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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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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.
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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.
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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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
But it's not one of the major hurdles that needs to be overcome to use hydrocarbons. Regarding the "hydrogen economy," Hydrogen is actually pretty far from ideal as a storage mechanism. Liquid hydrocarbons turns out to be one of the best ways to store hydrogen all around, and the infrastructure's already in place to handle it.
The way to get off "foreign oil" is to produce synthetic octane/diesel fuel. Since it's already possible to do this in a number of ways, the thing holding us back from kicking the oil habit is that oil is freakin' cheap. It's already made, all you have to do is pump it out of the ground. And maybe a little fractional distillation, but that's peanuts compared to the energy needed to synthesize liquid hydrocarbon fuel (or any easily transportable fuel, really.)
We'd all better hope that the carbon trapped in easy-to-get spots is pretty much insignificant atmosphere-wise, 'cause the cat's out of the bag, and it's not going to stop being pumped till it's gone.
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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.
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.
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
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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