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The Ultracapbus

an alternative drive system taking the test of everyday-use



As the first German transportation company we have been testing an alternative drive system using high-performance capacitors - so called Ultracaps - in everyday line-operation. The trial phase took place between November 2001 and May 2002, mainly on Line 36 in the city centre of Nuremberg. The cientific evaluation of the resulting data is in full swing now. Also participating in this venture are the vehicle manufacturer, MAN Nutzfahrzeuge AG, and the Institute of Vehicle Technology at Georg-Simon-Ohm university of applied sciences in Nuremberg.


The test vehicle was equipped with a diesel-electric drive in combination with the new Ultracp-technology.
The high-performance capacitors were used to accumulate braking-energy and - in comparison to other energy storage devices, like batteries - excelled by exceptionally high power take-up capacity. All in all, there were eight modules (containing 36 Ultracaps each) mounted on the roof of the bus. The braking-energy was stored in these high-performance capacitors. So the energy set free during braking was not "burned off" in wheel brakes or braking resistors, but re-used to accelerate the bus again.

The Ultracap-system

  • 8 Ultracap-modules
  • 640 V voltage
  • 400 A maximum current
  • 0,4 kWh energy content
  • 400 kg weight


Advantages of the system in overview

  • Significant decrease of fuel consumption (at the time being 10-15 percent compared to a conventional diesel vehicle)
  • Reduction of emissions, particularly CO²
  • Leaving stops without bothersome noise- or vehicle-exhaust-pollution
  • Enhancement of drive comfort (jerk-free, low-vibration drive)
  • Reduction of maintenance cost


By testing the Ultracapbus we help companies like MAN Nutzfahrzeuge AG, Siemens Transportation Systems and EPCOS to gain new insights from practical experience for the further improvement of tomorrow`s vehicles. Once again we actively contributed towards the development of new potentials for fuel economy, decrease of maintenance costs and reduction of pollutant emissions, like the climate-relevant carbondioxide CO². Since 1992 we - as a precursor of eco-friendly drive systems - have regularly been testing innovative vehicles: the first natural-gas-powered bus in line-operation (1992), two diesel-electric busses (1998) and the first fuel-cell bus in line-operation (2001/2002).