Is it possible to model a hybrid heat pump system in eQuest, possibly by adjusting CAP and EIR curves?

asked 2015-09-17 10:03:24 -0600

Mel
425 ●3 ●10

updated 2015-11-09 13:26:29 -0600

Is it possible to model a hybrid heat pump system in eQuest, possibly by adjusting the CAP and EIR curves? The proposed hybrid heat pump system is set up with one WSHP loop with boilers and cooling tower, where each heat pump uses the standard refrigeration cycle for cooling but uses only a water coil for heating without a refrigeration cycle for heating (with the loop temperature reset based on outdoor air temp). eQuest appears to eliminate the heating choice when selecting heat pump. As a work-around I tried using a packaged single zone, but it will only allow a 2-pipe, HW, or Domestic water coil for heating, and on the cooling side only allows a CW or WSHP loop for water cooled condenser. I seem not to be able to put the both the heating and cooling of the hybrid heat pump on the same loop to achieve the energy "sharing". So another thought I had was to play around with the heating CAP and EIR curves to model the heating as typical water coils. Any suggestions on how best to model the hybrid heat pump system?

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answered 2015-11-09 11:39:05 -0600

Daniel
648 ●3 ●10 http://www.sustainabil...

It's a good thought. I would be tempted to try setting the EIR curve to a flat part-load curve, and leaving the capacity (as a function of temperature) as is. It's not clear to me how to handle the EIR (or COP). Presumably this would tend towards zero as there would be no compressor energy to speak of. I think the major challenge in this kind of work-around would be handling the loop water temperatures, as they would presumably need to be higher than usual to allow hot water coils to add sufficient heat to the supply air without a heat pump. I recommend setting up a model with a 4-pipe system and a separate model with a WSHP system with whatever workaround you are interested in trying. You should be able to determine the heating and cooling energy required from the HW and CHW loops on an hourly basis, and compare this to what happens in the WSHP loop to see if the results are making sense. If you spend enough time with the hourly reports you should be able to test out a few ideas and determine whether your workaround is giving realistic results.