Dear Sirs,
I am modeling a school building for LEED which has a Campus Energy System (water cooled chiller and diesel boiler). The DES was installed almost 8 months ago for the first phase of the project.
Now, I am modeling for the project's second phase, and additional chillers / boilers will be added to the DES in order to be able to serve both phases in addition to any potential building on campus in the future.
1) Looking at the USGBC's guidance for DES (Appendix C): in order to determine the proposed building heating / cooling efficiency, I guess I have to go with the "Modeling" option because the DES will be expanded as part of my project (so it's not existing).
For this option, do I have to create a separate model of the district plant, or shall I add this district plant to my project's model? Appendix C says "Apply measured or estimated load profiles as "process loads" to reflect the estimated total loads on the plant". If this is the case, then if I add the process loads in addition to my project's loads, I will be double counting the loads, right?
Does this mean I have to create a dummy project building (with no loads) with the proposed district plant to determine the efficiencies?
2) Does anyone have additional guidance for modeling district energy systems, other than the one of the USGBC? Something with more examples or maybe a case study with actual numbers?
Best regards,
Omar
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Omar Katanani
Omar,
For the "modeling" option you will need to model the plant with the assumed full load (which includes more than just the one building). In a separate energy mode: Run an energy model with load from all buildings on it, and then use the average efficiency (e.g. kW/ton, COP, etc) in the building model as a constant efficiency for the whole year.
For example, from the plant model you may come up with a COP = 5.1 as an annual average. Then the building model would use COP = 5.1 as a constant value.
I'll leave it up to you to determine the best way to model the full load on the DES plant, but this could be estimated with a relatively simple model. The modeling software Trace has a specific feature for this, but you can manually do this in eQuest with a little work.
Regards,
Scott
Hi Omar,
For estimating proposed buildings cooling/heating efficiencies you can
follow any of two method's mentioned below-
1. You can use default heating cooling efficiencies as per USGBC DES
modelling document.
2. You have to calculate manually heating and cooling efficiencies of
whole plant( Including Cooling tower , pumps, chillers etc.) at part
load i.e DES system capacity.
I would suggest that modelling of whole system is not required when DES
option is availed.
Thanks & Regards
Rajendra Choudhary
Sr.Energy Analyst