<div dir="ltr">Drake<div><br></div><div>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!</div>
<div><br></div><div>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) . </div>
<div><br></div><div>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? </div>
<div><br></div><div>see <a href="http://files.sma.de/dl/7418/PID-TI-UEN113410.pdf">http://files.sma.de/dl/7418/PID-TI-UEN113410.pdf</a></div><div>and <a href="http://files.sma.de/dl/7418/PID-PVOBox-TI-en-10.pdf">http://files.sma.de/dl/7418/PID-PVOBox-TI-en-10.pdf</a></div>
<div><br></div><div>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!</div><div><br></div><div>
Bill</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Dec 27, 2013 at 8:39 AM, Drake <span dir="ltr"><<a href="mailto:drake.chamberlin@redwoodalliance.org" target="_blank">drake.chamberlin@redwoodalliance.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
Hello Wrenches,<br><br>
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.
<br><br>
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?<br><br>
<br>
Thanks,<br><br>
<br>
Drake<br><br>
<br>
<a name="14334ed5236f4e9c__MailAutoSig"></a>Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br>
<a href="tel:740-448-7328" value="+17404487328" target="_blank">740-448-7328</a><br>
</i><a href="http://athens-electric.com/" target="_blank">http://athens-electric.com/</a>
<br><br>
</div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr"><div>Bill Hoffer <br></div>161 SE Fourth Ave<br><div>P.O. Box 1823<br>White Salmon, WA 98672<br><a href="mailto:bhoffer@sunergyengineeringservices.com" target="_blank">sunengser@gmail.com</a><br>
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