Comprehensive study of performance degradation of field-mounted photovoltaic modules in India

Abstract

The All India Survey of Photovoltaic Module Reliability 2014 is an enhanced version of the survey conducted in the previous year, with detailed characterization of PV modules including current-voltage, infrared and electroluminescence imaging, visual inspection, insulation resistance test and interconnect breakage test. More than a thousand modules were inspected in the field and the main results of the survey are presented in this paper. The average P-max degradation rate for the so-called good' modules (Group X) is 1.33%/year which is higher than that commonly projected by manufacturers, and widely employed in financial calculations. Modules falling in the not-so-good' category (Group Y) show even higher degradation rates, and it is at least partly due to higher number of micro-cracks in the modules, and increased degradation of the packaging materials like encapsulant, backsheet, etc. Modules in Hot' climates degrade faster than modules in the Non-Hot' climates. Degradation in fill factor is the primary cause for performance degradation in the young modules (ages <5years), whereas short-circuit current degradation is the main contributor to power degradation in the older modules. Small installations (<100kW(p) capacity) show higher degradation than large systems, which may be partly due to lack of proper due diligence by the owner at the time of procurement and installation.