Fuel Cells 

Fuel cells are extremely efficient electro-chemical devices that use hydrogen and oxygen to produce electricity to power an electric motor.   Fuel cell vehicles can be either 'pure' or 'hybrids'.   When fuelled directly by pure hydrogen, fuel cell vehicles emit only heat and water vapour.  As such, they are often considered to be the ideal sustainable transport solution.   However, energy is required to produce hydrogen.  Therefore, for fuel cell vehicles to be truly "zero emission", the hydrogen they run off must be produced using a renewable energy source (for example, wind or solar).   Fuel cell vehicles are not yet commercially available, although most vehicle manufacturers have fuel cell programmes and many believe these vehicles will outsell other vehicle types within 15-20 years.