Posted on 05/17/2007 4:09:52 AM PDT by saganite
WEST LAFAYETTE, INDIANA, USA -- A Purdue University engineer has developed a method that uses an aluminum alloy to extract hydrogen from water for running fuel cells or internal combustion engines. The technique could be used to replace gasoline, though it is not quite cost-competitive yet.
The method makes it unnecessary to store or transport hydrogen - two major challenges in creating a hydrogen economy, said Jerry Woodall, a distinguished professor of electrical and computer engineering at Purdue who invented the process.
"The hydrogen is generated on demand, so you only produce as much as you need when you need it," said Woodall, who presented research findings detailing how the system works during a recent energy symposium at Purdue.
The technology could be used to drive small internal combustion engines in various applications, including portable emergency generators, lawn mowers and chain saws. The process could, in theory, also be used to replace gasoline for cars and trucks, he said.
Hydrogen is generated spontaneously when water is added to pellets of the alloy, which is made of aluminum and a metal called gallium. The 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.
The waste products are gallium and aluminum oxide, also called alumina. Combusting hydrogen in an engine produces only water as waste.
As a catalyst, the gallium is not consumed, and hence does not need to be replenished. The alumina can be recharged in a separate process, preferably using renewable energy.
The Purdue Research Foundation holds title to the primary patent, which has been filed with the U.S. Patent and Trademark Office and is pending. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process.
Woodall discovered that liquid alloys of aluminum and gallium spontaneously produce hydrogen if mixed with water while he was working as a researcher in the semiconductor industry in 1967. The research, which focused on developing new semiconductors for computers and electronics, led to advances in optical-fiber communications and light-emitting diodes, making them practical for everything from DVD players to automotive dashboard displays. That work also led to development of advanced transistors for cell phones and components in solar cells powering space modules like those used on the Mars rover, earning Woodall the 2001 National Medal of Technology from President George W. Bush.
"I was cleaning a crucible containing liquid alloys of gallium and aluminum," Woodall said. "When I added water to this alloy - talk about a discovery - there was a violent poof. I went to my office and worked out the reaction in a couple of hours to figure out what had happened. When aluminum atoms in the liquid alloy come into contact with water, they react, splitting the water and producing hydrogen and aluminum oxide.
"Gallium is critical because it melts at low temperature and readily dissolves aluminum, and it renders the aluminum in the solid pellets reactive with water. This was a totally surprising discovery, since it is well known that pure solid aluminum does not readily react with water."
"No toxic fumes are produced," Woodall said. "It's important to note that the gallium doesn't react, so it doesn't get used up and can be recycled over and over again. The reason this is so important is because gallium is currently a lot more expensive than aluminum. Hopefully, if this process is widely adopted, the gallium industry will respond by producing large quantities of the low-grade gallium required for our process. Currently, nearly all gallium is of high purity and used almost exclusively by the semiconductor industry."
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. In order for the technology to be economically competitive with gasoline, however, the cost of recycling aluminum oxide must be reduced, he said.
"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.
However, 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 said.
"The cost of making on-site electricity is much lower if you don't have to distribute it," Woodall said.
The approach could enable the United States to replace gasoline for transportation purposes, reducing pollution and the nation's dependence on foreign oil. If hydrogen fuel cells are perfected for cars and trucks in the future, the same hydrogen-producing method could be used to power them, he said.
"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."
Even at the current cost of aluminum, however, the method would be economically competitive with gasoline if the hydrogen were used to run future fuel cells.
"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."
The hydrogen-generating technology paired with advanced fuel cells also represents a potential future method for replacing lead-acid batteries in applications such as golf carts, electric wheel chairs and hybrid cars, he said.
The technology underscores aluminum's value for energy production.
"Most people don't realize how energy intensive aluminum is," Woodall said. "For every pound of aluminum you get more than two kilowatt hours of energy in the form of hydrogen combustion and more than two kilowatt hours of heat from the reaction of aluminum with water. A midsize car with a full tank of aluminum-gallium pellets, which amounts to about 350 pounds of aluminum, could take a 350-mile trip and it would cost $60, assuming the alumina is converted back to aluminum on-site at a nuclear power plant.
"How does this compare with conventional technology? Well, if I put gasoline in a tank, I get six kilowatt hours per pound, or about two and a half times the energy than I get for a pound of aluminum. So I need about two and a half times the weight of aluminum to get the same energy output, but I eliminate gasoline entirely, and I am using a resource that is cheap and abundant in the United States. If only the energy of the generated hydrogen is used, then the aluminum-gallium alloy would require about the same space as a tank of gasoline, so no extra room would be needed, and the added weight would be the equivalent of an extra passenger, albeit a pretty large extra passenger."
The concept could eliminate major hurdles related to developing a hydrogen economy. Replacing gasoline with hydrogen for transportation purposes would require the production of huge quantities of hydrogen, and the hydrogen gas would then have to be transported to filling stations. Transporting hydrogen is expensive because it is a "non-ideal gas," meaning storage tanks contain less hydrogen than other gases.
"If I can economically make hydrogen on demand, however, I don't have to store and transport it, which solves a significant problem," Woodall said.
You can pull off a very similar process by simply dissolving some lye in water and adding aluminum foil.
Bubbles off hydrogen.
And I’m sure lye is alot cheaper than gallium.
In either case, the energy used to make the aluminum is greater than the energy gotten from the hydrogen, so more efficient batteries are a much better solution.
Well, the original poster said “oxygen” and you said “air”. Air is mostly nitrogen (77%?), which has a dampening effect on combustion. There is still oxidation happening — and those are small explosions — but the alumina coating forms and keeps the reaction in air from running away so only a very small amount of the aluminum is reacting.
The article, however, is about water rather than air or pure oxygen. Water doesn’t have the dampening effect of nitrogen, and a pound of aluminum oxidized in water produces 2kwh of heat in addition to the work done in splitting the water. That’s a lot of heat but still not the explosion you’d get if you reacted pure oxygen with the aluminum gallium mixture.
This is interesting, and not the first process that generates hydrogen “on demand” for an internal combustion engine. Electrical enerby is being used in a process to power an internal combustion engine with nascent hydrogen and oxygen. There is significantly more energy available recombining nascent hydrogen and oxygen than there is in combusting hydrogen (H2) with oxygen (O2).
“That’s legitimate...fuel is a an energy storage medium, after all...but it appears doubtful to me that this technology will ever become really competitive with fossil fuels. Not this century, anyway.”
I think the important point is that it is really dependent only on the cost of electricity, and we have many options on how to produce it. It does not depend on petroleum reserves that are not under our control, and it does not depend on choosing between food and energy uses from crops as ethanol or biodiesel does.
Those seem to be important points to me. It is true that the same can be said about batteries and electric vehicles. But this technology seems cheaper and more energy dense as a carrier than any of the battery technologies I’ve seen. According to the article, the aluminum is carrying 4.4kwh per kg ! That is compared to 0.2kwh per kg for li-ion batteries. Even including the full weight of the water and apparatus, it is still four times as energy dense as li-ion batteries.
Even at night ? I think you might have to get up much higher than the clouds. There’s the rub.
Gasoline engines already produce a lot of water vapor in addition to the CO2 produced.
So the real question is how many kilos of water vapor per mile are produced from a hydrogen vehicle (fuel-cell or ICE) compared to the equivalent gasoline vehicle ? Maybe it isn’t a lot more ?
Personally, I don’t think all that water vapor hurts the air quality here in LA at all ! I think the moisture starved landscape sucks it up before it ever becomes a greenhouse problem.
That works for LA. I live in a somewhat more humid environment.
Good point about the water vapor from gasoline engines. I’ve never seen a discussion about the advantages or disadvantages of hydrogen in that regard.
Where are you getting your numbers from ? We have daytime capacity problems, but excess electrical generation capacity at night.
http://www.eia.doe.gov/cneaf/electricity/epa/epat3p2.html
From the above DOE numbers, we have an overall 150,000MW excess generating capacity. If every gasoline vehicle in the country was replaced with either electric and charged at night, or using this aluminum oxidation tech and the aluminum was recycled at night, it would use less than half of the existing excess electrical generating capacity.
I think that that fairly obviously is true. The water, in such case, turns out to be merely a catalyst in a reaction which ultimately just oxidizes aluminum, delivering fuel to an engine or fuel cell, which gives you your water back as steam to be condensed and recycled.
Only if you "combust" it in a pure oxygen atmosphere. If you use air, you also get oxides of nitrogen, NOx.
It's also fuel we could produce right here (the Alumina can recycled), rather than subsidizing the Angry Ayatollahs and Mad Mullahs, directly or indirectly. It also reduces the need to burn valuable chemical feed stocks.
Oh okay, thanks!
Aluminum-Gallium alloy. It might be denser than aluminum, might not. Although a 350 pound block of aluminum isn't as big as you might think. Aluminum weighs 0.098 lb/in^3. Thus 350 pounds would be about 3700 cubic inches. That's a cube about 15 inches on a side. Or 30 inches x 15 inches X 7.5 inches. About the size of a gasoline tank. Put another way, that's about 15.8 gallons, again about the size of typical gasoline tank.
Except that you do have to transport the final product. Since it's solid (pellets), you probably can't move it by pipeline, which leaves trains and trucks. Highways and rail lines are even more expensive than transmission lines.
But that doesn't mean it's not a viable idea, you'd just have run the numbers.
We don’t have to spend a few hundred million bucks defending our access to the raw materials.
This time last century, well maybe a little before, they didn't think fossil fuels would replace oats as a source of power for vehicles.
92 1/2 years is a Long Time.
By then we might be getting the aluminum from the moon and using solar energy to refine it, or the Jihadies may have nuked us all by then. (Presumably we'll have nuked 'em back, unless there's a Rat President at the time, in which case we'd ask why they hate us so much).
Well, you have to go quite aways above the clouds for the sun to be always shining. I guess you could be in an orbit that precessed in a such a way as to keep in aligned with the terminator. Then you wouldn't have to so very high. Be tricky though.
Interesting!
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