Talk-Polywell.org

EEStor has some kind of deal cooking with Lockheed Martin, according to Technology Review. There's been lots of "too good to be true" skepticism about these guys. Landing a major contract may mean they've got something. Worth keeping an eye on.

Lockheed has not seen a working prototype but said that qualification testing and mass production of EEStor's system is planned for late 2008.

EEStor always claims they'll be in production about a year from whatever date the press release is posted. This game has been going on for a while now.

The big criticism of their patent is that barium titanate is not a linear dielectric, and it also has terrible performance in cold temperatures.

scareduck wrote:EEStor always claims they'll be in production about a year from whatever date the press release is posted. This game has been going on for a while now.

True; I've been watching these guys for years, and am firmly in the I'll-believe-it-when-I-see-it camp by now.

scareduck wrote:The big criticism of their patent is that barium titanate is not a linear dielectric, and it also has terrible performance in cold temperatures.

Well, to be fair, if they could get the performance they claim even under narrow temperature conditions, I suspect it would have a lot of novel uses. (Just off the top of my head, replacing batteries in home wind/solar power systems for example.)

JoeStrout wrote:

scareduck wrote:EEStor always claims they'll be in production about a year from whatever date the press release is posted. This game has been going on for a while now.

True; I've been watching these guys for years, and am firmly in the I'll-believe-it-when-I-see-it camp by now.

scareduck wrote:The big criticism of their patent is that barium titanate is not a linear dielectric, and it also has terrible performance in cold temperatures.

Well, to be fair, if they could get the performance they claim even under narrow temperature conditions, I suspect it would have a lot of novel uses. (Just off the top of my head, replacing batteries in home wind/solar power systems for example.)

Or in hybrid cars. I'm sure that with such a superior power store a proper insulation/heating system to keep the supercaps at optimum temp will be worth it.

A question here:

I've been reading a lot about supercapacitors and it seems like there's two approaches to radically increase storage.

One is to increase the surface area and another is to use better dielectrics.

Now most supercaps use the former, by using various forms of carbon. But this limits the maximum voltage as voltages higher than about 2 volts will damage the carbon.

EEStor seems to be on the dielectric route.

Why not build a battery that uses both the superior dielectric and the superior charged surface?

Why not try to construct nanoscale high surface area capacitors that can withstand 200V or more?

Just a regular super cap capable of reaching voltages that regular capacitors can go to would totally displace gasoline. (A 5000F supercap at 200Volts would store 100MJ of energy.)

I'm sure I'm not the only person that these questions have occured to, so I'm looking for the "why not" specifically.

Physical break down and arcing is the most likely reason. Once you get over 1 MV/m most materials will arc through. Increasing the surface area decreases the thickness for the same volume, so the electric field increases beyond the strength of the dielectric.

The ionization potential of a molecule is the theoretical limit. If you can find a molecule which requires 10eV to ionize and it is 2 Angstroms thick then you've got a 5MV/m material. That's still only 10V. To get to 200 Volts you would need 20 times the thickness. Since capacitance is inversely proportional the the distance between the plates, you get more capacity at lower voltage and thinner material than you get at higher voltage and thicker material.

The net end result is that you are better off with more capacitance at lower voltage in terms of energy per unit volume.

drmike wrote:Physical break down and arcing is the most likely reason. Once you get over 1 MV/m most materials will arc through. Increasing the surface area decreases the thickness for the same volume, so the electric field increases beyond the strength of the dielectric.

The ionization potential of a molecule is the theoretical limit. If you can find a molecule which requires 10eV to ionize and it is 2 Angstroms thick then you've got a 5MV/m material. That's still only 10V. To get to 200 Volts you would need 20 times the thickness. Since capacitance is inversely proportional the the distance between the plates, you get more capacity at lower voltage and thinner material than you get at higher voltage and thicker material.

The net end result is that you are better off with more capacitance at lower voltage in terms of energy per unit volume.

So supercaps reach their extraordinarily high capacitiances by not just increasing surface area, but also by bringing the positive and negative plates closer together?

OneWayTraffic wrote:Why not build a battery that uses both the superior dielectric and the superior charged surface?

Because a battery does not use a dielectric. A battery stores energy in ionic bonds.

Why not try to construct nanoscale high surface area capacitors that can withstand 200V or more?

This is what EEStor is trying to do. Assuming you could get the physics to work (which, judging by what's publicly available about EEStor's technology, is largely a matter of getting the purity of the barium titanate to a sufficient number of nines), the big problem with such a device will be the fact that they have to have much more exotic power management than conventional chemical batteries because they must operate over a very wide range of voltages.

I'm sure I'm not the only person that these questions have occured to, so I'm looking for the "why not" specifically.

The "why not" is that barium titanate has been heavily researched before, and it is a linear electrolyte which tends to arc at fairly low voltages, IIRC.

scareduck wrote:

OneWayTraffic wrote:Why not build a battery that uses both the superior dielectric and the superior charged surface?

Because a battery does not use a dielectric. A battery stores energy in ionic bonds.
.

Slip of the keyboard.

I guess that those science fiction stories of 'energy cells' storing enough energy for a Single Stage to Orbit or more will remain just that: Sci Fi.

Does anyone know of any theory which might allow such storage to rival gasoline? I'm guessing not, as such things tend to rely on the energy contained within the electrostatic force, and burning things is pretty hard to beat by any reversible means.

This is what EEStor is trying to do. Assuming you could get the physics to work (which, judging by what's publicly available about EEStor's technology, is largely a matter of getting the purity of the barium titanate to a sufficient number of nines), the big problem with such a device will be the fact that they have to have much more exotic power management than conventional chemical batteries because they must operate over a very wide range of voltages.

Actually given modern electronics a 4:1 range of voltage is not too tough.

A 2:1 range is easy. So let us run the numbers. Energy varies as V^2.

delta energy in % = (1 - (remaining voltage/initial voltage)^2) *100

all numbers when not exact rounded down.

2:1 - 75%
3:1 - 88%
4:1 - 93%

For lead acid batteries - to insure long life - discharge below 50% of stored energy not recommended. Lion is better. You still don't want to do 100% discharge.

OneWayTraffic wrote:
So supercaps reach their extraordinarily high capacitiances by not just increasing surface area, but also by bringing the positive and negative plates closer together?

Correct. At some point you rip the electrons out of their orbits though - ionization. When the potential across an atom is higher than the potential from the nucleus, the electron can leave. So as you get the plates closer, you have to drop the voltage.

That's why you see all the cores of processors going down in voltage. To go faster with smaller transistors, you have to reduce the voltage so the devices don't arc.