An anonymous reader writes: BBC reports the unveiling of a hydrogen car by British automobile company Riversimple. The car's top speed is 50 mph (80 km/h), and purportedly has an efficiency equivalent of 300 miles per gallon (0,8 litres/100 km). The car is powered by a six-kilowatt fuel cell, but is also equipped with ultracapacitors allowing for faster acceleration. The engineering designs are to be made open source, to enable "local manufacturing in small plants." The design can reportedly be "adjusted for local markets, using locally sourced parts or materials." The company expects the vehicles to enter production by 2013.