Citaro Hybrid Bus Wins 2008 DEKRA Environmental Award


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).


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