Joint Optimization of Vehicle Battery Pack Capacity and Charging Infrastructure for Electrified Public Bus Systems

Abstract

Although electric buses operate at lower noise levels and without direct emissions, only a small fraction of bus fleets in the world is electrified due to the high investment associated with the battery systems of the electric vehicles and the required charging infrastructure. To make the cost of electrification more competitive, the design of the battery pack and the charging infrastructure should be optimized for the specific operating conditions. In this article, a method is presented, which minimizes the total cost of ownership of the electric bus fleet by choosing the optimal battery size, number of charging stations, and charging power for a given schedule, vehicle characteristics, and environmental conditions. The method serves as a decision-making aid for automotive engineers in the early vehicle design process and/or for urban transit agencies to select appropriate vehicle models. Implementation of the method in a case study showed that the optimization can reduce the costs that are influenced by the battery and charging infrastructure by 22.8%, compared to the reference vehicle and the charging configuration of the pilot project. This is mainly attributed to the reduced battery pack capacity and the higher utilization ratio of the charging infrastructure.