Pure Electric Bus Traction Technology Overview - A Path Towards Enhanced Environmental Performance and Efficiency for Transit Bus Fleets 2014-36-0205

The growing concentration of population in world metropolis caused by increasing urbanization rates has pushed the demand for high capacity and efficient public transport systems. At the same time, environmental concerns have led to increasingly stricter emission standards. In this context, transit authorities have become strongly focused on making their bus fleets more efficient and cleaner, by incorporating new alternative fuels and clean propulsion technologies. This has led to increased interest in electric driven technologies, with their intrinsic efficient, quiet and environment friendly features. Trolleybuses, a well proven mature electric technology already adopted in some cities, although efficient and clean, are burdened by high infrastructure costs and operational inflexibility. Hydrogen fuel cell buses, an infant technology, currently on a precommercial status, still presents some hurdles on hardware durability and hydrogen supply, which need to be surpassed before reach commercial status. At the same time, there has been significant technical progress into development of the electromobility concept for transit bus systems, through the use of pure electric drivetrains supported by the improvement of range, durability, charging procedures and cost of energy storage systems - ESS (batteries or/and supercapacitors), considered the core components of the so called pure electric buses. In this scenario, pure electric driven bus technology has aroused interest of transit industry, as a strategy for improving efficiency and environmental performance of transit bus fleets. Although not yet commercially competitive with diesel buses, there has been significant technical progress in development of pure electric buses, notably with improvements observed in the so called Lithium Ion battery (with their variants), supercapacitors technology and charging procedures, both under a technical and cost perspective. This work is supposed to present an overview of pure electric traction bus technology, with a focus on technical, operational, environmental and economical features, highlighting the pathways to be followed to reach commercial feasibility in order to comply with stricter environmental targets already scheduled and consolidate the electromobilty concept for transit bus industry. Moreover, it will be presented an overview of the main ongoing electromobility bus experiences in some important cities around the world.