Hybrid technology
Citaro hybrid

Hybrid technology

The base function of the new Citaro hybrid is very simple: the disc-shaped and very robustly constructed electric motor is integrated between the combustion engine and automatic transmission. Amongst other things, it works as an alternator during the deceleration of the bus and converts coasting energy into electricity – when braking and when the driver removes their foot from the accelerator. The generated power is stored as electrical energy. Without hybrid technology this energy gained in the recuperation phase would be lost – the new Citaro hybrid uses it and therefore saves: as soon as the bus pulls off, the electric motor supports the diesel or gas engine with additional torque – the so-called boost phase. In this way the combustion engine momentarily has to provide less output when pulling away and therefore saves fuel. In addition, the electric motor provides support during idling. This improves the efficiency of the combustion engine and contributes towards a significantly reduced fuel consumption and therefore reduced emissions.

The electric motor does not serve to increase the maximum power. That's why the output and torque of the new Citaro hybrid remain unchanged compared to a combustion-engine vehicle of the same type and rating. The engine speed of the combustion engine is not reduced in the boost phase. Only the peak performance is imperceptibly reduced and enhanced by the electric motor.

The interplay of combustion engine for the base load and electric motor for peak loads ensures a high level of energy efficiency of the drive system when driving. The components designed for greatly varying loads are constructed in a very robust manner. Their high durability is comparable with those of conventional combustion-engine powertrains. The electric motor is water-cooled, outputs up to 14 kW and can provide a torque of up to 220 Nm.

A contribution towards increased economy is also made in the new Citaro hybrid by the new, efficiency-optimised fuel-efficient axle: on the one hand, by fuel savings resulting from the lower rolling resistance and on the other by less maintenance work and an increased maintenance interval – from 180,000 to 240,000 km. The acoustically improved portal wheels additionally ensure even quieter operation.

Its electronics convert the electrical energy stored as direct current into alternating current for powering the electric motor. Its space-saving water cooling ensures a high level of operating safety.

With its high power-to-size ratio, the innovative supercaps use condenser technology to store the electrical energy from and for the electric motor, saving space and doing so safely. They are designed for the continuous, quick change between charging and discharging in a typical urban bus cycle and have a high level of durability.

The increased energy efficiency in the new Citaro hybrid is also aided, as standard, by the new electrohydraulic steering "intelligent eco steering". It works on a requirements-oriented basis and also contributes towards reduced fuel consumption in urban regular-service bus operations.

* Not for low entry variants.