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<p>Nick,</p>
<p>This is an interesting topic that has evolved in an unexpected
way. Now that NREL has mastered the technology of
satellite-derived solar radiation, they have regarded weather
station data as an impediment, since there's no way to get such
measured data to match the 5-kilometer grid of the
satellite-derived solar. Therefore, they have abandoned the
weather station data (which was was used in all the TMYs to date)
and gone instead to Reanalysis Data from NOAA's MERRA, which is
running a climate forecasting model in retrospective mode. I don't
have time now to discuss reanalysis, except to say that from what
I've seen the results are decidedly "iffy". Almost two years ago,
I managed to get a Work Statement through ASHRAE for someone to
take a good look at reanalysis data.</p>
<p>So, what does this mean for your question? NREL's National
Solar Radiation Data Base (NSRDB) can now get you the hourly time
series or a TMY for more than a million grid points over the US,
all with satellite-derived solar radiation but MERRA results for
the other climate parameters. I've told NREL several years ago
that for the building simulation industry it would be much better
to merge the satellite-derived solar with actual station data
that give good accurate coverage of urban areas where buildings
are located. NREL's response was that they'd be happy to do this,
but someone has to pay them for the work. <br>
</p>
<p>In response to your hypothesis below, I think you're being too
disparaging of the previous modeling efforts while raising too
high your expectations of satellite solar. It's not that the
previous models failed to account for local climate conditions,
but that they lacked good data to drive them. For example, all
models included terms for cloud cover and clearness, or for the
more detailed physical models arcane parameters like aerosol
optical depth, preciptable moisture, etc., but how available are
the input data and how reliable are they? The advantages of
satellite-derived solar are that they provide a comprehensive and
objective view of the cloud conditions, which combined with
satellite measurements of the atmospheric conditions and improved
modeling, results in accuracies that previous modeling efforts
can not attain. As far as discerning localized effects of smog
and dust in urban areas, that would still depend on whether
there's sufficient monitoring at that spatial and time scale to
detect the differences. What I mean is that it's one thing to
observe that in general urban locations have more smog and
particulates than rural locations, but it's something else to
quantify the resultant differences in solar radiation over time
and distance.</p>
<p>I'd like to take the opportunity here to step back and comment on
the status of weather data for the building energy community, My
interactions with NREL has brought the realization that we have
been piggy-backing on the efforts of others outside our community
for our weather data. I don't intend to pick on the NREL Solar
Program, several of whom I consider friends and colleagues, but
their target client is the solar power industry. Since solar
power arrays can be installed anywhere, preferably in rural
uninhabited locations, it makes sense to go to satellite-derived
solar. It's also clear that to serve that industry, NREL would
focus its efforts on getting the best solar values, while all the
other climatic parameters, like temperature, humidity, wind speed,
etc., are secondary, which may be why getting them from MERRA is a
satisfactory choice. The focus on solar is also evident in the
weighting used by NREL to develop the TMYs, with 50% weight placed
on the 2 solar and 50% on the remaining 8 non-solar parameters. <br>
</p>
<p>For the building energy community, or priorities are somewhat
different. Since 99% of buildings are located in urban locations,
we should focus much more on climate in urban areas. Luckily,
that's also where the great majority of existing weather are
located, which is why I'm resistant to throwing out measured
weather data and replacing them with synthetic data, no matter how
much they've been "seeded" with real data. As for the weighting of
climate parameters in selecting the typical months, why not use
building energy simulations and weight them by the distribution of
heating and cooling loads? <br>
</p>
<p>Joe</p>
<pre class="moz-signature" cols="90">Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
<a class="moz-txt-link-abbreviated" href="mailto:yjhuang@whiteboxtechnologies.com">yjhuang@whiteboxtechnologies.com</a>
<a class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com">http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
</pre>
<div class="moz-cite-prefix">On 1/2/2018 9:30 AM, Nicholas Caton
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:VI1PR0402MB28144BD8601BE7923C9CCB19B6190@VI1PR0402MB2814.eurprd04.prod.outlook.com">
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<p class="MsoNormal"><span style="color:windowtext">Hi Joe,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">From your
perspective, are NREL or any other government/professional
bodies making moves/indications to update/refresh the
current TMY3 sets to utilize satellite-derived solar
radiation? Seems like a no-brainer for our industry, but is
there a counter-argument? It seems likely, but has there
been rigorous comparisons of satellite-derived solar
radiation against measured values and/or our “present-day”
solar models used to derive solar radiation information for
building energy simulation?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Also, I’m
trying to understand and correctly characterize the impact
of this development in simple terms my brain can follow. Is
it fair to say:
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span
style="color:windowtext">The solar models used in developing
weather files for building energy simulations to-date in our
industry (including all/most industry-standard TMY weather
sets), because they have been using solar radiation derived
from (evolving) solar models, have <u>not</u> accounted for
the likes of local climate cloud cover / smog / dust?
Seattle (~47</span><span style="color:windowtext">°</span><span
style="color:windowtext">N) has perhaps been seeing as much
sunlight through the winter as Paris (~48</span><span
style="color:windowtext">°</span><span
style="color:windowtext">N)?<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span
style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span
style="color:windowtext">Does satellite-derived solar
radiation address some or all of these local climate issues
(cloud cover, smog, dust) affecting direct/indirect solar
radiation?
<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span
style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Thanks
sincerely for all your teaching Joe,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">~Nick<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-family:"Arial",sans-serif;color:#3A7A46"><img
style="width:7.5625in;height:.0937in"
id="Picture_x0020_1"
src="cid:part1.07872FEA.8D9B98D3@whiteboxtechnologies.com"
class="" height="9" width="726"><o:p></o:p></span></p>
<p class="MsoNormal"><b><span
style="font-family:"Arial",sans-serif;color:#3A7A46">Nick
Caton, P.E., BEMP</span></b><span style="color:#3A7A46"><o:p></o:p></span></p>
<table class="MsoNormalTable"
style="width:543.0pt;border-collapse:collapse"
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<td style="width:172.3pt;padding:0in 0in 0in 0in"
valign="top" width="230">
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style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">
Senior Energy Engineer</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><br>
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">
Regional Energy Engineering Manager<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">
Energy and Sustainability Services</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><br>
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">
Schneider Electric</span><span
style="color:#1F497D"><o:p></o:p></span></p>
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valign="top" width="291">
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style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">913.564.6361
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><br>
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#57B069">M </span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">785.410.3317
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><br>
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#57B069">F </span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">913.564.6380</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><br>
</span><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#57B069">E </span><span
style="color:#1F497D"><a
href="mailto:nicholas.caton@schneider-electric.com"
moz-do-not-send="true"><span
style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#626469">nicholas.caton@schneider-electric.com</span></a><o:p></o:p></span></p>
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United States</span><span style="color:#1F497D"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
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<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="color:windowtext">From:</span></b><span
style="color:windowtext"> Equest-users
[<a class="moz-txt-link-freetext" href="mailto:equest-users-bounces@lists.onebuilding.org">mailto:equest-users-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Joe Huang via Equest-users<br>
<b>Sent:</b> Thursday, December 14, 2017 8:13 PM<br>
<b>To:</b> BLDG-SIM
<a class="moz-txt-link-rfc2396E" href="mailto:bldg-sim@lists.onebuilding.org"><bldg-sim@lists.onebuilding.org></a>;
EnergyPlus_Support
<a class="moz-txt-link-rfc2396E" href="mailto:EnergyPlus_Support@yahoogroups.com"><EnergyPlus_Support@yahoogroups.com></a>;
<a class="moz-txt-link-abbreviated" href="mailto:equest-users@lists.onebuilding.org">equest-users@lists.onebuilding.org</a><br>
<b>Subject:</b> [Equest-users] White Box Technologies
brings simulation weather data to the satellite age<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p>It is with joy and some trepidation to report that White Box
Technologies (WBT) is updating all its historical weather
files with satellite-derived solar radiation. Joy because this
overcomes what has been the most significant question mark
with weather files; trepidation because of the amount of work
needed to carry out and maintain this effort. To show that
this is more than marketing hype, I need to give a rather long
explanation about this development.<br>
<br>
The bane of weather data over the past three decades has been
the solar radiation (global horizontal and direct normal)
which are not measured parameters, but derived using various
solar and sky models. All the familiar "typical year" sets,
i.e., TMY, WYEC, IWEC, etc., let alone the historical weather
files, have modeled solar radiation. Although a lot of<br>
work has gone into such models (see M. Iqbal,"An Introduction
to Solar Radiation", Academic Press, 1983), there remain an
almost intractible problem of the lack of good measured solar
to tune any of these models. For example, in the ASHRAE IWEC2
weather files, my team was able to find one or two years'
measured data for less than 50 locations,<br>
from which were derived 28 sets of regression coefficients
then used for all 3,012 IWEC2 locations.<br>
<br>
For the past decade and a half, researchers around the world
have been working to derive solar radiation from weather
satellite imagery, driven largely by the needs of the solar
power industry for the siting of solar power plants and
getting "bankable" solar estimates for their arrays. Our
little building energy simulation sector can of course benefit
by hanging on the coattails of the solar power industry, but
the downside has been to be totally priced out, since the
commercial cost for one year's solar data for one location
(grid cell) typically runs around $1,000.<br>
<br>
A welcome development over the last five years is that various
government offices or affiliated consortia are now beginning
to also providing access to satellite-derived solar radiation
at minimal or more acceptable costs under various conditions.
Over the past three years, WBT has obtained access to such
data and permission for its use in WBT weather files.<br>
WBT is now either replacing the solar radiation on its
historical weather files, or using satellite-derived radiation
to develop custom solar coefficients for each location to
extend the satellite-derived solar to time periods outside the
available time window. With the exception of polar locations
above or below 60/66 degrees, island nations in the Pacific
and Indian Ocean, and a few unfortunate "blind spots", the
entire land mass is being covered with at least 10 years up to
18 years of hourly solar records.<br>
<br>
Starting in 2018, WBT historical weather files in the
following areas will all have satellite-derived solar
radiation for the following time periods: Europe, Africa,
South America east of 66 West, i.e., Brazil and Uruguay (2004
to date), Australia (1999 to date), and East Asia (2007 to
date, access pending). WBT historical weather files in the
following areas will have satellite-derived solar radiation
for the indicated time periods - North America and
Central/South American down to 20 South (1998-2015), South
Asia (2000-2014), with modeled solar radiation from 2016 on
that has been individually tuned to the past satellite-derived
solar.<br>
<br>
Another benefit to the satellite-derived solar is to increases
the number of available weather stations, which in many places
has been limited by the lack of cloud cover data needed to
model the solar radiation. For reasons that are not
immediately identifiable, several English-speaking
Commonwealth countries has seen a marked drop in the number of
available stations due to the decreases in the reporting of
cloud cover (see plot, ZAF = South Africa). For example, the
number of stations in the UK has dropped by almost 2/3s
between 2001 and 2017 (174 to 64), but with satellite-derived
solar, it will go back up to over 180, while in Australia and
South Africa the comparable numbers are from 175 to well over
500, and from 37 to over 100, respectively.<br>
<img style="width:6.5104in;height:3.5104in" id="_x0000_i1025"
src="cid:part4.EA45B74D.0554CF2C@whiteboxtechnologies.com"
class="" height="337" width="625" border="0"><br>
If interested, customers who have purchased a historical
weather files from WBT over the past five years can get an
updated weather file at no cost. Lastly, although it will take
at least a month to update all 10,000 2017 files, it's very
quick to do for any specific location or even 50 or so
locations. Therefore, if you have an urgent request please
e-mail me and I will put that at the beginning of the queue
for that day.<o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>Joe Huang<o:p></o:p></pre>
<pre>White Box Technologies, Inc.<o:p></o:p></pre>
<pre>346 Rheem Blvd., Suite 205A<o:p></o:p></pre>
<pre>Moraga CA 94556<o:p></o:p></pre>
<pre><a href="mailto:yjhuang@whiteboxtechnologies.com" moz-do-not-send="true">yjhuang@whiteboxtechnologies.com</a><o:p></o:p></pre>
<pre><a href="http://weather.whiteboxtechnologies.com" moz-do-not-send="true">http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data<o:p></o:p></pre>
<pre>(o) (925)388-0265<o:p></o:p></pre>
<pre>(c) (510)928-2683<o:p></o:p></pre>
<pre>"building energy simulations at your fingertips"<o:p></o:p></pre>
</div>
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