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Oooo... Or maybe a module or more are shorted and being bypassed
?<br>
<br>
A FLIR can sometimes come in handy to look at the entire array and
of course<br>
detect bad/hot connections.<br>
<br>
But a shorted module will be almost as hot as a working module at
MPP voltage.<br>
<br>
boB<br>
<br>
<br>
On 6/1/2015 11:28 AM, <a class="moz-txt-link-abbreviated" href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a> wrote:<br>
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<br>
Partial shading will also reduce the MPP voltage and to a much
smaller extent, the Voc.<br>
<br>
I don't suppose there are some new trees or something at the
site ?<br>
<br>
Jarmo, I like your presentation.<br>
<br>
boB<br>
<br>
<br>
On 6/1/2015 11:21 AM, Starlight Solar Power Systems wrote:<br>
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cite="mid:CFBA85A9-59A2-4458-A270-82AEC61DBB89@starlightsolar.com"
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Luke,
<div class=""><br class="">
</div>
<div class="">For reference, we sold/installed many hundreds of
Uni-Solar products since 2002. I have never seen anywhere near
that much Voc loss. </div>
<div class=""><br class="">
</div>
<div class="">Since the PVL-68 has an open circuit of 23.1V
(92.4V) but you only see 14.2V (71V), a loss of 25%, I do not
believe degradation is the culprit even at 15 years. The rated
degradation is 0.73% per year. That should put you at 82.3
Voc. But, Uni-Solar consistantly outputs at least 10% more
than rated power, even with age it should be higher than 82
volts.</div>
<div class=""><br class="">
</div>
<div class="">Proper Uni-Solar installation required 2 screws
into the roof up near the top. A misplaced screw and time or
an open seam may be causing a ground fault, pulling down the
voltage of the array. Start by using a Megger at the combiner
to check for leakage. No one likes crawling in a hot attic but
I think you may need to.
<div class=""><br class="">
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class="">
Larry Crutcher<br class="">
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<div class=""> <br class="">
<br class="">
<tt class=""><font class="" size="2">Hello Off-Grid
Wrenches,<br class="">
<br class="">
I recently made a periodic maintenance visit to a
residential off-grid system I take care of here in
Southern CO, and discovered an interesting problem.
<br class="">
<br class="">
This system has an array of 48x Uni-Solar PVL-68
laminate modules applied directly to standing-seam
metal roofing. <br class="">
<br class="">
The data logging on the controller (Outback MX-60)
indicated that the system was having trouble
completing a charge cycle and going to float.
Initially I assumed was due to heavy electrical use
by the occupants (renters). After a little checking,
I noticed that the module string voltage was only
about 0.5V above the battery voltage! <br class="">
This was a cool late morning, with full sun, and the
array was charging almost 2kW at 54.5V. The module
strings were running at 55V. I've noticed the module
voltage being lower than I'd like before, but it has
never been this low. I suspect this is the real
reason the system hasn't been able to complete a
charge cycle.<br class="">
<br class="">
By removing the loads I was able to get an
open-circuit voltage of 71V, but that still seems
pretty low. <br class="">
<br class="">
Has anyone else experienced a voltage degradation
issue with the Uni-Solar laminate? What was the
expected annual voltage degradation for this
technology? <br class="">
<br class="">
These modules do have some age on them. The system
was installed about 15 years ago (by a competent
installer who is now retired). The system was
installed before MPPT controllers were common, so I
assume the modules are wired in strings of 4 for 48V
nominal. <br class="">
<br class="">
Any experiences or opinions are appreciated.<br
class="">
Thanks in advance. <br class="">
<br class="">
-Luke<br class="">
<br class="">
<br class="">
Luke Christy<br class="">
<br class="">
NABCEP Certified PV Installation Professional™:
Certification #031409-25 <br class="">
NABCEP Certified Solar Heating Installer™:
Certification #ST032611-03 <br class="">
CoSEIA Certified PV Installer <br class="">
<br class="">
Solar Gain Services, LLC<br class="">
PO Box 531<br class="">
Monte Vista, CO. 81144<br class="">
<a moz-do-not-send="true"
href="mailto:SGSRenewables@Gmail.com" class="">SGSRenewables@Gmail.com</a><br
class="">
719.588.3044<br class="">
</font></tt><a moz-do-not-send="true"
href="x-msg://40/www.sgsrenewables.com" class=""><tt
class=""><font class="" size="2">www.sgsrenewables.com</font></tt></a><tt
class=""><font class="" size="2"><br class="">
<br class="">
</font></tt><br>
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