Strain monitoring within photovoltaic laminates: A fibre Bragg grating sensor proof-of-concept and comparison with digital image correlation

Temperature variation is a fundamental environmental factor that affects the long-term reliability of photovoltaic (PV) modules, giving rise to thermo-mechanical stresses within a PV module. These stresses are created by the mismatch in the coefficient of thermal expansion (CTE) of the different materials that form the laminate. In this work, we present an optimised procedure to integrate optical fibre Bragg grating sensors (FBG) within the PV laminate and a temperature-compensated analysis of the detected strain on the Si cell for small glass-glass PV laminates subjected to thermal loads. At the same time, digital image correlation (DIC) is used as alternative technique for comparison of the measured strain and to study the influence on the mechanical behaviour of integrating optical fibres within the laminate. The results indicate the potential of FBG sensors for strain measurements and the negligible effect on the mechanical behaviour of their integration. This proof of concept provides a method to quantify the strain within the module during manufacturing processes, accelerated testing or in-field monitoring, which can be advantageous for improving the reliability of the PV modules.