[Bldg-sim] District Heat

Keohane, Michael Michael.Keohane at pmg.ie
Wed May 6 13:03:10 PDT 2009


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
Energy Engineer
Project Management Group



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