We are dealing with the project served by DES. As client’s goal is to achieve Platinum we are proceeding with option 2 of modelling DES.
Our DES is served with mix fuel ( coal, biomass and oil) for which we calculated fuel mix price as 26,47 $/MWh. Our baseline system is on-site gas boiler for which fuel utility rate is 50,8$/MWh .
As DES guidance is super unclear we have a question in regard to the rates used for calculations:
should we use the same rates for baseline and proposed building equal to = 26,47 $/MWh (as calculated for the fuel mix)? Or maybe ,the same utility rates for base and proposed which are required in DES guide means that they must be consistent in both base and proposed building i.e. if DES will use gas it will be priced at rate of 50,8$/MWh - the same as baseline?
Any comments will be appreciated
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 2, 2014 - 10:42 am
Use the same rate in both models based on the rate calculated for the DES.
BH .
72 thumbs up
June 2, 2014 - 11:02 am
But thaht don't make any sense, to price gas as fuel mix. Plus it's not showing any benefits of DES over standard boiler.
I thnik that this quidance confirms thaht the rates for base and propose might be diffrent.. What do you think Marcus?
http://www.districtenergy.org/assets/pdfs/LEED/DES-User-Guide.pdf
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 2, 2014 - 11:46 am
The gas price has nothing to do with it in this case since the DES does not use gas. Appendix G does not say that the Baseline is always gas. The Baseline uses the same fuel as the Proposed in Appendix G.
See G2.4 - the energy cost is determined using the actual rate. The rates applied to each model must be identical. Section 2.4.2.2 of the DES v2 states that the rates must follow the normal Appendix G and LEED protocol.
The DES guidance is set up to account for the impact of the DES. If the system is more efficient than the Baseline you show savings, if not you show a penalty.
In general Appendix G and LEED do not allow savings related to the comparison of different fuels.
The document is certainly not an official document so it does not really matter what it says but it is technically correct. If the DES used gas you use the building rate for the gas (not the DES gas rate) in both models. Since this does not apply to your case and 2.4.2.2 Exception a does apply, you use the central plant rate.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 2, 2014 - 11:47 am
If the biomass is a qualifying renewable you can get credit for that.
BH .
72 thumbs up
June 3, 2014 - 10:42 am
Thank you for help