Degradation and Defect Characterisation of Field-Deployed Silicon PV Modules

A sample of fifteen monocrystalline silicon-based PV modules was tested and characterised in this study. These modules have been deployed in the field for over a decade at the Outdoor Research Facility of Nelson Mandela University, South Africa. Various characterisation techniques were utilised, including visual inspection, electroluminescence (EL) imaging, and current-voltage (I-V) curves. A detailed analysis was done on the various PV modules in order to understand the observed defects or anomalies and associated performance degradation. When compared to historically acquired I-V curve measurements, the modules show substantial degradation in the performance for one type of module and the other module type does not show any power decrease compared to specification. Combining visual, UV Fluorescence (UV-F) imaging, and EL imaging provided deeper insight into hidden defects and material degradation not evident from visual inspection alone.