Process (computing)

Engineering

Ecology

Biology

Materials science

Layer (electronics)

Thin-film transistor

Operating system

Computer science

Chemical engineering

Dissolution

Polymer

Waste management

Nanotechnology

Copolymer

Ethylene-vinyl acetate

Process engineering

Environmental science

Composite material

Polycrystalline silicon

Photovoltaic system

Hazardous waste

Electrical engineering

Engineering physics

Solar Energy Materials and Solar Cells

End-of-life photovoltaic modules can be hazardous wastes if they contain hazardous materials. The main problem arising from this type of waste is the presence of environmentally toxic substances and the poor biodegradability of the waste, which occupies great volumes when landfilled. For these reasons, photovoltaic modules have to be treated before landfilling as required by the legislation. The subject of this paper is the polycrystalline silicon type photovoltaic modules. They were treated with a physical and a chemical process. The physical process was aimed at the recovery of glass, metals, and the polyvinyl fluoride film. The modules were initially shredded with a knife mill and then processed with heavy medium separation, milling, and sieving. The glass (76%) and 100% of the metals were recovered respectively, at a grade of about 100% and 67%. Finally, a flow sheet of the physical process was proposed. The chemical process was aimed at identifying the best conditions which allow the dissolution of the EVA (ethylene vinyl acetate), that is the polymer that attaches the three layers that make up the module, namely the glass, the polycrystalline silicon, and the polyvinyl fluoride support. The experimental factors investigated were: type of solvent, thermal pretreatment, treatment time, temperature, and ultrasound. The best conditions to completely dissolve EVA in less than 60 min were the use of toluene as a solvent at 60 °C combined with the use of ultrasound at 200 W, while the pretreatment at 200 °C appeared to be useless.

Photovoltaic module recycling, a physical and a chemical recovery process