Tishitu explains

We already uses some 10 million tons of hydrogen each year for industrial purposes, such as making fertilizer and refining petroleum. If hydrogen-powered vehicles are to become the norm, we'll need at least 10 times more. The challenge will be to produce it in an efficient and environmentally friendly way.

FOSSIL FUELS: At present, 95 percent of hydrogen is produced from natural gas. Through a process called steam methane reformation, high temperature and pressure break the hydrocarbon into hydrogen and carbon oxides — including carbon dioxide, which is released into the atmosphere as a greenhouse gas. Over the next 10 or 20 years, fossil fuels most likely will continue to be the main feedstock for the hydrogen economy. And there's the rub: Using dirty energy to make clean energy doesn't solve the pollution problem-it just moves it around. "As a CO2 reducer, hydrogen stinks.Whether carbon dioxide will remain underground in large-scale operations remains to be seen. In addition, natural gas is a limited resource; the cost of hydrogen would be subject to its price fluctuations.

ELECTROLYSIS: Most of the remainder of today's hydrogen is made by electrically splitting water into its constituent parts, hydrogen and oxygen. But because fossil fuels generate more than 70 percent of the nation's electrical power, hydrogen produced from the grid would still be a significant source of greenhouse gas. If solar, wind or other renewable resources generate the electricity, hydrogen could be produced without any carbon emissions at all.

NUCLEAR POWER: Next-generation nuclear power plants will reach temperatures high enough to produce hydrogen as well as electricity, either by adding steam and heat to the electrolysis process, or by adding heat to a series of chemical reactions that split the hydrogen from water.. Department of Energy is largely funding a 10-year, $950 million project to build a coal-fed plant that will produce hydrogen to make electricity, and likewise lock away carbon dioxide to achieve what it bills as "the world's first zero-emissions fossil fuel plant."

Storage
At room temperature and pressure, hydrogen's density is so low that it contains less than one-three-hundredth the energy in an equivalent volume of gasoline. In order to fit into a reasonably sized storage tank, hydrogen has to be somehow squeezed into a denser form.

LIQUEFACTION: Chilled to near absolute zero, hydrogen gas turns into a liquid containing
one-quarter the energy in an equivalent volume of gasoline. The technology is well-proven: For decades, NASA has used liquid hydrogen to power vehicles such as the space shuttle. The cooling process requires a lot of energy, though-roughly a third of the amount held in the hydrogen. Storage tanks are bulky, heavy and expensive.

COMPRESSION: Some hydrogen-powered vehicles use tanks of room-temperature hydrogen compressed to an astounding 10,000 psi. The Sequel, which GM unveiled in January 2005, carries 8 kilograms of compressed hydrogen this way-enough to power the vehicle for 300 miles. Refueling with compressed hydrogen is relatively fast and simple. But even compressed, hydrogen requires large- volume tanks. They take up four to five times as much space as a gas tank with an equivalent mileage range. Then again, fuel cell cars can accommodate bigger tanks because they contain fewer mechanical parts.

SOLID-STATE: Certain compounds can trap hydrogen molecules at room temperature and pressure, then release them upon demand. So far, the most promising research has been conducted with a class of materials called metal hydrides. These materials are stable, but heavy: A 700-pound tank might hold a few hours' fuel. However, exotic compounds now being studied could provide a breakthrough to make hydrogen storage truly practical. "High-pressure tanks are a stopgap until we can develop materials that will allow us to do solid-state storage efficiently," says Dan O'Connell, a director of GM's hydrogen vehicle program.

Use
Once hydrogen reaches consumers, is there anything they can do with it except drive vehicles? Home energy generation is one other option. The question is whether hydrogen would be more practical than current methods. Hydrogen produced by steam reformation or by electrolysis loses energy when it is converted into electricity. The resulting efficiency is roughly equal to that of today's

power plants — which pay a lot less for raw materials. Direct generation of electricity through wind and solar power will also be more efficient for most stationary applications. That leaves transportation as the most promising use for hydrogen

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