The basics of a hydrogen economy
03/02/2009 12:01 AM
04/02/2009 11:28 AM
Boosters say hydrogen and fuel cells have the potential to revolutionize the way the world makes and uses energy.
To date, hydrogen has been used to power everything from cell phones to space shuttles.
Hydrogen is the most abundant element in the universe. It is lighter than air, colorless, odorless, tasteless and nontoxic at room temperature.
Hydrogen also contains more useful energy per pound than any other energy carrier. This means hydrogen is more efficient on a weight basis than any of the fuels currently used in air or ground transportation, experts say.
When hydrogen is used in a fuel cell, the only byproducts created are electricity, water and useful heat — no particulates, no carbon dioxide and no smog.
While hydrogen makes up most of the known universe, it’s rarely found on Earth in pure form.
Almost all hydrogen in use today is made by separating, or “reforming,” a hydrogen compound. Most hydrogen is produced from light hydrocarbons, such as natural gas, although in principle any hydrogen compound can be used — even plain water. Hydrogen also sometimes is produced as a byproduct of other chemical processes.
Natural gas accounts for 48 percent of current hydrogen production, but increasing renewable alternatives, such as water electrolysis via solar power, are gaining momentum and will contribute to the sustainability of clean hydrogen technologies.
Hydrogen can be stored in many ways, but it is usually compressed in steel or composite tanks and held at pressures up to 10,000 pounds per square inch, or liquefied at -423 degrees Fahrenheit. Liquid hydrogen has three times the amount of energy as an equal weight of gasoline. Hydrogen also can be stored in metal hydrides — granular metal that absorbs hydrogen.
Each of these storage technologies are currently being explored by both the Savannah River National Laboratory and the Center for Hydrogen Research, both in Aiken.
A national hydrogen distribution network supplies commercial users. Hydrogen is distributed by pipeline, truck and barge and in smaller portable containers.
Hydrogen has been produced, stored, transported and used for more than 40 years by NASA and other industrial groups.
HOW FUEL CELLS WORK
Essentially, a fuel cell operates like a battery but does not run down or require recharging. It will produce energy as long as fuel is supplied. A fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat.
Ever since the Hindenburg was destroyed by fire in 1937, hydrogen has been given a misleading reputation. Hydrogen was used only to keep the Hindenburg buoyant. It was the ship’s outer fabric that was coated with easily ignitable chemicals that was to blame for the disaster.
Hydrogen is lighter than air and diffuses rapidly. In the event of an accidental release, hydrogen disperses quickly upward into the atmosphere. Other fuels can take longer to disperse or may spill into the ground, requiring specialized cleanup efforts.
When hydrogen burns, its flames have very low radiant heat, which means there will be less risk of secondary fires. In the event of an automobile collision, hydrogen tanks won’t react like typical gasoline tanks, meaning that a resulting fire will disperse much quicker and the interior of the car will not heat up to extreme temperatures.
SOURCE: SC Hydrogen and Fuell Cell Alliance
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