Researchers at the Federal University of Santa Catarina (UFSC) in Brazil have conducted a 2-year testing on second-life polycrystalline solar modules deployed at their campus and have found that they can still ensure “stable” behavior, with performance consistent with annual degradation rates of up to 0.44%.
“Despite the many aspects making it a difficult sell, circular economy and sustainability issues might work in favor of second-life photovoltaic modules, due to the huge amount of panles that will become available with the exponential growth this technology is undergoing for nearly a decade,” the research’s lead author, Ricardo Rüther, told pv magazine.
“Despite the clear case for second-life PV regarding technical issues, sustainability and circular economy aspects, it is difficult to make the case for it on the grounds of economics, because state-of-the-art silicon PV keeps coming down in price.” he went on to say. “It is currently hard to believe someone would go for a second-life Si PV module at a price at least 50% below current market prices for brand new, state-of-the-art, Si PV modules. Moreover, warranty times are a bit murky in this market.”
For the experiment, the research team used second-life multicrystalline PV modules recovered from a decommissioned off-grid system on Ratones Island, Brazil, originally installed in to replace diesel generation. The system consisted of 76 modules totaling 4.7 kW and operated for over 22 years before being repowered in 2022 with higher-efficiency technology.
Following decommissioning, the modules were transported to the PV laboratory of UFSC for detailed evaluation under similar coastal environmental conditions. In 2023, all modules underwent visual, electrical, and safety assessments, leading to the approval of 68% for second-life use.
Experimental setup
The approved modules were then tested in two configurations: a module-level outdoor setup and a system-level grid-connected installation. At the module level, two representative modules were installed on a single-axis tracker with continuous IV curve measurements at one-minute resolution.
This setup enabled detailed monitoring of electrical parameters such as maximum power, current, voltage, and degradation behavior under real operating conditions. High-precision sensors measured irradiance and temperature, allowing correction of results to standard test conditions.
Strict data filtering ensured high-quality datasets, resulting in 49 valid clear-sky days over a two-year monitoring period.
Electroluminescence imaging was conducted both after decommissioning and after two years of outdoor exposure to detect defects and track degradation. This combined electrical and imaging approach provided insights into the long-term stability of reused modules.
System performance was evaluated using the performance ratio (PR), including weather-corrected PR to account for temperature variations.
Electrical and environmental data were collected and processed with filtering criteria to ensure reliability, resulting in 128 valid days of analysis.
Additional field tests, including IV curve tracing, insulation resistance measurements, and thermal drone inspections, were conducted to assess system integrity. Operating temperature was estimated using established models due to the absence of direct sensors.
Results
The testing was conducted between 2023 and 2025 and showed that the modules were able to retain 87–88% of their original power, with minimal additional degradation of around 0.4%/year, with IV curves under clear-sky conditions confirming stable electrical behavior over two years, consistent with post-decommissioning measurements.
Electroluminescence imaging, meanwhile, detected only moderate luminescence reductions, with no inactive cells or severe defect propagation.
Furthermore, system-level degradation was found to average about 0.7%/year, slightly higher due to module mismatch, but still below manufacturer expectations.
Safety tests, including insulation resistance and thermal inspections, confirmed the modules were reliable, even for repaired units with minor cracks. Repaired modules showed only mild hotspots, posing no immediate risk to performance or safety.
“Overall, the study provides comprehensive evidence on the performance, reliability, and degradation behavior of second-life PV modules,” said Rüther. “It demonstrates that, despite aging, a significant portion of decommissioned modules can still operate effectively. However, financial incentives are still necessary to establish and scale reuse markets in a sustainable way.”
The research findings are available in “Second-Life Photovoltaics in Practice: Performance Results from a Brazilian Case,” published in Solar Energy Advances.
The UFSC is also hosting Brazil’s oldest PV system. It was deployed by Rüther himself in 1997, after completing a postdoctorate in Solar Energy Systems at Germany’s Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Freiburg, Germany.
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