EEStor's "Ultracapacitors": Quick-Charging Battery Replacements
The AP has a decent high-level overview of the "ultracapacitor" technology from EEStor, an as-yet-untested, quick-charging capacitor that its inventors claim will replace batteries entirely.
EEStor's secret ingredient is a material sandwiched between thousands of wafer-thin metal sheets, like a series of foil-and-paper gum wrappers stacked on top of each other. Charged particles stick to the metal sheets and move quickly across EEStor's proprietary material.Extraordinary claims require extraordinary evidence, reminded Carl Sagan. Until EEStor's products are in the hands of independent testers, we can only cross our fingers....
Previous attempts to improve ultracapacitors have focused on improving the metal sheets by increasing the surface area where charges can attach.
EEStor is instead creating better nonconductive material for use between the metal sheets, using a chemical compound called barium titanate. The question is whether the company can mass-produce it.
Although much of the initial talk about the ultracapacitor technology refers to its use in electric cars, smaller versions could also be used to power quick-charging gadgets like phones and MP3 players.
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It's pretty clear that batteries are not the best technology for certain applications (specifically automotive where there are many rapid charge/discharge cycles). I'm very excited about the ultra-capacitor as a replacement for conventional batteries - it just makes sense.
Who knows if EEstor will be able to pull it off, but I'm hoping that someone can.
Sorry, but any "Wafer Thin" comments automatically bring Monty Python quotes to my mind, not the best connotation for an emerging technology...
A quick charge, quick discharge cycle does make sense for Electric & Hybrid vehicles, but this technology sounds like its not ready for Prime Time; in January they were saying they'd be releasing the product this year, they're now saying the middle of next year. Also, the company's threatened to sue publications that even discuss their technology:
http://www.treehugger.com/files/2006/03/eestor_capacito_1.php
Threats like that don't sound like a company that's ready to start selling its product to the general public.
Freddie: You are certainly correct in taking all this with a hunk of salt. Not all tech companies are very good at dealing with the press, but being that aggressive is rarely a positive sign.
Below is a detailed discussion clearly demonstrating the invalidity of EEstor’s claims and targets.
EEstor does not report either a new material, or any data that indicates the ability to store more energy than known titanate dielectrics. EEstor calculates the amount of energy they expect their capacitor to store. A fundamental oversight results in an invalid calculation that is inaccurate by more than a factor of 100! The error is uncomplicated. Simply, energy does not equal ½ CV2 for a capacitor made from a nonlinear dielectric. For all high permittivity ceramics, the dielectric permittivity (K’) decreases markedly with increasing electric field E (dielectric saturation). Energy increases roughly linearly with voltage for these materials, as opposed to with the square of the voltage (ref 2).
Importantly, this is not a case wherein EEstor claims to have made some specific breakthrough regarding this issue. No such breakthrough is reported. There are no energy storage measurements, no permittivity versus field data, and no mention of eliminating or reducing dielectric saturation. Their patent and presentations indicate a complete lack of awareness (or lack of acknowledgment) of this issue. EEstor simply purports to make (or aspires to make) high K barium titanate based material, with a K of 18,000, and ultimately with an incredibly high breakdown strength of up to 300V/um. They then calculate the energy stored as ½ CV2 without comment on the use of this equation.
How large of an error does this cause? Calculated energy density is ½K’E2 when calculated total energy is ½CV2. For K = 18,000, and a field 100 V/um, this invalid calculation gives 800 J/cc. (½K’E2 = (0.5)(8.85×10-12 F/m)(18,000)(1×108 V/m) = 8×108 J/m3 = 800 J/cc). Eight references describing actual studies of energy storage in high permittivity ceramic dielectrics (including barium titanate and BST) are noted below. All of these studies indicate a maximum energy density ranging from about 2 to 12 J/cc, depending on the exact material and the maximum breakdown voltage (which is on the order of 100V/um in most cases). Notably, for the studies involving very high K materials, if the authors had simply calculated energy storage using ½ CV2, as EEstor does, it would have similarly resulted in reported values on the order of 100 times greater than the actual measured values!
Hence there is no basis for concluding EEstor has made any advance in the field, and clear evidence that the sole basis for their claim of unbelievably high energy storage is the simple, invalid calculation. Their aspiration (with no reported results) to triple the breakdown field to 300 V/um in combination with the invalid calculation adds an additional factor of 9, giving an absurd 7200 J/cc (along with all of the corresponding hype and speculation about a new miracle material).
Below are notes regarding the references noted above that clearly substantiate the analysis above (one report of personal measurements, the other seven directly from a Google search on energy storge in ceramic dielectrics). .
1. (My work, unpublished), 1987 – Report to Maxwell Corporation on energy storage potential in high permittivity ceramics. Measurements were made on thin films up to 100V / um on barium titanate and PLZT based dielectrics. K varied as ~ 1/E over much of the voltage range, resulting in an approximately linear increase in energy density with field. Maximum energy storage was 4 – 8 J/cc.
2. Love, Journal of the American Ceramic Society 1990 – Also observed a linear increase in energy with voltage for several classes of high permittivity (up to 12,000) thick film ceramics (barium titanate, PLZT, PMN). Reported up to 5 J/cc at 80 V/um.
3. Triani, et.al, (ANSTO and CSIRO – Australia, 2001 – J. Materials Science and Engineering. They reported 8 – 10 J/cc for PbSr titanate, and noted that the energy densities were similar to those of the best BaSr titanate materials for a given field, but the maximum fields of up to 100V/um (100KV/mm) were superior for the PST.
4. Kaufmann, et.,al, Penn State and Argonne, 1999. DOE Contract Report. They report sputtered BaSr titanate thin films with a K of 500 and a breakdown field of 100 V / um. K decreases to 120, and the energy storage is 11 J/cc. Also reported are data for hot pressed AFE/FE lead zirconate. These had a maximum K of 12,000, and a breakdown strength of 12 V/um, resulting in an energy storage of 3.2 J/cc.
5. Fletcher, et.al, 1996 Journal of Applied Physics D. They report a theoretical analysis based on Devonshire theory of ferroelectrics. Optimal energy density is predicted for materials with Curie Temperatures well below the operating temperatures. Applied to BaSr titanate, the model predicts an energy density of 8 J/cc at 100 V/um. The model was verified in actual materials.
6. Randolf, et. al, (Austria, 1996) – IEEE Annual Report - Studied dielectric energy storage for powders embedded in polymer matrices. They reported using a PbTitanate-PbZnNiobate material with K = 5000, and reported energy densities of 1 – 10 J/cc.
7. Lawless, et. al., Ceramphysics Inc. 1992 report a high permittivity ceramic (K = 8000) for which a maxium energy density of 6 J/cc was observed for samples with optimum breakdown strength.
8. Freim, Nanomaterials Research Corp NASA SBIR Proposal 1998, reports reduced dielectric saturation for nanocrystalline microstructures, and states that “Commercial coarse grain dielectric based ceramic capacitors are ineffective for use in high energy storage and delivery applications since the dielectric’s permittivity decreases sharply when the applied voltage is increased.” They target 5 – 10 J/cc for the proposed new improved materials.
If you aren’t familiar with dielectric saturation, or even if you are and you don’t think back to where ½ CV2 comes from – you miss it. And until you collect information and compare with the calculation, you have no clue it makes a factor of 100 difference in this case. People don’t even realize what EEstor is asserting. If they said, “we are going to use barium titanate based materials, which up until now how only been able to store 8 J/cc, but our barium titanate will store over 1000 J/cc – people would ask themselves how is that possible and what is the basis for that claim.
Then you would find out it’s not just a case of them not providing data or proof of their claims. They don’t even claim to have observed or measured a property indicating their barium titanate would be different. There is nothing left but the calculation. The sole origin for their high numbers is that they simply start with the K of high permittivity modified barium titanate (eg., K = 18,000 not a new achievement), and simply calculate energy = 1/2CV2. Anyone could have done that at any time for any high K material and gotten the same outrageous numbers.
So at that point, one should ask why people get a factor of 100 less when they actually measure it. The answer is well documented and obvious – dielectric saturation. So the only justification for using 1/2CV2 which gives a factor of 100 higher than known and understood measured values, would be if you made a measured observation that you have a fantastic new material that doesn’t saturate at all and stores 100 times the energy.
EEstor has never made any such claim or reported to have made any such obvservation. They just did the calculation. It’s just a mistake.
Thanks a lot. My knowledge of electromagnetism is inadequate. I should have asked myself what might be so revolutionary about EEStor's BT -- it didn't occur to me that it was just falsified physics! If capacitors somehow could be improved by three orders of magnitude, the problem of containment in the event of failure would be a limiting factot anyway.
Oh well, so much for capacitors as primary energy storage devices. As for power storage, even 8J/cc will improve the performance of hybrids.
Pollution: Moving from individual engines to central electricity generating plants would mean a net decrease in overall pollution. Even getting pollution out of our crowded cities would be a gain for public health.
United States, Japan and Russia currently lead the global ultracapacitor industry, with makers such as Maxwell Technologies Inc. and NEC Corp. occupying the majority of world market. To keep up with their foreign counterparts, mainland China makers are upgrading their production technologies and improving their product quality and R&D.
Dick Weir, founder and CEO of EEStor, told me a few weeks ago that there would be an announcement soon on permittivity of its barium titanite powder, considered a major benchmark that would trigger future payments to EEStor from ZENN, and I can only assume Kleiner Perkins as well.
http://eestor.biz/