Electroluminescence inspections of PV modules and strings by a self-powering configuration in daylight mode

Abstract

Electroluminescence (EL) imaging is a widely used tool for identifying defects in the solar cells of photovoltaic (PV) modules. Traditional EL inspections require dark conditions and module disassembly, making them costly and logistically challenging. Daylight Electroluminescence (dEL) has emerged as a cost-effective alternative, enabling on-site inspections under any irradiance conditions without module dismounting and thereby reducing costs. However, EL inspections require current injection, necessitating an external power source. Solutions like bidirectional inverters have been proposed to address this challenge. This study proposes a novel self-powered dEL methodology that uses other PV strings in the plant to supply the necessary current. The method employs a switching procedure to filter ambient light and allows entire string inspection without dismounting modules or using external power. Field tests across various irradiance conditions show that the resulting images are comparable to those obtained in controlled darkroom environments, validating the method’s effectiveness and operational advantages.