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21. May 2007

Aluminum pellets may facilitate hydrogen-powered car, but…

A professor at Purdue University in the US has developed a method for extracting hydrogen from water using an aluminum alloy. He believes this method could be used to power cars, although he recognizes that there are significant hurdles that need to be overcome before this break-through becomes a commercially-viable alternative to gasoline.

The method, which was developed by Jerry Woodall a professor of electrical and computer engineering at Purdue University, makes it unnecessary to store or transport hydrogen.

“The hydrogen is generated on demand, so you only produce as much as you need when you need it,” said Woodall.

According to Woodall, the technology could be used to drive small internal combustion engines in various applications, including portable emergency generators, lawn mowers and chain saws. He also believes that the process could, in theory, also be used to replace gasoline for cars and trucks.

Hydrogen is generated spontaneously when water is added to pellets of the alloy, which is made of aluminum and a metal called gallium. Researchers have shown how hydrogen is produced when water is added to a small tank containing the pellets. Hydrogen produced in such a system could be fed directly to an engine, such as those on lawn mowers.

“When water is added to the pellets, the aluminum in the solid alloy reacts because it has a strong attraction to the oxygen in the water,” Woodall said.

This reaction splits the oxygen and hydrogen contained in water, releasing hydrogen in the process.

The gallium is critical to the process because it hinders the formation of a skin normally created on aluminum’s surface after oxidation. This skin usually prevents oxygen from reacting with aluminum, acting as a barrier. Preventing the skin’s formation allows the reaction to continue until all of the aluminum is used.

Woodall said that because the technology makes it possible to use hydrogen instead of gasoline to run internal combustion engines it could be used for cars and trucks.

That’s the good news. Now for the bad news.

Woodall admits that in order for the technology to be economically competitive with gasoline, however, the cost of recycling aluminum oxide must be reduced.

“Right now it costs more than $1 a pound to buy aluminum, and, at that price, you can’t deliver a product at the equivalent of $3 per gallon of gasoline,” Woodall said.

Woodhall does have a solution for this problem. He believes the cost of aluminum could be reduced by recycling it from the alumina using a process called fused salt electrolysis. The aluminum could be produced at competitive prices if the recycling process were carried out with electricity generated by a nuclear power plant or windmills. Because the electricity would not need to be distributed on the power grid, it would be less costly than power produced by plants connected to the grid, and the generators could be located in remote locations, which would be particularly important for a nuclear reactor to ease political and social concerns, Woodall contends.

“The cost of making on-site electricity is much lower if you don’t have to distribute it,” Woodall said.

Woodall believes adopting this approach could enable the United States to replace gasoline for transportation purposes, reducing pollution and the nation’s dependence on foreign oil.

“We call this the aluminum-enabling hydrogen economy,” Woodall said. “It’s a simple matter to convert ordinary internal combustion engines to run on hydrogen. All you have to do is replace the gasoline fuel injector with a hydrogen injector.”

Woodhall believes that even at the current cost of aluminum, however, the method would be economically competitive with gasoline if hydrogen fuel cells are perfected for cars and trucks in the future.

“Using pure hydrogen, fuel cell systems run at an overall efficiency of 75 percent, compared to 40 percent using hydrogen extracted from fossil fuels and with 25 percent for internal combustion engines,” Woodall said.

“Therefore, when and if fuel cells become economically viable, our method would compete with gasoline at $3 per gallon even if aluminum costs more than a dollar per pound.”

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