Carbon nanotubes used to create solar thermal “fuel”

Ars Technica : Photovoltaics and solar thermal energy plants are the two current approaches to harvesting energy from sunlight. Now, researchers have created a potential third alternative they call solar thermal fuel. In normal fuels, molecular bonds are broken to release energy. In the new fuel, the molecular bonds rearrange to absorb and release energy cyclically in response to exposure to UV radiation. The researchers used azobenzene which has two different physical structures . Normally the transition between the two structures is not efficient, but a computer model predicted a 30% improvement if the molecule was bonded to carbon nanotubes. When the researchers created such a bond, they found the actual increase in efficiency was 200%. The resulting material had an energy storage efficiency of 14% and an energy density of 44 Watt-hours/kg, on par with lead-acid batteries. Whether the material can be commercialized is not clear yet, but it could open a new avenue for using solar energy.