Analysis of electroluminescence and infrared thermal images of monocrystalline silicon photovoltaic modules after 20 years of outdoor use in a solar vehicle

Infrared (IR), under forward bias and under illuminated condition, and electroluminescence (EL) are the most employed non-destructive techniques to monitor performance of photovoltaics (PV) modules. The application of these two techniques have advantages and drawbacks and a combined use has not been made extensively. With this purpose, we performed a quantitative comparison of EL and IR images of monocrystalline PV modules after 20 years of outdoor exposure and use. The proposed methodology relies in the analysis of frequency histograms of IR and EL images. Results provides local information on PV modules state, useful to distinguish disconnected cell interconnect, humidity corrosion, and broken fingers in highly damaged solar cells. This method contributes and supports to the current knowledge of IR and EL imaging techniques used to assess different forms of damage in monocrystalline silicon PV modules. Moreover, it could contribute to the future draft technical specification IEC 60904-13 for EL.