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 fuel does not occur naturally on Earth and thus is not an energy source, but is an energy carrier. It can be made from a number of sources, currently it is most frequently made from methane or other fossil fuels. Hydrogen production via electrolysis of water is inefficient and expensive and is rarely used.
Many companies are working to develop technologies that can efficiently exploit the potential of hydrogen energy.
