[Bldg-sim] historic weather files for model calibration

[David Reddy]

Aaron-

The question "are model results significantly impacted by the difference 
between historic weather data and performance-period data" is a complex 
one, however, here is an approach that may be helpful if you need to 
construct your own custom weather file.

You can purchase historical weather data available from NOAA station 
data from the NCDC <http://www.ncdc.noaa.gov/oa/ncdc.html>.  However, 
these data sets do not include solar radiation data and often need some 
QC work (remove extraneous observations, fill gaps, etc).  In the past, 
I have also downloaded weather data from the EnergyPlus 
<http://apps1.eere.energy.gov/buildings/energyplus/weatherdata_download.cfm> 
site in IWEC format, and converted to .bin using a combination of the E+ 
weather data processor and EPW conversion tool available on the DOE-2 
Website <http://doe2.com/index_Wth.html#eQ_WthProc>.  However, although 
a great deal (a FREE service), in my experience, this data can have gaps 
that are too large to fill with the algorithms NREL prescribes, which 
then leads you to either piecing this together w/ some other data 
source, or, only evaluating the model performance over the periods you 
have data for.  For many of my projects, I need a complete year or more, 
so the E+ method was not ideal.

I recently created some DOE-2 .bin weather files using the following 
approach, using data formatting/calculation procedures automated in 
MATLAB, and then the "DOEWth.exe" utility (an older, command line 
program also available from DOE-2.com) to generate a .bin weather file.  
Once automated, this process can be completed in a relatively short 
period of time. The following is a brief explanation of the process I 
used that may give you some ideas:

1)  Downloaded NOAA data (Integrated Surface Data) for closest site.

2)  Cleaned data of extraneous points and filled gaps in data using NREL 
<http://apps1.eere.energy.gov/buildings/energyplus/pdfs/weatherdata_guide_34303.pdf> 
filling routines.  There is usually always one or more observations 
recorded for every hour, however, in many cases one or more of the 
variables you need for the simulation weather file may not have been 
reported.

If you can obtain measured solar data for your location, skip steps 3-5

3)  Used the Zhang-Huang solar model (discussed in the E+ engineering 
manual) to estimate total horizontal solar radiation with custom model 
parameters developed using least-squares regression to TMY3 data.  In 
this case, I assumed TMY data was more or less "true", however, for one 
station data I worked with, I noticed some cloud cover observations did 
not appear to be consistent the reported solar radiation data.  However, 
the custom coefficients yeilded better results than the default 
coefficients reported in the E+ literature when I compared the model 
output to a short sample of actual measured solar radiation data I had.

4)  Used another model to determine the diffuse solar radiation 
component from the total global radiation.  In my case, I used a custom 
model developed for the Pacific NW (published in a thesis) however, 
there are many similar models developed from various datasets.  Orgill 
and Hollands is a popular model, although they are all very similar.

5) Once you have the two solar components above, direct normal solar 
radiation can be readily calculated.

6) With all of the necessary data now assembled, format into the TMY2 
format for processing into a .bin file using the DOEWth utility.  Using 
the DOEWth output summary file and a weather file plotting program, like 
D-View, you can "inspect" the measured data to make sure it matches what 
you expect and aligns with daily or month averages more readily available.

A few notes:
- The DOEWth utilty does have format methods that will calculate solar 
data, however, I choose to pre-process the solar data using the solar 
radiation models I preferred, which leads you to using the TMY2 format 
method.
- I did not calculate illuminance data since my project did not include 
daylighting controls.  There are models available for calculating 
illuminance, and the DOE-2 program may use a model to estimate it from 
solar radiation data (need to brush up on this section of the engineers 
manual to confirm this).
-  Related to the above comment, there are many different models out 
there for calculating solar radiation/illuminance data from other 
measured parameters. I choose the above because I felt like the models 
best captured the variables that I thought were important, and to  
lesser degree, I could readily implement them in my programming.  Other 
than comparing these models to actual TMY data, I have not rigorously 
compared these model to others available, so you may want to explore 
others.
- For any source of weather data you pursue, I would emphasize reviewing 
how data is filled and non-measured variables are calculated (i.e. what 
models were used).

I just realized this post may use the word "model" a record number of 
times, but hope you find it useful.


David Reddy

360 Analytics
Building Energy Analysis Consultants
mail:	12354 16th Ave NE, Seattle, WA 98125
office: 206.420.7918
mobile:	206.406.9856
web:	www.360-Analytics.com




On 11/29/2010 11:54 AM, Dahlstrom, Aaron wrote:
>
> A recent LEED MV plan review comment asked "please indicate the 
> proposed calibration method to account for the local weather 
> conditions during the performance period."
>
> This raises the question for me - are model results significantly 
> impacted by the difference between historic weather data and 
> performance-period data?
>
> When I'm engaged in Measurement and Verification, I can install a 
> weather station that records data for performance period to allow for 
> calibration. 
> (http://www.gsd.harvard.edu/research/gsdsquare/Publications/BuildingSimulation2009.GundHallModel.pdf)
>
> But for an investment-grade energy audit with historic bills, I'm not 
> sure where to turn for all the variables needed to construct a weather 
> file.
>
> Anyone on this list have a recommendation?
>
> (I'm specifically looking for NYC, 2009, weather data for an eQUEST 
> model.)
>
> *Aaron Dahlstrom , PE, LEED® AP*
>
> *In P**o**sse*-- A subsidiary of*AKF*| 1500 Walnut Street, Suite 1414, 
> Philadelphia, PA 19102
>
> d: 215-282-6753| m: 267-507-5470| In Posse: 215-282-6800| AKF: 
> 215-735-7290
>
> e: ADahlstrom at in-posse.com | in posse web: www.in-posse.com 
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>
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