<html>
<font size=3>for the most part, I have been lurking on this group
because, unlike you designers, our specialty is calibrated models. We've
done hundreds of them, and there are very few doing such.<br>
<br>
<blockquote type=cite class=cite cite>I order up a years worth of
weather<br>
data for the most recent year and convert it to Doe2<br>
format.</blockquote><br>
I don't see how one can do that. At best, you can set the actual
temperature data into a TMY file. But you still have the old solar,
humidity, wind speed etc. Now those data are completely incompatible with
the hourly set of temperatures. Or do you have source for those other
weather data? I don't believe they are being measured anymore.<br><br>
<blockquote type=cite class=cite cite>To calibrate models to reality, you
must also watch out for what's<br>
included in the utility bills. </font></blockquote><br>
Yes, you have to include things like parking lot lights, if
applicable.<br><br>
<br>
<blockquote type=cite class=cite cite><font size=3>And, of course,
there's the difference between how equipment is supposed<br>
to operate and how it actually operates </font></blockquote><br>
As-built and as-operated. That's the whole point of a calibrated model.
The process of calibration often reveals operational opportunities for
further savings. As such, it is a low-cost commissioning tool.<br><br>
<blockquote type=cite class=cite cite><font size=3>Calibrating models
entails either incredibly detailed investigation of<br>
the actual building, </font></blockquote><br>
nonsense. If you have only limited reference data (monthly bills), you
don't need a detailed hourly model. A monthly simulation works fine and
is a whole lot easier.<br><br>
<blockquote type=cite class=cite cite><font size=3>or else application of
the black art of making<br>
informed guesses ("engineering judgment").
</font></blockquote><br>
Any modeling involves informed guesses -- eg) how do you model passive
infiltration? At least with the calibrated model, you have a reality
check.<br><br>
<blockquote type=cite class=cite cite><font size=3> In our
experience, there's a<br>
significant portion of models that just won't calibrate, because
the<br>
actual energy use is too strange and resources to investigate why
are<br>
not infinite.<br>
</font></blockquote><br>
Not so. The monthly bills are a cheap resource and the simulation cost is
minimal. The only ones we have had to reject were because the metering
was at a different level of aggregation.<br><br>
<br>
<blockquote type=cite class=cite cite><font size=3>The real objective of
generating reasonable energy savings estimates,<br>
however, can still be met if the model is overall reasonable.
</font></blockquote><br>
How do you define reasonable? If fact, we have found that using actual
weather, rather than TMY, may be necessary to resolve the model
sufficiently.<br><br>
<blockquote type=cite class=cite cite><font size=3> It's the<br>
delta in energy use attributable to the efficiency measures of
interests<br>
that matter, not necessarily tracking down all the unusual quirks
of<br>
utility metering and billing systems. </font></blockquote><br>
Yeah, but if you don't have the building defined, can you be sure of the
calculated delta? At least if you start with a calibrated model, then
move off it incrementally, you have some confidence that the deltas are
reasonable.<br><br>
<br>
<blockquote type=cite class=cite cite><font size=3>Using a whole building
simulation can be a big<br>
improvement on that practice.</font></blockquote><br>
Absolutely<br><br>
<x-sigsep><p></x-sigsep>
<font size=3>====================<br>
David Robison<br>
Stellar Processes<br>
1033 SW Yamhill Suite 405<br>
Portland, OR 97205<br>
(503) 827-8336<br>
<a href="http://www.ezsim.com/" eudora="autourl">www.ezsim.com</a></font></html>