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

Gren_Yuill/CET/UNO/UNEBR at unomail.unomaha.edu Gren_Yuill/CET/UNO/UNEBR at unomail.unomaha.edu
Thu Jun 3 07:53:34 PDT 1999

```The biggest problem in predicting peaks is in the input data.  We use repeating
schedules of occupancy and equipment use, without statistical fluctuations.  We
use  weather data that may be statistically valid, but certainly won't coincide
with the occupancy schedules the way the real weather next year will coincide
with the real occupancy.

For these reasons, I have found that the deviations of predicted from measured
peak power are considerably greater than for annual or monthly energy
consumption.  I don't know a solution to the problem.

"Michael J. Witte" <mjwitte at gard.com> on 06/03/99 09:04:13 AM

Please respond to MJWitte at gard.com

To:      BLDG-SIM at gard.com

cc:      (bcc: Gren Yuill/CET/UNO/UNEBR)

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

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

======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM

======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM

```