I wonder how close can HVAC system get to the result I get from running my model with Ideal Load Air System as far as energy consumption and unmet hours? Maybe I can get lower as far as energy consumption is consider?
The key thing to point out for the Ideal Load Air System is that it provides heating and cooling at perfect efficiency, which real HVAC systems cannot do. As such, energy consumption will always be less for the Ideal Load Air System compared to a real HVAC system maintaining the same conditioned air states -- unless you model an HVAC system that breaks some laws of physics and thermodynamics!!!
Both cases should have similar unmet hours as long as key system parameters -- capacity, supply air conditions, availability, etc. -- are the same between them.
Primarily, the Ideal Load Air System is used as a load calculation tool -- get everything else except HVAC set up in the model, then see what kind of heating and cooling loads each zone requires in order to design the real HVAC system.
I think some confusion that comes from this is that there are 'energy' outputs from an ideal air loads system. In my opinion, EnergyPlus shouldn't provide these as outputs because they should be loads. I know it's all academic, especially because they end up having the same units, but thinking about the energy use of an ideal air loads system doesn't have any physical meaning in the real world.
@bbrannon4 you make a good point about the 'energy' outputs from an ideal air loads system. Currently, EnergyPlus lumps the energy consumption of ideal air loads systems into the District Heating and District Cooling categories, which can be misleading. Maybe there should be a new "Ideal Loads" category that appears in energy use tables to clear things up -- an issue request on Github could potentially make that happen. Thoughts?
Good idea @Aaron Boranian, done: https://github.com/NREL/EnergyPlus/is...
Comments