Mercedes-Benz Hybrid Bus with Four Electric Wheel Hub Motors in Operation
2009-04-01 - Mercedes-Benz announced that it has put into operation the Citaro G BlueTec Hybrid articulated bus for the first time. As a result of using the largest lithium-ion vehicle battery for emission-free driving, the 18-metres long city bus reduces diesel consumption by up to 30 percent. The battery stores the energy from the diesel generator and the electrical energy recuperated during braking.
The hybrid bus features a serial hybrid drive system which allows emission-free driving under battery power alone over short distances. The drive system is installed in an articulated Citaro G bus, and drives the centre and rear axles by means of four wheel hub motors. The diesel engine in the serial hybrid bus does not act as a primary drive unit, but rather drives the generator to produce electric power as required. This energy is stored by lithium-ion batteries mounted on the roof. The batteries are not only fed by the diesel generator, but also with energy recuperated during braking. The energy generated by recuperation when braking on the approach to bus-stops or traffic lights is used both to supply the vehicle at standstill and when moving off. This means that the hybrid bus is able to operate purely under electric power, and therefore practically without emissions, when stationary and under acceleration - with a significant reduction in noise as well.
The battery system generates 180 kW and is comparatively light in weight at less than 350 kilograms. Power is transferred to the wheels of the Citaro G BlueTec Hybrid by four electric wheel hub motors on the centre and rear axles. The total output of the wheel hub motors is 320 kilowatts. Instead of the large, twelve-litre six-cylinder in-line engine normally employed in an articulated bus, a more compact unit with a displacement of 4.8 litres is used. According to the company, the engine weight is reduced from around 1000 kilograms to around 450 kilograms.
The new hybrid bus has successfully completed extensive practical trials over recent months, including several weeks of winter trials under tough operating conditions near the Arctic Circle. The first vehicles will be delivered to the transport operators before the end of this year.
Author(s): Bettina Merkelbach
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