[bldg-sim] GHP in eQuest and predicted vs. actual performance

[Liu, Xiaobing]

I'm also very glad to know  more comparison between eQUEST predicted and actual energy performance for GSHP
systems. According to a previous comparison study and my experience, the GLHE (vertical) model implemented in DOE 2.2 (and DOE 2.1 E) significantly over-predict the swing of loop temperature, which could in turn result in the under-prediction of the savings from GSHP systems.
 
In addition, the ground thermal properties and undisturbed ground temperature (which could be a few degrees higher than the soil temperature because of the vertical ground thermal heat flux) play an important role in the GSHP performance. The errors in these parameters may also be responsible for the under-prediction.
 
Another thing needs to be mentioned is that current eQUEST doesn't account for the effect of grouting, which could change the loop temperature significantly.
 
Last but not the least, the eQUEST default COP and EER of the GSHP are far below those of the currently available GSHP units. Higher COP and EER will make a big difference in the predicted energy savings.
 
This is my experience of using eQUEST for GSHP simulation. Hope it helps. I am looking forward to other peoples opinion and experience.
 
Have a nice week,
 
Xiaobing

________________________________

From: bldg-sim at gard.com on behalf of Renee J. Azerbegi
Sent: Sun 10/2/2005 11:43 AM
To: bldg-sim at gard.com
Subject: [bldg-sim] GHP in eQuest and predicted vs. actual performance



Yes, you can model ground source heat pump systems (GSHP). How accurate the
results are I'm not sure. You have to create a Loop in water side and then
add a Ground Loop Heat Exchanger. Check the min and max alarm temperatures
since sometimes these need to be adjusted.

I did model a small 10,000 sf building a few years ago in eQuest with GSHP
and compared it to actual data. Predicted was 43 kBtu/sf/yr and actual was
25 kBtu/sf/yr (a 99 Energy Star rating!) My life cycle cost results showed
the indirect/direct evaporative cooling was better than GSHP (since the
building was in a dry climate of Colorado), however the owner wanted to go
with the GSHP system. The owner is very energy conscious so they do turn off
equipment at around 3 PM for this school maintenance building which might be
part of the low energy usage, however, I wonder if eQuest under-predicts the
savings from GSHP systems?

GSHPs are all the rage, but I don't think they are cost-effective if you
have natural gas for heating as your base case. But then again, with the
rising cost of natural gas, maybe they will be more affordable. Anyone else
have any experience with predicted versus actual energy performance for GSHP
systems?

Renee

-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Leela Kala
Sent: Friday, September 30, 2005 9:17 AM
To: bldg-sim at gard.com
Subject: [bldg-sim] GHP in eQuest

Hi,
Can I model GHP in eQuest? If yes, I will appreaciate
if someone can send me teh details.

thanks

Leela


               
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