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.
No, because recycling metallic aluminum just involves remelting the already metallic form. When it's used in as fuel it goes to aluminum oxide, and needs the whole energy input of the original smelting/refining process to change it back form oxide to metallic aluminum. Currently about 15.7 kwh/lb.
Advocates can say that with quantity, the price will be lower. That is true, but not by very much. About 30 years ago, Daniel International was building a standardized plant called SNUPPS (Standardized Nuclear Unit Power Plant System). One is located in central Missouri and one in Kansas. I had friends who came to work on the Missouri plant and later moved to work on the Kansas one. They did not report any cost savings. In fact, the construction of the plant takes so long that one of the biggest cost variables is the impact of inflation on the cost of materials. For example, the price of concrete was substantially higher at the end of construction on the Missouri plant than for the first pour.
Just as people might speculate that stamping out nuke plants is just like stamping out widgets, nuclear power may cost out in a simple calculation, but I was raising the idea that there will be consequences to the rest of the capital market when 1/2 Trillion is priced so that the capital market will accept the deal. And the cost of the plant's electricity will be priced to make the plant pay. Wishing it will be a low number cannot change the hard economic truths such projects face.
Nuclear power plants are just giant consumers of capital- capital that is entirely at risk until payback is assured. The biggest municipal bond default in US history was a failed nuclear power project, the Washington Public Power Supply System (WPPSS).
It might be noted that if the aluminum and copper refining industries were moved off earth, off the grid, about 1/3 the power usage of the grid would go with them.
Thanks for the info. I was trying to reconcile what you’re saying with the quote in the article. Presumably then, they are talking about such things as aluminum scrap. I doubt there’s enough of that to fuel all the vehicles or even a significant number of cars on the road. I would note however that they proposed as the initial use of this technology small engines such as lawnmowers etc. If that is all it ever amounts to then perhaps there would be enough recyclable aluminum for that purpose.
It seems to me there are too many “ifs” for this process to be practical any time soon. 1) if enough gallium exists 2) if the gallium producers can be induced to produce more 3) if the price of gallium will drop in the face of increased demands 4) if fuel cells can be perfected for optimal size, weight, robustness, cost 5) if nuclear power plants can be built 6) if the Greens will agree to nuclear plants 7) if an infrastructure will be built to handle the aluminum pellets and exausted by-products.
Yep, a lot of ifs but no more so than any other major engineering project. This is just one of a whole boatload of ideas about how to make hydrogen useful anyway. It’s not the definitive answer by any means but we’ll be shifting away from oil in my lifetime and this idea will get thrown into the hopper with all the rest.
News to me. I melt Aluminum far too regularly (Unintentionally welded a worn end mill into a block just last week). Guess I'm just lucky.
I believe the ignition point of Aluminum is quite a bit higher then it's melting point.
News to me. I melt Aluminum far too regularly (Unintentionally welded a worn end mill into a block just last week). Guess I'm just lucky.Ooops....meant to say water. But it's the oxygen it's reacting to.
I spent about seven years in the secondary aluminum (scrap melting) industry. You have to be very careful about making sure your charge materials are dry, and especially sure that no water gets trapped and submerged under the molten metal bath.
-Eric
The molten moment was short.
This might work for non-air, commercial applications, but I don’t see it for private cars or air transport. Size and weight are important, and this has a great disadvantage in both.
Hydrogen is perhaps the most difficult stuff to store and transport in existence (except for Plutonium or U235) because of its immutable physical characteristics.
It cannot be liquified at any reasonable temperature (or cost) for general use, and cannot be solidified. It will form an explosive mixture in air over the widest concentration range of almost every other gas, making it extremely dangerous in closed areas.
As a metal (electron donor) it penetrates and dissolves (embrittles) metal tanks and pipes. As the physically lightest molecule, it has the highest average velocity, and diffuses through any flaw or weakness in containment. And an indicator gas, such as is added to natural gas to warn of leaks, would not penetrate the same flaws to provide such a warning.
1. Petroleum hydrocarbons are the second most abundant source of hydrogen on Earth, after the oceans.
2. Gasoline is a mixture of hydrocarbons - chemically similar molecules, all with a straight or branched chain of carbon atoms, plus a number of attached hydrogen atoms. Collectively, all can be represented by the generic formula:
H - (CH2)n - H
where “n” can be any number up to perhaps 40 or so. The lightest is Methane (CH4), the major component of natural gas. Carbon has an atomic weight of 12 and Hydrogen 1, so Methane has a molecular weight of 12 + 4 = 16, 25% of which (by weight) is Hydrogen.
3. Propane, which can be liquefied at ambient temperatures and relatively low pressure, is C3H8, with a molecular weight of 12 x 3 + 8 = 44, and is 18% Hydrogen by weight. This light hydrocarbon is produced as a byproduct of petroleum refining.
4. Gasoline is a mixture of medium weight liquid hydrocarbons, but can reasonably be represented (on average) by Octane, C8H18, which has a molecular weight of 8 x 12 + 18 = 114, and is 15.8% Hydrogen by weight.
5. One “mole” of Hydrogen gas at Standard Temperature and Pressure (STP = 68F, 14.7PSI) has a volume of 22.4 liters (5.92 gallons) and weighs 2 grams. Liquid Hydrogen has a specific gravity of 0.070. This means 1 liter would weigh 70 grams, and 22.4 liters would weigh 1568 grams.
6. 5.92 (we will use 6) gallons of gasoline would weigh approximately 6 x 8 x .75 = 36 pounds, x 16 oz/lb x 25.4 grams/oz = 14,360 grams. 14,360 x .158 = 2269 grams of Hydrogen, in the same space, without compression.
7. 2269 / 2 = 1135, x 14.7 = 16,677 PSI pressure required to achieve the same density of Hydrogen in the same size tank. This would be 2269 / 1568 = 1.45 times as dense as LIQUID Hydrogen, and far beyond current production technology.
8. Low molecular weight hydrocarbons are the most efficient way to store Hydrogen that God ever designed, and if you want something better, you should ask Him to do it. According to His rules, the fuel of the future will not be much different from what we use today, whether we continue to find and refine it, or manufacture it from other sources of Carbon and Hydrogen.
NOTE: I realize that I used a mixture of units, but I wanted to use familiar terms and measures where possible for clarity, while using constants and characteristics that would be easy to verify.
Car and aircraft manufacturers obsess about weight, and adding hundreds to thousqands of pounds to each vehicle is futile. It might work for trains, boats, trucks, and buses.
The billions spend on monitoring the middle east. Just because you don’t see it directly effecting your wallet, doesn’t mean it doesn’t.
That being said, I think we need something as closely cost competitive as petro...but it would be good enough to me if it was mildly more expensive.
Gallium is something like $180 per pound.
Roughly 17 gallons; as pellets, shape wouldn’t matter much.
Purdue ping!
I think the weight of 350lbs was for the complete hydrogen generation system, including 60 pounds of aluminum-gallium pellets, water, and associated apparatus.
A 20 gallon tank of gasoline weighs about 180lbs, so the 350lbs total weight jibes with his comment that it would be like carrying an extra passenger around — 350lbs - 180lbs = 170lbs extra.
As far as combustion vs. fuel-cell for getting energy out of the hydrogen, I think the article is pretty clear. He is talking about immediate uses — combustion by relatively minor changes to ICE engines to run on hygrogen — and then longer-term use via fuel-cell and electric vehicles when/if fuel cells ever become economically viable.
As far as recharging via replacing 60lbs of aluminum vs. swapping battery packs goes, it is all about the value and mechanics of what you are swapping. Battery packs to get you 350 miles cost thousands of dollars, and they have a lifespan to them, and they would weigh many times more than 60lbs. Nobody wants to swap out their recently purchased battery pack at a “gas station” and get some worn-out replacement battery packs in exchange. The 60lbs of aluminum is not some big block of metal that you have to lug around, but a slurry of tiny pellets that can be pumped almost as though it were a liquid.
This seems very promising to me. It allows for conversion of existing vehicles away from petroleum. It allows for a high energy density without the storage problems of compressed of liquified hydrogen. It allows a single fuel carrier to work with older vehicles and eventually fuel-cell vehicles. It does seem to generate a lot of waste heat, however. Good for winter and cold climate driving, but difficult to make use of otherwise. Maybe a small Stirling engine to drive all the accessories ?
Ordinarily, when aluminum reacts with air, a coating of aluminum oxide (aluminum rust) forms on the outside. This is why aluminum goes from being really mirror-shiney to dull if left unprotected.
In the article, the gallium prevents the coating from forming and the pellets have a lot of surface area compared to their weight and volume. So the alumina sloughs away instead of coating the pellets, constantly exposing new aluminum to the water where it reacts to pull the oxygen away and leave the gaseous H2 behind.
Thanks for taking the trouble to reply, but that wasn’t my doubt. Someone mentioned earlier that [pure] molten aluminium is an explosive when it reacts with oxygen.
The point is that the aluminum is a carrier of energy — the electricity used to make it. It won’t give up that energy like a battery, but can be used to separate water into hydrogen and oxygen.
So it is an energy carrier, and the question is how much it costs for the energy retrieved later. That answer is pretty easy. The cost of the aluminum. Which is currently about $1 per pound. That cost includes the cost of the energy embedded in the aluminum when it was made. Used in an ICE engine, the article says $60 worth of aluminum would drive a mid-size sedan 350 miles — about 17 cents per mile. Assuming the mid-size sedan would get 30mpg on gasoline, it would take 12 gallons to drive 360 miles, which would be like $5 gasoline. That’s why the article says it isn’t competitive with gasoline at current prices. The cost of aluminum used must come down, or more energy must be usable from the hydrogen as in a fuel-cell compared to combustion in an ICE.
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.
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