Energy-economy-environment evaluation of building-integrated photovoltaic considering facade factors for representative megacities in China

Although urban high-rise building facades receive less solar irradiance than rooftops, their potential energy output remains substantial owing to their larger areas. This study conducts a comprehensive energy-economy-environment (3E) evaluation of building-integrated photovoltaic (BIPV) potential in ten megacities located across China's typical climate zones, coupled with discussions about the synergism between BIPVs and electric vehicles (EVs) for urban sustainability. The analysis indicates that BIPV systems, including both rooftop photovoltaic (RPV) systems, followed by south-facing facade photovoltaic (FPV) systems, can make a significant contribution to urban electricity supply. Specifically, RPV systems can provide 29.10 % of a city's electricity demand. Furthermore, FPV systems are critical infrastructures in cities with low BIPV contributions, boosting the generation potential by 59.77 %. The combined RPV and FPV system is shown to reduce urban CO₂ emissions by 35.50 %, having a net-negative emission in some cities with high solar irradiation values. This study also finds that integration with EVs is a strategy to optimize energy use and reduce the waste light rate, particularly in cities with high BIPV potential. Systems with the highest BIPV generation potential can consume 9.78 % of the excess electricity. This study calls for policy support, market promotion, and technological innovation to enhance the adoption of BIPVs. The findings suggest that combining BIPV and EV to form a BIPV-EV system is a promising pathway for cities in China to achieve energy efficiency and carbon reduction goals, highlighting the need for a multi-dimensional approach aligned with policy, technology, and market dynamics.