Prediction of Power Output from a Crystalline Silicon Photovoltaic Module with Repaired Cell-in-Hotspots

Abstract

Recycling of problematic photovoltaic modules as raw materials requires considerable energy. The technology to restore cells in hotspot modules at a relatively low cost is more economical than replacing them with new modules. Moreover, a technology that restores power by replacing a cell-in-hotspot of a photovoltaic module with a new cell rather than replacing the whole module is useful for operating power plants. In particular, power plants that receive government subsidies have to use certified modules of specific models; the modules cannot be replaced with other modules. Before putting resources into module restoration, predicting the power of a module to be restored by replacing a cracked cell with a new cell is essential. Therefore, in this study, the module output amount after restoration was calculated using the previously proposed relative power loss analysis method and the recently proposed cell-to-module factor analysis method. In addition, the long-term degradation coefficient of the initial cell and the loss due to the electrical mismatch between the initial and new cell were considered. The output of the initial cell was estimated by inversely calculating the cell-to-module factor. The differences between the power prediction value and the actual experimental result were 1.12% and 3.20% for samples 190 A and 190 B, respectively. When the initial rating power and tolerance of the module were corrected, the differences decreased to 0.10% and 2.01%, respectively. The positive mismatch, which restores cells with a higher power, has no loss due to the reverse current; thus, the efficiency of the modules is proportional to the average efficiency of each cell. In this experiment, the electrical mismatches were only 0.37% and 0.34%. This study confirmed that even if a replacement cell has a higher power (<20%) than the existing cell, the power loss is not significantly affected, and heat generation of the existing normal cell is not observed. Hence, it was concluded that when some cells are damaged in a crystalline solar cell, the module could be restored by replacing only those cells instead of disposing of the entire module. However, for commercialization of the proposed method, a long-term reliability test of the module repaired using this method must be performed to confirm the results. Following this, recycling cells instead of recycling modules will be an economical and eco-friendly alternative.