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.chamber...@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@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 > suneng...@gmail.com <bhof...@sunergyengineeringservices.com> > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@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@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