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

[boB at midnitesolar.com]

Oooo...  Or maybe a module or more are shorted and being bypassed ?

A FLIR can sometimes come in handy to look at the entire array and of course
detect bad/hot connections.

  But a shorted module will be almost as hot as a working module at MPP 
voltage.

boB


On 6/1/2015 11:28 AM, boB at midnitesolar.com wrote:
>
>
> Partial shading will also reduce the MPP voltage and to a much smaller 
> extent, the Voc.
>
> I don't suppose there are some new trees or something at the site ?
>
> Jarmo, I like your presentation.
>
> boB
>
>
> On 6/1/2015 11:21 AM, Starlight Solar Power Systems wrote:
>> Luke,
>>
>> For reference, we sold/installed many hundreds of Uni-Solar products 
>> since 2002. I have never seen anywhere near that much Voc loss.
>>
>> 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.
>>
>> 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.
>>
>>
>> Larry Crutcher
>>
>>
>>
>> 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 Professional™: Certification #031409-25
>> NABCEP Certified Solar Heating Installer™: Certification #ST032611-03
>> CoSEIA Certified PV Installer
>>
>> Solar Gain Services, LLC
>> PO Box 531
>> Monte Vista, CO. 81144
>> SGSRenewables at Gmail.com <mailto:SGSRenewables at Gmail.com>
>> 719.588.3044
>> www.sgsrenewables.com <x-msg://40/www.sgsrenewables.com>
>>
>>
>

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