Utility-transit nexus: Leveraging intelligently charged electrified transit to support a renewable energy grid

The transportation sector is a major greenhouse gas emitter. Concurrent electrification of vehicles and investment in renewable energy sources (RESs) is required to mitigate these emissions. The introduction of intermittent RESs such as solar and wind at a large scale presents challenges to utility operators. This study quantifies the opportunity a Vehicle-to-Grid (V2G) Battery Electric Bus (BEB) fleet offers in overcoming these challenges. A Gumbi optimization model was developed to simulate the reaction of grid operators to changing load and production values by seeking the lowest operational cost at each timestep. The optimization model is integrated with a BEB energy consumption model. The two models interact to optimally maintain necessary charge for the BEB fleet and support the grid load. An Austin, Texas case study is analyzed to investigate the role of BEB charging in buffering sharp changes in RES production to help smooth power demands from traditional energy sources of coal, natural gas, and nuclear power. A V2G BEB smart charging (SC) scenario is compared in cost and emissions to a BEB charge-as-needed and a diesel bus scenario. Without any SC strategies, the total external cost of the electricity grid and bus emissions falls by 3.42%, and with SC strategies these costs fall by 5.64%. Further, with SC strategies, the utility manager saved 22% of their daily cost in this case study. Overall, the study provides practical avenues for jointly utilizing renewable energy sources and electric mobility alternatives.

Automated summary

The study quantified the opportunity that an electric bus fleet offers in overcoming challenges of renewable energy sources, and compared different charging strategies in terms of energy cost and emissions through an Austin case study.