[Bldg-sim] What do people do about Leap Years? was Re: Energy model calibration - normalizing the utility bills to month start-end

James Hansen jhansen at ghtltd.com
Tue Jun 23 14:17:53 PDT 2015


Getting upset that eQuest / DOE-2 doesn’t incorporate leap year data is like getting upset that it can’t predict a snow day.  Or a power outage.  If you are using an energy model for a specific task where missing 1 day in 1,460 is going to affect someone’s decision making process, and/or you’re not willing to multiply February energy consumption by 29/28 for that year, then that is worrisome.  No energy modeling program is so accurate that this would make a difference.  But that’s just my opinion.  I have lots of scratches on my car and don’t care…

-James

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Tuesday, June 23, 2015 4:57 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] What do people do about Leap Years? was Re: Energy model calibration - normalizing the utility bills to month start-end

I hear your frustrations Joe, but after finding many, many issues with eQuest/Doe-2 that never got fixed, I eventually did "just" switch to EnergyPlus.  I'm not sure when the last time DOE2 got a major update, but EnergyPlus is getting major updates all the time.  There are people actively supporting this software and every bug and idiosyncrasy I've found has either been fixed, or is in the cue to be fixed.

In my opinion, this community needs to either:

1.  Support a major update to eQuest/DOE-2 that fixes this, and many other issues.  If you are capable and interested in fixing some of these bugs - maybe try a crowdfunding campaign?  People could contribute towards fixing particular issues or bugs.
2.  Recognize the limitations of eQuest/ DOE-2 and use it only when projects can be appropriately modeled with this software.
3.  Switch software packages completely.

One of the challenges in this industry is that people are used to getting software for free.  eQuest, DOE-2, EnergyPlus have all be developed in large part with public funding.  When that funding goes away, support stops, but people still have the expectation that the software should be free.

--
Karen

On Tue, Jun 23, 2015 at 4:43 PM, Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>> wrote:
The responses so far are not what I expected and, in my view, miss the point.
I was not talking about workarounds or ignoring the missing day in DOE-2, which is what I presume everyone has been doing up until now.  I'm frankly tired of that, because adding the fixes to DOE-2 seems to be quite easy to do.

I also find the responses of "just use EnergyPlus" to be disingenuous and condescending.  It's like trying to fix a scratch on your car, and then somebody comes by and says, "oh, just go and buy this new better one".

Joe


Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 205A

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto: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 6/23/2015 1:21 PM, Justin Spencer wrote:
I think the cleanest is you just pretend every day is off by one. Ignore all of the month garbage (yes you'll be off by a day at times). Just think about it as days 1-365, with the right day of the week assigned. You can reassign your holidays if you want. You wind up dropping the real 12/31.

But I like the "just use EnergyPlus" option.

On Tue, Jun 23, 2015 at 12:57 PM, Jim Dirkes <jim at buildingperformanceteam.com<mailto:jim at buildingperformanceteam.com>> wrote:

  1.  Use EnergyPlus :), which allows >365 days.  This is also helpful when the combined two-fuel billing cycle is 13-14 months.
  2.  Ignore the 1/365 difference.  Do you really think it will matter much?

On Tue, Jun 23, 2015 at 2:48 PM, Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>> wrote:
This is a little off-topic, but something I've pondered for some time...

The question is when people are using eQUEST/DOE-2 with historical year weather, what do you do when it's a leap year?  Since DOE-2
always simulates a 365-day year,  do you just ignore the missing leap day, but then don't the Days of Week also get screwed up starting in March?

Since a quarter of the years are leap years, I've never understood why accounting for them has been considered an insignificant detail.
I mean, if I told you that a quarter of the time your simulation results would be a little wrong, isn't that a pretty high frequency?

Many eQUEST/DOE-2 users also have the mistaken impression that the fault lies in the DOE-2 weather files, which is not true.
Believe it or not, but the packed DOE-2 weather file format actually contains 384 days (32 days per month), and all the DOE-2 weather files I produce always contains Feb. 29 for the leap years (as well as other enhancements like greater precision in the data).

So, where does the problem lie?  It's in the clock within DOE-2 that always sets February to be 28 days.  In other words, DOE-2 will read the weather file and do the simulation only through February 28th, even though the weather file contains data through February 32nd (:-)), although everything beyond the 28th would be blank on non-leap years, and beyond the 29th on leap years.

When I've looked through the DOE-2.1E code, there are even flags setting the leap years but these are never used. I've thought many times of toying around with the code to see how difficult it would be to implement leap years, but just haven't gotten around to it.  As far as I can see, the biggest difficulty might might have to do not with the simulation itself, but with the reporting.

I'd like to know if others think this is something of sufficient importance to merit further investigation.

Joe



Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 205A

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto: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 6/23/2015 10:27 AM, Collinge, William Overton wrote:
All,

This is a fantastic thread, and I am wondering if it could be taken one step further to query if anyone has experience with methods to attempt calibrating models of energy savings attributable to retrofits of multiple systems simultaneously (plant, envelope, HVAC etc. – as most real-world retrofits likely are), going past the 4- or 5-parameter breakpoint regression models to incorporate inverse modeling of specific load types and their space- or time-variable characteristics. This would fit under multivariate methods in the last line of Table 2 in the older version of ASHRAE Guideline 14 that Jeff Haberl has posted on his website, and would attempt to standardize Maria’s Step 5 below without (possibly) the need to conduct as much in-depth field verification as might otherwise be required. I’ve dabbled in this a little bit…without extensive discussions with others…

Example: changing the OA ventilation rate is going to have a specific load profile versus some retrofit that affects the solar gain rate. Of course, much easier in theory to do calibrations of this sort with hourly meter data versus monthly utility bills…

Bill Collinge
Postdoctoral Scholar
University of Pittsburgh
Department of Civil and Environmental Engineering



From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Maria Karpman
Sent: Tuesday, June 23, 2015 12:02 PM
To: 'Jeff Haberl'; 'Joe Huang'; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] Energy model calibration - normalizing the utility bills to month start-end

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.

[cid:image001.png at 01D0ADD6.D9D5F9F0]



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<tel: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<mailto: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<tel:979-845-6507>
Department of Architecture............................................Lab Ph:979-845-6065<tel:979-845-6065>
Energy Systems Laboratory...........................................FAX: 979-862-2457<tel: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<mailto:bldg-sim-bounces at lists.onebuilding.org>] on behalf of Joe Huang [yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>]
Sent: Monday, June 22, 2015 9:17 PM
To: bldg-sim at lists.onebuilding.org<mailto: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<mailto: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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CEO/President
The Building Performance Team Inc.
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Direct: 616.450.8653<tel:616.450.8653>
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