Carbon Payback Time (CPBT) and Energy Payback Time (EPBT) of Residential Solar Photovoltaic Repowering

As new photovoltaic (PV) technologies with better performance and lower prices are available in the market, the older modules with lower efficiency will likely be replaced much before the completion of their operational life (i.e., 25-30 years). However, before large-scale implementation of PV repowering, a better understanding of the environmental impacts and economic performance of various repowering scenarios is required. In this work, carbon and energy payback times of three PV repowering scenarios of a 3 kW residential PV system installed in Detroit, Michigan are evaluated. The considered technologies are Multi-crystalline Silicon (Multi-Si), Bifacial Passivated Emitter and Rear Cell (PERC), Perovskite Silicon-tandem (PST), and Tunnel Oxide Passivated Contact (TOPCon) PVs. CPBTs of the considered PV types ranged from 7 months to 13 months, while the EPBTs ranged between 4.5 and 7.4 months. These two-energy metrics of emerging technologies like TOPCon with high efficiency are expected to decrease as technologies mature. The annual electricity generation (237.28 kWh per m²) over 30 years of the repowering time is highest when modules are replaced every 10 years.