Applications of infrared thermography in the characterization of photovoltaic cells, modules and arrays

Abstract

Infrared thermography is a valuable technique to obtain surface temperature profiles. In photovoltaics (PV) it has been used in different applications, being specially useful in field tests to detect hot-spots, that is, severely localized heatings in one or several cells inside a PV module what could produce irreversible damages. With the increase of PV potential, the number of manufacturers and the diversity of installations, applications of IR thermography in PV have also widened. This paper presents a summary of the results of different IR tests performed in PV devices. IR images have been taken in individual cells at different laboratory conditions, isolate PV modules from several technologies also at different working conditions, and fields tests of PV plants. The paper analyzes the information that can be obtained from each test in relation to the optimal operation of PV devices, and shows the main troubles found when working with IR cameras in this type of systems. Particularly in the in-field characterizations of PV plants some difficulties arise such us the differences between frontal (glass) and rear (polymeric material) view of the PV modules, the problem of solar reflected radiation when images are taken in the front side of the modules, and the angle of incidence of the camera with respect to the array. Information obtained form IR characterisation is valuable to decide if a cell or a module presents, or will probably present, problems that could reduce its lifetime, to determine the production losses due to hot-spot in PV plants, and also to show minor faults indicating that some improvements are required.