Generator-electric drives for electric vehicles.
Prospects for the future of electric mobility can be realized relatively easily by moving away from the principle of having to store all the electrical energy for an entire journey. As a generator-electric drive concept developed at Fraunhofer LBF shows, even heat engines and electric generators can generate electrical energy while driving. As stationary energy producers, heat engines can use fossil or biobased fuels and in the future will also be able to use electricity-generated methane. A generator converts the mechanical work produced into electrical energy which is available for electric traction.
Such a vehicle has the battery and monovalent heat engine as energy sources. The maximum battery capacity is 10 kWh and the constant power of the energy generator is less than 20 kW. As a result, the power input necessary on average for a normal mixture of routes is always available from the energy generator, while at the same time the energy storage device covers virtually any power peaks. The size of the energy storage device can be designed for a maximum output of approximately 45 kW per metric ton of vehicle weight, while the energy generator is only a third of this size but has to supply constant power. This enables a continuous speed of around 120 km/h on level ground. Significantly simplified design constraints for the heat engine and the comparatively small energy storage device reduce the costs and the weight considerably. According to calculations made with a model developed at the LBF, the illustrated costs of a generator-electric C-Class vehicle with a drive power of 80 kW are around 10% higher than the lifecycle costs of the reference model with diesel engine, but considerably lower than those of a battery electric vehicle.
With the GEV|1, the LBF implemented a first prototype with a weight of about 1.3 metric tons. This made it necessary for the gas engine to produce a continuous output of 18 kW. The high-voltage energy storage device was constructed of Li-Ion round cells. Its total capacity is 9.8 kWh (24 Ah), thus enabling a purely electric range of about 35 kilometers before the threshold for starting up regenerative power generation is reached. Even then, the maximum electrical drive power of 80 kW is still available. The vehicle’s emission balance ranges between zero for distances up to 35 kilometers and 70 g/km for distances ten times longer.
Generator-electric drives are easily scalable. What’s more, the concept does not require extensive investment in the charging infrastructure. Even using a household socket, the energy storage device is completely recharged in less than three hours. The electric generator can charge the high-voltage storage device within half an hour even without access to the power grid.
With generator-electric vehicles, the characteristics that are so important for the transport sector – efficiency, emission behavior and energy storage capability – are reconfigured and can shape the future of motorized individual mobility very positively.
Fraunhofer LBF has shown with a first prototype that a vehicle concept such as this can result in cost-efficient e-mobility suitable for a first vehicle.
Link: Detailed information about “the drive technology that connects us with the future right now
“The patented generator-electric drive with monovalent gas engine is an interesting drive concept for passenger cars and commercial vehicles that connects us with the future right now.” Rüdiger Heim
- Rüdiger Heim
- Phone: +49 6151 705-283