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

Maria Karpman maria.karpman at karpmanconsulting.net
Tue Jun 23 12:04:40 PDT 2015


Jim and all,

 

We have incentive programs in NY (Multifamily Performance Program) and NJ (Pay for Performance Program for C&I buildings, P4P) that require developing calibrated models to estimate ECM savings. Both programs rely on spreadsheet-based tools to facilitate model calibration, and require that the proposed ECM package reduces overall energy consumption by at least 15%. The programs have been around for 5+ years, and have hundreds of participating projects. Part of the incentive is awarded based on the projected (i.e. modeled) savings, and the rest (as much as 50% for P4P) based on the actual achieved savings established using Whole Building approach by comparing pre/post utility bills. 

 

My biggest take away from the involvement with these programs was that a calibrated model that meets MBE,  CVRMSE, and uncertainty requirements of Guideline 14 may produce grossly incorrect ECM savings. It is not feasible to create a calibrated model that can be reliably used to project savings from any conceivable ECM in a commercial non-research setting because, aside from the modeling effort, it would require a lot of very detailed field work. On the other hand, developing a calibrated simulation to estimate savings from a particular set of measures considered for a given project is a much more manageable task. So the bulk of the recent updates to the technical requirements of our incentive programs were focused on itemizing parameters that should be tweaked to achieve calibration depending on the ECMs included in the project scope. For example, if project involves boiler replacement, efficiency of existing boilers that are being replaced must be measured. (We had a project which modeled existing boiler as 35% efficient because that produced calibrated simulation. Of course such model would very likely exaggerate savings from installing a new boiler.) 

 

Do any of you know references that outline calibration techniques depending on the ECMs being modeled, beyond the general advice included in IPM&VP?

 

Thanks,

 

Maria

 

-- 

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 Jim Dirkes
Sent: Tuesday, June 23, 2015 1:31 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Energy model calibration - normalizing the utility bills to month start-end

 

I'm encouraged to see so many people addressing this topic because it means you are modeling existing buildings; a lot of work is needed in this arena.  Keep it up!

 

We, as usual, have a spreadsheet solution.  In this case, the spreadsheet is happy to use billing periods of any length, such as is normal for day-of-reading variations, but also to combine "estimated" readings into a period that has an actual reading at each end.

It requires that you tell EnergyPlus to report hourly meter data for each fuel (e.g., electricity and natural gas).  A macro totals that data into the billing periods for your site, displays the predicted vs actual energy and calculates an R-squared value for each fuel and the total. An example is shown below.

 

Inline image 1

 

On Tue, Jun 23, 2015 at 12:02 PM, Maria Karpman <maria.karpman at karpmanconsulting.net> wrote:

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

www.karpmanconsulting.net <http://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

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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 <tel:%28925%29388-0265> 
(c) (510)928-2683 <tel:%28510%29928-2683> 
"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.

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Toronto, ON M4P 1E4
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-- 

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim at buildingperformanceteam.com

Website  <http://buildingperformanceteamcom> l  LinkedIn <https://www.linkedin.com/pub/jim-dirkes/7/444/413> 

Studies show that four out of every three people have a hard time with math.

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