As the price of oil continues to rise solar arrays will continue to be built in the deserts, and that power will be available on the electric power grid. One issue is storing that electricity for use when the sun isn't shining. Batteries tend to have short life spans, high replacement costs and issues with disposing of or recycling the materials used to construct them.
This car uses a super-capacitor to extend the life of the battery.
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MIT Nanotube Super Capacitor - PESWiki
Technology Review: A Cheaper Battery for Hybrid Cars