Today’s electric vehicles typically only have enough power for 100 miles of driving, so designers of future vehicles are always looking to extend battery reserves. And it doesn’t always mean a bigger battery – some researchers are, instead, adding body components that double as capacitors, which are devices that hold an electrical charge until they are tapped. Emile Greenhalgh, a composites expert at Imperial College London, United Kingdom, has modified a car by doing just that. “Although the energies they provide are fairly modest,” Dr. Greenhalgh said, “they have shown that our material could be used to smooth the demands on the battery, thus enhancing its life.” Engineers are also developing car frames and bodies made of carbon fiber-reinforced composites, but the material remains too expensive for mass-market cars. One potential solution is to build cars with carbon composites that also serve as batteries – providing extra electricity while also making the vehicles lighter. The resin binding the carbon fibers would be laced with lithium ions, enabling the fibers to serve as conductive electrodes for this type of charge-holding capacitor. “Structural power technology combines mechanical structure and energy storage capabilities,” said Dr. Greenhalgh. “This could allow us to have our cake and eat it too.” Another European research group, the Swedish Institute of Composites, is working on a structural battery, and plans to test a prototype electric vehicle in which the trunk floor provides electricity. According to Per-Ivar Sellergren, an engineer at the Volvo Cars Materials Center in Gothenburg, Sweden, “We’re expecting a 15 percent weight savings compared to the standard battery in a conventional structure. Even though the panel will not be large enough to power the entire car, it could provide enough power to switch the engine off and on when the car is stopped at a traffic light.”
http://www.nytimes.com/2011/06/05/automobiles/05BATTERY.html?_r=2