[Bldg-sim] Energy model calibration - normalizing the utility bills to month start-end

Maria Karpman maria.karpman at karpmanconsulting.net
Tue Jun 23 09:02:22 PDT 2015


Hello all,

 

We usually do the following to calibrate model to monthly utility bills:

1)      Create or purchase weather file corresponding to pre-retrofit period
for which we have billing data. Lately we've been using WeatherAnalytics
files, which we found to be more cost effective than creating our own (they
charge $40 for an annual file).

2)      Run simulation using this weather file instead of TMY.

3)      Standard simulation reports (we typically use eQUEST) show usage by
calendar month (e.g. January, February, etc.) which is usually not aligned
with dates of utility bills, as noted in the question that started this
thread. As Brian mentioned in one of the earlier posts, this may be
circumvented by entering the actual meter read dates into eQUEST as shown in
the screenshot below. This will align usages shown in eQUEST's "E*" reports
such as ES-E with the actual utility bills.  The approach does not allow
entering more than one read date per month (e.g. we can't capture April 3 -
28 bill). For projects where this limitation is an issue we generate hourly
reports that show consumption by end use for each meter in the project, and
aggregate it into periods that are aligned with utility bills. 



  

4)      We then copy simulation outputs (either from ES-E or hourly reports,
depending on the method used) into a standard spreadsheet with utility data.
The spreadsheet is set up to plot side by side monthly utility bills and
simulated usage, and also calculates normalized mean bias error (NMBE) and
variance CV(RMSE).   

5)      If we did not to where we want to be with NMBE and CV(RMSE) we
adjust and re-run the model, and re-paste results into the same spreadsheet.


 

In my experience regression analysis using weather as independent variable
(i.e. running model with TMY file and normalizing for difference in weather)
or relying on HDD to allocate usage to billing periods can be very
misleading, mainly because on many projects weather is not the main driver
of consumption. For example energy usage of a school during a given time
period depends much more on vacation schedule than outdoor dry bulb
temperatures.  

 

Thanks,

 

-- 

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

 <http://www.karpmanconsulting.net/> www.karpmanconsulting.net 

Phone 860.430.1909 

41C New London Turnpike

Glastonbury, CT 06033

 

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of
Jeff Haberl
Sent: Tuesday, June 23, 2015 10:16 AM
To: Joe Huang; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Energy model calibration - normalizing the utility
bills to month start-end

 

Hello Joe,

 

Yes, you can count the degree days and regress against that to show a
correlation. However, one will get a better "fit" to the weather data if you
regress to the degree day that is calculated for the balance point
temperature of the building -- hence the inverse model toolkit or the
variable based degree day method.

 

PRISM actually calculates the degree days to a variety of change points and
actually provides a table for each location that you use as a look up. The
IMT will actually perform a variable based degree day calculation that
agrees well with PRISM. IMT will also provide you with the average daily
temperature for the billing period.

 

When using DOE-2 for actual billing periods, one will have to extract the
appropriate hourly variable, sum it to daily and then regroup to align with
the billing periods. Here's a chunk of code that will create a dummy plant,
display PV-A, PS-A, PS-E and BEPS, and extract the relevant hourly variables
to normalize the BEPS to the utility bills:

 

INPUT PLANT ..

 

PLANT-REPORT VERIFICATION = (PV-A)

$ PV-A, EQUIPMENT SIZES

 

SUMMARY = (PS-A,PS-E,BEPS)

 

$ PS-A, PLANT ENERGY UTILIZATION SUMMARY

$ PS-E, MONTHLY ENERGY END USE SUMMARY

$ BEPS, BUILDING ENERGY PERFORMANCE SUMMARY

 

HVAC=PLANT-ASSIGNMENT ..

 

$ EQUIPMENT DESCRIPTION

$ ELECTRIC DOMESTIC WATER HEATER

 

BOIL-1 =PLANT-EQUIPMENT TYPE=ELEC-DHW-HEATER SIZE=-999 ..

 

$ ELECTRIC HOT-WATER BOILER

 

BOIL-2 =PLANT-EQUIPMENT TYPE=ELEC-HW-BOILER SIZE=-999 ..

 

$ HERMETICALLY SEALED CENT CHILLER

 

CHIL-1 =PLANT-EQUIPMENT TYPE=HERM-CENT-CHLR SIZE=-999 ..

 

$ Graphics block for Data Processing ***

 

RP-3 = SCHEDULE THRU DEC 31 (ALL) (1,24) (1) ..

 

$ 8 = Total PLANT heating load (Btu/h)

$ 9 = Total PLANT cooling load (Btu/h)

$ 10 = Total PLANT electric load (Btu/h)

 

BLOCK-3-1 = REPORT-BLOCK

VARIABLE-TYPE = PLANT

VARIABLE-LIST = (8,9,10) ..

BLOCK-3-2 = REPORT-BLOCK

VARIABLE-TYPE = GLOBAL

VARIABLE-LIST = (1) ..

HR-3 = HOURLY-REPORT

REPORT-SCHEDULE = RP-3

REPORT-BLOCK = (BLOCK-3-1,BLOCK-3-2) ..

 

END ..

 

COMPUTE PLANT ..

 

STOP ..

 

8=!  8=)  :=)  8=)  ;=)  8=)  8=(  8=)  8=()  8=)  8=|  8=)  :=')  8=) 8=?
Jeff S. Haberl, Ph.D.,P.E.inactive,FASHRAE,FIBPSA,......jhaberl at tamu.edu
<mailto:........jhaberl at tamu.edu> 
Professor...................................................................
.....Office Ph: 979-845-6507
Department of Architecture............................................Lab
Ph:979-845-6065
Energy Systems Laboratory...........................................FAX:
979-862-2457
Texas A&M
University...................................................77843-3581
College Station, Texas, USA,
77843.............................http://esl.tamu.edu
8=/  8=)  :=)  8=)  ;=)  8=)  8=()  8=)  :=)  8=)  8=!  8=)  8=? 8=) 8=0

  _____  

From: Bldg-sim [bldg-sim-bounces at lists.onebuilding.org] on behalf of Joe
Huang [yjhuang at whiteboxtechnologies.com]
Sent: Monday, June 22, 2015 9:17 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Energy model calibration - normalizing the utility
bills to month start-end

Maybe I'm missing something here, but why can't you just count up the degree
days for the utility period?
I hope you're not working with average or "typical year" degree days, but
the degree days from the same time period.

I also recall that the old Princeton Scorekeeping Method (PRISM) back in the
1980's allows the user to enter the degree days for that time period, so
it's not a new problem.

Joe




Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 6/22/2015 6:09 AM, Jones, Christopher wrote:

When calibrating an energy model to utility bills the utility bills often
don't align with the month start and end.  I have reviewed a couple methods
to calendar normalize the utility bills but find them somewhat
unsatisfactory.

 

For example the method I am looking at does the following:

The April gas bill runs from March 25 - April 24.  The algorithm takes the
average number of m3 per day from that bill, applies it to the days in
April.  Then it takes the average number of days from the May bill which
runs from April 24 - May 25 and applies that average to the remaining days
in April.  

 

The issue is that the March-April period has much higher HDD than the
April-May period and the "normalized" gas usage is significantly lower than
the simulation data for April.

 

I am wondering if there are any papers or other sources of information as to
how others approach this problem.

 

 

cid:image003.png at 01D09C46.E75BA0D0

Christopher Jones,P.Eng. 
Senior Engineer

 

WSP Canada Inc.

2300 Yonge Street, Suite 2300

Toronto, ON M4P 1E4
T +1 416-644-4226

F +1 416-487-9766

C +1 416-697-0065

 

www.wspgroup.com <http://www.wspgroup.com/>  

 

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