Defect Recognition and Power Loss Estimation Using Infrared Thermography

Abstract

This study investigates how thermal signatures observed in PV systems using infrared thermography (IRT) affect the performance of PV modules and strings. To assess this, we use IRT images as a basis for circuit modeling of modules with defected solar cells. This allows us to calculate the performance of the individual modules with thermal signatures and the module string. We model the IV characteristics of defective modules based on IRT images and fit the results to field IV traces of the imaged modules. By IRT imaging, several thermal signatures have been identified, and by using a portable IV tracer, the power loss related to each defect under the given conditions has been found. Information from the IRT images are used as input to a model we have developed for defect evaluation, and a comparison of model and IV tracer data for a range of defective solar modules is presented. The string modeling shows that the power loss from a given thermal signature is highly dependent on string length and circuit design. For string sizes larger than 20 modules, only defects that affect two or more module substrings are expected to give a power loss higher than 3%