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An RC Car That Runs On Soda Can Rings
polyp2000 writes with an Engadget excerpt to inspire instant toy envy: "A pair of Spanish engineers have recently unveiled the dAlH2Orean (see what they did there?), a R/C car that runs on aluminum. Dropping a few soda can tabs into a tank of sodium hydroxide produces enough hydrogen to power the little speedster for 40 minutes — at almost 20mph."
Here is a page on the projects website, which provides at least some explanation of how it works. Depending on how recently you took chemistry, you can get at least some of the general picture of it all. I have to imagine that they are hiding at least some side effect, like potential cost in extracting the Aluminium from aluminium hydroxide. I don't really know any of the specifics to say though.
http://www.dalh2orean.com/dAlH2Orean/Blog/Entradas/2011/4/15_Press_Conference.html
Hehe, this gives me the opportunity to pass along an old favorite to a much younger generation. We were doing this around the time that today's college students were being born. The best part is that you can still get all the pieces for this (unlike many stories 20 years before my youth, which centered around things like large gunpowder fireworks and F-size model rocket engines).
If you were to take a square of aluminum foil, fold it diagonally in half to create a crease, fill the crease with lye (available as Red Devil drain cleaner, among others), and the roll the whole thing up like a... uh... hand-rolled cigarette, and then to fill a (preferably small, 500 mL or less) bottle with a fair amount of water, into which you then place the Drano Reefer before quickly (but firmly) closing the cap and throwing it far, far away, you'd get the Drano Reefer bomb.
The hydrogen comes from the water; the NaOH is merely a catalyst preventing the 2Al + 6H2O -> 2Al(OH)3 + 3H2 reaction from getting stopped by aluminum oxide films, etc. Done right, the gas pressure will rupture the bottle, while the hydrogen produced will add to any flame. For obvious reasons, not recommended for glass bottles.
For an encore, take a metal can (soup, tomato, soda, whatever) and add roughly 1:1 ratio by volume of brake fluid and pool chlorinator (the "shock treatment" is preferred for its high free chlorine content). Adding fluid to chlorinator produces a delayed reaction; adding chlorinator to fluid produces a much faster reaction. Work with the proportions to produce the desired effect - if done properly, you can reliably produce any effect from smoke-only to rapid bonfire. Once you're comfortable with that, you can start working with paper or styrofoam cups to produce a self-immolating container.
You're too quick to dismiss this. As a chemist I'm able to appreciate the simplicity and energy density of aluminum metal. The problem with this and other powerful reducing agents (fuels) is that they are dangerously flammable under the wrong conditions. Nevermind the energy demands associated with producing it - the key is really to heat the aluminium oxide/fluoride ore bauxite up and get it good and melting in a big iron container which serves as the cathode for the electrochemical cell. The anode of choice, at least my best guess is good old carbon or graphite. Yes, it takes a lot of current to reduce the aluminum, but that's the freaking point. It's an energy storage medium. But anyhow, if you have a ready source of thermal energy and/or electricity, like say a nuclear reactor, this is moot. Aluminum is hella lot better to cart around than hydrogen gas ( very poor energy density ).
The idea of reducing/oxidizing a metal for energy is the principle for many existing battery designs, so the idea isn't new. Many of the problems are already apparent in other implementations, like the infamous "exploding" (I doubt they exploded, but they surely burnt hot and bright) lithium batteries.
Indeed, lithium (metal) and aluminum are powerful, energy-dense fuels. Lithium is so reactive (and yet the least among group I metals) that it reacts spontaneously with oxygen in the air while its oxide dissolves in whatever atmospheric moisture it can suck up. Aluminum is probably nearly as electro-positive (I'm not checking a periodic table) and sports three electrons' worth of reducing power relative to lithium's one donor electron. Its self-passivization just might make it the right tool for a bunch of cool applications where lithium and other alkalis are too reactive, too. Unfortunately its a solid and not readily mechanically metered like gasoline so it may be some time before we find it as a direct source of mechanical power in our automobiles, but you never know.
The space shuttle used aluminum fuel.
http://www.nasa.gov/returntoflight/system/system_SRB.html
I'd go on a Vegan diet but the delivery time from Vega is too long. --brownkitty