Identification of Bill of Materials and Degradation State of PV modules in the Field via NIR spectroscopy

Photovoltaic (PV) modules exposed in the field are subjected to the influence of environmental stress factors that can cause material and performance degradation. In particular, polymeric materials are sensitive to ultraviolet radiation, temperature and moisture. PV systems with different sizes are often monitored in terms of overall performance and power degradation, but not much attention is given to changes in polymer characteristics, until it is too late. This study focuses on the use of spectroscopy based on near infrared (NIR) to identify the bill of materials (BOM) of field exposed PV modules and to detect signs of polymer degradation. NIR spectroscopy measurements were performed with a hand-held device and carried out on modules from two different PV systems, one located in central Italy and one located in Sweden. The results allowed to identify inconsistencies in the BOMs for the modules exposed in central Italy, and to detect signs of backsheet degradation when the spectra of exposed and unexposed modules were compared. The modules exposed in Sweden, instead, were characterized by less marked differences between spectra from exposed and unexposed modules. The investigation of PV modules in the field via NIR spectroscopy has proved to be an effective means to gain valuable insights on the age of PV modules in the field.