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A little more musing here...and I'm looking for others' opinions on
this theoretical piece.<br>
<br>
If you have two unmatched strings, won't the string with the larger
Imp define the MPP of the inverter? <br>
<br>
If so, I would expect that the weaker string would be forced to
operate at the Imp of the stronger string.<br>
<br>
If the stronger string operates at a higher Vmp, it will pull the
weaker string's operating voltage above its own MPP, which could
pull the current down substantially as voltage moved from Vmp toward
Voc.<br>
<br>
Conversely, if the stronger string operates at a lower Vmp, it will
pull the weaker string's operating voltage back toward its own MPP,
which would maintain approximately the same current at a slightly
lower voltage. This would reduce output slightly, but not nearly as
much as in the other direction.<br>
<br>
Does this make sense? And does real-world experience bear this out?<br>
<br>
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<p class="MsoNormal" style=""><span class="il"><b style="">Allan</b></span><b
style=""> Sindelar</b><span style="font-size: 10pt;"><br>
<a href="mailto:Allan@positiveenergysolar.com"
target="_blank"><span class="il">Allan</span>@positiveenergysolar.com</a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b style="">Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b style="">505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/"
target="_blank">www.positiveenergysolar.com</a></span></p>
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<br>
On 1/15/2011 11:50 AM, William Miller wrote:
<blockquote
cite="mid:6.0.1.1.2.20110115104240.032e9918@millersolar.com"
type="cite">
Friends:<br>
<br>
I have a client with a Xantrex GT2.8 inverter. Feeding it are 8
Solar World SW175 modules. This is half the modules that this
inverter can handle. The client wants to realize the full
potential
of this inverter. Adding 8 additional SW175 modules would be
ideal,
but they are no longer manufactured.<br>
<br>
I need to find a group of modules to match the 175s. I am
contemplating 9 SW240s. The specifications for this match up are
below. I imagine the IV curves are similar for these two modules
as
they are the same chemistry and the same manufacturer.<br>
<br>
<font size="3"><x-tab> </x-tab>8-SW175<x-tab> </x-tab>9-SW240<br>
Voc<x-tab> </x-tab>403<x-tab> </x-tab><x-tab> </x-tab>382<br>
Vmp<x-tab> </x-tab>283<x-tab> </x-tab><x-tab> </x-tab>275<br>
Imp<x-tab> </x-tab>4.95<x-tab> </x-tab><x-tab> </x-tab>7.87<br>
Pcsi<x-tab> </x-tab>1252<x-tab> </x-tab><x-tab> </x-tab>1715<br>
Ptotal<x-tab> </x-tab>2.967<br>
<br>
Might this match be close enough? I know this over-powers the
inverter slightly. I imagine that the Xantrex will self
regulate
this very rare over wattage condition.<br>
<br>
Comments?<br>
<br>
William Miller<br>
<br>
<br>
<br>
<x-sigsep></x-sigsep></font>
<p>
<font size="3"><u>Please note new e-mail address and domain:<br>
<br>
</u>William Miller <br>
Miller Solar<br>
Voice :805-438-5600<br>
email: <a class="moz-txt-link-abbreviated" href="mailto:william@millersolar.com">william@millersolar.com</a><br>
<a moz-do-not-send="true" href="http://millersolar.com/"
eudora="autourl">http://millersolar.com<br>
</a>License No. C-10-773985<br>
</font></p>
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