(Invited) Recovery Of Silver And Silicon From EoL PV Modules

Abstract

Photovoltaic modules global expansion has been dynamic over the last 20 years and is on the verge of becoming massive with the necessary ongoing energy transition. This development raises legitimate concerns of i) raw materials availability and ii) handling of modules as a waste after their decommissioning. End of Life (EoL) modules are indeed a powerful source of critical raw materials that worth being fully exploited and optimized to reduce the demand on natural resources and energy (>50MWh/t of PC-Si) to produce fresh modules whilst addressing the matter of wastes. We shall know that 6 tons of natural resources are needed to produce one ton of PV-grade Si, and the share of critical material Ag for PV production accounts already for more than 13% of global consumption. However, EoL module recycling has been poorly developed so far, mostly because of the difficult delamination stage necessary to release precious metals and Silicon. Different approaches, involving shredding, machining, solvents, flashing light have been investigated by different institutes or companies to delaminate the module structure and recycle metals, but none of them successfully demonstrated the recovery at large scale, suffering from a lack of purity, efficiency or scalability. In this context, ROSI developed an innovative route coupling different key steps to produce Silver and Silicon at industrial scale by recycling EoL modules. In order to address the varsity of polymer structures in PV panels, a thermal process based on pyrolysis ensures a generic approach of delamination to convert 100% of polymers into gas, thus releasing cell fragments. A mild chemical etching step then achieves the full separation of Silver fingers from the surface of Silicon, avoiding the use of harsh chemicals generally used in the recovery of metals from electronic wastes. A dedicated sortation process finally allows to recover high purity glass, copper, Silicon and Silver as depicted in Figure 1.Based on the thermal behaviour of different mixes of polymers, pyrolysis process has been optimized to ensure the full conversion of polymers in gas whilst limiting thermal budget regardless of the initial composition of the PV module. This optimization phase will be presented and coupled with the mild wet etching technology developed to obtain silver fingers. Characterizations of recoveredmaterials will be presented, together with their high value applications. Figure 1