I am working on a project that is using heat pump chillers to generate hot and cold water for the building systems. When the building loads are cooling dominated, the excess heat is rejected to the atmosphere by closed circuit coolers. When the building loads are heating dominated, the excess chilled water generated by the heat pump chillers is rejected to a campus chilled water system. My question is if I can take credit for the excess chilled water generated by the heat pump chillers. This isn't a direct benefit to the building itself but it will certainly reduce the energy consumed by the campus chilled water system. If I were taking chilled water from the campus chilled water system I would certainly need to account for that, so it would seem reasonable to me that you should be able to take credit for this.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
February 14, 2024 - 5:01 pm
Sure you should be able to do so. Is your project connected to the campus chilled water system?
Michael Hill
2 thumbs up
February 14, 2024 - 5:12 pm
Yes, it is connected to the campus chilled water system but only for the purposes for rejecting excess chilled water to the campus chilled water loop. This occurs when the building's heating demand requires us to generate chilled water in excess of what the building requires in order to satisfy the heating demand. In this scenario, we are effectively taking heat from the campus chilled water system in order to heat the building. All the chilled water used by the building is generated by the building's heat pump chillers.
Jamy Bacchus
Associate PrincipalME Engineers
20 thumbs up
February 14, 2024 - 5:53 pm
I had some similar questions recently with GBCI regrading credits for district systems with sewer heat recovery. In your case it sounds as if you're pulling heat from the chilled water loop vs a sewer. So perhaps the same ECM calcs could be done to show you're getting "free heat" and the baseline has no heat receovery. Where I stop in my tracks is Low Delta T. You'd need to make certain your heat draw isn't adversely affecting the upstream chillers' performance with a low delta T on return. If it were a drag on the system, then the ECM would need to deal with that.
Cory Duggin
Senior Energy WizardTLC Engineering Solutions
51 thumbs up
February 15, 2024 - 10:43 am
We have modeled and submitted a similar situation before with water-cooled VRF that uses campus CHW as the condenser water. We run two simulations. One to get the heat rejection load profile from the VRF. Then we place it as a scheduled load on the campus chiller loop in the model to capture the additional load we are adding. We were modeling the DES as purchased cost neutral, so then we did the virtual rate calculation and broke it out as district CHW in the MEPC. If the software you are using doesn't allow for a scheduled load on the CHW loop, you could just post process it in excel. The main comment we got from the GBCI reviewer was to break the DES cooling out in the MEPC from the compressor power cooling energy of the VRF.
Michael Hill
2 thumbs up
February 15, 2024 - 11:47 am
Jamy Baccus That's a very good point about the Low Delta T. I will have to discuss with the Lead Mechanical Engineer exactly how they plan to set up this system and I can determine if this will actually result in reduced performance of the plant chilled water system.
Farooq Saeed
HVAC DESIGN ENGINEERCDC | Consulting and Design Consortium (Pvt) Ltd
17 thumbs up
March 26, 2024 - 4:29 am
Hi
can somone guide me how to perrform "Exceptional Loda Calculation" and post process in excell? i need to perform these for a process load of manufacturing unit.