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Diesel-electric drive

Smoothly functioning transport and traffic systems are essential to the competitiveness of an economy within Europe and to a nation’s export drive.

Alongside costs and operating efficiency, there are other factors critical in the consideration of transport options: global warming, emissions, noise and the urgent need for higher energy efficiency. Right at the top of the political and social agenda in Germany and in many other countries worldwide is the issue of CO2 emissions. Accompanying the heated debate is rising pressure on industry to come up with workable and sustainable solutions for climate protection.

Lowering emissions and energy consumption

Kiepe Electric’s hybrid drive reduces fuel consumption and hence emissions from urban buses. There is also none of the typical noise caused by the diesel engine revving up. In all, much less of a nuisance for local residents, passengers waiting and on board, and the bus driver.

Kiepe Electric’s series hybrid drive

The basis for such fuel savings is adaptive and intelligent energy management. While the vehicle is moving, a diesel engine drives a generator and, at the same time, takes into consideration the actual load situation for minimum consumption. The generator is interconnected via a secondary electric circuit to the traction motor. When the brakes are applied, the released energy is quickly and effectively saved by the energy storage system (ESS) to be made available when reaccelerating. An energy manager regulates the flow of energy between the generator, ESS (supercaps; galvanic battery optional) and traction motor. All the energy management components are proprietary products from Kiepe Electric and undergo continuous refinement.


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A variety of options are available, depending on the type of vehicle and its equipment: diesel engine speed reduction down to switching off in a variety of time-frames. The vehicle can, if specified, start up and brake with the diesel engine switched off (zero emissions, very little noise). Part and parcel of the system are such state-of-the-art functions for activating ABS/ASR, an electric hillholder, and troubleshooting.

Being modular, the hybrid system can be used on (multi)articulated buses with dual-axle drive and on buses with single-axle drive alike.

Series hybrid drive allows the vehicle to do without a diesel engine altogether by using as its prime energy source a fuel cell.


Parallel or series?

There are basically two modes of hybrid drive available on the market: parallel and series. On the former, a diesel engine and an electric traction motor operate simultaneously.  Hence, they can have a smaller footprint than if only one of them assumed full traction responsibility. However, all-electric drive is only partly possible.

Series hybrid drive, in contrast, permits purely electric propulsion since the diesel engine is not directly connected to the drive axle. Instead, it drives a generator that sends energy to the storage unit or traction motor, as required, and hence acts as an energy supply module. I.C. engine, energy storage unit and electric motor are therefore interconnected in series (in a row) and activated independently of each other. This results in a higher degree of flexibility in the control and management of energy. Also possible is a more flexible use of various energy sources and storage units, all in conjunction with the same drive platform.

It is particularly under urban traffic conditions with their repeated acceleration/deceleration phases that series hybrid drive is in its element. With the aid of the electric traction motor the vehicle can accelerate and decelerate purely electrically. When the vehicle slows down, the kinetic energy is converted into electrical and, at a very high level of efficiency, made available for the next acceleration phase.