How to calculate thermal (cooling and heating) loads in EnergyPlus without designing HVAC system?
Hi,
I want to determine the overall cooling and heating load in my EnergyPlus model, without designing the actual HVAC system - this will serve as my baseline model, the results of which I can compare with "advanced" (modified) EnergyPlus model.
The only way I came across to do this is via defining an object in EnergyPlus called ZoneHVAC:IdealLoadsAirSystem.
Further, the Output:Variables which can help to estimate this are:
- Zone Ideal Loads Zone Total Heating Rate
- Zone Ideal Loads Zone Total Cooling Rate
- Zone Air System Sensible Heating Rate
- Zone Air System Sensible Cooling Rate
Can anyone from the community help me in understanding if I am on the right track pertaining to the above mentioned, if not, how can I achieve this effectively? - any sort of guidance will be welcomed and appreciated.
Apologies, if the question is not clear enough.
Thank you!
Edit-1:
Comments
@Denis Bourgeois thank you again, for clarifying my doubt on this. Regarding the files, I indeed referred to the "/5Zone_IdealLoadsAirSystems_ReturnPlenum.idf" - the same which you have referred to in your comment. It certainly was of help.
Another question, shouldn't both the sensible and latent thermal (cooling/heating) rates be taken into account for assessing the loads?
"[...] shouldn't both the sensible and latent thermal (cooling/heating) rates be taken into account"? From the IO Reference: "All of the ZoneHVAC:IdealLoadsAirSystem loads and energy use are reported for Sensible Heating, Latent Heating, Total Heating, Sensible Cooling, Latent Cooling, and Total Cooling". I may be misunderstanding your question.
@Denis Bourgeois actually what made me to ask this question is I was looking at the results generated by the EnergyPlus model for a weather environment classified as 1A. This is highly hot climate. When I compared the sensible and latent cooling loads, sensible loads turned out to be much higher - I was expecting latent cooling loads to be higher, but I understand this is mainly driven by the outdoor humidity than the People occupying the buildings? - I hope my question is clearer?
@MHW, I would indeed expect outdoor humidity driving latent cooling loads (more so than internal loads) in CZ1A (hot & humid). Although this would ultimately depend on what's going on in that facility (e.g. greenhouse? industrial laundry/cleaning?), and on selected "Dehumidification Control" options. Fortunately, the ZoneHVAC:IdealLoadsAirSystem object allows you to output/compare "Outdoor Air" vs "Supply Air" vs "Zone" Latent Cooling Energy. You can do the same for Sensible or Total, allowing you to pinpoint when/where sensible vs latent loads are being picked up.
@Denis Bourgeois perfect that clarified my doubts to a greater level. I think the "Humidification/Dehumidification Control" might be a factor too which influences the latent heating and cooling loads, as the aim is to maintain humidity close to 50%.
I have attached the image of the "IdealLoadsAirSystem" under Edit-1 of the original question. This is from my current (baseline) model. Since, the "Humidification Control" is chosen to be "None" - it might be leading to low latent thermal loads, correct me if I am wrong.