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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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Luke,
<div class=""><br class="">
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<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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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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