[RE-wrenches] Unisolar US64 problem

[Dana]

If the modules test out to spec., Are there any mystery
junction boxes where there may be a corroded connection
[i.e. - split bolt or butt splice] and are all the
connections tight? 

Seen this on several occasions.

 

Thanks,  Dana Orzel

 

Great Solar Works, Inc

E - dana at solarwork.com

V - 970.626.5253

F - 970.626.4140

C - 970.209.4076

web - www.solarwork.com

Responsible Technologies for Responsible People since 1988"

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf
Of Allan Sindelar
Sent: Friday, June 25, 2010 12:50 PM
To: RE-wrenches
Subject: [RE-wrenches] Unisolar US64 problem

 

We have an off-grid customer whose PV arrays seem to be
under performing and we're not sure why.  The customer has
16 Unisolar US64 modules, which have a peak output of 3.88
amps, but which were only putting out from 2 to 2.4 amps
each.  He has a C40 charge controller, so they were
operating off the peak of the I-V curve (they were operating
at 13.6 volts each at the time of the system inspection,
instead of the peak, which is up around 17 volts), but still
the amps that they were putting out were lower than they
should be.  He used to get 30+ amps (at 24 volts) from his
array, but now he's only getting a little more than 20 amps
(611 watts from a 1024 watt array is what my tech saw when
he was there a week ago).  The C40 was still in its bulk
cycle, not having reached the absorption set-point.  The
sunshine was strong (there was no shading all day), there
was no haze in the sky, it was solar noon (1pm MDT), in the
mid to high 70's with a breeze, the arrays are on tilt-up
racks, and there was no more than a little dust on the
modules.  His arrays are at a year round setting
(~latitude), so not optimal for this time of year, but not
that far off.  Half of the modules are 12 years old and half
are 10 years old, but it was only last year that he had 30+
amps coming in, so they couldn't have deteriorated/aged that
much in one year.

Since there is no combiner box (we didn't design or install
this system), each pair (string) was checked with a clamp-on
meter and was putting out only 2 to 2.4 amps.  When the C40
was bypassed, there was no increase in current coming in, so
the controller doesn't appear to be at fault.

The customer's measurement of the performance of his system
is the LED on the C40.  He has a meter face on his C40, but
he mostly just looks at the LED.  He says that the LED used
to go solid green by noon, and now he doesn't get more than
two or three blinks all day.

Any idea why all his modules might be under performing?

Thanks
Russell Mueller
Positive Energy
211-M Cruz Alta Rd.
Taos, NM 87571
575-737-9553

No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.830 / Virus Database: 271.1.1/2961 - Release
Date: 06/25/10 00:35:00

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20100625/27a2cd56/attachment-0004.html>