Recovery of Silver From Waste Crystalline Silicon Photovoltaic Cells by Wire Explosion

To establish an effective recycling process for waste photovoltaic (PV) panels, a wire explosion method using a high-voltage pulsed discharge was used to separate silver (Ag) from an ethylene-vinyl acetate (EVA) copolymer resin sheet. The cell used in the experiment was prepared by removing the aluminum frame and the glass cover plate from the waste PV panel. Ag particle recovery experiments were conducted in water. Electrodes were installed on each copper busbar of the cell. A 40.8- $\mu \text{F}$ capacitor was charged to a maximum of 15.0 kV and then discharged using a mechanical switch. Wire explosions occurred through the 102 Ag wires connected in parallel between the busbars. The particles recovered after the wire explosion were sieved and then characterized by inductively coupled plasma atomic emission spectroscopy and X-ray fluorescence. Scanning electron microscope and energy dispersive spectroscopy analysis revealed that the majority of separated Ag particles were attached to the silicon particles. The Ag recovery rate was 69% at a charging voltage of 15.0 kV. Higher discharge energies increased the Ag recovery rate; however, the recovered particles had lower Ag concentration. A circuit simulation was performed to analyze the current waveforms and calculate the current distribution. Shadowgraph imaging was used to observe the separation process of Ag particles and the EVA layer by wire explosion during pulse discharge. The shadowgraph images indicated that plasma generation and gas expansion have important roles in the separation process.