So the Army seems to have stumbled upon a new variant of aluminum which perpetually releases hydrogen without oxidizing the metal.
Apparently they are saying that this will revolutionize the creation and use of fuel cells. So my question is why won’t this work? Tell me all the reasons that this won’t be a huge change in allowing the hydrogen economy to move forward.
Nifty, if true… But where does the energy come from? I’m mighty dubious here.
Cold Fusion all over again? Or something really useful bequeathed to us by the quixotic natural world?
Sounds impressive. Let’s hope it scales up well.
Ok - so the nano-aluminum is not oxidized, but somehow it splits water into oxygen and hydrogen. AND it’s an exothermic reaction? Presumably, since aluminum is not being changed, that goes on forever?
Congrats, you invented perpetuum mobile. Too bad you can’t patent it, since perpetuum mobile designs are not patentable.
Both articles have scanty information, much of it seems inaccurate. They may only have a nano-aluminum compound that rapidly releases hydrogen from water. This is what ALICE rocket propellant does. Calm the reaction down to a reasonable operating temperature and you have a simple water based hydrogen generator. If this reaction is also releasing oxygen instead of it combining with the aluminum then they’ll have to explain some miracle.
Here’s the Army’s news releaseabout it, which at least makes clear the hydrogen is coming from the water.
It says, as long as there’s water, the alloy will keep breaking it down without oxidizing.
Sounds interesting, but forever is a long time, and it doesn’t say whether the reaction can be controlled or regulated.
It’s pretty clear that the aluminum is oxidized, but in a way that doesn’t prevent the reaction from continuing. Normally, a tiny amount of water would react, and then the aluminum would be coated with the oxide, and then nothing would happen. With small enough particles, or something that prevents the oxide from sticking, the reaction could keep going.
Still seems pretty inefficient. The end-to-end efficiency of running an (electric-powered) aluminum refinery, then using this method to convert that energy into hydrogen is probably well under 50%. In fact they say that the reaction is highly exothermic; perhaps some of that heat could be recovered, but you’ll lose most of it.
Might be useful when high energy density is more important than other factors.
So, anybody gonna start guessing the elements of the alloy? Becomes much less exciting if it’s a precious metal, I guess.
A response to a comment on the video on YouTube https://www.youtube.com/watch?v=oAE407SjFPM
Yes, it’s obviously not about the aluminium functioning as a catalyst, but about it reacting without that pesky oxide layer forming to prevent further reaction:
And if this part holds up in large scale applications, and a way can be found to discard the oxide and refill the aluminium, it would be a good way to fuel future fuel-cell cars:
My, possibly mistaken, impression is that the process eventually consumes the aluminum.
It has to consume the aluminum. The innovation is that a passivating layer is avoided.
Obviously the aluminum is consumed. And it takes a lot of electricity to reduce the oxide. But the point seems not to generate power for free, but for use in a fuel cell, a different proposition. All batteries are inherently inefficient, but efficiency is not the issue here. Just that it goes on producing and then you replace the aluminum.
I was going by the OP’s “without oxidizing the metal” statement.
But ok - this is just the regular aluminum oxidizing reaction that releases hydrogen. The article cited says "“Also, it is very fast. For example, we have calculated that one kilogram of aluminum powder can produce 220 kilowatts of energy in just three minutes.”
That doesn’t sound like something very battery-like. I mean if you use the whole thing at once - in three minutes - then the hydrogen collected would probably be useful in a regular hydrogen fuel cell, but you need some way to collect it and compress it to store it, and I am not sure how the thermal energy could be efficiently stored.
And if you have some kind of controlled release of small quantities of the material into water so that hydrogen is basically produced on demand, I am not sure how that can be done in a reasonably small self-contained battery.
This doesn’t sound like a good method to produce batteries. It could be a good alternative to hydrogen-generation-and-distribution - for example, instead of producing hydrogen, then distributing it to hydrogen-stations to be used in hydrogen-fuel-cell-powered cars, distribute this nano-powder to generate the hydrogen on demand and in situ.
What in the world does it mean that it produces “220 kilowatts of energy in three minutes”? While they’re at it, why don’t they give us the mass of the aluminum in feet, or the time in liters?
Science “journalism” at its best. :rolleyes:
Unit issues aside…
If my envelope scribbles are correct, and if you get full conversion, you’ll need 9 kg of Al and 9 kg of H2O to get 1 kg of H2. That seems like a lot of mass to carry around but hydrogen storage seriously sucks. A type IV tank for 700 bar storage weighs about 25 kg for every kg of hydrogen stored.
Hydrogen has an energy density (HHV) of 142 MJ/kg.