A hydrogen vehicle is a vehicle that uses hydrogen as its on-board 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 combustion, the hydrogen is burned in engines in fundamentally the same method as traditional gasoline (petrol) cars.
In fuel-cell conversion, the hydrogen is reacted with oxygen to produce water and electricity, the latter of which is used to power an electric traction motor.
Many companies are currently researching the feasibility of building hydrogen cars and most of the automobile manufacturers have begun developing hydrogen cars. Most of these vehicles are currently only available in demonstration models or in a lease construction in limited numbers and are not yet ready for general public use. The recorded number of hydrogen-powered public vehicles in the United States was 200 as of April 2007, mostly in California. Funding has come from both private and government sources.