Tips and Tricks for Using EnergyPlus — EnergyPlus 8.4

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Using OSC (Other Side Coefficients) to create controlled panels[LINK]

The Other Side Coefficient (OSC) equation permits setting either the outside surface temperature or the outside air temperature to a constant value or a scheduled value based on the size of the first input parameter, N1. The original temperature equation was:

T=N2Tzone+N3Toadb+N4N5+N6Tgrnd+N7WspdToadb

where:

  • T = Outside Air Temperature when N1 (Combined convective/radiative film Coeff) > 0

  • T = Exterior Surface Temperature when N1 (Combined convective/radiative film Coeff) < = 0

  • Tzone = MAT = Temperature of the zone being simulated (°C)

  • Toadb = Dry-bulb temperature of the outdoor air (°C)

  • Tgrnd = Temperature of the ground (°C) Wspd = Outdoor wind speed (m/sec)

The coefficients N2, N3, N4, N6, and N7 scale the contribution of the various terms that follow them. In the case of N4, it is followed by another term N5. This is a constant temperature that can also be overridden by a scheduled value. Note that in some EnergyPlus documentation, the N’s are given as C’s.

This object has been changed to permit the outside temperature, T, to be controlled to a set point temperature that is specified as N5 or comes from the schedule A2.

Note that since the surface that contains the panel subsurfaces (that must be called doors in EnergyPlus) receives that same outside temperature as the panels, it should have a construction with a very high thermal resistance to essentially take it out of the room heat balance calculation.

An Example input file object is shown below.

SurfaceProperty:OtherSideCoefficients,
  Zn001:Roof001:OSC, !- Name
  0,   ! (N1) Combined Convective/Radiative Film Coefficient {W/m2-K}
  0,   ! (N5) Constant Temperature {C}
  0.95,!(N4) Constant Temperature Coefficient
  ,    ! (N3)External Dry-Bulb Temperature Coefficient
  ,    ! (N6)Ground Temperature Coefficient
  ,    ! (N7)Wind Speed Coefficient
  -.95,! (N2) Zone Air Temperature Coefficient
  ConstantCooling,     ! (A2) Constant Temperature Schedule Name
  No,  ! (A3)Sinusoidal Variation of Constant Temperature Coefficient
  24,  ! (N8)Period of Sinusoidal Variation {hr}
  1.,  ! (N9)Previous Other Side Temperature Coefficient
  5.,  !(N10) Minimum Other Side Temperature Limit
  25.; ! (N11) Maximum Other Side Temperature Limit

This object results in the following equation for T:

T = 1.0*Tlast +0.95*(Tsetpoint – TzoneAir) (with limits)

The result of this is that the surface temperature, T, will be changed to the temperature that will force the zone air temperature to the setpoint providing the temperature limits are not reached. When the zone air temperature is at the setpoint, T remains at the value it had in the prior time step.

A complete example with all pertinent objects:

Construction,
  PanelConst,              !- Name
  Std Steel_Brown_Regular; !- Outside Layer


  Material,
  Std Steel_Brown_Regular, !- Name
  Smooth,                  !- Roughness
  1.5000000E-03,           !- Thickness {m}
  44.96960,                !- Conductivity {W/m-K}
  7689.000,                !- Density {kg/m3}
  418.0000,                !- Specific Heat {J/kg-K}
  0.9000000,               !- Thermal Absorptance
  0.9200000,               !- Solar Absorptance
  0.92000000;              !- Visible Absorptance


  BuildingSurface:Detailed,
  Zn001:Roof001,           !- Name
  Roof,                    !- Surface Type
  ROOF31,                  !- Construction Name
  ZONE ONE,                !- Zone Name
  OtherSideCoefficients,   !- Outside Boundary Condition
  Zn001:Roof001:OSC,       !- Outside Boundary Condition Object
  NoSun,                   !- Sun Exposure
  NoWind,                  !- Wind Exposure
  0,                       !- View Factor to Ground
  4,                       !- Number of Vertices
  0.000000,15.24000,4.572,  !- X,Y,Z = = &gt; Vertex 1 {m}
  0.000000,0.000000,4.572,  !- X,Y,Z = = &gt; Vertex 2 {m}
  15.24000,0.000000,4.572,  !- X,Y,Z = = &gt; Vertex 3 {m}
  15.24000,15.24000,4.572;  !- X,Y,Z = = &gt; Vertex 4 {m}


  FenestrationSurface:Detailed,
  panel002,                !- Name
  Door,                    !- Surface Type
  PanelConst,              !- Construction Name
  Zn001:Roof001,           !- Building Surface Name
  ,                        !- Outside Boundary Condition Object
  autocalculate,           !- View Factor to Ground
  ,                        !- Shading Control Name
  ,                        !- Frame and Divider Name
  1,                       !- Multiplier
  4,                       !- Number of Vertices
  3,2,4.572,  !- X,Y,Z = = &gt; Vertex 1 {m}
  3,3,4.572,  !- X,Y,Z = = &gt; Vertex 2 {m}
  4,3,4.572,  !- X,Y,Z = = &gt; Vertex 3 {m}
  4,2,4.572;  !- X,Y,Z = = &gt; Vertex 4 {m}


  SurfaceProperty:OtherSideCoefficients,
  Zn001:Roof001:OSC,       !- Name
  0,            !- Combined Convective/Radiative Film Coefficient {W/m2-K}
  0,                       !- Constant Temperature {C}
  0.95,                    !- Constant Temperature Coefficient
  ,                        !- External Dry-Bulb Temperature Coefficient
  ,                        !- Ground Temperature Coefficient
  ,                        !- Wind Speed Coefficient
  -.95,                    !- Zone Air Temperature Coefficient
  ConstantTwentyTwo,       !- Constant Temperature Schedule Name
  No,           !- Sinusoidal Variation of Constant Temperature Coefficient
  24,                      !- Period of Sinusoidal Variation {hr}
  1.,                      !- Previous Other Side Temperature Coefficient
  5.,                      !- Minimum Other Side Temperature Limit {C}
  25.;                     !- Maximum Other Side Temperature Limit {C}


  Schedule:Constant,ConstantTwentyTwo,PanelControl,22;