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Aaron- <br>
<br>
The question "<span style="font-size: 12pt;">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.</span><br>
<br>
You can purchase historical weather data available from NOAA station
data from the <a href="http://www.ncdc.noaa.gov/oa/ncdc.html">NCDC</a>.
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 <a
href="http://apps1.eere.energy.gov/buildings/energyplus/weatherdata_download.cfm">EnergyPlus</a>
site in IWEC format, and converted to .bin using a combination of
the E+ weather data processor and EPW conversion tool available on
the <a href="http://doe2.com/index_Wth.html#eQ_WthProc">DOE-2
Website</a>. 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.<br>
<br>
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:<br>
<br>
1) Downloaded NOAA data (Integrated Surface Data) for closest site.<br>
<br>
2) Cleaned data of extraneous points and filled gaps in data using
<a
href="http://apps1.eere.energy.gov/buildings/energyplus/pdfs/weatherdata_guide_34303.pdf">NREL</a>
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. <br>
<br>
If you can obtain measured solar data for your location, skip steps
3-5<br>
<br>
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. <br>
<br>
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.<br>
<br>
5) Once you have the two solar components above, direct normal solar
radiation can be readily calculated.<br>
<br>
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.<br>
<br>
A few notes:<br>
- 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.<br>
- 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). <br>
- 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. <br>
- 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). <br>
<br>
I just realized this post may use the word "model" a record number
of times, but hope you find it useful.<br>
<br>
<br>
<pre class="moz-signature" cols="72">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: <a class="moz-txt-link-abbreviated" href="http://www.360-Analytics.com">www.360-Analytics.com</a></pre>
<br>
<br>
<br>
On 11/29/2010 11:54 AM, Dahlstrom, Aaron wrote:
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<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">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.”<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">This raises
the question for me - are model results significantly
impacted by the difference between historic weather data and
performance-period data?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">When I’m
engaged in Measurement and Verification, I can install a
weather station that records data for performance period to
allow for calibration. (<a moz-do-not-send="true"
href="http://www.gsd.harvard.edu/research/gsdsquare/Publications/BuildingSimulation2009.GundHallModel.pdf">http://www.gsd.harvard.edu/research/gsdsquare/Publications/BuildingSimulation2009.GundHallModel.pdf</a>)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">Anyone on
this list have a recommendation? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;">(I’m
specifically looking for NYC, 2009, weather data for an
eQUEST model.)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 12pt;"><o:p> </o:p></span></p>
<p class="MsoNormal" style="line-height: 150%;"><b><span
style="font-size: 9pt; line-height: 150%; font-family:
"Verdana","sans-serif"; color: gray;">Aaron
Dahlstrom , PE, LEED® AP</span></b><o:p></o:p></p>
<p class="MsoNormal" style="line-height: 150%;"><b><span
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