Modelling geothermal and VRF in EnergyPlus

asked 2023-03-09 16:46:57 -0500

Fatma O's avatar

updated 2023-03-17 09:43:52 -0500


I am modeling a lowrise Multi-unit Residential Building that uses a geothermal heat pump on EnergyPlus.

The HVAC system consists of a geothermal loop connected to two condensing units (VRF) and one DHW. The condensing units are connected to FCUs in each apartment. There are also ERVs in each apartment and in the basement. So the components are geothermal GSHP, 2 VRF units, about 30 FCUs, and 16 ERVs.

The EnergyPlus GSHP measure created the following:

A ground source plant loop is connected to the condensing units (the chilled and hot water loops), which are connected to 3 coils for each of the building floors + basement.

And then, each coil is connected to thermal zones on each floor where there are FCUs. I summed the capacities of each thermal zone under the three FCUs and added the value as the total capacity of each coil.

The ERVs are connected to each of the FCUs.

All of the above does not produce any results on space heating and cooling unless I add VRF systems. (having the GSHP does not affect the heating/cooling results at all. I tried removing the whole system and keeping the VRFs and got the same result for heating and cooling)

I added the VRF (two) systems separately and added the thermal zones there too. And lastly, I added the DHW to the geothermal plant.

The results are cooling 4%, heating 3%, water systems 38%, interior equipment 43%, and interior lighting 9%.

Does this seem reasonable? Any thoughts?

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@Fatma O are the % values that you listed the energy savings after applying the GSHP measure and adding the VRF systems?

Aaron Boranian's avatar Aaron Boranian  ( 2023-03-17 09:43:23 -0500 )edit

@Aaron Boranian This is the breakdown of the total electricity consumption of the building. So the majority of consumption is coming from water systems and interior equipment (the DHW system isn't linked to the ground source pump since I don't think that's possible on OS). I am just curious about the accuracy of the GSHP measure in Open Studio, I have talked to colleagues in the energy modeling realm, and I haven't met anyone who has worked on this measure and gotten realistic results.

Fatma O's avatar Fatma O  ( 2023-03-17 10:29:14 -0500 )edit