trailer world issue Two 2008

Rubrik Ausgabe Zwei 2008 21 the batteries to the extent that movement under purely electrical power is ensured. Charging overnight from the socket is essential for longer, purely electrical routes in the town. For the hybrid Sprinter with Ni- MH batteries for example, this process can be completed in six hours. Or one can resort to charging during the journey with the diesel engine: in this case, a signiﬁcant proportion of the performance of the diesel drive is diverted via the electric motor, which now acts as a generator. In comparison to charging overnight with cheap elec- tricity from the socket, this form of on-board recharging is how- ever not particularly economi- cal, especially since the diesel engine only works (in the best case) at an energy eﬃciency level of 42 to 45%. The hybrid drive with an inten- tionally high proportion of purely electrical drive therefore requires a high charging rate, which can- not by any means be covered by the recovery of braking energy. Progress has already been made with regard to this problem in the case of inner-city buses. The IDEAS project (“Innovative die- sel-electric hybrid drive for city buses”) initiated by MAN and Siemens uses the combustion en- gine only as a pure plant engine, which only operates the electrical systems via a generator, and has nothing more to do with the actual drive to the wheel. The advantage of this so-called “serial” hybrid: the diesel engine only runs when re- quired, and then only in a very narrow revs range, always with op- timum load and consumption. The actual drive is provided only by electric motors. To complement this, high-performance condensers, so-called ULTRA-CAPS, have already proven their capability as short-term, high-energy accumulators for scheduled bus services. Developers however consider battery systems as more suitable for emission-optimised distributor use in truck applications. The energy densityrequiredforpure, EMISSION-FREE ELECTRONIC DRIVE (without the supporting generator drive by the diesel engine) can at the moment only be provided by battery-assisted systems. The logical consequence of all these eﬀorts towards high-eﬃcien- cy hybrid drives for commercial vehicles would in future be a drive using electric wheel hub motors. This would allow manufacturers to dispense with many components such as diﬀerentials, gearboxes, shafts, which not only entail unnecessary weight, but also signiﬁ- cantly restrict the basic idea of a distribution vehicle, namely the transport of goods to the trade. A truck whose basic structure would only have to accommo- date a battery pack, in addition to a diesel engine as a purely power plant motor, could be designed completely diﬀerently to current concepts thanks to the space-sav- ing wheel hub drive: for example as a self-supporting construction with a very low bed. Whether light hybrid transport- ers and trucks will be able to be launched onto our markets quickly depends primarily on whether they will be in demand, and at the same time subsidised. The demand pressure for high- performance hybrid trucks and transporters will only become great enough if towns and com- munities establish extremely restrictive “zero-emission” zones. Ve- hicles complying with these requirements could be quickly brought to the point of service maturity. Progress in the technology of LITHIUM-ION-(LI-IO) BATTERIES in particular gives cause to hope for more economical and durable battery solutions. Viable hy- brid trucks, according to Volvo and also Daimler, will not be avail- able until 2009, by which time Mercedes will have the plug-in hybrid Sprinter ready for series production, and Mitsubishi Fuso the hybrid Canter. Volvo is also promising that the FM will be available as a hybrid for 2009. (rd) Issue Two 2008 21 TechnologyPhoto:VolvoTrucks

trailer world issue Two 2008

Pages