High through-put, outdoor characterization of silicon photovoltaic modules by moving electroluminescence measurements

Abstract

Fast and non-destructive quality control tools are important to assess the reliability of photovoltaic plants. On-site inspection is essential to minimize the risk of module damage and electrical yield losses. This may only be achieved by using highly sensitive imaging techniques such as luminescence or infrared thermography imaging. Nowadays, electroluminescence is used to detect defects such as local cell changes, series resistances and shunts in solar cells and modules which can cause electrical losses. However, the drawback of this method is the relatively low measurement throughput. To increase the throughput InGaAs cameras with a resolution of 640 × 512 pixels are used, for which low integration times are possible to acquire electroluminescence images. For such low integration times even moving image acquisition and movie recording are feasible to detect the mentioned defects. In this paper, an outdoor electroluminescence setup is presented for mobile handheld recording. Experiments showed that 5 ms integration time is a good compromise between low contrasts for lower integration times and motion blurring for higher integration times. The camera prototype has an onboard computer to avoid image transmission losses. It was controlled and visualized over Wi-Fi and remote desktop connection. The energy supply was provided from LiPo-batteries for improved mobility. In comparison to conventional electroluminescence measurements we can decrease the measurement time of a 20 module string from 5 min to 20 s.