Photoluminescence imaging of silicon modules in a string

Abstract

Spectral imaging techniques are a powerful tool for surveillance and monitoring of degradation mechanisms in PV modules. Luminescence images of solar modules have until recently been predominantly acquired in controlled laboratory settings. Recent attempts have been made in detecting luminescence in daylight. This study aims to present a proof of concept for detection of photoluminescence with sunlight excitation. It enables imaging of several modules in a string as well as several strings simultaneously by changing the operating point through wireless and contactless communication with one or more string inverters. This new approach is validated with the electroluminescence technique as well as with an already established photoluminescence technique under sunlight excitation. Due to the string inverter's reaction time, the change in illumination results in lower image quality. However, with a more up-to-date imaging equipment, this approach is promising for identification of certain degradation mechanisms which can be detected with lower resolution such as large area damage and inactive areas. Further studies are needed to optimize the method and potentially use it in connection with an unmanned aerial vehicle inspection.