Synergistic optimization of thermal and electrical energy storage for zero-emission electric buses

In winter, the operation of cabin heating systems in battery electric vehicles could significantly decrease battery lifespan and driving range, due to extended cabin warm-up time and substantial energy consumption increase associated with maintaining a comfortable cabin temperature. These pose a notable challenge to the overall performance and practicality of battery electric vehicles in cold climates. To address this challenge, thermal energy storage, particularly, the integration of a metallic phase change material-based thermal energy storage device is proposed to extend the driving range and reduce the cabin warm-up time during cold start. An energy storage system sizing framework based on a detailed battery electric bus simulation model incorporating this approach was developed. Based on real-world driving data, an optimal energy storage system configuration was obtained as 318.8 kWh of battery and 86.5 kWh of thermal energy storage. Using these devices for heating, the cabin warm-up time was found to be reduced by up to 68.3 % and the battery service life could be extended by 13.8 %, leading to an annual operating cost reduction by 7.8 %. This study demonstrates the significant improvements of electrical bus performance through the integration of thermal energy storage with battery electric buses.