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.
fat chance you’ll be driving a car with that anytime soon.
Nope, recycling aluminum is just melting it (to a first approximation), but reclaiming this alumina back into aluminum metal is equivalent, minus mining expenses and separating the alumina from the ore, getting the aluminum from the alumina in the bauxite ore in the first place.
I think I said that
That answer is pretty easy. The cost of the aluminum
The answer isn't easy at all. The current cost of aluminum is based on the current demand for aluminum. Refining aluminum from aluminum oxide requires a LOT of electricity and currently there is not much excess capacity in the US electric supply, so if you start using aluminum as an energy carrier, then the demand for aluminum (actually the electricity to make it as well as the facilities to refine it) will vastly increase, shoving the transportation energy demand back on the electric grid which just doesn't have the capacity. I read somewhere that replacing the transportation energy demand with electricity would need about 200 new nuclear generating stations. That is why that even if this is technically feasible (and how do you get rid of the solid waste produced? Big recycling costs associated with the recapture of the al2o3), it isn't economically feasible on anything but a demonstration scale without the electric generating capacity to back it up.
“Above the clouds, the sun is always shining...” is a lyric from an old gospel song.......
Air conditioners and refrigeration systems can run on ammonia like they did before DuPont invented Freon. That requires heat to boil the ammonia to make it a gas. The waste heat from the chemical reaction could be used for that, as could the exhaust.......
People keep saying we don’t have the electrical generating capacity, but the DOE numbers disagree. Look at the numbers in the link in post 108.
We may not have excess capacity on summer days during peak demand, but the overall excess capacity is 20% — in 2004 that was 150,000MW excess capacity.
If used to charge electric vehicles, that would be enough for 100 million cars to drive 100 miles every day. This aluminum oxidation process feeding hydrogen to an internal combustion vehicle is much less efficient than an electric car would be, but it still works out to 36 miles every day for those 100 million vehicles. Those would be expensive miles — equivalent to $5 gasoline — but there are many options to producing electricity compared to finding more petroleum.
You are correct that supply and demand will drive up the price of electricity and therefor aluminum if this were to be widely adopted. If it were widely adopted, however, and demand fell for gasoline then oil prices would fall. It would be impossible to switch everything overnight, so the volatility in price would be minor and spread out over decades. All the while, that additional generating capacity you talk about will be coming on line, right ?
As far as the “waste” goes, in the vehicle, the fesh aluminum moves from its tank, to the reaction chamber, to the alumina tank. Filling stations pump out the alumina at the same time they pump in new aluminum. Tanker trucks pick up the alumina when they deliver new aluminum, compared to leaving empty after delivering gasoline. More expensive than dead-heading back to the depot, but not all that much more.
The other peculiar thing about aluminum is that you can’t shut the refineries off. If they cool down for more than 4 hours the aluminum solidifies necessitating a complete rebuild of the tank. and about power, we may have enough peaking capacity (read expensive electricity), but is the base load capacity there? The cost of electricity varies form moment to moment as the generation mix changes during the day. Electricity must be generated in exactly the amount used; there really isn’t any storage any significant increase in al production is going to drive the cost of electricity up and decrease the reserves.
Actually, I think the excess capacity is all at night and the baseload capacity is more than the night-time demand.
So as long as you do your aluminum recycling at night, you are ok ;-) The author does make the point that new generating capacity dedicated to aluminum recycling would be best. I’m just saying we have some excess capacity that could be used without waiting for that.
Controlling the reaction to provide the amount of hydrogen needed according to varying demands of the vehicle seems like it is left out of the article entirely.
It wouldn’t make sense for the reactor to be a single big tank where all the aluminum and water is dumped at once. Similar systems that I’ve seen move the reactants together via screw delivery systems into the reaction chamber. So you can move only as much as necessary to provide the hydrogen output needed at that time, and few of the aluminum pellets would be wasted when the reaction (and vehicle) are shut down. Just those remaining in the reaction chamber and flushed out with water into the alumina waste tank. Maybe not even those, if the reaction is allowed to continue and the hydrogen from those last pellets is compressed for storage in a relatively small gaseous hydrogen tank. I think a vehicle reactor would need to do that anyway, so it could produce hydrogen at an average rate and temporarily store it to meet the varying demands of the vehicle.
I would be much more expensive transporting aluminum over the road than electricity over the wire.
If you have aluminum, you have 1/2 of an aluminum air battery. You do not need a fuel cell. Look up mechanically recharged aluminum batteries. They have been around for 40 years.
If someone ever figures out how to keep an electrically rechargable aluminum battery from gelling up, we would not even need gasoline. It would provide about 10 times the capacity of the best lithium battery.
I only have high school chemistry but know you don’t get to split water, make hydrogen, for free. It takes energy and in this case it’s supplied by aluminum which is quite expensive. In supplying this splitting energy the aluminum becomes aluminum oxide. To reuse the aluminum oxide you turn it back into aluminum by electricity.
I fail to see what’s so clever about this scheme
thanks, bfl
Nothing that I can see either other than it may be more energy dense than batteries. For that matter you could run a car on calcium carbide and water, but no one does it. might be a good test bed for this process
Instead of using electricity to make hydrogen by splitting water, this process uses aluminum which itself is made by using electricity, to make the hydrogen. So same or more probably more electricity is used to make the hydrogen.
Look up powerchips.gi
You got to be a little careful with that number. A lot of those MW are in very old plants, many of them small (less than 1 MW industrial units) that are rarely utilized because of their high costs, fuel type (lots of diesel or or distillate) and poor emission profiles. They contribute little but remain "on the books" as part of the installed base.
The real issue with generating capacity today is the need for new baseload power plants --- those in the 700 and 1200 MW range, that can generate power around the clock for 2-3 cents/kWh. (That's new coal and nuclear units.) Our baseload demand keeps growing as population and economic activity grows and that's the segment of the fleet we need to focus on now. The 90s saw large growth in gas turbines for both simple and combined cycle plants, but with high natural gas prices now, we don't want to rely on those for baseload power. They work very well for cycling and peak power operations, but they are too expensive for baseload operation.
Or thermite.
I think is magnesium oxide and aluminum powder.
Do you have any idea how expensive solar power really is? If it made financial sense, you wouldn’t need the government pushing it.
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