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Hi Eli, Keith, ...<br>
Finally got some descent sun and a little time to do the further
testing on the effect of power line shadows on PV array output.<br>
<br>
The new results are here:<br>
<a class="moz-txt-link-freetext" href="http://www.builditsolar.com/Experimental/PVShading/PVShading.htm">http://www.builditsolar.com/Experimental/PVShading/PVShading.htm</a><br>
<br>
It looks to me like for real world wire shadows from wires 20+ ft
away that the effect might be small to none.<br>
<br>
Would appreciate any comments on this, or things that might be wrong
in the test.<br>
<br>
Gary<br>
<br>
<br>
On 12:59 PM, gdreysa wrote:
<blockquote cite="mid:%3C4D9C6F4C.6010607@gmail.com%3E" type="cite">
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Hi Eli,<br>
I'd agree with Keith that some caution is in order here.<br>
<br>
This is a picture of my Enphase PV array with some modest shading:<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.builditsolar.com/Projects/PV/EnphasePV/Shading.htm">http://www.builditsolar.com/Projects/PV/EnphasePV/Shading.htm</a><br>
<br>
You can see from the real time output plot that even the panel
with just a line across it is very much effected.<br>
The shadow is wider than a power line would cast, and maybe the
effect would diminish as the shadow gets narrower, but I'd be
careful.<br>
<br>
If I think about it later today and the weather cooperates, I'll
set up narrower shadow and let you know how that comes out.<br>
<br>
The micro inverters are good in that a shadow across one module
only effects the output of that one module and not the whole
string, but a wire shadow that goes across several modules could
still have a serious effect.<br>
<br>
Gary<br>
<br>
<br>
On 12:59 PM, Keith Winston wrote:
<blockquote
cite="mid:%3CBANLkTikWHTbcWvMu9ZoG2i53g00zenTYfQ@mail.gmail.com%3E"
type="cite">I'm not quite sure what you mean by "smaller than
the sun's disc"... larger power lines can cast distinct shadows.
If those align with an axis of the modules, then they may shade
an entire row of cells in a module, overcoming the ability of
the bypass diodes to "bypass" the shaded cells (most modules
are, I believe, still bypassed on a cell-by-cell basis, and are
wired in series along one of their axis). So I'll stand by my
earlier comment that a power line could very well create
significant shading. But I agree with the microinverter
suggestion.<br>
<br>
Keith<br>
<br>
<br>
<div class="gmail_quote">On Mon, Apr 4, 2011 at 11:22 AM, Gordon
Howell -- Howell Mayhew Engineering <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:ghowell@hme.ca">ghowell@hme.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;"> Thanks for your question Eli:<br>
<br>
It doesn't appear that the electrical lines would be a
significant issue. They are likely smaller than the sun's
disc.<br>
<br>
If you use Enphase module-inverters (one inverter for each
PV module) then any shaded module wouldn't affect the PV
array's performance, because each PV string is a PV module.<br>
<br>
To clarify: the industry term that is an
internationally-recognised standard for PV modules is
"module", not collector, not panel. See attached file for
pictoral description.<br>
</blockquote>
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