I’m sure this has been considered and written about before, but it really was my idea. Send the Nobel to…
Seriously, the ocean is an alkaline solution so it should work in theory right? Which metals would work best? How big and/or many would they have to be to run a flashlight or a city? In large scales, would this adversely affect the ocean chemistry?
Probably—but would you get more energy out of the reaction than it took to create the big giant electrodes in the first place? I wouldn’t think so.
IIRC any two dissimilar metals will do, but they cannot be corroded. The corrosion of the metal is what creates the current unless my mind is completly failing me.
Could be, it’s been 10 years since I had chemistry, I’m sure someone who had it more recently can add more.
You’re thinking of electroplating, I think.
Yes, you can. Trouble is, the chemical energy in a battery is derived from consumption of the metal electrodes, not from the electrolyte (the liquid) which can remain entirely unchanged. So you wouldn’t be getting any power from the sea - just extracting the energy you used to refine the metals in the first place.
You may have seen the gimmick of digital clocks that are powered by a lemon or a potato and wondered why you couldn’t run your house using a a few bushels of lemons. The same applies - no energy is being extracted from the lemon, only from oxidation of the less noble electrode.
An example - iron in nature is normally found in an oxidised state - e.g. as ferous hydroxide Fe(OH)[sub]2[/sub]. We go to a lot of trouble to reduce such ores to metallic iron in a blast furnace, using something like half a tonne of coke to produce each tonne of iron. (It used to be a tonne per tonne, but we’ve gotten better at it.)
You can get that energy back in many ways by re-oxidising the iron. If you devide iron finely enough you can burn it directly and get the energy as heat. Or you may wish to make an iron battery - use a lump of iron as an electrode and a noble metal (e.g. platimum) or chunk of graphite as a second, inert electrode. Use the sea, or lemon juice, or mashed potatoes as your electrolyte.
The wet iron will happily corrode according to the reaction:
Fe -> Fe[sup]2+[/sup] + 2e. The Fe[sup]2+[/sup] goes into the electrolyte, while the electrons are left on the metal.
On the platinum electrode, water and dissolved oxygen react as below:
H[sub]2[/sub]O + [sup]1[/sup]/[sub]2[/sub]O[sub]2[/sub] + 2e -> 2OH[sup]-[/sup]. The OH[sup]-[/sup] goes into the electrolyte, and an electron deficit is left on the metal.
Hook the two electrodes up to your digital clock and electrons run from one to the other, new electrons being generated at the iron electrode as it dissolves and consumed at the platinum electrode as oxygen is reduced.
Keep in mind that Fe[sup]2+[/sup] and OH[sup]-[/sup] are entering the liquid. If they concentrate up enough, they will combine to form Fe(OH)[sub]2[/sub] and you’re back with your ferrous hydroxide ore again.
Actually this would make a lousy battery - it doesn’t give a constant voltage since the iron electrode forms surface crud, and it can’t deliver high currents. But you could run a digital clock using it.
Oil rigs often have a ‘sacrificial anode’ attached - a big chunk of something that corrodes more readily than steel - the effect is the same as that used in salt water batteries and electroplating processes.