Hi Paul,
It is my understanding that LEED definitely wants you to use the actual fuel (coal) and rate for both the proposed case and the baseline case for the Step 2 model.
I don't know what you should use for efficiency in the baseline case, though. You are right that table 6.8.1 does not have efficiencies listed for coal. Are there any local codes or other mechanical codes that list a minimum efficiency for a coal boiler? Otherwise I would send in a CIR. I searched through the existing ones quickly and did not see any questions on coal fuel. It seems strange though, someone must have modeled a coal fueled building.
Good luck. The district ones are tough. I just finished one and am dreading the LEED review comments!
Allison Gaiko, PE, LEED AP
Hi all
I have a question in relation to the modeling of district cooling
systems which someone might be able to advise me on.
I have a campus where 4 air cooled chillers are providing cooling to a
number of buildings including my own.
There is no monitored data available for these chillers and no district
cooling utility costs as they are owned by the building users.
The LEED document on DES indicates that if the data required is not
available then a default value of COP of 4.4 can be used to calculate
the annual the energy cost including losses, pumps and maintenance etc.
This figure is based on a water cooled chiller and cooling tower
combination.
It does not make much sense to use this value as the air cooled system
is likely to be significant worse in terms of efficiency then this?
Would the correct approach in this situation be to model the 4 air
cooled chillers as a virtual plant using the either manufacturer curves,
or else the minimum efficiencies of aircooled chillers as per 90.1 and
implement the modeling rules as per Appendix G.
I would appreciate any help in regards to this matter
Thanks
Michael F. Keohane