Researchers at the MIT Laboratory for Electromagnetic and Electric Systems (LEES) are working on an ultracapacitor that uses vertically aligned, single-wall carbon nanotubes as the electrode in an ultracapacitor. They claim that their ultracapacitor "holds out the promise of the first technologically significant and economically viable alternative to conventional batteries in more than 200 years."
However, despite their inherent advantages -- a 10-year-plus lifetime, indifference to temperature change, high immunity to shock and vibration and high charging and discharging efficiency -- physical constraints on electrode surface area and spacing have limited ultracapacitors to an energy storage capacity around 25 times less than a similarly sized lithium-ion battery. ....
Storage capacity in an ultracapacitor is proportional to the surface area of the electrodes. Today's ultracapacitors use electrodes made of activated carbon, which is extremely porous and therefore has a very large surface area. However, the pores in the carbon are irregular in size and shape, which reduces efficiency. The nanotubes replace the activated carbon that is typically used as the electrode in ultracapacitors. The vertically aligned nanotubes in the LEES ultracapacitor are one thirty-thousandth the diameter of a human hair and 100,000 times as long as they are wide, only several atomic diameters in width, and have a regular shape. The result is a significantly more effective surface area, which equates to significantly increased storage capacity. ....
Joel E. Schindall, associate director of the LEES said "This configuration has the potential to maintain and even improve the high performance characteristics of ultracapacitors while providing energy storage densities comparable to batteries. Nanotube-enhanced ultracapacitors would combine the long life and high power characteristics of a commercial ultracapacitor with the higher energy storage density normally available only from a chemical battery." ....
Capacitors store energy as an electrical field, making them more efficient than standard batteries, which get their energy from chemical reactions. Ultracapacitors are capacitor-based storage cells that provide quick, massive bursts of instant energy. They are sometimes used in fuel-cell vehicles to provide an extra burst for accelerating into traffic and climbing hills.
I think their claims on relative size may be somewhat exagerated, but otherwise it sounds like a possibly important contribution to ultracapacitor technology. I wonder how this technology compares to the EEStor technology.
Resource: Researchers fired up over new battery, MIT news office, February 8, 2006
Technorati tags: ultracapacitors, energy storage, energy, technology
Posted by: concert artist | May 29, 2006 at 02:52 AM