U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Fact #204: February 18, 2002
As part of an effort to reduce American dependence on foreign oil, Energy Secretary Spencer Abraham announced on January 9, 2002, a new public-private partnership between the U.S. Department of Energy and the nation's automobile manufacturers to promote the development of hydrogen as a primary fuel for cars and trucks. This program is called FreedomCAR (Cooperative Automotive Research), and will fund research into advanced, efficient fuel cell technology that uses hydrogen to power zero-emission light-duty vehicles. A few facts about hydrogen follow.
What are some characteristics of hydrogen?
- Hydrogen is a nontoxic, colorless, odorless, and tasteless gas.
- Hydrogen, bound in organic matter and water, makes up 70% of the Earth's surface. It is the most common element in the universe.
- Hydrogen usually exists in combination with other elements, such as oxygen in water, carbon in methane, and in trace elements as organic compounds.
- When cooled to a liquid state, hydrogen takes up 1/700 as much space as it does in its gaseous state.
- Hydrogen is about one-fourth as dense as air.
- The temperature needed to cool hydrogen to a liquid state is -423ºF (-253ºC).
Why is hydrogen used as a fuel?
- Hydrogen has the highest energy content per unit weight of any known fuel — 52,000 Btu/lb (120.7 kJ/g).
- It burns cleanly. When hydrogen is burned with oxygen, the only by-products are heat and water. When burned with air, which is about 68% nitrogen, some oxides of nitrogen are formed.
How is hydrogen produced?
- Most of the hydrogen produced in the United States is made by steam reforming, which is currently the most cost-effective way to produce hydrogen. There are many other ways to produce hydrogen, including electrolysis.
- In fuel cells, electrolysis is reversed by combining hydrogen and oxygen through an electrochemical process that produces electricity, heat, and water.
Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy Network, Consumer Energy Information: EREC Reference Briefs, Hydrogen Fuel, February 2001.
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