<html>
<body>
I will use a lot of copper to save 1%. 6% is significant.<br><br>
For an off grid system, the angle is a major issue. <br><br>
At 12:35 PM 2/21/2011, you wrote:<br>
<blockquote type=cite class=cite cite="">Jim,<br>
Obviously, your latitude will make a big difference. The further north
you go the wider the summer to winter sun angle. Also, I'd want to know
if that data was taken using just I/V curves or through a controller
which had MPPT capabilities. In a real world situation with MPPT, I'm
guessing that matching the array tilt to the sun angle would make more
than a 6% difference at 40°+ latitudes.<br>
Besides, what's wrong with an extra 6%??<br>
Cheers, bob-O<br><br>
On Feb 19, 2011, at 8:03 PM, North Texas Renewable Energy Inc
wrote:<br><br>
At least that's the conclusion of Gottfried Wilhelm Leibniz. <br>
"The largest difference of the [PV] plant yield was less than 6% for
tilt angles between 0° and 70°."<br>
This begs the question, where did the notion that tilt to latitude is
critical come from. Surely NREL or someone else has tested this concept
before. Anyway if N-S angle energy production loss is only 6% to +/-35°
then E-W should be too, right? But it's not. <br>
Here's why. If you measured irradiance at 10°-70° only at noon over 12
months, the air mass would at its minimum during the entire test and so
irradiance deviation would be too. AM would not be constant at +/- 35°
E-W which has been verified by NREL and others for a long time, AM
increases the further from solar noon the sun gets. <br>
But if the Earths tilt is 23.5 degrees and Gottfried measured to 35
degrees, the difference is 11.5 degrees at summer and winter solstice.
And if your array angle is +/- 11.5 deg from true south, rule of thumb is
that irradiance losses are minimal. Maybe only 6% or so. <br>
This puts the significance of array tilt in a whole new light. Pun
intended... <br>
Of course there is a fee to download the entire document but the abstract
is here <br>
<b><a href="http://tinyurl.com/4zf2syk">http://tinyurl.com/4zf2syk</a><br>
</b>
<a href="http://www.scopus.com/record/display.url?eid=2-s2.0-78951495350&origin=inward&txGid=kX6CkwoH_w_VL01NbmaciIC%3a2" eudora="autourl">
http://www.scopus.com/record/display.url?eid=2-s2.0-78951495350&origin=inward&txGid=kX6CkwoH_w_VL01NbmaciIC%3a2</a>
<br>
<br>
<br>
<font size=2><b>Jim Duncan<br>
North Texas Renewable Energy<br>
</b></font><br>
_______________________________________________<br>
List sponsored by Home Power magazine<br><br>
List Address: RE-wrenches@lists.re-wrenches.org<br><br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" eudora="autourl">
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a>
<br><br>
List-Archive:
<a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" eudora="autourl">
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br>
<br>
List rules & etiquette:<br>
<a href="http://www.re-wrenches.org/etiquette.htm" eudora="autourl">
www.re-wrenches.org/etiquette.htm</a><br><br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org/" eudora="autourl">
www.members.re-wrenches.org</a></blockquote>
<x-sigsep><p></x-sigsep>
<font color="#0000FF">Drake
Chamberlin<x-tab> </x-tab>
<br>
Athens Electric<br>
OH License
44810<x-tab> </x-tab><br>
CO license 3773<br>
NABCEP Certified PV<br>
</font></body>
</html>