I have a CHP project that I cannot seem to fit in any one clearly defined compliance path. I have not found a previous LEEDUser discussion that seems to answer my questions.
Our project is a new Campus Utility Plant Building. The building shell is seeking LEED - NC Certification. It is not our intent to certify the Process systems—Boiler Plant, CHP and Electrical Distribution. Our general approach to demonstrate compliance with and percentage energy cost improvement for EAc1, Option 1. Whole Building Energy Simulation is based on an eQuest v3-64 model. As this building obtains all of its electric and thermal energy from AND HOUSES a Combined Heat and Power (CHP) plant for the Campus Thermal Energy system our modeling procedure was guided by the USGBC’s “Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 – Design & Construction”, August 13, 2010, and follows the “Performance Path 2 (full accounting)” defined in Appendix D.
It seems clear that the EAp2 &EAc1 Base Case model is constructed per Appendix G. The treatment of the proposed building is not clear to me.
Two questions related to my uncertainty on how to draw the “control volume” for energy flow for our building.
1. How do we allocate CHP electricity to our building? Even though the building obtains all electricity from the CHP, according to Appendix D Page 25, it appears we can only apply the portion of the electricity generated by the CHP that coincides with the thermal heat recovery used in the building. (Track Thermal in eQuest) and the cost of the electricity is the fuel cost for CHP generation of those kWh. When we calculate the “allocated CHP electricity “it is less than the electricity required by our building therefor “Scenario A” (page 26). Since in our case, all electricity for the building is CHP generated, the remainder of the electric energy not corresponding to thermal load in the building we also use the cost of fuel for CHP generating the rest of the electricity? If this is our path is there a need to make the distinction?
2. Since it is not our intent to certify the plant, do I include equipment located in the building that does not serve the building? There are 3 LPS boilers (1500 BHP total) and 1 HPS boiler (45s BHP ) that are in the new building to provide heating and process steam to the campus distribution system year round. Can we omit this energy since it is not used in the building? If we do include this energy then we get into the plant efficiency, in essence including the DES system in the certification and that is not our intent.
My 3rd question is to clarify contradictions between the LEED 2009 Reference Guide and the “Treatment of District…” since this document at its publishing was not mandatory.
3. Per “LEED Reference Guide 2009” pg. 268, there is a requirement for EAp2 that the proposed building have a 10% energy cost improvement without the CHP, implying the need for a separate model (parametric run). However, per page 9 of “Treatment of District…” “each project team chooses...” an option “...to show compliance for both EAp2 and EAc1 in a single unified step… under this updated (version 2) DES guidance document, no project team is required to assess both options, nor to model separately for EAp2 and EAc1. This is a substantial difference from version 1 of this guidance intended to simplify the guidance and improve its flexibility” Do I need demonstrate EAp2 compliance?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 14, 2011 - 7:22 pm
Obviously LEED was never intended to certifiy a project like this.
I don't think you can exclude the energy consuming equipment in the building. All energy within and associated with the LEED project must be included. Think of it like a manufacturing plant. Since the building uses thermal and electric energy generated within the building you can't really treat the equipment like a process load exclusively however. Perhaps you will need to treat it as both as a source and the majority as process.
You will need to comply with EAp2.
The complexities of your issues, as you probably know, require considerable research and thinking - more than a volunteer like me has time for.
Anyone done a project like this?
Christopher Schaffner
CEO & FounderThe Green Engineer
LEEDuser Expert
963 thumbs up
October 26, 2011 - 1:57 pm
I'm working on a project EXACTLY like this. Well, pretty similar. A few thoughts:
1) Re your question #3 - use the latest DES guidance, rather than the 2009 reference guide. You can show prerequisite compliance with either Option 1 or Option 2.
2) model your building as though it was supplied by the DES, but the DES was outside the building. This is actually covered in the definition of "downstream equipment" in the DES guidance (p7).
"Exception: When the building housing the thermal energy plant is itself seeking LEED certification, then the project shall treat the DES equipment as “downstream equipment” for the following prerequisites and credits:
• EA prerequisite 1
• EA prerequisite 2
o Mandatory Measures: The district energy equipment shall comply with all mandatory measures from ASHRAE 90.1-2004.
o Prescriptive Method: The district energy equipment shall comply with any applicable prescriptive requirements
o Performance Method: The district energy equipment shall be modeled as upstream equipment, NOT downstream equipment. USGBC recommends that such projects use modeling Option 2 (described below).
• EA prerequisite 3
• EA credit 3
• EA credit 4
• EA credit 5"
Eric Shamp
Associate Vice PresidentCannonDesign
68 thumbs up
December 9, 2011 - 4:44 pm
I am also working on exactly this building type: Central Plant with CW, HW, and electric distribution. No CHP. I know there have been discussions elsewhere on this forum re: process loads, but our problem seems unique to the building type... must we treat secondary plant equipment for heat rejection (ventilation fans, air conditioning for electric rooms) as a downstream building process load, or can those loads somehow be modeled as virtual downstream loads distributed amongst all connected buildings? The heat rejection process loads account for 60% of the total load in the Central Plant, which negates all energy efficiency measures implemented on the remainder of the building. We are struggling to meet EAp2.
Melissa Crowe
Sr Energy EngineerCMTA Inc
1 thumbs up
March 27, 2012 - 2:10 pm
I really appreciate your responses but still have a question that I think you might be able to address especially if you have worked on the EXACT situation.
Ok so I model DES equipment as “upstream equipment”, the question is: How do we allocate CHP electricity to our building? Note that for our building:
The CHP runs fully loaded 8760 and that 100% of the waste heat is used on the campus.
The CHP output always exceeds the building heating and electric requirements.
All of the energy used in the proposed building is generated by the CHP.
I know that, per the DES guide Appendix D (pg. 25-26), when the building is using heat from the CHP:
o Electricity generated by the CHP that coincides with the thermal heat recovery used in the proposed building is allocated to the building.
o CHP fuel usage that corresponds to the heat used is charged to the building.
o Excess CHP electricity allocated to the building is considered “process energy” (page 26, Scenario-B) and the input fuel associated with this excess CHP electricity is accounted for in the base-line case.
How do I model the times when no heat is required in the building (most of the year) since all electric comes from the CHP? The conclusion from reference sited above is to use the baseline electric utility rate.
Is there a rational for modeling the building as getting ALL of its electricity from the CHP even when no heating is required in the building? It would seem reasonable to model this situation using CHP power and that the fuel used to produce CHP electricity that serves the proposed building is charged to the building. I don’t think the guide addresses this situation.
Thank you
Melissa