Material Recovery from End-of-Life Solar Photovoltaic Module Through Thermal and Chemical Processes

Abstract

The expected life of photovoltaic (PV) modules is 10–20 years as solar modules degrades over the course of time. This degradation is mainly due to the water ingress, ultra violet (UV) rays exposure and temperature stress. The module failure indicators include delamination of the module encapsulation, anti-reflection coating deterioration, discolouration of Ethylene Vinyl Acetate (EVA), glass breakage, open/short circuit failure, hot spot failure and bypass diode failure. The most valuable element utilized in terms of economics is pure silicon, which can be recycled from PV cells. Pure silicon may be recovered from broken or end-of-life PV modules, which can have both financial and environmental advantages. Because of the high purity required of the recovered silicon, chemical treatment is the most critical stage in the recycling process. This work used a variety of etching techniques to etch electric connections, anti-reflective coating and the p–n junction in crystalline-Si(c-Si)-based PV systems which require nitric acid, potassium hydroxide and hydrofluoric acid. Also, the study contains the comparison between thermal and chemical processes availed for the removal of EVA. The thermal process has been performed using a muffle furnace where the samples have been heated at different temperatures 250, 350, 375 and 400 °C at a rate of 15 °C/min. The intact solar cells have been gathered after the heating process and then chemical processes to remove coatings have been performed. Whereas the chemical process for EVA removal required the use of chemical solvents like acetone, ethanol, trichloroethylene and nitric acid in which cells have been immersed. An oven and heat gun has been used to remove the Tedlar sheet. Lastly, the bare silicon wafers obtained from the processes have been collected and tested to confirm the removal.