Separating materials from photovoltaic panels through thermomechanical processes and laser beams for the extraction of metals

Abstract

Usually, a photovoltaic panel is composed of either monocrystalline or polycrystalline silicon cells that convert sunlight into electricity, with an average lifespan of nearly 30 years based on a guaranteed performance outlet of 80% power. After this period, the panels turn into waste and must be discarded properly, with recycling materials being the most resourceful method. The initial goal of this research was to develop a physical pre-treatment method aiming at separating components and determining adequate speed and power necessary for the removal of the sealant (ethylene vinyl acetate [EVA]) present in photovoltaic cells. This would enable easier extraction of commercially valuable metals, such as silver, metallic silicon, copper, and aluminum utilizing a laser beam. The methodology involved utilized photovoltaic cell samples subjected to a thermomechanical pre-treatment to remove prior components, followed by the application of a laser beam at varying potency and velocities to find the optimal settings to remove EVA present in samples without a backsheet foil. After removing the EVA, manual extraction of copper ribbons, silver filaments, and metallic silicon was carried out using a micro-grinder and a mill, producing a powder that was then analyzed by X-ray fluorescence (XRF). The results showed that the initial components (junction box and backsheet foil) could be removed through thermomechanical processes , followed by EVA removal using a 400 W laser beam at 200 mm/s. Following that, the copper ribbons, with an average content of 91.71% Cu, were separated manually. Silver and metallic silicon recovery through milling resulted in a powder with 0.6% Ag and 93% Si content.