Hydrogen is the most abundant element in the universe, but is rarely found in its un-combined form on the earth. When combusted (oxidized) it creates only water vapor as a byproduct (4H + 02 = 2 H20).
When burned in an internal combustion engine, however, combustion also produces small amounts of nitrogen oxides and small amounts of unburned hydrocarbons and carbon monoxide because of engine lubricants. The exhaust is free from carbon dioxide.
Hydrogen is normally a gas and can be compressed and stored in cylinders. It can also be kept as a liquid, but the gas only turns liquid at temperatures of minus 423.2 degrees Fahrenheit.
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Today, hydrogen is mostly obtained by cracking hydrocarbon fuels, but it can be produced by electrolysis of water (using electricity to split water into hydrogen and oxygen) and photolysis (chemical decomposition). The main problem hydrogen is bulk storage required for fuel tanks.
For an equivalent energy content of gasoline, liquid hydrogen and the required refrigeration system requires six to eight times more storage space than gasoline and compressed hydrogen gas requires six to ten times more storage space. Another development using hydrogen is as a blend of hydrogen and methane (natural gas) called Hyphened.
Preliminary information presented in mid-1994 at the 10th World Hydrogen Energy Conference in Cocoa Beach, Florida, says that test cars exhaust using 30 per cent hydrogen and 70 per cent methane contained 80 per cent less nitrogen oxides than U.S. EPA standards for 2003. This blend has much higher content of hydrogen than other Hyphened blends, which typically run about five per cent.
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There are no vehicles currently available that use hydrogen as a fuel; however, automobile manufacturers have experimented with developing vehicles that use hydrogen. Research vehicles have been produced by Daimler-Benz, BMW and Mazda. The Mercedes-Benz and BMW vehicles use liquid hydrogen.
The Mazda vehicle stores its hydrogen as a gas in a metal-hydride lattice of shaved metal. Other vehicles have been built using compressed hydrogen, including two vehicles in Arizona pirated by the American Hydrogen Association.
High production costs and low density have prevented hydrogen’s use as a transportation fuel in all but test programs, h may be 20 to 30 years or more before hydrogen is a viable Aspiration fuel and then perhaps only in fuel-cell-powered vehicles.