Shared Charging Strategies at the Electric Bus Depot: A Robust Optimization Model

Reservation-based shared charging (R-SC) at bus depots leverages underutilized daytime charging capacity to support private electric vehicle (EV) users while generating additional revenue for bus operators and improving the overall utilization of electric buses (EBs) charging infrastructure. The key challenge, however, is managing the competing charging demands of private EVs without compromising charging reliability and operational needs of EBs. This study introduces a robust optimization modelling framework to schedule same-day EB charging while managing private EV charging demand, accounting for uncertainties in the EB power consumption. Two strategies are proposed to manage the demand of EV charging: a hard charging window with fixed pricing, and a soft charging window with variable, differentiated pricing. Numerical experiments demonstrate that R-SC significantly outperforms the first-come-first-served (FIFO) baseline in terms of economic performance and resource utilization. The soft charging window strategy, especially under high EV demand, enhances charging flexibility and increases the overall utilization of depot charging resources. Additionally, time-of-use pricing further strengthens the robustness of the proposed model. These findings have practical implications for managing shared charging facilities, and the modelling framework offers a valuable tool for designing resilient and efficient allocation strategies for shared charging.