Researchers in Austria discovered a wasp nest in the junction box of a 1998 rooftop PV module, illustrating how insects can exploit even sealed electrical components. The affected module showed significant degradation and partial failure, although the overall results confirmed the surprising durability of older PV module designs.
Wasps are known to build nests in a wide variety of sheltered, dry and protected environments. Common nesting sites include outdoor locations such as under eaves and overhangs, in attics or loft spaces, wall cavities accessed through small openings or vents, as well as in sheds, garages or storage boxes.
They can also make nests in birdhouses, hollow trees, under terraces or patio structures, or in dense shrubs and hedges. In addition to natural and semi-natural environments, wasps often occupy man-made structures, including spaces behind building cladding or siding and vents or chimneys. They can also be found in unused machinery or vehicles, where undisturbed and enclosed conditions provide suitable nesting opportunities.
Occasionally, nests are discovered in more unusual or unexpected locations, highlighting the adaptability of wasps in exploiting a wide range of hidden spaces, including junction boxes for PV modules, as recently observed by Gernot Oreski, head of the Aging Behavior of Polymers research group at the Austrian research center Polymer Competence Center Leoben GmbH.
“We made the discovery in a module that was part of a roof system installed in Graz, Austria, in late 1998,” Oreski said. pv magazine. “My former PhD supervisor at the Leoben University of Technology, Reinhold Lang, contacted me because he was interested in the condition and aging status of the modules, and I agreed to conduct the study.”
Manufactured by Shell Solar, a company that is no longer in business, the 100W frameless modules consist of 72 polycrystalline silicon cells, EVA encapsulant, and an aluminum-Tedlar backplate. A range of degradation features and defects were observed, mainly discoloration of the backplate and local burn marks associated with hot spot formation. Only one module showed serious corrosion.
“Last week we went to conduct module characterization at 2nd Cycle, a start-up company in Austria developing an automated test line for PV modules,” Oreski continued. “There we can measure IV curves, electroluminescence (EL) and ultraviolet (UV) fluorescence imaging, and high-resolution images of the module in less than two minutes. In preparation, we dismantled the junction boxes of all the modules and found this old wasp’s nest inside, along with burn marks on the housing and back plate.”
“It is likely that the junction box remained partially operational,” Oreski continued. “One string of the module was probably still functioning, while the other, where the copper ribbon and contacts were completely broken, no longer conducted properly and operated via the bypass diode instead.”
The researcher believes that a similar phenomenon can hardly be observed in PV systems deployed in recent years. “I assume this is less likely because the junction boxes have become smaller and thinner, and most are sealed with a pottant. I’ve seen spider webs and bird nests on modules, but never anything like a wasp nest in the junction box. On the other hand, how many people actually open the junction box?
He also noted that the copper ribbons were encased in a polymer film, which was also burned. “I assume that due to moisture ingress, the copper ribbon has corroded. As a result, we were no longer able to contact the cells in this module and therefore we have no power data or EL images,” he added.
The other modules tested showed a power loss of between 10% and 20%, with some cell breakage detected. “This is further confirmation that PV modules of that era were more robust in their design and more tolerant to degradation effects and failure modes. Now that we have completed the testing, we will continue with the destructive characterization at the material level. We plan to publish the results in a paper and present them at conferences next year,” Oreski said.
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