Hi,
I am working on a building that includes GSHP to cover part of the heating and cooling load. Normally, due to software constrains, we tend to just use excel calculators to predict the energy available from the GSHP. For this particular project, an external company spezialized in designing GSHP carried out a deep analysis and provided us (MEP team) with the heating and cooling provided by the heat pump.
Therefore, I plan to proceed as follows with the energy modelling:
1st: Model the building without GSHP in the software in order to calculate annual energy consumption (energy software -IESve- has no capability to properly model GSHP)
2nd: Use either excel calculator or results from external GSHP company to deduct cooling and heating demand/energy to the results from the energy software.
I have always worked on projects and energy models where everything can be directly modelled in the software, therefore I would like to know:
a) whether the approach previously explained is correct and meets ASRHAE 90.1 guidelines.
b) how detail the GSHP results must be (i.e what should include: provided heating/cooling, pumps, losses, etc)
b) how to properly present a BPRM report for LEED review when 2 different sources of results are used.
Thanks in advance.
Manuel
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
October 18, 2021 - 12:29 pm
I think you are making this much harder than it needs to be. Can't you just model it in software that models GSHPs? eQUEST is free and models that system.
If you try this approach make sure you account for all the interactive affects of the various systems, like lighting on heating/cooling loads, etc. In essence you will need to document in detail how combining the two models will be thermodynamically representative of the building energy performance.
Jamy Bacchus
Associate PrincipalME Engineers
25 thumbs up
October 18, 2021 - 3:23 pm
Admittedly I haven't dug into this in a couple years, so this might be dated.
The issue Manuel raises is that some modeling platforms don't do a great job of the borefield's heat exchange--dedicated software is used for sizing, annual geo-exchange and determining how the field may drift over time.
Here's info from IES-VE (circa 2019):
Ground-Source Heat Pump Modeling using ApacheHVAC and Gaia Geothermal Ground-Loop Design (GLD)
Capability for transferring hourly equipment loads and final results between the IES Virtual Environment and Gaia Geothermal’s Ground Loop Design (GLD) provides for comprehensive and detailed modeling and design of ground-source heat pump HVAC systems.
There is not yet an explicit ground-source heat pump model within ApacheHVAC; however, loads results can be read into Gaia Geothermal’s Ground-Loop Design tool. This provides detailed modeling of heat pump equipment and bore fields.
Begin by modeling the building as you would otherwise in the VE and the appropriate HVAC system in ApacheHVAC, including all controls, air-side components, coils, terminal units, hydronics, water loops, etc. and a boiler and chiller to provide the hot and cold supply water with suitable water loop flow rates and temperatures. Include any loop temperature rest (sic) schemes that will be used with the ground-source heat pump (GSHP) system. The ApacheHVAC boiler and chiller components are a placeholder that will simply record loads for the GSHP, ground-source loops and pumps, geo-exchange bore fields, backup heating and cooling equipment (boiler and cooling tower), and time-of-use (TOU) demand-based heat pump controls that can be modelled in GLD 2010.