[RE-wrenches] Voltage Degradation with Uni-Solar laminate

Dana dana at solarwork.com
Sun May 31 11:42:13 PDT 2015


I have a new client in ID that has the same product. The 48 volt system has
a relay style era charge controller that we will upgrade this summer. He has
no issues achieving equalization voltages PV direct without the generator.
For a product that had a lot of press in the early days this is only the 2nd
Unisolar system I have seen since Jan of '88. 

 

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Dana Orzel 

Great Solar Works, Inc -  NABCEP # 051112-136

E - dana at solarwork.com  - Web - solarwork.com 

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"Responsible Technologies for Responsible People since 1988"  

P Please consider the environment before printing this email.

 

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Ray Walters
Sent: Sunday, May 31, 2015 12:31 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Voltage Degradation with Uni-Solar laminate

 

Yes, amorphous modules degrade faster then crystalline cells. 15 years will
really start catching up with you, that's why we always tried to stick to
monocrystalline when we could. 
I think your best option for now is to rewire the array for much higher
voltage.  Even your current voltage problem aside, the system will run more
efficiently at higher voltage:  Less current = less voltage drop.  I would
probably just jump the 4 module sets in series in the combiner box to 8 in
series.  Should be a quick fix, and really show an improvement.  I've seen
this same issue with low voltage polys and undersized wiring.  Usually the
MPP controllers like some room to play with; as soon as the MPP voltage gets
close to or less than battery voltage, the current drops off substantially.








R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer, 
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 5/31/2015 11:55 AM, Luke Christy wrote:

Hello Off-Grid Wrenches,
 
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. 
 
This system has an array of 48x Uni-Solar PVL-68 laminate modules applied
directly to standing-seam metal roofing. 
 
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! 
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.
 
By removing the loads I was able to get an open-circuit voltage of 71V, but
that still seems pretty low. 
 
Has anyone else experienced a voltage degradation issue with the Uni-Solar
laminate? What was the expected annual voltage degradation for this
technology? 
 
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. 
 
Any experiences or opinions are appreciated.
Thanks in advance. 
 
-Luke
 
 
Luke Christy
 
NABCEP Certified PV Installation ProfessionalT: Certification #031409-25 
NABCEP Certified Solar Heating InstallerT: Certification #ST032611-03       
CoSEIA Certified PV Installer 
 
Solar Gain Services, LLC
PO Box 531
Monte Vista, CO. 81144
SGSRenewables at Gmail.com
719.588.3044
www.sgsrenewables.com
 
   
 
 
 
 
 
 
 
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