Using ReadVarsESO[LINK]

Creating Charts and Spreadsheet files from Output Variables[LINK]

The ReadVarsESO program is distributed with EnergyPlus as a simple approach to converting the standard output files (eplusout.eso, eplusout.mtr) into files that can be put directly into a spreadsheet program and then used to create graphs or do other statistical operations. ReadVarsESO can read the complex output files and sort the data into time-based form, it is a very quick application but does not have a lot of features. Note that all the Output:Meter and Output:Meter:Cumulative objects are included on the eplusout.eso file as well as the eplusout.mtr file. You can choose the Output:Meter:MeterFileOnly or Output:Meter:Cumulative:MeterFileOnly objects if you do not want a particular meter to show up on the eplusout.eso file. If you wish to see only the metered outputs, the eplusout.mtr file will typically be a lot smaller than the eplusout.eso file.

The ReadVarsESO program has a very simple set of inputs. By default, you will get all the variables listed in the Output:Variable (eplusout.eso) or Output:Meter (eplusout.mtr) objects into the appropriate output files, and the outputs will be limited to 255 variables (a legacy Microsoft Excel^TM limit). You can tailor how many variables to list by specifying variables for the ReadVarsESO runs.

You can override the 255 variable limit by specifying an argument on the command line (EP-Launch has a special option for this). You use “unlimited” or “nolimit” on the command line to get as many variables into your output file as desired. Again, this will be limited either by the number of variables in the eplusout.eso or eplusout.mtr files or the contents of the “rvi” file. If you want to use this option, you must include two arguments to the command line of the ReadVars program – 1) the “rvi” file and 2) the “unlimited” argument.

By default, ReadVarsESO also included a trailing space on the header line, which can result in parsing difficulties, since the last variable will essentially have a blank character at the end. In EnergyPlus 9.0, a new command line option (fixheader) was added to ReadVarsESO to allow eliminating this extra padding. Just like with the variable limit command line argument, to use this one, you must first include an argument for the rvi file, which is a required first positional argument. If you aren’t using an rvi file, just include blank quotes to indicate no rvi use while satisfying the ReadVarsESO argument requirements.

In addition, another argument can be used so that the output file is only one time frequency. (By default, all variables – hourly, monthly, annual, etc. are mixed together in the output file). By using “Timestep” as an argument, you would get only the TimeStep reported variables. Using “Monthly”, only the monthly variables. This is not automated in either EP-Launch or the RunEPlus batch file but can easily be accomplished.

The program is run automatically from the EP-Launch program or the RunEPlus batch file (both these methods for executing EnergyPlus are described in the GettingStarted document). These programs use <filename>.rvi for input to the ReadVarsESO program executed first after the EnergyPlus execution and <filename>.mvi for the second execution. Ostensibly, the .rvi file would apply to the eplusout.eso file and the .mvi would apply to the eplusout.mtr file, BUT the contents of the files actually specify the “input” reporting file and the “output” reorganized file. Typical contents of an .rvi file are:

Note that the first two lines of the file are “input file” (where to read the output variable values from) and “output file” (where to put the reorganized data). If you have only those two lines in an “rvi” file, the program will use all the available variables on indicated input file to produce the output.

ReadVarsESO takes the input stream but recognizes the date/time information and appropriately places the required data onto the “output file”. Following these lines are a list of variables to be culled from the “input file” and placed onto the output file. “Variable Name” will take all variables matching that description whereas “Specific Variable Name” will only match the full description of the variable. So, in the above example, “Zone Air Temperature" will report air temperatures for all the zones (but available at the HVAC timestep if you choose the “detailed” reporting frequency in your input file) but “AIR LOOP OUTLET NODE” and “COOLING COIL AIR OUTLET NODE” will be the only values reported for the “System Node Temperature” variable (the node temperature is available for all nodes used in the simulation). The termination line (0) is included to terminate the input to the ReadVarsESO program and begin the scanning.

The output from ReadVarsESO is in the form commonly called “comma de-limited” or “comma separated variable”. This format can be read easily in spreadsheet programs, such as Excel^TM.

Note as described in the “Input for Output” above, only variables as listed on the eplusout.rdd file are available for reporting. If you request others, they will become “Warning” messages in the eplusout.err file.

** Warning ** The following Output variables were requested but not generated
**   ~~~   ** because IDF did not contain these elements or misspelled variable name -- check .rdd file
************* Key = *, VarName = SYSTEM SENSIBLE COOLING RATE

The above message was generated from an IDF that requested reporting of the “SYSTEM SENSIBLE COOLING RATE” but that variable was not available from the components in the execution.