Module prices in the index have been corrected upwards, and there is no relief in sight. Even more important than prices, however, is the issue of availability. The situation continues to deteriorate. While delivery times have so far been within reasonable limits, we are now slowly but surely moving toward a new bottleneck. But it is not so much the main components of the modules, such as solar cells or glass, that appear to be the cause of future problems; rather, it is the smaller components – junction boxes, plugs, encapsulant material, and so forth. Without these, no panels can be built. The overall disruption means we can all expect delays and interruptions in the near future. For modules in the field, meanwhile, there is also plenty to worry about.
Backsheet degradation
The extent of future critical problems and error patterns is not always recognized in time, because inherent product defects are often subtle and appear, if at all, initially as a purely visual defect. Only predictive and recurring audits along with proactive measures can identify serious impending issues in a timely manner and reduce the extent of the consequences.
Visual inspection is very often underestimated as a way to identify the causes of failures at plant or module level. Incidentally, a visual inspection is also the first step in the testing of fixed electrical systems and equipment, as specified in industry standard DIN VDE 0105-100. When optimally prepared, visual inspection remains a cost-efficient and very effective way for plant operators to identify performance or other issues.
A comprehensive fault catalog, including the module position and serial number should be created to support a possible warranty claim. In many cases, this, in combination with on-site measurement is worthwhile to make more precise statements about the causes of defects. Progressive degradation, such as cracks in backsheets, is a good example of that which all too often presents operators with major challenges. By now the word is out about the problem of brittle and cracked backsheets. But what does this mean for the operator? Should they just wait and hope that their modules are not affected? Or is it possible to check and detect at an early stage whether the installed modules of one’s own portfolio are affected by a backsheet problem? Shouldn’t the manufacturer in question issue a recall? After all, doesn’t a delay pose a danger?
Unfortunately, the facts are not so straightforward, and many manufacturers do not yet have a clear answer. But as is often the case in life, proactive and timely action can save a lot of trouble in the future. It is important to keep in mind that the backsheet problem is a gradual process and if you take a closer look, you can evaluate early whether the modules in question are affected. An operator with early awareness that backsheets will crack in the future has ample time to file a warranty claim. In most cases, the PV system can then continue to produce power while the warranty case is documented, discussed and adjudicated.
The backsheet problem does not affect all modules, but mainly polyamide-based AAA backsheets of modules installed mainly in the boom years from 2010 to 2014. According to our estimates, however, this is at least 20 GW – well over 80 million modules. But it is often not easy to trace which modules will be affected. Operators may know what type of module is installed, but only in very few cases is there also a full bill of materials (BoM).
A screening of the modules verifies whether there is any chalking of the backsheet. Only then is it clear whether cracks and corrosion inside the module may occur in the foreseeable future, depending on weather conditions such as UV radiation and moisture. The module should only be touched if there are no cracks, even microcracks, in the backsheet. Cracks drastically reduce the insulation resistance, especially when wet, and touching the module can cause a ground fault or even an electric shock in the worst-case scenario.
Here, the danger is imminent, and it is the operator’s responsibility. Solar panels with cracked backsheets lose their designated “class 2” protection and could theoretically only be used as electrical equipment with protection “class 0” in electrical operating environments. This means that only qualified electricians may enter the photovoltaic system. It is therefore difficult for the operator to allow groundskeepers, shepherds, module cleaners or other non-electrical specialists onto the premises.
To keep it simple, backsheet chalking is a reliable early indicator of a serious product defect and should not be dismissed. Manufacturers have already started to respond and have published product warnings. In our view, there is currently no certified repair process and it is usually not clear who guarantees that repair will be successful.
However, periodic screenings allow early detection of module changes. If backsheet problems are detected and documented, it makes sense to file a warranty claim with the module manufacturer as soon as possible and, in our experience, there is a good chance of success. The manufacturer is then forced to either come up with a repair solution that restores operational safety or to financially underwrite the replacement of the defective modules. Waiting is certainly the wrong strategy for operators.
About the authors
Martin Schachinger has been active in renewable energy for more than 20 years. In 2004, he founded the online trading platform pvXchange.com, where wholesalers, installers, and service companies can purchase standard components, solar modules, and inverters that are no longer manufactured but are still urgently needed to repair defective PV systems.
Falko Krause is a co-founder and the CTO of GME clean power AG. As a TÜV-certified appraiser, Krause is active as a provider of technical advice, system planning, and quality assessments. GME clean power AG focuses on optimizing existing systems and developing ecologically and economically sensible PV projects.
The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.
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