[BLDG-SIM] Stat Est response to John P. Karasaki
BKoran at aol.com
BKoran at aol.com
Thu Jun 3 16:47:24 PDT 1999
In a message dated 6/3/99 8:40:35 AM Pacific Daylight Time,
jpkarasa at cbg-engrs.com writes:
> I don't think you can estimate AC equipment demand with the statistics
> variables you mention. The number of AC units on at any time is a function
> of the internal and external building loads, the thermal inertia of the
> building and contents, and the equipment operating schedule set by the
> building operator.
And, I believe, statistical variability in things such as the duty cycle of
the equipment, which is dependent upon equipment variability, T-stat
> We had a project in which we had the good fortune of over 2 years of
> data and coincident weather data. The goal was to come up with a series (a
> minimal amount!) of equations by which we could predict a building's
> load based on outdoor air parameters.
> We were not able to do it as there were too many inconsistencies and too
> many variables. e.g. so what if it is 100 F out if that occurs on a Sunday
> when the building isn't occupied; or worse, a Monday that also just happens
> to be a holiday.
I had a retrofit project in which I also had "2 years of chiller data and
coincident weather data" This was a large hospital, and I WAS able to come
up with a series of equations to model the cooling load based on outdoor air
parameters. My spreadsheet model was evaluated by the P.E. for the local
utility, and we obtained a $180,000 rebate based solely on my model.
So now we have 2 anecdotes. Neither of us is right or wrong in the
reasonabless of simulating a facility based mostly on OSAT. I happened to
have a particularly consistent building. I'm guessing you didn't. Also,
the building I was looking was relatively unaffected by day-of-the-week,
> It seems the more one tries to simplify a complex process, the more the
> accuracy of the results are compromised.
I couldn't agree more. But my concern is that our *best* sim programs
already include big simplifications in this regard.
Thanks for responding to my post...this is most educational, and making me
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