We are working on a project which receives hot water for space heating and DHW from the city district. We know that the hot water is generated from a CHP which runs mainly on natural gas, but we would like to include a proportion of solid waste. Since, the cost of the solid waste is zero what is the best way to integrate this sustainable measure. We thought of proportionnaly reducing the natural gas energy rate for the proposed.
Any other potential solutions?
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
February 5, 2021 - 12:10 pm
It is unclear which path you're thinking about using to model the district heating source (Path 1 ASHRAE 90.1-10 Appendix G, Path 2 Full DES performance accounting, or Path 3 Streamlined DES modeling).
For Path 1, you would be modeling the district heating as purchased energy with the actual purchased energy rates charged by the city. You may be able to make a case for a different purchased energy rate in the Baseline if you can obtain some documentation from the city showing what the rate would have been without the free solid waste.
For Path 2, you would be modeling a vitual on-site district heating plant with CHP, with the actual fuels used in the city plant. In the Proposed model the solid waste would be considered free and in the Baseline model the fuel would just be natural gas.
For Path 3, you would account for the costs and efficiencies of each fuel source individually in the cost calculation, so the Proposed would include zero cost for the portion generated from solid waste, and the Baseline would just include natural gas.