Study on the separation of crystalline silicon photovoltaic modules using the green solvent NMP

Abstract

Solar energy, with its advantages of safety, reliability, cleanliness, and wide distribution, has seen a significant increase in photovoltaic (PV) installations. However, this growth has led to a large number of end of life PV modules. The adhesive effect of EVA (ethylene–vinyl acetate) makes it difficult to effectively separate and recycle the various layers of these modules. Therefore, the key to recycling silicon PV modules lies in removing or weakening the adhesive properties of EVA while protecting core components such as silicon from damage, thereby achieving efficient separation and recycling of the layers. This paper proposes a novel green treatment method using N-methylpyrrolidone (NMP) as a solvent for recycling discarded PV modules. Through experimental studies, we investigated the effects of different NMP treatment conditions-including temperature, time, sheet size, and rotor speed-on the reaction rate of EVA. The optimal processing condition was found to be heating at 150 °C for 45 min. Kinetic fittings were performed under various conditions, and parameters were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and contact angle measurements. The mechanism of the reaction between NMP and EVA was analyzed. Finally, experiments were conducted on Commercial PV modules to develop a fundamentally harmless recycling process. A life cycle assessment of this recycling process was also carried out, providing theoretical guidance for future applications of NMP in the treatment of waste silicon PV modules.