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Aluminum Alloy Releases Hydrogen From Water
mdsolar writes "PhysOrg is reporting on a method of releasing hydrogen from water by oxidizing aluminum in an alloy with gallium. In the presence of water the aluminum oxidizes, leaving aluminum oxide, gallium, and hydrogen gas. The Purdue scientists who discovered the effect think this could help to overcome difficulties with hydrogen storage. Quoting: 'On its own, aluminum will not react with water because it forms a protective skin [of aluminum oxide] when exposed to oxygen. Adding gallium keeps the film from forming, allowing the aluminum to react with oxygen in the water.'"
This is a significant breakthrough, not because it enables the hydrogen economy (which is important), but because it makes it a more closed system. In their scenario, the aluminum and gallium are recyclable and more importantly *reusable*. It means that filling stations could exchange your car's waste products for recycled waste products from your neighbour's car. Granted, this has costs. Right now, the costs seem to be the prohibitive factor, but hopefully adoption of the technology will lower them, as it does with most new technologies.
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Is this reusable? I was under the impression that once particles are oxidized, they're fairly difficult to separate. Seems like there might be some weird energy investment issues.
Just another way of converting electrical energy into a form that can be used later.
We need to have a source of reliable cheap electricity to make the aluminum. And we don't at this time.
Dog is my co-pilot.
You could add sodium hydroxide (lye) or another base to the water, to dissolve the oxide layer. Their solution is probably safer, but mine you can buy at the drug store. And fill balloons with the H2. (Oblig warning: NaOH is nasty caustic, and H2 is ridiculously flammable with a *huge* explosive range in air. Don't do this without appropriate safety precautions.)
What I'm actually curious about is why they think this is useful. The energy released only partly goes into cracking the water; an awful lot of it comes out as heat, which is both wasteful and has to be removed from the system. And all that energy came from electricity to refine the aluminum from aluminum oxide ore. It seems to me you should just ship the electricity in the normal manner and use it to charge conventional batteries, which have really gotten rather efficient lately.
Check the price on gallium. It's about $500 per kilogram, although there was a price spike a few years back and it passed $1000. It's a trace component in bauxite and coal. Way too expensive to be used as a fuel component.
Gallium is so expensive that it's not even cost effective in solar cells, where it works very well.
While I applaud the science, I doubt this is the "hydrogen revolution". It seems to be that we're suddenly talking about powering our cars with water (cheaply available) and massive blocks of a aluminium/gallium alloy. The article seemed to put forward the view that water was the fuel and the alloy acted as a catalyst. While this is indeed CHEMICALLY what is happening it's the cost of the catalyst driving (no pun intended) the reaction that's going to keep this off shelves for a while.
When/if they come up with a method for reactivating the alloy which is a) cheap and b) simple, then you can colour me interested.
Godless heathen.
The aluminum smelting process requires vast amounts of electricity.
quoting a random googled page : "On average, around the world, it takes some 15.7 kWh of electricity to produce one kilogram of aluminium from alumina. Design and process improvements have progressively reduced this figure from about 21kWh in the 1950's."
so it doesnt matter that it produces hydrogen. It's almost assured coal equivalent to or greater than the tank of gas it replaces was burned somewhere to get the aluminum.
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Except that storage is one of the major hurdles that needs to be over come to use hydrogen.
With this, the car's power source has been decoupled from our choice of power supply. We can use what ever source for energy to turn the 2Al2O3 back into 4Al + 3O2. Today we can use coal burning plants for the electricity, tomorrow nuclear, the next day solar and wind, the next fusion. You don't need to upgrade your car every time we invent (and/or make economical) a cleaner power source.
"You saved 1968." - Ms. Valerie Pringle to the crew of Apollo 8
So their process uses as much power as they put in and they are basically hoping for free electricity to make it commercially viable. Because the anti-nuclear wackos are never going to let nuclear reactors to be built *anywhere at all*, the chances of building one cheaply is nil. Some folks even object to windmills and will tie then up in litigation forever. So forget that too. That leaves coal, natural gas, and oil (or hydro - but we don't build damns anymore, because it hurts the fish).
They might as well use the imaginary nuclear reactors to directly power electrolysis of water and skip the aluminum. I'm not sure that hauling around several hundred pounds of aluminum beads is any easier than hauling around compressed hydrogen.
Making aluminium out of any aluminium ore (including oxides) takes big frickin' huge amounts of energy.
Wake me again when they have found some sort of catalyst that works with the reaction
2 H2O + (some sort of cheap, abundant energy, preferably heat or sunlight, definitely not electricity) -> 2 H2 + O2
Call me a optimist, but instead of developing indirect ways to make energy, why dont we just focus all of our attention on developing non-toxic and high energy density batteries. We do have nuclear power plants after all which are not only zero emissions, but also can provide energy worldwide. Personally, if we can put a man on the moon and bring him back safely in under a decade during the 1960's, I think we can probably develop a battery that we can use in your cars of the future....
How do you do this?? Simple... Challenge and encourage NASA, DARPA, DOD, and all university/research centers to focusing specifically on this one goal... Put out in specifications of what it means to achieving this goal and wait to be stunned by the wonder of human ingenuity. Commit huge amounts of money to the grants for such things.... That would assume, though, that we have an administration that is willing to commit to doing this. Something that until now we are unable to do....
The above is why I could never do post-graduate work. I'd love to do research - but the idea of having my discoveries and/or inventions stolen by some ossified... err.. tenured relic because that's just the way the system works just makes me angry.
All these nutty attempts to build and maintain a whole new infrastructure with dangerous, poisonous, chemicals and just as dangerous high pressure wessels, and biodiesel produced from algae(as opposed to the stupidity of using corn and sugar), using what we already have to refine and transport it, never even gets an honorable mention. We could be using the stuff right now if it wasn't for our infatuation with pop science from "beyond 2000" distracting us from putting a very workable system into place with minimal costs and low risks to the environment, and to humans.
What?
The basic reaction is:
2Al + 3 H20 -> Al2O3 + 3 H2
Aluminium has an atomic mass of about 27, so 54g of Al will produce 6g of H2, i.e. it takes 9kg of Al to produce 1kg of H2. (We haven't been told how much gallium is required in the mix, so I'm ignoring this component.)
According to Wikipaedea, the goal for hydrogen storage in 2015 is 0.09 kg H2/kg. This process rates at 0.11 kg H2/kg before accounting for the gallium - so it is looking pretty good so far.
I've neglected the weight of water used in the reaction. If we include this, it doubles the required mass: 54g Al + 54g H2O to produce 6g H2. We may be able to recycle the engine exhaust to provide the required water. However, this scheme means that you gain weight as you run your car: everytime you use 6g of hydrogen, you turn 54g of Al into 102g of Al2O3, which you are still carrying.
I'm also worried about the efficiency of the fuel cycle, which will require returning large amounts of Al2O3 from fuel stations to a recycling plant, which then uses electricity to convert the Al2O3 back to Al.
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Wikipedia has an article on the Hall-Héroult process, the major method used to refine aluminum oxide into aluminum. Ill save you the time.
"In the Hall-Héroult process alumina, Al2O3 is dissolved in a carbon-lined bath of molten cryolite, Na3AlF6. Aluminium fluoride, AlF3 is also present to reduce the melting point of the cryolite. The mixture is electrolyzed, which reduces the liquid aluminium. This causes the liquid aluminium to be deposited at the cathode as a precipitate. The carbon anode is oxidized and bubbles away as carbon dioxide. The electrical current used by many smelters, has a very low voltage, but massive amperage. This is typically 3-5 volts, but 150,000 amperes."
So now were back to greenhouse gasses and massive amounts of electricity.
Rust never sleeps.
Have gnu, will travel.
According to the Union of Concerned Scientists, 1000 Megawatt coal plant produces 250,000 tons of ash and 486,000 tons of sludge in a year.
So on a strictly weight-for-weight basis, nuclear is over 22,300 times cleaner than coal per megawatt. The nuclear waste is also highly regulated with stringent disposal requirements (if our politicians will get off their duffs and decide on a place to put it). A large portion of the ash and sludge from a coal plant is simply disposed into the atmosphere or sent to landfills where it ends up in our lungs and our water.
Yes, yes, everyone wants near-zero emission renewable energy. But given that that is currently not cost-effective enough to compete with coal, nuclear is a tremendously cleaner stepping stone that's available here and now, while we do the R&D to get the renewable costs down to where they're competitive.
While it is true that Aluminium smelting uses up a lot of energy, the rest of the process is remarkably pollution-free (most of the catalysts are recycled and reused in smelters). As for the energy, there are places in the world that produce vast amounts of clean energy that is used for aluminium smelter. One example of this is Iceland (where I live).
Interesting link, but the aluminum-air battery appears to be only about twice as power-dense as zinc-air, which is an established technology used primarily in hearing-aid batteries. Neither seems likely candidates as secondary cells, which is what we really want.
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Just to add some information, the reference to how much waste a 1000MW nuclear plant produces is wrong. With reprocessing, most of the 33t of "waste" is reusable.
e ssing
:) the sarcophagus of the reactor! With this surprisingly great news, maybe the only way to save the Amazon is to dump nuclear waste all over it - sad but true.
http://en.wikipedia.org/wiki/Nuclear_power#Reproc
So assuming just 90% is reused, that results in about 3.3t of actual waste. 3.3t at that densities is less than 0.5 cubic meter. That's one barrel of waste for 1000MW or 1GW power plant per year. And without reprocessing there is enough Uranium and Thorium for few hundred years. With reprocessing, there is enough for a thousand years or more. But then I'm sure we'll be able to come up with Shingle Solar Panels on every roof and fusion so no problem.
PS. For the radiation worried crowd - the Chernobyl disaster actually *saved* the environment around that town. The no-go zone is now one of the best animal and bird sanctuaries in Ukraine and surrounding regions. Endangered birds are now gaining in numbers even having their nests *inside* (well, on the building, not where the core is
Name one situation, ANYWHERE, that you get more energy out, than was put in. That would be called PERPETUAL MOTION or perhaps COLD FUSION.
The fact that hydrogen doesn't violates all known laws of the universe is a good thing, IMHO.
No, it certainly isn't.
Gasoline is currently cheaper, no question, but it's going up all the time, and the idea is that developing better and newer methods of hydrogen production will lower prices.
Internal combustion sure as hell isn't anywhere near as efficient as a hydrogen fuel cell.
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Aluminium is extracted via electrolysis and takes masses of electricity to produce. Hope you're adding this energy into your "zero sum".
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