Electrification of a bus system in a hilly city considering gradient impacts

Abstract

Electrifying a bus system in hilly cities is challenging, as the road gradient plays a significant role in vehicular energy consumption, influencing the configuration of bus fleet and the layout of charging facilities. In response, this study developed a data-driven large-scale simulation optimization model that explicitly considers the impact of road gradients, aiming to determine the optimal electric bus fleet and charging infrastructure deployment, with Hong Kong (a typical hilly city) as the study area. Results indicated that neglecting gradient characteristics would underestimate the system cost and life-cycle emissions. Meanwhile, when accounting for gradient impacts, the required number of charging stations and fleet size increased by 27% and 3%, respectively. Moreover, the spatial distribution of charging stations could be greatly influenced. Further scenario analysis indicated that charging speed and infrastructure costs are influential in shaping bus electrification strategies. The outcomes can be helpful for bus electrification in hilly cities.