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How to Collect Electrical and Environmental Parameters from an OpenStudio Model for an AHU Unit?

asked 2025-06-18 08:57:39 -0500

Olivia_casta's avatar

updated 2025-06-18 09:54:10 -0500

I am working with a pre-built model sourced from NREL and am trying to collect specific data from the OpenStudio (OS) model for an Air Handling Unit (AHU). The parameters I need to extract include:

  • Current
  • Voltage
  • Energy
  • Temperature (air and water)
  • Pressure
  • Airflow
  • Energy consumption

However, from the simulation results, I can only access data for the following components:

  • CORE_ZN
  • PERIMETER_ZN_ (1-4)
  • PSZ-AC (1-5)
  • DesPer 1-17, including:
    • Des Heat Mass Flow [kg/s]
    • Des Heat Capacity [W]
    • Des Cooling Mass Flow [kg/s]
    • Des Sensible Cooling Capacity [W]
    • Des Total Cooling Capacity [W]

How can I access the additional parameters, such as current, voltage, and energy consumption, from the OpenStudio model for the AHU unit?

here I'm sahring the drive link: https://drive.google.com/drive/folder...

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answered 2025-06-23 14:13:47 -0500

updated 2025-06-23 14:18:56 -0500

Partial answers ...


On voltage, current, power and energy. To the best of my knowledge, EnergyPlus only reports on power (W), and consequently on energy (J), for the vast majority of its "energy-consuming" object classes. Exceptions would be generators (e.g. PV) and transformers - AHUs wouldn't normally fall in that category.

Many similarly-named output variables can be reported either in W or in J. One can either request both W and J output variable variants, or post-process J from (i) reported W and (ii) defined timestep duration (e.g. 5 min = 300 s). I usually only request time series data in W, and do my post-processing from there (e.g. to tally GJ).

If ones postulates that a RTU operates at 240 V, then one can isolate current from P = I x V. I know, that's very basic. But for the purposes of building energy simulation, fixed voltage (e.g. 240 V) seems like a reasonable assumption.


On missing output variables. An EnergyPlus-generated run/eplusout.rdd file contains all admissible output variables, specific to your IDF. So if what you're after isn't there, then you're out of luck. You know what objects you're interested in, so the best is to search (e.g. CTRL-F) known keywords in the .rdd file.

It looks like your model is a variant of the US DOE Prototype SmallOffice model, and so I tested this with another variant of the SmallOffice I keep in some of my repositories (like this one). As with your model, I requested all (557) possible output variables (listed in the OpenStudio Application), and enabled the following (just in case):

OS:Output:Diagnostics,
  {fd2b9480-2f48-497a-96c6-b7ed055c5b05}, !- Handle
  DisplayAdvancedReportVariables;         !- Key 1

As expected, around 200 requested output variables weren’t generated by EnergyPlus (as reported in the run/eplusout.err file). This is expected for the vast majority of reported failures: for instance, any requested variables on fuels (e.g. diesel) or fluids (e.g. steam) will fail if these are not present in the model (fair enough).

Yet a few failures seemed odd to me. I filed an EnergyPlus issue, and a similar OpenStudio issue, on (now) unavailable output variables. Not sure if any of the variables you're looking into fall in some similar situation.

Hope this helps.


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Thank you for all your help and for taking the time to respond to my UMH post — I really appreciate it. I’ll review your answer in detail and will be sure to update and mark it accordingly on Unmethours.

Thanks again for your continued support!

Olivia_casta's avatar Olivia_casta  ( 2025-06-24 09:54:18 -0500 )edit

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Asked: 2025-06-18 08:57:39 -0500

Seen: 118 times

Last updated: Jun 24