Outdoor photoluminescence imaging of solar panels by contactless switching: Technical considerations and applications

Monitoring the performance of solar modules in a photovoltaic system is critical in order to understand the health of the system. Existing methods for field inspection have limited capability of detecting various electronic defects that can, however, be identified with luminescence-based methods. A contactless outdoor photoluminescence-imaging based measurement method that uses the sun as the excitation source was presented in our earlier work. This paper extends our previous work and presents two unique applications to (a) identify and quantify local areas of high series resistance within the cells and (b) identify bypass diodes that have failed in open-circuit. The paper also discusses specific technical considerations of this method. The main merit of this method is that it can be used when the module is under normal operation in the field, without requiring changing of the electrical wiring of the photovoltaic array.