Science/Engineering/Technical forums

Did you know you can run your car on water - well Aluminium and water - Aluminium burns in water and uses the Oxygen molecule and leaves the Hydrogen free and you can use the Hydrogen as fuel - you can even heat your home in winter with discarded coke cans. Not an energy effcient reaction but cheap - the byproduct is bauxite and water which you can drink.


http://keelynet.com/energy/cornish.htm

Well, sort of. It would not really be running on water (the energy of splitting it is a cost, not a benefit), but on oxidizing aluminum. Pretty poor cycle efficiency considering aluminum ore is reduced in molten bath by electricity input made at sub 50% thermal efficiency to begin with. I'd have to go search again, but a guy in the semi fab business patented (worst kind, a submarine patent filed early and modified till the time was right to make it public) on using Gallium-Aluminum with water to do this. The Gallium dissolves the aluminum enough to spoil the protective oxide coating, and let aluminum show just how reactive it is at valence 3. Very good power to weight ratio, the gallium is not consumed, and the by product is alumina to go back to the refinery (and be converted back at very-sub 40% net energy efficiency using electricity made usually from fossil fuels).

Note that the reaction of Al with anything is very exothermic itself (example:thermite!), and when that something is water based, nearly all that energy is wasted as well. It's quite easy to get an HCl solution boiling with more than hydrogen output by putting Al into it. Or for that matter, an NaOH solution. Schemes that only recover the hydrogen miss out on a lot of that.

I see all this as probably a waste of net energy -- see the numbers -- with the big deal being stored power to weight ratio being really good compared to batteries, something I'm quite familiar with having run on solar PV panels since 1979 and having built a couple small electric cars. To paraphrase Churchill, batteries are the worst thing there is -- except when compared to everything else. My work in engineering body worn electronics (prosthetics usually) has taught me that they truly stink -- all kinds I've used so far; haven't done sodium sulfer or vanadium redox, the latter of which look interesting for solar systems where weight doesn't matter...

Boy, when those plug-in hybrid cars get a little life experience like I've had -- there's going to be the backlash from hell on them when people find out how optimistic those cycle lives are in real life. Decades of actual, honest testing here show that the manufacturers claims for *all* battery cycle lives are total marketing baloney -- and that's putting it very nicely. Anyone who owns battery powered tools -- did you get anything like the number of recharge cycles claimed for that battery tech? Did you get half that? At half that, did you get full capacity, or maybe more like 20% of the new? I know the answer....most don't keep track, but if you use them such that you're recharging once a week, do you have to buy fresh ones yearly, or nearly so? Eg in 50-70 cycles, not the 300-700 claimed for the technology?

That's the beauty of either the Al based schemes or the vanadium redox batteries -- if you accept a high loss factor, at least they don't degrade over time so badly, because the battery itself is inert, and is basically a fuel cell.

Doug - using discarded coke or bear cans while not energy efficient, is cost-effective in terms of cheapness for the guy who collects them.
I accept the energy cost but items that would be otherwise lost to recycling is fare-game.

No question, but but just for your information, the energy costs of making Al from ore are so much higher than from remelting beer cans that my wife makes her mad money by collecting them for recycling (as well as other metals) and makes a few hundred a month -- tax free.

http://www.nature.com/ncomms/journal/v1 ... s1062.html

Evidently by treatment, they've managed to make aluminum alloy have steel like properties now -- this involves further work with age hardening and nanoscale crystal structures.

Doug
Funny you should put up that Nature paper.
I'm doing ion implantation work on Al @ the moment and I'm at around 12GPa hardness not 1GPa as in the Nature article

cannot divulge which ions, I will put up paper when I'm finished

We don't want to get anyone in trouble with their boss, (or lawyers) fer sure.

I can think of a few implants that make Al really hard...as deep as they went, and with the gettable depth/density profiles (but I'm no expert on that, all book reading so far, and the current art is likely better than I know).

What was interesting to me here was it was a standard alloy (7075!), treated specially to get a particular hierarchy of nano-structures in bulk (their words) -- looks like they are playing with dislocation structures, controlling slip and geometry, but said it was ductile too. Which is the kind of thing that might turn myself or Jerry (and a lot of others) on as an engineering material.

There are a ton of high value applications also for something strong in bulk and hard near the surface, that come to mind. Particularly if the "hard" is also "slippery".

It could be the approaches dovetail so both would work together? Get the best of both idea-sets? That would be the sort of thing I want this board to be all about, actually.