Recovering critical raw materials from end-of-life multi-junction III-V/silicon solar cells

Abstract

This thesis studies the criticality of gallium, indium and silicon for a 1GWp production of III-V/silicon solar cells and assesses the environmental impacts and economic costs \& benefits of a recycling process for these solar cells. III-V/silicon is an emerging solar cell technology, that is expected to enter the market in between 2025 and 2035. It was found that gallium availability can become restrictive for large scale production of III-V/silicon cells, because the amount of high-purity gallium needed for an annual 1 GWp production of III-V/silicon cells (176.3 tons) is close to the entire 2019 world production of high-purity gallium (205 tons). It is therefore recommended to create additional high-purity refineries to refine low grade gallium to high-purity gallium. Moreover, in the long term, gallium can be recycled from end-of-life III-V/silicon cells. Various gallium recovery technologies from end-of-life products have been summed up from a literature review. One of them, an ethanol dilution process, is included in the flowchart of a recycling process for III-V/silicon solar panels. The environmental impacts of the recycling process are compared to the cradle-to-gate impacts of the production of the panels, by performing a life cycle assessment (LCA). The impact categories where the recycling process scores high are climate change, marine eutrophication, freshwater ecotoxicity, fossil resource depletion and ozone layer depletion. A suggestion to reduce the climate change impacts is to recycle the waste plastic that comes from the EoL panels, instead of incinerating this plastic. Finally a cost-benefit analysis (CBA) is performed. The CBA shows that recycling gallium, indium and silicon from 1GWp end-of-life III-V/silicon cells is likely to be profitable. With a product lifetime of 25 to 30 years, recycling is assumed to be profitable starting in the timeframe 2050-2065.