 | | | Stopping, waiting and starting at the bus stop with zero emissions |
| When approaching the bus stop, while waiting or when accelerating away from the stop, the hybrid bus can run purely on electricity and operate with virtually no emissions, including a significant reduction in noise. |
Downsizing is one of the biggest advantages of the engineering in the ultra-sophisticated serial hybrid in Citaro: instead of employing the large-volume OM 457 hLA R6 cylinder with twelve litres displacement which is usually found in articulated buses, the hybrid bus uses the compact OM 924 LA. It produces 160 kW (218 hp) of power from 4.8 litres displacement. Thus the engine weight is decreased from around 1000 kg to only around 450 kg.
As the diesel engine in the Citaro Hybrid is not used as a drive unit, it does not have to produce its maximum output and can operate close to optimally in a very economical and environmentally friendly way within a narrow rpm range. That is why the engine’s torque characteristic curve has been optimised for low emissions and fuel consumption to match with the semi-permanent operating method of the hybrid bus.
The Citaro with hybrid drive also has no need for a traditional automatic transmission, thus improving its efficiency while simultaneously reducing its weight. The auxiliary units are also optimised: the refrigerant compressor, power steering pump and compressed air compressor are no longer powered by the combustion engine through belts or gear wheels but individually through an electric engine.
This brings about improved efficiency as all these units can be powered only when they are needed. Due to their electric power, the auxiliary units can be positioned almost anywhere, for example on the roof of the bus. The Citaro is the leader worldwide in terms of consistently optimising these auxiliary units.
The powertrain engineering of the Citaro Hybrid is not only technically demanding but also allows a new layout in the interior. As transmissions and the differential are no longer an issue and there is no rigid connection between the individual units, other possibilities open up in terms of designing the passenger compartment at the tail end of the urban public transit bus. The total height needed for the vertically built-in engine, despite the tower construction, is so low that the panelling over the engine can serve as a luggage rack for passengers. Due to the downsizing of the units, the additional weight of the Citaro Hybrid, at around one ton, is low in comparison to that of a traditional diesel-driven articulated bus.
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Models
