Hydrogen, generated from renewable sources, provides an ideal medium for energy storage and transportation. When combined with oxygen, it forms water and releases energy. Hydrogen is a gas at normal temperatures and pressures and can be transported in much the same way as natural gas. Converting the energy of stored hydrogen into useful work can be accomplished by many technologies. The most attractive long-term technology for this purpose is the fuel cell.
Fuel cells combine hydrogen and oxygen, without combustion, to produce water and electricity.
The DOE Office of Transportation Technologies, in collaboration with automobile manufacturers and other industries, is supporting the development of PEM fuel cells for use in the transportation sector. Conventional internal combustion engines can also be made to operate on hydrogen. MAN, a major European bus manufacturer, has constructed a hydrogen-powered bus from a standard production city bus with an internal combustion engine designed to operate on either hydrogen or gasoline. Both the hydrogen and gasoline are stored in liquid form. This particular bus has been in service since April, 1996.