General interest press release
Energy Storage Units Save 80 Tons of CO2 Per Year
Since November 2008, Sitras HES has been used in passenger service. The tram now operating between Almada and Seixal, two cities to the south of Lisbon, is not only able to travel over distances of up to 2,500 meters without being supplied with power from the OCL, it is also saving energy at the same time. The system was mounted on unused roof surfaces of the vehicle.
Siemens has launched a new hybrid energy storage system forstreetcars. Streetcars equipped with the solution can be driven upto 2,500 meters without an overhead conductor, and the systemsaves lots of energy. This is possible thanks to a combination of adouble-layer capacitor and battery. Running streetcars without anoverhead conductor is especially appropriate for historic downtownareas, where the cables spoil the view, or in places where itis simply difficult to install cables — for example in tunnels, underbridges, or at large intersections.
Streetcars with the system consume up to 30 percent less energyand produce up to 80 metric tons less CO2 emissions peryear than vehicles without energy storage devices. Another plusis that the systems are mounted on the streetcar roofs and electricallyconnected to the vehicle's energy supply point. This newswitching concept enables the Siemens technicians to integratethe energy storage system in new rail vehicles and in existingstreetcars to realize energy savings. The energy storage units arepart of the Siemens environmental portfolio, with which thecompany generated about €19 billion in revenues in 2008.
The Siemens system — called Sitras HES — consists of two energystorage devices: the Sitras MES (double-layer capacitor)mobile energy storage unit and a nickel-metal hydride battery.This concept combines the benefits of the high-performancecapacitors with the characteristics of a traction battery. The capacitorsrecharge faster and deliver the energy faster than tractionbatteries, which release their stored energy over longer periods.While the streetcar is under way, the energy storage unitsrecharge through the vehicle's braking. The stored energy makesit possible for a streetcar to be driven for longer distances withoutdrawing power from the overhead conductors. The energy storagesystems also can recharge while the streetcars are moving onsections equipped with overhead conductors or by means ofstationary charging stations, for example at streetcar stops.
In Portugal the hybrid energy-storage system is being successfullyused in everyday passenger-transport operation, linkingAlmada and Seixal, cities located south of Lisbon. In Germany italso is approved for use in public passenger transportation, inaccordance with BOStrab (a legal ordinance governing the manufactureand operation of streetcars).
Photo: http://www.siemens.com/ct-pictures/in20090707