## 2 Modern Recycling Technologies for PV Panels and Wind Turbines: A Systematic Literature Review  
### Ecology Issues of Renewable Energy Sources (RES)-Capacity Recycling  
At the end of 2018, the global installed PV capacity reached 486 GW (REN21, 2019; Figure 1). Given that the average life of modern solar panels is 25 years [15], and the average weight of the most common 200 Wp multi-Si PV model is 16.8 kg [16], the world may face the need to dispose of more than 24 million tons of expired multi-Si PV models by 2035. In the future, these volumes will only increase due to the rapid development of solar energy in all countries [17; 18]. According to expert forecasts, PV panels will reach 4500 GW of cumulative installed capacity worldwide by the middle of the century [15]. The PV solar panels contain lead (Pb), cadmium (Cd), and many other harmful chemicals. So far, the most common EoL treatment technology for PV models remains their disposal at landfills. [15]. It can be quite dangerous since harmful chemicals can leak into the ground, causing drinking water contamination [20]. Incineration is also used for PV models, as with regular municipal waste. It is crucial to understand that incinerating all kinds of electronic waste, including PV modules, can release toxic heavy metals into the atmosphere [21]. It is also known that some of the materials in PV modules are persistent and accumulative when released. This can cause long-term adverse ecology effects. Incineration also abolishes the opportunity of recovering raw materials. The only advantage of this method is that PV modules do not need to be separated from other commercial or industrial waste [22]. Industrial recycling capacities of used or defective PV models are currently limited and represented only by the Czech company Retina, several factories of First Solar in the United States, Germany, and Malaysia, Toshiba Environmental Solutions [15], and Veolia's new factory in France. At the legislative level, only the EU has established the rules for the collection and processing of solar panels in Waste of Electrical and Electronic Equipment (WEEE) Directive (Directive 2012/19/EU). Some countries with developed solar energy, such as South Korea, Japan, and the USA, are actively working on the problem of organizing the recycling of solar waste, while others, including China, are only exploring ways to solve this problem [23]. As has been previously reported in the literature, existing industrial technologies for recycling solar panels make it possible to achieve 95-97% recovery of cadmium and tellurium for thin-film solar cells [24], 90% recovery of glass [15; 24], and 80% recovery of silicon for multi-Si PV models [25]. They also achieve 67-81% recovery of aluminum and 80% recovery of ethylene-vinyl acetate (EVA),  
Figure 1: Historical development of annual new grid-connected photovoltaic (PV) installations (in GW) and anticipated decommissioning until 2035. Source: based on [19]. which is used to fix individual PV models into a single panel. The use of recovered materials in the production cycle reduces resource consumption. It can achieve a drastic reduction in waste; however, it is associated with enormous expenditures of energy and/or chemical materials, as well as the emission of significant amounts of harmful substances into the atmosphere. Therefore, according to the data [16], the recycling of all the components of 1-kW multi-Si PV panels by modern industrial thermal and chemical methods emits 6.32 kg SO\({}_{2}\), 23.4 kg NO\({}_{2}\), 13.8 kg CO\({}_{2}\), as well as 0.97 kg of ammonia (NH\({}_{3}\)), 2.59 kg of ethylene, and 4.26 kg of methane. At the end of 2019, the worldwide installed capacity of wind turbines reached 621 GW and 29 GW for onshore and offshore wind energy, respectively [26] (Figure 2). Considering the historical pace of development of wind energy in the world and an average 20-year lifetime of wind turbines, one can expect that in the coming years, up until 2030, the volumes of decommissioning of wind turbines will grow exponentially.