The GM Allison two-mode parallel hybrid system is a popular drive train for hybrid buses. So far we’ve heard of them being used in North American buses built by New Flyer Industries. If you can believe the press releases there are roughly 640 hybrid New Flyers in service in 51 North American cities.
Over in Europe the GM Allison system is making its way into buses in France and the Netherlands and provided the starting point for the joint development of a light-duty two-mode hybrid drive train by GM, DaimlerChrysler and BMW. Green Car Congress has more.
Mercedes Benz is set to unveil the hybrid version of their Citaro bus in 2008. Unlike the GM Allison Two-Mode system the new Mercedes configuration is a series hybrid with wheel motors. The articulated buses will use four wheel motors at the center and rear axles that will be powered by roof-mounted lithium ion batteries. The four motors have a combined output of 320kW.
The standard 12L diesel has been replaced by a smaller 4.8L unit which is sufficient to keep the batteries charged since it doesn’t have the deal with transient loads of acceleration. The smaller engine cuts about 550kg from the weight of the power train and the elimination of the transmission also contributes to a net weight penalty of only 1 tonne for the hybrid bus. The engine in the Citaro will only run when the batteries need charging which will also be supplemented by regenerative braking from the motors. More from AutoblogGreen, including the press release.
This press release from MAN suggests they are about to release their third generation hybrid bus.
In the medium-term, the Group identifies in particular bus-application potential for diesel-electric hybrid systems using new kinds of ultracapacitors. This is a technology already introduced in the city bus launched by MAN in 2001 and tested on regular service by the Nuremberg transit authority (VAG) in 2001/2002. This was followed in 2005 by a second-generation model featuring a number of improvements, again on regular service in Nuremberg. Even when compared with modern diesel-engine buses, fuel savings, depending on the nature of the operation, were up to 25 percent.
And then there is the Scania ethanol electric hybrid we told you about not long ago and London has a hybrid double decker bus built by WrightBus Limited. Hybrid buses are literally popping up everywhere.
Given the torque characteristics of electric motors are ideal for start stop operations we would have thought there would already be hybrid buses operating in Australia. The Age reports that Melbourne is set to trial hybrid buses but we haven’t heard of any in every day operation. If you have please let use know by leaving a comment.