A Multi-objective Framework for Assessment of Recycling Strategies for Photovoltaic Modules based on Life Cycle Assessment

Abstract

This work assesses the environmental benefits of including the recycling strategies for PV modules at the earlier design stage of PV grid-connected systems (PVGCS) considering simultaneously techno-economic and environmental criteria. First, two case studies from dedicated literature have been selected based on the availability of the life cycle inventory, i.e., recycling of PV modules of crystalline silicon (c-Si) and cadmium telluride (CdTe) technologies. Second, different scenarios have been formulated by varying the mix of virgin and recycled PV modules. Third, following an ecodesign framework, a bi-objective (Energy production versus Energy Payback time) optimization approach for the design of PVGCS encompassing the recycling stage has been developed to assess the formulated scenarios. The ecodesign methodology couples the life cycle assessment method with a PVGCS design model, which is then embedded in an external optimization loop based on a multi-objective genetic algorithm, i.e., a NSGA-II variant. For c-Si, the recycling strategy significantly reduces the EPBT (a factor of 1.8 is observed from the 100% virgin to the 100% recycled scenario) when considering an identical PV module efficiency and a significant decrease in Global Warming Potential (GWP), expressed in g CO2 eq per kWh, is also observed with a 20% reduction in the more extreme case. For CdTe thin film modules, the results confirm the environmental benefit when recycling of glass cullet and copper is considered. Although PV recycling modules are energy intensive, their implementation compensate for the energy used for producing virgin modules. This study confirms that the end-of-life management of PV modules must be thoroughly studied not only to determine the feasibility of the process but also to assess the environmental and economic benefits.