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In this paper, electrochemical degradation of photovolaic modules-encapsulated solar cells-is explored. It is pointed out that both device and insulation properties must be considered in determining the overall performance and remaining life of the system. A quantitative correlation between field-exposure time and exposure time in accelerated multistress tests is developed, based upon the concept that equal quantities of leakage current charge transfer between cells and module frame results in equivalent electrochemical damage. The correlation is useful in interpreting accelerated test data. The effects of temperature, humidity, and applied voltage difference on the quantity and rate of cellframe charge transfer and, hence, on electrochemical degradation are documented. Experimental data indicate that cell-frame polarity also influences the nature and severity of electrochemical degradation. These effects are regarded individually and collectively, and lead to a comprehensive understanding of electrochemical degradation processes in photovoltaic systems. |
