New technique to repair solder interconnection failures in solar panels

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From pv magazine Global

A research group in Japan has developed a new technique to repair failures of solder interconnections in photovoltaic panels.

“In the event of disconnection of busbars and solder ribbons in silicon solar modules, it will be possible to repair the faulty part on the spot,” the research’s corresponding author, Yu Kawano, told pv magazine. “We have developed a low-cost technology to extend the life of the solar cells, allowing them to recover their output directly at the outdoor installation site, without disassembling the solar module or removing it from the solar array.”

The novel methodology utilizes a portable induction heating system provided by Japan-based technology provider Toray Engineering Co., Ltd to repair the solder joint and interconnection failures. “It has a spot diameter of 2.0 mm and operates under a power of 3.5 kW, a frequency of 900 kHz, and a distance between the system and the PV module of 2.0 mm,” the researchers explained.

The team tested the induction heating system by applying it only to the region with the interconnection failures in damaged modules, with the heating time varying from 0.1 s to 10.0 s, and said that a heating time exceeding the 10.0 s threshold may result in further damage to the panels.

For the testing, the scientists utilized damaged and non-damaged modules with a back sheet/EVA/Si solar cells/EVA/cover glass structure, with the dimensions of 145 mm × 145 mm, and series interconnected solar cells with a size of 26 mm × 120 mm.

“According to the result, the optimized heating time of 2.0 s results in a more homogeneous bright across the entire module with high electroluminescence (EL) intensity lines in both horizontal and vertical lines,” they specified. “The too-long heating time of 10.0 s deteriorates the fill factor (FF) value to 0.765.”

The scientists said the system proved to be effective in decreasing the series resistance and recovering the performance of the damaged panels.

“It is noted that the more obvious recovery of the performance can be seen using this proposed repair method in the silicon PV module with the many failures of joints of solder and electrodes, solder, and interconnection ribbons,” they stated. “The optimized heating time for the disconnected Si PV module results in the recovery of the FF value close to that for the standard Si PV module, consistent with the recovery of the EL imaging.”

The new technique is described in the study “Development of repairing technique for interconnection of silicon photovoltaic modules using an induction heating system,” published in Solar Energy. The research group includes scientists from the Ritsumeikan University and Japanese copper wire manufacturer Showa Seisakusho Co., Ltd.

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