# The Design Value for Recycling End-of-Life Photovoltaic Panels
## 3 Effective PV Panel Design Methods for Recycling at EoL
### Design for Recycling
Two main phases of the diagram are the thermal and chemical processes:  
* The **thermal process** must occur at relatively low temperatures (\(\leq\)60 \({}^{\circ}\)C) because, in addition to bringing a minimum energy expenditure and therefore a low environmental impact, this process allows for the avoidance of the thermal degradation of the plastic, allowing, in this way, the recovery of the polymeric materials contained in the panel. In addition, by containing emissions into the atmosphere, it makes it easier to obtain authorization to build any treatment plants. * The **chemical process**, on the other hand, is the most important step in the recycling process because the chemical treatment conditions must be precisely adjusted to achieve the required level of purity of the recovered silicon. By following quality control, pure silicon in the form of powders can be used for the production of new photovoltaic cells and consequently of new modules. The recycling process starts with mechanical disassembly, with which the frame, the tempered glass and the PV module are separated. Then, a thermal process isolates the photovoltaic cells by exploiting the softening of the polymer layers in EVA. Subsequently,  
Figure 9: Logical scheme for silicon-based PV module total recycling. through a chemical process, the materials located inside each cell (silicon and copper) are recovered. Silicon is a critical raw material that is difficult to completely recover because it is printed in copper circuits in the PV cell and not in a pure state, and it is 'doped' by chemical additives. Therefore, in order to be able to free it, it is necessary to resort to hydrometallurgy processes (to date, they are still particularly expensive). Hydrometallurgy is a process of extracting metals from minerals by dissolving minerals in an aqueous phase and subsequently recovering the metal. Compared to other commonly used techniques, this process has the advantage of being selective, being economical and having a low environmental impact. However, for the complete recyclability of the PV module, its recovery is fundamental. Adopting the logical scheme above for a very common standard PV module of 21 kg, we can obtain: 15 kg of glass; 2.8 kg of plastic material; 2 kg of aluminum; 1 kg of silicon powder; and 0.14 kg of copper, as shown in Figure 10.  
The costs and benefits of recycling, especially when externality costs resulting from environmental pollution are considered, are of difficult estimation. By the quantification of the private and externality costs and benefits of recycling crystalline silicon (c-Si) PV panels, it is possible to evaluate the costs of recycling, as performed by [PERSON] et al. [24]. Table 3 reports the costs of recycling, the material value and the net profit for a standard PV module of 21 kg. In particular, the total cost of recycling [**c**] was obtained from the product of the weight material and the costs of recycling, and the total material value was the product of the weight and material value taken from the work of [PERSON] et al. The net profit was the difference between the total material value and the total cost of recycling.