Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
That "Number of Simulation Processes" option you see in EP-Launch is NOT referenced if you run a single EnergyPlus Input Data file (#.idf). It is ONLY referenced if you run an EnergyPlus Group file (#.epg), which is really one large file that is a combination of multiple #.idf files. If you read more about these group files in the Auxiliary Programs documentation, you can create a #.epg file using a wizard that allows you to select multiple #.idf files to combine. This wizard also allows you to choose multiple weather files to use, in case your analysis requires different locations.
OpenStudio DOES NOT reference this "Number of Simulation Processes" option, since it doesn't have the capability of running simultaneous simulations. That's what it's "sister" program Parametric Analysis Tool (PAT) is for. Using PAT requires the application of measures to a baseline OpenStudio model, where you can then combine measures to form different simulation cases to compare to the baseline.
You can read more from a similar Unmet Hours question about parametric EnergyPlus simulations HERE.
When simulation time reaches multiple days, I'd seriously look into simplifying the model. You can reduce envelope heat transfer calculations by combining window surfaces (as long as you're not worried about accurate daylight modeling) and by using an area-weighted average U-value for a large opaque surface that represents combination of multiple opaque surfaces. As long as the overall heat transfer properties are the same (UA, h, absorptance, etc.) EnergyPlus will calculate heat transfer the same. Once the envelope has been simplified, the next place to analyze is the number of zones in the model and if they can be combined in any way.
| | 2 | No.2 Revision |
That "Number of Simulation Processes" option you see in EP-Launch is NOT referenced if you run a single EnergyPlus Input Data file (#.idf). It is ONLY referenced if you run an EnergyPlus Group file (#.epg), which is really one large file that is a combination of multiple #.idf files. If you read more about these group files in the Auxiliary Programs documentation, you can create a #.epg file using a wizard that allows you to select multiple #.idf files to combine. This wizard also allows you to choose multiple weather files to use, in case your analysis requires different locations.
OpenStudio DOES NOT reference this "Number of Simulation Processes" option, since it doesn't have the capability of running simultaneous simulations. That's what it's "sister" program Parametric Analysis Tool (PAT) is for. Using PAT requires the application of measures to a baseline OpenStudio model, where you can then combine measures to form different simulation cases to compare to the baseline.
You can read more from a similar Unmet Hours question about parametric EnergyPlus simulations HERE.
When simulation time reaches multiple days, I'd seriously look into simplifying the model. You can reduce envelope heat transfer calculations by combining window surfaces (as long as you're not worried about accurate daylight modeling) and by using an area-weighted average U-value for a large opaque surface that represents combination of multiple opaque surfaces. As long as the overall heat transfer properties are the same (UA, h, absorptance, etc.) EnergyPlus will calculate heat transfer the same. Once the envelope has been simplified, the next place to analyze is the number of zones in the model and if they can be combined in any way.
If you are checking errors, it may help to run the design / sizing period(s), and then use the weather file to run 2-3 weeks around the design day(s) instead of the entire year. This will really shorten simulation time and give you results around times when errors are likely to occur.
