title: Assessment of the ecological lifetime of photovoltaic systems considering aging effects, end-of-life and early replacement
Creators: name: Herceg, Sina
Publisher: name: UNSPECIFIED
Year: 2024

description: Photovoltaic (PV) systems are crucial for a clean energy transition. Still, their massive deployment in the coming years will consume significant amounts of energy and resources. Emissions from the production of solar energy systems have been constantly decreasing in the past years. However, not only production emissions but also factors like lifetime and energy yield are decisive for the life cycle environmental impact of PV electricity. Previous Life Cycle Assessment (LCA) studies focus
mainly on the quantification of primary energy and resource use during PV production, whereas their use and end-of-life phase and the regarding impact on the overall environmental performance of PV electricity are rarely investigated. For example, aging and degradation during use phase which can be strongly dependent on site-specific conditions like a corrosive atmosphere, are affecting the systems lifetime and therefore its environmental footprint. Further, the end-of-life treatment of PV modules is gaining relevance for quantifying the emissions of PV electricity due to increasing 
amounts of PV module waist in the coming years. Hence, to assess the emissions over the whole life cycle of a PV system it is important to also be able to quantify the aforementioned impacts since they can have a strong effect on its overall lifecycle emissions.
This work aims to investigate the environmental impact of PV systems throughout their lifecycle, addressing the research gaps identified above. The influence of performance degradation, end-of-life (EoL) treatment as well as actual operational time on the environmental footprint of PV electricity and therefore the optimal ecological lifetime of PV systems is assessed using LCA methodology. 
Three sub-questions are explored in separate peer-reviewed journal articles: 1) The impact of different recycling approaches for PV modules, highlighting the potential for improved environmental performance with dedicated recycling technologies. 2) The influence of regionalized degradation patterns on greenhouse gas emissions from PV electricity, revealing location and temperature dependent variations in emissions. 3) The calculation of the earliest and the optimum point to maximize the ecological benefits of early PV system replacement (repowering), emphasizing the 
benefits of repowering when combined with recycling and increased peak power.
The results show that all the mechanisms under study can significantly influence the life cycle environmental emissions of a PV system. For example, dedicated recycling can reduce CO2-emissions by up to 4%, despite the higher efforts for waste treatment. Also, using non-linear degradation rates instead of a linear degradation rate of 0.7% results in a variation of up to -4 % to +6 % in CO2-emissions per kWh of produced electricity. Moreover, in regions where climatic stressors like temperature, humidity and corrosion are high, the CO2-emissions per kWh almost double when climate-specific degradation rates are used. Finally, it could be shown that the premature replacement of PV-modules can be environmentally beneficial under certain conditions, 
especially in combination with dedicated recycling. 
By using the results from all three studies, the assessment of PV life cycle emissions is improved and, in doing so, PV deployment strategies can be optimized. Future research should focus on integrating the here presented methodologies and results, enabling site-specific quantification of PV system life cycle emissions and the development of improved end-of-life management strategies to enhance sustainability.