Charging electric buses with solar power under varying environmental temperatures and sunlight conditions

It has been widely acknowledged that electric buses (EBs) can offer a lower-carbon, more cost-effective solution for mass transit services than conventional diesel buses. Recent advancements in the photovoltaic (PV) technologies have stimulated and increased the deployment of photovoltaic-storage-charging (PSC) stations, enabling EBs to transition toward a near zero-carbon transportation mode. Furthermore, PSC stations enhance system efficiency by storing PV-generated electricity and dynamically regulating electricity flow in response to the charging demand of EBs and time-of-use (TOU) variations in electricity prices. However, the operations of both EBs and PV panels are highly sensitive to their surrounding environment, where environmental temperature and solar irradiance may be the most influential factors causing substantial variations in charging cost and behavior of EBs across different regions and weather conditions. In this paper, the charging schedule and operational cost of an EB fleet (consisting of 128 buses) powered by a PSC station network (consisting of 18 stations) are derived by a mixed integer linear programming model for different temperature and sunlight variation scenarios. The optimal charging schedules determine not only the charging times, charging locations, and amounts of electricity charged to EBs, but also the electricity allocation scheme within each PSC station, including PV-generated and grid-supplied electricity, as well as PV-to-grid electricity. A comparative analysis of the performance of the EB-PSC system is conducted across different scenarios that are formed by placing it in six Chinese cities with different climate and geographical features over four distinct seasons. The results indicate that the use of PSC stations leads to a reduction of 10–15% in the annual operational cost in all the cities, demonstrating the appealing economic competitiveness of EB-PSC systems. The findings also reveal that environmental factors lead to substantial variations in the charging cost, with the highest cost being nearly 150% greater than the lowest, where environmental temperature is identified as a more significant contributing factor to the operational cost of EB-PSC systems than sunlight intensity.