[RE-wrenches] PID

[Peter Parrish]

Has anyone any direct experience with the SMA PV Offset Box? Which inverter
did you use it with and with which PV modules? Any help would be appreciated
as we may have problems in the field.

Has SunPower issued anything regarding their product line as to allowing
negative grounding. It would be great to be able to look at a specific
SunPower PV module + Serial Number and figure out whether it can operate
with negative grounding w/o PID.

Peter T. Parrish, Ph.D. President
SolarGnosis
1107 Fair Oaks Ave.
South Pasadena, CA 91107
Ph. (323) 839-6108, Fax. (323) 258-8827


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
drake.chamberlin at redwoodalliance.org
Sent: Friday, December 27, 2013 3:05 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] PID

Bill,

Thank you. That is exactly the data needed.

Drake


> Drake
>
> PID is caused by many factors, the capacitive nature of a solar panel 
> and materials ( cheaper, thinner encapsulants and backsheets and cell 
> surface treatments to get more efficiency to name a few).  The new 
> marketing battle cry for module manufacturers material vendors is PID 
> resistant materials, but we all have to take marketing claims with a 
> grain of salt until we get independent data to show that it is true!
>
> A simplified explanation of PID is the build up of charged ions in a 
> module that cause a significant reduction in voltage output, dominated 
> by a complex interaction between materials within the module.  With a 
> negative grounded system there is a path to bleed off this charge .  
> The nature of SunPowers module when negative grounding was used 
> initially was the charge build up was not bleed off the negative side, 
> but needed to bleed off the
> positive side.   This resulted in significantly reduced output, which is
> irreversible after a period of time.  These were the first cases of 
> PID in the US.  That is why they solved it by specifying positive 
> grounding to bleed off this charge properly.  A transformerless 
> inverter does not ( and can not with fatal results) have a bond 
> between negative and ground, so it cannot bleed off this excess 
> charge.  There may have already been PID, but we never noticed with 
> transformer based inverters and 600 VDC systems.  We are seeing it 
> predominately in Europe now where 1000VDC transformerless inverters are
more common, combined with cheaper modules ( ie materials) .
>
> I am surprised that SMA knows nothing about this since I understand 
> they have a field fix  to add a switch, controlled by the inverter 
> that allows a bond connection between PV negative and ground when the 
> inverter shuts down over night to bleed off this excess charge and the 
> switch is opened at sunrise by the inverter before it makes it 's 
> checks ( ground - negative isolation and megging of the array for 
> faults before startup).  Maybe this is only available so far in 
> Europe?
>
> see http://files.sma.de/dl/7418/PID-TI-UEN113410.pdf
> and http://files.sma.de/dl/7418/PID-PVOBox-TI-en-10.pdf
>
> It can be a serious problem once it has reached an irreversible point!
>  Some modules seem to be more susceptible to this issue. but it is not 
> easy to find which ones to avoid!
>
> Bill
>
>
> On Fri, Dec 27, 2013 at 8:39 AM, Drake 
> <drake.chamberlin at redwoodalliance.org
>> wrote:
>
>>  Hello Wrenches,
>>
>> Attached is an article from Home Power that came in my email. It says 
>> module degradation is increased by PID (Potential Induced 
>> Degradation) by the use of transformerless inverters.  It says power 
>> degradation can occur over days or weeks and cause a 10% to 60% loss 
>> of efficiency.
>>
>> I called Power One and SMA and their tech support people have not had 
>> any reports of problems. Is this something we need to be concerned 
>> about?
>>
>>
>> Thanks,
>>
>>
>> Drake
>>
>>
>> Drake Chamberlin
>>
>>
>>
>>
>>
>> *Athens Electric LLC OH License 44810 CO License 3773 NABCEP 
>> Certified Solar PV 740-448-7328 <740-448-7328> 
>> *http://athens-electric.com/
>>
>>
>> _______________________________________________
>> List sponsored by Home Power magazine
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Change email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> List-Archive:
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>>
>> Check out participant bios:
>> www.members.re-wrenches.org
>>
>>
>>
>
>
> --
> Bill Hoffer
> 161 SE Fourth Ave
> P.O. Box 1823
> White Salmon, WA 98672
> sunengser at gmail.com <bhoffer at sunergyengineeringservices.com>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Change email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive:
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>


_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Change email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org