Characterization of defects in photovoltaic modules using electroluminescence imaging and current-voltage measurement techniques

Abstract

External and internal factors can lead to the development of defects that affect the actual performance of PV Photovoltaic (PV) modules over time. This study was aimed at characterizing defects that arise in PV modules using electroluminescence imaging, a powerful technique for identifying various types of defects, including cracks, broken cell interconnections, and shunts, especially those not noticeable to the naked eye. Additionally, it sought to assess the impact of these defects on the performance of PV modules using current-voltage curve measurements. Four mono-crystalline modules and one polycrystalline module, labeled A, B, C, D and E were investigated in this study. Module A was a 20 W monocrystalline silicon module that had been in use at the Physics Department for the last five years and showed no signs of damage on its surface. The other two modules, module B and module C, were new 395 W monocrystalline modules. Module B had visible damages resulting from mechanical stresses during transportation from the supplier, while Module C was used as a reference module. Module D was 120 W polycrystalline module that had also been use at the Physics Department, while Module E was a new monocrystalline outsourced from the local market. In electroluminescence (EL) imaging, the selected PV modules were forward-biased with a defined biasing voltage, emitting an EL signal captured by an infrared-sensitive CCD camera in the form of 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. Further analysis of the performance of these modules was conducted using an I-V 400 W Photovoltaic analyzer for current-voltage (I-V) measurements. The results indicated that the 20 W monocrystalline silicon module had lost approximately 40% of its total output, resulting in an output of 1179 W, while the damaged 395 W monocrystalline silicon modules exhibited a significant decrease in power output, declining from 395 W to 155 W within a very short period compared to the reference module. This suggests that PV modules installed with defects degrade faster, resulting in a notable reduction in power output within a relatively short period compared to modules without defects.