There were a couple of previous posts on this subject, one from an industrial process and one from a data center that were located outside the LEED project boundary. When using waste heat from a source within the project boundary this is simple and straight forward, since the source of the waste heat would be included as an energy use within the model. When the source of waste heat is off-site the issue is more complicated since the source of energy use that generates the waste heat is not captured within the energy model.
Waste heat generated from a source that uses energy to then generate that waste heat is not free. There is a cost associated with the generation of that waste heat. For off-site waste heat sources a cost must be assigned to this heat source according to GBCI guidance. However, GBCI did not provide any definitive guidance on how to determine this cost. This cost must be proposed by the project team and submitted for review. It will be subject to the discretion of the individual reviewer. Similarly it is up to the project team to suggest an appropriate baseline energy source cost.
Our initial thoughts, if we were faced with submitted this for review, would be to propose the following for the Proposed fuel cost associated with the waste heat - the cost of the fuel source used in the process times the fraction of the energy use that generates the waste heat. For example, suppose you have a process boiler that is 80% efficient and you install a stack economizer that recovers an additional 10% of the heat in the fuel with the remaining 10% going up an out the stack. You would take the original fuel cost times 10% and apply that to the waste heat fuel cost in the proposed case.
For the baseline fuel cost you could use the full cost of the fuel used in the process or the cost of the fuel source of the heating system you would have used absent the availability of the waste heat recovery. We would use the fuel cost that is the lowest between these two to make sure we were taking a conservative approach.
Anyone else have any thoughts on this issue?
