Hydrogen
Hydrogen is the most abundant element in the universe, making up 75% of all mass of all visible matter in stars and galaxies. Hydrogen is the simplest of all elements. A hydrogen atom has a dense central nucleus with a single orbiting electron, much like a single planet in orbit around the sun. Hydrogen has the greatest energy to weight quotient of any fuel because hydrogen is the lightest of all the elements. Hydrogen has been used extensively in the space program where weight is crucial. The amount of energy released during the reaction of hydrogen, on a unit mass basis, is about 2.5 times the heat of combustion of common hydrocarbon fuels such as; gasoline, diesel, methane, propane, etc. Therefore, on a comparison basis the amount of hydrogen required is only about a third of the amount of hydrocarbon fuel needed to do the same amount of work. The current drawback of hydrogen as a fuel is storage space volume. On a comparison basis with hydrogen and diesel fuel, the volume of the hydrogen storage tank would have to be 16 times larger for gaseous hydrogen and 4 times larger for liquid hydrogen in comparison to diesel fuel.Hydrogen can be stored as a gas, a cryogenic liquid, or a metal hydride. According to Department of Energy guidelines, in a draft released on June 3, 2003 the goal for technical production of hydrogen is to become competitive with gasoline by 2015.
