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Mercedes-Benz Citaro G Bluetec Hybrid Bus Given 2008 DEKRA Environmental Award

The Citaro G BlueTec Hybrid urban bus.

The Mercedes-Benz Citaro G BlueTec Hybrid urban bus was presented with the 2008 DEKRA environmental award at the World Mobility Forum in Stuttgart, Germany.

The Citaro G BlueTec Hybrid, announced in 2007 (earlier post), is a series-hybrid articulated bus featuring a downsized diesel engine as the genset to provide power for a 19.4 kWh lithium-ion battery pack located on the roof. The Citaro hybrid uses four 80 kW electric wheel hub motors on the center and rear axles of the vehicle, with total output of 320 kW.

The engine applied in the hybrid is a compact 4-cylinder Euro 4 engine with a cubic capacity of 4.8 litres and an output of 160 kW (218 hp) at 3,200 rpm with maximum torque of 810 Nm at 1,600 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 battery pack is recharged by regenerative braking as well as the 160 kW generator. 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. The aim is for the Citaro G BlueTec Hybrid to cover around half of a demanding inner-city route under electric power alone, without the diesel engine running.

Daimler anticipates that the hybrid will offer 20% to 30% lower fuel consumption than conventional diesel Citaros.

The Citaro hybrid bus will shortly enter field trials with public-transport operator; a small production series is planned for 2009.

Daimler is the top-seller of hybrid buses in the world at this point, with sales of some 2,600 hybrid buses to date by its Orion brand in the US and Fuso in Japan.

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 protecting the environment. The assessment focuses on mobility, in particular improving the transportation of people and goods. DEKRA selected ten projects from a long line-up of potential candidates and a panel of expert judges made up of environmental and traffic scientists and trade journalists.


Bob Bastard

A series hybrid configuration makes a lot of sense for a vehicle of this duty cycle. I would think it would also make sense for taxicabs in urban areas as well. This seems like it could provide a good testing environment for GM's E-Flex platform. Why not build some E-Flex Impalas for an urban taxi fleet using currently available battery's/supercaps? They wouldn't necessarily have to have much if any electric-only range at first.

Stan Peterson

Germans giving a German Bus company an award. Whoop-te-do. A diesel hybrid is nice but Gee Whiz is only Euro 4 complaint?. Why not say it has NO POLLUTION CONTROLS at all, and jsut belches siesel soot unabated into the air, since that is about the same thing!

Still improvoing fuel efficiency from about 2 mpg to 3 mpg is significant...

Gerald Shields

I wonder how this bus compares to GM's two mode Hybrid buses?


20 -305 Anticipated savings in 2009. We'll see.
As one would expect high daily hours the lower hourly running costs should translate to usefull fuel savings.
But would I be building this vehicle with a half sized engine unless it was viable? I dont think so.
Note 320 kw electric motors may be expected to provide increased tourque.

"Germans giving a German Bus company an award. Whoop-te-do."

On this point I'd like to add that I couldn't help but giggle a bit when I went and looked at the actual votes given in the 2008 European Car of The Year award, given to the Fiat 500.
Three German voters gave the Fiat 500 a score of 2. This was the lowest vote given by any judge for this car. What is interesting is that this means that the car got more bottom votes from the German voters than from all other voters combined (a score of 2 was also given by one Hungarian judge and by one Swedish judge).

Heil! Heil!

James White

Gerald asked about GM's two mode hybrid. The series hybrid is much simpler mechanically. I much prefer this series hybrid over the Orion parallel hybrid. Series hybrids are quieter and I believe will ultimately prove to be more efficient in the long run. Many claim that the efficiency losses in the generator and electric motor are greater than the losses caused by running the engine at less than optimal speeds, but this has not been a problem for diesel-electric locomotives.

I rode in one of the world's first PHEV school buses yesterday. The mileage is much better than a conventional bus, but the riding experience in the parallel hybrid bus is not much different than a standard bus. Because the electric motor is mechanically connected to the engine, the diesel engine still runs up and down as the gears shift and it runs to power the brakes and power steering. Being able to drive without the diesel engine running would have greatly changed the riding dynamics.

Bob Bastard

James White, I think that the operating cycle of the bus plays a big factor in which architecture is preferable. I agree that for a bus running around downtown Manhattan that never exceeds 30 mph, and has lots of stops, a series design makes more sense. However, for a Greyhound traveling on the interstate between Arizona and New Jersey, the series hybrid design doesn't make much sense.


The roof is a strange place to put a 17KWhr Li-ion battery pack, that would weigh 100-200kg.

If Li-ion battery prices come down, could they replace the entire 550kg saving on engine weight with batteries. They might get 50KWhrs, which should take a 10 ton bus 50km.

No mention if these buses are designed to be plugged in or not.

Mark Hazell

Bob Bastard says "jsut belches siesel soot unabated into the air" -- in my travels to Europe in recent years I have driven a number of diesel vehicles and have found that they are much quieter and cleaner than the diesel vehicles available in the USA -- European, Japanese and Korean diesel engines are designed to burn the much cleaner, low sulpher diesel fuel that is available in most of the world, and they are far more efficient than most gasoline engines. A friend of mine just drove over 1,200 kilometres on a single tank of gas in an Audi diesel while traveling in Italy.

Bob Bastard

@Mark Hazell: I would never say a silly thing like that. I believe you are confusing me with Stan Peterson.

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