Handbook of Energy Storage for Transmission or ... - W2agz.com

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Maxwell Technologies began development efforts on electrochemical capacitors in the
early 1990’s after receiving a DOE contract to develop an advanced electric vehicle loadleveling
capacitor. Development was initially confined to type I products, then switched
to type II products in an effort to obtain higher energy density. Maxwell has developed
8-kJ cells using an accordion-fold design with carbon cloth electrodes and organic
electrolyte. They presently are developing a spiral-wound design using particulate
carbon.
At about the same time in Japan, the Okamura Laboratory begin working on a type II
design that used active power electronics for controlling and leveling multi-cell modules.
Several patents have been obtained in Japan and the US. Results of this work were first
published in English at the electric vehicle conference, EVS-13 in 1996, and some time
later at the International Seminar on Double Layer Capacitors held annually in south
Florida. The design technique, under the trademark ECaSS, has led to relatively high
reported specific energies in the 4-6 Wh/kg range. Several Japanese manufactures
including Shizuki Electric, Nissan Diesel and Power Systems Ltd, offer either capacitor
modules or products that use this design.
The first reported activity on type III capacitors was from Russia. The Elit Company
made asymmetric capacitors based on nickel oxyhydroxide and carbon electrodes with
potassium hydroxide electrolyte. These devices were used to power wheel chairs and
subsequently, children’s toy cars. This company later concentrated on, and has widely
commercialized a type I carbon/carbon electrochemical capacitor.
The Russian company ECOND presented a paper in the US in late 1993 that described
type I electrochemical capacitors much larger in size than any device then available or
under development in the US. Their capacitors were described as the power source for
starting diesel internal combustion engines of sizes up to 3000 horsepower, including
locomotive engines. The 1993 paper was certainly an eye-opener for some US
researchers involved in the development of 1.8 MJ electric vehicle load-leveling
capacitors. As with ELIT, this work was a giant step ahead of research that had been
reported in the US and provided encouragement to many capacitor developers.
Type III development activities continued in Russia and were greatly expanded by the
Joint Stock Company ESMA, a Moscow-based developer and manufacturer. This
company reported using type III capacitors to power electric buses and electric trucks in
1997, with capacitors being the sole energy source in the vehicles. These 30 MJ
capacitor storage systems far surpassed the size of any previously reported system.
ELTON, the ESMA parent company, has patents that cover the asymmetric capacitor
concept, i.e. type III and IV designs.
There is considerable development activity today on type IV capacitor products. These
include use of lithium battery intercalation electrodes in combination with activated
carbon double-layer charge storage electrodes. Development along this line has
progressed rapidly due to the exploitation of material advances made on Li-ion battery
technology.
Electrochemical Capacitors 23