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

[Joe Huang]

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
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 6/23/2015 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
> *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.
>
> 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 <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
> 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 <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
> (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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