ZENN Motors vehicle at the EDTA Conference last November

More details have emerged about EEStor's ambitious ultracapacitor electrochemical battery replacement technology. EEStor sees applications for their Electrical Energy Storage Units (EESU) in everything from hybrid-electric and pure-electric vehicles, to laptop computers, to utility-scale electricity storage. Based on barium-titanate powders, the units are supposed to dramatically outperform the best lithium-ion batteries on the market in terms of energy density, price, charge time, and safety. And since capacitors don't require chemical processes to store power, EEStor said in its patent, the materials the company uses are safer and more environmentally friendly.

Ultracapacitors store energy in an electrical field between two closely spaced conductors, or plates, upon which an electric charge builds when voltage is applied. Unlike traditional electrochemical batteries, ultracapacitors can completely store and release a charge quickly and indefinitely over many cycles. Where they don't compete though is energy storage; here lithium-ion batteries can store 25 times more specific energy - the amount of energy in a given unit of mass.

Most research into increasing the charge that can be stored by the plates has focused on ways to increase the surface area. Last year, the Massachusetts Institute of Technology said it was working on hugely increasing the plate surface area by researching plates made of microscopic nanotubes.

Up until now, ultracapacitors, have been used in conjunction with traditional batteries to more fully harness the regenerative energy created in sudden bursts by braking activity with their ability to release quick jolts of electricity. Their characteristics are ideal for maximising efficiency in stop-start city driving. Ultracapacitor manufacturer Maxwell Technologies has been able to capitalise on this strategy in their 125-volt BoostCap ultracapacitor module.

EEStor's EESU, a ceramic ultracapacitor with a barium-titanate dielectric, or insulator, is claimed to break free of the traditional limitations of small energy storage found in other ultracapacitors. Apparently they have achieved an exceptionally high specific energy and permittivity - the ability of an substance to store electrical energy in an electric field. Normally an ultracapacitor has a permittivity rating of 20 to 30, compared to the claimed EESU rating of 18,500 plus. As you can imagine, such claims have raised questions amongst experts who hold concerns that such ceramic materials can survive and function properly in vehicle applications.

In an interview with Technology Review, Jim Miller, vice president of advanced transportation technologies at Maxwell Technologies said, "We're skeptical, number one, because of leakage. Meaning, if you leave it parked overnight it will discharge, and you'll have to charge it back up in the morning."

In the same article, Andrew Burke, an expert on energy systems for transportation at University of California at Davis said, "I have no doubt you can develop that kind of [ceramic] material, and the mechanism that gives you the energy storage is clear, but the first question is whether it's truly applicable to vehicle applications."

ZENN Motor Company is reported to be getting first access to EEStor's EESU technology for use in their Low Speed Vehicles.

Maxwell Technologies meanwhile has just announced that they are forging ahead with their technology and have received a purchase order for 100,000 square meters / 1,076,400 square feet of proprietary ultracapacitor electrode material from a licensee, Shanghai Sanjiu Electric Equipment Co. This will allow Sanjiu Electric to launch a new ultracapacitor product line based on Maxwell's Cell Architecture for transportation, utility and industrial markets in mainland China.

Mr. Hong Yuan Shuai, Chairman and CEO of Sanjiu Electric parent company, the Ruihua Group, said that Sanjiu Electric has already produced and delivered a variety of prototype electric and hybrid buses, trucks and other vehicles powered by drive systems combining batteries and Maxwell BoostCap ultracapacitors for energy storage and regenerative braking.

Analysis: The EESU prospects are exciting, but I think Maxwell's use of ultracapacitors in regenerative breaking applications is probably a better choice for vehicular applications at this point. Where EEStor's products could open up a sizeable lead over the opposition though is in the area of military, direct-energy "ray-gun" weapons. Personally, I'll just stick with better fuel economy in stop-start traffic.

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[Source: Technology Review]

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