A review of Bus2Grid applications in electric bus systems

Abstract

Countries around the world are currently striving towards carbon neutrality, requiring the energy and transportation systems to undergo a major transformation. Vehicle-to-Grid (V2G) technology Enables Electric Vehicles (EVs) to feed electricity back into the grid, allowing the energy stored in their batteries to be discharged when the vehicles are not in use. Most current research focuses on private electric vehicles, as their owners can potentially earn additional income while contributing to grid stability. However, private EVs have highly dispersed ownership, no fixed routes, and their parking time is short and fragmented, making it difficult to coordinate and aggregate them to provide large-scale and reliable power supply to the grid. This review argues that electric bus depots, with their large-scale charging infrastructure, are the most suitable targets for implementing V2G. Buses have fixed schedules for departure, and during off-peak hours or at night, large numbers of buses are typically parked at depots and can be centrally managed by bus operators. Operators can therefore determine when batteries are available for grid services and estimate how much electricity can be sent out in advance, making scheduling considerably easier. This paper reviews the basic technologies required to implement V2G at bus depots, including charging stations, communication networks, and control systems. It also explains why bus depots are particularly suitable as distributed energy resources, primarily because they have substantial aggregate battery capacity and operators can accurately identify periods when buses are idle and available for grid services. Finally, this review synthesises academic research and real-world project outcomes, summarising current knowledge and identifying key areas requiring further investigation to enable bus depots to play a greater role in the transition to clean energy.