## 4 Results and Discussion  
### PV Panels LCA  
To operate with LCA results performed for different system boundaries and functional units, we used data only from the sources where the results were given in physical units (not in dimensionless points). For this reason, the analysis did not include the results of studies where environmental impact assessments were presented in normalized values (e.g., [16; 68; 69; 70; 71]). Additionally, because recycling technologies are rapidly progressing, we selected for comparison only the results of the decade. Table 2 presents the results of a comparative analysis of the photovoltaic plant's life cycle. The results of LCA in [41] were calculated according to the ReCiPe endpoint method with GaBi software. The functional unit was 1 kg of silicon-based PV waste modules. The study considered two types of PV modules (multi- and monocrystalline silicon modules) and several end-of-life treatment scenarios: landfill, incineration, and thermal, chemical, and mechanical recycling. In the case of recycling, the system boundaries included manufacturing, installation, operation, recycling, and reuse of recycled materials in a new cycle of manufacturing. One of the notable features of the study was a separate analysis of the transportation phase. In this case, the impacts do not depend on the recycling technology but the waste collection system and distance from it. The environmental effects of transporting used modules to the place of recycling or disposal were taken into account in two ways: (1) assuming a transportation distance of 50 km; (2) assuming a transportation distance of 100 km (for the case of recycling only). Modeling results showed that transportation for 50 km increases impacts on human health up to 2.1-2.3 \(\times\) 10\({}^{-4}\) DALY in case of landfill or incineration, and up to 1-1.2 \(\times\) 10\({}^{-4}\) in case of recycling. Transportation for 100 km for recycling increases the impact on human health up to 1.6-1.7 \(\times\) 10\({}^{-4}\) DALY, which is comparable to the landfill or incineration indicators on site (without transportation). Similar results were obtained in two other categories of environmental impact. Transportation for 50 km increased ecosystem effects to 5.8-6.2 \(\times\) 10\({}^{-11}\) species-year in case of landfill or incineration and 3-3.5 \(\times\) 10\({}^{-11}\) species-year in case of recycling. Transportation per 100 km for processing increased the adverse effects up to 4.5-5.5 \(\times\) 10\({}^{-11}\) species-year, which offset all the positive effects of recycling compared to landfill or incineration. Thus, the results of this analysis demonstrate that the recycling plant should be at most 80 km away from a PV plant. Otherwise, landfill and incineration scenarios have lower impacts when considering human health and ecosystems. This is a critical practical conclusion for the eco-design of the energy system regarding the territorial location of PV-plants. Solar plants must be placed compactly in a relatively small radius from the processing plant, or they should be some kind of mobile recycling plant. In addition, it is essential to consider not only the distance but also the method of transportation. In [67], an LCIA is made for the recycling of c-Si and CdTe PV modules using both the cut-off and end-of-life approaches. Data were collected from several recycling companies in central Europe. The functional unit was 1 kg of used framed c-Si and unframed CdTe PV modules, but the final results were presented for 3 kW modules, mounted on a slanted roof. The life cycle impact assessment competed with the ILCD Midpoint 2011 method, but only six of the most relevant impact categories were taken into consideration. \begin{table}