At a recent press conference held by Siemens to mark 150 years in South Africa and launch its new investment plans, the company showcased its new electric Porsche. Delegates had the opportunity to drive the eRuf Roadster on the Kyalami race track.
Siemens is deeply involved in the field of electromobility. On the vehicle side the main thrust is the development of electric drive units. “For the prototype we used an integrated system consisting of a motor and generator, power electronics, and an interface with a battery connection,” explains Professor Spiegelberg, an expert in the field of electric drive systems and head of the electric mobility team at Siemens Corporate Technology. The innovative eDrive system has a central motor with an output of 270 kWh and torque of 950 Nm. When driven in a moderate manner, it has a range of around 200 km.
Siemens does not build electric cars itself, but has a research collaboration with RUF Automobile, a German company that specialises in modifying Porsches. RUF has installed the eDrive system in two demonstration vehicles, the eRuf Roadster, based on the Porsche 911, and the eRuf Stormster, based on the Porsche Cayenne. The eRuf sportscar can accelerate from zero to 100 km/h in five seconds and attains a top speed of 250 km/h.
At present Siemens researchers and developers are working on the next generation of electric motors based on a double electric motor concept. The new electric motor has an output of 125 kW and a rated voltage of 700 V. Power density is 2,4 kW/kg, with a total weight of 52 kg.
Ruf plans to manufacture new models employing this dual-motor concept. This will be the first electric car in the world with a bidirectional power connection. It will be recharged within an hour at a 380 V electrical outlet without the extra electrical circuitry typically required for recharging. The bidirectional system will also permit it to feed energy back into the power grid via the same socket.
Another focus of Spiegelberg’s team is on electric vehicle system requirements and the design of a mobility power grid infrastructure. Siemens engineers are examining power generation and distribution options, transport and energy management systems, smart metering, power electronics, software, sensors and the recovery and storage of energy. In addition to serving as energy storage units, electric drives could also become an important part of Siemens’ environmental portfolio. That is because they utilise energy more efficiently than combustion engines.
A good electric vehicle requires a battery with an energy content of 42 kWh to achieve a range of around 300 km, in other words an energy consumption level of 15 kWh per 100 km. Assuming a normal voltage of 230 V and a current of 16 A, it would take around 12 hours to completely charge such a battery. “But at 400 V and 25 A, a driver could recharge in just two hours,” says Professor Spiegelberg. “Every German household has 400 V potential because that is the voltage used by a normal three-phase current connection. The only thing missing up until now has been a suitable interface between the vehicle and the grid,” he adds.
For more information contact Keshin Govender, Siemens Southern Africa, +27 (0)11 652 2412, [email protected], www.siemens.co.za
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