Evaluation of Cell Mismatch in Pre-Exposure Photovoltaic Modules Using Electroluminescence Imaging
Abstract
The objective of this study is to analyze the impact of cell mismatch on the maximum power output in a case study involving seven PV modules from the same manufacturing batch. Since the cells are connected in series, module assembly is performed using cells from the same performance bin to minimize mismatch losses and the manufacturer specifies a batch power tolerance. However, once a PV module is encapsulated, measuring the electrical behavior of individual cells becomes a non-trivial task. In this work, cell mismatch was evaluated by correlating electroluminescence (EL) image pixel intensity with current-voltage (I-V) curve measurements. With the EL images, a normalized brightness matrix for each module was created. The results showed that 5 from the 7 modules presented underperformance (fake power) related to cell mismatch. These findings suggest that low and highly variable cell brightness—potentially resulting from inadequate cell sorting during module assembly—can be associated with underrated power.
Keywords
cell mismatch, underperformance PV module, electroluminescence, pre-exposure PV module, fake power