|Basic elements and operating principle of the diesel fuel-cell APU. Click to enlarge.|
At the upcoming IAA in Hanover, automotive supplier Eberspächer is presenting a fuel-cell APU (auxiliary power unit) for commercial trucks that converts diesel efficiently to electricity and thereby supplies the required power to all on-board consumer components such as the air-conditioning system or the refrigerator units.
As a result, the load for electricity generation can be taken off the engine or generator with a resulting decrease in fuel consumption and emissions. In future generations of trucks, components still driven mechanically today could thus be powered electrically at considerably less expense, the company suggests.
Currently, the need for auxiliary power is usually met on the road via a generator. In stationary periods, a diesel auxiliary power unit or, in the worst case, the idling engine takes over the supply of on-board electricity and air-conditioning. The diesel-engine APU usually drives the air-conditioning compressor mechanically via a belt and produces electricity.
Eberspächer’s fuel-cell APU generates electrical power without mechanical power losses from the diesel in the truck tank quietly with NOx, carbon monoxide and soot particulate emissions 90% less compared with a diesel-engine APU. The control electronics limit electricity production to what is actually required.
|The application concept. Click to enlarge.||Interior of the APU. Click to enlarge.|
The maximum output is 3 kW, the possible efficiency is up to 40%. The system can be used as a supplier of energy not only during stationary periods but also on a permanent basis. When the truck starts driving, the fuel-cell system starts as well, supplying all the consumers of electricity. This relieves the generator, which would otherwise require approximately double the amount of fuel to provide the electrical power as the diesel fuel-cell system, Eberspächer says.
The longer the fuel-cell system runs and the more power is called off, the more it enhances the overall efficiency and cost effectiveness of the vehicle.
The basis of the Eberspächer APU is a high-temperature fuel cell that can generate electricity from the syngas resulting from diesel reforming. In the reformer, the diesel is first mixed with air; the mixture then flows through a catalytic converter. This process generates fuel gas containing hydrogen and carbon monoxide. The technology required for this process is based on the core competencies of the Eberspächer Group.
The mixture formation is based on our know-how in the area of fuel-operated pre-heaters, whereas in catalysis our exhaust technology skills are brought to bear.—Dr. Klaus Beetz, COO Eberspächer Climate Control Systems
The electrification of commercial vehicles is an important aspect in further fuel and CO2 reduction in the transport sector, and the diesel fuel-cell APU is an important part in this future strategy, Eberspächer says.
Many energy-intensive consumers previously coupled with the drive engine—such as the cooling water- and hydraulic pump or the compressed-air system—could in the future be operated considerably more efficiently using electricity from the mobile fuel-cell system. Even the air-conditioning compressor, today coupled with the engine, plus an additional auxiliary cooling system could be replaced by a single electrical AC system for driving and stationary operation.
The output of the drive engine would then almost exclusively take care of propulsion, which would reduce consumption further. Thanks to the switch from mechanically to electrically driven components, the weight distribution in the truck could also be bettered. And, because the battery is constantly in an ideal charging state during fuel-cell operation, the batteries lifetime lasts longer and the truck cuts out more rarely.
At the present time we’ve not yet reached the end of development. But currently we’re pressing ahead with the systems development together with a well-known commercial vehicle manufacturer. Before this year is over we’ll be carrying out extensive practical testing and are planning to launch the fuel-cell APU initially on the US market at the end of 2017.—Dr. Beetz