Optimized EVA Decomposition in Bifacial Solar Panels: Sustainable Recovery of Polymerized Oil and Materials

Abstract

The disposal of end-of-life (EOL) photovoltaic (PV) solar panels presents environmental challenges due to hazardous materials and complex structure. This study proposes an optimized method for recycling bifacial solar panels, which lack a back sheet and use ethylene-vinyl acetate (EVA) as the sole encapsulant. The process achieves 100% recovery of valuable materials, including polymerized oil, clean glass, solar cells, and copper tape. Unlike traditional PV panels with back sheet polymers like PVF, PET, or PVDF, bifacial panels simplify the recycling process. EVA, composed of hydrogen, carbon, and oxygen, is more environmentally friendly, especially without fluorinated compounds. Using a modified pyrolysis reactor, the EVA layer is degraded in inert conditions, minimizing emissions and producing polymerized oil. This oil can be used as a lubricant, while the recovered glass, solar cells, and copper tape are reusable in manufacturing new panels. Optimized oil yield is achieved using Response Surface Methodology (RSM) and Box-Behnken Design (BBD). At a heating rate of 8.92 °C min⁻¹, a 31.82-min hold time, and a maximum temperature of 528.22 °C, the process yields 57.53% polymerized oil. The oil is characterized by thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FT-IR), meeting ASTM and Australian diesel standards. This method maximizes material recovery and supports a circular economy, enhancing solar energy system sustainability.