Purdue Process Generates Hydrogen from Aluminum Alloy On demand Hydrogen for cars)

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.

"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.

So where's the savings? I already get around 450-480 miles to a tankfull of gas and even at $3 a gallon it still only costs around $50 to fill up.

The savings will be there when gasoline hits $15 a gallon. Once the population of China and India own cars at the same rate that Americans do we will see the price of gas shoot up to astronomical figures.

Its simple supply and demand.

“A midsize car with a full tank of aluminum-gallium pellets, which amounts to about 350 pounds of aluminum.”

I wonder how much water, which would need to be stored in a separate tank until needed, is required to use up all that aluminum? I guess I should really ask that the other way around, since it is the water that is the source of the hydrogen fuel. Seems heavy compared to the 80 lbs of gasoline or so I carry in my car’s tank, but maybe the fuel cell would be sufficiently lighter than an internal combustion engine to make up the difference.

which amounts to about 350 pounds of aluminum, could take a 350-mile trip and it would cost $60

Interesting concept, but I don't see me shoveling 350 lbs of aluminum pellets into my car to drive it for a week. Process needs to get far far more efficient to be useful.

I’m also wondering about the efficiency of this cycle. The article states that considerable heat is also liberated in this reaction - how much, and is it of any use? I guess it might be useful for heating the car in the winter. How efficient is the process of reforming the aluminum oxide back to aluminum? The devil’s in the details with these schemes. Of course, it’s not hard to beat the 25% (or so) efficiency of the gasoline powered internal combustion engine.

The article states that considerable heat is also liberated in this reaction - how much, and is it of any use? I guess it might be useful for heating the car in the winter.

The other problem is how do you dispose of the solid "ash" Al₂O₃ Without looking up the bond energies and doing the calculation I'm guessing with you that there is a lot of waste heat in this operation. My idea is to run a car on water and calcium carbide Then you have to dump the Ca(OH)₂

Yes, smelting aluminum is extremely energy intensive. That’s why many of the major aluminum producers have been in places like Quebec or British Columbia, located nearby to major hydroelectric facilities. That’s despite the fact that the bauxite comes from the other side of the world.

I wonder how the energy intensity differs for "virgin" aluminum as opposed to remanufacturing the resulting aluminum oxide back into the pellets. I'm sure there would always be demand for new aluminum sources for vehicles under this scenario, but at some point, most of the production would be aluminum oxide back to pellets.

Lots of great comments on this thread. I don't know what the result of this research will be, but the thought of driving in clean, silent, vehicles fueled by non-volatile expendables is pretty attractive, even if the cost is higher than gasoline.

Drivetrains for electrics are generally lighter (not counting batteries) than their IC counterparts, have great torque from a start, and need minimal maintenance. Then there's the lack of need for oil changes, coolant, and lots of other things that leak and pollute and far fewer moving parts that aren't trying to contain explosions.

Two things I am curious about...

Could any of the water that occurs as a byproduct of combustion be used in the aluminum/hydrogen process?

How reactive are those pellets to the humidity in ambient air, such as in Florida?

From your comments I gather you don’t believe recycling the aluminum as mentioned in the article is feasible?

Obviously not. Once it's burned, then it becomes aluminum oxide that has to be re-reduced electrically to metallic aluminum; that -1600 kJ/mol again.

Seems like the extra cost of transporting 350 pounds of aluminum pellets (plus some amount of gallium) from the nuclear reactor would be significantly higher than current transportation costs for an equivalent amount of gasoline (say 20 gallons at about 120 pounds). Plus the used Al has to be transported back. Six times the transport costs of gasoline...

Plus, we would be transporting a whole lot of water. Interestingly, the process requires approx. equal masses of Al and water. So the 350 pounds of Al requires transporting an additional 350 pounds of water (42 gallons).

Finally, if the water is emitted as steam won’t the global warming freaks be offended? Isn’t water vapor a potent greenhouse gas? Or maybe we can extract the heat energy and emit the water as liquid. Crowded highways will be permanently wet as each car on the road dumps a gallon of water on each 8 miles of highway (this may not sound like much, but consider a heavy traffic day with 75 cars per minute - this would be the equivalent of 1/3 inch of rain per day on the highways).

That said, if the process could be made more efficient (smaller Al-Ga granules to increase surface area) and possible recycling of exhausted water to reuse in the process) there may be a point where it becomes at least somewhat useful...

Process needs to get far far more efficient to be useful.

Of course, but it's not a bad start for a new idea. Give it a few years and see where it lands.

I don't see me shoveling 350 lbs of aluminum pellets into my car to drive it for a week.

I don't either. It's probably be more like a large bin elevated above your head, you pull a lever and the pellets slide down into the holding container. The water can be pumped in like gas is now, or simply dropped with the pellets. (from a separate bin... don't want them reacting before they get put in the cars!)

How would the by-product alimuna be removed? My guess: you flip a lever on the car's container (before re-filling) and it all drops out into a pit in the ground, like a Jiffy Lube basement. let gravity do all of the work.

Anything to make the Middle East (and Islam) irrelevant again!

Once again, hydrogen is not a source of energy. It is a store of energy. Now we add some arm waving as aluminum is inserted in the storage chain. Aluminum has to be converted to metallic form using lots of electricity. That returns to the baseline issue of what energy source generates the electricity. It still comes down to oil, coal, hydoelectric or nuclear.

The energy path is now {oil,coal,hydroelectric,nuclear->electricity)->aluminum->water hydrolysis->hydrogen. There is a energy conversion loss at every step. This proposal is just making the aluminum alloy into the store of energy. Aside from a safer way store energy than gaseous hydrogen, I see little merit in this invention. The "waste" product will need to be recycled as you are no longer just generating CO2 and H20 as you drive.

Finally, if the water is emitted as steam won’t the global warming freaks be offended? Isn’t water vapor a potent greenhouse gas?

That’s always been my first question regarding the use of hydrogen in vehicles. The increased production of the greatest greenhouse gas there is never seems to be addressed in any of the hydrogen schemes. If there is concern about a minor greenhouse gas like CO2 then you would think the greens would be falling all over themselves to prevent the use of hydrogen.

All of this is fine and dandy, provided you have plenty of electrical capacity. I submit, that we need a HUGE investment in Nuclear Powerplants. Once we have enough spare electricity, we can create whatever fuels we need, and make everyone pretty happy.. I am dismayed that the GW fanatics don’t jump on this bandwagon.

I read the article and wondered about this quote:

“Recycled aluminium requires only 5 per cent of the energy required to make “new” aluminium. Blending recycled metal with new metal allows considerable energy savings, as well as the efficient use of process heat. There is no difference between primary and recycled aluminium in terms of quality or properties”.

Does this not apply as regards the recycling mentioned in this article?

The real way to compare is to compare the amount of energy in the hydrogen vs the energy in the gasoline, and then feed that into the efficiency of the hydrogen-to-wheel power transfer vs gasoline-to-wheel transfer.

That's not a fair comparison. It leaves out all the conversion losses incurred in generating the hydrogen. A fair comparison would start at the primary source of energy and include all the conversion losses on the way to the wheel. Gaseous hydrogen is hard to store. You can lose half a tank in a week without driving anywhere. That is also a loss in the total chain from primary energy to the wheels.

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