Mercedes-Benz Hybrid Bus awarded 2008 DEKRA environmental prize

By: Chris Smith

At the World Mobility Forum the Mercedes-Benz Citaro G BlueTec Hybrid urban bus was presented with the 2008 DEKRA environmental

At the World Mobility Forum the Mercedes-Benz Citaro G BlueTec Hybrid urban bus was presented with the 2008 DEKRA environmental award.

Clemens Klinke, Chairman of the Board of Management of DEKRA Automobil GmbH, presented the award to Andreas Renschler, member of the Daimler AG Board of Management with responsibility for Daimler Trucks & Daimler Buses, commenting that: "We have awarded the 2008 DEKRA environmental prize for this bus-drive technology because it makes an innovative and lasting contribution to the quality of life of our urban population".

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 environmental protection. During the award ceremony Andreas Renschler responded: "The hybrid bus is part of our "Shaping Future Transportation" initiative for a clean environment. With sales of 2600 hybrid buses to date by its Orion brand in America and Fuso in Japan, Daimler is the world market leader in this sector.

"With the Mercedes-Benz Citaro, we are now also able to offer pioneering hybrid technology for the demanding European market," said Renschler.

According to DEKRA, the jury consisting of environmental and transport scientists, as well as specialist journalists, not only expressed their recognition of the Citaro Hybrid with this award, but also of the many decades of work by the Research and Development department at Daimler AG.

"Since 1969 Daimler has repeatedly set milestones on the road to realising diesel-electric public-transport buses, and has now once again developed the right hybrid vehicle for the European market".

The Mercedes-Benz Citaro G BlueTec Hybrid is equipped with a technologically highly sophisticated, serial hybrid-drive system which uses electric wheel hub motors. It is capable of emissions-free operation under battery power alone over short distances. The diesel engine does not operate as a drive unit, but instead powers the generator to produce electricity as required. Accordingly, the diesel engine has no mechanical connection to the drive axles.

The generated current is stored by maintenance-free lithium-ion batteries, which are installed on the roof of the Citaro. The batteries are not only charged by the diesel generator, but also by energy obtained during braking, in a process known as recuperation. The power is transferred to the wheels of the Citaro Hybrid by four 80 kW electric wheel hub motors at the centre and rear axles.

The energy recuperated during braking is used both to power the vehicle when at standstill and when moving off. When approaching a bus stop, at standstill and when accelerating away from the stop, the hybrid bus is able to operate under electrical power alone, and therefore with practically no emissions - which also means a significant reduction in noise and fuel consumption.

The Mercedes-Benz Citaro G BlueTec Hybrid will shortly be entering field trials with public-transport operators. This is linked to a further ambitious goal: the aim is to realise a diesel-electric, hybrid urban bus which is cost-effective for the operator. Owing to the still very small production volume, the cost-effectiveness threshold has not yet been reached despite fuel savings of up to 30 percent.

In addition to further advances on the part of manufacturers, the decisive factor for the success of hybrid vehicles will be the willingness of the public to acknowledge or incentivise the ecological added value of the concept. The success of alternative drive technologies in the USA and Japan, where they are publicly subsidised, confirms this; however in Europe transport operators still lack this basis for decision-making.

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