Detection of defects in photovoltaic modules

Abstract

External and internal factors can lead to the development of defects that affect the performance of Photovoltaic (PV) modules over time. This study aimed at detecting and characterizing defects in PV modules using electroluminescence (EL) imaging, a powerful technique for identifying various types of defects, including cracks, broken cell interconnections, and shuntsthat are not noticeable to the naked eye. A forward biasing voltage approximately equal to the open circuit voltage of the PV module was applied to the modules in the dark causing them to emit light. The emitted light (EL signal) in the infrared region was captured by a specialised camera (infrared sensitive charge coupled device (CCD) camera with visible light filters to for images. These images were then processed using image enhancement software to enable visual identification of defects. Results from EL measurements revealed that areas of PV modules with defects appeared darker or emitted less light compared to areas without defects. Some of the identified defects in the selected modules included micro-cracks, dark cores, finger interruptions, multiple directional cracks and inactive solar cells. These defects could significantly affect the module performance under real operating conditions in the long run, thus impacting the PV system’s energy yield.