Selective delamination by milling as a first step in the recycling of photovoltaic modules

The recycling of photovoltaic modules has been a topic of increasing interest over the last years. At industrial scale, delamination of the module structure, which represents the first step in the recycling process, is currently achieved by multi-stage crushing. However, the quality of the outputs obtained through subsequent processing is low and offers room for improvement. Milling was investigated as an alternative physical delamination method. Lab-scale experiments were conducted to evaluate the applicability of the technology in general, as well as comparing a process by which all non-glass layers are removed at the same time (one-step) with one where the backsheet is removed as a separate fraction (two-step). Furthermore, a qualitative and quantitative analysis of the resulting outputs in each case was performed. Results show effective delamination by the milling process. Advantages in comparison to the currently used delamination techniques are identified in regard to the quality of the recovered glass, which is separated directly during delamination as well as the fact that the subsequent processing can therefore be focused on the polymers, metals and silicon contained within the removed materials. Some possibly problematic aspects in regard to upscaling have also been identified and discussed. While the two-step process enables the recovery of more homogenous outputs, it is also associated with a higher effort regarding input characterization and the milling process itself. In order to reach a conclusion about which process option is more feasible, additional investigations concerning the milling process, the input material and the output fractions are needed.