Passive electroluminescence and photoluminescence in outdoor photovoltaic modules: synchronous and asynchronous lock-in strategies

Photovoltaic power plants require module inspections to detect failures, thereby avoiding safety issues and optimizing overall operation. Luminescence imaging acquisition offers a viable solution for photovoltaic inspections, providing valuable information about module performance. This article presents a novel technique termed passive electroluminescence and photoluminescence, capable of producing luminescence images under daylight conditions by using sunlight or string current as excitation sources for photoluminescence and electroluminescence modulation, respectively. To achieve this modulation, an electronic board has been developed, which connects within a photovoltaic string and allows for measurements during the normal operation of the plant. The study focuses on analysing two strategies: synchronous and asynchronous lock-in approaches. While the synchronous method requires coordination between the camera and the electronic board, the asynchronous method operates independently of such synchronization. Although both strategies have been successfully validated, results indicate that the asynchronous strategy is faster and simpler to implement, whereas the synchronous approach may yield slightly higher quality results.