district CHP system

Giorgia Lorenzi

Engineer LEED AP

Strategie d'Impresa

LEEDuser Basic Member

0 thumbs up

July 5, 2012

I am modeling a building which is connected to a district CHP system. I’m using LEED 2009 NC Italia, which refers to “CHP Calculation Methodology for LEED-NC v2.2 EA Credit 1” http://www.usgbc.org/ShowFile.aspx?DocumentID=1354 where it is written “The Baseline Building heating and cooling plant utilizes the backup energy source(s) of the Design, or electricity if no backup source is present”. I'm modeling a project with no backup source (heating is due only to the district heating and to solar collectors and no cooling system is present). For the heating system shall I model electrical resistances? To calculate the primary energy shall I use the conversion factor relative to electric energy (according to Italian standards 2,17)? And for the cooling system can I choose any system which uses electrical energy as input and the limit value of ASHRAE 90.1 as efficiency?

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Joseph Lewis

Senior Energy Modeler

Fortier Engineering

LEEDuser Basic Member

2 thumbs up

Thu, 07/12/2012 - 18:57

I would suggest you get permission from your local USGBC to use the updated version of your document. http://www.usgbc.org/ShowFile.aspx?DocumentID=7671 The rules in this document are much more clear and it offers a streamlined calculation process if you are not seeking a lot of points on this credit. Additionally, it gives specific assumptions as to what rates to use use if you have just a district system or if you have a complete CHP system. ASHRAE 90.1 2007 Appendix G tables G3.1.1A & B would be the tables you should use to determine what system is needed since the building has no cooling system. You would select from the "Electric and Other" column. It is also important to note that according to ASHRAE 90.1 2007 Table G3.1#1 (b) if a space is considered "conditioned" by definition listed in that document then you must model the proposed and baseline systems with the same type of cooling system compliant with the Appendix G rules. Based on the way it is worded my interpreatation has been on several projects to pick a very high cooling thermostat setpoint so the system rarely runs with a load.