Energy storage system with ultracaps on board of railway vehicles

The on board energy storage system with Ultracaps for railway vehicles presented in this paper seems to be a reliable technical solution with an enormous energy saving potential. Bombardier Transportation has equipped one bogie of a prototype LRV (light rail vehicle) for the public transportation operator RNV in Mannheim with a MITRAC Energy Saver. Outstanding feature is the daily operation of the energy storage unit in daily passenger service, and this even since September 2003. The experiences are very positive. The measured traction energy saving of approximately 30% confirmed fully the former calculations. Running the energy storage device on board of a tram brings additionally following benefits: (i) a dramatic reduction of the peak power demand (ii) catenary free operation" on several hundred meters without power supply from the catenary (iii) catenary free city center by on board storage and recharging stations. Applying the energy storage devices in Metro systems has a similar effect as in case of LRVs. However the savings distribution in the whole system will be a little bit different. Due to higher regeneration capability of metro systems the expected share of the train propulsion saving will be lower. It will be compensated by a considerable reduction of the line losses, especially for systems with low rated catenary voltages (600 V or 750 V). Very promising are energy storage applications in propulsion systems of diesel-electrical multiple units (DEMUs). These vehicles lack possibilities to use the braking energy of the train. Energy storage systems on board of DEMUs bring high fuel savings together with the corresponding emission reduction. On top of that the energy storage leads to a booster effect - extra power during acceleration from the storage, by adding the limited weight of the MITRAC Energy Saver.