HYDROGEN VEHICLE
A hydrogen vehicle is a vehicle that uses hydrogen as its onboard fuel for motive power. The term may refer to a personal transportation vehicle, such as an automobile, or any other vehicle that uses hydrogen in a similar fashion, such as an aircraft. The power plants of such vehicles convert the chemical energy of hydrogen to mechanical energy (torque) in one of two methods: combustion, or electrochemical conversion in a fuel-cell:
• In hydrogen internal combustion engine vehicles, the hydrogen is combusted in engines in fundamentally the same method as traditional internal combustion engine vehicles.
• In fuel-cell conversion, the hydrogen is reacted with oxygen to produce water and electricity, the latter being used to power an electric traction motor.
Hydrogen is one of two natural elements that combine to make water. Hydrogen is not an energy source, but an energy carrier because it takes a great deal of energy to extract it from water. It is useful as a compact energy source in fuel cells. Many companies are working hard to develop technologies that can efficiently exploit the potential of hydrogen energy.

By Jason Palmer
Science and technology reporter, BBC News

The car may be rolled out in small to medium UK cities starting in 2010

The manufacturer of a hydrogen car unveiled in London will make its designs available online so the cars can be built and improved locally.
The Riversimple car can reach 80km/hr (50mph) with a range of 322km (200 miles). Fuel consumption is claimed to be equivalent to 300 miles per gallon.
The cars will be leased with fuel and repair costs included, at an estimated £200 ($315) per month.
The company hopes to have the vehicles in production by 2013.
Next year, it aims to release 10 prototypes in a UK city which has yet to be confirmed.
Riversimple has in partnership with gas supply company BOC to install hydrogen stations for the cars in the city where the prototypes are launched.