In an article released today, MIT researchers have found that carbon nanotubes, formed into tiny springs have the potential to store as much energy pound for pound as modern lithium ion batteries. We have summarized the article below but encourage you to read the full text (see link below).

"Theoretical analysis shows the carbon nanotube springs could ultimately have an energy density — a measure of the amount of energy that can be stored in a given weight of material — more than 1,000 times that of steel springs, and comparable to that of the best lithium-ion batteries."

For some applications, springs can have advantages over other ways of storing energy, Livermore explains. Unlike batteries, for example, springs can deliver the stored energy effectively either in a rapid, intense burst, or slowly and steadily over a long period — as exemplified by the difference between the spring in a mousetrap or in a windup clock. Also, unlike batteries, stored energy in springs normally doesn't slowly leak away over time; a mousetrap can remain poised to snap for years without dissipating any of its energy.

Rod Ruoff, professor of mechanical engineering at the University of Texas, adds that while the theoretical energy density of such systems is high, present ways of making carbon nanotubes are limited in their ability to produce highly concentrated bundles, and so "It appears to me that the 'low hanging fruit' here is to find important applications where the energy density on per weight basis outweighs the energy density on a per volume basis." But, he adds, if Livermore and her team are able to produce denser bundles of carbon nanotubes, "then there are exciting possibilities for mechanical energy storage" with such systems.

Two papers describing Livermore and her team's findings on energy storage in carbon nanotube springs have just been published. A paper describing a theoretical analysis of the springs' potential, co-authored by Livermore, graduate student Frances Hill and Timothy Havel SM ’07, appeared in June in the journal Nanotechnology. Another paper, by Livermore, Hill, Havel and A. John Hart SM ’02, PhD ’06, now a professor at the University of Michigan, describing laboratory tests that demonstrate that nanotubes really can exceed the energy storage potential of steel, appears in the September issue of the Journal of Micromechanics and Microengineering.

Full Article from MIT "Small Springs Could Provide Big Power"