Dear Everyone,
Many of our buildings are connected to DES system with CHP. To calculate CHP influence we use "Treatment of District Energy CHP Outputs in LEED® for Building Design and Construction: New Construction and Major Renovations" it describes clearly Option 2 Patch 2 Full DES performance accounting in which we model Baseline and Proposed using remote hot water and then costs are recalculated based on described equations.
Hovewer when we look into LEED v4 Reference Guide this methodology is more like Patch 3 Streamlined DES Modeling which makes me confuse which methodology we actually use and what we need to input in MEPC.
Many thanks for any help
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
June 26, 2019 - 2:53 pm
For v4 project you must use the DES in the LEED Reference Guide. The old DES document only applies to v2009 projects.
Przemysław Rejczak
Energy Modeling SpecialistJW+A
11 thumbs up
June 27, 2019 - 2:14 am
OK clear, but this doumment ""Treatment of District Energy CHP Outputs in LEED® for Building Design and Construction: New Construction and Major Renovations" references LEED v4.
Przemysław Rejczak
Energy Modeling SpecialistJW+A
11 thumbs up
June 27, 2019 - 11:05 am
At first: "Treatment of District Energy CHP Outputs in LEED® for Building Design and Construction: New Construction and Major Renovations" documment refers to LEED v4 and it should be compatible with Patch 2.
I want to clarify some issues about this patch and the documment used.
At first it shows methodology of recalculation Proposed and Baseline costs when utilizing CHP in municipal DES system which building use. Usually Baseline costs stays the same and Proposed recalculated costs is a sum of additional electricity + additional thermal energy + CHP fuel costs.
The questions are:
1. Documment states to make nessesary calculation we need to prepare energy model.
For the Baseline "The onsite heating plant must meet requirements outlined in ASHRAE 90.1-2010, Appendix G", so should it be modelled as fossil fuel? If yes I assume that it should be coal that CHP uses with its price. ( it is very low comparing to RHW cost). Right?
2. There is no strict information about modeling Proposed "Using an energy model, determine the electricity and thermal energy loads of the Design Building". However LEED v4 Reference Guide states that proposed must use virtual plant with default or calculated efficiencies of heat production distribution losses etc.
I am not sure if this documment is kind of separate methodology which requires just energy model created using ASHRAE 90.1 -2010 using remote hot water energy in both Proposed and Baseline and it gives a method of recalculation savings which is compatible with Patch 2, or it is additional methodology to patch 2 described in LEED v4 Reference guide which shows how to recalculate calculate savings after creating Proposed and Baseline in the way described in LEEDv4 Reference guide - Fossil Fuel Baseline + Virtual Plant Proposed.
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
June 28, 2019 - 12:55 pm
1. Yes, the Baseline onsite heating plant should use the same fossil fuel as the DES heating plant. If there is a mixture of fuels in the DES, then an identical mixture would be used in the Baseline heating plant.
2. The document you are referencing appears to be published by the US EPA CHP Partnership as a guidance for modeling DES systems with CHP according to the LEED v4 Reference Guide using Option 1, Path 2: Full DES Performance Accounting. It is not a separate methodology.
Przemysław Rejczak
Energy Modeling SpecialistJW+A
11 thumbs up
July 1, 2019 - 1:03 pm
Thanks for help,
Two additional questions,
1. Patch 2 states that for Proposed building Virtual Plant must be created. When I use US EPA CHP Partnership guidance my recalculated Proposed results consist of fuel and electricity. DES provides 100% of thermal load ( transfered to hot water, I does not include VRF) so I don`t need any additional Proposed boiler energy use. It means for me that I don`t need to care about virtual boiler efficiency right? I understand that this Virtual Plant should be created for this additional boiler energy use only to postprocess results, not for calculation Proposed Building Thermal Load which may be calculated according to Appendix G using 100% efficient plant.
2. Reference Guide for LEED v4 mentions about inclusion of upstream pumping energy and district system thermal loss. US EPA CHP Partnership guidance does not mention about inclusion of those parameters in Proposed. I assume that heat loss is included in parameter BLDG_HEAT which is a fraction of heat supplied to building/total heat supplied to DES. Is that right? What about Pumping Energy?
Option 1 - I assume that this energy is also included somewere in calculation ( I provide net produced energy of DES)
Option 2 - I should estimate upstream pumping energy and include it in Proposed using as Total Pumping Energy*( Building Heat/ Total Heat).
Many Thanks in advance
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
September 12, 2019 - 7:50 pm
1. The DES virtual plant needs to account for the actual efficiency at the central plant. You can either model the central plant efficiency directly or model it as 100% and account for the actual efficiency in post-processing. Either way the efficiency needs to be included.
2. Heat loss is not included in the BLDG_HEAT parameter. It gets factored into the efficiency as Plant Efficiency (%) x [100% - distribution loss (%)]. The pumping energy is prorated to the building based on the ratio of the annual thermal load of the building to the total DES thermal load.