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Yes, interesting idea and glad to see it discussed here. <br>
<br>
This idea also occurred to us when evaluating PV systems on a number
of buildings in Hawaii. In that project, we were fortunate enough
to have a <a href="http://www.nrel.gov/midc/nelha/">solar
monitoring site</a> right down the street, and he had 15min and
1hour PV energy generation for every panel (micro-invertors) on 15
different buildings, each oriented in the same direction. However,
some other issues, besides the one's Joe described, came to mind in
trying to develop a model that linked the two:<br>
<ul>
<li>In addition to temperature, PV panels energy production also
degrades as the panels get dirty. That seemed like the variable
that is toughest to compensate for. <br>
</li>
<li>Data connection between the inverters to the cloud was pretty
good, but we did find gaps a number of gaps; sometimes for up to
a month or two. </li>
</ul>
<p>Still yes, an interesting idea, and sounds like a good research
project...<br>
David<br>
</p>
<br>
<div class="moz-cite-prefix">On 7/20/2015 4:07 PM, Joe Huang wrote:<br>
</div>
<blockquote cite="mid:55AD7F35.50307@whiteboxtechnologies.com"
type="cite">
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This is an intriguing idea (using PV output as a surrogate for
irradiance), but there are a number of complications that need to
be investigated:<br>
1. PV efficiency degrades with temperature; therefore, you have to
have some way to adjust the output by the temperature of the PV
(not the air temperature)<br>
2. you also need to adjust for the tilt and azimuth of the PV
panels to derive the equivalent global horizontal radiation.<br>
3. you also need to split the global horizontal into direct and
diffuse radiation, which could be done using a number of
direct/diffuse split models, which is what's done for 99% of the
weather files anyway because I've yet to find any measured direct
normal radiation outside of strictly research applications.<br>
<br>
When I look at this list, all three could be done using a building
energy simulation program, provided that you know the
absorptivity of the PV and its conversion efficiency as a function
of temperature, but at this point it's getting more hairy than
calculating the solar radiation from standard weather station data
or, beginning in Sept 2015 for US locations, downloading the solar
radiation from NREL. <br>
<br>
I'm not being critical, and actually I am quite intrigued by this
technique, and would be happy to help evaluate how well it works.<br>
<br>
Joe<br>
<br>
<pre class="moz-signature" cols="72">Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:yjhuang@whiteboxtechnologies.com">yjhuang@whiteboxtechnologies.com</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com">http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.whiteboxtechnologies.com">http://www.whiteboxtechnologies.com</a>
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
</pre>
<div class="moz-cite-prefix">On 7/21/2015 2:21 AM, Justin Spencer
wrote:<br>
</div>
<blockquote
cite="mid:CAB+zL_=fgoJVJqK3H=M6XewfewtR+D-+38Smhy0eKq_wd2ywMA@mail.gmail.com"
type="cite">
<div dir="ltr">You can use anything you want as a surrogate, as
long as you have some way of proving it works. In this case,
if you could somehow get real time PV data for a set of sites
that also had actual insolation and then looked at your
results, I think you could derive a typical relationship that
wouldn't lead you too far astray. The problem will come when
there are passing clouds and the PV system is "hunting" all
the time trying to catch up with the changing insolation. I
bet you could find those and apply a bias correction that
could then be used in multiple sites with real time PV data. </div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, Jul 20, 2015 at 10:55 AM,
Chris Yates <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:chris.malcolm.yates@gmail.com"
target="_blank">chris.malcolm.yates@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<p dir="ltr">Ok, so there's no substitute for doing
weather data right.</p>
<p dir="ltr">However, in the absence of such data, could
real-time pv yield be used as a surrogate?</p>
<p dir="ltr">Chris </p>
<p dir="ltr">Sent from my Android device. Please excuse
typos, etc.</p>
<br>
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