Ice Storage - Chiller efficiency, etc.

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I have two air-cooled chillers that I'm using to charge an ice thermal
storage system at night. I have entered the EIR that equest calculated
with the EER based on the chillers' normal operating conditions (44
degree CHWST). Now, the model with ice storage is using about 46% less
energy for space cooling, which is way too low. They should be pretty
close to the same..

Does anybody have experience with this? I'm thinking that equest isn't
derating my chillers while they're making ice (should be ~35% decrease
in efficiency). I will probably have to get the chiller efficiencies at
ice-making conditions and add 2 more chillers into equest at these
conditions to charge my ice storage, and just allow the other chillers
to run during the day. Can anybody confirm this or provide any other
tips?

Thanks,

Greg Collins

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Greg,

Your best bet is to contact the (or any) manufacturer and have them tell you the chiller efficiency at the given operating conditions. I've never tried to model a thermal storage scenario before, but I have tried to optimize a heating hot water temperature to try to take advantage of a condensing boiler, and just changing the loop temperature is not enough for eQuest to catch on. You have to manually change the efficiencies for each piece of equipment in order to accurately model this. I know it's not exactly what you had asked for, but I hope it helps. Thanks.

Daniel I. Deese, EI

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