A group of researchers from the Australian National University has investigated how to integrate electrical safety test into a reuse qualification of PV modules through a large-scale field testing and has found that around 15% of the decommissioned modules intended for reuse failed to meet legal requirements.
“With the increasing number of fully functional PV panels being decommissioned, reliable and efficient testing is becoming increasingly important before these panels can be deployed in second-life applications. However, the lack of rapid and cost-effective safety testing methods remains a major bottleneck for the reuse of PV modules,” corresponding author Rabin Basnet told pv magazine. “Our work addresses this electrical safety challenge by proposing two potential pathways: silicone coating of the module surface and modification of the standard wet-leakage (WL) testing procedure to enable faster and more practical qualification.”
The first approach involved repairing degraded backsheets with a silicone-based coating to restore electrical insulation, with laboratory tests being conducted on decommissioned crystalline-silicon glass/backsheet modules aged between three and 15 years. The modules were assessed through WL, damp-heat and potential-induced degradation tests.
The second approach modified WL testing to increase the number of modules that can be assessed. Instead of testing modules individually, two modules can be connected in parallel to the same 1,000 V source and the combined leakage current and module area are then assessed against the existing IEC safety threshold. Importantly, the modified procedure does not lower the required safety threshold, but reduces testing time.
The two approaches were tested in a large-scale reuse pilot project in Queensland, Australia, with the research team processing 23,587 decommissioned modules, of which 5,067 were selected for on-site reuse assessment. Following performance and electroluminescence screening, 2,200 modules, or 43%, proceeded to WL testing. Parallel testing enabled these modules to be assessed more efficiently while retaining the IEC safety criteria.
As for the first approach, the scientists assessed whether the coating could provide stable electrical insulation without repeated WL testing and found that, during more than 60 hours of water immersion, the coated module maintained stable wet-leakage resistance. They also ascertained that, although uncoated modules showed greater resistance reductions, they remained above the IEC safety threshold.
This anaylsis also showed that, at temperatures up to 40 C, repaired modules showed no measurable decline in insulation performance, with the coating’s hydrophobic and low-permeability properties limiting moisture ingress and temperature-sensitive leakage. After accelerated damp-heat and PID exposure, all repaired modules continued to pass the electrical safety test.
As for the second approach, the mass-scale pilot testing showed that testing time can be considerably reduced to less than five minutes per module while retaining IEC safety thresholds. Of the 2,200 assessed modules, 1,869 modules (85%) passed the WL test, while 331 (15%) failed, indicating potential insulation defects.
The analysis also showed that about 75% of failed modules were detected within the first 10 seconds of testing, while only around 4% failed between 60 and 120 seconds, suggesting that shorter voltage dwell times could further increase throughput.
“These findings confirm that performance-based screening alone is insufficient to ensure safe second-life deployment,” the academics stated.
Further economis economic assessment suggested that streamlining WL testing is currently the more cost-effective option, at approximately AUD 8–11 ($5.64-7.76) per module approved for reuse. By comparison, silicone-based backsheet repair costs around AUD 25.50–29.50 per module at small scale. However, the cost of coating could fall significantly to about AUD 5–11.50 per module through process optimisation, automation and higher-volume deployment, the researchers concluded.
Their findings are available in the paper “Electrical safety qualifications of decommissioned PV modules for scalable second-life deployment,” published in Solar Energy Materials and Solar Cells.
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