In many parts of the world, the rock strata are like a layer- cake. In many such cases, there are porous, water- saturated strata separated by impermeable layers.
The water-saturated, permeable layers are, in general, reasonably conductive by virtue of dissolved salts.
What we have, therefore, is effectively a giant capacitor - two layers of conductor, separated by an insulator. Depending on the area of the structure and the thickness of the non-conductive rock, this capacitance is likely to be on the order of many zergoFarads.
So, in these cases, simply sink a couple of mine shafts. The first shaft runs all the way down to the lower conductive stratum. A few tons of molten copper is poured in, filling the very bottom of this shaft; a big insulated cable then connects this copper to the surface. The second shaft only runs down as far as the upper conductive layer, and is likewise connected to a big cable.
Gadulka! You now have an immense system for capacitative storage of power from fluctuating sources such as wind or solar.-- MaxwellBuchanan, Jul 24 2015 Gadulka https://en.wikipedia.org/wiki/Gadulka [normzone, Jul 24 2015] The Zerg Overmind does not approve of your discovery of their zergofarad unit of measurement.-- RayfordSteele, Jul 24 2015 Probably a small scale mockup would be good first. That copper will be costly and a pain in the butt to retrieve. I was going to suggest a sandbox but the prospect of a giant sandbox capacitor would provoke too much glee from certain readers. Better: a large bucket with a mockup of relevant strata. This bucket is sited far away from kiddies of any sort.-- bungston, Jul 24 2015 //The Zerg Overmind//
Who knew?-- MaxwellBuchanan, Jul 24 2015 The other one.-- MaxwellBuchanan, Jul 24 2015 An ideal candidate for lightning storage Shirley? Can any interesting ions be introduced to make the chemistry a bit more fun?-- bs0u0155, Jul 24 2015 Thankyou for the link, [normz]. A gadulka is, of course, a type of voila.-- MaxwellBuchanan, Jul 26 2015 (link) surely the Earth's capacitance is in microfarads and not nanofarads? 600x10^-6? Important facts and all that....-- Ling, Jul 27 2015 Great premise. It should be easy to test this premise in a small prototype setup. Just need some rocks & water...-- sophocles, Jul 28 2015 Probably some clay too, right?-- bungston, Jul 28 2015 // surely the Earth's capacitance is in microfarads//
It depends on the area of the strata, and the distance between conductive layers.
Suppose we can find strata which extend over a 10x10km area (fairly easy, one would think), and with a 10m insulating stratum between the conductors. The capacitance is then given by:
C = p.q.A/d
where p is the permittivity of the insulator (we'll call it 1), q is about 10^-11, and A and d are the area and separation, in m2 and m.
So
C = 1 x 10^-11 x 10^8 /10 = 10^-4, or about 100µF.
Assuming decent insulating properties for the middle layer, we ought to be able to run this up to at least 10MV, which equates to ahout 10^10J of stored energy. Which is not unsignficant.-- MaxwellBuchanan, Jul 28 2015 // surely the Earth's capacitance is in microfarads// I was referring to the "Earth as a spherical capacitor" link, which says (6.3x10^6)/(9x10^9) = approx 700x10^-9 for some reason.-- Ling, Jul 28 2015 If such a region exists, maybe it has already accumulated some charge. It stands to reason that it would. Maybe you can just plug in and go. Lots of other useful things have accumulated under the earth and are waiting for us to use them.-- bungston, Jul 28 2015 //I was referring to the "Earth as a spherical capacitor" link,// I think that link assumes that one conductor is the core, and the other is at the surface - much too far apart.-- MaxwellBuchanan, Jul 28 2015 I would think there would be some shorting out between the layers due to salt water and the like.-- RayfordSteele, Jul 28 2015 Suppose deep layers do sometimes accumulate charge. Drilling operations would enounter this charge. There would be sparks, current and the like. I wonder if this happens?-- bungston, Jul 29 2015 Is it possible to overcharge it, reach breakdown voltage, and blow up a continent?-- Voice, Jul 29 2015 Theoretically possible. We could test it on Wales and see how it goes.-- MaxwellBuchanan, Jul 29 2015 random, halfbakery