Study on Optically and Digitally Filtered Large-Scale Background Noise for Daylight EL Imaging of PV Modules

Outdoor daylight electroluminescence (EL) and photoluminescence (PL) imaging techniques have gained significant interest in the Operations & Maintenance industry for their safety, feasibility and effectiveness in identifying defects and faults in PV modules. Previous research have shown that fast solar irradiance variations pose the greatest challenge for digital filtering. Additionally, the evaluation of optical daylight filters shows that in bright daylight, narrow bandwidth filters enable the use of wider lens apertures, leading to higher-quality and more robust EL images. This work aims to quantify, across the imaging camera's spectral range, the sunlight variations that cannot be digitally filtered and to provide insights into the properties of narrow band-pass filters for blocking unwanted sunlight photons detected by the camera. The findings are validated through EL images captured in bright daylight, demonstrating how the signal-to-noise ratio improves when critical portions of the solar spectrum are effectively filtered out.