Battery capacity and recharging needs for electric buses in city transit service

Abstract

This paper evaluates the energy consumption and battery performance of city transit electric buses operating on real day-today routes and standardized bus drive cycles, based on a developed framework tool that links bus electrification feasibility with real-world vehicle performance, city transit bus service reliability, battery sizing and charging infrastructure. The impacts of battery capacity combined with regular and ultrafast charging over different routes have been analyzed in terms of the ability to maintain city transit bus service reliability like conventional buses. The results show that ultrafast charging via frequent short-time boost charging events, for example at a designated bus stop after completing each circuit of an assigned route, can play a significant role in reducing the battery size and can eliminate the need for longer duration charging events that would cause schedule delays. The analysis presented shows that significant benefits can be realized by employing multiple battery configurations and flexible battery swapping practices in electric buses. These flexible design and use options will allow electric buses to service routes of varying city driving patterns and can therefore enable meaningful reductions to the cost of the vehicle and battery while ensuring service that is as reliable as conventional buses.

Analysis of the Reduction of CO2 Emissions in Urban Environments by Replacing Conventional City Buses by Electric Bus Fleets: Spain Case Study

“…Gao et al estimated the power of auxiliary systems on series and parallel hybrid buses as being 2.29 kW [50], with 3.75 kW for electric buses [51], as opposed to Göhlich et al, who found power consumption of 6 kW for the auxiliary systems [52].…”

Conceptual Design of Urban E-Bus Systems with Special Focus on Battery Technology

“…Rogge et al (2015) further discussed the trade-off between passenger and battery capacity and the interdependency between charging power and battery capacity in order to electrify an existing bus network. Battery sizing is investigated in Gao et al (2017). 1 Fuel cell powered busses are not considered in this study because the cost of the required infrastructure and the current market price of hydrogen is not yet competitive.…”

Assessing life cycle impacts and the risk and uncertainty of alternative bus technologies

“…where ηch is the BEB charging efficiency, 97% [64], GHGWTT is the WTT GHG emissions factor (gCO2e/MJ) and GHGTTW is the TTW GHG emissions factor (gCO2e/MJ) ( Table 5). For the BEB configuration, ηth = 100% in equations 8 and 9.…”

“…[73]. b Sum of clutch, gearbox, final drive and wheel efficiencies from [64]. c Traditionally in TIF studies, percentage deviations from the baseline are used, this study also includes variability of inputs applicable to BEBs only.…”