This object is used to model the energy losses of
transformers when they are used to transfer electricity from
the grid to a building (as distribution transformers) or
transfer electricity from onsite generators to the grid.
Distribution transformers reduce the voltage on utility
distribution lines (34.5 kV or less) to a lower secondary
voltage (600 V or less) suitable for customer equipment.
According to the medium used for cooling and insulation,
distribution transformers can be classified into
liquid-immersed and dry type transformers. According to the
input voltages, distribution transformers can be classified
into medium-voltage (between 600 V and 34.5kV) and low-voltage
transformer (less than 600 V). The transformers used to output
the surplus electricity from onsite generators to the grid
usually match the cogeneration voltage to the grid. This
object can be used for all types of distribution transformers
and the transformers used to output electricity from onsite
generators to the grid, but the model defaults applies to the
low-voltage dry type transformers because they are the most
common type found in commercial and industrial facilities.
Energy losses in transformers consist of the no load (core)
loss and the load (winding) loss. The no load loss comes
primarily from the switching of the magnetic fields in the
core material. It is roughly constant and exists continuously
in the core material as long as the transformer is energized.
The load loss comes from the electrical resistance in the
windings when there is a load on the transformer. The load
loss is proportional to the load squared with a small
temperature correction. The energy losses at a given load
depend on the transformer’s performance. This object provides
the user two alternative ways to indicate the transformer’s
performance. First, the user can provide the no load loss and
load loss at rated conditions. Second, the user can provide
the nameplate efficiency and the corresponding reference
conditions. The detailed algorithms to calculate the energy
losses are described in the Engineering Reference.
The user needs to specify which loads are connected to the
transformer. This is achieved in different manners depending
on the transformer usage. For a distribution transformer, the
user needs to provide a number of electric meters wired to
that transformer. The input object can currently accommodate
up to ten meters, but it is extensible by modifying the
Energy+.idd entry. For a transformer used to output
electricity from onsite generators to the grid, the user needs
to indicate the transformer name in the served electric load
center.
This alpha field contains the schedule name (ref. Schedule
objects) that contains information on the availability of the
transformer. A schedule value greater than 0 (usually 1 is
used) indicates that the transformer is available to convert
AC power from one voltage to another. A value less than or
equal to 0 (usually 0 is used) denotes that the transformer is
not available. If this field is blank, the schedule has values
of 1 for all time periods.
This field indicates one of the two supported transformer
application types: PowerInFromGrid and
PowerOutFromOnsiteGeneration. The first type of transformer is
used to step down voltage from the electricity grid to a
building. The second type of transformer is used to match
voltage from building onsite generators to the electricity
grid.
This field contains the name of the thermal zone where the
transformer is located. Entering a valid name of zone here
will direct EnergyPlus to include the transformer’s losses as
heat gains to the named thermal zone. If the transformer is
not within a thermal zone, this field can be left blank and
the thermal energy associated with transformer losses is
removed from the building model.
This field contains the fraction of transformer’s losses
that enter the zone as long-wave thermal radiation. This
numeric filed should have a value between 0.0 and 1.0. The
balance of the losses is convective. This field is not used if
the previous field for zone name is left blank.
This field indicates whether the transformer is a single
phase or three phase type. The two alternative values are 1 or
3. The default is 3. This field is currently not used in the
model.
This field specifies the winding material used by the
transformer. There are two options: Copper and Aluminum. The
choice will determine the thermal coefficient of resistance
used to calculate the temperature correction factor for the
transformer load losses. The default is Aluminum.
This numeric field defines the temperature rise of the
windings above the ambient temperature, when the transformer
is loaded at its nameplate rating. For liquid-immersed
distribution transformers, the full load temperature rise
usually takes the value of 65 °C. For dry-type transformers,
the temperature rise usually takes three optional values: 80,
115 and 150 °C. This field accepts any value between the
minimum (50 °C) and the maximum (180 °C). The default is 150
°C.
This field defines the fraction of load losses resulting
from the eddy currents. Transformer’s load losses comprise two
parts: the ohmic loss due to the current flowing in the
resistance of the windings and the eddy and stray losses due
to the eddy currents. This field indicates the fraction of the
load losses due to the eddy currents. This numeric field
should have a value between 0.0 and 1.0. The default is
0.1.
This alpha field contains the method by which the user will
specify the transformer performance: “RatedLosses” or
“NominalEfficiency”. If this field is left blank in the input
data file, the default input method is assumed to be
“RatedLosses”. If the method “NominalEfficiency” is selected,
the user must enter the fields for the nameplate efficiency
and the corresponding reference coditions as described below.
If the method “RatedLosses” is selected, then the fields for
rated no load loss and load loss must be entered as described
below.
This field defines the no load loss (W) at rated load and
conditions. The no load loss is roughly constant and exists
whenever the transformer is energized. The no load loss is
also called the core loss. This field is used only if the
field of Performance Input Method is specified as
“RatedLosses”.
This field defines the load loss (W) at rated load and
conditions. The load loss varies with the square of the load
being served by the transformer. The load loss is also called
the winding loss because the load loss occurs in the primary
and secondary windings around the core. This field is used
only if the field of Performance Input Method is specified as
“RatedLosses”.
This field contains the value for transformer efficiency at
a given per unit load and specified reference temperature.
This field is used only if the field of Performance Input
Method is specified as “NominalEfficiency”. The default is
0.98.
Field:
Per Unit Load for Nameplate Efficiency[LINK]
This field defines the percentage of the rated capacity at
which the nameplate efficiency is measured. According to the
NEMA (National Electrical Manufactures Association) Standard
TP-1, the per unit load takes the value of 0.35 for dry-type
distribution transformers and it takes the value of 0.50 for
liquid-filled distribution transformers. The default is
0.35.
Field:
Reference Temperature for Nameplate Efficiency[LINK]
This field defines the conductor temperature at which the
nameplate efficiency is measured. This field is used only if
the field of Performance Input Method is specified as
“NominalEfficiency”. According to the NEMA Standard TP-1, the
reference temperature takes the value of 75 °C for dry-type
distribution transformers and it takes the value of 55 °C for
liquid-filled distribution transformers. The default is 75
°C.
This field defines the percentage of the rated capacity at
which the maximum efficiency is obtained. This field is used
only if the field of Performance Input Method is specified as
“NominalEfficiency”. A blank field indicates that it takes the
same value as the per unit load for nameplate efficiency.
Field:
Consider Transformer Loss for Utility Cost[LINK]
This field indicates whether the transformer losses are
considered to calculate utility cost. In some cases, the
transformer losses are required but they are not part of the
energy consumption for utility cost calculation. For example,
the transformer is owned by the utility company but it locates
in the building. In this case, it might be desired to model
transformer energy losses for HVAC operation but the energy
losses will not be accounted for utility cost.
A transformer may serve different loads such as plug loads,
some lighting loads, and some HVAC equipment loads. The user
needs to specify which loads are connected to the transformer.
This is achieved by providing a list of electric meters wired
to the transformer. The input object can currently accommodate
up to ten meters, but it is extensible by modifying the
Energy+.idd entry. Any valid electric meter name can be used
here to wire to the transformer loads. Many different meters
are automatically generated by the program and will depend on
the objects used throughout the input file. The typical
process of determining the exact name to enter in this field
involves doing an initial run of EnergyPlus and then examining
the *.mdd file which will list the meters and their resulting
names. A custom meter is also supported. The meter must have
electricity as its resource type.
ElectricLoadCenter:Transformer,
Transformer 1, !-Name
Always On, !- Availability Schedule Name
PowerInFromGrid, !- Transformer Usage
, !- Zone Name
, !- Radiative Fraction
15000, !- Nameplate Rating {VA}
3, !- Phase
Aluminum, !- Conductor Material
150, !- Full Load Temperature Rise {°C}
0.1, !- Fraction of Eddy Current Losses
NominalEfficiency, !- Performance Input Method
, !- Rated No Load Loss {W}
, !- Rated Load Loss {W}
0.985, !- Nameplate Efficiency
0.35, !- Per Unit Load for Nameplate Efficiency
75, !- Reference Temperature for Nameplate Efficiency {°C}
, !- Per Unit Load for Maximum Efficiency
Yes, !- Consider Transformer Loss for Utility Cost
Electricity:Building; !- Meter 1 Name
Schedule:Compact,
Always On, !- Name
Fraction, !- ScheduleType
Through: 12/31, !- Field #1
For: AllDays, !- Field #2
Until: 24:00, !- Field #3
1.0; !- Field #4
HVAC,Average,Transformer Efficiency[]
HVAC,Average,Transformer Output Electric Power[W]
HVAC,Sum,Transformer Output Elecric Energy [J]
HVAC,Average,Transformer Input Electric Power[W]
HVAC,Sum,Transformer Input Electric Energy [J]
HVAC,Average,Transformer No Load Loss Rate [W]
HVAC,Sum,Transformer No Load Loss Energy [J]
HVAC,Average,Transformer Load Loss Rate [W]
HVAC,Sum,Transformer Load Loss Energy [J]
HVAC,Average,Transformer Thermal Loss Rate [W]
HVAC,Sum,Transformer Thermal Loss Energy [J]
HVAC,Sum,Transformer Distribution Electric Loss Energy [J]
HVAC,Sum,Transformer Cogeneration Electric Loss Energy [J]
This output field is the efficiency at which the
distribution transformer changes alternating current from the
higher primary voltage to a lower secondary voltage. The
efficiency is calculated for each HVAC system timestep being
simulated, and the results are averaged for the timestep being
reported.
These outputs are the total electricity power or energy
provided by the transformer. They are equal to the metered
loads which are wired to the transformer. These values are
calculated for each HVAC system timestep being simulated, and
the results are averaged (for power) or summed (for energy)
for the timestep being reported.
These outputs are the total electricity power or energy fed
into the transformer. These values are calculated for each
HVAC system timestep being simulated, and the results are
averaged (for power) or summed (for energy) for the timestep
being reported.
These outputs are the no load loss occurred in the
transformer. These values are calculated for each HVAC system
timestep being simulated, and the results are averaged (for
rate) or summed (for energy) for the timestep being
reported.
These outputs are the load loss occurred in the
transformer. These values are calculated for each HVAC system
timestep being simulated, and the results are averaged (for
rate) or summed (for energy) for the timestep being
reported.
These outputs are the total energy losses occurred in the
transformer. They are equal to the sum of the no load loss and
the load loss. These values are calculated for each HVAC
system timestep being simulated, and the results are averaged
(for rate) or summed (for energy) for the timestep being
reported.
Transformer
Distribution Electric Loss Energy [J][LINK]
This output is the total energy losses occurred in the
transformer when it is used for input power from grid to
building. It is set as zero if the transformer is used to
transfer energy from onsite power generators to the
electricity grid. This output is also added to a meter with
ResourceType = Electricity, GroupKey = System.
Transformer
Cogeneration Electric Loss Energy [J][LINK]
This output is the total energy losses occurred in the
transformer when it is used for input onsite cogeneration to
the grid. It is set as zero if the transformer is used to
transfer the electricity grid to building. This output is also
added to a meter with ResourceType = ElectricityProduced,
EndUseKey = Cogeneration, GroupKey = System.
ElectricLoadCenter:Distribution
objects are used to include on-site electricity generators in
a simulation. The electric load center dispatches generators
according to operation schemes and tracks and reports the
amount of electricity generated and purchased. When using
on-site generators, the program provides a “net” report where
the total electricity used is reduced by the amount generated
on site. Electrical demand tracking is done by the internal or
custom meters used by EnergyPlus for reporting. The thermal
demand tracking uses internal load calculations from the plant
simulation. The dispatching of different generators is based
on expectations based on their nominal/rated electric power
output. If the current conditions are such that the generator
model determines that generation was higher or lower, then the
results of the dispatch may differ from expectations.
Multiple different ElectricLoadCenter:Distribution
objects can be included in an input file. A great deal of
flexibility is available by mixing different load centers and
operating schemes. If multiple load centers are used, the
supervisory control will dispatch generators sequentially
across the load centers. Therefore, the order of these input
objects in the IDF file becomes important with the generators
associated with first load center in the file being the first
to be managed. A certain amount of caution is needed to avoid
conflicting operating schemes.
The electricity produced from photovoltaic arrays will be
reported in the electricity produced output variable and will
reduce the demand that the generators will try to meet for
that timestep.
This alpha field specifies the type of operating scheme for
the generator set. The available operating schemes are
“Baseload,” “DemandLimit,” “TrackElectrical,” “TrackSchedule,”
“TrackMeter,” “FollowThermal,” and
“FollowThermalLimitElectrical.” The Baseload scheme operates
the generators at their rated (requested) electric power
output when the generator is scheduled ON (ref.
ElectricLoadCenter:Generators). The Baseload scheme requests
all generators scheduled ON (available) to operate, even if
the amount of electric power generated exceeds the total
facility electric power demand. The DemandLimit scheme limits
the amount of purchased electrical from the utility to the
amount specified in the input object. The DemandLimit scheme
tries to have the generators meet all of the demand above the
purchased electric limit set by the user in the next field.
The TrackElectrical scheme tries to have the generators meet
all of the electrical demand for the building. The
TrackSchedule scheme tries to have the generators meet all of
the electrical demand determined in a user-defined schedule.
The TrackMeter scheme tries to have the generators meet all
the electrical demand from a meter, which could also be a
user-defined custom meter.
The DemandLimit, TrackElectrical, TrackSchedule, and
TrackMeter schemes will sequentially load the available
generators. All demand not met by available generator capacity
will be met by purchased electrical. Therefore, if
DemandLimit, TrackElectrical, TrackSchedule, or TrackMeter is
utilized and the available generators are not enough to meet
demand, then purchased electrical will offset the difference.
If a generator is needed in the simulation for a small load
and it is less than the minimum part load ratio the generator
will operate at the minimum part load ratio and the excess
will either reduce demand or the excess energy will be
available for returning to the electric grid.
The FollowThermal and FollowThermalLimitElectrical schemes
are for heat following cogeneration and run the generators to
meet the thermal demand. The FollowThermal schemes allow
excess electrical generation to be exported to the grid, while
the FollowThermalLimitElectrical scheme restricts generator
output to a maximum of the building’s current electrical
demand (so that no electricity is exported). The thermal
demand is determined from the plant modeling and depends on
the flow requested by other components on the demand side of
the plant loop, the loop temperatures, and the loop
temperature set point. The electric load center converts the
thermal load to an electrical load using a nominal ratio of
the thermal to electrical power production for each generator.
For these schemes, the generator needs to be connected to the
supply side of a plant loop and components that request hot
water need to be on the demand side of the plant loop. This is
different than the usual configuration for electrical
following schemes where the generator is put on the demand
side and request flow for the purposes of cooling the
generator. Therefore a switch from one of the electrical-based
operating schemes to one of the thermal-based operating
schemes requires a substantial change in plant topology.
If the load center includes electrical storage, then the
choice of operating schemes will also affect how storage is
managed.
Field:
Demand Limit Scheme Purchased Electric Demand Limit[LINK]
This numerical field is the user input for the demand limit
above which the generators will try and meet the entire
electrical load on the building minus the photovoltaic array
if available.
Field:
Track Schedule Name Scheme Schedule Name[LINK]
This alpha field is the user input for the name of a
schedule defined elsewhere in the input file that contains
values for the “demand” loads placed on the generator(s). The
schedule values should be in Watts.
This alpha field is the user input for the name of a meter.
Any valid meter name can be used here to control the loads
that the generator(s) will try to meet. Many different meters
are automatically generated by the program and will depend on
the objects used throughout the input file. The typical
process of determining the exact name to enter in this field
involves doing an initial run of EnergyPlus and then examining
the *.rdd file which will list the meters and their resulting
names. The *.mtd file will also be useful to understand what
exactly is included in a meter. The user can also use the
Output:CustomMeter objects to redefine meter names and to
control what electrical loads are included on them in a
flexible manner.
This alpha field is used to describe how the electric load
center is configured with respect to any power conditioning
and/or storage equipment. There are five configurations for
load centers available by using one of these keywords:
AlternatingCurrent
AlternatingCurrentWithStorage
DirectCurrentWithInverter
DirectCurrentWithInverterDCStorage
DirectCurrentWithInverterACStorage
AlternatingCurrent is the default. All the generators
connected to a specific load center need to be of the same
type (all AC or all DC). If the generators are DC, then an
inverter is needed to convert the DC to AC. If there are DC
generators and a DC electrical storage device on the buss
along with an inverter, then use
DirectCurrentWithInverterDCStorage in this field. See the
Engineering Reference for more information including diagrams
of the load center configurations.
This field is used to identify the inverter connected to
this load center (if any). This field is only used if the
Electrical Buss Type is set to DirectCurrentWithInverter and
should contain the user-defined name of an inverter object.
There are three types of inverter models available–see ElectricLoadCenter:Inverter:Simple,ElectricLoadCenter:Inverter:LookUpTable,
or ElectricLoadCenter:Inverter:FunctionOfPower.
Enter the name of one of these types of inverter objects
defined elsewhere in the input file.
This field is used to identify the electrical storage
connected to this load center (if any). This field is only
used if the Electrical Buss Type is set to
DirectCurrentWithInverterDCStorage or
DirectCurrentWithInverterACStorage. Enter the name of an ElectricLoadCenter:Storage:Simple
object defined elsewhere in the input file.
This field is used to identify the transformer connected to
this load center (if any). This field can be used for any
electrical buss types. Enter the name of an ElectricLoadCenter:Transformer
object defined elsewhere in the input file.
Examples of this object are:
ElectricLoadCenter:Distribution,
SOFC Electric Load Center, !- Name
Micro-Generators, !- Generator List Name
Baseload, !- Generator Operation Scheme Type
0.0, !- Demand Limit Scheme Purchased Electric Demand Limit {W}
, !- Track Schedule Name Scheme Schedule Name
, !- Track Meter Scheme Meter Name
AlternatingCurrent, !- Electrical Buss Type
, !- Inverter Object Name
; !- Electrical Storage Object Name
ElectricLoadCenter:Distribution,
Electric Load Center, !- Name
Backup Generators, !- Generator List Name
DemandLimit, !- Generator Operation Scheme Type
10000.0, !- Demand Limit Scheme Purchased Electric Demand Limit {W}
, !- Track Schedule Name Scheme Schedule Name
, !- Track Meter Scheme Meter Name
AlternatingCurrent, !- Electrical Buss Type
, !- Inverter Object Name
; !- Electrical Storage Object Name
There are three levels of results reporting related to
electric load centers and generators. The top level of
reporting provides results across the whole building and all
the different electric load centers and generators. The second
level of reporting provides results for individual load
centers. The third level is for each type of generator (see
individual generator descriptions). This section discusses the
first two levels.
The whole-building summary output variables are:
HVAC,Average,Facility Total Produced Electric Power [W]
HVAC,Sum,Facility Total Produced Electric Energy [J]
HVAC,Average,Facility Total Purchased Electric Power [W]
HVAC,Sum,Facility Total Purchased Electric Energy [J]
HVAC,Average,Facility Total Building Electric Demand Power [W]
HVAC,Average,Facility Total HVAC Electric Demand Power [W]
HVAC,Average,Facility Total Electric Demand Power [W]
These output variables all use a default keyword “Whole Building.”
These output variables can also be accessed without
specifying generation equipment by including the syntax shown
below:
ElectricLoadCenter:Distribution,
Electric Load Center; !- Name
Even if no ElectricLoadCenter:Distribution
object is included, these output variables are also available
for all simulations that have any electricity consuming
equipment with the default keyword name “Electrical
Service.”
These outputs are the total generator and photovoltaic
electricity produced on-site for the entire model, and they
are in both Power and Energy units. When electrical storage is
used with on-site production, the electricity put into storage
is decremented from production and the electricity removed
storage is added to production. This means that losses from a
round trip through electrical storage decrease on-site
electricity production.
Facility
Total Purchased Electric Energy [J][LINK]
These outputs are the total of electricity purchased for
the entire model in both Power and Energy units. This value is
always positive and indicates the amount of energy is
purchased from the utility.
This output is the excess electricity produced and sent out
to the electrical grid. This value is always positive and
indicates the surplus electricity from generation that exceeds
whole-building demand and fed into the grid.
Facility
Total Building Electric Demand Power [W][LINK]
This output variable includes all of the electric demand
from the building (non-HVAC) portion of the simulation, which
would contain lights, electrical equipment, exterior lights
and equipment, etc.
Facility
Total HVAC Electric Demand Power [W][LINK]
This output variable includes all of the electric demand
from the HVAC portion of the simulation, which would contain
fans, electric coils, pumps, chillers, cooling towers,
etc.
These outputs are the net electricity purchased in both
Power and Energy units. This value can be either positive or
negative. Positive values are defined as electricity purchased
from the utility. Negative values are defined as surplus
electricity fed back into the grid.
Each ElectricLoadCenter also collects results from the
individual generators that are connected to that load center.
The output variables available at the ElectricLoadCenter level
are:
HVAC,Average,Electric Load Center Requested Electric Power [W]
HVAC,Average,Electric Load Center Produced Electric Power [W]
HVAC,Sum,Electric Load Center Produced Electric Energy [J]
HVAC,Average,Electric Load Center Produced Thermal Rate [W]
HVAC,Sum,Electric Load Center Produced Thermal Energy [J]
Electric
Load Center Requested Electric Power [W][LINK]
This output variable is the average electric power supply
(in watts) requested by the load center from its generators
for the time step being reported. For the baseload operating
scheme, this output variable should equal the sum of the power
supply requests for the ‘available’ generators associated with
this load center (ref. ElectricLoadCenter:Generators). In
other cases, this output could be different from the sum of
the power supply requests for the generators associated with
this load center. For example, a generator might be requested
to provide a certain amount of power but can only provide a
fraction of the requested amount. In this case the load center
will detect this shortfall and include it when calculating the
power request for the next available generator. Therefore, the
sum of the power supply requests for the individual generators
associated with this load center (ref.
ElectricLoadCenter:Generators) could be greater than the
Electric Load Center Requested Electric Power output
variable.
Electric
Load Center Produced Electric Power [W][LINK]
Electric
Load Center Produced Electric Energy [J][LINK]
These outputs are the sum of electrical energy and power
produced by the generators attached to a particular load
center. The keywords for these reports are the unique names of
ElectricLoadCenter:Distribution
objects.
Electric
Load Center Produced Thermal Rate [W][LINK]
Electric
Load Center Produced Thermal Energy [J][LINK]
These outputs are the sum of the thermal energy and power
produced by the generators attached to a particular load
center. The keywords for these reports are the unique names of
ElectricLoadCenter:Distribution
objects.
The ElectricLoadCenter:Generators
object is used to provide a list of the generators to include
in the simulation. The list includes the names and types of
all the generators along with separate availability schedules,
the rated power output, and thermal-to-electrical power ratio
for each. Sets of five input fields are repeated for each
generator. If more than 30 generators are needed, EnergyPlus
will “auto-extend” to suit the needs but other interfaces
(such as the IDF Editor may not). The user can always modify
the Energy+.idd file to accommodate the extra fields
necessary, but it is likely the next release of EnergyPlus
will overwrite any user modifications.
This alpha field contains the identifying name for the
generators in the set.
FieldSet:
Name, Object Type, Rated Power Output, Availability, Thermal
Ratio up to 30[LINK]
Each generator is specified by a set of 5 input fields that
contain an identifying name, a keyword that indicates the type
of generator, the rated output of the generator, the
availability schedule of the generator, and the thermal to
electrical power production ratio.
This alpha field contains the keyword for the type of
generator. The available types include:
Generator:InternalCombustionEngine
Generator:CombustionTurbine
Generator:Photovoltaic
Generator:FuelCell
Generator:MicroCHP
Generator:MicroTurbine
Generator:WindTurbine
These keywords are the names of the input objects for the
type of generator.
Field:
Generator Rated Electric Power Output[LINK]
This numeric field contains the nominal electric power
output to be requested from generator 1. It is normally equal
to the rated power output of the generator in Watts. This
value is used only for supervisory control and generator
dispatch; the actual power output for each time step is
determined by the generator models. This value affects how
much a generator is loaded (i.e., requested electric power
output) and can also impact the operation of an electric
storage unit (e.g., LoadCenter:Storage:Simple) if one is
connected to the associated load distribution center (ref.
ElectricLoadCenter:Distribution). Refer to Electrical Storage
in the EnergyPlus Engineering Reference for more details
regarding this input field and its relationship with electric
storage.
This alpha field is used as an identifying field for the
generator availability schedule. If not blank, this field must
contain the name of a schedule defined elsewhere in the input
file. A schedule value of <=0.0 indicates the generator is
not available, while a schedule value > 0.0 indicates that
the generator is available to operate. If this field is blank,
the schedule has values of 1 for all time periods.
Field:
Generator Rated Thermal to Electrical Power Ratio[LINK]
This numeric field contains the ratio of the rated thermal
output to the rated electric output. It is only needed and
used if the operation scheme is set to
FollowThermal or
FollowThermalLimitElectrical. This nominal
ratio is only used for control and dispatch decisions. This
value should be generally consistent with the more detailed
performance input for the individual generator component
models but it is not used in those component models.
An example IDF showing how this object is used is provided
below:
ElectricLoadCenter:Generators,
Backup Generators, !- Name
Cat Diesel, !- Generator 1 Name
Generator:InternalCombustionEngine, !- Generator 1 Object Type
50000, !- Generator 1 Rated Electric Power Output
ON PEAK GENERATOR SCHEDULE, !- Generator 1 Availability Schedule Name
, !- Generator 1 Rated Thermal to Electrical Power Ratio
Solar Turbine, !- Generator 2 Name
Generator:CombustionTurbine, !- Generator 2 Object Type
30000, !- Generator 2 Rated Electric Power Output
OFF PEAK GENERATOR SCHEDULE, !- Generator 2 Availability Schedule Name
, !- Generator 2 Rated Thermal to Electrical Power Ratio
Capstone C65, !- Generator 3 Name
Generator:Microturbine, !- Generator 3 Object Type
65000, !- Generator 3 Rated Electric Power Output
MID PEAK GENERATOR SCHEDULE, !- Generator 3 Availability Schedule Name
; !- Generator 3 Rated Thermal to Electrical Power Ratio
This output variable represents the average electric power
supply in Watts that is being requested from a specific
generator for the time step being reported. In some instances
the output value may be the Rated Electric Power Output
specified for the generator in the ElectricLoadCenter:Generators
object. If the generator is not available for a simulation
time step (as indicated by its availability schedule), then
the power supply request will be zero. The power supply
request may be less than the rated electric power output if
the overall electric power reduction target has already been
met, partially or completely, by electric power produced by
other generators. If an EnergyPlus Energy Management System is
used to specify an electric power supply request for this
generator, then that EMS request will be reflected in this
output variable.
This input object is used to model conversion from Direct
Current (DC) to Alternating Current (AC) in an electric load
center that contains photovoltaic modules. Such a load center
has an array of photovoltaic modules that feed an inverter DC
power and the inverter produces AC power. This input object is
for the simplest inverter model and uses a fixed efficiency.
There are two other types of inverters with more complex
models described below.
This field contains a unique name for the inverter. The
name entered must also be unique across all other types of
inverters that may also be in the input file.
This field contains the name of a schedule that describes
when the inverter is available. If the inverter is scheduled
to not be available, by scheduling a value of 0, then it
cannot produce AC power and will not consume ancillary power
during standby. Any non-zero schedule value means the inverter
is available to produce AC power and consume ancillary power
during standby. If the Inverter is scheduled to be unavailable
but it is being supplied with DC power anyway, then the energy
is dissipated as heat. If this field is blank, the schedule
has values of 1 for all time periods.
This field contains the name of the thermal zone where the
inverter is located. Entering a valid name of zone here will
direct EnergyPlus to include the inverter’s losses as heat
gains to the named thermal zone. If the inverter is not within
a thermal zone, then this field can be left blank (and the
thermal energy associated with inverter losses is removed from
the building model).
This field contains the fraction of inverter thermal losses
that enter the zone as long-wave thermal radiation. This
should be a factor between 0.0 and 1.0. The balance of the
losses is convective. This field is not used if the previous
field for zone name is left blank.
This field contains the value for inverter efficiency. In
the simple model, efficiency is a constant. This is the
so-called 1-term model. Input data for different types of
inverters is available at
http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries
where the “CEC Efficiency” would be the value to enter
here.
An example IDF showing how this object is used is provided
below:
ElectricLoadCenter:Inverter:Simple,
Simple Ideal Inverter, !- Name
Always On, !- Availability Schedule Name
, !- Zone Name
0.0, !- Radiative Fraction
1.0; !- Inverter Efficiency
This input object is used to model conversion from Direct
Current (DC) to Alternating Current (AC) in an electric load
center that contains photovoltaic modules. Such a load center
has an array of photovoltaic modules that feed an inverter DC
power and the inverter produces AC power. This input object is
for an inverter model where efficiency is a function of
normalized power.
This field contains a unique name for the inverter. The
name entered must also be unique across all other types of
inverters that may also be in the input file.
This field contains the name of a schedule that describes
when the inverter is available. If the inverter is scheduled
to not be available, by scheduling a value of 0, then it
cannot produce AC power, nor contribute heat gains to the
zone, and will not consume ancillary power during standby. Any
non-zero schedule value means the inverter is available to
produce AC power, contribute heat gains to the zone and
consume ancillary power during standby. If this field is
blank, the schedule has values of 1 for all time periods.
This field contains the name of the thermal zone where the
inverter is located. Entering a valid name of zone here will
direct EnergyPlus to include the inverter’s losses as heat
gains to the named thermal zone. If the inverter is not within
a thermal zone, then this field can be left blank (and the
thermal energy associated with inverter losses is removed from
the building model).
This field contains the fraction of inverter thermal losses
that enter the zone as long-wave thermal radiation. This
should be a factor between 0.0 and 1.0. The balance of the
losses is convective. This field is not used if the previous
field for zone name is left blank.
Field:
Efficiency Function of Power Curve Name[LINK]
This field contains the name of curve representing the
relationship between DC power input into the inverter and the
efficiency with which that power is converted to AC. The curve
can be either a Curve:Linear,Curve:Quadratic,
or Curve:Cubic.
The curve’s “x” value is DC power input normalized by the
following field. The result of the curve should be power
conversion efficiency expressed as a fraction between 0.0 and
1.0.
This field contains the rated power input in watts. This is
value used to normalize input power for use with the curve
named in the previous field. This is DC power from the PV
arrays going into the inverter.
This field contains a lower limit on the AC power produced
by the inverter. If the resulting power output would be below
this level, then the inverter is assumed to not produce any
power and is in stand by mode. All DC power input is lost
(unless it is going into storage).
This field contains an upper limit on the AC power produced
by the inverter. If the resulting power output would be above
this level, then the power produced is capped at this level
with the rest of input power converted to losses (unless it is
going into storage).
This field contains the ancillary power in watts used by
the inverter when not producing AC power. This is AC
electricity consumed in standby mode. Standby mode occurs when
the inverter is scheduled to be available but the incoming DC
power is too low.
An example IDF showing how this object is used is provided
below:
ElectricLoadCenter:Inverter:FunctionOfPower,
Curve Inverter, !- Name
ALWAYS_ON, !- Availability Schedule Name
, !- Zone Name
0.3, !- Radiative Fraction
Inverter Curve, !- Efficiency Function of Power Curve Name
15000, !- Rated Maximum Continuous Input Power {W}
0.0, !- Minimum Efficiency
1.0, !- Maximum Efficiency
200, !- Minimum Power Output {W}
20000, !- Maximum Power Output {W}
0.0; !- Ancillary Power Consumed In Standby {W}
This input object is used to model conversion from Direct
Current (DC) to Alternating Current (AC) in an electric load
center that contains photovoltaic modules. Such a load center
has an array of photovoltaic modules that feed an inverter DC
power and the inverter produces AC power. This input object is
for an inverter model where efficiency is interpolated using a
look up table.
This object was designed for use with data contained in the
Inverter Performance Test Summaries available at
http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries.
All of the data needed for this object can be found there by
make and model of inverter. The core of the data set is a 3x6
matrix of efficiency at different voltage and power levels.
These form the look up table used in the model. Note that
EnergyPlus’ PV models currently model only power and not the
voltage and current situation. Therefore, only the nominal
voltage data are used. This is the middle row of data in the
Go Solar summaries.
This field contains a unique name for the inverter. The
name entered must also be unique across all other types of
inverters that may also be in the input file.
This field contains the name of a schedule that describes
when the inverter is available. If the inverter is scheduled
to not be available, by setting a value of 0, then it cannot
produce AC power, nor contribute heat gains to the zone, and
will not consume ancillary power during standby. Any non-zero
schedule value means the inverter is available to produce AC
power, contribute heat gains to the zone and consume ancillary
power during standby. If this field is blank, the schedule has
values of 1 for all time periods.
This field contains the name of the thermal zone where the
inverter is located. Entering a valid name of zone here will
direct EnergyPlus to include the inverter’s losses as heat
gains to the named thermal zone. If the inverter is not within
a thermal zone, then this field can be left blank (and the
thermal energy associated with inverter losses is removed from
the building model).
This field contains the fraction of inverter thermal losses
that enter the zone as long-wave thermal radiation. This
should be a factor between 0.0 and 1.0. The balance of the
losses is convective. This field is not used if the previous
field for zone name is left blank.
Field:
Rated Maximum Continuous Output Power[LINK]
This field contains the rated maximum continuous output
power in watts.
This field contains the nominal DC input voltage in volts.
This is “Vnom” in the Go Solar test summaries.
Field:
Efficiency at 10% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 10% power.
Field:
Efficiency at 20% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 20% power.
Field:
Efficiency at 30% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 30% power.
Field:
Efficiency at 50% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 50% power.
Field:
Efficiency at 75% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 75% power.
Field:
Efficiency at 100% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal
voltage and 100% power.
An example IDF showing how this object is used is provided
below:
ElectricLoadCenter:Inverter:LookUpTable,
PV Inverter, !- Name
ALWAYS_ON, !- Availability Schedule Name
, !- Zone Name
0.25, !- Radiative Fraction
14000, !- Rated Maximum Continuous Output Power {W}
200.0, !- Night Tare Loss Power {W}
368, !- Nominal Voltage Input {V}
0.839, !- Efficiency at 10% Power and Nominal Voltage
0.897, !- Efficiency at 20% Power and Nominal Voltage
0.916, !- Efficiency at 30% Power and Nominal Voltage
0.931, !- Efficiency at 50% Power and Nominal Voltage
0.934, !- Efficiency at 75% Power and Nominal Voltage
0.930; !- Efficiency at 100% Power and Nominal Voltage
Each inverter can report the following seven output
variables.
HVAC,Average,Inverter DC to AC Efficiency [ ]
HVAC,Average,Inverter DC Input Elecric Power [W]
HVAC,Sum,Inverter DC Input Electric Energy [J]
HVAC,Average,Inverter AC Output Electric Power [W]
HVAC,Sum,Inverter AC Output Electric Energy [J]
HVAC,Average,Inverter Thermal Loss Rate [W]
HVAC,Sum,Inverter Thermal Loss Energy [J]
HVAC,Sum,Inverter Ancillary AC Electric Energy [J]
HVAC,Average,Inverter Ancillary AC Electric Power [W]
These outputs are total electricity power or energy fed
into the inverter. This is Direct Current from photovoltaics
(or DC-based electrical storage) going into the inverter.
These outputs are the Alternating Current electricity
consumed by the inverter. These are ancillary, or night tare
loss, power uses by the inverter and modeled as if powered by
the building’s grid connection. These ancillary power draws
generally occur when the inverter is not generating power but
waiting in a standby mode ready to begin generating power.
This input object is used to model storage of electricity
in an electric load center. This is a simple model that does
not attempt to represent any of the characteristics of a real
storage device such as a battery. The type of power, AC or DC,
depends on the configuration chosen as the Electrical Buss
Type in the ElectricLoadCenter:Distribution
object.
This field contains the name of a schedule that describes
when the storage device is available. If storage is not
available, by scheduling a value of 0, then no electrical
energy can be stored or drawn from the device. Any non-zero
schedule value means the devices is available. If this field
is blank, the schedule has values of 1 for all time
periods.
This field contains the name of the thermal zone where the
storage device is located. Entering a valid name of a zone
here will direct EnergyPlus to include the storage losses as
heat gains to the name thermal zone. If the storage is not
within a therma zone, then this field can be left blank.
Field:
Radiative Fraction for Zone Heat Gains[LINK]
This field contains the fraction of storage losses that
enter the zone as long-wave thermal radiation. This should be
a factor between 0.0 and 1.0. The balance of the losses are
convective. This field is not used if the previous field for
zone name is left blank.
Field:
Nominal Energetic Efficiency for Charging[LINK]
This field contains the charging efficiency. This is the
energetic efficiency of storing electrical energy in the
storage device. A value of 1.0 means the device does not lose
any energy when charging.
This field contains the discharging efficiency. This is the
energetic efficiency of drawing electrical energy from the
storage device. A value of 1.0 means the device does not lose
any energy when drawing power.
This field describes the maximum amount of energy that can
be stored in the device in Joules. Once the storage device is
full, no additional energy can be stored in it.
This field describes the value for the initial state of
charge in Joules. This is used to model the storage device as
having some amount of stored energy at the beginning of the
simulation period.
An example IDF showing how this object is used is provided
below:
ElectricLoadCenter:Storage:Simple,
Battery, !- Name
ALWAYS_ON, !- Availability Schedule Name
, !- Zone Name
0.0, !- Radiative Fraction for Zone Heat Gains
0.7, !- Nominal Energetic Efficiency for Charging
0.7, !- Nominal Discharging Energetic Efficiency
1.0E11, !- Maximum Storage Capacity {J}
50000, !- Maximum Power for Discharging {W}
25000, !- Maximum Power for Charging {W}
1.0E10; !- Initial State of Charge {J}
Each electrical storage device can report the following
seven output variables.
HVAC,Average,Electric Storage Charge State [J]
HVAC,Average,Electric Storage Charge Power [W]
HVAC,Sum,Electric Storage Charge Energy [J]
HVAC,Average,Electric Storage Discharge Power [W]
HVAC,Sum,Electric Storage Discharge Energy [J]
HVAC,Average,Electric Storage Thermal Loss Rate [W]
HVAC,Sum,Electric Storage Thermal Loss Energy [J]
HVAC,Sum,Electric Storage Production Decrement Energy [J]
This output is the state of charge of the storage device.
State of charge is the amount of electrical energy stored in
the device at a point of time. The amount of energy stored in
tracked in Joules.
These outputs are total electricity power or energy fed
into the storage device. This is the rate or amount of
charging.
Electric
Storage Production Decrement Energy [J][LINK]
This output is the total electricity energy decremented
from electricity production because it has fed into the
storage device. This output has the opposite sign of “Electric
Storage Charge Energy” but is otherwise similar. This
decrement output variable is also a meter associated with the
resource type “ElectricityProduced” that reduces the metered
electricity production to account for power that went into
storage after production.
These outputs are total electricity power or energy drawn
from the storage device. This is the rate or amount of
discharging. The energy from storage output variable is also a
meter associated with the resource type “ElectricityProduced”
that increases the metered electricity production to account
for power that has come back out of storage.
These outputs are the thermal power or energy losses from
both charging and drawing electrical power in or out of the
storage device. These losses are the result of inefficiencies
in charging and drawing.
This object uses the kinetic battery model (KiBaM) to
simulate rechargeable battery banks in an electrical load
center. The battery bank is a collection of one or more
individual battery modules. Given the surplus or deficit power
from the electrical system and the state of charge from the
previous time step, this object can model the voltage,
current, and energy losses with charging and discharging
during each time step. The cumulative battery damage can be
also modeled and reported at the end of each simulation
run.
This object allows the simulation of both lead-acid and
Nickel Cadmium batteries. With input parameters derived from
specific battery tests, the object is expected to support
other battery types such as Lithium-ion batteries.
The kinetic battery model assumes that part of the
battery’s energy storage capacity is immediately available in
discharging or charging while the rest is chemically bound. As
a function of constant current, the battery capacity is
related to three parameters: the maximum capacity at
infinitesimal current, the capacity ratio of available
charges, and the conversion ratio between available charges
and bound charges. These parameters are usually obtained via
curve fitting based on battery data sheets or test data.
Each individual battery module is modeled as a voltage
source in series with an electrical resistance. KiBaM assumes
that the internal resistance is constant and the open circuit
voltage varies with the electric current, the state of charge
and the operation mode (charging or discharging). For an
individual battery module, the open circuit voltage at any
time is correlated to the voltage at fully charged/discharged
state and three other regression coefficients. These
regression coefficients are usually obtained via curve fitting
based on battery test data.
The object offers user the option to perform battery life
calculation. If battery life is modeled, the user needs to
provide a group of coefficients for the correlation between
the number of cycles for battery failure and the corresponding
cycle range. More detailed information can be found from the
Engineering Reference.
This alpha field contains the schedule name (ref. Schedule
objects) that describes when the battery is available. A
schedule value greater than 0 (usually 1 is used) indicates
that electrical energy can be stored or drawn from the
battery. A value less than or equal to 0 (usually 0 is used)
denotes that the battery is not available. If this field is
blank, the schedule has values of 1 for all time periods.
This field contains the name of the thermal zone where the
battery is located. Entering a valid name of zone here will
direct EnergyPlus to include the energy storage losses as heat
gains to the named thermal zone. If the battery is not within
a thermal zone, this field can be left blank and the thermal
energy associated with storage losses is removed from the
building model.
This field contains the fraction of storage losses that
enter the zone as long-wave thermal radiation. This numeric
filed should have a value between 0.0 and 1.0. The balance of
the losses is convective. This field is not used if the
previous field for zone name is left blank.
Field:
Number of Battery Modules in Parallel[LINK]
This field defines the number of modules connected in
parallel in the battery bank.
This field defines the number of modules connected in
series in the battery bank. The total number of modules in a
battery bank is equal to the number of modules in parallel
times the number of modules in series.
This field indicates the maximum capacity of one battery
module. It is evaluated as the total Amp-hours available when
a full battery is discharged at infinitesimal current. This
capacity is for an individual battery module, not for the
whole battery bank. The maximum capacity can be found from
manufacture’s data or derived from test data by curve
fitting.
This field describes the initial state of charge in terms
of the fraction of maximum capacity as defined in the previous
field.
Field:
Fraction of Available Charge Capacity[LINK]
The kinetic battery model assumes that battery is a
two-tank electrical energy storage device: an available tank
and a bound tank. The available tank can be immediately
charged or discharged, while the bound tank can only be
charged or discharged via the available tank. This field
specifies the fraction of total charge in the battery that is
part of the available tank. The ratio of available charge
capacity to total capacity is a parameter usually derived from
test data by curve fitting.
Field:
Change Rate from Bound Charge to Available Charge[LINK]
This field specifies the rate at which the charge flows
between the available tank and the bound tank. It is a
parameter used to calculate the conversion between available
charge and chemically bound charge when charging and
discharging the battery. This parameter is usually derived
from test data by curve fitting.
Field:
Fully Charged Module Open Circuit Voltage[LINK]
This field indicates the open circuit voltage for a fully
charged battery module. It can be found from manufacture’s
data or battery tests.
Field:
Fully Discharged Module Open Circuit Voltage[LINK]
This field indicates the open circuit voltage for a fully
discharged battery module. It can be found from manufacture’s
data or battery tests.
Field:
Voltage Change Curve Name for Charging[LINK]
This field specifies the name of a rectangular hyperbola
type 2 performance curve (ref: Curve:RectangularHyperbola2
in Performance Curves) that determines the change of open
circuit voltage (\(\Delta
E\)) as a function of the battery state of charge in
charging. The change of open circuit voltage is relative to a
fully discharged battery.
The curve has the following form:
\[\Delta E = ({C_1}*X)/({C_2} +
X) + {C_3}*X\]
where X is the battery charge divided by the maximum
capacity at a given current. More details can be found from
the Engineering Reference.
Field:
Voltage Change Curve Name for Discharging[LINK]
This field specifies the name of a rectangular hyperbola
type 2 performance curve (ref: Curve:RectangularHyperbola2
in Performance Curves) that determines the change of open
circuit voltage (\(\Delta
E\)) as a function of the battery state of charge in
discharging. The change of open circuit voltage is relative to
a fully charged battery.
The curve has the following form:
\[\Delta E = ({C_1}*X)/({C_2} +
X) + {C_3}*X\]
where X is the removed charge divided by the maximum
capacity at a given current. More details can be found from
the Engineering Reference.
This field specifies the battery internal resistance in
ohms. In theory, the electrical resistance within the battery
varies with the state of charge and depends on whether it is
in charging or discharging. In the kinetic battery model, the
internal resistance is assumed as constant and the terminal
voltage varies with current and state of charge. The internal
resistance may be obtained from the battery manufacture or
battery test data. Note that the field is for an individual
module, not for the whole battery bank.
This field indicates the maximum current at which the
battery can be discharged continuously. The limit on discharge
current is usually defined by the battery manufacture to avoid
battery damage. The limit is for an individual battery
module.
This field specifies the minimum allowable voltage, below
which the battery is generally regarded as empty. The cut-off
voltage is usually defined by the battery manufacture and it
is for an individual battery module.
This field specifies the limit on charging current relative
to the remaining charge until the battery is full. This limit
reflects the common practice that the charge rate is reduced
as the battery gets more charged.
This field indicates whether the battery life model is
activated in the simulation. If the battery life model is
activated, the following five inputs on curve coefficients are
required; otherwise, they are not used.
This field specifies the number of equally ranged cycle
bins in battery life simulation. If 10 bins are used, the
cycle ranges will include 10%, 20%, …, 100%.
This field specifies the name of a double exponential decay
curve (ref: Curve:DoubleExponentialDecay
in Performance Curves) that correlates the cycles of battery
failure (CF) and fractional depth of discharge (R).
The curve is:
An example input of the ElectricLoadCenter:Storage: Battery
input is:
ElectricLoadCenter:Storage:Battery,
Lead Acid Battery A, !-Name
Always On, !- Availability Schedule Name
, !- Zone Name
, !- Radiative Fraction
1, !- Number of Battery Modules in Parallel
1, !- Number of Battery Modules in Series
86.1, !- Maximum Module Capacity {Ah}
1.0, !- Initial Fractional State of Charge
0.3747, !- Fraction of Available Charge Capacity
0.5874, !- Change Rate from Bound Charge to Available Charge {hr^-1^}
12.60, !- Fully Charged Module Open Circuit Voltage {V}
12.37, !- Fully Discharged Module Open Circuit Voltage {V}
BatteryChargeCurve, !- Voltage Change Curve Name for Charging
BatteryDischargeCurve,!- Voltage Change Curve Name for Discharging
0.0538, !- Module Internal Electrical Resistance {Ohm}
100, !- Maximum Module Discharging Current {A}
10.2, !- Module Cut-off Voltage {V}
1, !- Module Charge Rate Limit {1/hr}
Yes, !- Battery Life Calculation
10, !- Number of Cycle Bins
BatteryCycleCurve; !- Battery Cycle Life Curve Name
Curve:RectangularHyperbola2,
BatteryChargeCurve, !- Name
-0.2765, !- Coefficient1 C1
-93.27, !- Coefficient2 C2
0.0068, !- Coefficient3 C3
0, !- Minimum Value of x
1.0, !- Maximum Value of x
-100, !- Minimum Curve Output
100; !- Maximum Curve Output
Curve:RectangularHyperbola2,
BatteryDischargeCurve, !- Name
0.0899, !- Coefficient1 C1
-98.24, !- Coefficient2 C2
-0.0082, !- Coefficient3 C3
0, !- Minimum Value of x
1.0, !- Maximum Value of x
-100, !- Minimum Curve Output
100; !- Maximum Curve Output
Curve:DoubleExponentialDecay,
BatteryCycleCurve, !- Name
1380, !- Coefficient1 C1
6834, !- Coefficient2 C2
-8.75, !- Coefficient3 C3
6747, !- Coefficient4 C4
-6.22, !- Coefficient5 C5
0, !- Minimum Value of x
1.0; !- Maximum Value of x
HVAC,Average, Electric Storage Operating Mode Index []
HVAC,Average,Electric Storage Charge State[Ah]
HVAC,Average, Electric Storage Charge Fraction []
HVAC,Average,Electric Storage Charge Power[W]
HVAC,Sum,Electric Storage Charge Energy [J]
HVAC,Average,Electric Storage Discharge Power[W]
HVAC,Sum,Electric Storage Discharge Energy [J]
HVAC,Average,Electric Storage Total Current[A]
HVAC,Average, Electric Storage Total Voltage [V]
HVAC,Average,Electric Storage Thermal Loss Rate [W]
HVAC,Average, Electric Storage Degradation Fraction []
HVAC,Sum,Electric Storage Production Decrement Energy [J]
HVAC,Sum,Electric Storage Thermal Loss Energy [J]
This output reports the battery mode of operation: 0 for
idle; 1 for discharging; 2 for charging. It is expected that
more operation modes would be added when a smart and active
power dispatch controller is used in future.
The state of charge is expressed as the amount of charge
stored in the battery at a point of time. It has the same unit
as the maximum capacity. This value is given for an individual
battery module
These outputs are total electricity power or energy fed
into the battery. This is the rate of amount of charging.
Electric
Storage Production Decrement Energy [J][LINK]
This output is the total electricity energy decremented
from electricity production because it has fed into the
battery. This output has the opposite sign of “Electric
Storage Charge Energy” but is otherwise similar. This
decrement output variable is also a meter associated with the
resource type “ElectricityProduced” that reduces the metered
electricity production to account for power that went into
storage after production.
These outputs are total electricity power or energy drawn
from the battery. This is the rate or amount of discharging.
The energy from storage output variable is also a meter
associated with the resource type “ElectricityProduced” that
increases the metered electricity production to account for
power that has come back out of storage.
This output is the current to or from the battery bank
depending on whether the battery is in the state of charging
or discharging. The value is positive for discharging and
negative for charging.
These outputs are the thermal power or energy losses from
both charging and drawing electrical power in or out of the
storage device. These losses are due to the battery internal
resistance in charging and discharging.
This output reports the fractional battery life used up at
a point of time. For example, a value of 0.4 at the end of one
year simulation means that the 40% of the battery life is used
up, so the battery needs to be replaced every two and a half
years.
The Internal Combustion (IC) Engine generator uses a
modified Otto cycle. This generator model uses the electrical
load and rated engine generator size to compute part-load
ratios (PLR). Fuel energy input and recoverable jacket and
lube oil heat are then computed. Finally, the recoverable
exhaust heat is calculated.
Manufacturer’s curves or tables must be obtained for IC
engine generators to derive the equipment performance
parameters that are specified in the quadratic curve fits.
Note that simple transformation of the form of the
manufacturer’s curves may be required. Electric energy
output/fuel energy input is related to the part-load ratio
(i.e., electric/load generator capacity) with a polynomial.
Recoverable jacket heat/fuel energy equipment, recoverable
lube oil heat/fuel energy input equipment performance, total
exhaust heat/fuel energy input equipment, exhaust gas
temperature/fuel energy input equipment performance parameters
are all specified with a quadratic curve fit.
When the heat recovery curve fits = 0.0, this means that no
heat recovery is done on the IC engine generator exhaust gas;
and no heat recovery is specified.
This alpha field contains the optimal operating fraction of
full load. This is the part load ratio that gives the optimal
production of electric power with the least amount of fuel
usage.
This alpha field contains the name of the shaft power
curve. The curve itself is specified separately using a curve
object (ref: Curve:QuadLinear). The Shaft Power Curve is a
quadratic equation that determines the electric output versus
the fuel used. Used to calculate the electric energy output
divided by the fuel energy consumption as a function of
part-load ratio. The defining equation is:
This alpha field contains the name of the Recovery Jacket
Heat curve. The curve itself is specified separately using a
curve object (ref: Curve:QuadLinear). The Jacket Heat Recovery
Curve is a quadratic equation that determines the ratio of
recovery jacket heat to fuel energy. Used to calculate the
recoverable jacket heat as a function of part-load ratio.
This alpha field contains the name of the Recovery Lube
Heat curve. The curve itself is specified separately using a
curve object (ref Curve:QuadLinear). The Lube Heat Recovery
Curve is a quadratic equation that determines the ratio of
recovery lube heat to fuel energy. Used to calculate the
recoverable lube oil heat as a function of part-load ratio.
The defining equation is:
This alpha field contains the name of the Total Exhaust
Energy curve. The curve itself is specified separately using a
curve object (ref Curve:QuadLinear
object). The Total Exhaust Energy Curve is a quadratic
equation that determines the ratio of total exhaust energy to
fuel energy. Used to calculate the total exhaust heat as a
function of part-load ratio. The defining equation is:
This alpha field contains the name of the Exhaust
Temperature curve. The curve itself is specified separately
using a curve object (ref Curve:QuadLinear
object). The Exhaust Temperature Curve is a quadratic equation
that determines the absolute exhaust temperature. Used to
determine the exhaust gas temperature as a function of
part-load ratio. The defining equation is:
The UA curve applies to the exhaust gas heat exchanger. The
curve is an equation that determines the overall heat transfer
coefficient for the exhaust gases with the stack. The heat
transfer coefficient ultimately helps determine the exhaust
stack temperature. The defining equation is:
The following two fields contain the coefficients for the
equation.
Field:
Coefficient 1 of U-Factor Times Area Curve[LINK]
This numeric field contains the first coefficient for the
overall heat transfer coefficient curve.
Field:
Coefficient 2 of U-Factor Times Area Curve[LINK]
This numeric field contains the second (exponential)
coefficient for the overall heat transfer coefficient
curve.
Field:
Maximum Exhaust Flow per Unit of Power Output[LINK]
Maximum exhaust flow per unit capacity for the generator.
The parameter sets an upper limit on exhaust gas flow and
exhaust gas heat recovery for the generator. Units: kg/sec per
kW capacity
This alpha field determines the type of fuel that the
generator uses. The default is Diesel. Valid values are:
NaturalGas, PropaneGas,
Diesel, Gasoline,
FuelOil#1, FuelOil#2,
OtherFuel1, and OtherFuel2.
This field sets the maximum temperature that this piece of
equipment can produce for heat recovery. The idea behind this
field is that the current models do not take temperatures into
account for availability and they just pass Q’s around the
loop without a temperature limit. This temperature limit puts
an upper bound on the recovered heat and limits the max
temperatures leaving the component.
As temperatures in the loop approach the maximum
temperature, the temperature difference between the entering
water and the surfaces in the piece of equipment becomes
smaller. For the given heat recovery flow rate and that
temperature difference the amount of heat recovered will be
reduced, and eventually there will be no heat recovered when
the entering water temperature is equal to the maximum
temperature specified by the user in this field. The reduced
amount of heat recovered will diminish if the temperature of
the loop approach is the maximum temperature, and this will
show up in the reporting. This allows the user to set the
availability or the quality of the heat recovered for usage in
other parts of the system or to heat domestic hot water
supply.
The temperature is specified in degrees C.
An IDF example showing how it is used is provided
below:
Generator:InternalCombustionEngine,
Cat Diesel, !- Name
50000, !- Rated Power Output {W}
Generator Diesel Electric Node, !- Electric Circuit Node Name
0.15, !- Minimum Part Load Ratio
1.0, !- Maximum Part Load Ratio
0.65, !- Optimum Part Load Ratio
BG Shaft Power Curve, !- Shaft Power Curve Name
BG Recovery Jacket Heat Curve, !- Jacket Heat Recovery Curve Name
BG Recovery Lube Heat Curve, !- Lube Heat Recovery Curve Name
BG Total Exhaust Energy Curve, !- Total Exhaust Energy Curve Name
BG Exhaust Temperature Curve, !- Exhaust Temperature Curve Name
0.00952329, !- Coefficient 1 of U-Factor Times Area Curve
0.9, !- Coefficient 2 of U-Factor Times Area Curve
0.00000063, !- Maximum Exhaust Flow per Unit of Power Output {(kg/s)/W}
150, !- Design Minimum Exhaust Temperature {C}
45500, !- Fuel Higher Heating Value {kJ/kg}
0.0, !- Design Heat Recovery Water Flow Rate {m3/s}
, !- Heat Recovery Inlet Node Name
, !- Heat Recovery Outlet Node Name
Diesel; !- Fuel Type
Curve:Quadratic,
BG Shaft Power Curve, !- Name
0.09755, !- Coefficient1 Constant
0.6318, !- Coefficient2 x
-0.4165, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Recovery Jacket Heat Curve, !- Name
0.25, !- Coefficient1 Constant
0, !- Coefficient2 x
0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Recovery Lube Heat Curve, !- Name
0.15, !- Coefficient1 Constant
0, !- Coefficient2 x
0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Total Exhaust Energy Curve, !- Name
0.1, !- Coefficient1 Constant
0, !- Coefficient2 x
0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Exhaust Temperature Curve, !- Name
425, !- Coefficient1 Constant
0, !- Coefficient2 x
0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
These outputs are the electric power output from the
electric generator. Energy is metered on
Cogeneration:ElectricityProduced, ElectricityProduced:Plant,
and ElectricityProduced:Facility.
For electric generators with heat recovery these outputs
are the components of recoverable energy available. For the IC
engine generator, the following heat recovery components are
reported: Lube (engine lubricant), Jacket (engine coolant),
and Exhaust (engine exhaust). These components are totaled
together for Generator Produced Thermal Rate and Generator
Produced Thermal Energy reports. Generator Lube Heat Recovery
Energy, Generator Jacket Heat Recovery Energy, and Generator
Exhaust Heat Recovery Energy are metered on
HeatRecovery:EnergyTransfer, EnergyTransfer:Plant, and
EnergyTransfer:Facility.
If the fuel type is Diesel, then Diesel is shown as the
fuel type. They are the diesel fuel input to the electric
generator. Consumption is metered on Cogeneration:Diesel,
Diesel:Plant, and Diesel:Facility.
If the fuel type is Natural Gas, then Gas is shown as the
fuel type. They are the natural gas fuel input to the electric
generator. Consumption is metered on Cogeneration:Gas,
Gas:Plant, and Gas:Facility.
If the fuel type is Propane, then Propane is shown as the
fuel type. They are the propane fuel input to the electric
generator. Consumption is metered on Cogeneration:Propane,
Propane:Plant, and Propane:Facility.
If the fuel type is Gasoline, then Gasoline is shown as the
fuel type. They are the gasoline fuel input to the electric
generator. Consumption is metered on Cogeneration:Gasoline,
Gasoline:Plant, and Gasoline:Facility.
If the fuel type is FuelOil#1, then FuelOil#1 is shown as
the fuel type. They are the fuel oil input to the electric
generator. Consumption is metered on Cogeneration:FuelOil#1,
FuelOil#1:Plant, and FuelOil#1:Facility.
If the fuel type is FuelOil#2, then FuelOil#2 is shown as
the fuel type. They are the fuel oil input to the electric
generator. Consumption is metered on Cogeneration:FuelOil#2,
FuelOil#2:Plant, and FuelOil#2:Facility.
If the fuel type is OtherFuel1, then OtherFuel1 is shown as
the fuel type. They are the fuel oil input to the electric
generator. Consumption is metered on Cogeneration:OtherFuel1,
OtherFuel1:Plant, and OtherFuel1:Facility.
If the fuel type is OtherFuel2, then OtherFuel2 is shown as
the fuel type. They are the fuel oil input to the electric
generator. Consumption is metered on Cogeneration:OtherFuel2,
OtherFuel2:Plant, and OtherFuel2:Facility.
EnergyPlus has two different models for combustion turbine
style generators. This one stems for a model that was
originally in the BLAST computer program. A newer model with a
different formulation is also available–see the Generator:MicroTurbine
input object. The basic combustion-turbine cycle is the
Brayton Cycle or open cycle, which consists of an adiabatic
compression, constant pressure heating, and adiabatic
expansion. The Combustion turbine model uses the electrical
load and engine generator size to compute part-load ratios
(PLR). Fuel energy input and recoverable lube oil heat are
then computed. Finally, the recoverable exhaust heat is
calculated.
Combustion turbine generators use performance parameters to
compute fuel energy consumption as a function of part-load and
ambient (entering) air temperature. Recoverable fuel energy
equipment, recoverable lube oil heat/fuel energy input
equipment performance, total exhaust heat/fuel energy input
equipment, exhaust gas temperature/fuel energy input equipment
performance parameters are all specified with a quadratic
curve fit.
When the heat recovery curve fits = 0.0, this means that no
heat recovery is done on the diesel generator exhaust gas; and
no heat recovery is specified.
This alpha field contains the optimal operating fraction of
full load. This is the part load ratio that gives the optimal
production of electric power with the least amount of fuel
usage.
Field:
Part Load Based Fuel Input Curve Name[LINK]
The Total Exhaust Energy Curve is a quadratic equation that
needs to be specified by a curve object. Used to calculate the
total exhaust heat as a function of part-load ratio.
Field:
Part Load Based Exhaust Temperature Curve Name[LINK]
The Exhaust Temperature Curve is a quadratic equation that
needs to be specified by a curve object. Used to determine the
exhaust gas temperature as a function of part-load ratio.
Field:
Temperature Based Exhaust Temperature Curve Name[LINK]
The Exhaust Temperature Curve is a quadratic equation that
needs to be specified by a curve object. Used to determine the
exhaust gas temperature as a function of part-load ratio.
This alpha field contains the name of the Recovery Lube
Heat curve. The curve itself is specified separately using a
curve object (see Curve:Quadlinear object). The Recovery
Lubricant Heat Curve is a quadratic equation that determines
the ratio of recovery lube heat to fuel energy. Used to
calculate the recoverable lube oil heat as a function of
part-load ratio. The defining equation is:
The UA curve applies to the exhaust gas heat exchanger. The
curve is an equation that determines the overall heat transfer
coefficient for the exhaust gases with the stack. The heat
transfer coefficient ultimately helps determine the exhaust
stack temperature. The defining equation is:
The following two fields contain the coefficients for the
equation.
Field:
Coefficient 1 of U-Factor Times Area Curve[LINK]
This numeric field contains the first coefficient for the
overall heat transfer coefficient curve.
Field:
Coefficient 2 of U-Factor Times Area Curve[LINK]
This numeric field contains the second (exponential)
coefficient for the overall heat transfer coefficient
curve.
Field:
Maximum Exhaust Flow per Unit of Power Output[LINK]
Maximum exhaust flow per unit capacity for diesel engines.
The parameter sets an upper limit on exhaust gas flow and
exhaust gas heat recovery for diesel engines. Units: kg/sec
per kW capacity
This alpha field determines the type of fuel that the
generator uses. Valid choices are: NaturalGas,
PropaneGas, Diesel, Gasoline, FuelOil#1, FuelOil#2,
OtherFuel1 and OtherFuel2. The
default is NaturalGas.
This field sets the maximum temperature that this piece of
equipment can produce for heat recovery. The idea behind this
field is that the current models do not take temperatures into
account for availability and they just pass Q’s around the
loop without a temperature limit. This temperature limit puts
an upper bound on the recovered heat and limits the max
temperatures leaving the component.
As temperatures in the loop approach the maximum
temperature, the temperature difference between the entering
water and the surfaces in the piece of equipment becomes
smaller. For the given heat recovery flow rate and that
temperature difference the amount of heat recovered will be
reduced, and eventually there will be no heat recovered when
the entering water temperature is equal to the maximum
temperature specified by the user in this field. The reduced
amount of heat recovered will diminish if the temperature of
the loop approach is the maximum temperature, and this will
show up in the reporting. This allows the user to set the
availability or the quality of the heat recovered for usage in
other parts of the system or to heat domestic hot water
supply.
This field is optional. It is used to explicitly define an
outdoor air node for the inlet for combustion air stream.
Defining an outdoor air node here allows using the
height-dependent model for outdoor air conditions.
An IDF example showing how it is used is provided
below:
Generator:CombustionTurbine,
Solar Turbine, !- Name
30000, !- Rated Power Output {W}
GT gen Electric Node, !- Electric Circuit Node Name
0.15, !- Minimum Part Load Ratio
1.0, !- Maximum Part Load Ratio
0.65, !- Optimum Part Load Ratio
BG PL Based Fuel Input Curve, !- Part Load Based Fuel Input Curve Name
BG Temp Based Fuel Input Curve, !- Temperature Based Fuel Input Curve Name
BG Exhaust Flow Curve, !- Exhaust Flow Curve Name
BG PL Based Exhaust Temp Curve, !- Part Load Based Exhaust Temperature Curve Name
BG Temp Based Exhaust Temp Curve, !- Temperature Based Exhaust Temperature Curve Name
BG Tur Recovery Lube Heat Curve, !- Heat Recovery Lube Energy Curve Name
0.01907045, !- Coefficient 1 of U-Factor Times Area Curve
0.9, !- Coefficient 2 of U-Factor Times Area Curve
0.00000504, !- Maximum Exhaust Flow per Unit of Power Output {(Kg/s)/W}
150, !- Design Minimum Exhaust Temperature {C}
25, !- Design Air Inlet Temperature {C}
43500, !- Fuel Higher Heating Value {kJ/kg}
0.0, !- Design Heat Recovery Water Flow Rate {m3/s}
, !- Heat Recovery Inlet Node Name
, !- Heat Recovery Outlet Node Name
NaturalGas, !- Fuel Type
, !- Heat Recovery Maximum Temperature {C}
CT OA inlet; !- Outdoor Air Inlet Node Name
Curve:Quadratic,
BG PL Based Fuel Input Curve, !- Name
9.41, !- Coefficient1 Constant
-9.48, !- Coefficient2 x
4.32, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Temp Based Fuel Input Curve, !- Name
1.0044, !- Coefficient1 Constant
-0.0008, !- Coefficient2 x
0, !- Coefficient3 x**2
-30, !- Minimum Value of x
+30; !- Maximum Value of x
Curve:Quadratic,
BG Exhaust Flow Curve, !- Name
0.05, !- Coefficient1 Constant
0.0, !- Coefficient2 x
0.0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG PL Based Exhaust Temp Curve, !- Name
450, !- Coefficient1 Constant
0, !- Coefficient2 x
0, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
Curve:Quadratic,
BG Temp Based Exhaust Temp Curve, !- Name
1.005, !- Coefficient1 Constant
0.0018, !- Coefficient2 x
0, !- Coefficient3 x**2
-30, !- Minimum Value of x
+30; !- Maximum Value of x
Curve:Quadratic,
BG Tur Recovery Lube Heat Curve, !- Name
0.223, !- Coefficient1 Constant
-0.4, !- Coefficient2 x
0.2286, !- Coefficient3 x**2
0, !- Minimum Value of x
1; !- Maximum Value of x
MicroTurbine generators are small combustion turbines that
produce electricity on a relatively small scale (e.g., 25kW to
500kW). This model uses nominal performance at reference
conditions along with several modifier curves to determine
electrical power output and fuel use at non-reference
conditions. Standby and ancillary power can also be taken into
account. Furthermore, energy recovery from exhaust air can be
used to heat water. Similar to electrical power output,
thermal power (heat recovery) output is calculated using
nominal performance at reference conditions with modifier
curves to account for variations at non-reference
conditions.
This numeric field specifies the full-load electrical power
output of the microturbine generator in Watts at reference
conditions. The reference conditions are defined via
additional input fields for this object (see below). This is a
required input, and the value entered in this field must be
greater than zero.
Field:
Minimum Full Load Electrical Power Output[LINK]
This numeric field specifies the minimum electrical power
output in Watts at full-load conditions. The electrical power
output of the generator is determined by multiplying the
Reference Electrical Power Output by the Electrical Power
Function of Temperature and Elevation modifier curve. If the
result is less than the numeric value specified in this input
field, then the generator’s electrical power output is reset
to the minimum full-load value specified in this input field.
The value entered in this field must be greater than or equal
to zero. If this field is left blank, the default value of 0.0
will be used.
Field:
Maximum Full Load Electrical Power Output[LINK]
This numeric field specifies the maximum electrical power
output in Watts at full-load conditions. The electrical power
output of the generator is determined by multiplying the
Reference Electrical Power Output by the Electrical Power
Function of Temperature and Elevation Modifier curve. If the
result is greater than the numeric value specified in this
input field, then the generator’s electrical power output is
reset to the maximum full-load value specified in this input
field. The value entered in this field must be greater than
zero. If this field is left blank, then the value entered for
the Reference Electrical Power Output field (above) will be
used as the Maximum Full Load Electrical Power Output.
Field:
Reference Electrical Efficiency Using Lower Heating Value[LINK]
This numeric field contains the electrical efficiency of
the generator at reference conditions, based on the lower
heating value of the fuel. The electrical efficiency is the
electric power output divided by the fuel energy consumption
rate (LHV basis). The reference conditions are defined via
additional input fields for this object (see below). This is a
required input, and the value entered in this field must be
greater than zero and less than or equal to 1.0.
Field:
Reference Combustion Air Inlet Temperature[LINK]
This numeric field specifies the reference temperature for
the combustion inlet air in degrees Celsius. If this field is
left blank, the default value of 15°C will be used.
Field:
Reference Combustion Air Inlet Humidity Ratio[LINK]
This numeric field specifies the reference humidity ratio
for the combustion inlet air in kgWater/kgDryAir. The value
specified for this field must be greater than zero. If this
field is left blank, the default value of 0.00638
(kgWater/kgDryAir) will be used.
This numeric field specifies the reference elevation in
meters (relative to sea level). The value specified for this
field must be greater than or equal to -300.0 meters. If this
field is left blank, the default value of 0.0 meters will be
used.
Field:
Electrical Power Function of Temperature and Elevation Curve
Name[LINK]
This alpha field specifies the name of a bi-quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of electrical power output as a function of the
combustion air inlet temperature and elevation. The output of
this curve is multiplied by the Reference Electrical Power
Output to give the full-load power output at a specific
combustion air inlet temperature and elevation (i.e., at
values different from the reference conditions). This curve
should be normalized to have a value of 1.0 at the reference
conditions, and the curve should be valid for the range of
inlet air temperatures anticipated for the simulation period
and for the actual elevation of the generator.
Field:
Electrical Efficiency Function of Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of electrical efficiency as a function of the
combustion air inlet temperature. The output of this curve is
multiplied by the Reference Electrical Efficiency Using Lower
Heating Value to give the full-load electrical efficiency at
specific combustion air inlet temperatures (i.e., at inlet air
temperatures different from the Reference Combustion Air Inlet
Temperature). This curve should be normalized to have a value
of 1.0 at the Reference Combustion Air Inlet Temperature, and
the curve should be valid for the range of inlet air
temperatures anticipated for the simulation period.
Field:
Electrical Efficiency Function of Part Load Ratio Curve
Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of electrical efficiency as a function of the
generator’s part-load ratio (part-load ratio is the actual
electrical power output divided by the full-load electrical
power output at the current operating conditions). The output
of this curve is multiplied by the Reference Electrical
Efficiency Using Lower Heating Value and the output of the
Electrical Efficiency Function of Temperature modifier curve
to give the electrical efficiency at specific part-load and
combustion air inlet (temperature) conditions. This curve
should be normalized to have a value of 1.0 when the
generator’s part-load ratio is 1.0, and the curve should be
valid for the range of part-load ratios anticipated for the
simulation period.
This choice field specifies the type of fuel used by the
generator. Valid fueld types are PropaneGas and NaturalGas. If
the field is left blank, the fuel type will be assumed to be
NaturalGas.
This numeric field specifies the higher heating value of
the fuel used in kJ/kg. The value specified for this field
must be greater than zero and greater than the specified Fuel
Lower Heating Value. If this field is left blank, the default
value of 50,000 kJ/kg will be used.
This numeric field specifies the lower heating value of the
fuel used in kJ/kg. The value specified for this field must be
greater than zero but less than the specified Fuel Higher
Heating Value. If this field is left blank, the default value
of 45,450 kJ/kg will be used.
This numeric field specifies the standby electric power
consumed by the generator in Watts. The standby power is the
electrical power consumed by the generator (e.g., air fans and
controls) when the generator is available to operate but the
generator electrical power output is zero (power output is not
being requested by the electric load center). The value
specified for this field must be greater than or equal to
zero. If this field is left blank, the default value of 0.0 W
will be used.
This numeric field specifies the ancillary electric power
consumed by the generator in Watts. The ancillary power is the
electrical power consumed by other associated equipment (e.g.,
external fuel pressurization pumps) when the generator is
operating. Specify this input as 0.0 if the Reference
Electrical Power Output and Reference Electrical Efficiency
Using Lower Heating Value input fields and associated modifier
curves reflect the “net” electrical power output from the
generator (i.e., ancillary power already deducted from the
generator’s gross electrical power output). A value greater
than zero indicates that this electrical power is consumed
whenever the generator is operating and will be deducted from
the generator’s overall electrical power output (Generator
Produced Electric Power). The value specified for this field
must be greater than or equal to zero. If this field is left
blank, the default value of 0.0 W will be used.
Field:
Ancillary Power Function of Fuel Input Curve Name[LINK]
This alpha field specifies the name of a quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of ancillary power as a function of the
generator’s input fuel mass flow rate (kg/s). The output of
this curve is multiplied by the ancillary power to give the
ancillary power at a specific fuel mass flow rate. If this
field is left blank, the model assumes that the modifier curve
is 1.0 for the entire simulation (i.e., the ancillary power is
constant whenever the generator operates).
This alpha field specifies the identifying name for the
generator’s heat recovery water outlet node.
Field:
Reference Thermal Efficiency Using Lower Heat Value[LINK]
This numeric field specifies the thermal efficiency (heat
recovery to water) at reference conditions, based on the lower
heating value of the fuel. The thermal efficiency is the
thermal power output (to water) divided by the fuel energy
consumption rate (LHV basis). The reference conditions are
defined via additional input fields for this object. This
value must be from 0.0 to 1.0. If this field is left blank,
the default value of 0.0 will be used.
This numeric field specifies the reference temperature for
the inlet water to the heat recovery heat exchanger in degrees
Celsius.
Field:
Heat Recovery Water Flow Operating Mode[LINK]
This field is used to choose between different modes of
controlling the mass flow rate of water being heated by energy
recovered from exhaust air. There are two options available
for this field: “PlantControl” or “InternalControl.” The
“PlantControl” option indicates that the heat recovery water
flow rate through the generator is determined externally (by
the wider balance of plant). In this case, the generator will
request the Reference Heat Recovery Water Flow Rate whenever
it operates but the actual flow rate may be limited by other
plant components (e.g., pump). The “InternalControl” option
indicates the flow of water is controlled inside the generator
based on current operating conditions. For InternalControl,
the generator should (probably) include a bypass branch when
connecting to the plant loop.
Field:
Reference Heat Recovery Water Flow Rate[LINK]
This numeric field is the reference heat recovery
(volumetric) water flow rate in cubic meters per second.
Entered values must be greater than zero.
Field:
Heat Recovery Water Flow Rate Function of Temperature and
Power Curve Name[LINK]
This alpha field specifies the name of a bi-quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of heat recovery water flow rate as a function
of the inlet water temperature and net electrical power
output. This field is only used if the Heat Recovery Water
Flow Operating Mode is ‘InternalControl’. The output of this
curve is multiplied by the Reference Heat Recovery Water Flow
Rate to give the water flow rate at the specific inlet water
temperature and net power operating conditions. This curve
should be normalized to have a value of 1.0 at the reference
conditions, and the curve should be valid for the range of
inlet water temperatures and net electrical power output
anticipated for the simulation period. If this field is left
blank, the model assumes that the modifier curve is 1.0 for
the entire simulation.
Field:
Thermal Efficiency Function of Temperature and Elevation Curve
Name[LINK]
This alpha field specifies the name of a bi-quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of thermal efficiency as a function of the
combustion air inlet temperature and elevation. The output of
this curve is multiplied by the Reference Thermal Efficiency
Using Lower Heating Value to give the full-load thermal
efficiency at a specific combustion air inlet temperature and
elevation (i.e., at values different from the reference
conditions). This curve should be normalized to have a value
of 1.0 at the reference conditions, and the curve should be
valid for the range of inlet air temperatures anticipated for
the simulation period and for the actual elevation of the
generator. If this field is left blank, the model assumes that
the modifier curve is 1.0 for the entire simulation.
Field:
Heat Recovery Rate Function of Part Load Ratio Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of heat recovery to water (thermal power output)
as a function of the generator’s part-load ratio (part-load
ratio is the actual electrical power output divided by the
full-load electrical power output at the current operating
conditions). The output of this curve is multiplied by the
steady-state heat recovery at the current combustion inlet air
temperature and elevation to give the heat recovery rate
(thermal power output) at specific part-load operating
conditions. This curve should be normalized to have a value of
1.0 when the generator’s part-load ratio is 1.0, and the curve
should be valid for the range of part-load ratios anticipated
for the simulation period. If this field is left blank, the
model assumes that the modifier curve is 1.0 for the entire
simulation.
Field:
Heat Recovery Rate Function of Inlet Water Temperature Curve
Name[LINK]
This alpha field specifies the name of a quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of heat recovery to water (thermal power output)
as a function of the inlet water temperature. The output of
this curve is multiplied by the steady-state heat recovery at
the current combustion inlet air temperature and elevation to
give the heat recovery rate (thermal power output) at
non-reference inlet water conditions. This curve should be
normalized to have a value of 1.0 at the Reference Inlet Water
Temperature, and the curve should be valid for the range of
inlet water temperatures anticipated for the simulation
period. If this field is left blank, the model assumes that
the modifier curve is 1.0 for the entire simulation.
Field:
Heat Recovery Rate Function of Water Flow Rate Curve Name[LINK]
This alpha field specifies the name of a quadratic
performance curve (ref: Performance Curves) that parameterizes
the variation of heat recovery to water (thermal power output)
as a function of the heat recovery water flow rate. The output
of this curve is multiplied by the steady-state heat recovery
at the current combustion inlet air temperature and elevation
to give the heat recovery rate (thermal power output) at
non-reference heat recovery water flow rates. This curve
should be normalized to have a value of 1.0 at the Reference
Heat Recovery Water Flow Rate, and the curve should be valid
for the range of water flow rates anticipated for the
simulation period. If this field is left blank, the model
assumes that the modifier curve is 1.0 for the entire
simulation.
Field:
Minimum Heat Recovery Water Flow Rate[LINK]
This numeric field specifies the minimum (volumetric) water
flow rate through the heat recovery heat exchanger in cubic
meters per second. The minimum input value is 0.0, and a value
of 0.0 is assumed if this field is left blank.
Field:
Maximum Heat Recovery Water Flow Rate[LINK]
This numeric field specifies the maximum (volumetric) water
flow rate through the heat recovery heat exchanger in cubic
meters per second. The minimum input value for this field is
0.0, and a value of 0.0 is assumed if this field is left
blank. The maximum heat recovery water flow rate must be
greater than or equal to the minimum heat recovery water flow
rate.
Field:
Maximum Heat Recovery Water Temperature[LINK]
This field sets the maximum water temperature, in degrees
Celsius, that this generator can produce via heat recovery.
This temperature limit puts an upper bound on the recovered
heat and limits the max temperatures leaving the
component.
As temperatures in the water loop approach this maximum
temperature, the temperature difference between the entering
water and the surfaces in generator’s heat recovery heat
exchanger becomes smaller. For the given heat recovery flow
rate and that temperature difference the amount of heat
recovered will be reduced, and eventually there will be no
heat recovered when the entering water temperature is equal to
the maximum temperature specified by the user in this field.
The amount of heat recovered will diminish if the inlet water
temperature approaches the maximum temperature, and this will
show up in the reporting.
This alpha field specifies the name of the combustion air
inlet node. If a node name is specified, this node must be an
outdoor air node and must also be specified elsewhere in the
input (ref: OutdoorAir:Node
and OutdoorAir:NodeList). If this field is left blank, the
combustion air inlet conditions are assumed to be the outdoor
weather conditions used for the simulation.
This numeric field is the reference exhaust air mass flow
rate in kilograms per second. Entered values must be greater
than zero.
Field:
Exhaust Air Flow Rate Function of Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of exhaust air flow rate as a function of the
combustion air inlet temperature. The output of this curve is
multiplied by the Reference Exhaust Air Mass Flow Rate to give
the exhaust air mass flow rate at non-reference combustion air
inlet temperatures. This curve should be normalized to have a
value of 1.0 at the Reference Combustion Air Inlet
Temperature, and the curve should be valid for the range of
inlet air temperatures anticipated for the simulation period.
If this field is left blank, the model assumes that the
modifier curve is 1.0 for the entire simulation.
Field:
Exhaust Air Flow Rate Function of Part Load Ratio Curve
Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of exhaust air flow rate as a function of the
generator’s part-load ratio (part-load ratio is the actual
electrical power output divided by the full-load electrical
power output at the current operating conditions). The output
of this curve is multiplied by the Reference Exhaust Air Mass
Flow Rate to give the exhaust air mass flow rate at specific
part-load operating conditions. This curve should be
normalized to have a value of 1.0 when the generator’s
part-load ratio is 1.0, and the curve should be valid for the
range of part-load ratios anticipated for the simulation
period. If this field is left blank, the model assumes that
the modifier curve is 1.0 for the entire simulation.
Field:
Nominal Exhaust Air Outlet Temperature[LINK]
This numeric field is the exhaust air outlet temperature at
nominal (reference) conditions in degrees Celsius.
Field:
Exhaust Air Temperature Function of Temperature Curve
Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of exhaust air outlet temperature as a function
of the combustion air inlet temperature. The output of this
curve is multiplied by the Nominal Exhaust Air Outlet
Temperature to give the exhaust air temperature at
non-reference combustion air inlet temperatures. This curve
should be normalized to have a value of 1.0 at the Reference
Combustion Air Inlet Temperature, and the curve should be
valid for the range of inlet air temperatures anticipated for
the simulation period. If this field is left blank, the model
assumes that the modifier curve is 1.0 for the entire
simulation.
Field:
Exhaust Air Temperature Function of Part Load Ratio Curve
Name[LINK]
This alpha field specifies the name of a quadratic or cubic
performance curve (ref: Performance Curves) that parameterizes
the variation of exhaust air outlet temperature as a function
of the generator’s part-load ratio (part-load ratio is the
actual electrical power output divided by the full-load
electrical power output at the current operating conditions).
The output of this curve is multiplied by the Nominal Exhaust
Air Outlet Temperature to give the exhaust air temperature at
specific part-load operating conditions. This curve should be
normalized to have a value of 1.0 when the generator’s
part-load ratio is 1.0, and the curve should be valid for the
range of part-load ratios anticipated for the simulation
period. If this field is left blank, the model assumes that
the modifier curve is 1.0 for the entire simulation.
An example IDF showing how this object is used is provided
below:
Generator:MicroTurbine,
Generator 3, !- Name
65000, !- Reference Electrical Power Output {W}
29900, !- Minimum Full Load Electrical Power Output {W}
65000, !- Maximum Full Load Electrical Power Output {W}
0.29, !- Reference Electrical Efficiency Using Lower Heating Value
15.0, !- Reference Combustion Air Inlet Temperature {C}
0.00638, !- Reference Combustion Air Inlet Humidity Ratio (kgWater/kgDryAir)
0.0, !- Reference Elevation {m}
Power_vs_Temp_Elev, !- Electrical Power Function of Temperature and Elevation Curve Name
Efficiency_vs_Temp, !- Electrical Efficiency Function of Temperature Curve Name
Efficiency_vs_PLR, !- Electrical Efficiency Function of Part Load Ratio Curve Name
NaturalGas, !- Fuel Type
50000, !- Fuel Higher Heating Value {kJ/kg}
45450, !- Fuel Lower Heating Value {kJ/kg}
300, !- Standby Power {W}
4500; !- Ancillary Power {W}
! Electrical Power Modifier Curve (function of temperature and elevation)
! x = Dry-Bulb Temperature of Combustion Inlet Air (C) and y = Elevation (meters)
Curve:Biquadratic,
Power_vs_Temp_Elev, !- Name
1.2027697, !- Coefficient1 Constant
-9.671305E-03, !- Coefficient2 x
-4.860793E-06, !- Coefficient3 x**2
-1.542394E-04, !- Coefficient4 y
9.111418E-09, !- Coefficient5 y**2
8.797885E-07, !- Coefficient6 x*y
-17.8, !- Minimum Value of x
50.0, !- Maximum Value of x
0.0, !- Minimum Value of y
3050.; !- Maximum Value of y
! Electrical Efficiency Modifier Curve (function of temperature)
! x = Dry-Bulb Temperature of Combustion Inlet Air (C)
Curve:Cubic,
Efficiency_vs_Temp, !- Name
1.0402217, !- Coefficient1 Constant
-0.0017314, !- Coefficient2 x
-6.497040E-05, !- Coefficient3 x**2
5.133175E-07, !- Coefficient4 x**3
-20.0, !- Minimum Value of x
50.0; !- Maximum Value of x
! Electrical Efficiency Modifier Curve (function of part-load ratio)
! x = Part-Load Ratio (electrical load/steady-state electrical power output)
Curve:Cubic,
Efficiency_vs_PLR, !- Name
0.215290, !- Coefficient1 Constant
2.561463, !- Coefficient2 x
-3.24613, !- Coefficient3 x**2
1.497306, !- Coefficient4 x**3
0.03, !- Minimum Value of x
1.0; !- Maximum Value of x!
ElectricLoadCenter:Distribution,
Electric Load Center, !- Name
Backup Generators, !- Generator List Name
DemandLimit, !- Generator Operation Scheme Type
10000.0, !- Demand Limit Scheme Purchased Electric Demand Limit {W}
, !- Track Schedule Name Scheme Schedule Name
, !- Track Meter Scheme Meter Name
AlternatingCurrent, !- Electrical Buss Type
, !- Inverter Object Name
; !- Electrical Storage Object Name
ElectricLoadCenter:Generators,
Backup Generators, !- Name
Generator 1, !- Generator 1 Name
Generator:InternalCombustionEngine, !- Generator 1 Object Type
50000, !- Generator 1 Rated Electric Power Output
ON PEAK GENERATOR SCHEDULE, !- Generator 1 Availability Schedule Name
, !- Generator 1 Rated Thermal to Electrical Power Ratio
Generator 2, !- Generator 2 Name
Generator:CombustionTurbine, !- Generator 2 Object Type
30000, !- Generator 2 Rated Electric Power Output
OFF PEAK GENERATOR SCHEDULE, !- Generator 2 Availability Schedule Name
, !- Generator 2 Rated Thermal to Electrical Power Ratio
Generator 3, !- Generator 3 Name
Generator:MicroTurbine, !- Generator 3 Object Type
65000, !- Generator 3 Rated Electric Power Output
MID PEAK GENERATOR SCHEDULE, !- Generator 3 Availability Schedule Name
; !- Generator 3 Rated Thermal to Electrical Power Ratio
The output variables that are available for the
microturbine generator are:
HVAC,Average,Generator Produced Electric Power [W]
HVAC,Sum,Generator Produced Electric Energy [J]
HVAC,Average,Generator LHV Basis Electric Efficiency [-]
HVAC,Average,Generator <Fuel Type> HHV Basis Rate [W]
HVAC,Average,Generator Fuel HHV Basis Rate [W]
HVAC,Sum,Generator <Fuel Type> HHV Basis Energy [J]
HVAC,Sum,Generator Fuel HHV Basis Energy [J]
HVAC,Average,Generator <Fuel Type> Mass Flow Rate [kg/s]
If Standby Power input field > 0.0:
HVAC,Average,Generator Standby Electric Power [W]
HVAC,Sum,Generator Standby Electric Energy [J]
If Ancillary Power input field > 0.0:
HVAC,Average,Generator Ancillary Electric Power [W]
HVAC,Sum,Generator Ancillary Electric Energy [J]
If heat recovery water inlet and outlet node names are entered (and valid):
HVAC,Average,Generator Produced Thermal Rate [W]
HVAC,Sum,Generator Produced Thermal Energy [J]
HVAC,Average,Generator Thermal Efficiency LHV Basis [-]
HVAC,Average,Generator Heat Recovery Inlet Temperature [C]
HVAC,Average,Generator Heat Recovery Outlet Temperature [C]
HVAC,Average,Generator Heat Recovery Water Mass Flow Rate [kg/s]
If exhaust air calculations are performed:
HVAC,Average,Generator Exhaust Air Mass Flow Rate [kg/s]
HVAC,Average,Generator Exhaust Air Temperature [C]
This output variable is the average electric power produced
by the generator in Watts for the timestep being reported.
This is the “net” electric power produced, accounting for
ancillary electric power consumed during generator
operation.
This output variable is the electric energy produced by the
generator in Joules for the timestep being reported. This
output is also added to a meter with Resource Type =
ElectricityProduced, End Use Key = Cogeneration, Group Key =
Plant (Ref. Output:Meter
objects). This is the “net” electric energy produced,
accounting for ancillary electric consumption during generator
operation.
This output variable is the average electric efficiency of
the generator (lower heating value basis) for the timestep
being reported. The electric efficiency is the Generator
Produced Electric Power in Watts divided by the generator’s
fuel energy consumption rate in Watts (lower heating value
basis).
This output variable is the average fuel-specific energy
consumption rate of the electric generator in Watts (higher
heating value basis) for the timestep being reported.
is the name of the fuel used by this electric
generator. can be one of the following: NaturalGas
(=> ‘Gas’) or PropaneGas (=>‘Propane’).
This output variable is the average fuel energy consumption
rate of the electric generator in Watts (higher heating value
basis) for the timestep being reported. The output variable
name is non-fuel specific.
This output variable is the fuel-specific energy
consumption of the electric generator in Joules (higher
heating value basis) for the timestep being reported. This
output is also added to a meter with Resource Type =
, End Use Key = Cogeneration, Group Key = Plant
(Ref. Output:Meter
objects). is the name of the fuel used by this
electric generator. can be one of the following:
NaturalGas (=> ‘Gas’) or PropaneGas (=>‘Propane’).
This output variable is the fuel energy consumption of the
electric generator in Joules (higher heating value basis) for
the timestep being reported. The output variable name is
non-fuel specific.
This output variable is the average mass flow rate of fuel
being consumed by the electric generator in kg/s for the
timestep being reported. is the name of the fuel
used by this electric generator. can be one of the
following: Natural Gas (=> ‘Gas’) or Propane Gas
(=>‘Propane’).
This output variable is the average standby electric power
consumed by the generator in Watts for the timestep being
reported. Standby power is electrical power consumed by the
generator (e.g., air fans and controls) when the generator is
available to operate but the generator electrical power output
is zero (power output is not being requested by the electric
load center). This output variable is only produced when the
user enters a value greater than 0.0 for the input field
Standby Power.
This output variable is the standby electric energy
consumption for the generator in Joules for the timestep being
reported. This output is also added to a meter with Resource
Type = Electricity, End Use Key = Cogeneration, Group Key =
Plant (Ref. Output:Meter
objects). This output variable is only produced when the user
enters a value greater than 0.0 for the input field Standby
Power.
This output variable is the average ancillary electric
power consumed by the generator in Watts for the timestep
being reported. Ancillary power is the electrical power
consumed by other associated equipment (e.g., external fuel
pressurization pumps) when the generator is operating. This
output variable is only produced when the user enters a value
greater than 0.0 for the input field Ancillary Power.
This output variable is the ancillary electric energy
consumption for the generator in Joules for the timestep being
reported. This energy consumption is already deducted from the
output variable Generator Produced Electric Energy (“net”
electric energy produced by the generator). This output
variable is only produced when the user enters a value greater
than 0.0 for the input field Ancillary Power.
This output variable is the thermal energy produced (i.e.,
exhaust energy recovery to heat water) in Joules for the
timestep being reported. This output is also added to a meter
with Resource Type = EnergyTransfer, End Use Key =
HeatRecovery, Group Key = Plant (Ref. Output:Meter
objects).
This output variable is the average thermal efficiency of
the generator (lower heating value basis) for the timestep
being reported. The thermal efficiency is the Generator
Produced Thermal Rate in Watts divided by the generator’s fuel
energy consumption rate in Watts (lower heating value
basis).
Generator
Heat Recovery Inlet Temperature [C][LINK]
This output variable is the average heat recovery inlet
water temperature in degrees Celsius for the timestep being
reported.
Generator
Heat Recovery Outlet Temperature [C][LINK]
This output variable is the average heat recovery outlet
water temperature in degrees Celsius for the timestep being
reported.
Generator
Heat Recovery Water Mass Flow Rate [kg/s][LINK]
This output variable is the average heat recovery water
mass flow rate in kilograms per second for the timestep being
reported.
This object is used to model small-scale combined heat and
power (micro CHP) electric generators using the model
developed by IEA/ECBCS Annex 42 - see www.cogen-sim.net. The
model was developed for both internal combustion and Stirling
cycle engines, but might be used for other types of
residential CHP devices.
Note that unlike other component models in EnergyPlus, this
model is not normalized. Therefore, performance coefficients
developed for one type and capacity of CHP device cannot be
used for a device with a different capacity.
This model is an empirical, curve fit model. This object
describes the connections to the rest of the building model
and includes a reference to another object called Generator:MicroCHP:NonNormalizedParameters
that provides the operating characteristics.
This field contains the name of the thermal zone where the
CHP device is located in the model. If the device is outdoors,
or you do not want skin losses to be added to a zone, then
leave this field blank.
This field provides the name of a node that is the inlet to
the CHP device. The node should be on the plant loop that will
receive the heat from the residential CHP unit. This inlet
serves as the cooling water for the CHP device.
This field provides the name of a node that is the outlet
to the CHP device. The node should be on the plant loop that
will receive the heat from the residential CHP unit. This
outlet serves as the exit of the cooling water leaving the CHP
unit.
This field contains the name of a schedule used to control
whether or not the unit is available. It is “available” any
time the value is greater than zero. If it is available, it
may consume standby power at times when there is no request
for power from the Electric Load Center. If it is not
available (schedule value = 0.0) then the CHP unit is in a
completely off “mode” and will not consume standby power. If
this field is blank, the schedule has values of 1 for all time
periods.
An example IDF showing how this object is used is provided
below:
Generator:MicroCHP,
MicroCoGen1, !- Name
SENERTECH5_5KW, !- Performance Parameters Name
ZN_1_FLR_1_SEC_1, !- Zone Name
MICROCHP SENERTECH Pump-MicroCoGen1Node, !- Cooling Water Inlet Node Name
MICROCHP SENERTECH Supply Equipment Outlet Node, !- Cooling Water Outlet Node Name
MicroCoGen1 air inlet node, !- Air Inlet Node Name
, !- Air Outlet Node Name
NATURALGAS, !- Generator Fuel Supply Name
ALWAYS_ON; !- Availability Schedule Name
This is the size of the CHP unit in terms of the maximum
electrical power it can produce [W]. If the electric load
center requests more power than this maximum, then the unit
will restrict its output to this level.
This is the size of the CHP unit in terms of the minimum
electrical power it can produce [W]. If the electric load
center requests less power than this minimum, then the unit
will hold its output to this level.
This is the minimum flow rate of cooling water that must be
available for the unit to operate [kg/s]. If the plant loop is
not providing this flow of water, the unit will shut down to
protect it from overheating.
This is the name of Curve:Triquadratic
object that defines the steady-state net electrical
efficiency. The electrical efficiency, \({\eta _e}\), is a function of the
cooling water mass flow rate, \({\dot m_{cw}}\), the temperature
of the cooling water at the inlet, \({T_{cw}}\), the steady-state net
electrical power produced, \({P_{net,ss}}\).
The associated Curve:Triquadratic
object should be defined with the independent variables \({P_{net,ss}},{\dot
m_{cw}},{T_{cw}}\) corresponding to x,
y, and z, respectively.
This is the name of a Curve:Triquadratic
object that defines the steady-state net thermal efficiency.
The thermal efficiency, \({\eta
_q}\), is a function of the cooling water mass flow
rate, \({\dot m_{cw}}\), the
temperature of the cooling water at the inlet, \({T_{cw}}\), the steady-state net
electrical power produced, \({P_{net,ss}}\).
The associated Curve:Triquadratic
object should be defined with the independent variables \({P_{net,ss}},{\dot
m_{cw}},{T_{cw}}\) corresponding to x,
y, and z, respectively.
This field is used to choose between different modes of
controlling the mass flow rate of cooling water. There are two
options available for this field: “PlantControl” or
“InternalControl.” The “PlantControl” option indicates that
the cooling water flow rate through the CHP device is
determined externally (by the wider balance of plant). The
“InternalControl” option indicates the flow of cooling water
is controlled inside the CHP device (e.g., like an
automobile’s thermostat).
For internal control, the following field is used to define
a Biquadratic curve that will determine the cooling water flow
rate. For internal control, the CHP device should (probably)
include a bypass branch when connecting to the plant loop.
This field contains the name of a Curve:Biquadratic
object that defines the mass flow rate of cooling water, \({\dot m_{cw}}\). This field is
only used if the prior field is set to “InternalControl.” The
mass flow of cooling water is a function of steady-state
power, \({P_{net,ss}}\), and
the inlet temperature of the cooling water, \({T_{cw}}\). The associated Curve:Biquadratic
should be defined with the independent variables \({P_{net,ss}}\) and \({T_{cw}}\) corresponding to
x and y, respectively.
This field describes the split between thermal radiation
and thermal convection for the heat losses from the skin of
the generator.
Field:
Aggregated Thermal Mass of Energy Conversion Portion of
Generator[LINK]
This field describes the aggregated thermal mass of the
energy conversion portion of the generator. This includes the
engine block in an internal combustion engine.
Field:
Aggregated Thermal Mass of Heat Recovery Portion of
Generator[LINK]
This field describes the aggregated thermal mass of the
heat recovery portion of the generator. This includes the
encapsulated cooling water and heat exchanger shell in
immediate thermal contact.
This field describes the power used by the CHP unit’s
control systems while in standby operation. Standby operation
mode occurs whenever the unit is available but not being
called upon to produce power. Power is entered as a positive
value but indicates negative generation.
This field is used to choose between different modes of
controlling the warm up characteristics. Residential CHP units
such as Stirling engines have different warm up
characteristics than internal combustion engines. There are
two warm up modes available: “NominalEngineTemperature” or
“TimeDelay.” If the former mode is input in this field, then
the next three fields are used to model warm up. If the later
mode is input, then the fourth field below is used to model
warm up.
This field describes the value for the coefficient used to
determine the rate of fuel flow during warm up. The
coefficient, kf, is used in the following
relation,
This field describes the value for the coefficient used to
determine the rate of power production during warm up. The
coefficient kp is used in the following
relation,
This field is used to describe a limit to the fuel flow
rate during warm up. The limit is a ratio multiplied by the
maximum fuel flow rate during normal operation (corresponding
to the fuel flow for maximum electrical power). If the warm up
operating fuel flow rate is twice the steady state fuel flow
at maximum power, then a value of 2.0 would be entered in this
field. This field is only used with the nominal engine
temperature warm up mode and is intended for Stirling
engines.
This field describes the power used by the CHP unit’s
ancillary systems while in cool down operation mode. Cool down
operation mode occurs whenever the unit has recently been told
to stop producing power. Power here is consumed and entered as
a positive value that indicates negative generation. For
example, a component such as a cooling fan might continue to
run during cool down.
This field is used to describe the time it takes for the
CHP unit to cool off and complete the cool down operation.
Enter the time between deactivation and the end of a cool down
period in seconds.
This field is used to choose between two different control
situations for the cool down operation. The two options for
this field are “MandatoryCoolDown” and “OptionalCoolDown.” The
former is used to direct the model to complete the entire cool
down period before the generator can subsequently enter warm
up mode. The latter directs the model to allow immediately
switching to warm up mode, if power is requested before the
cool down period is completed.
An example IDF showing how this object is used is provided
below:
Generator:MicroCHP:NonNormalizedParameters,
SENERTECH5_5KW, !- Name
5500.0000, !- Maximum Electric Power {W}
0.0000, !- Minimum Electric Power {W}
0.0000, !- Minimum Cooling Water Flow Rate {kg/s}
80.0000, !- Maximum Cooling Water Temperature {C}
SenerTechElEff, !- Electrical Efficiency Curve Name
SenerTechThermEff, !- Thermal Efficiency Curve Name
InternalControl, !- Cooling Water Flow Rate Mode
SenerTechCoolWaterflow, !- Cooling Water Flow Rate Curve Name
SenerTechAirFlow, !- Air Flow Rate Curve Name
1000000000.0000, !- Maximum Net Electrical Power Rate of Change {W/s}
1000000000.0000, !- Maximum Fuel Flow Rate of Change {kg/s2}
741.0000, !- Heat Exchanger U-Factor Times Area Value {W/K}
13.7000, !- Skin Loss U-Factor Times Area Value {W/K}
0.5000, !- Skin Loss Radiative Fraction
63605.6000, !- Aggregated Thermal Mass of Energy Conversion Portion of Generator {W/K}
1000.7000, !- Aggregated Thermal Mass of Heat Recovery Portion of Generator {W/K}
0.0000, !- Standby Power {W}
TimeDelay, !- Warm Up Mode
, !- Warm Up Fuel Flow Rate Coefficient
, !- Nominal Engine Operating Temperature {C}
, !- Warm Up Power Coefficient
, !- Warm Up Fuel Flow Rate Limit Ratio
60.0000, !- Warm Up Delay Time {s}
0.0000, !- Cool Down Power {W}
60.0000, !- Cool Down Delay Time {s}
OptionalCoolDown; !- Restart Mode
HVAC,Sum,Generator Off Mode Time [s]
HVAC,Sum,Generator Standby Mode Time [s]
HVAC,Sum,Generator Warm Up Mode Time [s]
HVAC,Sum,Generator Normal Operating Mode Time [s]
HVAC,Sum,Generator Cool Down Mode Time [s]
HVAC,Average,Generator Produced Electric Power [W]
HVAC,Sum,Generator Produced Electric Energy [J]
HVAC,Average,Generator Electric Efficiency [ ]
HVAC,Average,Generator Thermal Efficiency [ ]
HVAC,Average,Generator Gross Input Heat Rate [W]
HVAC,Average,Generator Steady State Engine Heat Generation Rate [W]
HVAC,Average, Generator Engine Heat Exchange Rate [W]
HVAC,Average,Generator Air Mass Flow Rate [kg/s]
HVAC,Average,Generator Fuel Molar Flow Rate [kmol/s]
HVAC,Average,Generator Fuel Mass Flow Rate [kg/s]
HVAC,Average,Generator Engine Temperature [C]
HVAC,Average,Generator Coolant Inlet Temperature [C]
HVAC,Average,Generator Coolant Outlet Temperature [C]
HVAC,Sum,Generator Fuel HHV Basis Energy [J]
HVAC,Average,Generator Fuel HHV Basis Rate [W]
HVAC,Sum,Generator Fuel LHV Basis Energy [J]
HVAC,Average,Generator Fuel LHV Basis Rate [W]
HVAC,Average,Generator Fuel Compressor Electric Power [W]
HVAC,Sum,Generator Fuel Compressor Electric Energy [J]
HVAC,Average,Generator Fuel Compressor Skin Heat Loss Rate [W]
HVAC,Average,Generator Zone Sensible Heat Transfer Rate [W]
HVAC,Sum,Generator Zone Sensible Heat Transfer Energy [J]
HVAC,Average,Generator Zone Convection Heat Transfer Rate [W]
HVAC,Average,Generator Zone Radiation Heat Transfer Rate [W]
This report is the model prediction for the leaving
temperature of water used for heat recovery. If there is no
flow this is the modeled prediction for the mass of cooling
water in contact with the engine.
This is the energy used by the cogeneration device in terms
of higher heating value in joules. This is the output variable
is also put on the meter for natural gas.
This object is used to model small Fuel Cell (FC)
generators. IEA/ECBCS Annex 42 - see www.cogen-sim.net,
developed the FC model implemented in EnergyPlus. The model
can be used for two general types of fuel cells, solid oxide
fuel cells (SOFC) and proton exchange membrane fuel cells
(PEMFC). Warning! This is a complicated model, intended
primarily for research. Because fuel cells for cogeneration
(producing both heat and electricity) are not yet a mature
product for building systems, the input data for this model
are extremely difficult to obtain. However, the model is
designed to allow investigating the relative implications of a
broad array of subsystems and interactions with the
building.
There should be one Generator:FuelCell
object for each individual FC generator in the model. Multiple
fuel cell generators can be included in a given simulation.
Because there are a large number of inputs to the FC model and
numerous, somewhat separable subsystems within a fuel cell,
the EnergyPlus input objects have been organized into a number
of separate input objects. This object simply refers to the
names of all the other input objects that provide the input
details for individual subsystems within the fuel cell
cogeneration device. The following figure diagrams these
separate subsystems. (not shown is an optional stack cooler
with separate connections to heat recovery water loop and
surrounding zone air).
Fuel cell
subsystems.
Note that the FC model is formulated using the Lower
Heating Value (LHV) of the fuel, whereas most other parts of
EnergyPlus use the Higher Heating Value (HHV). LHV has
important advantages over HHV in the context of the quality of
heat recovered. While model coefficients for input performance
descriptions are to be based on LHV, energy consumption and
tariff calculations are also reported on HHV basis when using
this model.
This field contains the name of a
Generator:FuelCell:StackCooler input object. This is optional.
The presence of a stack cooler distinguishes between SOFC and
PEMFC with PEMFC operating at lower temperatures and requiring
a separate subsystem to maintain stack temperatures.
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell,
FCT SOFC, !- Name
FCT SOFC Power Module, !- Power Module Name
FCT SOFC Air Supply, !- Air Supply Name
FCT SOFC Fuel Supply, !- Fuel Supply Name
FCT SOFC Water Supply, !- Water Supply Name
FCT SOFC Auxiliary Heater, !- Auxiliary Heater Name
FCT SOFC Exhaust HX, !- Heat Exchanger Name
FCT SOFC Battery, !- Electrical Storage Name
FCT SOFC Inverter; !- Inverter Name
The following output variables are available for the fuel
cell model.
Output:Variable,*,Generator Produced Electric Power,hourly; !- HVAC Average [W]
Output:Variable,*,Generator Produced Electric Energy,hourly; !- HVAC Sum [J]
Output:Variable,*,Generator Produced Thermal Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Generator Produced Thermal Energy,hourly; !- HVAC Sum [J]
Output:Variable,*,Generator Fuel HHV Basis Energy,hourly; !- HVAC Sum [J]
Output:Variable,*,Generator Fuel HHV Basis Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Generator Fuel LHV Basis Energy,hourly; !- HVAC Sum [J]
Output:Variable,*,Generator Fuel Consumption Rate LHV Basis,hourly; !- HVAC Average [W]
Output:Variable,*,FuelCell Heat Loss Rate to Zone,hourly; !- HVAC Average [W]
Output:Variable,*,FuelCell Heat Loss Energy to Zone,hourly; !- HVAC Sum [J]
Output:Variable,*,FuelCell Convection Heat Loss Rate to Zone,hourly; !- HVAC Average [W]
Output:Variable,*,FuelCell Radiation Heat Loss Rate to Zone,hourly; !- HVAC Average [W]
This is the energy used by the cogeneration device in terms
of higher heating value in joules. This is the output variable
is also put on the meter for natural gas.
This is the rate of fuel energy use by the cogeneration
device in terms of lower heating value in watts.
Generator
Zone Sensible Heat Transfer Rate [W][LINK]
This variable provides the results for the total rate of
skin losses from the fuel cell to the surrounding zone.
Generator
Zone Sensible Heat Transfer Energy [J][LINK]
This variable provides the results for the total energy in
skin losses from the fuel cell to the surrounding zone.
Generator
Zone Convection Heat Transfer Rate [W][LINK]
This variable provides the results for the rate of skin
losses in the form of surface convection heat transfer from
the fuel cell to the surrounding zone.
Generator
Zone Radiation Heat Transfer Rate [W][LINK]
This variable provides the results for the rate of skin
losses in the form of radiation heat transfer from the fuel
cell to the surrounding zone.
Using the FC model with DisplayAdvancedReportVariables (see
Diagnostics object or use of operating system’s environment
variables) makes the following output variables available as
listed in the RDD file. There are a large number of output
variables that provide access to the inner workings of the
model and individual subsystems that are not likely to be
useful for the average user.
HVAC,Average,Generator Air Inlet Temperature [C]
HVAC,Average,Generator Power Module Entering Air Temperature [C]
HVAC,Average,Generator Air Molar Flow Rate [kmol/s]
HVAC,Average,Generator Power Module Entering Air Enthalpy [W]
HVAC,Average,Generator Blower Electric Power [W]
HVAC,Sum,Generator Blower Electric Energy [J]
HVAC,Average,Generator Blower Skin Heat Loss Rate [W]
HVAC,Average,Generator Fuel Inlet Temperature [C]
HVAC,Average,Generator Power Module Entering Fuel Temperature [C]
HVAC,Average,Generator Fuel Molar Flow Rate [kmol/s]
HVAC,Average,Generator Power Module Entering Fuel Enthalpy [W]
HVAC,Average,Generator Fuel Compressor Electric Power [W]
HVAC,Sum,Generator Fuel Compressor Electric Energy [J]
HVAC,Average,Generator Fuel Compressor Skin Heat Loss Rate [W]
HVAC,Average,Generator Fuel Reformer Water Inlet Temperature [C]
HVAC,Average,Generator Power Module Entering Reforming Water Temperature [C]
HVAC,Average,Generator Fuel Reformer Water Molar Flow Rate [kmol/s]
HVAC,Average,Generator Fuel Reformer Water Pump Electric Power [W]
HVAC,Sum,Generator Fuel Reformer Water Pump Electric Energy [J]
HVAC,Average,Generator Power Module Entering Reforming Water Enthalpy [W]
HVAC,Average,Generator Product Gas Temperature [C]
HVAC,Average,Generator Product Gas Enthalpy [W]
HVAC,Average,Generator Product Gas Molar Flow Rate [kmol/s]
HVAC,Average,Generator Product Gas Ar Molar Flow Rate [kmol/s]
HVAC,Average,Generator Product Gas CO2 Molar Flow Rate [kmol/s]
HVAC,Average,Generator Product Gas H2O Vapor Molar Flow Rate [kmol/s]
HVAC,Average,Generator Product Gas N2 Molar Flow Rate [kmol/s]
HVAC,Average,Generator Product Gas O2 Molar Flow Rate [kmol/s]
HVAC,Average,Generator Inverter Loss Power [W]
HVAC,Average,Generator Produced DC Electric Power [W]
HVAC,Average,Generator DC Power Efficiency [ ]
HVAC,Average,Generator Electric Storage Charge State [J]
HVAC,Average,Generator Produced DC Electric Power [W]
HVAC,Sum,Generator DC Storage Charging Energy [J]
HVAC,Average,Generator DC Storage Discharging Power [W]
HVAC,Sum,Generator DC Storage Discharging Energy [J]
HVAC,Average,Generator Ancillary AC Electric Power [W]
HVAC,Sum,Generator Ancillary AC Electric Energy [J]
HVAC,Average,Generator Zone Sensible Heat Transfer Rate [W]
HVAC,Sum,Generator Zone Sensible Heat Transfer Energy [J]
HVAC,Average,Generator Zone Convection Heat Transfer Rate [W]
HVAC,Average,Generator Zone Radiation Heat Transfer Rate [W]
HVAC,Sum, Generator Fuel Cell Model Iteration Count [ ]
HVAC,Sum,Generator Regula Falsi Iteration Count [ ]
This variable provides the temperature of air supplied to
the FC.
Generator
Power Module Entering Air Temperature [C][LINK]
This variable provides the temperature of the air supplied
to the power module after it has gone through the blower and
received any heat recovered from other subsystems.
This variable provides the results for \({\dot N_{air}}\), the flow rate
of air into the FC.
Generator
Power Module Entering Air Enthalpy [W][LINK]
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i}
\cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]}
\right)} _{air}}\), which is the enthalpy flow in the
air stream entering the power module relative to 25ºC.
This variable provides the results for \({\dot N_{fuel}}\), which is the
flow rate of fuel into the FC.
Generator
Power Module Entering Fuel Enthalpy [W][LINK]
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i}
\cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]}
\right)} _{fuel}}\), which is the enthalpy flow in the
fuel stream entering the power module relative to 25ºC.
Generator
Fuel Compressor Electric Power [W][LINK]
This variable provides the results for \({P_{comp - el}}\), which is the
electrical power used by the fuel supply compressor.
Generator
Fuel Compressor Electric Energy [J][LINK]
This variable provides the results for the energy used by
the fuel supply compressor. It is also added to the
appropriate meters.
Generator
Fuel Compressor Skin Heat Loss Rate [W][LINK]
This variable provides the results for the rate of energy
“lost” to the surroundings.
Generator
Fuel Reformer Water Inlet Temperature [C][LINK]
This variable provides the temperature of the water
supplied to the FC for reforming.
Generator
Power Module Entering Reforming Water Temperature [C][LINK]
This variable provides the temperature of the water
supplied to the power module after it has gone through the
pump.
Generator
Fuel Reformer Water Molar Flow Rate [kmol/s][LINK]
This variable provides the results for \({\dot N_{water}}\), which the
flow rate of reforming water into the FC.
Generator
Fuel Reformer Water Pump Electric Power [W][LINK]
This variable provides the results for \({P_{pump - el}}\), which is the
electrical power used by the water pump.
Generator
Fuel Reformer Water Pump Electric Energy [J][LINK]
This variable provides the results for energy used by the
water pump. It is also added to the appropriate meters.
Generator
Power Module Entering Reforming Water Enthalpy [W][LINK]
This variable provides the results for \({\dot H_{liq - water}}\) which is
the enthalpy flow of the water stream entering the power
module relative to 25ºC.
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i}
\cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]}
\right)} _{FCPM - cg}}\), which is the enthalpy flow in
the product gas stream leaving the power module relative to
25ºC.
Generator
Product Gas Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of all
the product gases leaving the fuel cell power module.
Generator
Product Gas Ar Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the
argon gas leaving the fuel cell power module.
Generator
Product Gas CO2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the
carbon dioxide gas leaving the fuel cell power module.
Generator
Product Gas H2O Vapor Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the
water gas leaving the fuel cell power module.
Generator
Product Gas N2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the
nitrogen gas leaving the fuel cell power module.
Generator
Product Gas O2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the
oxygen gas leaving the fuel cell power module.
This variable provides the results for state of charge of
the electrical storage device inside the fuel cell. Although
the units are Joules, this is a state variable and is reported
as an average rather than a sum.
This variable provides the results for \({P_{el,ancillaries - AC}}\),
which is the rate at which ancillary devices within the power
module use electricity supplied to the fuel cell by an
external source.
This variable provides the results for the energy used by
AC ancillaries. It is also added to the appropriate
meters.
Generator
Fuel Cell Model Iteration Count [ ][LINK]
This variable provides information on the numerical method
used to calculate the FC model. EnergyPlus uses a sequential
substitution iterative algorithm to solve the main heat
balance equation for the FC model. This output variable
indicates the number of iterations needed to converge.
This variable provides information on the numerical method
used to calculate product gas temperature as a function of the
product gas’s enthalpy. A Regula Falsi numerical method is
used to invert the Shomate equation for enthalpy as a function
of temperature. This output variable indicates the number of
iterations needed for the Regula Falsi method to converge.
Generator
Heat Recovery Exit Gas Temperature [C][LINK]
This is the temperature of the exiting gas for heat
recovery in C.
Generator
Heat Recovery Exit Gas H2O Vapor Fraction [][LINK]
This is the water vapor fraction in the exit gas.
Generator
Heat Recovery Water Condensate Molar Flow Rate [kmol/s][LINK]
This object is used to describe the core power module
subsystem of the FC. This includes the fuel cell stack, fuel
reformer, and whatever ancillary devices are included inside.
If the model has multiple FC generators that are of the exact
same type, then only one of these objects is needed and all
the Generator:FuelCell
can reference it. The model uses a number of curves to
describe operating performance. Input data for specific models
of FC are not yet available but will be produced by IEA Annex
42 and should be available in the future.
This field is used to choose between different modes of
inputting the electrical efficiency curve. There are two
options available for this Field: “Annex42” and “Normalized”.
The “Annex42” option indicates that the efficiency curves are
not normalized and are used for the single size and type of FC
product. The “Normalized” option indicates that the efficiency
curves are normalized (as is standard practice in EnergyPlus)
relative to a single rating point. In the Annex42 mode, the
curves directly represent efficiency as a function of fuel
use, but in the Normalized mode, the curves represent an
efficiency modification that is applied to the efficiency at
the rating point.
This field contains the name of a Curve:Quadratic
input object described elsewhere in the input file. The curve
is a function of the net DC electric power, \({P_{el}}\) (W), produced by the
power module and describes either the electrical efficiency or
the how the efficiency is modified depending on the mode
selected in the previous field. This quadratic curve is just
one part of the entire parametric relation used to describe
electrical efficiency \({\varepsilon
_{el}}\). For the Annex42 mode the full relation for
efficiency is,
where the Curve:Quadratic
input object named in this field serves to define the
quadratic portion in the first set of brackets. For the
Normalized mode the full relation for efficiency is,
where \({\varepsilon
_{nom}}\) is the nominal electrical efficiency at the
rating point \({P_{nom}}\)
which are described in the next two fields. The Normalized
mode may be more useful for a simulation study that needs to
vary the capacity of the FC.
This field is used for the “Normalized” efficiency curve
mode and provides the nominal efficiency \({\varepsilon _{nom}}\)
(dimensionless) at the rating point. This field can be left
blank if using the “Annex42” mode.
This field is used for the “Normalized” efficiency curve
mode and provides the nominal net DC electrical power produced
\({P_{nom}}\) (W) at the
rating point. This field can be left blank if using the
“Annex42” mode.
Field:
Number of Stops at Start of Simulation[LINK]
This field is used to describe the number of times the FC
has been cycled on and off prior to the start of the
simulation. FC products might degrade as a result of starting
and stopping the fuel cell stack, so the model includes terms
to model the degradation effects of cycling FC units on and
off. This is the initial value of the \({N_{stops}}\) term in the
efficiency relation above.
This field is used to describe the fixed value representing
the fractional performance degradation associated with each
start and stop cycle. This is the value of \(D\) in the efficiency relations
above. If there is no degradation from cycling, then D should
be 0.0.
Field:
Number of Run Hours at Beginning of Simulation[LINK]
This field is used to describe the amount of time the FC
has been operating prior to the start of the simulation. FC
products might degrade over time so the model includes terms
to model the degradation effects of FC run time. This is the
initial value of the integrated run time term \(\int\limits_0 {dt}\).
Field:
Accumulated Run Time Degradation Coefficient[LINK]
This field is used to describe the fixed value representing
the fractional performance degradation associated with the
total amount of run time. This is the value of \(L\) in the efficiency relations
above. If there is no degradation from run time, the L should
be 0.0.
Field:
Run Time Degradation Initiation Time Threshold[LINK]
This field is used to describe the time period for which
there is no degradation associated with the amount of run
time. This provides the ability to model a system that
initially operates without degradation for some period time
before it starts to degrade. This is the value of \({t_{threshold}}\) in the
efficiency relations above.
This field is used to describe the maximum allowable rate
at which the fuel cell can increase the level of power it
produces (W/s). This is a time derivative of the net DC
electrical power used to limit how fast the FC can ramp
up.
This field is used to describe the maximum allowable rate
at which the fuel cell can decrease the level of power it
produces (W/s). This is a time derivative of the net DC
electrical power used to limit how fast the FC can ramp
down.
This field is used to describe the amount of fuel (kmol)
used during the entire start up period. The fuel is the same
type as what is described in the Generator:FuelSupply
object elsewhere in the input file.
This field is used to describe the amount of fuel (kmol)
used during the entire shut down period. The fuel is the same
type as what is described in the Generator:FuelSupply
object elsewhere in the input file.
This field is used to describe the constant term, \(an{c_0}\), in a relation that
describes the AC electrical power used by ancillary equipment
located inside the power module, \({P_{el,ancillaries - AC}}\). The
model uses this relation,
This field is used to select the mode for how skin losses
are modeled. Skin losses are heat energy “lost” from the power
module and transferred to the surrounding thermal zone named
in the following field. There are three alpha options to
choose from: “ConstantRate”, “UAForProcessGasTemperature”, or
“QuadraticFunctionOfFuelRate.” Enter ConstantRate in this
field to model skin losses using a constant rate, e.g. 100
watts. Enter UAForProcessGasTemperature to model skin losses
using a “UA-Delta-T” calculation method with the temperature
difference determined by the power module’s product gas
temperature and the surrounding zone. Enter
QuadraticFunctionOfFuelRate to model skin losses as a function
of the rate of fuel use.
This field is used to describe the thermal zone that will
receive skin and other heat losses from the FC. This should be
the name of a Zone
input object declared elsewhere in the input file.
This field is used to describe the portion of skin losses
that are in the form of thermal radiation. This controls the
radiative/convective split for the energy transferred to the
zone by the FC.
This field is used to describe the constant rate of skin
losses (W). This field is used with the ConstantRate mode. It
can be left blank for other skin loss modes.
This field is used to describe the “UA” term (W/K). This
field is used with the UAForProcessGasTemperature mode. It can
be left blank for other skin loss modes. “UA” is the product
of the overall heat transfer coefficient “U” and the area
“A.”
This field is used to refer to the name of a quadratic
curve object defined elsewhere in the input file. The
quadratic curve should define skin heat loss rate as a
function of the fuel use rate (kmol/s) so that,
This field is used to describe the rate of dilution air
(kmol/sec) drawn into, or through, the power module. This air
stream may not be present in all FC products. It is used for
limiting skin and stack heat losses and for strategies that
mitigate potential safety issue were fuel gases to escape the
stack.
This field is used to describe the rate at which the fuel
cell stack adds energy to the dilution air stream. It is
entered as a constant heat rate (W).
This field is used to describe the air node where the
dilution air is drawn from. This would typically be the name
of the air node associated with the thermal zone where the FC
is located.
This field is used to describe the air node where the
dilution air is exhausted to. This could be the inlets to a
heat recovery ventilator or an exhaust node.
This field is used to describe the maximum operating point
for the net DC electric power, \({P_{el}}\) (W).
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:PowerModule,
FCT SOFC Power Module, !- Name
Annex42, !- Efficiency Curve Mode
FCT Power Curve, !- Efficiency Curve Name
0.354, !- Nominal Efficiency
3400, !- Nominal Electrical Power {W}
0, !- Number of Stops at Start of Simulation
0.0, !- Cycling Performance Degradation Coefficient
0, !- Number of Run Hours at Beginning of Simulation {hr}
0.0, !- Accumulated Run Time Degradation Coefficient
10000, !- Run Time Degradation Initiation Time Threshold {hr}
1.4, !- Power Up Transient Limit {W/s}
0.2, !- Power Down Transient Limit {W/s}
0.0, !- Start Up Time {s}
0.2, !- Start Up Fuel {kmol}
, !- Start Up Electricity Consumption {J}
0.0, !- Start Up Electricity Produced {J}
0.0, !- Shut Down Time {s}
0.2, !- Shut Down Fuel {kmol}
, !- Shut Down Electricity Consumption {J}
0.0, !- Ancilliary Electricity Constant Term
0.0, !- Ancilliary Electricity Linear Term
ConstantRate, !- Skin Loss Calculation Mode
ZN_1_FLR_1_SEC_5, !- Zone Name
0.6392, !- Skin Loss Radiative Fraction
729, !- Constant Skin Loss Rate {W}
0.0, !- Skin Loss U-Factor Times Area Term {W/K}
, !- Skin Loss Quadratic Curve Name
6.156E-3, !- Dilution Air Flow Rate {kmol/s}
2307, !- Stack Heat loss to Dilution Air {W}
SOFC Air HR Inlet, !- Dilution Inlet Air Node Name
SOFC Air HR Outlet, !- Dilution Outlet Air Node Name
3010, !- Minimum Operating Point {W}
3728; !- Maximum Operating Point {W}
This field contains the nominal stack operating temperature
for the PEMFC, \(T_{stack}^o\). This field and the
next five provide values for use in the empirical equation for
the rate of heat extracted from the fuel cell power module by
the stack cooler using the following relation
The stack cooler is assumed to have a closed water
circulation loop that is used to extract heat from the stack
and move it to a cogeneration heat exchanger and/or an air
cooler. This field is used to enter the flow rate of coolant
in this loop.
Field:
Stack Cooler U-Factor Times Area Value[LINK]
This is the heat transfer coefficient between the stack and
the coolant.
This field provides the value for an adjustment factor,
\({F_{s - cogen}}\), used in
the following relation for the cogeneration heat transfer
coefficient, \({\left( {UA}
\right)_{s - cogen}}\):
This field provides the value for \(\dot N_{s - cogen}^0\) in the
following relation for the cogeneration heat exchanger
convection coefficient, \({h_{s -
cogen}}\):
Field:
Stack Cogeneration Exchanger Nominal Heat Transfer
Coefficient[LINK]
This field provides the value for \(h_{s - cogen}^0\) in the relation
above for the cogeneration heat exchanger convection
coefficient, \({h_{s -
cogen}}\).
Field:
Stack Cogeneration Exchanger Nominal Heat Transfer Coefficient
Exponent[LINK]
This field provides the value for \({n_s}\) is the relation above for
the cogeneration heat exchanger convection coefficient, \({h_{s - cogen}}\).
This field and the next two are used to define coefficients
for the following relation for the power used by the
air-cooler’s fan to dump excess heat into the surrounding
zone:
This field is used to define the air node where the inlet
air stream is drawn from. If the FC uses outdoor air then the
node named here should be designated an outdoor air node. If
the FC draws air from its surroundings, then this would be the
name of the air node associated with the thermal zone
containing the FC.
This field contains the name of a Curve:Cubic
input object described elsewhere in the input file. The curve
provides the power used by the air blower (W) as a cubic
function of the rate of air supply (kmol/s).
This field describes the portion of blower electrical power
that is “lost” to the surroundings. The rest of the energy is
added to the air stream. A heat loss factor of 1.0 indicates
that all the heat is lost to the surroundings and no energy is
added to the air inlet stream.
This field describes how the model will calculate the air
supply rate. There are three options to choose from:
“AirRatiobyStoics”, “QuadraticFunctionofElectricPower”, and
“QuadraticFunctionofFuelRate.” The choice will determine how
the model calculates the rate of air and will depend on the
formulations used to develop model input data. The choices are
described in the next four fields.
This field describes the excess air ratio beyond
stoichiometric air supply. This field is only used if the air
supply rate calculation mode is AirRatiobyStoics. The total
air supply ratio will be the value entered here plus 1.0. Thus
if 1.0 is entered in this field, the total air flow will be
2.0 times what is needed to exactly match stoichiometry with
the fuel supply.
Field:
Air Rate Function of Electric Power Curve Name[LINK]
This field contains the name of a QuadraticCurve input
object described elsewhere in the input file. This field is
only used if the air supply rate calculation mode is
QuadraticFunctionofElectricPower. The quadratic curve named
here describes the first part of the relation below used to
calculate the rate of inlet air, \({\dot N_{air}}\) (kmol/s). It is
a quadratic function of the net DC electrical power, \({P_{el}}\) (W).
This field is used to describe the air temperature
coefficient, \({a_3}\), used
to adjust inlet air flow rate in the relations for inlet air
rate.
Field:
Air Rate Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Quadratic
input object described elsewhere in the input file. This field
is only used if the air supply rate calculation mode is
QuadraticFunctionofFuelRate. The quadratic curve named here
describes the first part of the relation used to calculate the
rate of inlet air, \({\dot
N_{air}}\) (kmol/s). It is a quadratic function of the
fuel flow rate, \({\dot
N_{fuel}}\).
This field is used to control how heat losses from three
other subsystems within the FC may or may not be recovered by
the air inlet. There are six possible choices for what to use
in this Field: “NoRecovery” “RecoverBurnerInverterStorage”
“RecoverAuxiliaryBurner” “RecoverInverterandStorage”
“RecoverInverter” and “RecoverElectricalStorage”. If heat is
recovered then that means that energy “losses” from those
subsystems are added to the inlet air and fed back into the FC
power module. The following table clarifies the meaning of the
six possible choices.
This field is used to choose between two different modes
for describing the make up of the inlet air stream. There are
two possible choices: “AmbientAir” or
“UserDefinedConstituents.” Choosing the AmbientAir mode will
automatically set the composition of air to be usual at:
77.28% nitrogen, 20.73% oxygen, 1.04% water, 0.92% argon, and
0.03% carbon dioxide. Choosing UserDefinedConstituents allows
the user to customize the make up the inlet air in the
remaining fields.
This field is used to describe the number of constituents
in the inlet air. This field is only used if the air supply
constituent mode is set to UserDefinedConstituents. The
maximum number is 5.
The remaining fields in this object are repeating pairs of
fields with one pair for each constituent and the same number
as described in the previous field. The pairs consist of the
name of the constituent followed by the molar fraction of that
constituent.
These fields describe the air stream constituents by name.
The name field for each pair must be filled with one of these
choices: “CarbonDioxide”, “Nitrogen,” “Oxygen,” “Water,” or
“Argon.”
These fields describe the molar fraction of the air stream
constituents. It is very important that the sum of the molar
fractions add up to 1.0.
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:AirSupply,
FCT SOFC Air Supply, !- Name
SOFC Air Inlet Node, !- Air Inlet Node Name
FCT Blower Power Curve, !- Blower Power Curve Name
1.0, !- Blower Heat Loss Factor
QuadraticFunctionofElectricPower, !- Air Supply Rate Calculation Mode
, !- Stoichiometric Ratio
FCT Excess Air Ratio Curve, !- Air Rate Function of Electric Power Curve Name
2.83507E-3, !- Air Rate Air Temperature Coefficient
, !- Air Rate Function of Fuel Rate Curve Name
NoRecovery, !- Air Intake Heat Recovery Mode
UserDefinedConstituents, !- Air Supply Constituent Mode
5, !- Number of UserDefined Constituents
Nitrogen, !- Constituent 1 Name
0.7728, !- Molar Fraction 1
Oxygen, !- Constituent 2 Name
0.2073, !- Molar Fraction 2
Water, !- Constituent 3 Name
0.0104, !- Molar Fraction 3
Argon, !- Constituent 4 Name
0.0092, !- Molar Fraction 4
CarbonDioxide, !- Constituent 5 Name
0.0003; !- Molar Fraction 5
This object is used to provide details of the water supply
subsystem. This water is used for steam reforming of the fuel
and is not the same as the water used for thermal heat
recovery.
Generator:FuelCell:WaterSupply,
A1, \field Name
\required-field
\reference FCWaterSupNames
A2, \field Reformer Water Flow Rate Function of Fuel Rate Curve Name
\type object-list
\object-list QuadraticCurves
A3, \field Reformer Water Pump Power Function of Fuel Rate Curve Name
\type object-list
\object-list QubicCurves
N1, \field Pump Heat Loss Factor
A4, \field Water Temperature Modeling Mode
\type choice
\key TemperatureFromAirNode
\key TemperatureFromWaterNode
\key TemperatureFromSchedule
\key MainsWaterTemperature
A5, \field Water Temperature Reference Node Name
A6; \field Water Temperature Schedule Name
\type object-list
\object-list ScheduleNames
This field contains a unique name for the fuel cell water
supply subsystem.
Field:
Reformer Water Flow Rate Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Quadratic
input object described elsewhere in the input file. The curve
provides the rate of water flow (kmol/sec) as a function of
fuel flow rate (kmol/sec).
If the unit does not use water for reforming then use a
“null” quadratic where all the coefficients are 0.0.
Field:
Reformer Water Pump Power Function of Fuel Rate Curve
Name[LINK]
This field contains the name of a Curve:Cubic
input object described elsewhere in the input file. The curve
provides the power used by the water pump (W) as a cubic
function of the rate of water supply (kmol/s).
This field describes the portion of pump electrical power
that is “lost” to the surroundings. The rest of the energy is
added to the water stream. A heat loss factor of 1.0 indicates
that all the heat is lost to the surroundings and no energy is
added to the water inlet stream.
This field describes how the model will determine the inlet
temperature of the water stream. There are four options to
choose from: “TemperatureFromAirNode,”
“TemperatureFromWaterNode,” “TemperatureFromSchedule,” and
“MainsWaterTemperature.” For the first two options, the
temperature of the water inlet is determined by the
temperature at the node named in the next field. For the third
option, the temperature is determined by the schedule in the
last field. Using the MainsWaterTemperature option requires
also defining a separate “Site:WaterMainsTemperature”
input object elsewhere in the input file.
Field:
Water Temperature Reference Node Name[LINK]
This field is used to define the node where the temperature
of the inlet water stream is obtained. This can be either an
air node or a water node.
This field is used to define the name of a schedule,
defined elsewhere in the input file, that will be used to
determine the temperature of the water inlet stream when using
the TemperatureFromSchedule mode.
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:WaterSupply,
FCT SOFC Water Supply, !- Name
Null Quadratic, !- Reformer Water Flow Rate Function of Fuel Rate Curve Name
Null Cubic, !- Reformer Water Pump Power Function of Fuel Rate Curve Name
0.0, !- Pump Heat Loss Factor
TemperatureFromAirNode, !- Water Temperature Modeling Mode
SOFC Air Inlet Node, !- Water Temperature Reference Node Name
; !- Water Temperature Schedule Name
Curve:Quadratic,
Null Quadratic, !- Name
0.0, !- Coefficient1 Constant
0.0, !- Coefficient2 x
0.0, !- Coefficient3 x**2
-1.0E+10, !- Minimum Value of x
1.0E+10; !- Maximum Value of x
Curve:Cubic,
Null Cubic, !- Name
0.0, !- Coefficient1 Constant
0.0, !- Coefficient2 x
0.0, !- Coefficient3 x**2
0.0, !- Coefficient4 x**3
-1.0E+10, !- Minimum Value of x
1.0E+10; !- Maximum Value of x
This object is intended for modeling an auxiliary heater,
however this portion of the model is not yet available in
EnergyPlus. An auxiliary heater may be present in fuel cell
products so that the unit can meet much higher thermal loads
than would be possible using only cogeneration. This portion
of the model will be added in the future once suitable
cogeneration control capabilities are also available. The
input fields are described for future reference but may
change. The program still requires one of these objects be
included even though the data are not yet used (so that
internal data structures can be allocated).
This field describes the excess air ratio beyond
stoichiometric air supply for the heater. The total air supply
ratio will be the value entered here plus 1.0. Thus if 1.0 is
entered in this field, the total air flow will be 2.0 times
what is needed to exactly match stoichiometry with the fuel
supply.
This field describes the constant term, \({x_0}\), used to model the
auxiliary burner’s ancillary devices such as fans and ignition
controls. The electrical power for ancillaries is calculated
using,
This field describes the “UA” term (W/K) for calculating
skin losses in the auxiliary burner. “UA” is the product of
the overall heat transfer coefficient “U” and the area “A.”
The skin heat losses are calculated using,
where, \({T_{aux - mix}}\)
is temperature of product gases leaving the auxiliary burner
and includes the mixing of the product gases from the fuel
cell power module. Thus, the input for UA should reflect this
choice of reference temperature rather than an exterior
surface temperature of the auxiliary burner.
This field describes the user’s choice for what happens to
the skin losses. There are two options: “SurroundingZone” and
“AirInletForFuelCell”. Entering SurroundingZone will direct
the model to put the “lost” energy into the surrounding
thermal Zone
named in the next field. Entering AirInletForFuelCell will
direct the model to put the “lost” energy into the air inlet
stream for the fuel cell to preheat that air.
This field is used to determine the zone that will receive
the skin losses. Enter the name of a Zone
declared elsewhere in the input file. This field is only used
if the “SurroundingZone” mode is used in the previous
field.
This field describes the user’s choice for how the capacity
of the auxiliary heater will be defined. There are two
options: “Watts” or “kmol/s.” Entering Watts will direct the
program to use the next two fields to determine the maximum
and minimum heating capacity. Entering kmol/s will direct the
program to use the last two fields to determine the maximum
and minimum heating capacities.
This field is used to describe the minimum heating capacity
of the auxiliary burner (W).
Field:
Maximum Heating Capacity in Kmol per Second[LINK]
This field is used to describe the maximum fuel use rate
for the auxiliary burner (kmol/s).
Field:
Minimum Heating Capacity in Kmol per Second[LINK]
This field is used to describe the minimum fuel use rate
for the auxiliary burner (kmol/s).
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:AuxiliaryHeater,
FCT SOFC Auxiliary Heater, !- Name
0.0, !- Excess Air Ratio
0.0, !- Ancilliary Power Constant Term
0.0, !- Ancilliary Power Linear Term
0.5, !- Skin Loss U-Factor Times Area Value
SurroundingZone, !- Skin Loss Destination
ZN_1_FLR_1_SEC_5, !- Zone Name to Receive Skin Losses
Watts, !- Heating Capacity Units
0.0, !- Maximum Heating Capacity in Watts
0.0, !- Minimum Heating Capacity in Watts
, !- Maximum Heating Capacity in Kmol per Second
; !- Minimum Heating Capacity in Kmol per Second
Generator:FuelCell:ExhaustGasToWaterHeatExchanger
This object is used to describe the exhaust gas heat
exchanger subsystem of the FC used to recovery thermal
energy.
This field contains the name of the node that connects the
heat exchanger’s outlet to the plant loop.
Field:
Heat Recovery Water Maximum Flow Rate[LINK]
This field describes the design maximum flow rate of the
heat recovery water (m3/s). The value should match
the design flow rate of the plant loop connected to the
FC.
This field is used to determine which node will receive the
exhaust air stream leaving the FC. This node will usually be
outside and not be referenced elsewhere. However, if the
exhaust stream is used in a heat recovery ventilator (as
described in section 11 of the Annex 42 specification) then
the node would be reference in the heat recovery ventilator
object.
This field is used to direct how EnergyPlus will calculate
heat exchanger performance. The Annex 42 model provides for
four different methods of modeling the heat exchanger. The
choices available for this field are: “FixedEffectiveness”
(method 1 in Annex 42 specification), “EmpiricalUAeff” (method
2), “FundementalUAeff” (method 3), or “Condensing” (method 4).
The remaining fields provide input data for the different
methods. The heat exchanger correlations are described
below.
This field describes constant heat exchanger effectiveness,
\({\varepsilon _{HX}}\). This
field is only used with the “FixedEffectiveness” mode, which
corresponds to “method 1” in the Annex 42 specification. For
this mode, the heat exchange between the exhaust gases and the
heat recovery water are calculated using,
where, \({\left( {\dot N{{\hat
c}_p}} \right)_{\min }}\) is the minimum value of \({\left( {\dot N{{\hat c}_p}}
\right)_{aux - mix}}\) and \({\left( {\dot N{{\hat c}_p}}
\right)_{water}}\).
This field describes the value of \(h{x_{s,0}}\) in the relation
below for effective UA. This field is used with the
“EmpiricalUAeff” mode, which corresponds to “method 2” in the
Annex 42 specification and with the “Condensing” mode, which
corresponds to “method 4”. This method uses the log mean
temperature difference (LMTD) approach to calculate the heat
exchange:
This field describes the value of \(h{x_{s,1}}\) in the relation
above for effective UA. This field is used with the
“EmpiricalUAeff” mode, which corresponds to “method 2” in the
Annex 42 specification and with the “Condensing” mode, which
corresponds to “method 4”.
This field describes the value of \(h{x_{s,2}}\) in the relation
above for effective UA. This field is used with the
“EmpiricalUAeff” mode, which corresponds to “method 2” in the
Annex 42 specification and with the “Condensing” mode, which
corresponds to “method 4”.
This field describes the value of \(h{x_{s,3}}\) in the relation
above for effective UA. This field is used with the
“EmpiricalUAeff” mode, which corresponds to “method 2” in the
Annex 42 specification and with the “Condensing” mode, which
corresponds to “method 4”.
This field describes the value of \(h{x_{s,4}}\) in the relation
above for effective UA. This field is used with the
“EmpiricalUAeff” mode, which corresponds to “method 2” in the
Annex 42 specification and with the “Condensing” mode, which
corresponds to “method 4”.
This field describes the value of \(h_{gas}^0\) in the relation
below. This field is only used with the “FundementalUAeff”
mode, which corresponds to “method 3” in the Annex 42
specification. For this mode, the heat exchange is calculated
using the LMTD method, but the effective UA is determined
using:
This field describes the value of \(\dot N_{gas}^0\) in the relation
above. This field is only used with the “FundementalUAeff”
mode, which corresponds to “method 3” in the Annex 42
specification.
This field describes the value of \(n\) in the relation above. This
field is only used with the “FundementalUAeff” mode, which
corresponds to “method 3” in the Annex 42 specification.
This field describes the value of \({A_{gas}}\) in the relation
above. This field is only used with the “FundementalUAeff”
mode, which corresponds to “method 3” in the Annex 42
specification.
This field describes the value of \(h_{water}^0\) in the relation
above. This field is only used with the “FundementalUAeff”
mode, which corresponds to “method 3” in the Annex 42
specification.
This field describes the value of \(\dot N_{water}^0\) in the
relation above. This field is only used with the
“FundementalUAeff” mode, which corresponds to “method 3” in
the Annex 42 specification.
This field describes the value of \(m\) in the relation above. This
field is only used with the “FundementalUAeff” mode, which
corresponds to “method 3” in the Annex 42 specification.
This field describes the value of \({A_{water}}\) in the relation
above. This field is only used with the “FundementalUAeff”
mode, which corresponds to “method 3” in the Annex 42
specification.
This field describes the value of \({F_{HX}}\) in the relation above.
This field is only used with the “FundementalUAeff” mode,
which corresponds to “method 3” in the Annex 42
specification.
This field describes the value of \(h{x_{l,1}}\) in the relation
below for the rate of condensation of water from the gas
stream, \({\dot N_{{H_2}O -
cond}}\). This field is only used with the “Condensing”
mode, which corresponds to “method 4” in the Annex 42
specification. This method uses a modified version of the LMTD
approach to calculate heat exchange:
This field describes the value of \(h{x_{l,2}}\) in the relation
above for the rate of condensation of water from the gas
stream, \({\dot N_{{H_2}O -
cond}}\). This field is only used with the “Condensing”
mode, which corresponds to “method 4” in the Annex 42
specification.
This field describes the value of \({T_{cond - threshold}}\) in the
relation above for the rate of condensation of water from the
gas stream, \({\dot N_{{H_2}O -
cond}}\). This field is only used with the “Condensing”
mode, which corresponds to “method 4” in the Annex 42
specification.
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:ExhaustGasToWaterHeatExchanger,
FCT SOFC Exhaust HX, !- Name
Small SOFC Heat Rec Inlet Node, !- Heat Recovery Water Inlet Node Name
Small SOFC Heat Rec Outlet Node, !- Heat Recovery Water Outlet Node Name
0.0004, !- Heat Recovery Water Maximum Flow Rate {m3/s}
SOFC Air Outlet Node, !- Exhaust Outlet Air Node Name
CONDENSING, !- Heat Exchanger Calculation Method
, !- Method 1 Heat Exchanger Effectiveness
83.1, !- Method 2 Parameter hxs0
4798, !- Method 2 Parameter hxs1
-138E+3, !- Method 2 Parameter hxs2
-353.8E+3, !- Method 2 Parameter hxs3
5.15E+8, !- Method 2 Parameter hxs4
, !- Method 3 h0Gas Coefficient
, !- Method 3 NdotGasRef Coefficient
, !- Method 3 n Coefficient
, !- Method 3 Gas Area
, !- Method 3 h0 Water Coefficient
, !- Method 3 N dot Water ref Coefficient
, !- Method 3 m Coefficient
, !- Method 3 Area Water Coefficient
, !- Method 3 F Adjustment Factor
-1.96E-4, !- Method 4 hxl1 Coefficient
3.1E-3, !- Method 4 hxl2 Coefficient
35.0; !- Method 4 Condensation Threshold {C}
This object is used to describe the electrical storage
subsystem for the FC. The electrical storage model is a very
simple “constrained bucket” model. Future developments made
add additional models for battery systems. Note that this
electrical storage is embedded within the FC device.
This field is used to direct how EnergyPlus will model
electrical storage. The only choice currently available is
“SimpleEfficiencyWithConstraints,” which should be entered in
this field. Future developments may expand the number of
models available for electrical storage.
This is the energetic efficiency of charging the storage
device. A value of 1.0 means that the storage device does not
lose any energy when charging. Note that the model can recover
the “lost” energy into the air supply intake.
This is the energetic efficiency of discharging the storage
device. A value of 1.0 means that the storage device does not
lose any energy when discharging. Note that the model can
recover the “lost” energy into the air supply intake.
This field describes the value for the initial state of
charge (J). This allows the storage device to contain some
amount of stored electricity at the beginning of the
simulation period.
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:ElectricalStorage,
FCT SOFC Battery, !- Name
SimpleEfficiencyWithConstraints, !- Choice of Model
1.0, !- Nominal Charging Energetic Efficiency
1.0, !- Nominal Discharging Energetic Efficiency
0, !- Simple Maximum Capacity {J}
0, !- Simple Maximum Power Draw {W}
0, !- Simple Maximum Power Store {W}
0; !- Initial Charge State {J}
This object is used to describe the power condition unit
subsystem of the FC. This object models an inverter system
contained within a fuel cell system that converts from direct
current (DC) to alternating current (AC).
This field describes the value for inverter efficiency when
using the Constant mode.
Field:
Efficiency Function of DC Power Curve Name[LINK]
This field names a Curve:Quadratic
object defined elsewhere in the input file. The curve
determines inverter efficiency as a function of the DC power
entering the inverter as follows:
An example input data file (IDF) entry for this object is
provided below:
Generator:FuelCell:Inverter,
FCT SOFC Inverter, !- Name
Quadratic, !- Inverter Efficiency Calculation Mode
, !- Inverter Efficiency
FCT Inverter Quadratic; !- Efficiency Function of DC Power Curve Name
Curve:Quadratic,
FCT Inverter Quadratic, !- Name
0.560717, !- Coefficient1 Constant
1.24019E-4, !- Coefficient2 x
-2.01648E-8, !- Coefficient3 x**2
-1.0E+10, !- Minimum Value of x
1.0E+10; !- Maximum Value of x
This object is used to define details of the fuel supply
for certain generators. This object allows the user to
describe a wide array of possible fuel mixtures. The program
contains data and internal methods to calculate the properties
of the various mixtures of gaseous fuels. The program will
calculate the Lower Heating Value (LHV), Higher Heating Value
(HHV), and molecular weight for the fuel mixture. The fuel
properties are then use by both fuel cell and Micro CHP
models. Results of the gas phase thermochemistry modeling are
also reported in the EIO file.
In addition to gaseous mixtures, the Micro CHP model is
able to use generic liquid fuels and this object is used to
describe the properties.
Note that the fuel consumption metering is currently
handled by the Natural Gas meter. So no matter what fuel
mixture is defined in this object, the aggregated reports from
EnergyPlus meters for (natural) Gas will include the fuel used
for the generator (with the Joule content based on HHV).
This field describes how the model will determine the
temperature of the fuel. There are two options for this field
to choose from: “TemperatureFromAirNode” and “Scheduled.” If
this field contains TemperatureFromAirNode then the fuel is
modeled as having the same temperature as the air node that is
named in the next field. If this field contains Scheduled then
the fuel is modeled as having the temperature described in a
schedule defined elsewhere in the input file.
This field contains the name of the air node used to obtain
the inlet temperature of the fuel. This field is only used if
the Fuel Temperature Modeling Mode is set to
TemperatureFromAirNode.
This field contains the name of a temperature schedule
defined elsewhere in the input file. This field is only used
if the Fuel Temperature Modeling Mode is set to Scheduled. The
temperature of the fuel inlet will be obtained from the
schedule.
Field:
Compressor Power Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Cubic
input object described elsewhere in the input file. The curve
provides the electrical power used by the fuel compressor (W)
as a cubic function of the rate of fuel supply (kmol/s).
This field describes the portion of the compressor
electrical power that is “lost” to the surroundings. The rest
of the energy is added to the fuel stream. A heat loss factor
of 1.0 indicates that all the heat is lost to the surroundings
and no energy is added to the fuel inlet stream.
For fuel type “LiquidGeneric,” this field is used to enter
the molecular weight of the fuel in units of g/mol.
Field:
Liquid Generic Fuel CO2 Emission Factor[LINK]
This field is not used. This part of the Annex 42 model was
not implemented in EnergyPlus; see the FuelFactors
object.
Field:
Number of Constituents in Gaseous Constituent Fuel Supply[LINK]
This field is used to describe the number of constituents
in the inlet fuel supply. The maximum number of different
types of constituents is currently set to 12.
The remaining fields in this object are repeating pairs of
fields with one pair for each constituent and the same number
as described in the previous field. The field set pairs
consist of the name of the constituent followed by the molar
fraction of that constituent.
These fields describe the fuel stream constituents by name.
The name field for each pair must be filled with one of these
14 choices: “CarbonDioxide”, “Nitrogen”, “Oxygen”, “Water”,
“Argon”, “Hydrogen”, “Methane”, “Ethane”, “Propane”, “Butane”,
“Pentane”, “Hexane”, “Methanol”, and “Ethanol”. No other fuel
constituents can currently be modeled. The properties of the
constituents are already contained inside the program as
provided in the Annex 42 model specification.
In addition to the following output variables, the
resulting fuel heating values are also reported to the eio
file.
HVAC,Average,Generator Fuel Compressor Electric Power [W]
HVAC,Sum,Generator Fuel Compressor Electric Energy [J]
HVAC,Average,Generator Fuel Compressor Skin Heat Loss Rate [W]
Generator
Fuel Compressor Electric Power [W][LINK]
This is the rate of energy use by the gas compressor, if
any, that provides fuel at a higher pressure.
Generator
Fuel Compressor Electric Energy [J][LINK]
This is the energy used by the gas compressor, if any, that
provides fuel at a higher pressure.
Generator
Fuel Compressor Skin Heat Loss Rate [W][LINK]
Convective heat gains to zone from gas compressor, if any,
that provides fuel at a higher pressure.
EnergyPlus offers different options for predicting the
electricity produced by solar electric photovoltaic (PV)
panels. The three different options are “Simple”, “Equivalent
One-Diode” and “Sandia” and the choice will determine the
mathematical models used to determine energy production. The
first allows the user to input an arbitrary efficiency. The
other two models use empirical relationships to predict PV
operating performance based on many environmental variables
such as cell temperature. The PV models can be used with
either normal PV modules or as part of a hybrid
photovoltaic/thermal (PVT) flat plat collector.
The generator is connected to an Electric Load Center. The
PV models refer to surface input objects defined elsewhere in
the input file. This object describes an array that is
“attached” to a surface object in order to describe its
orientation and to access results of the solar insolation
calculations. These can be either Heat Transfer or Shading
objects (see Surfaces). This will define the orientation of
the solar panel for the detailed models and also the area for
the simple model. The exposure of that surface to incident
solar radiation is calculated using the full set of models in
EnergyPlus that are used to account for solar thermal loads
arising from building windows and walls. Therefore the
incident solar radiation is calculated to include the effects
of shading and reflections from other surfaces declared in the
input file. In addition to the output variables associated
with PV models, there are numerous related output variables
available for the surfaces including: ‘Surface Outside Face
Sunlit Area’, ‘Surface Outside Face Sunlit Fraction’, ‘Surface
Outside Face Incident Solar Radiation Rate per Area’, ‘Surface
Outside Face Incident Beam Solar Radiation Rate per Area’,
‘Surface Outside Face Incident Sky Diffuse Solar Radiation
Rate per Area’, ‘Surface Outside Face Incident Ground Diffuse
Solar Radiation Rate per Area’, ‘Surface Outside Face Beam
Solar Incident Angle Cosine Value’, ‘Surface Outside Face
Incident Sky Diffuse Ground Reflected Solar Radiation Rate per
Area’, ‘Surface Outside Face Incident Sky Diffuse Surface
Reflected Solar Radiation Rate per Area’, ‘Surface Outside
Face Incident Beam To Beam Reflected From Surfaces Solar
Radiation Rate per Area’, ‘Surface Outside Face Incident Beam
To Diffuse Surface Reflected Solar Radiation Rate per Area’,
and ‘Surface Outside Face Incident Beam To Diffuse Ground
Reflected Solar Radiation Rate per Area.’ Note that it is
possible to define a PV array area that doesn’t conform to the
surface area (i.e. model a PV array area that is larger or
smaller than what is available on the surface) so it is the
users responsibility to not over-specify area when determining
how many modules will fit onto a surface. However this type of
input is allowed.
EnergyPlus does not include models for ancillary equipment
for a PV array including charge controllers or power-point
trackers. The operation of the entire electrical system that
must go along with a PV array is not currently modeled in
EnergyPlus and is therefore assumed to operate in ideal ways.
The PV production models do not resolve voltage and current,
only power (and energy). Electricity production is metered
based on the output of the inverter. Output results are
available before and after the inverter. One assumption is
that the array is assumed to be always operating at the
maximum power point. Energy production is based on the
assumption that the quasi-steady power prediction is constant
and continuous over the simulation timestep.
For a variety of reasons, actual installations of
photovoltaics are often observed to exhibit system-level
problems that significantly reduce electricity production.
Therefore this modeling should be considered a method of
bracketing the upper end of electricity production rather than
an accurate prediction of what the panels will produce. Also
note that the model predictions are closely related to the
solar radiation data (typically of of TMY2 origin) in the
EnergyPlus weather file, that the solar data in these is
usually from a model rather than direct measurements, and that
solar resources encountered by a real installation in a given
year are likely to differ from the weather data file.
This object is used to describe an array of PV modules and
how they are to be modeled. A series of different PV arrays
can be connected to a single electric load center (and
inverter) by listing them all in an
ElectricLoadCenter:Generator object.
The PV model allows for different ways of integrating with
other EnergyPlus heat transfer surfaces and models and
calculating cell temperature. For Building
Integrated PV (BIPV), the “Integrated” options allow for the
PV modeling to be coupled to the surface heat transfer models
elsewhere in EnergyPlus. The user must select one of these
options for this field:
Decoupled. The cell temperature of modules
in the array is computed based on a energy balance relative to
NOCT conditions. The input fields for Module Heat Capacity and
Module Heat Loss Coefficient are ignored.
DecoupledUllebergDynamic the cell
temperature is calculated based on a dynamic model developed
by Ulleberg. The input fields for Module Heat Capacity and
Module Heat Loss Coefficient are required.
IntegratedSurfaceOutsideFace The cell
temperature is obtained from the outside face of the
Surface:Heat Transfer named in the previous field. Energy
exported by the module is removed from the heat transfer
surface (at the position determined by the associated Construction
with Internal Source). The input fields for Module Heat
Capacity and Module Heat Loss Coefficient are ignored.
IntegratedTranspiredCollector The cell
temperature is obtained from the collector surface temperature
in the unglazed transpired collector model. Energy exported by
the module is removed from the collector surface. The input
fields for Module Heat Capacity and Module Heat Loss
Coefficient are ignored.
IntegratedExteriorVentedCavity The cell
temperature is obtained from the exterior baffle temperature
in the naturally ventilated exterior cavity model. Energy
exported by the module is removed from the exterior baffle
surface. The input fields for Module Heat Capacity and Module
Heat Loss Coefficient are ignored.
PhotovoltaicThermalSolarCollector The cell
temperature is obtained from the photovoltaic/thermal solar
collector model. If the PV layer is inside the collector, then
the incident solar is modified by the photovoltaic/thermal
solar collector model.
This field is the number of series-wired strings of PV
modules that are in parallel to form the PV array. The product
of this field and the next field should equal the total number
of modules in the array.
This field is the number of modules wired in series (on
each string) to form the PV array. The product of this field
and the previous field should equal the total number of
modules in the array.
Using the Generator:PV:Simple object makes a number of
output variables available.\
HVAC,Average,Generator Produced DC Electric Power [W]
HVAC,Sum,Generator Produced DC Electric Energy [J]
HVAC,Average,Generator PV Cell Temperature [C]
HVAC,Average,Generator PV Short Circuit Current [A]
HVAC,Average,Generator PV Open Circuit Voltage [V]
HVAC,Average,Generator PV Array Efficiency []
The PhotovoltaicPerformance:Simple
object describes a simple model of photovoltaics that may be
useful for early phase design analysis. In this model the user
has direct access to the efficiency with which surfaces
convert incident solar radiation to electricity and need not
specify arrays of specific modules. The full geometric model
for solar radiation is used, including shading and
reflections, to determine the incident solar resource. This
model is intended to be useful for design purposes to quickly
get an idea of the levels for annual production and peak
power. The model can also accept arbitrary conversion
efficiencies and does not require actual production units be
tested to obtain performance coefficients.
This field is the name of the PV array. The name is only
used as an identifier. Multiple instances need have unique
names.
Field:
Fraction of Surface Area with Active Solar Cells[LINK]
This field is the user defined fraction for the area of
surface named in the parent PV object that will have active PV
cells on it. The area actually covered with solar cells will
be the net area of the surface (gross area less any
subsurfaces like windows) times the fraction entered here.
This fraction includes the difference between PV module area
and active cells within it and any losses for how closely
packed modules can be arranged on surface. The value should be
between 0.0 and 1.0.
This field specifies how the PV array efficiency values are
input. There are two choices, Fixed and
Scheduled. If this field is set to ‘Fixed’
then the PV array always has the efficiency value specified in
the next field. If this field is set to ‘Scheduled’ then the
efficiency is determined by a user defined schedule named in
the second field to follow.
This field specifies the efficiency with which solar
incident energy is converted to electricity. Efficiency =
(electrical power generated [W])/(power of incident solar[W]).
These efficiency values are dimensionless and should be
between 0.0 and 1.0.
This field should be set to the name of schedule defined
elsewhere in the input file. This schedule should specify
dimensionless efficiency values between 0.0 and 1.0. This
could be used for example to vary the efficiency to match
results computed with more detailed models.
An example idf instance of this object follows:
PhotovoltaicPerformance:Simple,
Simple PV Flat, !- Name
0.1044 , !- Fraction of Surface area that has active solar cells
FIXED , !- Conversion efficiency input mode
0.12 , !- Value for cell efficiency if fixed
; !- Name of Schedule that Defines Efficiency
This object describes the performance characteristics of
Photovoltaic (PV) modules to be modeled using an equivalent
one-diode circuit. This model is also known at the 4- or
5-parameter TRNSYS model for photovoltaics.
The following table shows several sample PV array types
with their input values.
Photovoltaics Array Types with Values
–
Short Circuit Current
Open Circuit Voltage
Voltage at Maximum Power
Current at Maximum Power
Temperature Coefficient of Short
Circuit Current
Temperature Coefficient of Open
Circuit Voltage
Number of Cells in Series per
Module
Cell Temperature at NOCT
Conditions
Module Area
Units:
[A]
[V]
[V]
[A]
[A/K]
[V/K]
[-]
[K]
[ m2]
ASE 300- DFG/50
6.2
60
50.5
5.6
0.001
-0.0038
216
318
2.43
BPsolar 275
4.75
21.4
17
4.45
0.00065
-0.08
36
320
0.63
BPsolar 3160
4.8
44.2
35.1
4.55
0.00065
-0.16
72
320
1.26
BPsolar 380
4.8
22.1
17.6
4.55
0.00065
-0.08
36
320
0.65
BPsolar 4160
4.9
44.2
35.4
4.52
0.00065
-0.16
72
320
1.26
BPsolar 5170
5
44.2
36
4.72
0.00065
-0.16
72
320
1.26
BPsolar 585
5
22.1
18
4.72
0.00065
-0.08
36
320
0.65
Shell SM110-12
6.9
21.7
17.5
6.3
0.0028
-0.076
36
318
0.86856
Shell SM110-24
3.45
43.5
35
3.15
0.0014
-0.152
72
318
0.86856
Shell SP70
4.7
21.4
16.5
4.25
0.002
-0.076
36
318
0.6324
Shell SP75
4.8
21.7
17
4.4
0.002
-0.076
36
318
0.6324
Shell SP140
4.7
42.8
33
4.25
0.002
-0.152
72
318
1. 320308
Shell SP150
4.8
43.4
34
4.4
0.002
-0.152
72
318
1. 320308
Shell S70
4.5
21.2
17
4
0.002
-0.076
36
317
0.7076
Shell S75
4.7
21.6
17.6
4.2
0.002
-0.076
36
317
0.7076
Shell S105
4.5
31.8
25.5
3.9
0.002
-0.115
54
317
1.037
Shell S115
4.7
32.8
26.8
4.2
0.002
-0.115
54
317
1.037
Shell ST40
2.68
23.3
16.6
2.41
0.00035
-0.1
16
320
0. 424104
UniSolar PVL-64
4.8
23.8
16.5
3.88
0.00065
-0.1
40
323
0.65
UniSolar PVL-128
4.8
47.6
33
3.88
0.00065
-0.2
80
323
1.25
Where:
Shunt Resistance: the value of shunt resistance is finite
only if the PV Module being modeled is a thin film variety.
For all crystaline silicon modules the value is essentially
infinite
This field is used to describe the type of technology used
in the PV module. There are two options available,
CrystallineSilicon and
AmorphousSilicon. The choice affects the
modeling.
This field is an integer representing the number of
individual cells wired in series to make up a single module.
The typical number for a 12V crystalline silicon PV module is
36.
This field indicates the transmittance-absorptance product
at normal incidence angles for the PV modules. If the
product is positive, that value will be used for all angles of
incidence. If the value specified is negative, then the
magnitude of the given value will be used for normal incidence
and the IAM modifier correlation will be used for all other
angles.
This field is the shunt (parallel) resistance (in ) in the
single diode electrical model of the PV. The shunt resistance
is effectively infinite for crystalline silicon based PV
modules and is finite for thin film and exotic metal
modules.
This field is the heat loss coefficient (in
W/m2.K) for the array. The heat loss coefficient is
dependent upon measures taken to actively or passively promote
airflow over the array surface. The heat loss coefficient
value is used only if the Integration and Cell Temperature
Mode is set to “Decoupled Ulleberg Dynamic.”
This field is the heat capacity (in J/m2.K) of
the modules in the array. It describes the module’s ability to
store incident solar radiation internally. Such energy storage
is manifested as a temperature increase in the modules that is
considered to be undesirable. The total heat capacity value is
used only if the Integration and Cell Temperature Mode is set
to “Decoupled Ulleberg Dynamic.”
An IDF example:
PhotovoltaicPerformance:EquivalentOne-Diode,
Siemens, ! Name
CrystallineSilicon, !cell Type
36, !cells in series [-]
1.0, !module area [m2]
0.9, !tau alpha product at normal incidence [-]
1.12, !electron bandgap [eV]
1000000, !shunt resistance [ohms]
6.5, !short circuit current at reference conditions [A/K]
21.6, !open circuit voltage at reference conditions [V/K]
25, !temperature at reference conditions [C]
1000, !radiation at reference conditions [W/m2]
5.9, !current at max power
17, !voltage at max power
0.002, !temperature coefficient of short circuit current
-0.079, !temperature coefficient of open circuit voltage
20, !ambient temperature at NOCT [C]
45, !cell temperature at NOCT [C]
800, !radiation at NOCT [W/m2]
30, !heat loss coefficient [W/m2.K]
50000; !total heat capacity (only used in TC mode 1)
This ‘PhotovoltaicPerformance:Sandia’ object describes the
performance of a single type of module. The model used with
this object for predicting the electricity generated by
photovoltaics is referred to as the Sandia model. This model
is based on work done at Sandia National Lab, Albuquerque, NM
by David King – with the help of many others.
This object describes performance input data needed for
specific makes and models of production PV panels using the
empirical coefficients assembled by Sandia National
Laboratory. There are a large number of empirical coefficients
required to use the Sandia model. These data are obtained
after extensive measurements and data reduction. This testing
has been performed for some types of production panels and
Sandia publishes a database of module and array performance
parameters on the web at www.sandia.gov/pv. The entries in the
database as of January 15, 2004 were converted to idf segments
and are included with the EnergyPlus release in the library
file SandiaPVData.imf. There are more than hundred different
module types included in the library and identified by the
manufacturer’s model names listed at the beginning of the file
SandiaPVData.imf. This data library file is arranged for use
with EpMacro but the user can also copy .idf segments directly
from the macro data set.
The Sandia model itself can aggregate multiple PV modules.
Therefore, an instance of a ‘PhotovoltaicPerformance:Sandia’
object could actually represent an array of modules as well as
the more usual single module. These can be can be thought of
as simple larger modules and used by Generator:PV:Sandia
objects in the usual manner.
The many empirical coefficients for the model are listed
below and are described in more more detail in the EnergyPlus
engineering documentation EngineeringDoc.pdf.
The field descriptions below focus on providing the
parameter’s variable name as identified in the Sandia
database. See the the EngineeringDoc.pdf for details on how
the input fields are used in the correlations. The user
generally would not need to worry about the details of the
fields since he/she is not likely to generate the data on
their own.
“Vmpo” in Sandia Database. Voltage at maximum powerpoint is
a a basic parameter typically provided by manufacturers a t
Standard Report Conditions. (Volts)
When using EpMacro with an typical installation of
EnergyPlus, the above entry can be included in an input file
by adding the following two lines to an input macro file
(*.imf).
A wind turbine is a component that converts the kinetic
energy of the surrounding airstream into electricity. This
model is intended to calculate the electrical power that a
wind turbine system produces. The performance of wind turbine
systems is dependent on the local environmental conditions
such as wind speed and density of air at the height of the
systems. An analysis of these conditions is necessary to
accurately estimate power output. The model obtains the
weather information from the weather data file in EnergyPlus
and then determines the wind speed and air density at the
specific height of the system. It also requires the user to
input the annual average wind speed measured at the local site
and the height of the measurement so that it factors in
differences between the weather file wind data and the local
wind data.
The model employs the general kinetic energy equation to
calculate the performance characteristics of the horizontal
axis wind turbine (HAWT) systems. It provides a simple
approximation algorithm when the power coefficient, Cp, is
available which represents the efficiency of the wind turbine
in the wind power extraction from the ambient air stream. It
also allows the user to input experimental constants so that
the power coefficient can precisely be determined according to
the characteristic of the airfoil of the system. As for the
vertical axis wind turbine (VAWT) systems, it employs the
general mathematical equations for straight-bladed
Darrieus-type VAWT systems, which are common to VAWT systems.
Various types of VAWT systems such as the Savonius-type and
the curved-blade (or Egg-beater) type may be simulated with
this same model.
It includes two different types of dynamic power control:
FixedSpeedFixedPitch (FSFP) and VariableSpeedFixedPitch
(VSFP). Currently, it does not include an algorithm for
modeling pitch control such as FixedSpeedVariablePitch (FSVP)
and VariableSpeedVariablePitch (VSVP). If the control type of
the wind turbine is either FSVP or VSVP, the control type of
VSFP will be assumed. In addition, constant power generation
is assumed when the ambient wind speed is between the rated
wind speed and the cut out wind speed, if the user specifies
one of the last three options. The model also has the ability
to account for transient losses associate with the power
produced during dynamic control by a user-specified
fraction.
The model does not include detailed algorithms for
generators and inverters due to concerns for computational
convergence, time, and usability. Instead, all conversion
losses of these subsystems are included by applying a
user-supplied total system efficiency to the maximum power
extraction of the wind turbine. The field of the total system
efficiency must be specified by the user.
The name of the schedule (ref: Schedule) that denotes
whether the wind turbine system can run during a given time
period. A schedule value greater than 0 (usually 1 is used)
indicates that the unit can be on during the time period. A
value less than or equal to 0 (usually 0 is used) denotes that
the unit is off and will not operate for the time period. If
this field is blank, the schedule has values of 1 for all time
periods.
This field is the type of axis of the wind turbine. The
user specifies either a horizontal axis wind turbine or a
vertical axis wind turbine. Each type of wind turbine employs
a different algorithm for the calculation of the electrical
power output of the wind turbine. The default value is
HorizontalAxisWindTurbine.
This field is the type of rotor control for the wind
turbine. This protects the system against the overloading for
a system with no speed or pitch control and also to maximize
the energy yield for the system. Four different control types
are classified in the literature: FixedSpeedFixedPitch (FSFP),
FixedSpeedVariablePitch (FSVP), VariableSpeedFixedPitch
(VSFP), and VariableSpeedVariablePitch (VSVP). Currently, FSFP
and VSFP types can be modeled in EnergyPlus. The other two
types will be modeled as VSFP. If the first FSFP control type
is chosen, the model assumes the maximum power at a fixed
rotor speed when the power output predicted is greater than
the maximum until the rotor speed reaches the maximum wind
speed (see next field). If one of the last three control
options is chosen, the model assumes that the system produces
a constant power at the rated wind speed when the wind speed
is between the rated wind speed and cut-out wind speed. The
default value is VariableSpeedFixedPitch (VSFP).
This field is the maximum rotational speed of the rotor at
the rated power of the wind turbine in rev/min (revolution per
minute). It is used to determine the tip speed ratio of the
rotor and relative flow velocity incident on a single blade of
the VAWT systems.
This field is the diameter of the rotor in meters. Note
that this field is not the height of the blade, but the
diameter of the perpendicular circle from the vertical pole in
the VAWT systems. It determines the swept area of the rotor of
the HAWT systems and the chordal velocity of the VAWT
systems.
This field is the height of the hub of the HAWT system, or
of the pole of the VAWT system in meters. It is necessary to
estimate local air density and the wind speed at this
particular height where the wind turbine system is
installed.
This field is the number of blades of the wind turbine. The
azimuth angle of the rotor of the VAWT system is determined by
dividing 360 degree by this field so that the model determines
the chordal velocity component and the normal velocity
component of the system. The default value is 3.
This field is the nominal power output of the wind turbine
system at the rated wind speed in Watts. Note that the user
should input the maximum power of the system with no control,
i.e., FSFP control type, can physically produce.
Manufacturers’ data also indicates it as “peak power” or
“rated capacity”. If the local wind speed is greater than the
rated wind speed, the model assumes constant power output of
this field.
This field is the wind speed that the wind turbine system
indicates the peak in the power curve in m/s. The system
produces the maximum power at this speed and the speed of the
rotor is managed based on this wind speed.
This field is the lowest wind speed where the wind turbine
system can be operated in m/s. No power generation is achieved
as long as the ambient wind speed is lower than this
speed.
This field is the greatest wind speed in m/s. When the wind
speed exceeds this value, the wind turbine system needs to be
stopped because of inefficiencies in the system. All systems
that have either pitch or speed control must be stopped when
the ambient wind speed exceeds this speed. Note that the user
should input a wind speed above which physical damage to the
system might be caused in the case of a FSFP system. It
appears as “extreme/survival/design wind speed” in the
literature. The system will be turned off when the ambient
wind speed is over this speed.
This field is the overall system efficiency of the wind
turbine system. It includes all the conversion losses as well
as transient losses during the dynamic control when the
ambient wind speed is between the rated wind speed and cut-out
wind speed (see previous fields). The user also has the
ability to specify delivery losses from the system to the
local area. If the user does not enter a fraction, the model
assumes the default value of 0.835. Note that the fraction
must be between zero and one.
This field is the maximum tip speed ratio between the rotor
velocity and ambient wind velocity. The rotor speed varies
with this ratio to maximize the power output when the rotor
control types are variable speed ones. This field allows the
user to adjust the power output from the particular system or
to find the optimal tip speed ratio of the system. Optimal tip
speed ratio is dependent on the number of blades. It is
typically about 6, 5, and 3 for two-bladed, three-bladed, and
four-bladed rotor, respectively. For the vertical axis wind
turbine, it is smaller than horizontal axis wind turbine, and
varies with the chord area. The default and maximum values are
5.0 and 12.0.
This field is the maximum fraction of power extraction from
ambient wind. If the user inputs this field, the simple
approximation model is assumed. The model simply employs the
value of this field into the general kinetic energy equation,
so that the power output is obtained. The user can obtain this
field with a simple calculation from the power curve published
in almost all manufacturers’ specifications by using the
kinetic energy equation as:
This field is the local annual average wind speed that
represents a representative wind profile at the location of
the system in m/s. It is used to factor the difference in wind
speed between the weather file wind data and the locally
measured wind data so that the model minimizes uncertainties
caused by improper wind data at the particular location.
Considerable differences between the weather file wind data
and the local wind data typically appear. The user thus needs
to enter this field in order to obtain accurate local wind
data. The model internally determines a multiplier and it is
multiplied by the weather file wind data adjusted at the
height of the system. If this field is not entered, then the
model will use the wind speed from the design day or weather
file information with only adjustment at the height of the
rotor.
This field is the height that the local wind speed is
measured in meters. The annual average wind speed (see
previous field) input by the user is internally recalculated
by existing EnergyPlus functions at the height of the local
station. This modified wind speed is then factored and applied
to the weather file wind data. If the annual local average
wind speed is not entered, this field is then assumed as zero.
The minimum and default values are zero and 50 meters.
This field is the blade chord area of a single blade of
VAWT system in m2. It is necessary to determine the net
tangential and normal forces of a single blade.
This field is the blade drag coefficient for a specific
blade. It is for determining the tangential and normal force
coefficients with the blade lift coefficient (see next field)
so that the model can calculate the power output from the
system. The user should be able to obtain this parameter for a
specific blade from the manufacturers’ data. This field is
only valid for VAWT systems.
This field is the blade lift coefficient for a specific
blade. It is for determining the tangential and normal force
coefficients with the blade drag coefficient (see previous
field) so that the model can calculate the power output from
the system. The user should also be able to obtain it for a
specific blade from the manufacturers’ data. This field is
only valid for VAWT systems.
These six fields are the parameters for the power
coefficient equation shown below. These fields are used to
determine the power coefficient of the system. The analytical
approximation model of the power coefficient in EnergyPlus
is:
If the user does not input any field of these parameters,
the simple approximation model for the power coefficient will
be used (see previous maximum power coefficient field). That
is, the analytical approximation model of the power
coefficient will be chosen only if the user inputs all these
six parameters. The user also has the ability to modify each
parameter when the specific value of the system is available.
The default values are given in the table below.
C1
C2
C3
C4
C5
C6
0.5176
116
0.4
0.0
5.0
21
These fields are only valid for HAWT systems.
An example input for the wind turbine is shown in
below.
Generator:WindTurbine,
WT1, ! Name
WT Schedule, ! Availability Schedule Name
HorizontalAxisWindTurbine, ! Rotor type
FixedSpeedVariablePitch, ! Power control type
41, ! Maximum rotational speed of the rotor {rev/min}
19.2, ! Diameter of the rotor {m}
30.5, ! Overall height of the system {m}
3, ! Number of blades
55000, ! Rated power output at the rated wind speed {W}
11, ! Rated wind speed {m/s}
3.5, ! Cut In wind speed {m/s}
25, ! Cut Out wind speed {m/s}
0.835, ! Overall wind turbine system efficiency
8, ! Maximum tip speed ratio
0.4, ! Maximum power coefficient
6.4, ! Annual local wind speed {m/s}
50, ! Height of local meteorological station {m}
, ! Blade chord area {m2}
, ! Blade drag coefficient
, ! Blade lift coefficient
0.5176, ! Power Coefficient C1
116, ! Power Coefficient C2
0.4, ! Power Coefficient C3
0, ! Power Coefficient C4
5, ! Power Coefficient C5
21; ! Power Coefficient C6
HVAC,Average, Generator Produced Electric Power [W]
HVAC,Sum, Generator Produced Electric Energy [J]
HVAC,Average, Generator Turbine Local Wind Speed [m/s]
HVAC,Average, Generator Turbine Local Air Density [kg/m3]
HVAC,Average, Generator Turbine Power Coefficient []
HVAC,Average, Generator Turbine Tip Speed Ratio []
HVAC,Average, Generator Turbine Chordal Component Velocity [m/s]
HVAC,Average, Generator Turbine Normal Component Velocity [m/s]
HVAC,Average, Generator Turbine Relative Flow Velocity [m/s]
HVAC,Average, Generator Turbine Attack Angle [deg]
This report is the ratio between the rotational speed of
the tip of the blades and the ambient wind speed at the height
of the hub or pole of the wind turbine.
This report represents the efficiency of the power
extraction from the ambient wind of the wind turbine. It is
function of the tip speed ratio and pitch angle. It is only
valid for HAWT systems.
This report is the local relative flow velocity that
represents actual direction and velocity incident on the
blades. It is the square root of the sum of both chordal
velocity component and normal velocity component. It is only
valid for VAWT systems.
This report is the azimuth angle between the relative flow
velocity and the plane of chord. It varies as the wind speed
increases, so that the lift and drag forces change.
Group – Electric Load Center-Generator Specifications[LINK]
ElectricLoadCenter:Transformer[LINK]
This object is used to model the energy losses of transformers when they are used to transfer electricity from the grid to a building (as distribution transformers) or transfer electricity from onsite generators to the grid. Distribution transformers reduce the voltage on utility distribution lines (34.5 kV or less) to a lower secondary voltage (600 V or less) suitable for customer equipment. According to the medium used for cooling and insulation, distribution transformers can be classified into liquid-immersed and dry type transformers. According to the input voltages, distribution transformers can be classified into medium-voltage (between 600 V and 34.5kV) and low-voltage transformer (less than 600 V). The transformers used to output the surplus electricity from onsite generators to the grid usually match the cogeneration voltage to the grid. This object can be used for all types of distribution transformers and the transformers used to output electricity from onsite generators to the grid, but the model defaults applies to the low-voltage dry type transformers because they are the most common type found in commercial and industrial facilities.
Energy losses in transformers consist of the no load (core) loss and the load (winding) loss. The no load loss comes primarily from the switching of the magnetic fields in the core material. It is roughly constant and exists continuously in the core material as long as the transformer is energized. The load loss comes from the electrical resistance in the windings when there is a load on the transformer. The load loss is proportional to the load squared with a small temperature correction. The energy losses at a given load depend on the transformer’s performance. This object provides the user two alternative ways to indicate the transformer’s performance. First, the user can provide the no load loss and load loss at rated conditions. Second, the user can provide the nameplate efficiency and the corresponding reference conditions. The detailed algorithms to calculate the energy losses are described in the Engineering Reference.
The user needs to specify which loads are connected to the transformer. This is achieved in different manners depending on the transformer usage. For a distribution transformer, the user needs to provide a number of electric meters wired to that transformer. The input object can currently accommodate up to ten meters, but it is extensible by modifying the Energy+.idd entry. For a transformer used to output electricity from onsite generators to the grid, the user needs to indicate the transformer name in the served electric load center.
Inputs[LINK]
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that contains information on the availability of the transformer. A schedule value greater than 0 (usually 1 is used) indicates that the transformer is available to convert AC power from one voltage to another. A value less than or equal to 0 (usually 0 is used) denotes that the transformer is not available. If this field is blank, the schedule has values of 1 for all time periods.
Field: Transformer Usage[LINK]
This field indicates one of the two supported transformer application types: PowerInFromGrid and PowerOutFromOnsiteGeneration. The first type of transformer is used to step down voltage from the electricity grid to a building. The second type of transformer is used to match voltage from building onsite generators to the electricity grid.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the transformer is located. Entering a valid name of zone here will direct EnergyPlus to include the transformer’s losses as heat gains to the named thermal zone. If the transformer is not within a thermal zone, this field can be left blank and the thermal energy associated with transformer losses is removed from the building model.
Field: Radiative Fraction[LINK]
This field contains the fraction of transformer’s losses that enter the zone as long-wave thermal radiation. This numeric filed should have a value between 0.0 and 1.0. The balance of the losses is convective. This field is not used if the previous field for zone name is left blank.
Field: Rated Capacity[LINK]
This field defines the rated capacity of the transformer in VA.
Field: Phase[LINK]
This field indicates whether the transformer is a single phase or three phase type. The two alternative values are 1 or 3. The default is 3. This field is currently not used in the model.
Field: Conductor Material[LINK]
This field specifies the winding material used by the transformer. There are two options: Copper and Aluminum. The choice will determine the thermal coefficient of resistance used to calculate the temperature correction factor for the transformer load losses. The default is Aluminum.
Field: Full Load Temperature Rise[LINK]
This numeric field defines the temperature rise of the windings above the ambient temperature, when the transformer is loaded at its nameplate rating. For liquid-immersed distribution transformers, the full load temperature rise usually takes the value of 65 °C. For dry-type transformers, the temperature rise usually takes three optional values: 80, 115 and 150 °C. This field accepts any value between the minimum (50 °C) and the maximum (180 °C). The default is 150 °C.
Field: Fraction of Eddy Current Losses[LINK]
This field defines the fraction of load losses resulting from the eddy currents. Transformer’s load losses comprise two parts: the ohmic loss due to the current flowing in the resistance of the windings and the eddy and stray losses due to the eddy currents. This field indicates the fraction of the load losses due to the eddy currents. This numeric field should have a value between 0.0 and 1.0. The default is 0.1.
Field: Performance Input Method[LINK]
This alpha field contains the method by which the user will specify the transformer performance: “RatedLosses” or “NominalEfficiency”. If this field is left blank in the input data file, the default input method is assumed to be “RatedLosses”. If the method “NominalEfficiency” is selected, the user must enter the fields for the nameplate efficiency and the corresponding reference coditions as described below. If the method “RatedLosses” is selected, then the fields for rated no load loss and load loss must be entered as described below.
Field: Rated No Load Loss[LINK]
This field defines the no load loss (W) at rated load and conditions. The no load loss is roughly constant and exists whenever the transformer is energized. The no load loss is also called the core loss. This field is used only if the field of Performance Input Method is specified as “RatedLosses”.
Field: Rated Load Loss[LINK]
This field defines the load loss (W) at rated load and conditions. The load loss varies with the square of the load being served by the transformer. The load loss is also called the winding loss because the load loss occurs in the primary and secondary windings around the core. This field is used only if the field of Performance Input Method is specified as “RatedLosses”.
Field: Nameplate Efficiency[LINK]
This field contains the value for transformer efficiency at a given per unit load and specified reference temperature. This field is used only if the field of Performance Input Method is specified as “NominalEfficiency”. The default is 0.98.
Field: Per Unit Load for Nameplate Efficiency[LINK]
This field defines the percentage of the rated capacity at which the nameplate efficiency is measured. According to the NEMA (National Electrical Manufactures Association) Standard TP-1, the per unit load takes the value of 0.35 for dry-type distribution transformers and it takes the value of 0.50 for liquid-filled distribution transformers. The default is 0.35.
Field: Reference Temperature for Nameplate Efficiency[LINK]
This field defines the conductor temperature at which the nameplate efficiency is measured. This field is used only if the field of Performance Input Method is specified as “NominalEfficiency”. According to the NEMA Standard TP-1, the reference temperature takes the value of 75 °C for dry-type distribution transformers and it takes the value of 55 °C for liquid-filled distribution transformers. The default is 75 °C.
Field: Per Unit Load for Maximum Efficiency[LINK]
This field defines the percentage of the rated capacity at which the maximum efficiency is obtained. This field is used only if the field of Performance Input Method is specified as “NominalEfficiency”. A blank field indicates that it takes the same value as the per unit load for nameplate efficiency.
Field: Consider Transformer Loss for Utility Cost[LINK]
This field indicates whether the transformer losses are considered to calculate utility cost. In some cases, the transformer losses are required but they are not part of the energy consumption for utility cost calculation. For example, the transformer is owned by the utility company but it locates in the building. In this case, it might be desired to model transformer energy losses for HVAC operation but the energy losses will not be accounted for utility cost.
Field: Electric Meter 1-10 Name[LINK]
A transformer may serve different loads such as plug loads, some lighting loads, and some HVAC equipment loads. The user needs to specify which loads are connected to the transformer. This is achieved by providing a list of electric meters wired to the transformer. The input object can currently accommodate up to ten meters, but it is extensible by modifying the Energy+.idd entry. Any valid electric meter name can be used here to wire to the transformer loads. Many different meters are automatically generated by the program and will depend on the objects used throughout the input file. The typical process of determining the exact name to enter in this field involves doing an initial run of EnergyPlus and then examining the *.mdd file which will list the meters and their resulting names. A custom meter is also supported. The meter must have electricity as its resource type.
An example input of the ElectricLoadCenter:Transformer input is:
Outputs[LINK]
Transformer Efficiency[LINK]
This output field is the efficiency at which the distribution transformer changes alternating current from the higher primary voltage to a lower secondary voltage. The efficiency is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Transformer Output Electric Power [W][LINK]
Transformer Output Elecric Energy [J][LINK]
These outputs are the total electricity power or energy provided by the transformer. They are equal to the metered loads which are wired to the transformer. These values are calculated for each HVAC system timestep being simulated, and the results are averaged (for power) or summed (for energy) for the timestep being reported.
Transformer Input Electric Power [W][LINK]
Transformer Input Electric Energy [J][LINK]
These outputs are the total electricity power or energy fed into the transformer. These values are calculated for each HVAC system timestep being simulated, and the results are averaged (for power) or summed (for energy) for the timestep being reported.
Transformer No Load Loss Rate [W][LINK]
Transformer No Load Loss Energy [J][LINK]
These outputs are the no load loss occurred in the transformer. These values are calculated for each HVAC system timestep being simulated, and the results are averaged (for rate) or summed (for energy) for the timestep being reported.
Transformer Load Loss Rate [W][LINK]
Transformer Load Loss Energy [J][LINK]
These outputs are the load loss occurred in the transformer. These values are calculated for each HVAC system timestep being simulated, and the results are averaged (for rate) or summed (for energy) for the timestep being reported.
Transformer Thermal Loss Rate [W][LINK]
Transformer Thermal Loss Energy [J][LINK]
These outputs are the total energy losses occurred in the transformer. They are equal to the sum of the no load loss and the load loss. These values are calculated for each HVAC system timestep being simulated, and the results are averaged (for rate) or summed (for energy) for the timestep being reported.
Transformer Distribution Electric Loss Energy [J][LINK]
This output is the total energy losses occurred in the transformer when it is used for input power from grid to building. It is set as zero if the transformer is used to transfer energy from onsite power generators to the electricity grid. This output is also added to a meter with ResourceType = Electricity, GroupKey = System.
Transformer Cogeneration Electric Loss Energy [J][LINK]
This output is the total energy losses occurred in the transformer when it is used for input onsite cogeneration to the grid. It is set as zero if the transformer is used to transfer the electricity grid to building. This output is also added to a meter with ResourceType = ElectricityProduced, EndUseKey = Cogeneration, GroupKey = System.
ElectricLoadCenter:Distribution[LINK]
ElectricLoadCenter:Distribution objects are used to include on-site electricity generators in a simulation. The electric load center dispatches generators according to operation schemes and tracks and reports the amount of electricity generated and purchased. When using on-site generators, the program provides a “net” report where the total electricity used is reduced by the amount generated on site. Electrical demand tracking is done by the internal or custom meters used by EnergyPlus for reporting. The thermal demand tracking uses internal load calculations from the plant simulation. The dispatching of different generators is based on expectations based on their nominal/rated electric power output. If the current conditions are such that the generator model determines that generation was higher or lower, then the results of the dispatch may differ from expectations.
Multiple different ElectricLoadCenter:Distribution objects can be included in an input file. A great deal of flexibility is available by mixing different load centers and operating schemes. If multiple load centers are used, the supervisory control will dispatch generators sequentially across the load centers. Therefore, the order of these input objects in the IDF file becomes important with the generators associated with first load center in the file being the first to be managed. A certain amount of caution is needed to avoid conflicting operating schemes.
The electricity produced from photovoltaic arrays will be reported in the electricity produced output variable and will reduce the demand that the generators will try to meet for that timestep.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the electric load center.
Field: Generator List Name[LINK]
This alpha field contains the identifying name for the list of generators in the set.
Field: Generator Operation Scheme Type[LINK]
This alpha field specifies the type of operating scheme for the generator set. The available operating schemes are “Baseload,” “DemandLimit,” “TrackElectrical,” “TrackSchedule,” “TrackMeter,” “FollowThermal,” and “FollowThermalLimitElectrical.” The Baseload scheme operates the generators at their rated (requested) electric power output when the generator is scheduled ON (ref. ElectricLoadCenter:Generators). The Baseload scheme requests all generators scheduled ON (available) to operate, even if the amount of electric power generated exceeds the total facility electric power demand. The DemandLimit scheme limits the amount of purchased electrical from the utility to the amount specified in the input object. The DemandLimit scheme tries to have the generators meet all of the demand above the purchased electric limit set by the user in the next field. The TrackElectrical scheme tries to have the generators meet all of the electrical demand for the building. The TrackSchedule scheme tries to have the generators meet all of the electrical demand determined in a user-defined schedule. The TrackMeter scheme tries to have the generators meet all the electrical demand from a meter, which could also be a user-defined custom meter.
The DemandLimit, TrackElectrical, TrackSchedule, and TrackMeter schemes will sequentially load the available generators. All demand not met by available generator capacity will be met by purchased electrical. Therefore, if DemandLimit, TrackElectrical, TrackSchedule, or TrackMeter is utilized and the available generators are not enough to meet demand, then purchased electrical will offset the difference. If a generator is needed in the simulation for a small load and it is less than the minimum part load ratio the generator will operate at the minimum part load ratio and the excess will either reduce demand or the excess energy will be available for returning to the electric grid.
The FollowThermal and FollowThermalLimitElectrical schemes are for heat following cogeneration and run the generators to meet the thermal demand. The FollowThermal schemes allow excess electrical generation to be exported to the grid, while the FollowThermalLimitElectrical scheme restricts generator output to a maximum of the building’s current electrical demand (so that no electricity is exported). The thermal demand is determined from the plant modeling and depends on the flow requested by other components on the demand side of the plant loop, the loop temperatures, and the loop temperature set point. The electric load center converts the thermal load to an electrical load using a nominal ratio of the thermal to electrical power production for each generator. For these schemes, the generator needs to be connected to the supply side of a plant loop and components that request hot water need to be on the demand side of the plant loop. This is different than the usual configuration for electrical following schemes where the generator is put on the demand side and request flow for the purposes of cooling the generator. Therefore a switch from one of the electrical-based operating schemes to one of the thermal-based operating schemes requires a substantial change in plant topology.
If the load center includes electrical storage, then the choice of operating schemes will also affect how storage is managed.
Field: Demand Limit Scheme Purchased Electric Demand Limit[LINK]
This numerical field is the user input for the demand limit above which the generators will try and meet the entire electrical load on the building minus the photovoltaic array if available.
Field: Track Schedule Name Scheme Schedule Name[LINK]
This alpha field is the user input for the name of a schedule defined elsewhere in the input file that contains values for the “demand” loads placed on the generator(s). The schedule values should be in Watts.
Field: Track Meter Scheme Meter Name[LINK]
This alpha field is the user input for the name of a meter. Any valid meter name can be used here to control the loads that the generator(s) will try to meet. Many different meters are automatically generated by the program and will depend on the objects used throughout the input file. The typical process of determining the exact name to enter in this field involves doing an initial run of EnergyPlus and then examining the *.rdd file which will list the meters and their resulting names. The *.mtd file will also be useful to understand what exactly is included in a meter. The user can also use the Output:CustomMeter objects to redefine meter names and to control what electrical loads are included on them in a flexible manner.
Field: Electrical Buss Type[LINK]
This alpha field is used to describe how the electric load center is configured with respect to any power conditioning and/or storage equipment. There are five configurations for load centers available by using one of these keywords:
AlternatingCurrent is the default. All the generators connected to a specific load center need to be of the same type (all AC or all DC). If the generators are DC, then an inverter is needed to convert the DC to AC. If there are DC generators and a DC electrical storage device on the buss along with an inverter, then use DirectCurrentWithInverterDCStorage in this field. See the Engineering Reference for more information including diagrams of the load center configurations.
Field: Inverter Object Name[LINK]
This field is used to identify the inverter connected to this load center (if any). This field is only used if the Electrical Buss Type is set to DirectCurrentWithInverter and should contain the user-defined name of an inverter object. There are three types of inverter models available–see ElectricLoadCenter:Inverter:Simple, ElectricLoadCenter:Inverter:LookUpTable, or ElectricLoadCenter:Inverter:FunctionOfPower. Enter the name of one of these types of inverter objects defined elsewhere in the input file.
Field: Electrical Storage Object Name[LINK]
This field is used to identify the electrical storage connected to this load center (if any). This field is only used if the Electrical Buss Type is set to DirectCurrentWithInverterDCStorage or DirectCurrentWithInverterACStorage. Enter the name of an ElectricLoadCenter:Storage:Simple object defined elsewhere in the input file.
Field: Transformer Object Name[LINK]
This field is used to identify the transformer connected to this load center (if any). This field can be used for any electrical buss types. Enter the name of an ElectricLoadCenter:Transformer object defined elsewhere in the input file.
Examples of this object are:
Outputs[LINK]
There are three levels of results reporting related to electric load centers and generators. The top level of reporting provides results across the whole building and all the different electric load centers and generators. The second level of reporting provides results for individual load centers. The third level is for each type of generator (see individual generator descriptions). This section discusses the first two levels.
The whole-building summary output variables are:
These output variables all use a default keyword “Whole Building.”
These output variables can also be accessed without specifying generation equipment by including the syntax shown below:
Even if no ElectricLoadCenter:Distribution object is included, these output variables are also available for all simulations that have any electricity consuming equipment with the default keyword name “Electrical Service.”
Facility Total Produced Electric Power [W][LINK]
Facility Total Produced Electric Energy [J][LINK]
These outputs are the total generator and photovoltaic electricity produced on-site for the entire model, and they are in both Power and Energy units. When electrical storage is used with on-site production, the electricity put into storage is decremented from production and the electricity removed storage is added to production. This means that losses from a round trip through electrical storage decrease on-site electricity production.
Facility Total Purchased Electric Power [W][LINK]
Facility Total Purchased Electric Energy [J][LINK]
These outputs are the total of electricity purchased for the entire model in both Power and Energy units. This value is always positive and indicates the amount of energy is purchased from the utility.
Facility Total Surplus Electric Energy [J][LINK]
This output is the excess electricity produced and sent out to the electrical grid. This value is always positive and indicates the surplus electricity from generation that exceeds whole-building demand and fed into the grid.
Facility Total Building Electric Demand Power [W][LINK]
This output variable includes all of the electric demand from the building (non-HVAC) portion of the simulation, which would contain lights, electrical equipment, exterior lights and equipment, etc.
Facility Total HVAC Electric Demand Power [W][LINK]
This output variable includes all of the electric demand from the HVAC portion of the simulation, which would contain fans, electric coils, pumps, chillers, cooling towers, etc.
Facility Total Electric Demand Power [W][LINK]
This is the total of the whole Building and HVAC electric demands.
Facility Net Purchased Electric Power [W][LINK]
Facility Net Purchased Electric Energy [J][LINK]
These outputs are the net electricity purchased in both Power and Energy units. This value can be either positive or negative. Positive values are defined as electricity purchased from the utility. Negative values are defined as surplus electricity fed back into the grid.
Each ElectricLoadCenter also collects results from the individual generators that are connected to that load center. The output variables available at the ElectricLoadCenter level are:
Electric Load Center Requested Electric Power [W][LINK]
This output variable is the average electric power supply (in watts) requested by the load center from its generators for the time step being reported. For the baseload operating scheme, this output variable should equal the sum of the power supply requests for the ‘available’ generators associated with this load center (ref. ElectricLoadCenter:Generators). In other cases, this output could be different from the sum of the power supply requests for the generators associated with this load center. For example, a generator might be requested to provide a certain amount of power but can only provide a fraction of the requested amount. In this case the load center will detect this shortfall and include it when calculating the power request for the next available generator. Therefore, the sum of the power supply requests for the individual generators associated with this load center (ref. ElectricLoadCenter:Generators) could be greater than the Electric Load Center Requested Electric Power output variable.
Electric Load Center Produced Electric Power [W][LINK]
Electric Load Center Produced Electric Energy [J][LINK]
These outputs are the sum of electrical energy and power produced by the generators attached to a particular load center. The keywords for these reports are the unique names of ElectricLoadCenter:Distribution objects.
Electric Load Center Produced Thermal Rate [W][LINK]
Electric Load Center Produced Thermal Energy [J][LINK]
These outputs are the sum of the thermal energy and power produced by the generators attached to a particular load center. The keywords for these reports are the unique names of ElectricLoadCenter:Distribution objects.
ElectricLoadCenter:Generators[LINK]
The ElectricLoadCenter:Generators object is used to provide a list of the generators to include in the simulation. The list includes the names and types of all the generators along with separate availability schedules, the rated power output, and thermal-to-electrical power ratio for each. Sets of five input fields are repeated for each generator. If more than 30 generators are needed, EnergyPlus will “auto-extend” to suit the needs but other interfaces (such as the IDF Editor may not). The user can always modify the Energy+.idd file to accommodate the extra fields necessary, but it is likely the next release of EnergyPlus will overwrite any user modifications.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the generators in the set.
FieldSet: Name, Object Type, Rated Power Output, Availability, Thermal Ratio up to 30[LINK]
Each generator is specified by a set of 5 input fields that contain an identifying name, a keyword that indicates the type of generator, the rated output of the generator, the availability schedule of the generator, and the thermal to electrical power production ratio.
Field: Generator Name [LINK]
This alpha field contains the identifying name for the first generator in the list.
Field: Generator
Object Type [LINK]
This alpha field contains the keyword for the type of generator. The available types include:
These keywords are the names of the input objects for the type of generator.
Field: Generator Rated Electric Power Output [LINK]
This numeric field contains the nominal electric power output to be requested from generator 1. It is normally equal to the rated power output of the generator in Watts. This value is used only for supervisory control and generator dispatch; the actual power output for each time step is determined by the generator models. This value affects how much a generator is loaded (i.e., requested electric power output) and can also impact the operation of an electric storage unit (e.g., LoadCenter:Storage:Simple) if one is connected to the associated load distribution center (ref. ElectricLoadCenter:Distribution). Refer to Electrical Storage in the EnergyPlus Engineering Reference for more details regarding this input field and its relationship with electric storage.
Field: Generator Availability Schedule Name [LINK]
This alpha field is used as an identifying field for the generator availability schedule. If not blank, this field must contain the name of a schedule defined elsewhere in the input file. A schedule value of <=0.0 indicates the generator is not available, while a schedule value > 0.0 indicates that the generator is available to operate. If this field is blank, the schedule has values of 1 for all time periods.
Field: Generator Rated Thermal to Electrical Power Ratio [LINK]
This numeric field contains the ratio of the rated thermal output to the rated electric output. It is only needed and used if the operation scheme is set to FollowThermal or FollowThermalLimitElectrical. This nominal ratio is only used for control and dispatch decisions. This value should be generally consistent with the more detailed performance input for the individual generator component models but it is not used in those component models.
An example IDF showing how this object is used is provided below:
Outputs[LINK]
A single output variable is available for each generator specified via this object as described below:
Generator Requested Electric Power [W][LINK]
This output variable represents the average electric power supply in Watts that is being requested from a specific generator for the time step being reported. In some instances the output value may be the Rated Electric Power Output specified for the generator in the ElectricLoadCenter:Generators object. If the generator is not available for a simulation time step (as indicated by its availability schedule), then the power supply request will be zero. The power supply request may be less than the rated electric power output if the overall electric power reduction target has already been met, partially or completely, by electric power produced by other generators. If an EnergyPlus Energy Management System is used to specify an electric power supply request for this generator, then that EMS request will be reflected in this output variable.
ElectricLoadCenter:Inverter:Simple[LINK]
This input object is used to model conversion from Direct Current (DC) to Alternating Current (AC) in an electric load center that contains photovoltaic modules. Such a load center has an array of photovoltaic modules that feed an inverter DC power and the inverter produces AC power. This input object is for the simplest inverter model and uses a fixed efficiency. There are two other types of inverters with more complex models described below.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the inverter. The name entered must also be unique across all other types of inverters that may also be in the input file.
Field: Availability Schedule Name[LINK]
This field contains the name of a schedule that describes when the inverter is available. If the inverter is scheduled to not be available, by scheduling a value of 0, then it cannot produce AC power and will not consume ancillary power during standby. Any non-zero schedule value means the inverter is available to produce AC power and consume ancillary power during standby. If the Inverter is scheduled to be unavailable but it is being supplied with DC power anyway, then the energy is dissipated as heat. If this field is blank, the schedule has values of 1 for all time periods.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the inverter is located. Entering a valid name of zone here will direct EnergyPlus to include the inverter’s losses as heat gains to the named thermal zone. If the inverter is not within a thermal zone, then this field can be left blank (and the thermal energy associated with inverter losses is removed from the building model).
Field: Radiative Fraction[LINK]
This field contains the fraction of inverter thermal losses that enter the zone as long-wave thermal radiation. This should be a factor between 0.0 and 1.0. The balance of the losses is convective. This field is not used if the previous field for zone name is left blank.
Field: Inverter Efficiency[LINK]
This field contains the value for inverter efficiency. In the simple model, efficiency is a constant. This is the so-called 1-term model. Input data for different types of inverters is available at http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries where the “CEC Efficiency” would be the value to enter here.
An example IDF showing how this object is used is provided below:
ElectricLoadCenter:Inverter:FunctionOfPower[LINK]
This input object is used to model conversion from Direct Current (DC) to Alternating Current (AC) in an electric load center that contains photovoltaic modules. Such a load center has an array of photovoltaic modules that feed an inverter DC power and the inverter produces AC power. This input object is for an inverter model where efficiency is a function of normalized power.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the inverter. The name entered must also be unique across all other types of inverters that may also be in the input file.
Field: Availability Schedule Name[LINK]
This field contains the name of a schedule that describes when the inverter is available. If the inverter is scheduled to not be available, by scheduling a value of 0, then it cannot produce AC power, nor contribute heat gains to the zone, and will not consume ancillary power during standby. Any non-zero schedule value means the inverter is available to produce AC power, contribute heat gains to the zone and consume ancillary power during standby. If this field is blank, the schedule has values of 1 for all time periods.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the inverter is located. Entering a valid name of zone here will direct EnergyPlus to include the inverter’s losses as heat gains to the named thermal zone. If the inverter is not within a thermal zone, then this field can be left blank (and the thermal energy associated with inverter losses is removed from the building model).
Field: Radiative Fraction[LINK]
This field contains the fraction of inverter thermal losses that enter the zone as long-wave thermal radiation. This should be a factor between 0.0 and 1.0. The balance of the losses is convective. This field is not used if the previous field for zone name is left blank.
Field: Efficiency Function of Power Curve Name[LINK]
This field contains the name of curve representing the relationship between DC power input into the inverter and the efficiency with which that power is converted to AC. The curve can be either a Curve:Linear, Curve:Quadratic, or Curve:Cubic. The curve’s “x” value is DC power input normalized by the following field. The result of the curve should be power conversion efficiency expressed as a fraction between 0.0 and 1.0.
Field: Rated Maximum Continuous Input Power[LINK]
This field contains the rated power input in watts. This is value used to normalize input power for use with the curve named in the previous field. This is DC power from the PV arrays going into the inverter.
Field: Minimum Efficiency[LINK]
This field contains a minimum bound on the inverter efficiency. This value will be used as a limit on the curve’s result.
Field: Maximum Efficiency[LINK]
This field contains a maximum bound on the inverter efficiency. This value will be used as a limit on the curve’s result.
Field: Minimum Power Output[LINK]
This field contains a lower limit on the AC power produced by the inverter. If the resulting power output would be below this level, then the inverter is assumed to not produce any power and is in stand by mode. All DC power input is lost (unless it is going into storage).
Field: Maximum Power[LINK]
This field contains an upper limit on the AC power produced by the inverter. If the resulting power output would be above this level, then the power produced is capped at this level with the rest of input power converted to losses (unless it is going into storage).
Field: Ancillary Power Consumed In Standby[LINK]
This field contains the ancillary power in watts used by the inverter when not producing AC power. This is AC electricity consumed in standby mode. Standby mode occurs when the inverter is scheduled to be available but the incoming DC power is too low.
An example IDF showing how this object is used is provided below:
ElectricLoadCenter:Inverter:LookUpTable[LINK]
This input object is used to model conversion from Direct Current (DC) to Alternating Current (AC) in an electric load center that contains photovoltaic modules. Such a load center has an array of photovoltaic modules that feed an inverter DC power and the inverter produces AC power. This input object is for an inverter model where efficiency is interpolated using a look up table.
This object was designed for use with data contained in the Inverter Performance Test Summaries available at http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries. All of the data needed for this object can be found there by make and model of inverter. The core of the data set is a 3x6 matrix of efficiency at different voltage and power levels. These form the look up table used in the model. Note that EnergyPlus’ PV models currently model only power and not the voltage and current situation. Therefore, only the nominal voltage data are used. This is the middle row of data in the Go Solar summaries.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the inverter. The name entered must also be unique across all other types of inverters that may also be in the input file.
Field: Availability Schedule Name[LINK]
This field contains the name of a schedule that describes when the inverter is available. If the inverter is scheduled to not be available, by setting a value of 0, then it cannot produce AC power, nor contribute heat gains to the zone, and will not consume ancillary power during standby. Any non-zero schedule value means the inverter is available to produce AC power, contribute heat gains to the zone and consume ancillary power during standby. If this field is blank, the schedule has values of 1 for all time periods.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the inverter is located. Entering a valid name of zone here will direct EnergyPlus to include the inverter’s losses as heat gains to the named thermal zone. If the inverter is not within a thermal zone, then this field can be left blank (and the thermal energy associated with inverter losses is removed from the building model).
Field: Radiative Fraction[LINK]
This field contains the fraction of inverter thermal losses that enter the zone as long-wave thermal radiation. This should be a factor between 0.0 and 1.0. The balance of the losses is convective. This field is not used if the previous field for zone name is left blank.
Field: Rated Maximum Continuous Output Power[LINK]
This field contains the rated maximum continuous output power in watts.
Field: Night Tare Loss Power[LINK]
This field contains the “night tare loss” in watts. This is modeled as ancillary power consumed during standby.
Field: Nominal Voltage Input[LINK]
This field contains the nominal DC input voltage in volts. This is “Vnom” in the Go Solar test summaries.
Field: Efficiency at 10% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 10% power.
Field: Efficiency at 20% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 20% power.
Field: Efficiency at 30% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 30% power.
Field: Efficiency at 50% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 50% power.
Field: Efficiency at 75% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 75% power.
Field: Efficiency at 100% Power and Nominal Voltage[LINK]
This field contains the fractional efficiency at nominal voltage and 100% power.
An example IDF showing how this object is used is provided below:
Outputs[LINK]
Each inverter can report the following seven output variables.
Inverter DC to AC Efficiency [ ][LINK]
This is the efficiency with which DC power is converted to AC power by the inverter.
Inverter DC Input Elecric Power [W][LINK]
Inverter DC Input Electric Energy [J][LINK]
These outputs are total electricity power or energy fed into the inverter. This is Direct Current from photovoltaics (or DC-based electrical storage) going into the inverter.
Inverter AC Output Electric Power [W][LINK]
Inverter AC Output Electric Energy [J][LINK]
These outputs are the total electricity power or energy produced by the inverter. This is Alternating Current going out of the inverter.
Inverter Thermal Loss Rate [W][LINK]
Inverter Thermal Loss Energy [J][LINK]
These outputs are the thermal power or energy losses in the inverter that stem from converting from DC to AC.
Inverter Ancillary AC Electric Power [W][LINK]
Inverter Ancillary AC Electric Energy [J][LINK]
These outputs are the Alternating Current electricity consumed by the inverter. These are ancillary, or night tare loss, power uses by the inverter and modeled as if powered by the building’s grid connection. These ancillary power draws generally occur when the inverter is not generating power but waiting in a standby mode ready to begin generating power.
ElectricLoadCenter:Storage:Simple[LINK]
This input object is used to model storage of electricity in an electric load center. This is a simple model that does not attempt to represent any of the characteristics of a real storage device such as a battery. The type of power, AC or DC, depends on the configuration chosen as the Electrical Buss Type in the ElectricLoadCenter:Distribution object.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the electric storage device.
Field: Availability Schedule Name[LINK]
This field contains the name of a schedule that describes when the storage device is available. If storage is not available, by scheduling a value of 0, then no electrical energy can be stored or drawn from the device. Any non-zero schedule value means the devices is available. If this field is blank, the schedule has values of 1 for all time periods.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the storage device is located. Entering a valid name of a zone here will direct EnergyPlus to include the storage losses as heat gains to the name thermal zone. If the storage is not within a therma zone, then this field can be left blank.
Field: Radiative Fraction for Zone Heat Gains[LINK]
This field contains the fraction of storage losses that enter the zone as long-wave thermal radiation. This should be a factor between 0.0 and 1.0. The balance of the losses are convective. This field is not used if the previous field for zone name is left blank.
Field: Nominal Energetic Efficiency for Charging[LINK]
This field contains the charging efficiency. This is the energetic efficiency of storing electrical energy in the storage device. A value of 1.0 means the device does not lose any energy when charging.
Field: Nominal Discharging Energetic Efficiency[LINK]
This field contains the discharging efficiency. This is the energetic efficiency of drawing electrical energy from the storage device. A value of 1.0 means the device does not lose any energy when drawing power.
Field: Maximum Storage Capacity[LINK]
This field describes the maximum amount of energy that can be stored in the device in Joules. Once the storage device is full, no additional energy can be stored in it.
Field: Maximum Power for Discharging[LINK]
This field describes the maximum rate at which electrical power can be discharged from the storage device in watts.
Field: Maximum Power for Charging[LINK]
This field describes the maximum rate at which electrical power can be stored in the device in watts.
Field: Initial State of Charge[LINK]
This field describes the value for the initial state of charge in Joules. This is used to model the storage device as having some amount of stored energy at the beginning of the simulation period.
An example IDF showing how this object is used is provided below:
Outputs[LINK]
Each electrical storage device can report the following seven output variables.
Electric Storage Charge State [J][LINK]
This output is the state of charge of the storage device. State of charge is the amount of electrical energy stored in the device at a point of time. The amount of energy stored in tracked in Joules.
Electric Storage Charge Power [W][LINK]
Electric Storage Charge Energy [J][LINK]
These outputs are total electricity power or energy fed into the storage device. This is the rate or amount of charging.
Electric Storage Production Decrement Energy [J][LINK]
This output is the total electricity energy decremented from electricity production because it has fed into the storage device. This output has the opposite sign of “Electric Storage Charge Energy” but is otherwise similar. This decrement output variable is also a meter associated with the resource type “ElectricityProduced” that reduces the metered electricity production to account for power that went into storage after production.
Electric Storage Discharge Power [W][LINK]
Electric Storage Discharge Energy [J][LINK]
These outputs are total electricity power or energy drawn from the storage device. This is the rate or amount of discharging. The energy from storage output variable is also a meter associated with the resource type “ElectricityProduced” that increases the metered electricity production to account for power that has come back out of storage.
Electric Storage Thermal Loss Rate [W][LINK]
Electric Storage Thermal Loss Energy [J][LINK]
These outputs are the thermal power or energy losses from both charging and drawing electrical power in or out of the storage device. These losses are the result of inefficiencies in charging and drawing.
ElectricLoadCenter:Storage: Battery[LINK]
This object uses the kinetic battery model (KiBaM) to simulate rechargeable battery banks in an electrical load center. The battery bank is a collection of one or more individual battery modules. Given the surplus or deficit power from the electrical system and the state of charge from the previous time step, this object can model the voltage, current, and energy losses with charging and discharging during each time step. The cumulative battery damage can be also modeled and reported at the end of each simulation run.
This object allows the simulation of both lead-acid and Nickel Cadmium batteries. With input parameters derived from specific battery tests, the object is expected to support other battery types such as Lithium-ion batteries.
The kinetic battery model assumes that part of the battery’s energy storage capacity is immediately available in discharging or charging while the rest is chemically bound. As a function of constant current, the battery capacity is related to three parameters: the maximum capacity at infinitesimal current, the capacity ratio of available charges, and the conversion ratio between available charges and bound charges. These parameters are usually obtained via curve fitting based on battery data sheets or test data.
Each individual battery module is modeled as a voltage source in series with an electrical resistance. KiBaM assumes that the internal resistance is constant and the open circuit voltage varies with the electric current, the state of charge and the operation mode (charging or discharging). For an individual battery module, the open circuit voltage at any time is correlated to the voltage at fully charged/discharged state and three other regression coefficients. These regression coefficients are usually obtained via curve fitting based on battery test data.
The object offers user the option to perform battery life calculation. If battery life is modeled, the user needs to provide a group of coefficients for the correlation between the number of cycles for battery failure and the corresponding cycle range. More detailed information can be found from the Engineering Reference.
Field: Name[LINK]
This alpha field contains the identifying name for the battery bank.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that describes when the battery is available. A schedule value greater than 0 (usually 1 is used) indicates that electrical energy can be stored or drawn from the battery. A value less than or equal to 0 (usually 0 is used) denotes that the battery is not available. If this field is blank, the schedule has values of 1 for all time periods.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the battery is located. Entering a valid name of zone here will direct EnergyPlus to include the energy storage losses as heat gains to the named thermal zone. If the battery is not within a thermal zone, this field can be left blank and the thermal energy associated with storage losses is removed from the building model.
Field: Radiative Fraction[LINK]
This field contains the fraction of storage losses that enter the zone as long-wave thermal radiation. This numeric filed should have a value between 0.0 and 1.0. The balance of the losses is convective. This field is not used if the previous field for zone name is left blank.
Field: Number of Battery Modules in Parallel[LINK]
This field defines the number of modules connected in parallel in the battery bank.
Field: Number of Battery Modules in Series[LINK]
This field defines the number of modules connected in series in the battery bank. The total number of modules in a battery bank is equal to the number of modules in parallel times the number of modules in series.
Field: Maximum Module Capacity[LINK]
This field indicates the maximum capacity of one battery module. It is evaluated as the total Amp-hours available when a full battery is discharged at infinitesimal current. This capacity is for an individual battery module, not for the whole battery bank. The maximum capacity can be found from manufacture’s data or derived from test data by curve fitting.
Field: Initial Fractional State of Charge[LINK]
This field describes the initial state of charge in terms of the fraction of maximum capacity as defined in the previous field.
Field: Fraction of Available Charge Capacity[LINK]
The kinetic battery model assumes that battery is a two-tank electrical energy storage device: an available tank and a bound tank. The available tank can be immediately charged or discharged, while the bound tank can only be charged or discharged via the available tank. This field specifies the fraction of total charge in the battery that is part of the available tank. The ratio of available charge capacity to total capacity is a parameter usually derived from test data by curve fitting.
Field: Change Rate from Bound Charge to Available Charge[LINK]
This field specifies the rate at which the charge flows between the available tank and the bound tank. It is a parameter used to calculate the conversion between available charge and chemically bound charge when charging and discharging the battery. This parameter is usually derived from test data by curve fitting.
Field: Fully Charged Module Open Circuit Voltage[LINK]
This field indicates the open circuit voltage for a fully charged battery module. It can be found from manufacture’s data or battery tests.
Field: Fully Discharged Module Open Circuit Voltage[LINK]
This field indicates the open circuit voltage for a fully discharged battery module. It can be found from manufacture’s data or battery tests.
Field: Voltage Change Curve Name for Charging[LINK]
This field specifies the name of a rectangular hyperbola type 2 performance curve (ref: Curve:RectangularHyperbola2 in Performance Curves) that determines the change of open circuit voltage (\(\Delta E\)) as a function of the battery state of charge in charging. The change of open circuit voltage is relative to a fully discharged battery.
The curve has the following form:
\[\Delta E = ({C_1}*X)/({C_2} + X) + {C_3}*X\]
where X is the battery charge divided by the maximum capacity at a given current. More details can be found from the Engineering Reference.
Field: Voltage Change Curve Name for Discharging[LINK]
This field specifies the name of a rectangular hyperbola type 2 performance curve (ref: Curve:RectangularHyperbola2 in Performance Curves) that determines the change of open circuit voltage (\(\Delta E\)) as a function of the battery state of charge in discharging. The change of open circuit voltage is relative to a fully charged battery.
The curve has the following form:
\[\Delta E = ({C_1}*X)/({C_2} + X) + {C_3}*X\]
where X is the removed charge divided by the maximum capacity at a given current. More details can be found from the Engineering Reference.
Field: Module Internal Electrical Resistance[LINK]
This field specifies the battery internal resistance in ohms. In theory, the electrical resistance within the battery varies with the state of charge and depends on whether it is in charging or discharging. In the kinetic battery model, the internal resistance is assumed as constant and the terminal voltage varies with current and state of charge. The internal resistance may be obtained from the battery manufacture or battery test data. Note that the field is for an individual module, not for the whole battery bank.
Field: Maximum Module Discharging Current[LINK]
This field indicates the maximum current at which the battery can be discharged continuously. The limit on discharge current is usually defined by the battery manufacture to avoid battery damage. The limit is for an individual battery module.
Field: Module Cut-off Voltage[LINK]
This field specifies the minimum allowable voltage, below which the battery is generally regarded as empty. The cut-off voltage is usually defined by the battery manufacture and it is for an individual battery module.
Field: Module Charge Rate Limit[LINK]
This field specifies the limit on charging current relative to the remaining charge until the battery is full. This limit reflects the common practice that the charge rate is reduced as the battery gets more charged.
Field: Battery Life Calculation[LINK]
This field indicates whether the battery life model is activated in the simulation. If the battery life model is activated, the following five inputs on curve coefficients are required; otherwise, they are not used.
Field: Number of Cycle Bins[LINK]
This field specifies the number of equally ranged cycle bins in battery life simulation. If 10 bins are used, the cycle ranges will include 10%, 20%, …, 100%.
Field: Battery Cycle Life Curve Name[LINK]
This field specifies the name of a double exponential decay curve (ref: Curve:DoubleExponentialDecay in Performance Curves) that correlates the cycles of battery failure (CF) and fractional depth of discharge (R). The curve is:
\[{C_F} = {C_1} + {C_2}{e^{{C_3}R}} + {C_4}{e^{{C_5}R}}\]
An example input of the ElectricLoadCenter:Storage: Battery input is:
ElectricLoadCenter: Storage:Battery Outputs[LINK]
Electric Storage Operating Mode Index [][LINK]
This output reports the battery mode of operation: 0 for idle; 1 for discharging; 2 for charging. It is expected that more operation modes would be added when a smart and active power dispatch controller is used in future.
Electric Storage Charge State [Ah][LINK]
The state of charge is expressed as the amount of charge stored in the battery at a point of time. It has the same unit as the maximum capacity. This value is given for an individual battery module
Electric Storage Charge Fraction [][LINK]
This output is the ratio between the electrical storage state of charge and the maximum capacity.
Electric Storage Charge Power [W][LINK]
Electric Storage Charge Energy [J][LINK]
These outputs are total electricity power or energy fed into the battery. This is the rate of amount of charging.
Electric Storage Production Decrement Energy [J][LINK]
This output is the total electricity energy decremented from electricity production because it has fed into the battery. This output has the opposite sign of “Electric Storage Charge Energy” but is otherwise similar. This decrement output variable is also a meter associated with the resource type “ElectricityProduced” that reduces the metered electricity production to account for power that went into storage after production.
Electric Storage Discharge Power [W][LINK]
Electric Storage Discharge Energy [J][LINK]
These outputs are total electricity power or energy drawn from the battery. This is the rate or amount of discharging. The energy from storage output variable is also a meter associated with the resource type “ElectricityProduced” that increases the metered electricity production to account for power that has come back out of storage.
Electric Storage Total Current [A][LINK]
This output is the current to or from the battery bank depending on whether the battery is in the state of charging or discharging. The value is positive for discharging and negative for charging.
Electric Storage Total Voltage [V][LINK]
This output is the total terminal voltage of the battery bank.
Electric Storage Thermal Loss Rate [W][LINK]
Electric Storage Thermal Loss Energy [J][LINK]
These outputs are the thermal power or energy losses from both charging and drawing electrical power in or out of the storage device. These losses are due to the battery internal resistance in charging and discharging.
Electric Storage Degradation Fraction [][LINK]
This output reports the fractional battery life used up at a point of time. For example, a value of 0.4 at the end of one year simulation means that the 40% of the battery life is used up, so the battery needs to be replaced every two and a half years.
Generator:InternalCombustionEngine[LINK]
The Internal Combustion (IC) Engine generator uses a modified Otto cycle. This generator model uses the electrical load and rated engine generator size to compute part-load ratios (PLR). Fuel energy input and recoverable jacket and lube oil heat are then computed. Finally, the recoverable exhaust heat is calculated.
Manufacturer’s curves or tables must be obtained for IC engine generators to derive the equipment performance parameters that are specified in the quadratic curve fits. Note that simple transformation of the form of the manufacturer’s curves may be required. Electric energy output/fuel energy input is related to the part-load ratio (i.e., electric/load generator capacity) with a polynomial. Recoverable jacket heat/fuel energy equipment, recoverable lube oil heat/fuel energy input equipment performance, total exhaust heat/fuel energy input equipment, exhaust gas temperature/fuel energy input equipment performance parameters are all specified with a quadratic curve fit.
When the heat recovery curve fits = 0.0, this means that no heat recovery is done on the IC engine generator exhaust gas; and no heat recovery is specified.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the IC engine generator.
Field: Rated Power Output[LINK]
The design nominal capacity of the generator in Watts [W].
Field: Electric Circuit Node Name[LINK]
This named node contains where the electric power is put in the program simulation for use by the electric equipment in the Load Center.
Field: Minimum Part Load Ratio[LINK]
This field contains the minimum allowed operating fraction of full load. The input value must be >=0.0 and <=1.0.
Field: Maximum Part Load Ratio[LINK]
This field contains the maximum allowed operating fraction of full load. The input value must be >0.0 and <=1.0.
Field: Optimum Part Load Ratio[LINK]
This alpha field contains the optimal operating fraction of full load. This is the part load ratio that gives the optimal production of electric power with the least amount of fuel usage.
Field: Shaft Power Curve Name[LINK]
This alpha field contains the name of the shaft power curve. The curve itself is specified separately using a curve object (ref: Curve:QuadLinear). The Shaft Power Curve is a quadratic equation that determines the electric output versus the fuel used. Used to calculate the electric energy output divided by the fuel energy consumption as a function of part-load ratio. The defining equation is:
\[ShaftPowerToFuelRatio = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
Field: Jacket Heat Recovery Curve Name[LINK]
This alpha field contains the name of the Recovery Jacket Heat curve. The curve itself is specified separately using a curve object (ref: Curve:QuadLinear). The Jacket Heat Recovery Curve is a quadratic equation that determines the ratio of recovery jacket heat to fuel energy. Used to calculate the recoverable jacket heat as a function of part-load ratio.
The defining equation is:
\[RecoveryJacketHeatToFuelRatio = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
Field: Lube Heat Recovery Curve Name[LINK]
This alpha field contains the name of the Recovery Lube Heat curve. The curve itself is specified separately using a curve object (ref Curve:QuadLinear). The Lube Heat Recovery Curve is a quadratic equation that determines the ratio of recovery lube heat to fuel energy. Used to calculate the recoverable lube oil heat as a function of part-load ratio. The defining equation is:
\[RecoveryLubeHeatToFuelRatio = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
Field: Total Exhaust Energy Curve Name[LINK]
This alpha field contains the name of the Total Exhaust Energy curve. The curve itself is specified separately using a curve object (ref Curve:QuadLinear object). The Total Exhaust Energy Curve is a quadratic equation that determines the ratio of total exhaust energy to fuel energy. Used to calculate the total exhaust heat as a function of part-load ratio. The defining equation is:
\[TotalExhaustToFuelRatio = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
Field: Exhaust Temperature Curve Name[LINK]
This alpha field contains the name of the Exhaust Temperature curve. The curve itself is specified separately using a curve object (ref Curve:QuadLinear object). The Exhaust Temperature Curve is a quadratic equation that determines the absolute exhaust temperature. Used to determine the exhaust gas temperature as a function of part-load ratio. The defining equation is:
\[AbsoluteExhaustTemperature = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
U-Factor Times Area (UA) Curve[LINK]
The UA curve applies to the exhaust gas heat exchanger. The curve is an equation that determines the overall heat transfer coefficient for the exhaust gases with the stack. The heat transfer coefficient ultimately helps determine the exhaust stack temperature. The defining equation is:
\[UAToCapacityRatio = {C_1}GeneratorRatedPowerOutpu{t^{{C_2}}}\]
The following two fields contain the coefficients for the equation.
Field: Coefficient 1 of U-Factor Times Area Curve[LINK]
This numeric field contains the first coefficient for the overall heat transfer coefficient curve.
Field: Coefficient 2 of U-Factor Times Area Curve[LINK]
This numeric field contains the second (exponential) coefficient for the overall heat transfer coefficient curve.
Field: Maximum Exhaust Flow per Unit of Power Output[LINK]
Maximum exhaust flow per unit capacity for the generator. The parameter sets an upper limit on exhaust gas flow and exhaust gas heat recovery for the generator. Units: kg/sec per kW capacity
Field: Design Minimum Exhaust Temperature[LINK]
This is the design engine stack saturated steam temperature in degrees C.
Field: Fuel Higher Heating Value[LINK]
This numeric field contains the higher heating value of the fuel used in kJ/kg.
Field: Design Heat Recovery Water Flow Rate[LINK]
Design water volumetric flow rate through heat recovery loop in m3/sec.
Field: Heat Recovery Inlet Node Name[LINK]
This alpha field contains the identifying name for the generator’s heat recovery side inlet node.
Field: Heat Recovery Outlet Node Name[LINK]
This alpha field contains the identifying name for the generator’s heat recovery side outlet node.
Field: Fuel Type[LINK]
This alpha field determines the type of fuel that the generator uses. The default is Diesel. Valid values are: NaturalGas, PropaneGas, Diesel, Gasoline, FuelOil#1, FuelOil#2, OtherFuel1, and OtherFuel2.
Field: Heat Recovery Maximum Temperature[LINK]
This field sets the maximum temperature that this piece of equipment can produce for heat recovery. The idea behind this field is that the current models do not take temperatures into account for availability and they just pass Q’s around the loop without a temperature limit. This temperature limit puts an upper bound on the recovered heat and limits the max temperatures leaving the component.
As temperatures in the loop approach the maximum temperature, the temperature difference between the entering water and the surfaces in the piece of equipment becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The reduced amount of heat recovered will diminish if the temperature of the loop approach is the maximum temperature, and this will show up in the reporting. This allows the user to set the availability or the quality of the heat recovered for usage in other parts of the system or to heat domestic hot water supply.
The temperature is specified in degrees C.
An IDF example showing how it is used is provided below:
Outputs[LINK]
The output variables that are available for the IC engine generator are:
Generator Produced Electric Power [W][LINK]
Generator Produced Electric Energy [J][LINK]
These outputs are the electric power output from the electric generator. Energy is metered on Cogeneration:ElectricityProduced, ElectricityProduced:Plant, and ElectricityProduced:Facility.
Generator Lube Heat Recovery Rate [W][LINK]
Generator Lube Heat Recovery Energy [J][LINK]
Generator Jacket Heat Recovery Rate [W][LINK]
Generator Jacket Heat Recovery Energy [J][LINK]
Generator Exhaust Heat Recovery Rate [W][LINK]
Generator Exhaust Heat Recovery Energy [J][LINK]
Generator Produced Thermal Rate [W][LINK]
Generator Produced Thermal Energy [J][LINK]
For electric generators with heat recovery these outputs are the components of recoverable energy available. For the IC engine generator, the following heat recovery components are reported: Lube (engine lubricant), Jacket (engine coolant), and Exhaust (engine exhaust). These components are totaled together for Generator Produced Thermal Rate and Generator Produced Thermal Energy reports. Generator Lube Heat Recovery Energy, Generator Jacket Heat Recovery Energy, and Generator Exhaust Heat Recovery Energy are metered on HeatRecovery:EnergyTransfer, EnergyTransfer:Plant, and EnergyTransfer:Facility.
Generator Exhaust Air Temperature [C][LINK]
This is the exhaust temperature leaving the engine.
Generator Heat Recovery Inlet Temperature [C][LINK]
Generator Heat Recovery Outlet Temperature [C][LINK]
Generator Heat Recovery Mass Flow Rate [kg/s][LINK]
These outputs are the heat recovery inlet and outlet temperatures and flow rate for generators with heat recovery.
Generator Fuel HHV Basis Rate [W][LINK]
Generator Fuel HHV Basis Energy [J][LINK]
These outputs are the generator’s fuel energy and use rate. The energy content of the fuel is based on the higher heating value (HHV).
Generator Rate [W] [LINK]
Generator Energy
[J] [LINK]
Generator
Mass Flow Rate [kg/s] [LINK]
If the fuel type is Diesel, then Diesel is shown as the fuel type. They are the diesel fuel input to the electric generator. Consumption is metered on Cogeneration:Diesel, Diesel:Plant, and Diesel:Facility.
If the fuel type is Natural Gas, then Gas is shown as the fuel type. They are the natural gas fuel input to the electric generator. Consumption is metered on Cogeneration:Gas, Gas:Plant, and Gas:Facility.
If the fuel type is Propane, then Propane is shown as the fuel type. They are the propane fuel input to the electric generator. Consumption is metered on Cogeneration:Propane, Propane:Plant, and Propane:Facility.
If the fuel type is Gasoline, then Gasoline is shown as the fuel type. They are the gasoline fuel input to the electric generator. Consumption is metered on Cogeneration:Gasoline, Gasoline:Plant, and Gasoline:Facility.
If the fuel type is FuelOil#1, then FuelOil#1 is shown as the fuel type. They are the fuel oil input to the electric generator. Consumption is metered on Cogeneration:FuelOil#1, FuelOil#1:Plant, and FuelOil#1:Facility.
If the fuel type is FuelOil#2, then FuelOil#2 is shown as the fuel type. They are the fuel oil input to the electric generator. Consumption is metered on Cogeneration:FuelOil#2, FuelOil#2:Plant, and FuelOil#2:Facility.
If the fuel type is OtherFuel1, then OtherFuel1 is shown as the fuel type. They are the fuel oil input to the electric generator. Consumption is metered on Cogeneration:OtherFuel1, OtherFuel1:Plant, and OtherFuel1:Facility.
If the fuel type is OtherFuel2, then OtherFuel2 is shown as the fuel type. They are the fuel oil input to the electric generator. Consumption is metered on Cogeneration:OtherFuel2, OtherFuel2:Plant, and OtherFuel2:Facility.
Generator:CombustionTurbine[LINK]
EnergyPlus has two different models for combustion turbine style generators. This one stems for a model that was originally in the BLAST computer program. A newer model with a different formulation is also available–see the Generator:MicroTurbine input object. The basic combustion-turbine cycle is the Brayton Cycle or open cycle, which consists of an adiabatic compression, constant pressure heating, and adiabatic expansion. The Combustion turbine model uses the electrical load and engine generator size to compute part-load ratios (PLR). Fuel energy input and recoverable lube oil heat are then computed. Finally, the recoverable exhaust heat is calculated.
Combustion turbine generators use performance parameters to compute fuel energy consumption as a function of part-load and ambient (entering) air temperature. Recoverable fuel energy equipment, recoverable lube oil heat/fuel energy input equipment performance, total exhaust heat/fuel energy input equipment, exhaust gas temperature/fuel energy input equipment performance parameters are all specified with a quadratic curve fit.
When the heat recovery curve fits = 0.0, this means that no heat recovery is done on the diesel generator exhaust gas; and no heat recovery is specified.
Inputs[LINK]
Field: Name[LINK]
Unique name to identify this combustion turbine generator.
Field: Rated Power Output[LINK]
The design nominal capacity of the combustion turbine generator in Watts [W].
Field: Electric Circuit Node Name[LINK]
This Named node contains where the electric power is put in the program simulation for use by the electric equipment in the Load Center.
Field: Minimum Part Load Ratio[LINK]
This field contains the minimum allowed operating fraction of full load. The input value must be >=0.0 and <=1.0.
Field: Maximum Part Load Ratio[LINK]
This field contains the maximum allowed operating fraction of full load. The input value must be >0.0 and <=1.0.
Field: Optimum Part Load Ratio[LINK]
This alpha field contains the optimal operating fraction of full load. This is the part load ratio that gives the optimal production of electric power with the least amount of fuel usage.
Field: Part Load Based Fuel Input Curve Name[LINK]
Needs a Curve:Quadratic object to be specified.
Fuel Input = a + b*PLR + c*PLR**2
PLR = Ratio of Generator Load to Rated Power Output. This curve is multiplied to the Temperature Based Fuel Input Curve to determine Fuel Energy In.
Field: Temperature Based Fuel Input Curve Name[LINK]
Needs a Curve:Quadratic object to be specified.
Fuel Input = a + b*AT + c*AT**2 where: AT = Ambient Delta T
Field: Exhaust Flow Curve Name[LINK]
The Total Exhaust Energy Curve is a quadratic equation that needs to be specified by a curve object. Used to calculate the total exhaust heat as a function of part-load ratio.
Field: Part Load Based Exhaust Temperature Curve Name[LINK]
The Exhaust Temperature Curve is a quadratic equation that needs to be specified by a curve object. Used to determine the exhaust gas temperature as a function of part-load ratio.
Field: Temperature Based Exhaust Temperature Curve Name[LINK]
The Exhaust Temperature Curve is a quadratic equation that needs to be specified by a curve object. Used to determine the exhaust gas temperature as a function of part-load ratio.
Field: Heat Recovery Lube Energy Curve Name[LINK]
This alpha field contains the name of the Recovery Lube Heat curve. The curve itself is specified separately using a curve object (see Curve:Quadlinear object). The Recovery Lubricant Heat Curve is a quadratic equation that determines the ratio of recovery lube heat to fuel energy. Used to calculate the recoverable lube oil heat as a function of part-load ratio. The defining equation is:
\[RecoveryLubeHeatToFuelRatio = {C_1} + {C_2}RL + {C_3}R{L^2}\]
where RL is the Ratio of Load to Rated Power Output.
U-Factor Times Area (UA) Curve[LINK]
The UA curve applies to the exhaust gas heat exchanger. The curve is an equation that determines the overall heat transfer coefficient for the exhaust gases with the stack. The heat transfer coefficient ultimately helps determine the exhaust stack temperature. The defining equation is:
\[UAToCapacityRatio = {C_1}GeneratorRatedPowerOutpu{t^{{C_2}}}\]
The following two fields contain the coefficients for the equation.
Field: Coefficient 1 of U-Factor Times Area Curve[LINK]
This numeric field contains the first coefficient for the overall heat transfer coefficient curve.
Field: Coefficient 2 of U-Factor Times Area Curve[LINK]
This numeric field contains the second (exponential) coefficient for the overall heat transfer coefficient curve.
Field: Maximum Exhaust Flow per Unit of Power Output[LINK]
Maximum exhaust flow per unit capacity for diesel engines. The parameter sets an upper limit on exhaust gas flow and exhaust gas heat recovery for diesel engines. Units: kg/sec per kW capacity
Field: Design Minimum Exhaust Temperature[LINK]
This is the design engine stack saturated steam temperature in degrees C.
Field: Design Air Inlet Temperature[LINK]
Design air inlet temperature in degrees C.
Field: Fuel Higher Heating Value[LINK]
This numeric field contains the higher heating value of the fuel used in kJ/kg.
Field: Design Heat Recovery Water Flow Rate[LINK]
Design water volumetric flow rate through heat recovery loop in m3/sec.
Field: Heat Recovery Inlet Node Name[LINK]
This alpha field contains the identifying name for the combustion turbine generator heat recovery side inlet node.
Field: Heat Recovery Outlet Node Name[LINK]
This alpha field contains the identifying name for the combustion turbine generator heat recovery side outlet node.
Field: Fuel Type[LINK]
This alpha field determines the type of fuel that the generator uses. Valid choices are: NaturalGas, PropaneGas, Diesel, Gasoline, FuelOil#1, FuelOil#2, OtherFuel1 and OtherFuel2. The default is NaturalGas.
Field: Heat Recovery Maximum Temperature[LINK]
This field sets the maximum temperature that this piece of equipment can produce for heat recovery. The idea behind this field is that the current models do not take temperatures into account for availability and they just pass Q’s around the loop without a temperature limit. This temperature limit puts an upper bound on the recovered heat and limits the max temperatures leaving the component.
As temperatures in the loop approach the maximum temperature, the temperature difference between the entering water and the surfaces in the piece of equipment becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The reduced amount of heat recovered will diminish if the temperature of the loop approach is the maximum temperature, and this will show up in the reporting. This allows the user to set the availability or the quality of the heat recovered for usage in other parts of the system or to heat domestic hot water supply.
The temperature is specified in degrees C.
Field: Outdoor Air Inlet Node Name[LINK]
This field is optional. It is used to explicitly define an outdoor air node for the inlet for combustion air stream. Defining an outdoor air node here allows using the height-dependent model for outdoor air conditions.
An IDF example showing how it is used is provided below:
Outputs[LINK]
The output variables that are available for the combustion turbine generator are:
All of these outputs, except for the Combustion use outputs, are described above under “Generator:InternalCombustionEngine Outputs.”
Generator Rate
[W] [LINK]
Generator Energy
[J] [LINK]
Generator
Mass Flow Rate [kg/s] [LINK]
These outputs are the fuel input to the electric generator. Consumption is metered on Cogeneration:,
:Plant, and :Facility.
Generator:MicroTurbine[LINK]
MicroTurbine generators are small combustion turbines that produce electricity on a relatively small scale (e.g., 25kW to 500kW). This model uses nominal performance at reference conditions along with several modifier curves to determine electrical power output and fuel use at non-reference conditions. Standby and ancillary power can also be taken into account. Furthermore, energy recovery from exhaust air can be used to heat water. Similar to electrical power output, thermal power (heat recovery) output is calculated using nominal performance at reference conditions with modifier curves to account for variations at non-reference conditions.
The following inputs define the MicroTurbine electric generator. The ElectricLoadCenter:Generators and ElectricLoadCenter:Distribution objects are used to define the availability and control of all electric generators included in the simulation (ref. ElectricLoadCenter:Generators and ElectricLoadCenter:Distribution).
Inputs[LINK]
Field: Name[LINK]
This alpha field specifies a unique user-defined name to identify this generator. This is a required input.
Field: Reference Electrical Power Output[LINK]
This numeric field specifies the full-load electrical power output of the microturbine generator in Watts at reference conditions. The reference conditions are defined via additional input fields for this object (see below). This is a required input, and the value entered in this field must be greater than zero.
Field: Minimum Full Load Electrical Power Output[LINK]
This numeric field specifies the minimum electrical power output in Watts at full-load conditions. The electrical power output of the generator is determined by multiplying the Reference Electrical Power Output by the Electrical Power Function of Temperature and Elevation modifier curve. If the result is less than the numeric value specified in this input field, then the generator’s electrical power output is reset to the minimum full-load value specified in this input field. The value entered in this field must be greater than or equal to zero. If this field is left blank, the default value of 0.0 will be used.
Field: Maximum Full Load Electrical Power Output[LINK]
This numeric field specifies the maximum electrical power output in Watts at full-load conditions. The electrical power output of the generator is determined by multiplying the Reference Electrical Power Output by the Electrical Power Function of Temperature and Elevation Modifier curve. If the result is greater than the numeric value specified in this input field, then the generator’s electrical power output is reset to the maximum full-load value specified in this input field. The value entered in this field must be greater than zero. If this field is left blank, then the value entered for the Reference Electrical Power Output field (above) will be used as the Maximum Full Load Electrical Power Output.
Field: Reference Electrical Efficiency Using Lower Heating Value[LINK]
This numeric field contains the electrical efficiency of the generator at reference conditions, based on the lower heating value of the fuel. The electrical efficiency is the electric power output divided by the fuel energy consumption rate (LHV basis). The reference conditions are defined via additional input fields for this object (see below). This is a required input, and the value entered in this field must be greater than zero and less than or equal to 1.0.
Field: Reference Combustion Air Inlet Temperature[LINK]
This numeric field specifies the reference temperature for the combustion inlet air in degrees Celsius. If this field is left blank, the default value of 15°C will be used.
Field: Reference Combustion Air Inlet Humidity Ratio[LINK]
This numeric field specifies the reference humidity ratio for the combustion inlet air in kgWater/kgDryAir. The value specified for this field must be greater than zero. If this field is left blank, the default value of 0.00638 (kgWater/kgDryAir) will be used.
Field: Reference Elevation[LINK]
This numeric field specifies the reference elevation in meters (relative to sea level). The value specified for this field must be greater than or equal to -300.0 meters. If this field is left blank, the default value of 0.0 meters will be used.
Field: Electrical Power Function of Temperature and Elevation Curve Name[LINK]
This alpha field specifies the name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of electrical power output as a function of the combustion air inlet temperature and elevation. The output of this curve is multiplied by the Reference Electrical Power Output to give the full-load power output at a specific combustion air inlet temperature and elevation (i.e., at values different from the reference conditions). This curve should be normalized to have a value of 1.0 at the reference conditions, and the curve should be valid for the range of inlet air temperatures anticipated for the simulation period and for the actual elevation of the generator.
Field: Electrical Efficiency Function of Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of electrical efficiency as a function of the combustion air inlet temperature. The output of this curve is multiplied by the Reference Electrical Efficiency Using Lower Heating Value to give the full-load electrical efficiency at specific combustion air inlet temperatures (i.e., at inlet air temperatures different from the Reference Combustion Air Inlet Temperature). This curve should be normalized to have a value of 1.0 at the Reference Combustion Air Inlet Temperature, and the curve should be valid for the range of inlet air temperatures anticipated for the simulation period.
Field: Electrical Efficiency Function of Part Load Ratio Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of electrical efficiency as a function of the generator’s part-load ratio (part-load ratio is the actual electrical power output divided by the full-load electrical power output at the current operating conditions). The output of this curve is multiplied by the Reference Electrical Efficiency Using Lower Heating Value and the output of the Electrical Efficiency Function of Temperature modifier curve to give the electrical efficiency at specific part-load and combustion air inlet (temperature) conditions. This curve should be normalized to have a value of 1.0 when the generator’s part-load ratio is 1.0, and the curve should be valid for the range of part-load ratios anticipated for the simulation period.
Field: Fuel Type[LINK]
This choice field specifies the type of fuel used by the generator. Valid fueld types are PropaneGas and NaturalGas. If the field is left blank, the fuel type will be assumed to be NaturalGas.
Field: Fuel Higher Heating Value[LINK]
This numeric field specifies the higher heating value of the fuel used in kJ/kg. The value specified for this field must be greater than zero and greater than the specified Fuel Lower Heating Value. If this field is left blank, the default value of 50,000 kJ/kg will be used.
Field: Fuel Lower Heating Value[LINK]
This numeric field specifies the lower heating value of the fuel used in kJ/kg. The value specified for this field must be greater than zero but less than the specified Fuel Higher Heating Value. If this field is left blank, the default value of 45,450 kJ/kg will be used.
Field: Standby Power[LINK]
This numeric field specifies the standby electric power consumed by the generator in Watts. The standby power is the electrical power consumed by the generator (e.g., air fans and controls) when the generator is available to operate but the generator electrical power output is zero (power output is not being requested by the electric load center). The value specified for this field must be greater than or equal to zero. If this field is left blank, the default value of 0.0 W will be used.
Field: Ancillary Power[LINK]
This numeric field specifies the ancillary electric power consumed by the generator in Watts. The ancillary power is the electrical power consumed by other associated equipment (e.g., external fuel pressurization pumps) when the generator is operating. Specify this input as 0.0 if the Reference Electrical Power Output and Reference Electrical Efficiency Using Lower Heating Value input fields and associated modifier curves reflect the “net” electrical power output from the generator (i.e., ancillary power already deducted from the generator’s gross electrical power output). A value greater than zero indicates that this electrical power is consumed whenever the generator is operating and will be deducted from the generator’s overall electrical power output (Generator Produced Electric Power). The value specified for this field must be greater than or equal to zero. If this field is left blank, the default value of 0.0 W will be used.
Field: Ancillary Power Function of Fuel Input Curve Name[LINK]
This alpha field specifies the name of a quadratic performance curve (ref: Performance Curves) that parameterizes the variation of ancillary power as a function of the generator’s input fuel mass flow rate (kg/s). The output of this curve is multiplied by the ancillary power to give the ancillary power at a specific fuel mass flow rate. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation (i.e., the ancillary power is constant whenever the generator operates).
Field: Heat Recovery Water Inlet Node Name[LINK]
This alpha field specifies the identifying name for the generator’s heat recovery water inlet node.
Field: Heat Recovery Water Outlet Node Name[LINK]
This alpha field specifies the identifying name for the generator’s heat recovery water outlet node.
Field: Reference Thermal Efficiency Using Lower Heat Value[LINK]
This numeric field specifies the thermal efficiency (heat recovery to water) at reference conditions, based on the lower heating value of the fuel. The thermal efficiency is the thermal power output (to water) divided by the fuel energy consumption rate (LHV basis). The reference conditions are defined via additional input fields for this object. This value must be from 0.0 to 1.0. If this field is left blank, the default value of 0.0 will be used.
Field: Reference Inlet Water Temperature[LINK]
This numeric field specifies the reference temperature for the inlet water to the heat recovery heat exchanger in degrees Celsius.
Field: Heat Recovery Water Flow Operating Mode[LINK]
This field is used to choose between different modes of controlling the mass flow rate of water being heated by energy recovered from exhaust air. There are two options available for this field: “PlantControl” or “InternalControl.” The “PlantControl” option indicates that the heat recovery water flow rate through the generator is determined externally (by the wider balance of plant). In this case, the generator will request the Reference Heat Recovery Water Flow Rate whenever it operates but the actual flow rate may be limited by other plant components (e.g., pump). The “InternalControl” option indicates the flow of water is controlled inside the generator based on current operating conditions. For InternalControl, the generator should (probably) include a bypass branch when connecting to the plant loop.
Field: Reference Heat Recovery Water Flow Rate[LINK]
This numeric field is the reference heat recovery (volumetric) water flow rate in cubic meters per second. Entered values must be greater than zero.
Field: Heat Recovery Water Flow Rate Function of Temperature and Power Curve Name[LINK]
This alpha field specifies the name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of heat recovery water flow rate as a function of the inlet water temperature and net electrical power output. This field is only used if the Heat Recovery Water Flow Operating Mode is ‘InternalControl’. The output of this curve is multiplied by the Reference Heat Recovery Water Flow Rate to give the water flow rate at the specific inlet water temperature and net power operating conditions. This curve should be normalized to have a value of 1.0 at the reference conditions, and the curve should be valid for the range of inlet water temperatures and net electrical power output anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Thermal Efficiency Function of Temperature and Elevation Curve Name[LINK]
This alpha field specifies the name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of thermal efficiency as a function of the combustion air inlet temperature and elevation. The output of this curve is multiplied by the Reference Thermal Efficiency Using Lower Heating Value to give the full-load thermal efficiency at a specific combustion air inlet temperature and elevation (i.e., at values different from the reference conditions). This curve should be normalized to have a value of 1.0 at the reference conditions, and the curve should be valid for the range of inlet air temperatures anticipated for the simulation period and for the actual elevation of the generator. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Heat Recovery Rate Function of Part Load Ratio Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of heat recovery to water (thermal power output) as a function of the generator’s part-load ratio (part-load ratio is the actual electrical power output divided by the full-load electrical power output at the current operating conditions). The output of this curve is multiplied by the steady-state heat recovery at the current combustion inlet air temperature and elevation to give the heat recovery rate (thermal power output) at specific part-load operating conditions. This curve should be normalized to have a value of 1.0 when the generator’s part-load ratio is 1.0, and the curve should be valid for the range of part-load ratios anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Heat Recovery Rate Function of Inlet Water Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic performance curve (ref: Performance Curves) that parameterizes the variation of heat recovery to water (thermal power output) as a function of the inlet water temperature. The output of this curve is multiplied by the steady-state heat recovery at the current combustion inlet air temperature and elevation to give the heat recovery rate (thermal power output) at non-reference inlet water conditions. This curve should be normalized to have a value of 1.0 at the Reference Inlet Water Temperature, and the curve should be valid for the range of inlet water temperatures anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Heat Recovery Rate Function of Water Flow Rate Curve Name[LINK]
This alpha field specifies the name of a quadratic performance curve (ref: Performance Curves) that parameterizes the variation of heat recovery to water (thermal power output) as a function of the heat recovery water flow rate. The output of this curve is multiplied by the steady-state heat recovery at the current combustion inlet air temperature and elevation to give the heat recovery rate (thermal power output) at non-reference heat recovery water flow rates. This curve should be normalized to have a value of 1.0 at the Reference Heat Recovery Water Flow Rate, and the curve should be valid for the range of water flow rates anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Minimum Heat Recovery Water Flow Rate[LINK]
This numeric field specifies the minimum (volumetric) water flow rate through the heat recovery heat exchanger in cubic meters per second. The minimum input value is 0.0, and a value of 0.0 is assumed if this field is left blank.
Field: Maximum Heat Recovery Water Flow Rate[LINK]
This numeric field specifies the maximum (volumetric) water flow rate through the heat recovery heat exchanger in cubic meters per second. The minimum input value for this field is 0.0, and a value of 0.0 is assumed if this field is left blank. The maximum heat recovery water flow rate must be greater than or equal to the minimum heat recovery water flow rate.
Field: Maximum Heat Recovery Water Temperature[LINK]
This field sets the maximum water temperature, in degrees Celsius, that this generator can produce via heat recovery. This temperature limit puts an upper bound on the recovered heat and limits the max temperatures leaving the component.
As temperatures in the water loop approach this maximum temperature, the temperature difference between the entering water and the surfaces in generator’s heat recovery heat exchanger becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The amount of heat recovered will diminish if the inlet water temperature approaches the maximum temperature, and this will show up in the reporting.
Field: Combustion Air Inlet Node Name[LINK]
This alpha field specifies the name of the combustion air inlet node. If a node name is specified, this node must be an outdoor air node and must also be specified elsewhere in the input (ref: OutdoorAir:Node and OutdoorAir:NodeList). If this field is left blank, the combustion air inlet conditions are assumed to be the outdoor weather conditions used for the simulation.
Field: Combustion Air Outlet Node Name[LINK]
This alpha field specifies the name of the combustion air outlet node.
Field: Reference Exhaust Air Mass Flow Rate[LINK]
This numeric field is the reference exhaust air mass flow rate in kilograms per second. Entered values must be greater than zero.
Field: Exhaust Air Flow Rate Function of Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of exhaust air flow rate as a function of the combustion air inlet temperature. The output of this curve is multiplied by the Reference Exhaust Air Mass Flow Rate to give the exhaust air mass flow rate at non-reference combustion air inlet temperatures. This curve should be normalized to have a value of 1.0 at the Reference Combustion Air Inlet Temperature, and the curve should be valid for the range of inlet air temperatures anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Exhaust Air Flow Rate Function of Part Load Ratio Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of exhaust air flow rate as a function of the generator’s part-load ratio (part-load ratio is the actual electrical power output divided by the full-load electrical power output at the current operating conditions). The output of this curve is multiplied by the Reference Exhaust Air Mass Flow Rate to give the exhaust air mass flow rate at specific part-load operating conditions. This curve should be normalized to have a value of 1.0 when the generator’s part-load ratio is 1.0, and the curve should be valid for the range of part-load ratios anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Nominal Exhaust Air Outlet Temperature[LINK]
This numeric field is the exhaust air outlet temperature at nominal (reference) conditions in degrees Celsius.
Field: Exhaust Air Temperature Function of Temperature Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of exhaust air outlet temperature as a function of the combustion air inlet temperature. The output of this curve is multiplied by the Nominal Exhaust Air Outlet Temperature to give the exhaust air temperature at non-reference combustion air inlet temperatures. This curve should be normalized to have a value of 1.0 at the Reference Combustion Air Inlet Temperature, and the curve should be valid for the range of inlet air temperatures anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
Field: Exhaust Air Temperature Function of Part Load Ratio Curve Name[LINK]
This alpha field specifies the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of exhaust air outlet temperature as a function of the generator’s part-load ratio (part-load ratio is the actual electrical power output divided by the full-load electrical power output at the current operating conditions). The output of this curve is multiplied by the Nominal Exhaust Air Outlet Temperature to give the exhaust air temperature at specific part-load operating conditions. This curve should be normalized to have a value of 1.0 when the generator’s part-load ratio is 1.0, and the curve should be valid for the range of part-load ratios anticipated for the simulation period. If this field is left blank, the model assumes that the modifier curve is 1.0 for the entire simulation.
An example IDF showing how this object is used is provided below:
Outputs[LINK]
The output variables that are available for the microturbine generator are:
Generator Produced Electric Power [W][LINK]
This output variable is the average electric power produced by the generator in Watts for the timestep being reported. This is the “net” electric power produced, accounting for ancillary electric power consumed during generator operation.
Generator Produced Electric Energy [J][LINK]
This output variable is the electric energy produced by the generator in Joules for the timestep being reported. This output is also added to a meter with Resource Type = ElectricityProduced, End Use Key = Cogeneration, Group Key = Plant (Ref. Output:Meter objects). This is the “net” electric energy produced, accounting for ancillary electric consumption during generator operation.
Generator LHV Basis Electric Efficiency [][LINK]
This output variable is the average electric efficiency of the generator (lower heating value basis) for the timestep being reported. The electric efficiency is the Generator Produced Electric Power in Watts divided by the generator’s fuel energy consumption rate in Watts (lower heating value basis).
Generator HHV
Basis Rate [W] [LINK]
This output variable is the average fuel-specific energy consumption rate of the electric generator in Watts (higher heating value basis) for the timestep being reported. is the name of the fuel used by this electric
generator. can be one of the following: NaturalGas
(=> ‘Gas’) or PropaneGas (=>‘Propane’).
Generator Fuel HHV Basis Rate [W][LINK]
This output variable is the average fuel energy consumption rate of the electric generator in Watts (higher heating value basis) for the timestep being reported. The output variable name is non-fuel specific.
Generator
HHV Basis Energy [J] [LINK]
This output variable is the fuel-specific energy consumption of the electric generator in Joules (higher heating value basis) for the timestep being reported. This output is also added to a meter with Resource Type =, End Use Key = Cogeneration, Group Key = Plant
(Ref. Output:Meter
objects). is the name of the fuel used by this
electric generator. can be one of the following:
NaturalGas (=> ‘Gas’) or PropaneGas (=>‘Propane’).
Generator Fuel HHV Basis Energy [J][LINK]
This output variable is the fuel energy consumption of the electric generator in Joules (higher heating value basis) for the timestep being reported. The output variable name is non-fuel specific.
Generator
Mass Flow Rate [kg/s] [LINK]
This output variable is the average mass flow rate of fuel being consumed by the electric generator in kg/s for the timestep being reported. is the name of the fuel
used by this electric generator. can be one of the
following: Natural Gas (=> ‘Gas’) or Propane Gas
(=>‘Propane’).
Generator Standby Electric Power [W][LINK]
This output variable is the average standby electric power consumed by the generator in Watts for the timestep being reported. Standby power is electrical power consumed by the generator (e.g., air fans and controls) when the generator is available to operate but the generator electrical power output is zero (power output is not being requested by the electric load center). This output variable is only produced when the user enters a value greater than 0.0 for the input field Standby Power.
Generator Standby Electric Energy [J][LINK]
This output variable is the standby electric energy consumption for the generator in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cogeneration, Group Key = Plant (Ref. Output:Meter objects). This output variable is only produced when the user enters a value greater than 0.0 for the input field Standby Power.
Generator Ancillary Electric Power [W][LINK]
This output variable is the average ancillary electric power consumed by the generator in Watts for the timestep being reported. Ancillary power is the electrical power consumed by other associated equipment (e.g., external fuel pressurization pumps) when the generator is operating. This output variable is only produced when the user enters a value greater than 0.0 for the input field Ancillary Power.
Generator Ancillary Electric Energy [J][LINK]
This output variable is the ancillary electric energy consumption for the generator in Joules for the timestep being reported. This energy consumption is already deducted from the output variable Generator Produced Electric Energy (“net” electric energy produced by the generator). This output variable is only produced when the user enters a value greater than 0.0 for the input field Ancillary Power.
Generator Produced Thermal Rate [W][LINK]
This output variable is the average thermal power produced (i.e., exhaust energy recovery to heat water) in Watts for the timestep being reported.
Generator Produced Thermal Energy [J][LINK]
This output variable is the thermal energy produced (i.e., exhaust energy recovery to heat water) in Joules for the timestep being reported. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatRecovery, Group Key = Plant (Ref. Output:Meter objects).
Generator Thermal Efficiency LHV Basis [-][LINK]
This output variable is the average thermal efficiency of the generator (lower heating value basis) for the timestep being reported. The thermal efficiency is the Generator Produced Thermal Rate in Watts divided by the generator’s fuel energy consumption rate in Watts (lower heating value basis).
Generator Heat Recovery Inlet Temperature [C][LINK]
This output variable is the average heat recovery inlet water temperature in degrees Celsius for the timestep being reported.
Generator Heat Recovery Outlet Temperature [C][LINK]
This output variable is the average heat recovery outlet water temperature in degrees Celsius for the timestep being reported.
Generator Heat Recovery Water Mass Flow Rate [kg/s][LINK]
This output variable is the average heat recovery water mass flow rate in kilograms per second for the timestep being reported.
Generator Exhaust Air Mass Flow Rate [kg/s][LINK]
This is the mass flow rate of exhaust leaving the generator. This output is available when the model input is setup for exhaust conditions.
Generator Exhaust Air Temperature [C][LINK]
This is the temperature of exhaust leaving the generator. This output is available when the model input is setup for exhaust conditions.
Generator:MicroCHP[LINK]
This object is used to model small-scale combined heat and power (micro CHP) electric generators using the model developed by IEA/ECBCS Annex 42 - see www.cogen-sim.net. The model was developed for both internal combustion and Stirling cycle engines, but might be used for other types of residential CHP devices.
Note that unlike other component models in EnergyPlus, this model is not normalized. Therefore, performance coefficients developed for one type and capacity of CHP device cannot be used for a device with a different capacity.
This model is an empirical, curve fit model. This object describes the connections to the rest of the building model and includes a reference to another object called Generator:MicroCHP:NonNormalizedParameters that provides the operating characteristics.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the residential CHP device.
Field: Performance Parameters Name[LINK]
This field contains the name of a Generator:MicroCHP:NonNormalizedParameters object defined elsewhere in the input.
Field: Zone Name[LINK]
This field contains the name of the thermal zone where the CHP device is located in the model. If the device is outdoors, or you do not want skin losses to be added to a zone, then leave this field blank.
Field: Cooling Water Inlet Node Name[LINK]
This field provides the name of a node that is the inlet to the CHP device. The node should be on the plant loop that will receive the heat from the residential CHP unit. This inlet serves as the cooling water for the CHP device.
Field: Cooling Water Outlet Node Name[LINK]
This field provides the name of a node that is the outlet to the CHP device. The node should be on the plant loop that will receive the heat from the residential CHP unit. This outlet serves as the exit of the cooling water leaving the CHP unit.
Field: Air Inlet Node Name[LINK]
The name of an air node that supplies the CHP unit with air for use inside the generator.
Field: Air Outlet Node Name[LINK]
The name of an air node that receives the exhaust from the CHP unit.
Field: Generator Fuel Supply Name[LINK]
This field contains the name of a Generator:FuelSupply object defined elsewhere in the input file.
Field: Availability Schedule Name[LINK]
This field contains the name of a schedule used to control whether or not the unit is available. It is “available” any time the value is greater than zero. If it is available, it may consume standby power at times when there is no request for power from the Electric Load Center. If it is not available (schedule value = 0.0) then the CHP unit is in a completely off “mode” and will not consume standby power. If this field is blank, the schedule has values of 1 for all time periods.
An example IDF showing how this object is used is provided below:
Generator:MicroCHP:NonNormalizedParameters[LINK]
This object is referenced by a Generator:MicroCHP object and provides the non-normalized parameters for the MicroCHP generator model.
Inputs[LINK]
Field: Name[LINK]
Unique name to identify this set of parameter data.
Field: Maximum Electric Power[LINK]
This is the size of the CHP unit in terms of the maximum electrical power it can produce [W]. If the electric load center requests more power than this maximum, then the unit will restrict its output to this level.
Field: Minimum Electric Power[LINK]
This is the size of the CHP unit in terms of the minimum electrical power it can produce [W]. If the electric load center requests less power than this minimum, then the unit will hold its output to this level.
Field: Minimum Cooling Water Flow Rate[LINK]
This is the minimum flow rate of cooling water that must be available for the unit to operate [kg/s]. If the plant loop is not providing this flow of water, the unit will shut down to protect it from overheating.
Field: Maximum Cooling Water Temperature[LINK]
This is the maximum temperature of cooling water inlet or outlet that can occur without the unit shutting down to protect from overheating [°C].
Field: Electrical Efficiency Curve Name[LINK]
This is the name of Curve:Triquadratic object that defines the steady-state net electrical efficiency. The electrical efficiency, \({\eta _e}\), is a function of the cooling water mass flow rate, \({\dot m_{cw}}\), the temperature of the cooling water at the inlet, \({T_{cw}}\), the steady-state net electrical power produced, \({P_{net,ss}}\).
\[{\eta _e} = f\left( {{P_{net,ss}},{{\dot m}_{cw}},{T_{cw}}} \right)\]
The associated Curve:Triquadratic object should be defined with the independent variables \({P_{net,ss}},{\dot m_{cw}},{T_{cw}}\) corresponding to x, y, and z, respectively.
Field: Thermal Efficiency Curve Name[LINK]
This is the name of a Curve:Triquadratic object that defines the steady-state net thermal efficiency. The thermal efficiency, \({\eta _q}\), is a function of the cooling water mass flow rate, \({\dot m_{cw}}\), the temperature of the cooling water at the inlet, \({T_{cw}}\), the steady-state net electrical power produced, \({P_{net,ss}}\).
\[{\eta _q} = f\left( {{P_{net,ss}},{{\dot m}_{cw}},{T_{cw}}} \right)\]
The associated Curve:Triquadratic object should be defined with the independent variables \({P_{net,ss}},{\dot m_{cw}},{T_{cw}}\) corresponding to x, y, and z, respectively.
Field: Cooling Water Flow Rate Mode[LINK]
This field is used to choose between different modes of controlling the mass flow rate of cooling water. There are two options available for this field: “PlantControl” or “InternalControl.” The “PlantControl” option indicates that the cooling water flow rate through the CHP device is determined externally (by the wider balance of plant). The “InternalControl” option indicates the flow of cooling water is controlled inside the CHP device (e.g., like an automobile’s thermostat).
For internal control, the following field is used to define a Biquadratic curve that will determine the cooling water flow rate. For internal control, the CHP device should (probably) include a bypass branch when connecting to the plant loop.
Field: Cooling Water Flow Rate Curve Name[LINK]
This field contains the name of a Curve:Biquadratic object that defines the mass flow rate of cooling water, \({\dot m_{cw}}\). This field is only used if the prior field is set to “InternalControl.” The mass flow of cooling water is a function of steady-state power, \({P_{net,ss}}\), and the inlet temperature of the cooling water, \({T_{cw}}\). The associated Curve:Biquadratic should be defined with the independent variables \({P_{net,ss}}\) and \({T_{cw}}\) corresponding to x and y, respectively.
Field: Air Flow Rate Curve Name[LINK]
This is the name of a Curve:Quadratic object that defines the steady state air flow into the CHP device as a function of the mass flow rate of fuel.
Field: Maximum Net Electrical Power Rate of Change[LINK]
This field contains input on the limits for how fast the generator can ramp up or down in terms of the net electrical power.
Field: Maximum Fuel Flow Rate of Change[LINK]
This field contains input on the limits for how fast the generator can ramp up or down in terms of the fuel flow rates.
Field: Heat Exchanger U-Factor Times Area Value[LINK]
This field describes the effective UA value for the heat exchanger that transfers heat from the generator to the cooling water.
Field: Skin Loss U-Factor Times Area Value[LINK]
This field describes the effective UA value for the heat transfer from the generator to the surrounding air.
Field: Skin Loss Radiative Fraction[LINK]
This field describes the split between thermal radiation and thermal convection for the heat losses from the skin of the generator.
Field: Aggregated Thermal Mass of Energy Conversion Portion of Generator[LINK]
This field describes the aggregated thermal mass of the energy conversion portion of the generator. This includes the engine block in an internal combustion engine.
Field: Aggregated Thermal Mass of Heat Recovery Portion of Generator[LINK]
This field describes the aggregated thermal mass of the heat recovery portion of the generator. This includes the encapsulated cooling water and heat exchanger shell in immediate thermal contact.
Field: Standby Power[LINK]
This field describes the power used by the CHP unit’s control systems while in standby operation. Standby operation mode occurs whenever the unit is available but not being called upon to produce power. Power is entered as a positive value but indicates negative generation.
Field: Warm Up Mode[LINK]
This field is used to choose between different modes of controlling the warm up characteristics. Residential CHP units such as Stirling engines have different warm up characteristics than internal combustion engines. There are two warm up modes available: “NominalEngineTemperature” or “TimeDelay.” If the former mode is input in this field, then the next three fields are used to model warm up. If the later mode is input, then the fourth field below is used to model warm up.
Field: Warm Up Fuel Flow Rate Coefficient[LINK]
This field describes the value for the coefficient used to determine the rate of fuel flow during warm up. The coefficient, kf, is used in the following relation,
\[{\dot m_{fuel,warm - up}} = {\dot m_{fuel,ss - \max }} + {k_f}{\dot m_{fuel,ss - \max }}\left( {\frac{{{T_{eng,nom}} - {T_{room}}}}{{{T_{eng}} - {T_{room}}}}} \right)\]
Field: Nominal Engine Operating Temperature[LINK]
This field describes the nominal engine temperature during normal, steady-state operation, \({T_{eng,nom}}\) [°C].
Field: Warm Up Power Coefficient[LINK]
This field describes the value for the coefficient used to determine the rate of power production during warm up. The coefficient kp is used in the following relation,
\[{P_{net,warm - up}} = {P_{\max }}{k_p}\left( {\frac{{{T_{eng}} - {T_{room}}}}{{{T_{eng,nom}} - {T_{room}}}}} \right)\]
Field: Warm Up Fuel Flow Rate Limit Ratio[LINK]
This field is used to describe a limit to the fuel flow rate during warm up. The limit is a ratio multiplied by the maximum fuel flow rate during normal operation (corresponding to the fuel flow for maximum electrical power). If the warm up operating fuel flow rate is twice the steady state fuel flow at maximum power, then a value of 2.0 would be entered in this field. This field is only used with the nominal engine temperature warm up mode and is intended for Stirling engines.
Field: Warm Up Delay Time[LINK]
This field is used to model the warm up operation when the warm up mode is “TimeDelay.”
Enter the time between activation and power generation in seconds.
Field: Cool Down Power[LINK]
This field describes the power used by the CHP unit’s ancillary systems while in cool down operation mode. Cool down operation mode occurs whenever the unit has recently been told to stop producing power. Power here is consumed and entered as a positive value that indicates negative generation. For example, a component such as a cooling fan might continue to run during cool down.
Field: Cool Down Delay Time[LINK]
This field is used to describe the time it takes for the CHP unit to cool off and complete the cool down operation. Enter the time between deactivation and the end of a cool down period in seconds.
Field: Restart Mode[LINK]
This field is used to choose between two different control situations for the cool down operation. The two options for this field are “MandatoryCoolDown” and “OptionalCoolDown.” The former is used to direct the model to complete the entire cool down period before the generator can subsequently enter warm up mode. The latter directs the model to allow immediately switching to warm up mode, if power is requested before the cool down period is completed.
An example IDF showing how this object is used is provided below:
Outputs[LINK]
Generator Off Mode Time [s][LINK]
This report is the amount of time the generator spent in “Off” mode in seconds.
Generator Standby Mode Time [s][LINK]
This report is the amount of time the generator spent in “Stand By” mode in seconds.
Generator Warm Up Mode Time [s][LINK]
This report is the amount of time the generator spent in “Warm Up” mode in seconds.
Generator Normal Operating Mode Time [s][LINK]
This report is the amount of time the generator spent in “Normal Operating” mode in seconds.
Generator Cool Down Mode Time [s][LINK]
This report is the amount of time the generator spent in “Cool Down” mode in seconds.
Generator Produced Electric Power [W][LINK]
This report is the net electrical power produced by the generator in watts.
Generator Produced Electric Energy [J][LINK]
This report is the net electrical energy produced by the generator in joules. This output variable is also put on the meter for on-site production.
Generator Electric Efficiency [ ][LINK]
This is the result for electrical efficiency.
Generator Thermal Efficiency [ ][LINK]
This is the result for thermal efficiency.
Generator Gross Input Heat Rate [W][LINK]
This is the gross rate of heat input (from fuel consumption) into the engine control volume.
Generator Steady State Engine Heat Generation Rate [W][LINK]
This is an interim value in the dynamic thermal calculation that describes the steady-state heat generation in the engine.
Generator Engine Heat Exchange Rate [W][LINK]
This is the rate of heat transfer within the generator between the engine section and the heat recovery section, in Watts.
Generator Produced Thermal Rate [W][LINK]
Generator Produced Thermal Energy [J][LINK]
These are the rate and energy of thermal heat transferred from the engine to the heat recovery fluid in the coolant control volume.
Generator Air Mass Flow Rate [kg/s][LINK]
This is the rate of air flow thru the engine on a mass basis.
Generator Fuel Molar Flow Rate [kmol/s][LINK]
This is the rate of fuel flow thru the engine on a molar basis.
Generator Fuel Mass Flow Rate [kg/s][LINK]
This is the rate of fuel flow thru the engine on a mass basis.
Generator Engine Temperature [C][LINK]
This is the model result for engine temperature in C. This is the lumped temperature for the engine control volume.
Generator Coolant Inlet Temperature [C][LINK]
This is the temperature of the inlet water used for heat recovery. It is determined by the balance of plant connected to the generator.
Generator Coolant Outlet Temperature [C][LINK]
This report is the model prediction for the leaving temperature of water used for heat recovery. If there is no flow this is the modeled prediction for the mass of cooling water in contact with the engine.
Generator Fuel HHV Basis Energy [J][LINK]
This is the energy used by the cogeneration device in terms of higher heating value in joules. This is the output variable is also put on the meter for natural gas.
Generator Fuel HHV Basis Rate [W][LINK]
This is the rate of fuel energy use by the cogeneration device in terms of higher heating value in watts.
Generator Fuel LHV Basis Energy [J][LINK]
This is the fuel energy used by the cogeneration device in terms of lower heating value in joules.
Generator Fuel LHV Basis Rate [W][LINK]
This is the rate of fuel energy use by the cogeneration device in terms of lower heating value in watts
Generator Zone Sensible Heat Transfer Rate [W][LINK]
Rate of heat gain to zone from cogeneration unit.
Generator Zone Sensible Heat Transfer Energy [J][LINK]
Heat gains to zone from cogeneration unit.
Generator Zone Convection Heat Transfer Rate [W][LINK]
Portion of rate of heat gain to zone in the form of surface convection heat transfer.
Generator Zone Radiation Heat Transfer Rate [W][LINK]
Portion of heat gains to zone in the form of surface radiation heat transfer (to other surfaces in zone).
Generator:FuelCell[LINK]
This object is used to model small Fuel Cell (FC) generators. IEA/ECBCS Annex 42 - see www.cogen-sim.net, developed the FC model implemented in EnergyPlus. The model can be used for two general types of fuel cells, solid oxide fuel cells (SOFC) and proton exchange membrane fuel cells (PEMFC). Warning! This is a complicated model, intended primarily for research. Because fuel cells for cogeneration (producing both heat and electricity) are not yet a mature product for building systems, the input data for this model are extremely difficult to obtain. However, the model is designed to allow investigating the relative implications of a broad array of subsystems and interactions with the building.
There should be one Generator:FuelCell object for each individual FC generator in the model. Multiple fuel cell generators can be included in a given simulation. Because there are a large number of inputs to the FC model and numerous, somewhat separable subsystems within a fuel cell, the EnergyPlus input objects have been organized into a number of separate input objects. This object simply refers to the names of all the other input objects that provide the input details for individual subsystems within the fuel cell cogeneration device. The following figure diagrams these separate subsystems. (not shown is an optional stack cooler with separate connections to heat recovery water loop and surrounding zone air).
Note that the FC model is formulated using the Lower Heating Value (LHV) of the fuel, whereas most other parts of EnergyPlus use the Higher Heating Value (HHV). LHV has important advantages over HHV in the context of the quality of heat recovered. While model coefficients for input performance descriptions are to be based on LHV, energy consumption and tariff calculations are also reported on HHV basis when using this model.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell.
Field: Power Module Name[LINK]
This field contains the name of a Generator:FuelCell:PowerModule input object.
Field: Air Supply Name[LINK]
This field contains the name of a Generator:FuelCell:AirSupply input object.
Field: Fuel Supply Name[LINK]
This field contains the name of a Generator:FuelSupply input object.
Field: Water Supply Name[LINK]
This field contains the name of a Generator:FuelCell:WaterSupply input object.
Field: Auxiliary Heater Name[LINK]
This field contains the name of a Generator:FuelCell:AuxiliaryHeater input object.
Field: Heat Exchanger Name[LINK]
This field contains the name of a Generator:FuelCell:ExhaustGasToWaterHeatExchanger input object.
Field: Electrical Storage Name[LINK]
This field contains the name of a Generator:FuelCell:ElectricalStorage input object.
Field: Inverter Name[LINK]
This field contains the name of a Generator:FuelCell:Inverter input object.
Field: Stack Cooler Name[LINK]
This field contains the name of a Generator:FuelCell:StackCooler input object. This is optional. The presence of a stack cooler distinguishes between SOFC and PEMFC with PEMFC operating at lower temperatures and requiring a separate subsystem to maintain stack temperatures.
An example input data file (IDF) entry for this object is provided below:
Outputs[LINK]
The following output variables are available for the fuel cell model.
Generator Produced Electric Power [W][LINK]
This report is the net electrical power produced by the generator in watts.
Generator Produced Electric Energy [J][LINK]
This report is the net electrical energy produced by the generator in joules. This output variable is also put on the meter for on-site production.
Generator Produced Thermal Rate [W][LINK]
Generator Produced Thermal Energy [J][LINK]
These are the rate and energy of thermal heat transferred from the engine to the heat recovery fluid in the coolant control volume.
Generator Fuel HHV Basis Energy [J][LINK]
This is the energy used by the cogeneration device in terms of higher heating value in joules. This is the output variable is also put on the meter for natural gas.
Generator Fuel HHV Basis Rate [W][LINK]
This is the rate of fuel energy use by the cogeneration device in terms of higher heating value in watts.
Generator Fuel LHV Basis Energy [J][LINK]
This is the fuel energy used by the cogeneration device in terms of lower heating value in joules.
Generator Fuel Consumption Rate LHV Basis [W][LINK]
This is the rate of fuel energy use by the cogeneration device in terms of lower heating value in watts.
Generator Zone Sensible Heat Transfer Rate [W][LINK]
This variable provides the results for the total rate of skin losses from the fuel cell to the surrounding zone.
Generator Zone Sensible Heat Transfer Energy [J][LINK]
This variable provides the results for the total energy in skin losses from the fuel cell to the surrounding zone.
Generator Zone Convection Heat Transfer Rate [W][LINK]
This variable provides the results for the rate of skin losses in the form of surface convection heat transfer from the fuel cell to the surrounding zone.
Generator Zone Radiation Heat Transfer Rate [W][LINK]
This variable provides the results for the rate of skin losses in the form of radiation heat transfer from the fuel cell to the surrounding zone.
Using the FC model with DisplayAdvancedReportVariables (see Diagnostics object or use of operating system’s environment variables) makes the following output variables available as listed in the RDD file. There are a large number of output variables that provide access to the inner workings of the model and individual subsystems that are not likely to be useful for the average user.
Generator Air Inlet Temperature [C][LINK]
This variable provides the temperature of air supplied to the FC.
Generator Power Module Entering Air Temperature [C][LINK]
This variable provides the temperature of the air supplied to the power module after it has gone through the blower and received any heat recovered from other subsystems.
Generator Air Molar Flow Rate [kmol/s][LINK]
This variable provides the results for \({\dot N_{air}}\), the flow rate of air into the FC.
Generator Power Module Entering Air Enthalpy [W][LINK]
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i} \cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]} \right)} _{air}}\), which is the enthalpy flow in the air stream entering the power module relative to 25ºC.
Generator Blower Electric Power [W][LINK]
This variable provides the results for \({P_{blower - el}}\), which is the electrical power used by the air supply blower.
Generator Blower Electric Energy [J][LINK]
This variable provides the results for the energy used by the air supply blower. It is also added to the appropriate meters.
Generator Blower Skin Heat Loss Rate [W][LINK]
This variable provides the results for \({q_{blower - heat - loss}}\), which is the rate of energy “lost” to the surroundings.
Generator Fuel Inlet Temperature [C][LINK]
This variable provides the temperature of the fuel supplied to the FC.
Generator Power Module Entering Fuel Temperature [C][LINK]
This variable provides the temperature of the fuel supplied to the power module after it has gone through the compressor.
Generator Fuel Molar Flow Rate [kmol/s][LINK]
This variable provides the results for \({\dot N_{fuel}}\), which is the flow rate of fuel into the FC.
Generator Power Module Entering Fuel Enthalpy [W][LINK]
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i} \cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]} \right)} _{fuel}}\), which is the enthalpy flow in the fuel stream entering the power module relative to 25ºC.
Generator Fuel Compressor Electric Power [W][LINK]
This variable provides the results for \({P_{comp - el}}\), which is the electrical power used by the fuel supply compressor.
Generator Fuel Compressor Electric Energy [J][LINK]
This variable provides the results for the energy used by the fuel supply compressor. It is also added to the appropriate meters.
Generator Fuel Compressor Skin Heat Loss Rate [W][LINK]
This variable provides the results for the rate of energy “lost” to the surroundings.
Generator Fuel Reformer Water Inlet Temperature [C][LINK]
This variable provides the temperature of the water supplied to the FC for reforming.
Generator Power Module Entering Reforming Water Temperature [C][LINK]
This variable provides the temperature of the water supplied to the power module after it has gone through the pump.
Generator Fuel Reformer Water Molar Flow Rate [kmol/s][LINK]
This variable provides the results for \({\dot N_{water}}\), which the flow rate of reforming water into the FC.
Generator Fuel Reformer Water Pump Electric Power [W][LINK]
This variable provides the results for \({P_{pump - el}}\), which is the electrical power used by the water pump.
Generator Fuel Reformer Water Pump Electric Energy [J][LINK]
This variable provides the results for energy used by the water pump. It is also added to the appropriate meters.
Generator Power Module Entering Reforming Water Enthalpy [W][LINK]
This variable provides the results for \({\dot H_{liq - water}}\) which is the enthalpy flow of the water stream entering the power module relative to 25ºC.
Generator Product Gas Temperature [C][LINK]
This variable provides the results for the temperature of the product gas stream leaving the fuel cell power module.
Generator Product Gas Enthalpy [W][LINK]
This variable provides the results for \({\sum\limits_i {\left( {{{\dot N}_i} \cdot \left[ {{{\hat h}_i} - {\Delta _f}\hat h_i^0} \right]} \right)} _{FCPM - cg}}\), which is the enthalpy flow in the product gas stream leaving the power module relative to 25ºC.
Generator Product Gas Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of all the product gases leaving the fuel cell power module.
Generator Product Gas Ar Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the argon gas leaving the fuel cell power module.
Generator Product Gas CO2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the carbon dioxide gas leaving the fuel cell power module.
Generator Product Gas H2O Vapor Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the water gas leaving the fuel cell power module.
Generator Product Gas N2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the nitrogen gas leaving the fuel cell power module.
Generator Product Gas O2 Molar Flow Rate [kmol/s][LINK]
This variable provides the results for the flow rate of the oxygen gas leaving the fuel cell power module.
Generator Inverter Loss Power [W][LINK]
This variable provides the results for the power losses associated with inefficiencies in the inverter.
Generator Produced DC Electric Power [W][LINK]
This variable provides the results for \({P_{el}}\), which is the net DC electrical power produced by the fuel cell power module.
Generator DC Power Efficiency [ ][LINK]
This variable provides the results for \({\varepsilon _{el}}\), which is the electrical efficiency of the fuel cell power module.
Generator Electric Storage Charge State [J][LINK]
This variable provides the results for state of charge of the electrical storage device inside the fuel cell. Although the units are Joules, this is a state variable and is reported as an average rather than a sum.
Generator Produced DC Electric Power [W][LINK]
This variable provides the rate at which power was stored into the fuel cell’s electrical storage subsystem.
Generator DC Storage Charging Energy [J][LINK]
This variable provides the energy stored into the fuel cell’s electrical storage subsystem.
Generator DC Storage Discharging Power [W][LINK]
This variable provides the rate at which power was drawn from the fuel cell’s electrical storage subsystem.
Generator DC Storage Discharging Energy [J][LINK]
This variable provides the energy drawn from the fuel cell’s electrical storage subsystem.
Generator Ancillary AC Electric Power [W][LINK]
This variable provides the results for \({P_{el,ancillaries - AC}}\), which is the rate at which ancillary devices within the power module use electricity supplied to the fuel cell by an external source.
Generator Ancillary AC Electric Energy [J][LINK]
This variable provides the results for the energy used by AC ancillaries. It is also added to the appropriate meters.
Generator Fuel Cell Model Iteration Count [ ][LINK]
This variable provides information on the numerical method used to calculate the FC model. EnergyPlus uses a sequential substitution iterative algorithm to solve the main heat balance equation for the FC model. This output variable indicates the number of iterations needed to converge.
Generator Regula Falsi Iteration Count [ ][LINK]
This variable provides information on the numerical method used to calculate product gas temperature as a function of the product gas’s enthalpy. A Regula Falsi numerical method is used to invert the Shomate equation for enthalpy as a function of temperature. This output variable indicates the number of iterations needed for the Regula Falsi method to converge.
Generator Heat Recovery Exit Gas Temperature [C][LINK]
This is the temperature of the exiting gas for heat recovery in C.
Generator Heat Recovery Exit Gas H2O Vapor Fraction [][LINK]
This is the water vapor fraction in the exit gas.
Generator Heat Recovery Water Condensate Molar Flow Rate [kmol/s][LINK]
This is the flow of condensed water in kmol/s.
Generator:FuelCell:PowerModule[LINK]
This object is used to describe the core power module subsystem of the FC. This includes the fuel cell stack, fuel reformer, and whatever ancillary devices are included inside. If the model has multiple FC generators that are of the exact same type, then only one of these objects is needed and all the Generator:FuelCell can reference it. The model uses a number of curves to describe operating performance. Input data for specific models of FC are not yet available but will be produced by IEA Annex 42 and should be available in the future.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell power module subsystem.
Field: Efficiency Curve Mode[LINK]
This field is used to choose between different modes of inputting the electrical efficiency curve. There are two options available for this Field: “Annex42” and “Normalized”. The “Annex42” option indicates that the efficiency curves are not normalized and are used for the single size and type of FC product. The “Normalized” option indicates that the efficiency curves are normalized (as is standard practice in EnergyPlus) relative to a single rating point. In the Annex42 mode, the curves directly represent efficiency as a function of fuel use, but in the Normalized mode, the curves represent an efficiency modification that is applied to the efficiency at the rating point.
Field: Efficiency Curve Name[LINK]
This field contains the name of a Curve:Quadratic input object described elsewhere in the input file. The curve is a function of the net DC electric power, \({P_{el}}\) (W), produced by the power module and describes either the electrical efficiency or the how the efficiency is modified depending on the mode selected in the previous field. This quadratic curve is just one part of the entire parametric relation used to describe electrical efficiency \({\varepsilon _{el}}\). For the Annex42 mode the full relation for efficiency is,
\[{\varepsilon _{el}} = \left[ {{\varepsilon _0} + {\varepsilon _1} \cdot {P_{el}} + {\varepsilon _2} \cdot P_{el}^2} \right] \cdot \left[ {1 - {N_{stops}} \cdot D} \right] \cdot \left[ {1 - (MAX(\int\limits_{} {dt - {t_{threshold}},0.0))} \cdot L} \right]\]
where the Curve:Quadratic input object named in this field serves to define the quadratic portion in the first set of brackets. For the Normalized mode the full relation for efficiency is,
where \({\varepsilon _{nom}}\) is the nominal electrical efficiency at the rating point \({P_{nom}}\) which are described in the next two fields. The Normalized mode may be more useful for a simulation study that needs to vary the capacity of the FC.
Field: Nominal Efficiency[LINK]
This field is used for the “Normalized” efficiency curve mode and provides the nominal efficiency \({\varepsilon _{nom}}\) (dimensionless) at the rating point. This field can be left blank if using the “Annex42” mode.
Field: Nominal Electrical Power[LINK]
This field is used for the “Normalized” efficiency curve mode and provides the nominal net DC electrical power produced \({P_{nom}}\) (W) at the rating point. This field can be left blank if using the “Annex42” mode.
Field: Number of Stops at Start of Simulation[LINK]
This field is used to describe the number of times the FC has been cycled on and off prior to the start of the simulation. FC products might degrade as a result of starting and stopping the fuel cell stack, so the model includes terms to model the degradation effects of cycling FC units on and off. This is the initial value of the \({N_{stops}}\) term in the efficiency relation above.
Field: Cycling Performance Degradation Coefficient[LINK]
This field is used to describe the fixed value representing the fractional performance degradation associated with each start and stop cycle. This is the value of \(D\) in the efficiency relations above. If there is no degradation from cycling, then D should be 0.0.
Field: Number of Run Hours at Beginning of Simulation[LINK]
This field is used to describe the amount of time the FC has been operating prior to the start of the simulation. FC products might degrade over time so the model includes terms to model the degradation effects of FC run time. This is the initial value of the integrated run time term \(\int\limits_0 {dt}\).
Field: Accumulated Run Time Degradation Coefficient[LINK]
This field is used to describe the fixed value representing the fractional performance degradation associated with the total amount of run time. This is the value of \(L\) in the efficiency relations above. If there is no degradation from run time, the L should be 0.0.
Field: Run Time Degradation Initiation Time Threshold[LINK]
This field is used to describe the time period for which there is no degradation associated with the amount of run time. This provides the ability to model a system that initially operates without degradation for some period time before it starts to degrade. This is the value of \({t_{threshold}}\) in the efficiency relations above.
Field: Power Up Transient Limit[LINK]
This field is used to describe the maximum allowable rate at which the fuel cell can increase the level of power it produces (W/s). This is a time derivative of the net DC electrical power used to limit how fast the FC can ramp up.
Field: Power Down Transient Limit[LINK]
This field is used to describe the maximum allowable rate at which the fuel cell can decrease the level of power it produces (W/s). This is a time derivative of the net DC electrical power used to limit how fast the FC can ramp down.
Field: Start Up Time[LINK]
This field is used to describe the length of time (seconds) of the start up period when the FC is turned on.
Field: Start Up Fuel[LINK]
This field is used to describe the amount of fuel (kmol) used during the entire start up period. The fuel is the same type as what is described in the Generator:FuelSupply object elsewhere in the input file.
Field: Start Up Electricity Consumption[LINK]
This field is used to describe the amount of electricity (Joules) used by ancillary equipment during the entire start up period.
Field: Start Up Electricity Produced[LINK]
This field is used to describe the amount of electricity (Joules) produced by the power module during the entire start up period.
Field: Shut Down Time[LINK]
This field is used to describe the length of time (seconds) of the shut down period.
Field: Shut Down Fuel[LINK]
This field is used to describe the amount of fuel (kmol) used during the entire shut down period. The fuel is the same type as what is described in the Generator:FuelSupply object elsewhere in the input file.
Field: Shut Down Electricity Consumption[LINK]
This field is used to describe the amount of electricity (J) used by ancillary equipment during the entire shut down period.
Field: Ancilliary Electricity Constant Term[LINK]
This field is used to describe the constant term, \(an{c_0}\), in a relation that describes the AC electrical power used by ancillary equipment located inside the power module, \({P_{el,ancillaries - AC}}\). The model uses this relation,
\[{P_{el,ancillaries - AC}} = an{c_0} + an{c_1} \cdot {\dot N_{fuel}}\]
where \({\dot N_{fuel}}\) is the rate of fuel use in the power module (kmol/s).
Field: Ancilliary Electricity Linear Term[LINK]
This field is used to describe the linear term, \(an{c_1}\), in the relation shown in the previous field.
Field: Skin Loss Calculation Mode[LINK]
This field is used to select the mode for how skin losses are modeled. Skin losses are heat energy “lost” from the power module and transferred to the surrounding thermal zone named in the following field. There are three alpha options to choose from: “ConstantRate”, “UAForProcessGasTemperature”, or “QuadraticFunctionOfFuelRate.” Enter ConstantRate in this field to model skin losses using a constant rate, e.g. 100 watts. Enter UAForProcessGasTemperature to model skin losses using a “UA-Delta-T” calculation method with the temperature difference determined by the power module’s product gas temperature and the surrounding zone. Enter QuadraticFunctionOfFuelRate to model skin losses as a function of the rate of fuel use.
Field: Zone Name[LINK]
This field is used to describe the thermal zone that will receive skin and other heat losses from the FC. This should be the name of a Zone input object declared elsewhere in the input file.
Field: Skin Loss Radiative Fraction[LINK]
This field is used to describe the portion of skin losses that are in the form of thermal radiation. This controls the radiative/convective split for the energy transferred to the zone by the FC.
Field: Constant Skin Loss Rate[LINK]
This field is used to describe the constant rate of skin losses (W). This field is used with the ConstantRate mode. It can be left blank for other skin loss modes.
Field: Skin Loss U-Factor Times Area Term[LINK]
This field is used to describe the “UA” term (W/K). This field is used with the UAForProcessGasTemperature mode. It can be left blank for other skin loss modes. “UA” is the product of the overall heat transfer coefficient “U” and the area “A.”
Field: Skin Loss Quadratic Curve Name[LINK]
This field is used to refer to the name of a quadratic curve object defined elsewhere in the input file. The quadratic curve should define skin heat loss rate as a function of the fuel use rate (kmol/s) so that,
\[{q_{skin - loss}} = {s_0} + {s_1} \cdot {\dot N_{fuel}} + {s_2} \cdot \dot N_{fuel}^2\]
Field: Dilution Air Flow Rate[LINK]
This field is used to describe the rate of dilution air (kmol/sec) drawn into, or through, the power module. This air stream may not be present in all FC products. It is used for limiting skin and stack heat losses and for strategies that mitigate potential safety issue were fuel gases to escape the stack.
Field: Stack Heat loss to Dilution Air[LINK]
This field is used to describe the rate at which the fuel cell stack adds energy to the dilution air stream. It is entered as a constant heat rate (W).
Field: Dilution Inlet Air Node Name[LINK]
This field is used to describe the air node where the dilution air is drawn from. This would typically be the name of the air node associated with the thermal zone where the FC is located.
Field: Dilution Outlet Air Node Name[LINK]
This field is used to describe the air node where the dilution air is exhausted to. This could be the inlets to a heat recovery ventilator or an exhaust node.
Field: Minimum Operating Point[LINK]
This field is used to describe the minimum operating point for the net DC electric power, \({P_{el}}\) (W).
Field: Maximum Operating Point[LINK]
This field is used to describe the maximum operating point for the net DC electric power, \({P_{el}}\) (W).
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:StackCooler[LINK]
This object is optional and is used to define details needed to model the stack cooler on PEMFC.
Field: Name[LINK]
This field contains a unique name for the PEM fuel cell stack cooler
Field: Heat Recovery Water Inlet Node Name[LINK]
This field contains the node name for the water inlet to the stack cooler.
Field: Heat Recovery Water Outlet Node Nane[LINK]
This field contains the node name for the water outlet from the stack cooler.
Field: Nominal Stack Temperature[LINK]
This field contains the nominal stack operating temperature for the PEMFC, \(T_{stack}^o\). This field and the next five provide values for use in the empirical equation for the rate of heat extracted from the fuel cell power module by the stack cooler using the following relation
\[{q_{s - cool}} = \left[ {{r_0} + {r_1}\left( {{T_{stack}} - T_{stack}^o} \right)} \right] \cdot \left[ {1 + {r_2}{P_{el}} + {r_3}P_{el}^2} \right]\]
Field: Actual Stack Temperature][LINK]
This field contains the actual stack operating temperature for the PEMFC, \({T_{stack}}\).
Field: Coefficient r0[LINK]
This field contains the coefficient r0 in the equation above.
Field: Coefficient r1[LINK]
This field contains the coefficient r1 in the equation above.
Field: Coefficient r2[LINK]
This field contains the coefficient r2 in the equation above.
Field: Coefficient r3[LINK]
This field contains the coefficient r3 in the equation above.
Field: Stack Coolant Flow Rate[LINK]
The stack cooler is assumed to have a closed water circulation loop that is used to extract heat from the stack and move it to a cogeneration heat exchanger and/or an air cooler. This field is used to enter the flow rate of coolant in this loop.
Field: Stack Cooler U-Factor Times Area Value[LINK]
This is the heat transfer coefficient between the stack and the coolant.
Field: Fs-cogen Adjustment Factor[LINK]
This field provides the value for an adjustment factor, \({F_{s - cogen}}\), used in the following relation for the cogeneration heat transfer coefficient, \({\left( {UA} \right)_{s - cogen}}\):
\[{\left( {UA} \right)_{s - cogen}} = {\left[ {\frac{1}{{{{\left( {hA} \right)}_{s - cogen}}}} + {F_{s - cogen}}} \right]^{ - 1}}\]
Field: Stack Cogeneration Exchanger Area[LINK]
This field provides the value for the cogeneration heat exchanger area, \({A_{s - cogen}}\)
Field: Stack Cogeneration Exchanger Nominal Flow Rate[LINK]
This field provides the value for \(\dot N_{s - cogen}^0\) in the following relation for the cogeneration heat exchanger convection coefficient, \({h_{s - cogen}}\):
\[{h_{s - cogen}} = h_{s - cogen}^0 \cdot {\left( {\frac{{{{\dot N}_{s - cogen}}}}{{\dot N_{s - cogen}^0}}} \right)^{{n_s}}}\]
Field: Stack Cogeneration Exchanger Nominal Heat Transfer Coefficient[LINK]
This field provides the value for \(h_{s - cogen}^0\) in the relation above for the cogeneration heat exchanger convection coefficient, \({h_{s - cogen}}\).
Field: Stack Cogeneration Exchanger Nominal Heat Transfer Coefficient Exponent[LINK]
This field provides the value for \({n_s}\) is the relation above for the cogeneration heat exchanger convection coefficient, \({h_{s - cogen}}\).
Field: Stack Cooler Pump Power[LINK]
This field is the power used by the stack cooler’s circulating pump in Watts. It is a constant power draw whenever the stack cooler is active.
Field: Stack Cooler Pump Heat loss[LINK]
This field is the fraction of the pump power consumption that is lost to the surround zone.
Field: Stack Air Cooler Fan Coefficient f0[LINK]
This field and the next two are used to define coefficients for the following relation for the power used by the air-cooler’s fan to dump excess heat into the surrounding zone:
\[{P_{s - air - el}} = {f_0} + {f_1} \cdot {q_{s - air}} + {f_2} \cdot q_{s - air}^2\]
Field: Stack Air Cooler Fan Coefficient f1[LINK]
This field provides a value for the coefficient f1 in the relation above.
Field: Stack Air Cooler Fan Coefficient f2[LINK]
This field provides a value for the coefficient f2 in the relation above.
Generator:FuelCell:AirSupply[LINK]
This object is used to define details of the air supply subsystem.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell air supply subsystem.
Field: Air Inlet Node Name[LINK]
This field is used to define the air node where the inlet air stream is drawn from. If the FC uses outdoor air then the node named here should be designated an outdoor air node. If the FC draws air from its surroundings, then this would be the name of the air node associated with the thermal zone containing the FC.
Field: Blower Power Curve Name[LINK]
This field contains the name of a Curve:Cubic input object described elsewhere in the input file. The curve provides the power used by the air blower (W) as a cubic function of the rate of air supply (kmol/s).
\[{P_{blower - el}} = {b_0} + {b_1} \cdot {\dot N_{air}} + {b_2} \cdot \dot N_{air}^2 + {b_3} \cdot \dot N_{air}^3\]
Field: Blower Heat Loss Factor[LINK]
This field describes the portion of blower electrical power that is “lost” to the surroundings. The rest of the energy is added to the air stream. A heat loss factor of 1.0 indicates that all the heat is lost to the surroundings and no energy is added to the air inlet stream.
Field: Air Supply Rate Calculation Mode[LINK]
This field describes how the model will calculate the air supply rate. There are three options to choose from: “AirRatiobyStoics”, “QuadraticFunctionofElectricPower”, and “QuadraticFunctionofFuelRate.” The choice will determine how the model calculates the rate of air and will depend on the formulations used to develop model input data. The choices are described in the next four fields.
Field: Stoichiometric Ratio[LINK]
This field describes the excess air ratio beyond stoichiometric air supply. This field is only used if the air supply rate calculation mode is AirRatiobyStoics. The total air supply ratio will be the value entered here plus 1.0. Thus if 1.0 is entered in this field, the total air flow will be 2.0 times what is needed to exactly match stoichiometry with the fuel supply.
Field: Air Rate Function of Electric Power Curve Name[LINK]
This field contains the name of a QuadraticCurve input object described elsewhere in the input file. This field is only used if the air supply rate calculation mode is QuadraticFunctionofElectricPower. The quadratic curve named here describes the first part of the relation below used to calculate the rate of inlet air, \({\dot N_{air}}\) (kmol/s). It is a quadratic function of the net DC electrical power, \({P_{el}}\) (W).
\[{\dot N_{air}} = \left[ {{a_0} + {a_1} \cdot {P_{el}} + {a_2} \cdot P_{el}^2} \right].\left[ {1 + {a_3} \cdot {T_{air}}} \right]\]
Field: Air Rate Air Temperature Coefficient[LINK]
This field is used to describe the air temperature coefficient, \({a_3}\), used to adjust inlet air flow rate in the relations for inlet air rate.
Field: Air Rate Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Quadratic input object described elsewhere in the input file. This field is only used if the air supply rate calculation mode is QuadraticFunctionofFuelRate. The quadratic curve named here describes the first part of the relation used to calculate the rate of inlet air, \({\dot N_{air}}\) (kmol/s). It is a quadratic function of the fuel flow rate, \({\dot N_{fuel}}\).
\[{\dot N_{air}} = \left[ {{a_0} + {a_1} \cdot {{\dot N}_{fuel}} + {a_2} \cdot \dot N_{fuel}^2} \right].\left[ {1 + {a_3} \cdot {T_{air}}} \right]\]
Field: Air Intake Heat Recovery Mode[LINK]
This field is used to control how heat losses from three other subsystems within the FC may or may not be recovered by the air inlet. There are six possible choices for what to use in this Field: “NoRecovery” “RecoverBurnerInverterStorage” “RecoverAuxiliaryBurner” “RecoverInverterandStorage” “RecoverInverter” and “RecoverElectricalStorage”. If heat is recovered then that means that energy “losses” from those subsystems are added to the inlet air and fed back into the FC power module. The following table clarifies the meaning of the six possible choices.
Field: Air Supply Constituent Mode[LINK]
This field is used to choose between two different modes for describing the make up of the inlet air stream. There are two possible choices: “AmbientAir” or “UserDefinedConstituents.” Choosing the AmbientAir mode will automatically set the composition of air to be usual at: 77.28% nitrogen, 20.73% oxygen, 1.04% water, 0.92% argon, and 0.03% carbon dioxide. Choosing UserDefinedConstituents allows the user to customize the make up the inlet air in the remaining fields.
Field: Number of UserDefined Constituents[LINK]
This field is used to describe the number of constituents in the inlet air. This field is only used if the air supply constituent mode is set to UserDefinedConstituents. The maximum number is 5.
The remaining fields in this object are repeating pairs of fields with one pair for each constituent and the same number as described in the previous field. The pairs consist of the name of the constituent followed by the molar fraction of that constituent.
Field: Constituent 1-5 Name[LINK]
These fields describe the air stream constituents by name. The name field for each pair must be filled with one of these choices: “CarbonDioxide”, “Nitrogen,” “Oxygen,” “Water,” or “Argon.”
Field: Molar Fraction 1-5[LINK]
These fields describe the molar fraction of the air stream constituents. It is very important that the sum of the molar fractions add up to 1.0.
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:WaterSupply[LINK]
This object is used to provide details of the water supply subsystem. This water is used for steam reforming of the fuel and is not the same as the water used for thermal heat recovery.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell water supply subsystem.
Field: Reformer Water Flow Rate Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Quadratic input object described elsewhere in the input file. The curve provides the rate of water flow (kmol/sec) as a function of fuel flow rate (kmol/sec).
\[{\dot N_{liq - water}} = {w_0} + {w_1} \cdot {\dot N_{fuel}} + {w_2} \cdot \dot N_{fuel}^2\]
If the unit does not use water for reforming then use a “null” quadratic where all the coefficients are 0.0.
Field: Reformer Water Pump Power Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Cubic input object described elsewhere in the input file. The curve provides the power used by the water pump (W) as a cubic function of the rate of water supply (kmol/s).
\[{P_{pump - el}} = {p_0} + {p_1} \cdot {\dot N_{water}} + {p_2} \cdot \dot N_{water}^2 + {p_3} \cdot \dot N_{water}^3\]
If the unit does not use water for reforming then use a “null” cubic where all the coefficients are 0.0.
Field: Pump Heat Loss Factor[LINK]
This field describes the portion of pump electrical power that is “lost” to the surroundings. The rest of the energy is added to the water stream. A heat loss factor of 1.0 indicates that all the heat is lost to the surroundings and no energy is added to the water inlet stream.
Field: Water Temperature Modeling Mode[LINK]
This field describes how the model will determine the inlet temperature of the water stream. There are four options to choose from: “TemperatureFromAirNode,” “TemperatureFromWaterNode,” “TemperatureFromSchedule,” and “MainsWaterTemperature.” For the first two options, the temperature of the water inlet is determined by the temperature at the node named in the next field. For the third option, the temperature is determined by the schedule in the last field. Using the MainsWaterTemperature option requires also defining a separate “Site:WaterMainsTemperature” input object elsewhere in the input file.
Field: Water Temperature Reference Node Name[LINK]
This field is used to define the node where the temperature of the inlet water stream is obtained. This can be either an air node or a water node.
Field: Water Temperature Schedule Name[LINK]
This field is used to define the name of a schedule, defined elsewhere in the input file, that will be used to determine the temperature of the water inlet stream when using the TemperatureFromSchedule mode.
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:AuxiliaryHeater[LINK]
This object is intended for modeling an auxiliary heater, however this portion of the model is not yet available in EnergyPlus. An auxiliary heater may be present in fuel cell products so that the unit can meet much higher thermal loads than would be possible using only cogeneration. This portion of the model will be added in the future once suitable cogeneration control capabilities are also available. The input fields are described for future reference but may change. The program still requires one of these objects be included even though the data are not yet used (so that internal data structures can be allocated).
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell auxiliary heater subsystem.
Field: Excess Air Ratio[LINK]
This field describes the excess air ratio beyond stoichiometric air supply for the heater. The total air supply ratio will be the value entered here plus 1.0. Thus if 1.0 is entered in this field, the total air flow will be 2.0 times what is needed to exactly match stoichiometry with the fuel supply.
Field: Ancillary Power Constant Term[LINK]
This field describes the constant term, \({x_0}\), used to model the auxiliary burner’s ancillary devices such as fans and ignition controls. The electrical power for ancillaries is calculated using,
\[{P_{el,aux - ancillaries}} = {x_0} + {x_1} \cdot {\dot N_{aux - fuel}}\]
Field: Ancillary Power Linear Term[LINK]
This field describes the linear term, \({x_1}\), used to model the auxiliary burner’s ancillary devices.
Field: Skin Loss U-Factor Times Area Value[LINK]
This field describes the “UA” term (W/K) for calculating skin losses in the auxiliary burner. “UA” is the product of the overall heat transfer coefficient “U” and the area “A.” The skin heat losses are calculated using,
\[{q_{aux - skin - losses}} = {(UA)_{aux}} \cdot ({T_{aux - mix}} - {T_{room}})\]
where, \({T_{aux - mix}}\) is temperature of product gases leaving the auxiliary burner and includes the mixing of the product gases from the fuel cell power module. Thus, the input for UA should reflect this choice of reference temperature rather than an exterior surface temperature of the auxiliary burner.
Field: Skin Loss Destination[LINK]
This field describes the user’s choice for what happens to the skin losses. There are two options: “SurroundingZone” and “AirInletForFuelCell”. Entering SurroundingZone will direct the model to put the “lost” energy into the surrounding thermal Zone named in the next field. Entering AirInletForFuelCell will direct the model to put the “lost” energy into the air inlet stream for the fuel cell to preheat that air.
Field: Zone Name to Receive Skin Losses[LINK]
This field is used to determine the zone that will receive the skin losses. Enter the name of a Zone declared elsewhere in the input file. This field is only used if the “SurroundingZone” mode is used in the previous field.
Field: Heating Capacity Units[LINK]
This field describes the user’s choice for how the capacity of the auxiliary heater will be defined. There are two options: “Watts” or “kmol/s.” Entering Watts will direct the program to use the next two fields to determine the maximum and minimum heating capacity. Entering kmol/s will direct the program to use the last two fields to determine the maximum and minimum heating capacities.
Field: Maximum Heating Capacity in Watts[LINK]
This field is used to describe the maximum heating capacity of the auxiliary burner (W).
Field: Minimum Heating Capacity in Watts[LINK]
This field is used to describe the minimum heating capacity of the auxiliary burner (W).
Field: Maximum Heating Capacity in Kmol per Second[LINK]
This field is used to describe the maximum fuel use rate for the auxiliary burner (kmol/s).
Field: Minimum Heating Capacity in Kmol per Second[LINK]
This field is used to describe the minimum fuel use rate for the auxiliary burner (kmol/s).
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:ExhaustGasToWaterHeatExchanger
This object is used to describe the exhaust gas heat exchanger subsystem of the FC used to recovery thermal energy.
Field: Name[LINK]
This field contains a unique name for the fuel cell power module subsystem.
Field: Heat Recovery Water Inlet Node Name[LINK]
This field contains the name of the node that connects the heat exchanger’s inlet to the plant loop. This water is used for heat recovery.
Field: Heat Recovery Water Outlet Node Name[LINK]
This field contains the name of the node that connects the heat exchanger’s outlet to the plant loop.
Field: Heat Recovery Water Maximum Flow Rate[LINK]
This field describes the design maximum flow rate of the heat recovery water (m3/s). The value should match the design flow rate of the plant loop connected to the FC.
Field: Exhaust Outlet Air Node Name[LINK]
This field is used to determine which node will receive the exhaust air stream leaving the FC. This node will usually be outside and not be referenced elsewhere. However, if the exhaust stream is used in a heat recovery ventilator (as described in section 11 of the Annex 42 specification) then the node would be reference in the heat recovery ventilator object.
Field: Heat Exchanger Calculation Method[LINK]
This field is used to direct how EnergyPlus will calculate heat exchanger performance. The Annex 42 model provides for four different methods of modeling the heat exchanger. The choices available for this field are: “FixedEffectiveness” (method 1 in Annex 42 specification), “EmpiricalUAeff” (method 2), “FundementalUAeff” (method 3), or “Condensing” (method 4). The remaining fields provide input data for the different methods. The heat exchanger correlations are described below.
Field: Method 1 Heat Exchanger Effectiveness[LINK]
This field describes constant heat exchanger effectiveness, \({\varepsilon _{HX}}\). This field is only used with the “FixedEffectiveness” mode, which corresponds to “method 1” in the Annex 42 specification. For this mode, the heat exchange between the exhaust gases and the heat recovery water are calculated using,
\[{q_{HX}} = {\varepsilon _{HX}} \cdot {\left( {\dot N{{\hat c}_p}} \right)_{\min }} \cdot \left( {{T_{aux - mix}} - {T_{water,in}}} \right)\]
where, \({\left( {\dot N{{\hat c}_p}} \right)_{\min }}\) is the minimum value of \({\left( {\dot N{{\hat c}_p}} \right)_{aux - mix}}\) and \({\left( {\dot N{{\hat c}_p}} \right)_{water}}\).
Field: Method 2 Parameter hxs0[LINK]
This field describes the value of \(h{x_{s,0}}\) in the relation below for effective UA. This field is used with the “EmpiricalUAeff” mode, which corresponds to “method 2” in the Annex 42 specification and with the “Condensing” mode, which corresponds to “method 4”. This method uses the log mean temperature difference (LMTD) approach to calculate the heat exchange:
\[{q_{HX}} = {\left( {UA} \right)_{eff}} \cdot \frac{{\left( {{T_{aux - mix}} - {T_{water,out}}} \right) - \left( {{T_{HX - exh}} - {T_{water,in}}} \right)}}{{\ln \left( {\frac{{{T_{aux - mix}} - {T_{water,out}}}}{{{T_{HX - exh}} - {T_{water,in}}}}} \right)}}\]
The user input in this field, and the next four fields, describe coefficients in an empirical relation for \({\left( {UA} \right)_{eff}}\):
\[{\left( {UA} \right)_{eff}} = h{x_{s,0}} + h{x_{s,1}} \cdot {\dot N_{water}} + h{x_{s,2}} \cdot \dot N_{water}^2 + h{x_{s,3}} \cdot {\dot N_{aux - mix}} + h{x_{s,4}} \cdot \dot N_{aux - mix}^2\]
Field: Method 2 Parameter hxs1[LINK]
This field describes the value of \(h{x_{s,1}}\) in the relation above for effective UA. This field is used with the “EmpiricalUAeff” mode, which corresponds to “method 2” in the Annex 42 specification and with the “Condensing” mode, which corresponds to “method 4”.
Field: Method 2 Parameter hxs2[LINK]
This field describes the value of \(h{x_{s,2}}\) in the relation above for effective UA. This field is used with the “EmpiricalUAeff” mode, which corresponds to “method 2” in the Annex 42 specification and with the “Condensing” mode, which corresponds to “method 4”.
Field: Method 2 Parameter hxs3[LINK]
This field describes the value of \(h{x_{s,3}}\) in the relation above for effective UA. This field is used with the “EmpiricalUAeff” mode, which corresponds to “method 2” in the Annex 42 specification and with the “Condensing” mode, which corresponds to “method 4”.
Field: Method 2 Parameter hxs4[LINK]
This field describes the value of \(h{x_{s,4}}\) in the relation above for effective UA. This field is used with the “EmpiricalUAeff” mode, which corresponds to “method 2” in the Annex 42 specification and with the “Condensing” mode, which corresponds to “method 4”.
Field: Method 3 h0Gas Coefficient[LINK]
This field describes the value of \(h_{gas}^0\) in the relation below. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification. For this mode, the heat exchange is calculated using the LMTD method, but the effective UA is determined using:
\[{\left( {UA} \right)_{eff}} = {\left[ {\frac{1}{{{{\left( {hA} \right)}_{gas}}}} + \frac{1}{{{{(hA)}_{water}}}} + {F_{HX}}} \right]^{ - 1}}\]
where,
\({F_{HX}}\) is an adjustment factor,
\({h_{gas}} = h_{gas}^0 \cdot {\left( {\frac{{{{\dot N}_{gas}}}}{{\dot N_{gas}^0}}} \right)^n}\),
\({h_{water}} = h_{water}^0 \cdot {\left( {\frac{{{{\dot N}_{water}}}}{{\dot N_{water}^0}}} \right)^m}\)
Field: Method 3 NdotGasRef Coefficient[LINK]
This field describes the value of \(\dot N_{gas}^0\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 n Coefficient[LINK]
This field describes the value of \(n\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 Gas Area[LINK]
This field describes the value of \({A_{gas}}\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 h0 Water Coefficient[LINK]
This field describes the value of \(h_{water}^0\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 N dot Water ref Coefficient[LINK]
This field describes the value of \(\dot N_{water}^0\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 m Coefficient[LINK]
This field describes the value of \(m\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 Area Water Coefficient[LINK]
This field describes the value of \({A_{water}}\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 3 F Adjustment Factor[LINK]
This field describes the value of \({F_{HX}}\) in the relation above. This field is only used with the “FundementalUAeff” mode, which corresponds to “method 3” in the Annex 42 specification.
Field: Method 4 hxl1 Coefficient[LINK]
This field describes the value of \(h{x_{l,1}}\) in the relation below for the rate of condensation of water from the gas stream, \({\dot N_{{H_2}O - cond}}\). This field is only used with the “Condensing” mode, which corresponds to “method 4” in the Annex 42 specification. This method uses a modified version of the LMTD approach to calculate heat exchange:
\[{q_{HX}} = {\left( {UA} \right)_{eff}} \cdot \frac{{\left( {{T_{aux - mix}} - {T_{water,out}}} \right) - \left( {{T_{HX - exh}} - {T_{water,in}}} \right)}}{{\ln \left( {\frac{{{T_{aux - mix}} - {T_{water,out}}}}{{{T_{HX - exh}} - {T_{water,in}}}}} \right)}} + {\dot N_{{H_2}O - cond}} \cdot {\hat h_{fg}}\]
where,
\[{\dot N_{{H_2}O - cond}} = \left( {{T_{cond - threshold}} - {T_{water,in}}} \right) \cdot \left[ {h{x_{l,1}} \cdot \left( {\frac{{{{\dot N}_{{H_2}O}}}}{{{{\dot N}_{aux - mix}}}}} \right) + h{x_{l,2}} \cdot {{\left( {\frac{{{{\dot N}_{{H_2}O}}}}{{{{\dot N}_{aux - mix}}}}} \right)}^2}} \right]\]
Field: Method 4 hxl2 Coefficient[LINK]
This field describes the value of \(h{x_{l,2}}\) in the relation above for the rate of condensation of water from the gas stream, \({\dot N_{{H_2}O - cond}}\). This field is only used with the “Condensing” mode, which corresponds to “method 4” in the Annex 42 specification.
Field: Method 4 Condensation Threshold[LINK]
This field describes the value of \({T_{cond - threshold}}\) in the relation above for the rate of condensation of water from the gas stream, \({\dot N_{{H_2}O - cond}}\). This field is only used with the “Condensing” mode, which corresponds to “method 4” in the Annex 42 specification.
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:ElectricalStorage[LINK]
This object is used to describe the electrical storage subsystem for the FC. The electrical storage model is a very simple “constrained bucket” model. Future developments made add additional models for battery systems. Note that this electrical storage is embedded within the FC device.
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell electrical storage subsystem.
Field: Choice of Model[LINK]
This field is used to direct how EnergyPlus will model electrical storage. The only choice currently available is “SimpleEfficiencyWithConstraints,” which should be entered in this field. Future developments may expand the number of models available for electrical storage.
Field: Nominal Charging Energetic Efficiency[LINK]
This field describes the value of \({\varepsilon _{charge}}\) in the relation for the State of Charge, \(Q_{battery}^{t + \Delta t}\):
\[Q_{battery}^{t + \Delta t} = Q_{battery}^t + {P_{battery - charge}} \cdot {\varepsilon _{charge}} \cdot \Delta t\]
This is the energetic efficiency of charging the storage device. A value of 1.0 means that the storage device does not lose any energy when charging. Note that the model can recover the “lost” energy into the air supply intake.
Field: Nominal Discharging Energetic Efficiency[LINK]
This field describes the value of \({\varepsilon _{discharge}}\) in the relation for the State of Charge, \(Q_{battery}^{t + \Delta t}\):
\[Q_{battery}^{t + \Delta t} = Q_{battery}^t + \frac{{{P_{battery - discharge}} \cdot \Delta t}}{{{\varepsilon _{discharge}}}}\]
This is the energetic efficiency of discharging the storage device. A value of 1.0 means that the storage device does not lose any energy when discharging. Note that the model can recover the “lost” energy into the air supply intake.
Field: Simple Maximum Capacity[LINK]
This field describes the maximum amount of electrical energy that can be stored in the device (J).
Field: Simple Maximum Power Draw[LINK]
This field describes the maximum rate at which electrical power can be discharged from the storage device (W).
Field: Simple Maximum Power Store[LINK]
This field describes the maximum rate at which electrical power can charge the storage device (W).
Field: Initial Charge State[LINK]
This field describes the value for the initial state of charge (J). This allows the storage device to contain some amount of stored electricity at the beginning of the simulation period.
An example input data file (IDF) entry for this object is provided below:
Generator:FuelCell:Inverter[LINK]
This object is used to describe the power condition unit subsystem of the FC. This object models an inverter system contained within a fuel cell system that converts from direct current (DC) to alternating current (AC).
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell inverter subsystem.
Field: Inverter Efficiency Calculation Mode[LINK]
This field is used to direct how EnergyPlus will calculate the inverter efficiency. There are two possible choices: “Constant” or “Quadratic”.
Field: Inverter Efficiency[LINK]
This field describes the value for inverter efficiency when using the Constant mode.
Field: Efficiency Function of DC Power Curve Name[LINK]
This field names a Curve:Quadratic object defined elsewhere in the input file. The curve determines inverter efficiency as a function of the DC power entering the inverter as follows:
\[{\eta _{PCU}} = {u_0} + {u_1} \cdot {P_{PCU - in}} + {u_2} \cdot P_{PCU - in}^2\]
An example input data file (IDF) entry for this object is provided below:
Generator:FuelSupply[LINK]
This object is used to define details of the fuel supply for certain generators. This object allows the user to describe a wide array of possible fuel mixtures. The program contains data and internal methods to calculate the properties of the various mixtures of gaseous fuels. The program will calculate the Lower Heating Value (LHV), Higher Heating Value (HHV), and molecular weight for the fuel mixture. The fuel properties are then use by both fuel cell and Micro CHP models. Results of the gas phase thermochemistry modeling are also reported in the EIO file.
In addition to gaseous mixtures, the Micro CHP model is able to use generic liquid fuels and this object is used to describe the properties.
Note that the fuel consumption metering is currently handled by the Natural Gas meter. So no matter what fuel mixture is defined in this object, the aggregated reports from EnergyPlus meters for (natural) Gas will include the fuel used for the generator (with the Joule content based on HHV).
Inputs[LINK]
Field: Name[LINK]
This field contains a unique name for the fuel cell fuel supply subsystem.
Field: Fuel Temperature Modeling Mode[LINK]
This field describes how the model will determine the temperature of the fuel. There are two options for this field to choose from: “TemperatureFromAirNode” and “Scheduled.” If this field contains TemperatureFromAirNode then the fuel is modeled as having the same temperature as the air node that is named in the next field. If this field contains Scheduled then the fuel is modeled as having the temperature described in a schedule defined elsewhere in the input file.
Field: Fuel Temperature Reference Node Name[LINK]
This field contains the name of the air node used to obtain the inlet temperature of the fuel. This field is only used if the Fuel Temperature Modeling Mode is set to TemperatureFromAirNode.
Field: Fuel Temperature Schedule Name[LINK]
This field contains the name of a temperature schedule defined elsewhere in the input file. This field is only used if the Fuel Temperature Modeling Mode is set to Scheduled. The temperature of the fuel inlet will be obtained from the schedule.
Field: Compressor Power Function of Fuel Rate Curve Name[LINK]
This field contains the name of a Curve:Cubic input object described elsewhere in the input file. The curve provides the electrical power used by the fuel compressor (W) as a cubic function of the rate of fuel supply (kmol/s).
\[{P_{comp - el}} = {c_0} + {c_1} \cdot {\dot N_{fuel}} + {c_2} \cdot \dot N_{fuel}^2 + {c_3} \cdot \dot N_{fuel}^3\]
Field: Compressor Heat Loss Factor[LINK]
This field describes the portion of the compressor electrical power that is “lost” to the surroundings. The rest of the energy is added to the fuel stream. A heat loss factor of 1.0 indicates that all the heat is lost to the surroundings and no energy is added to the fuel inlet stream.
Field: Fuel Type[LINK]
Choose between “GaseousConstituents” or “LiquidGeneric”.
Field: Liquid Generic Fuel Lower Heating Value[LINK]
For fuel type “LiquidGeneric,” this field is used to enter the lower heating value of the fuel in units of kJ/kg.
Field: Liquid Generic Fuel Higher Heating Value[LINK]
For fuel type “LiquidGeneric,” this field is used to enter the higher heating value of the fuel in units of kJ/kg.
Field: Liquid Generic Fuel Molecular Weight[LINK]
For fuel type “LiquidGeneric,” this field is used to enter the molecular weight of the fuel in units of g/mol.
Field: Liquid Generic Fuel CO2 Emission Factor[LINK]
This field is not used. This part of the Annex 42 model was not implemented in EnergyPlus; see the FuelFactors object.
Field: Number of Constituents in Gaseous Constituent Fuel Supply[LINK]
This field is used to describe the number of constituents in the inlet fuel supply. The maximum number of different types of constituents is currently set to 12.
The remaining fields in this object are repeating pairs of fields with one pair for each constituent and the same number as described in the previous field. The field set pairs consist of the name of the constituent followed by the molar fraction of that constituent.
Field: Constituent 1-12 Name[LINK]
These fields describe the fuel stream constituents by name. The name field for each pair must be filled with one of these 14 choices: “CarbonDioxide”, “Nitrogen”, “Oxygen”, “Water”, “Argon”, “Hydrogen”, “Methane”, “Ethane”, “Propane”, “Butane”, “Pentane”, “Hexane”, “Methanol”, and “Ethanol”. No other fuel constituents can currently be modeled. The properties of the constituents are already contained inside the program as provided in the Annex 42 model specification.
Field: Constituent 1-12 Molar Fraction[LINK]
These fields describe the molar fraction of the fuel stream constituents. It is very important that the sum of the molar fractions add up to 1.0.
Outputs[LINK]
In addition to the following output variables, the resulting fuel heating values are also reported to the eio file.
Generator Fuel Compressor Electric Power [W][LINK]
This is the rate of energy use by the gas compressor, if any, that provides fuel at a higher pressure.
Generator Fuel Compressor Electric Energy [J][LINK]
This is the energy used by the gas compressor, if any, that provides fuel at a higher pressure.
Generator Fuel Compressor Skin Heat Loss Rate [W][LINK]
Convective heat gains to zone from gas compressor, if any, that provides fuel at a higher pressure.
Photovoltaic Generators[LINK]
EnergyPlus offers different options for predicting the electricity produced by solar electric photovoltaic (PV) panels. The three different options are “Simple”, “Equivalent One-Diode” and “Sandia” and the choice will determine the mathematical models used to determine energy production. The first allows the user to input an arbitrary efficiency. The other two models use empirical relationships to predict PV operating performance based on many environmental variables such as cell temperature. The PV models can be used with either normal PV modules or as part of a hybrid photovoltaic/thermal (PVT) flat plat collector.
The generator is connected to an Electric Load Center. The PV models refer to surface input objects defined elsewhere in the input file. This object describes an array that is “attached” to a surface object in order to describe its orientation and to access results of the solar insolation calculations. These can be either Heat Transfer or Shading objects (see Surfaces). This will define the orientation of the solar panel for the detailed models and also the area for the simple model. The exposure of that surface to incident solar radiation is calculated using the full set of models in EnergyPlus that are used to account for solar thermal loads arising from building windows and walls. Therefore the incident solar radiation is calculated to include the effects of shading and reflections from other surfaces declared in the input file. In addition to the output variables associated with PV models, there are numerous related output variables available for the surfaces including: ‘Surface Outside Face Sunlit Area’, ‘Surface Outside Face Sunlit Fraction’, ‘Surface Outside Face Incident Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Beam Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Sky Diffuse Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Ground Diffuse Solar Radiation Rate per Area’, ‘Surface Outside Face Beam Solar Incident Angle Cosine Value’, ‘Surface Outside Face Incident Sky Diffuse Ground Reflected Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Sky Diffuse Surface Reflected Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Beam To Beam Reflected From Surfaces Solar Radiation Rate per Area’, ‘Surface Outside Face Incident Beam To Diffuse Surface Reflected Solar Radiation Rate per Area’, and ‘Surface Outside Face Incident Beam To Diffuse Ground Reflected Solar Radiation Rate per Area.’ Note that it is possible to define a PV array area that doesn’t conform to the surface area (i.e. model a PV array area that is larger or smaller than what is available on the surface) so it is the users responsibility to not over-specify area when determining how many modules will fit onto a surface. However this type of input is allowed.
EnergyPlus does not include models for ancillary equipment for a PV array including charge controllers or power-point trackers. The operation of the entire electrical system that must go along with a PV array is not currently modeled in EnergyPlus and is therefore assumed to operate in ideal ways. The PV production models do not resolve voltage and current, only power (and energy). Electricity production is metered based on the output of the inverter. Output results are available before and after the inverter. One assumption is that the array is assumed to be always operating at the maximum power point. Energy production is based on the assumption that the quasi-steady power prediction is constant and continuous over the simulation timestep.
For a variety of reasons, actual installations of photovoltaics are often observed to exhibit system-level problems that significantly reduce electricity production. Therefore this modeling should be considered a method of bracketing the upper end of electricity production rather than an accurate prediction of what the panels will produce. Also note that the model predictions are closely related to the solar radiation data (typically of of TMY2 origin) in the EnergyPlus weather file, that the solar data in these is usually from a model rather than direct measurements, and that solar resources encountered by a real installation in a given year are likely to differ from the weather data file.
Generator:Photovoltaic[LINK]
This object is used to describe an array of PV modules and how they are to be modeled. A series of different PV arrays can be connected to a single electric load center (and inverter) by listing them all in an ElectricLoadCenter:Generator object.
Inputs[LINK]
Field: Name[LINK]
This field is a unique name for the PV array.
Field: Surface Name[LINK]
This field is the name of a surface that defines the location and geometry of the array.
Field: Photovoltaic Performance Object Type[LINK]
This field is the type of PV performance model. The choices are the class names for the three modeling options:
Field: Module Performance Name[LINK]
This is the name of the PV performance object define elsewhere (corresponding to the object type listed in the previous field)
Field: Heat Transfer Integration Mode[LINK]
The PV model allows for different ways of integrating with other EnergyPlus heat transfer surfaces and models and calculating cell temperature. For Building Integrated PV (BIPV), the “Integrated” options allow for the PV modeling to be coupled to the surface heat transfer models elsewhere in EnergyPlus. The user must select one of these options for this field:
Decoupled. The cell temperature of modules in the array is computed based on a energy balance relative to NOCT conditions. The input fields for Module Heat Capacity and Module Heat Loss Coefficient are ignored.
DecoupledUllebergDynamic the cell temperature is calculated based on a dynamic model developed by Ulleberg. The input fields for Module Heat Capacity and Module Heat Loss Coefficient are required.
IntegratedSurfaceOutsideFace The cell temperature is obtained from the outside face of the Surface:Heat Transfer named in the previous field. Energy exported by the module is removed from the heat transfer surface (at the position determined by the associated Construction with Internal Source). The input fields for Module Heat Capacity and Module Heat Loss Coefficient are ignored.
IntegratedTranspiredCollector The cell temperature is obtained from the collector surface temperature in the unglazed transpired collector model. Energy exported by the module is removed from the collector surface. The input fields for Module Heat Capacity and Module Heat Loss Coefficient are ignored.
IntegratedExteriorVentedCavity The cell temperature is obtained from the exterior baffle temperature in the naturally ventilated exterior cavity model. Energy exported by the module is removed from the exterior baffle surface. The input fields for Module Heat Capacity and Module Heat Loss Coefficient are ignored.
PhotovoltaicThermalSolarCollector The cell temperature is obtained from the photovoltaic/thermal solar collector model. If the PV layer is inside the collector, then the incident solar is modified by the photovoltaic/thermal solar collector model.
Field: Number of Series Strings in Parallel[LINK]
This field is the number of series-wired strings of PV modules that are in parallel to form the PV array. The product of this field and the next field should equal the total number of modules in the array.
Field: Number of Modules in Series[LINK]
This field is the number of modules wired in series (on each string) to form the PV array. The product of this field and the previous field should equal the total number of modules in the array.
Outputs[LINK]
Using the Generator:PV:Simple object makes a number of output variables available.\
Generator Produced DC Electric Power [W][LINK]
This output variable is the power of DC electricity produced by the PV array in Watts..
Generator Produced DC Electric Energy [J][LINK]
This output variable is the energy in DC electricity produced by the PV array, in Joules.
Generator PV Array Efficiency [ ][LINK]
This output variable is the resulting efficiency of the PV array .
The two more detailed PV models also have the following output variables.
Generator PV Cell Temperature [°C][LINK]
This output variable represents the temperature of the solar cell used in the calculation of cell performance.
Generator PV Short Circuit Current [A][LINK]
This output variable represents the short circuit current of the PV array, in Amps. This is provided to describe the I-V characteristics.
Generator PV Open Circuit Voltage [V][LINK]
This output variable represents the open circuit voltage of the PV array, in Volts. This is provided to describe the I-V characteristics.
PhotovoltaicPerformance:Simple[LINK]
The PhotovoltaicPerformance:Simple object describes a simple model of photovoltaics that may be useful for early phase design analysis. In this model the user has direct access to the efficiency with which surfaces convert incident solar radiation to electricity and need not specify arrays of specific modules. The full geometric model for solar radiation is used, including shading and reflections, to determine the incident solar resource. This model is intended to be useful for design purposes to quickly get an idea of the levels for annual production and peak power. The model can also accept arbitrary conversion efficiencies and does not require actual production units be tested to obtain performance coefficients.
Inputs[LINK]
Field: Name[LINK]
This field is the name of the PV array. The name is only used as an identifier. Multiple instances need have unique names.
Field: Fraction of Surface Area with Active Solar Cells[LINK]
This field is the user defined fraction for the area of surface named in the parent PV object that will have active PV cells on it. The area actually covered with solar cells will be the net area of the surface (gross area less any subsurfaces like windows) times the fraction entered here. This fraction includes the difference between PV module area and active cells within it and any losses for how closely packed modules can be arranged on surface. The value should be between 0.0 and 1.0.
Field: Conversion Efficiency Input Mode[LINK]
This field specifies how the PV array efficiency values are input. There are two choices, Fixed and Scheduled. If this field is set to ‘Fixed’ then the PV array always has the efficiency value specified in the next field. If this field is set to ‘Scheduled’ then the efficiency is determined by a user defined schedule named in the second field to follow.
Field: Value for Cell Efficiency if Fixed[LINK]
This field specifies the efficiency with which solar incident energy is converted to electricity. Efficiency = (electrical power generated [W])/(power of incident solar[W]). These efficiency values are dimensionless and should be between 0.0 and 1.0.
Field: Efficiency Schedule Name[LINK]
This field should be set to the name of schedule defined elsewhere in the input file. This schedule should specify dimensionless efficiency values between 0.0 and 1.0. This could be used for example to vary the efficiency to match results computed with more detailed models.
An example idf instance of this object follows:
PhotovoltaicPerformance:EquivalentOne-Diode[LINK]
This object describes the performance characteristics of Photovoltaic (PV) modules to be modeled using an equivalent one-diode circuit. This model is also known at the 4- or 5-parameter TRNSYS model for photovoltaics.
The following table shows several sample PV array types with their input values.
Where:
Shunt Resistance: the value of shunt resistance is finite only if the PV Module being modeled is a thin film variety. For all crystaline silicon modules the value is essentially infinite
Shunt Resistance value: 1,000,000 \(\Omega\) (ohms)
Module Heat Loss Coefficient: this value is dependent more on the array configuration than on the module itself.
Module Heat Loss Coefficient value: 30 W/m2-K
Module Heat Capacity: this is a typical value for a silicon based sandwich construction framed PV panel.
Module Heat Capacity Value: 50,000 J/m2-K
Reference Temperature: 298K (25C)
Insolation at Reference Conditions: 1000 W/m2
Ambient Temperature at NOCT conditions: 293K (20C)
Insolation at NOCT Conditions: 800 W/m2
Average tau-alpha Product: .9
Semiconductor Bandgap: 1.12 eV
Field: Name[LINK]
This field contains the uniqe name for the photovoltaic module performance data. The name is only used as an identifier.
Field: Cell Type[LINK]
This field is used to describe the type of technology used in the PV module. There are two options available, CrystallineSilicon and AmorphousSilicon. The choice affects the modeling.
Field: Number of Cells in Series[LINK]
This field is an integer representing the number of individual cells wired in series to make up a single module. The typical number for a 12V crystalline silicon PV module is 36.
Field: Active Area[LINK]
This field is the active area of the PV module in m2.
Field: Transmittance Absorptance Product[LINK]
This field indicates the transmittance-absorptance product at normal incidence angles for the PV modules. If the product is positive, that value will be used for all angles of incidence. If the value specified is negative, then the magnitude of the given value will be used for normal incidence and the IAM modifier correlation will be used for all other angles.
Field: Semiconductor Bandgap[LINK]
This field is the semiconductor bandgap for the PV material. The bandgap for silicon is 1.12 eV (electron volts).
Field: Shunt Resistance[LINK]
This field is the shunt (parallel) resistance (in ) in the single diode electrical model of the PV. The shunt resistance is effectively infinite for crystalline silicon based PV modules and is finite for thin film and exotic metal modules.
Field: Short Circuit Current[LINK]
This field is the short circuit current (in Amps) for an individual module in the PV array at reference conditions.
Field: Open Circuit Voltage[LINK]
This field is the open circuit voltage (in Volts) for an individual module in the PV array at reference conditions.
Field: Reference Temperature[LINK]
This field is the ambient temperature (in Kelvin) at reference conditions. The value is usually 298K
Field: Reference Insolation[LINK]
This field is the radiation level (in W/m2) at reference conditions. The value is usually 1000 W/m2.
Field: Module Current at Maximum Power[LINK]
This field is module current (in Amps) at the maximum power point and reference conditions.
Field: Module Voltage at Maximum Power[LINK]
This field is module voltage (in Volts) at the maximum power point and reference conditions.
Field: Temperature Coefficient of Short Circuit Current[LINK]
This field accounts for the fact that the module short circuit current is temperature dependent. The coefficient is given in Amps/Kelvin.
Field: Temperature Coefficient of Open Circuit Voltage[LINK]
This field accounts for the fact that the module open circuit voltage is temperature dependent. The coefficient is given in Volts/Kelvin.
Field: Nominal Operating Cell Temperature Test Ambient Temperature[LINK]
This field is the ambient temperature (in Kelvin) from the Nominal Operating Cell Temperature (NOCT) test. The value is usually 293 K
Field: Nominal Operating Cell Temperature Test Cell Temperature[LINK]
This field is the cell temperature (in Kelvin) from the Nominal Operating Cell Temperature (NOCT) test.
Field: Nominal Operating Cell Temperature Test Insolation[LINK]
This field is the insolation level (in W/m2) from the Nominal Operating Cell Temperature (NOCT) test. The value is usually 800 W/m2.
Field: Module Heat Loss Coefficient[LINK]
This field is the heat loss coefficient (in W/m2.K) for the array. The heat loss coefficient is dependent upon measures taken to actively or passively promote airflow over the array surface. The heat loss coefficient value is used only if the Integration and Cell Temperature Mode is set to “Decoupled Ulleberg Dynamic.”
Field: Total Heat Capacity[LINK]
This field is the heat capacity (in J/m2.K) of the modules in the array. It describes the module’s ability to store incident solar radiation internally. Such energy storage is manifested as a temperature increase in the modules that is considered to be undesirable. The total heat capacity value is used only if the Integration and Cell Temperature Mode is set to “Decoupled Ulleberg Dynamic.”
An IDF example:
PhotovoltaicPerformance:Sandia[LINK]
This ‘PhotovoltaicPerformance:Sandia’ object describes the performance of a single type of module. The model used with this object for predicting the electricity generated by photovoltaics is referred to as the Sandia model. This model is based on work done at Sandia National Lab, Albuquerque, NM by David King – with the help of many others.
This object describes performance input data needed for specific makes and models of production PV panels using the empirical coefficients assembled by Sandia National Laboratory. There are a large number of empirical coefficients required to use the Sandia model. These data are obtained after extensive measurements and data reduction. This testing has been performed for some types of production panels and Sandia publishes a database of module and array performance parameters on the web at www.sandia.gov/pv. The entries in the database as of January 15, 2004 were converted to idf segments and are included with the EnergyPlus release in the library file SandiaPVData.imf. There are more than hundred different module types included in the library and identified by the manufacturer’s model names listed at the beginning of the file SandiaPVData.imf. This data library file is arranged for use with EpMacro but the user can also copy .idf segments directly from the macro data set.
The Sandia model itself can aggregate multiple PV modules. Therefore, an instance of a ‘PhotovoltaicPerformance:Sandia’ object could actually represent an array of modules as well as the more usual single module. These can be can be thought of as simple larger modules and used by Generator:PV:Sandia objects in the usual manner.
The many empirical coefficients for the model are listed below and are described in more more detail in the EnergyPlus engineering documentation EngineeringDoc.pdf.
The field descriptions below focus on providing the parameter’s variable name as identified in the Sandia database. See the the EngineeringDoc.pdf for details on how the input fields are used in the correlations. The user generally would not need to worry about the details of the fields since he/she is not likely to generate the data on their own.
Inputs[LINK]
Field: Name[LINK]
This field provides a unique name for the PV module. This is often the manufacturer’s identifier for a particular model of a PV module.
Field: Active Area[LINK]
Units m2 , real number, area of active solar electric cell for the entire module.
Field: Number of Cells in Series[LINK]
“Series_Cells” in Sandia Database.
Field: Number of Cells in Parallel[LINK]
“Parallel_Cells” in Sandia Database
Field: Short-Circuit Current[LINK]
“Isco” in Sandia Database. Short-circuit current is a basic parameter Typically supplied by manufacturers at Standard Report Conditions. (Amps)
Field: Open-Circuit Voltage[LINK]
“Voco” in Sandia Database, Open-circuit voltage is a basic parameter typically provided by manufacturers a t Standard Report Conditions. (Volts)
Field: Current at Maximum Power Point[LINK]
“Impo” in Sandia Database. Current at maximum powerpoint is a basic parameter provided by manufacturers at Standard Report Conditions. (Amps)
Field: Voltage at Maximum PowerPoint[LINK]
“Vmpo” in Sandia Database. Voltage at maximum powerpoint is a a basic parameter typically provided by manufacturers a t Standard Report Conditions. (Volts)
Field: Sandia Database Parameter aIsc[LINK]
“aIsc in Sandia Database” (1/degC)
Field: Sandia Database Parameter aImp[LINK]
“aImp” in Sandia Database (1/degC)
Field: Sandia Database Parameter c0[LINK]
“C0” in Sandia Database, (non-dimensional)
Field: Sandia Database Parameter c1[LINK]
“C1” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter Bvoc0[LINK]
“Bvoco” in Sandia Database (Volts/degC)
Field: Sandia Database Parameter mBVoc[LINK]
“mBVoc” in Sandia Database (Volts/degC)
Field: Sandia Database Parameter BVmp0[LINK]
“Bvmpo” in Sandia Database (Volts/degC)
Field: Sandia Database Parameter mBVmp[LINK]
“mBVmp” in Sandia Database (Volts/degC)
Field:Diode Factor[LINK]
“n” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter c2[LINK]
“C2” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter c3[LINK]
“C3” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a0[LINK]
“A0” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a1[LINK]
“A1” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a2[LINK]
“A2” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a3[LINK]
“A3” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a4[LINK]
“A4” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b0[LINK]
“B0” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b1[LINK]
“B1” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b2[LINK]
“B2” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b3[LINK]
“B3” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b4[LINK]
“B4” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b5[LINK]
“B5” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter Delta(TC)[LINK]
“d(Tc)” in Sandia Database (deg C)
Field: Sandia Database Parameter fd[LINK]
“fd” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter a[LINK]
“a” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter b[LINK]
“b” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter c4[LINK]
“C4” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter c5[LINK]
“C5” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter Ix0[LINK]
“Ix0” in Sandia Database (Amps)
Field: Sandia Database Parameter Ixx0[LINK]
“Ixx0” in Sandia Database (Amps)
Field: Sandia Database Parameter c6[LINK]
“C6” in Sandia Database (non-dimensional)
Field: Sandia Database Parameter c7[LINK]
“C7” in Sandia Database (non-dimensional)
An example of the object follows:
When using EpMacro with an typical installation of EnergyPlus, the above entry can be included in an input file by adding the following two lines to an input macro file (*.imf).
Generator:WindTurbine[LINK]
A wind turbine is a component that converts the kinetic energy of the surrounding airstream into electricity. This model is intended to calculate the electrical power that a wind turbine system produces. The performance of wind turbine systems is dependent on the local environmental conditions such as wind speed and density of air at the height of the systems. An analysis of these conditions is necessary to accurately estimate power output. The model obtains the weather information from the weather data file in EnergyPlus and then determines the wind speed and air density at the specific height of the system. It also requires the user to input the annual average wind speed measured at the local site and the height of the measurement so that it factors in differences between the weather file wind data and the local wind data.
The model employs the general kinetic energy equation to calculate the performance characteristics of the horizontal axis wind turbine (HAWT) systems. It provides a simple approximation algorithm when the power coefficient, Cp, is available which represents the efficiency of the wind turbine in the wind power extraction from the ambient air stream. It also allows the user to input experimental constants so that the power coefficient can precisely be determined according to the characteristic of the airfoil of the system. As for the vertical axis wind turbine (VAWT) systems, it employs the general mathematical equations for straight-bladed Darrieus-type VAWT systems, which are common to VAWT systems. Various types of VAWT systems such as the Savonius-type and the curved-blade (or Egg-beater) type may be simulated with this same model.
It includes two different types of dynamic power control: FixedSpeedFixedPitch (FSFP) and VariableSpeedFixedPitch (VSFP). Currently, it does not include an algorithm for modeling pitch control such as FixedSpeedVariablePitch (FSVP) and VariableSpeedVariablePitch (VSVP). If the control type of the wind turbine is either FSVP or VSVP, the control type of VSFP will be assumed. In addition, constant power generation is assumed when the ambient wind speed is between the rated wind speed and the cut out wind speed, if the user specifies one of the last three options. The model also has the ability to account for transient losses associate with the power produced during dynamic control by a user-specified fraction.
The model does not include detailed algorithms for generators and inverters due to concerns for computational convergence, time, and usability. Instead, all conversion losses of these subsystems are included by applying a user-supplied total system efficiency to the maximum power extraction of the wind turbine. The field of the total system efficiency must be specified by the user.
Inputs[LINK]
Field: Name[LINK]
A unique user assigned name for a particular wind turbine system. Any reference to this unit by another object will use this name.
Field: Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes whether the wind turbine system can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit is off and will not operate for the time period. If this field is blank, the schedule has values of 1 for all time periods.
Field: Rotor Type[LINK]
This field is the type of axis of the wind turbine. The user specifies either a horizontal axis wind turbine or a vertical axis wind turbine. Each type of wind turbine employs a different algorithm for the calculation of the electrical power output of the wind turbine. The default value is HorizontalAxisWindTurbine.
Field: Power Control[LINK]
This field is the type of rotor control for the wind turbine. This protects the system against the overloading for a system with no speed or pitch control and also to maximize the energy yield for the system. Four different control types are classified in the literature: FixedSpeedFixedPitch (FSFP), FixedSpeedVariablePitch (FSVP), VariableSpeedFixedPitch (VSFP), and VariableSpeedVariablePitch (VSVP). Currently, FSFP and VSFP types can be modeled in EnergyPlus. The other two types will be modeled as VSFP. If the first FSFP control type is chosen, the model assumes the maximum power at a fixed rotor speed when the power output predicted is greater than the maximum until the rotor speed reaches the maximum wind speed (see next field). If one of the last three control options is chosen, the model assumes that the system produces a constant power at the rated wind speed when the wind speed is between the rated wind speed and cut-out wind speed. The default value is VariableSpeedFixedPitch (VSFP).
Field: Rated Rotor Speed[LINK]
This field is the maximum rotational speed of the rotor at the rated power of the wind turbine in rev/min (revolution per minute). It is used to determine the tip speed ratio of the rotor and relative flow velocity incident on a single blade of the VAWT systems.
Field: Rotor Diameter[LINK]
This field is the diameter of the rotor in meters. Note that this field is not the height of the blade, but the diameter of the perpendicular circle from the vertical pole in the VAWT systems. It determines the swept area of the rotor of the HAWT systems and the chordal velocity of the VAWT systems.
Field: Overall Height[LINK]
This field is the height of the hub of the HAWT system, or of the pole of the VAWT system in meters. It is necessary to estimate local air density and the wind speed at this particular height where the wind turbine system is installed.
Field: Number of Blades[LINK]
This field is the number of blades of the wind turbine. The azimuth angle of the rotor of the VAWT system is determined by dividing 360 degree by this field so that the model determines the chordal velocity component and the normal velocity component of the system. The default value is 3.
Field: Rated Power[LINK]
This field is the nominal power output of the wind turbine system at the rated wind speed in Watts. Note that the user should input the maximum power of the system with no control, i.e., FSFP control type, can physically produce. Manufacturers’ data also indicates it as “peak power” or “rated capacity”. If the local wind speed is greater than the rated wind speed, the model assumes constant power output of this field.
Field: Rated Wind Speed[LINK]
This field is the wind speed that the wind turbine system indicates the peak in the power curve in m/s. The system produces the maximum power at this speed and the speed of the rotor is managed based on this wind speed.
Field: Cut In Wind Speed[LINK]
This field is the lowest wind speed where the wind turbine system can be operated in m/s. No power generation is achieved as long as the ambient wind speed is lower than this speed.
Field: Cut Out Wind Speed[LINK]
This field is the greatest wind speed in m/s. When the wind speed exceeds this value, the wind turbine system needs to be stopped because of inefficiencies in the system. All systems that have either pitch or speed control must be stopped when the ambient wind speed exceeds this speed. Note that the user should input a wind speed above which physical damage to the system might be caused in the case of a FSFP system. It appears as “extreme/survival/design wind speed” in the literature. The system will be turned off when the ambient wind speed is over this speed.
Field: Fraction System Efficiency[LINK]
This field is the overall system efficiency of the wind turbine system. It includes all the conversion losses as well as transient losses during the dynamic control when the ambient wind speed is between the rated wind speed and cut-out wind speed (see previous fields). The user also has the ability to specify delivery losses from the system to the local area. If the user does not enter a fraction, the model assumes the default value of 0.835. Note that the fraction must be between zero and one.
Field: Maximum Tip Speed Ratio[LINK]
This field is the maximum tip speed ratio between the rotor velocity and ambient wind velocity. The rotor speed varies with this ratio to maximize the power output when the rotor control types are variable speed ones. This field allows the user to adjust the power output from the particular system or to find the optimal tip speed ratio of the system. Optimal tip speed ratio is dependent on the number of blades. It is typically about 6, 5, and 3 for two-bladed, three-bladed, and four-bladed rotor, respectively. For the vertical axis wind turbine, it is smaller than horizontal axis wind turbine, and varies with the chord area. The default and maximum values are 5.0 and 12.0.
Field: Maximum Power Coefficient[LINK]
This field is the maximum fraction of power extraction from ambient wind. If the user inputs this field, the simple approximation model is assumed. The model simply employs the value of this field into the general kinetic energy equation, so that the power output is obtained. The user can obtain this field with a simple calculation from the power curve published in almost all manufacturers’ specifications by using the kinetic energy equation as:
\[{C_p} = \frac{P}{{0.5\rho A{V^3}}}\]
where
P = power production at the rated wind speed [W]
ρ = density of air [kg/m3]
A = swept area of rotor [m2]
V = rated wind speed [m/s]
Cp= power coefficient
The maximum and default values are 0.59 and 0.35.
Field: Annual Local Average Wind Speed[LINK]
This field is the local annual average wind speed that represents a representative wind profile at the location of the system in m/s. It is used to factor the difference in wind speed between the weather file wind data and the locally measured wind data so that the model minimizes uncertainties caused by improper wind data at the particular location. Considerable differences between the weather file wind data and the local wind data typically appear. The user thus needs to enter this field in order to obtain accurate local wind data. The model internally determines a multiplier and it is multiplied by the weather file wind data adjusted at the height of the system. If this field is not entered, then the model will use the wind speed from the design day or weather file information with only adjustment at the height of the rotor.
Field: Height for Local Average Wind Speed[LINK]
This field is the height that the local wind speed is measured in meters. The annual average wind speed (see previous field) input by the user is internally recalculated by existing EnergyPlus functions at the height of the local station. This modified wind speed is then factored and applied to the weather file wind data. If the annual local average wind speed is not entered, this field is then assumed as zero. The minimum and default values are zero and 50 meters.
Field: Blade Chord Area[LINK]
This field is the blade chord area of a single blade of VAWT system in m2. It is necessary to determine the net tangential and normal forces of a single blade.
Field: Blade Drag Coefficient[LINK]
This field is the blade drag coefficient for a specific blade. It is for determining the tangential and normal force coefficients with the blade lift coefficient (see next field) so that the model can calculate the power output from the system. The user should be able to obtain this parameter for a specific blade from the manufacturers’ data. This field is only valid for VAWT systems.
Field: Blade Lift Coefficient[LINK]
This field is the blade lift coefficient for a specific blade. It is for determining the tangential and normal force coefficients with the blade drag coefficient (see previous field) so that the model can calculate the power output from the system. The user should also be able to obtain it for a specific blade from the manufacturers’ data. This field is only valid for VAWT systems.
Field: Power Coefficient Parameter
These six fields are the parameters for the power coefficient equation shown below. These fields are used to determine the power coefficient of the system. The analytical approximation model of the power coefficient in EnergyPlus is:
\[{C_p} = {C_1}(\frac{{{C_2}}}{{{\lambda _i}}} - {C_3}\theta - {C_4}{\theta ^x} - {C_5}){e^{ - \frac{{{C_6}(\lambda ,\theta )}}{{{\lambda _i}}}}}\]
with
\[\frac{1}{{{\lambda _i}}} = \frac{1}{{\lambda + 0.08\theta }} - \frac{{0.035}}{{{\theta ^3} + 1}}\]
where
Cp = power coefficient
C~1- 6~ = empirical power coefficient parameters
λ = tip speed ratio (often known as TSR)
λi = tip speed ratio at ith time step
θ = azimuth angle of the pitch, 0 [degree]
If the user does not input any field of these parameters, the simple approximation model for the power coefficient will be used (see previous maximum power coefficient field). That is, the analytical approximation model of the power coefficient will be chosen only if the user inputs all these six parameters. The user also has the ability to modify each parameter when the specific value of the system is available. The default values are given in the table below.
These fields are only valid for HAWT systems.
An example input for the wind turbine is shown in below.
Outputs[LINK]
Generator Produced Electric Power [W][LINK]
This report is the electric power that the wind turbine system produces.
Generator Produced Electric Energy [J][LINK]
This report is the electric energy that the wind turbine system produces.
Generator Turbine Local Wind Speed [m/s][LINK]
This report is the local wind speed at the specific height of the wind turbine.
Generator Turbine Local Air Density [kg/m3][LINK]
This report is the local density of the air at the specific height of the wind turbine.
Generator Turbine Tip Speed Ratio [][LINK]
This report is the ratio between the rotational speed of the tip of the blades and the ambient wind speed at the height of the hub or pole of the wind turbine.
Generator Turbine Power Coefficient [][LINK]
This report represents the efficiency of the power extraction from the ambient wind of the wind turbine. It is function of the tip speed ratio and pitch angle. It is only valid for HAWT systems.
Generator Turbine Chordal Component Velocity [m/s][LINK]
This report is the axial velocity component along the chord of the wind turbine system. It is only valid for VAWT systems.
Generator Turbine Normal Component Velocity [m/s][LINK]
This report is the axial velocity component of the rotor of the wind turbine system. It is only valid for VAWT systems.
Generator Turbine Relative Flow Velocity [m/s][LINK]
This report is the local relative flow velocity that represents actual direction and velocity incident on the blades. It is the square root of the sum of both chordal velocity component and normal velocity component. It is only valid for VAWT systems.
Generator Turbine Attack Angle [deg][LINK]
This report is the azimuth angle between the relative flow velocity and the plane of chord. It varies as the wind speed increases, so that the lift and drag forces change.
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This documentation is made available under the EnergyPlus Open Source License v1.0.