Corrosion growth of solar cells in modules after 15 years of operation

Abstract

This paper is to study the deterioration of PV modules after 15 years of operation in Thailand. All 16 modules of a string were annually measured in the standard testing laboratory, then taken back to the same position of string since the 7th year after operation. The results and data analysis can be divided into 3 parts consisting of electrical performance evaluation, physical deterioration observation, and corrosion growth on cell ribbons. From the electrical results of performance at STC, it was found that power of modules were less than 80% of the nameplate value in the 15th year for 75% of total modules. The average degradation rates, based on nameplate, was 1.47%/year. The degradation rates of modules since the 10th year after operation were in the range of 2.5 to 3.0%. From the visual failures on the front and rear side of modules were appeared in all modules. During the 12th – 15th year, the corrosion area growth on cell ribbons, calculated by ImageJ program, was around 10–17%/3 years of ribbons area, especially for cells beside junction box. The colors of corrosion products were also observed in both color appearance and color change on each cell of selected modules. For these modules, we intend to continue operation until end-of-life of the system. Another similar module was destructed and taken to investigate. The corrosion products and color of corrosion products can be justified by EDS and referred to ASTM D130 standard. Sn and Pb corrosion products were confirmed by SEM and EDS.