Degradation analysis of polycrystalline silicon modules from different manufacturers under the same climatic conditions

Different kinds of photovoltaic modules from various manufacturers have entered the PV market. However, the long-term performance of these modules under outdoor conditions is uncertain. This study evaluated the degradation of polycrystalline silicon modules from 11 different manufacturers installed under the same climatic conditions in Kumasi, Ghana with the aim of predicting the long-term performance of the modules. Specifically, this study sought to: (i) analyse the power degradation rates of the modules and determine the correlation between the degradation and the age of the modules, (ii) determine the correlation between the power degradation and other electrical performance parameters of the modules, (iii) identify the modules with visual defects and compare their degradation rates with the modules without any visual defects, (iv) compare the degradations of PV modules from the same manufacturer installed under the same climatic conditions for the same number of years and (v) assess the installation and maintenance practices that could negatively affect the degradation of the modules. Forty-eight PV modules from 11 different manufacturers were sampled from 12 PV systems installed between 5 and 9 years. The methods used were visual inspection, observation, interviews, and current-voltage (IV) tracings. The results revealed the mean power degradation rates of the modules between 0.79 and 1.67%/ year, contingent on the manufacturer. The power degradation rate had no correlation with the age of the modules but the power degradation of all modules was mainly due to the degradation of short circuit current (Isc) of the modules. Light encapsulant discoloration, dark encapsulant discoloration, minor frames corrosion, and minor metallization discoloration were found on modules from four different manufacturers. However, the degradation of electrical performance parameters could not be solely attributed to these visual defects. Slight variations in degradations were observed for PV modules from the same manufacturer installed under the same climatic conditions for the same number of years. The installation and maintenance practices of the system owners were similar and unlikely to impact differently on the degradation of the modules from different manufacturers.