Storing solar energy in chemical form (credit: Grossman/Kolpak)

MIT researchers have developed a new application of carbon nanotubes that shows promise as an innovative approach to storing solar energy for use whenever it’s needed.

Storing the sun’s heat in chemical form — rather than first converting it to electricity or storing the heat itself in a heavily insulated container — has significant advantages: in principle, the chemical material can be stored for long periods of time without losing any of its stored energy.

The researchers created carbon nanotubes in combination with a compound called azobenzene. The resulting molecules, produced using nanoscale templates to shape and constrain their physical structure, and the concept that can be applied to many new materials.

This material is vastly more efficient at storing energy in a given amount of space — about 10,000 times higher in volumetric energy density, making its energy density comparable to lithium-ion batteries, the researchers said.

Ref.: Alexie M. Kolpak, Jeffrey C. Grossman, Azobenzene-Functionalized Carbon Nanotubes As High-Energy Density Solar Thermal Fuels, Nano Letters, 2011; 110705085331088 [DOI: 10.1021/nl201357n]