A new concept of “green” car was unveiled today in London. This one runs on hydrogen.

The Riversimple Urban Car (RUC) is reportedly powered by a fuel cell designed to use the energy provided by combining hydrogen gas with the oxygen naturally present in the air. No smoke and no pollution: all the car “exhausts” is water.

The RUC manufacturers are also looking into simpler, more cost-efficient methods of manufacturing the car. They expect it to be sold to the public by 2011, while its closest competitor, Honda’s FCX Clarity hydrogen car, is expected to hit the streets on 2018.