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<font face="Times New Roman, Times, serif">Wrenches,<br>
<br>
I am talking with a potential client about a roof mounted PV
array. The client has a reasonably large south facing roof, but it
is broken up by a large (18' W x 16' H) shed dormer. The roof is
10:12 and the dormer is </font>6:12. I designed a layout that
gave the dormer some room to avoid shading. The client was
disappointed by how much wattage I could get on his roof. I pointed
out that installing modules in the shade of the dormer was a bad
idea.<br>
<br>
<font face="Times New Roman, Times, serif">He is also talking to
another installer. </font>The other installer proposed installing
part of the array on the 10:12 roof and part on the 6:12 dormer. The
client had already asked me about that and I gave him a rudimentary
explanation of maximum power point tracking and the inefficiency of
such an arrangement. He asked them about that and their guy said "No
big deal." He is still considering the two-angle scenario.<br>
<br>
So, how much efficiency will he lose by going with two angles? It
seems like the ultimate MPPT design error to me, but I don't have a
number for him to make my case. I suppose it all comes down to cents
per delivered kWh in the end, but two different roof angles seems
the the wrong way to go. I'd like to be able to give him a
definitive idea of what he would be sacrificing with that scenario.<br>
<br>
Side note: The other installer is using the new Sunpower E20
modules. They seem to be available only from the manufacturer.
Anybody have a source? Has anybody used them yet? Do they live up to
the hype?<br>
<br>
Many thanks,<br>
<br>
Hilton<br>
<pre class="moz-signature" cols="72">--
Hilton Dier III
Renewable Energy Design
Partner, Solar Gain LLC
453 East Hill Rd.
Middlesex, VT 05602
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