A building pursuing LEED 2009 NC certification will be located in a campus with a District Energy System (DES) that incorporates a CHP, absorption chillers, electric chillers and boilers. This DES will supply 100% of the building’s thermal needs (hot and chilled water). Under this context:
1) What methodology shall be adopted to calculate Proposed Design building energy costs under EAc2 when following option 2 – Full accounting (aggregate building / DES scenario). As this DES includes CHP as well as boilers and electric compression chillers, our proposal is (using as reference document ”Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009 – Design&Construction”):
a. To use appendix D for CHP modelling
b. To use the general methodology for DES modelling for calculating chilled and hot water energy rates;
2) Does electric energy use of CHP ancillary equipment (e.g.: pumps) need to be accounted? How shall it be included in the energy costs calculations? Please note that there isn’t any reference to this energy use in appendix D (using as reference document ”Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009 – Design&Construction”)
3) When calculating Xheat (the fraction of CHP plant total thermal energy supplied to the DES) shall the Proposed Building energy use included in the calculations (historic data from meters does includes the new building…)?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
May 24, 2017 - 3:07 pm
1. EAc2 is for renewable energy which does not seem to apply. I'll assume you mean EAp2/EAc1. Appendix D does not include any guidance on the rates so use the DES rate methodology (Section 2.4.2.2).
2. They would be treated like the other DES pumps. They enter into the methodologies used to determine the overall efficiency. See DESv2 Appendix C.
3. Xheat is usually 1 because all of the waste heat gets applied or supplied to the district system. It would possibly be less than 1 if some of the waste heat was used for other purposes. The energy use of the proposed buildings would not factor into the determination of Xheat unless the building would use some or all of this waste heat directly within a building system(s).
Additional guidance on modeling CHP scenarios is contained in the LEED v2009 BD+C Reference Guide under EAc1.
Ricardo Sá
Director of SustainabilityEdifícios Saudáveis Consultores (503 910 767)
84 thumbs up
May 26, 2017 - 10:31 am
In what regards Xheat calculation, does the amount of useful waste heat rejected in the flue gas (i.e. heat that could otherwise be used for generating hot water for heating purposes) be accounted for? In other words, does the real annual CHP thermal efficiency affect the calculation of Xheat?
Thanks,
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
May 26, 2017 - 11:22 am
The Xheat is only the recovered waste heat. The heat lost by the system is a factor in the determination of the efficiency of the system.