[Equest-users] GSHP Simulation Results

Scott Hackel shackel at ecw.org
Mon Apr 27 12:13:05 PDT 2009

Stephen -
I have seen significant savings on several GSHP models, but never quite as high as you're showing.  I'd agree with the replies you've gotten so far, especially the point about supplemental heat on the air-source system...If your building is in a northern climate then your air-source system will be running on electrical resistance most of the heating season, unless you have a cold-climate heat pump and modify the lock-out temperature accordingly...

I'd also add, on your ground-source model (especially since this is research-level work), you should check that the default performance curves in eQUEST (which you can view in the detailed interface) reflect your equipment well.  The EER and COP you mention are pretty high; as the fluid temperatures change in the model, is the heat pump efficiency reflecting levels similar to what the manufacturer had documented for the actual equipment you're trying to model?  And last but certainly not least, I would turn on an hourly report of the heat pump entering water temperature, and check it to be sure that the loop field you're modeling is giving you reasonable temperatures back at your heat pumps (and that backup heat isn't being used at all for the GSHPs - unless you're planning a hybrid system).

Best of luck to you -

Scott Hackel

Energy Engineer

Energy Center of Wisconsin
455 Science Drive, Suite 200
Madison, WI  53711
608.238.8276  x129
shackel at ecw.org

> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Stephen Parker
> *Sent:* Friday, April 24, 2009 3:03 AM
> *To:* equest-users
> *Subject:* [Equest-users] GSHP Simulation Results
> Hello everyone,
> I have modeled a ground source heat pump within the building I have
> designed and have been getting results that seem almost too good to be
> true.  I decided to compare my results with a typical high efficiency air
> side heat pump and discovered that the geothermal system is operating about
> 65-75% better than the air side heat pump in terms of cost.  The results
> from the air side heat pump appear to be correct and are reasonable for my
> design.
> Has anybody else ever gotten results for a geothermal system design that
> were much better than expected?  If so, was there something incorrect within
> your model or have you deemed it as an internal flaw of eQUEST?  This
> project is for my masters thesis, so I am trying to justify my results as
> much as possible.  For my system I am using two 3.5 ton GSHPs with an EER of
> 21.8 and a COP of 4.4, which is rather efficient.
> Thanks,
> Stephen Parker
> Bucknell University
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