Photovoltaic systems (PV systems) do not produce any waste or emissions during the production of electricity. On the other hand, PV systems must be manufactured, installed and re-dismantled at the end of their useful life, which impacts the environment. Photovoltaic modules recycling has not yet been so important for research institution and industrial companies. PV system life is longer than for common goods and the number of modules to be recycled is still low – only a few hundreds of tons a year.
According to the Green Match simulation, the amount of PV waste can be estimated about 60 million tons of PV panels waste lying in landfills by the year 2050; since all PV cells contain certain amount of toxic substances, that would truly become a not-so-sustainable way of sourcing energy. There are two approaches to recycling – PV modules recycling regardless of the production technology, and design modifications to make recycling easier. A challenging task is to develop optimal recycling technology and to finance its high investment costs.
The main objectives of the recycling of the PV modules are to reduce the amount of remaining waste and to maximize material recovered for further production. The manufacturing process is as follows: On the front of the PV module tempered glass is placed. The glass is highly shock-resistant and can withstand relatively large hail. A plastic EVA (ethylene vinyl acetate) film is applied to the glass and the interconnected PV cells are placed on it. The EVA film is again deposited on the PV cells and the rear part is usually laminated by polyvinyl fluoride (Tedlar). The air is exhausted from the space between the glass and the Tedlar and the module is heated above the melting point of the EVA film. EVA melts in the space between the front glass and the rear laminate as a sealing compound. The modules are framed and sealed with silicone sealant into aluminum profiles and provided with a junction box with output contacts. The lifetime of high-quality PV modules based on crystalline semiconductors ranges from 20 to 30 years. Main recycled materials from them are glass, aluminum, plastic, photovoltaic cells and heavy metals.
PV modules recycling is becoming increasingly important with the higher demands for silicon. PV recycling process consists of two main phases:
PV modules delamination is also required for the recycling process. EVA, glass, Tedlar, aluminium frame, steel, copper and plastics are removed and separated from each other in this step. In the following section, three experiments for PV modules and PV cells recycling are presented and compared (chemical, thermal and mechanical methods) together with the laser method to obtain silicon wafers.