Bus’ system electrification review – A technological operational comparative assessment 2018-36-0095
Despite the recent groundbreaking improvements in diesel engine technology, with its inherent improved emission performance (Euro VI, US 2010 and their equivalences), it is well known that there is a limit on cleaning diesel buses. At the same time, cities and transit operators have been permanently challenged for seeking for traction technologies to comply with the emissions’ reduction agenda. In this context, electric bus traction technologies appear as a promising alternative for cleaning the bus’ fleets, with their intrinsic potential to reduce environmental impacts caused by public transport, such as greenhouse gas and local pollutant, as well as noise emissions. Moreover, the use of electricity also contributes to reduce the transport system’s dependency on fossil fuels and their inherent price volatility. From an operational perspective, it is required that alternative bus' traction technologies comply with diesel bus performance, in terms of costs, technological maturity, operational reliability, refueling times and infrastructure requirements. This, in some way, has challenged regulatory authorities and operators with the conflicting objectives of shifting to zero emission vehicles, while keeping the required operational performance and flexibility, as well as the costs under the limits imposed by fares and/or public budgets. In this scenario, electric driven traction technologies, like trolleybuses, hybrid-electric, fuel cell, battery and ultracapacitor buses, each one with their own strengths and weaknesses, appears as candidates for the electrification of bus’ fleets. This work is supposed to present an overview of electric bus tractions alternatives into a technological and operational comparative perspective, complemented with some examples of international operational experiences.