Optimisation of electroluminescence setup for characterisation of photovoltaic module degradation

Abstract

Electroluminescence (EL) is a useful characterisation tool for the early detection of performance limiting defects such as micro-cracks, unwanted impurities inside photovoltaic (PV) module cells and grain boundaries[1][2]. Most micro cracks result from the manufacturing process, transportation, and handling during storage and installation. After deployment, micro cracks can become more severe due to thermal cycling and dynamic wind loading. In order to correctly interpret EL images and be able to compare images taken at different degradation stages, the images need to be taken under similar resolution, integration time, applied current as percentage of short circuit current and environmental conditions. This paper discusses these settings and how best to optimise them to efficiently and accurately image degradation present in PV modules. The modules used in this work are two monocrystalline modules (A and B of 60 and 72 cells respectively). Degradation of PV modules such as Potential Induced Degradation (PID) or micro-cracks can affect the long-term reliability and profitability of PVinstallations. This paper describes and identifies the optimum settings (camera and voltage bias) at which module performance degrading defects and resistive properties may be observed. The EL method is fast and non-destructive and can be used to assess modules prior to deployment.