Ceramic cap hoarding

my math was basically 2E=CV^2

My thinking is maximum energy density per unit volume of dielectric should be constant for all different configurations.

CV^2 constant (for fixed volume) is my claim above, It's good to see that the theory of operation brings out the same result :)

Best regards, Piotr

What do you mean "too"? The above N *is* the number of layers.

Rick C.

I think that higher voltage electrolytics have a better ratio of dielectric thickness to foil thickness than low voltage ones. There's a limit to how thin the foil can be, so the foil, wasted volume, tends to dominate the LV parts.

I'd guess that the max available energy storage per volume of actual dielectric is pretty much constant. I wonder what material is best?

I'd guess diamond.

Well, vacuum* of course. But it gets much, much worse as soon as you have any kind of condensed matter nearby to rip electrons from. More practical as transmission line than capacitor.

Tim

What is the field strength that rips conductors out of the "foam"? I know this happens in the huge gravitational gradient near the event horizon of a black hole giving rise to Hawking radiation.

Rick C.

Pair production is where vacuum becomes nonlinear. In quantum terms, you need at least two photons of 511keV each, but the cross section for that is quite small (why I don't know, probably something about phase and momentum having to line up perfectly -- they're quite small photons after all). The cross section doesn't go suddenly to zero for smaller photons, but it does drop precipitously. But it goes back up in extremely intense field strengths, a semiclassical mixing effect if you will.

AFAIK, it's a rate, not a simple threshold -- so the effect would be losses and scattering, getting worse as field strength goes up.

Everything is nonlinear, it's just a matter of degree; vacuum just happens to have the widest linear range. :)

Tim

Maybe something with strongly polar molecules stores spring-y energy better. So, a pure crystal of something strongly polar, plates properly aligned to the right crystal axis, and something with high breakdown voltage.

A dielectric constant of a couple thousand sure helps here. Diamond is around 6.

Something like 1e8 v/cm rips metals apart. That limits how much microwave power you can pump into a superconductive cavity.

For energy storage don't you want something bordering on chemistry, How do super caps stack up energy density (per volume) wise? Then Al electros?

George H.

Helps, if it can hold that much charge. X7R falls over at orders of magnitude less than diamond breakdown (2000 MV/m).

(Compare:

Looks like ceramics fail not much beyond there, depending on type. C0G dielectric constant is around 40 I guess, so diamond being 6 is a (2000/24) / (40/6) improvement, quite reasonable.

Probably materials with high binding energy and bandgap are the best. You're dealing with stripping electrons from the valence band, or something like that. There's going to be one material that's best (probably diamond, or BN or such), and nothing that can be any better than that, period, basically because the mass of the electron and nuclei are what they are.

That's why I noted pure vacuum can go much higher... a shame that it's rather more difficult to arrange as a static energy storage medium!

Tim

Ideally, you'd have something that stores energy in atomic bonds, not just fields around them (otherwise known as... a battery). But bonds are quantum, so you get a constant voltage, give or take statistical mechanics (hence exponentials everywhere).

Any more and you have to go smaller (nuclear).

Any less, and, say, you can afford to store energy in the field around the atoms, in which case you get a capacitor. Simply by the fact that a capacitor _cannot_ break bonds -- because if it did, it would break down, or it would be a battery -- a capacitor cannot have as much energy density as a battery. :)

Tim