Could Small Springs Beat Batteries?
Friday, September 25 2009
Any system that requires conversion from mechanical energy to electrical and back again, using a generator and then a motor, will lose some of its energy in the process through friction and other processes that produce waste heat. In addition to the direct energy losses, about half the weight of electromechanical systems is in the motor-generator used for the conversion — something that wouldn't be needed in a purely mechanical system.
The nanotube molecules have a strong tendency to stick to each other, lending themselves to being made into longer fibers that can make effective springs. Livermore says that this quality means that ultimately it may be possible to "make something that looks like a carbon nanotube and is as long as you want it to be."
Carbon nanotube springs are also relatively unaffected by differences in temperature and other environmental factors, whereas batteries need to be optimized for a particular set of conditions, usually to operate at normal room temperature.
Livermore says that to create devices that come close to achieving the theoretically possible high energy density of the material will require plenty of additional basic research, followed by engineering work. The initial lab tests used fibers of carbon nanotubes joined in parallel, but creating a practical energy storage device will require assembling nanotubes into longer and likely thicker fibers without losing their key advantages.