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.

Effect of Solder Flux on Resistive Solder Bond Hotspot Generation in Photovoltaic Module Circuit Process and Restoration of Hotspot Module

“…According to the previous study, in the restoration of the back surface field (BSF) type cell, which is an early model of the crystalline silicon solar cell, almost no decrease in output due to cell deterioration was observed. [30] The cell taken for this experiment was of passivated emitter rear contact (PERC) type, which was the next generation of BSF cells, and in this case, it was found that the higher the initial efficiency, the higher the degradation rate of the cell when the module is restored. The decrease in output was mainly caused by a decrease in V mp , which can be found in the increase of series resistance elements due to cell deterioration.…”

Effect of Cell Electrical Mismatch on Output of Crystalline Photovoltaic Modules

“…The loss due to the electrical mismatch of the cell has been published as a concept called RPL (relative power loss), which is not precisely defined and classified before the CTM factor [48]. RPL is expressed as the difference between the maximum power (Pmpc) of n individual cells connected in series to form a cell string or module and the output power of the cell string.…”

“…In a previous study [48] that reported repairs of a waste module containing some damaged cells by replacing it with a new cell, it which was checked whether the same results were obtained even when the module type was different as a single crystal. The cell replacement experiment followed the sequence from previous studies.…”

Investigating defects and annual degradation in UK solar PV installations through thermographic and electroluminescent surveys

“…They could lead to electrically disconnected cell regions, causing a decrease in short-circuit current and shunt resistance 24 , subsequently reducing the module's power output 25 . Cracks may also develop in the PV module if there are localised hotspots 26,27 .…”