The Citaro bus, developed by Daimler AG's Mercedes-Benz division, is pretty high-tech as far as urban buses go. It's a series-hybrid, meaning that the diesel engine generates electricity instead of mechanically driving the wheels. This design means that in the future it would be relatively easy to replace the engine with a hydrogen fuel cell, thus making the bus completely zero emissions at the source. But even without a fuel cell, the specifications are pretty good.
For now, the main power source is a downsized 4-cylinder, Euro 4 compliant, diesel engine of 4.8 liters producing 218 horsepower (160 kW) at 3,200 rpm. "This replaces the 12-liter in-line six-cylinder engine of conventional articulated buses. As a result, the engine weight is reduced from around 1,000 kg (2,200 pounds) to 450 kg (992 pounds) or so. [...] The hybrid-drive Citaro also dispenses with a conventional automatic transmission, resulting in further weight savings and improved efficiency. The downsizing of the drivetrain components means that the weight penalty of the Citaro hybrid bus over a conventional diesel-powered articulated bus is only around one tonne." (!)
The electricity generated by the diesel engine and regenerative braking is stored in a lithium-ion battery located on the roof. It has a 19.4 kWh capacity, and drives four 80 kW electric wheel hub motors on the center and rear axles of the vehicle (total output: 320 kW).
Daimler anticipates that the hybrid will offer 20% to 30% lower fuel consumption than conventional diesel Citaros.
The Citaro hybrid bus will shortly enter field trials with public-transport operator; a small production series is planned for 2009.
Daimler is the top-seller of hybrid buses in the world at this point, with sales of some 2,600 hybrid buses to date by its Orion brand in the US and Fuso in Japan.
The DEKRA environmental prize is oriented towards the principle of sustainability and is awarded to projects, measures or initiatives which make a far-reaching and innovative contribution to protecting the environment. The assessment focuses on mobility, in particular improving the transportation of people and goods.
See also: ::More Cities Jumping on the Hybrid Bus Bandwagon, ::Seen in New York: Clean Air Hybrid Electric Bus, ::Facing Smog and Sluggish Traffic, Beijing Upgrades Its Public Bus System, ::London Plans for Hybrid Bus Expansion, ::Popularity of Public Transportation Increasing in US