Low Carbon Charging Schedule of Electric Buses: Case Study in Denmark and Japan

This study examines regional differences in time-varying carbon dioxide $(\text{CO}_{2})$ emissions from power systems in Denmark and Japan, influencing on the low-carbon charging schedules of electric buses in public transportation systems. The time-varying $\text{CO}_{2}$ emissions differ significantly due to variations in the penetration rates of variable renewable energy (VREs) sources, particularly wind power. Numerical experiments reveal that under an optimal charging schedule, total $\text{CO}_{2}$ emissions in Denmark are 81% lower in summer and 71% in winter compared to Japan when chargers are available only at their depot. Additionally, distributing chargers across all bus terminals ensures the feasibility of transportation in winter. Furthermore, distributed chargers at bus terminals have potential to reduce emissions by up to 4% further by expanding the flexibility of charging times to align with VRE utilization throughout the day. This international comparison highlights the critical importance of optimizing charging schedules in high VRE penetration systems, where $\text{CO}_{2}$ emissions exhibit significant daily fluctuations.