Replace or retain? Timing PV panel replacement for maximum life cycle carbon savings

Abstract

Driven by innovations in cell materials and manufacturing techniques, photovoltaic (PV) technology has advanced rapidly, with panel efficiencies increasing from around 5-10% to over 25% in recent designs. These efficiency gains raise questions about optimizing the replacement of PV panels in a system as they degrade; could upgrading an older, less efficient panel provide environmental benefits even if it hasn't reached its full lifespan? This study investigates the optimal timing for PV panel replacement by examining the embodied and operational trade-offs between maintaining panels until their technical end of life and upgrading to high-efficiency panels earlier. We develop a parametric model that assesses embodied impacts, carbon payback times, and the impact of the regional electricity grid's carbon intensity for two types of PV panels: monocrystalline and Cadmium telluride. Results reveal threshold conditions where early replacement aligns with carbon reduction goals. A case study of a residential building in Switzerland with full building-integrated PV coverage provides insights into real-world applications. The findings provide a framework for policymakers and industry stakeholders to make informed decisions on PV replacement, balancing carbon payback across scenarios. This approach enables a strategic use of PV technology, aligning decisions with long-term sustainability goals.