LEEDv4 CHP Calculation

asked 2020-07-12 12:08:46 -0500

LEEDv4 project on a university campus, climate 2A; initially told it was a DES only. Project is receiving all chilled water and steam from DES (no on-site boiler/chiller). Had initially modeled under Path 1 - Option 2 - full DES; CHW COP=~5ish & boiler=55% (with losses accounted for). This method used a chiller & boiler with a 'flat' curve at those efficiencies. Project savings were 26% / 11 points.

Have learned learned project is actually CHP, not DES. Have review the LEEDv4 guidance and information from EPA (https://www.epa.gov/chp/treatment-chp...) and have a few questions after re-re-reviewing and recalculating; mostly because I dont believe the savings increase. It's a 'simple' CHP/DES in that all 'waste' heat goes to the Steam Loop (X_heat = 1; per the university).

1- to get the thermal energy fraction of the total DES to the building (BLDG_heat), the Proposed needs to be modeled with meters / get the load from the chilled/hot loops, yes? (Step 1)b) i) in calculations) [my Proposed uses less than its allocation, but ignoring that penalty to the Baseline for now]. This deviates from the Path 1 - Option 2 & is more like a Path 1 Option 1 model? Or, what is best way to demonstrate the 5% pre-req while staying thru to the method Path 1 - Option 2?

2-Since the Proposed electrical consumption is less than my allocation of electricity from the CHP. No added electricity needs to be purchased. The Proposed model's total costs are the allocation of fuel used at the CHP...(?) This leads to my savings becoming 54% / 18 points. - still without the allocation penalty to the Baseline.

I understand the process in that a CHP can make multiple 'uses' of a BTU, first as electricity then as 'waste' steam heat and that the electricity can be used to make chilled water. This is basically making chilled water at the cost of gas vs the cost of utility electricity. But this still leaves me cautious/disbelief. The LEEDv4 MEPC file did not appear to offer much additional guidance & not sure the CHP checkbox vba is working as intended. Not sure how GBCI will take to the review either. Any one have similar experience or guidance they can offer is greatly appreciated.

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