A Ghanaian research team has conducted a series of tests to evaluate the performance of polycrystalline solar modules in photovoltaic systems that have been operating in their home country for at least five years. They found that most of the panels could “fail” before 20 years of outdoor use.
Their work specifically analyzed 48 solar panels from 12 different photovoltaic systems. “In each PV system, stratified random sampling was used to select four PV modules for testing,” they explained. “All the systems were connected to the grid and installed on the roofs for 5-9 years.”
Deciding to keep the manufacturers anonymous, the researchers labeled the 12 locations with the letters A to L and said the panel’s wattage ranged from 100 W to 460 W. They performed a visual inspection based on a checklist prepared by the US Department of Energy. National Renewable Energy Laboratory (NREL) and used a Seaward PV 210-meter automated IV Tracer to measure panel performance.
They said that none of the PV systems were subject to shading and that they were all built using the same installation and maintenance practices.
Through testing, the researchers found that the minimum degradation rate of the analyzed modules was 0.79%/year, while the maximum degradation rate is 1.67%/year. They also found that the modules degraded at different rates, with degradation rates ranging from 0.78 to 1.95%/year, with mean and median degradation rates of 1.36%/year and 1.38%/year, respectively.
“Overall, only one manufacturer’s PV modules degraded less than the guaranteed percentage of 0.8 percent per year, while other manufacturers’ modules degraded more than 1.0 percent per year,” they noted, noting that 42 modules exceeded the 1.0 percent annual threshold. , which they said meant these panels could “fail” before 20 years of use in outdoor conditions in Kumasi. “Of the 48 solar modules examined, 6 solar modules, representing 12.5 percent, are likely to operate reliably for 20-25 years, and only 4 solar modules, representing 8.3 percent, are expected to meet the 25-year warranty period.”
The research team emphasized that the solar panels of the manufacturer with the highest average degradation rate do not necessarily mean that all products from this manufacturer are of lower quality. It also said that the rate of degradation did not correlate with the age of the modules, and that the biggest power loss was mainly due to the lower short-circuit current.
The academics presented their findings in a paper “Degradation analysis of polycrystalline silicon modules from different manufacturers under the same climatic conditions,” published Energy conversion and management: X. “The results of this study were comparable to the results obtained in the degradation analysis of polycrystalline silicon modules from different manufacturers in other countries,” they concluded.