What's the COP/EER of Ideal Loads Air System

asked 2022-10-12 06:39:37 -0600

Liza Lee
85 ●5

updated 2022-10-12 09:19:26 -0600

14155 ●83 ●24 http://bigladdersoftware.com/

Hi, So I used "ZoneHVAC:IdealLoadsAirSystem" in one simulation case. I have the cooling and heating energy consumption. Just wondering, what's the COP/EER of this ideal air conditioning system? Thank you very much！

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Same question as this.

shorowit ( 2022-10-12 12:10:43 -0600 )edit

Thank you. But... " This component can be thought of as an ideal unit that mixes air at the zone exhaust condition (or plenum outlet condition when a plenum is attached) with the specified amount of outdoor air and then adds or removes heat and moisture at 100% efficiency in order to produce a supply air stream at the specified conditions." This sentence is not saying that COP is 1. It's talking about the efficiency caused by specific components, the ideal system doesn't have specific parts, so efficiency is 100%

Liza Lee ( 2022-10-13 00:36:41 -0600 )edit

If COP of the ideal loads air system is really 1, it's unreasonable. In fact, air conditioning system's COP/EER is always bigger than 1. In reality, air conditioning system's COP/EER is among 3 to 6.

Liza Lee ( 2022-10-13 00:40:15 -0600 )edit

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answered 2022-10-13 10:23:51 -0600

shorowit

11891 ●201 ●9 https://www.nrel.gov/b...

updated 2022-10-13 10:25:10 -0600

An ideal air system is not mean to be a realistic piece of equipment. It's often used to calculate the building's heating and cooling loads or is used when the HVAC equipment is not known. It has a constant year-round COP of 1, though I believe you can specify a heating or cooling efficiency for it using the EnvironmentalImpactFactors object -- see the District Heating Efficiency and District Cooling COP fields.

If you want to model an air conditioning system, you can add a DX coil object to your model. Unlike an ideal air system, air conditioners and heat pumps will have COPs that vary throughout the year based on (primarily) outdoor temperature.

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Thank you very much. This is really, wow, an air conditioning system with COP of 1, in my opinion, i will consider the energy consumption of this simulation as wrong. It's too far away from reality. Thank you for your suggestions, i will try to make a new air conditioning system.

Liza Lee ( 2022-10-13 10:40:01 -0600 )edit

Here's a relevant feature request to add efficiency fields to the District* objects. https://github.com/NREL/EnergyPlus/is...

MatthewSteen ( 2022-10-14 11:34:15 -0600 )edit

Hi Liza, it is unrealistic, yes, but keep in mind, that a use case of using COP=1 is to easily postprocess your simulation result in e.g. Excel at early stages of the design.

furtonb ( 2022-10-14 13:23:48 -0600 )edit

Sure, Thanks. I think it would be better if it's clearly explained in the documents.

Liza Lee ( 2022-10-14 13:33:21 -0600 )edit

@Liza Lee it's mentioned here. https://bigladdersoftware.com/epx/doc...

This component can be thought of as an ideal unit that mixes air at the zone exhaust condition (or plenum outlet condition when a plenum is attached) with the specified amount of outdoor air and then adds or removes heat and moisture at 100% efficiency in order to produce a supply air stream at the specified conditions.

MatthewSteen ( 2022-10-14 13:41:11 -0600 )edit

I have seen this sentence. I don't think it's saying COP is 1. I think it's talking about something like mechanical efficiency is 100%. COP is clearly something different, and it's almost never in the form of percentage.

Liza Lee ( 2022-10-14 13:50:37 -0600 )edit

@Liza Lee it is saying that by generalizing the efficiency of heating and cooling systems. A COP of 3.0 is basically an efficiency of 300% because of the "free" energy available to the system. If you want to estimate the cooling energy of a refrigerant-based system, you could simply post process the results by dividing the cooling energy by your COP, which I think is what @furtonb said.

MatthewSteen ( 2022-10-14 14:03:08 -0600 )edit

Yes, it's a way to make it more realistic. It's what I did, for now. Thank you!

Liza Lee ( 2022-10-14 14:18:37 -0600 )edit

@MatthewSteen Yes, that's what I was thinking about, it wasn't clear.

furtonb ( 2022-10-14 15:19:32 -0600 )edit

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