Reply #13: Russian physicist takes on EEStor's bold claims:

[wtmusic]

Anatoly Moskalev wrote on January 20th, 2007 at 2:05 pm

About EEStore supercapacitor hype :

1. The company made claims about dielectric powder parameters - that is it. Claims themselves are likely correct. So they have powder with:

Eps = 18500, Eth = 3 * 10 ^ 6 V / sm, Density = ~ 6 g / sm^3 ( Eth - practical electric field intensity threshold )

For 12 um thickness of dielectric we get Uth = ~3500 V - top practical voltage. From a capacitor formula you could get

C = ~0.2 F / kg resulting to energy density ~1.15 MJ / kg = ~320 Wh / kg

For comparison Tesla Motors battery pack has 5 2 kWh / 450 kg = ~110 Wh / kg

Capacitors formulas from school text books appears well known so after powder parameters verified EEStore CHEMISTS feel safe to make bold claims.

2. But good physicist like me knows very well that capacitors physics under extreme conditions is not textbook straightforward. The dielectric constant involved will stay at indicated value until approximately 30000 V / sm electric field strength. This value is pretty high so measurements unlikely exceed this so they give high Eps value OK.

But to get claimed energy density you need approximately 100 times higher field strength. Getting such field strenght is extremely unlikely in the Eps measurements. But the reality is that exactly in this field strenght region electrical induction gets saturation because it reaches the interatomic field strength. This is well know effect to physicysts but not very widely known phenomenon to general public. Resulted effect on the energy could be described as if dielectric constant gets reduced in the formula. My estimations demonstrates that actual energy density would be 25 - 50 times less than a claim.

Resulted EEStore capacitor would approximately match currently available ultracapacitors by energy density per unit of mass making ~5 times better energy density per unit of volume. As such it would be marginal improvement over existing ultracapacitors technology. It surely would be a order of magnitude improvement for ceramic capacitors so it would have some use. But it would be nothing as bold as EEStore claims.

In 1 - 2 years from now we will see what would be the outcome of EEStore activity. Judgement day for EEStore would come when somebody would build a capacitor and try to store expected energy into it. It would be discovered that above
~100 V voltage would grow with charge much faster than expected and finally instead of ~15 kWh it would be ~0.3 kWh at the highest possible voltage. But powder alone would match all the promises. Who knows - they might even think it is a big discovery of new phenomenon. So they would explain the failure by claiming they run into truly unpredictable effect unknown to science. Irony is that 1947 year physics knows it and today it is forgotten.

http://www.teslamotors.com/blog1/index.php?p=46&js_enabled=1