Optimization Model Estimated Battery Electric Bus Charging Infrastructure Cost for 15 Bus Routes in Washington at $10.1 Million.

With the progress in battery technology, battery electric buses (BEB) are emerging as potential practical solutions for sustainable urban transportation. However, the transition from traditional to BEB fleets requires efficient planning for BEB charging infrastructure. In contrast to on-base charging stations, on-route fast charging stations pose distinct challenges related to safe operation and power supply capacity, making it more difficult to manage grid operational costs. This study presented a framework that integrated the bus route network and the power network, leveraging their interdependence to improve the planning outcomes of on-route BEB charging stations in South King County, Washington. The study used an optimization model with the goal of minimizing overall planning costs, which included investments in charging equipment, power facilities, and grid operation.

The study used an optimization model to estimate the total infrastructure costs of building on-route charging facilities for a BEB network for 15 bus routes in South King County, Washington assuming a 10-year planning period. When the initial state of charge (SOC) of the battery, indicating the remaining quantity of electricity available in the battery, was set to 10 percent, the total cost was $10.1 million, of which $5.40 million covered the charging station investment, $1.13 million for charging pile investment, $3.16 million in power line investment, and about $437,000 in power loss cost. The costs decreased with increasing SOC levels. Notably, when the initial SOC was set to 40 percent, the total cost decreased more than 90 percent compared to the total cost calculated for 10 percent initial SOC, and the total number of on-route charging stations decreased from 27 to three stations. At 40 percent SOC scenario, the power line investment became zero since the three charging stations were built directly on the power nodes, eliminating the need for extra power lines to connect the stations to the power grid. The results also indicated that when the SOC exceeded 50 percent, there was no need for on-route charging for the 15 BEBs, since the fleet was able to complete a round trip without the need for on-route charging.