Outdoor photoluminescence and electroluminescence imaging of photovoltaic silicon modules in a string Free

Spectral imaging techniques are powerful tools for surveillance and monitoring of degradation mechanisms in PV power plants. Luminescence images of silicon solar modules have until recently been predominantly acquired in controlled laboratory settings. Recent attempts have been made in detecting photoluminescence from silicon PV modules in daylight. This study aims to present an approach for detection of photoluminescence with sunlight excitation. It enables imaging of several modules simultaneously by changing the string’s operating point through wireless, contactless communication with the string inverter. The advantage of this approach compared to electroluminescence imaging is that it can be conducted in daylight and it does not require wiring of the modules. However, due to the string inverter’s reaction time, the change in illumination causes image quality to deteriorate compared to the methods for photoluminescence imaging using instantaneous switching of the operating point and electroluminescence imaging. A comparison is conducted between photoluminescence images acquired through string inverter modulation and images acquired through instantaneous switching as well as with electroluminescence images. It shows that the photoluminescence images obtained though string inverter modulation can be used for identification of degradation mechanisms such as series resistance. Further studies are needed to improve the image quality and potentially use it in UAV inspections.