[BLDG-SIM] Statistical Estimate of Number of Units ON (peak

Michael J. Witte mjwitte at gard.com
Thu Jun 3 07:04:13 PDT 1999

On  2 Jun 99 at 18:51, BKoran at aol.com wrote:

> If I have a large number of units, the number of units likely to be
> operating simultaneously will approach the product of the total number of
> units times the fraction of time each unit is on.
> I suppose I need to use a threshold probability to constrain the problem. 
> So, with a probability greater than 70%, what is the maximum number of
> units operating simultaneously?  Even better, what is the maximum average
> number of units operating simultaneously over a 15-minute period?
> How do DOE-2, Trace, HAP, BLAST, etc. calculate a 15-minute peak demand?

DOE-2.1E and BLAST do not do anything special to calculate subhourly
demand windows.  The electric consumption for the hour is averaged
over the hour.  As you said, this is a good approximation for larger
facilities with more than a few units, but it could underestimate
demand charges for facilities with a few units or in applications
where return from setback would cause all units to kick on at the
same time and run for say 30 minutes to cool down the facility. 
Does anyone out there know whether Trace or HAP or DOE-2.2 have any 
subhourly demand tracking capabilities?  

Mike Witte

Michael J. Witte                        mjwitte at gard.com
GARD Analytics, Inc.                        www.gard.com
1028 Busse Highway                    Phone 847-698-5685
Park Ridge, Illinois 60068-1802         FAX 847-698-5600
USA          Energy, Environmental and Economic Research

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