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<p>As the co-author of the Zhang-Huang Model, I can say that the
information in your first sentence is garbled. The ZHM calculates
the global horizontal radiation based on various climatic
parameters, i.e., cloud cover, temperature change over 3 hours,
wind speed, etc. It is NOT used to derive the direct/diffuse
split, so I don't understand how that has gotten into the
EnergyPlus documentation. I have mentioned this misunderstanding
to members of the EnergyPlus Team five years ago or so, but it
seems it still persists.<br>
</p>
<p>A week or so ago I read that the Perez Model is used only for
hourly data, which raises the question how the direct/diffuse
split is done when there's subhourly GHI data? <br>
</p>
<p>Lastly, I would also add a caution that all-sky modeling, i.e.,
solar radiation under non-clear conditions, is still an evolving
topic, and that just because the results didn't make EnergyPlus
crash it doesn't necessarily mean that they're right.</p>
<p>Joe<br>
</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 11/11/2016 12:54 PM, Lukas Hovee via
Bldg-sim wrote:<br>
</div>
<blockquote
cite="mid:5aea3149-95de-79ef-a83d-a73f636c28bf@360-analytics.com"
type="cite">
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<font face="Calibri">FYI - <br>
<br>
The EnergyPlus Weather File Converter packaged with the Energy
Plus download includes two methods for performing the
direct/diffuse split: Zhang-Huang and the Perez Split. See the
Energy Plus Auxiliary Programs for more detail:<br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://bigladdersoftware.com/epx/docs/8-6/auxiliary-programs/definitions-file-custom-file-processing.html#custom-file-processing---solar-radiation-value-calculation">http://bigladdersoftware.com/epx/docs/8-6/auxiliary-programs/definitions-file-custom-file-processing.html#custom-file-processing---solar-radiation-value-calculation</a><br>
<br>
I've recently successfully used this tool to generate an EPW
given only hourly global horizontal (plus the necessary
non-solar measurements). One bug I would mention - for the
'Custom File Processing' option, it only seems to accept space
delimited files - even if you specify otherwise in the
Definitions file...<br>
</font><br>
- Luke <br>
<div class="moz-signature">
<p>--<br>
Lukas Hovee, P.E.</p>
<strong>360 Analytics</strong><br>
Building Energy Analysis Consultants<br>
<font size="2.5">mail: 710 2nd Ave, Suite 925, Seattle, WA
98104</font><br>
<font size="2.5">office: 206.557.4732 x 202</font><br>
<font size="2.5">cell: 206.909.0106</font><br>
<font size="2.5">web: <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="http://www.360-Analytics.com">www.360-Analytics.com</a></font><br>
<strong>** We've moved! Please note our new address above.</strong><br>
<br>
</div>
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