Optimal Public Electric Bus Fleet Charging Schedule with Solar and Energy Storage Considering Static and Dynamic Route Assignment

Abstract

This paper presents a mathematical model to optimize the depot charging of a transit electric bus fleet given route schedules. The total cost of electricity drawn from the power grid is minimized in the presence of solar (PV) generation and an energy storage system (ESS). A mixed-integer linear program (MILP) is proposed that allows for static bus-route pairs as well as more flexible and dynamic assignments of buses to routes. The models are tested on data from a transit agency in Santa Clara County, California, including time-of-use (TOU) grid prices, vehicle specifications, and solar generation capabilities. Results show both models achieve full solar utilization and consume less power during peak hours. Dynamic route assignment achieves an 11% reduction in operational costs and performs over a range of parameters based on sensitivity analysis. Furthermore, the results demonstrate the effect of weather on operational costs and other operational strategies.