Carbon nanotubes are the glamor boys of material science. They are stronger than steel, conduct electricity better than metals and are incredibly lightweight.
The question has been what to do with them.
MIT associate professor Jeffrey Grossman, in conjunction with grad student Alexie Kolpak, has come up with a way to store solar energy with nanotubes. It is in the embryonic, experimental stage, but if further developments can be made, we could see heat batteries in the future that absorb sunlight and later, at their leisure, release heat. The heat, of course, could then be used to warm water, heat buildings, or generate electricity via thermoelectric device. Heat can also be used to run air conditioners.
The molecule in question combines carbon nanotubes -- which are tiny tubes constructed of carbon atoms -- with another material called azobenzene. When exposed to sunlight, the molecule changes structure. Later, if the molecule is exposed to a catalyst or other stimulant, it will revert to its original state and release a blast of heat. The reaction is reversible and the molecule can retain the energy indefinitely. Early research indicates that the molecules could be put into arrays that would have about the same energy density at lithium ion batteries. The key to the research is creating an energy barrier that prevents the molecule from reverting back to its original state on its own.
Because the raw materials are relatively common, heat batteries could be somewhat inexpensive.
Fabulous, eh? Yes -- but carbon nanotubes have an ornery side. Manufacturers have had difficulties in turning carbon atoms into large volumes of consistent, identical nanotubes. Often, manufacturers get large batches of nanotubes with varying properties. Then comes the challenge of organizing curly fibers measuring 10 to 20 nanometers (or 10 billionths of a meter) in length into an even array. IBM and NEC began working on nanotubes back in the early '90s, after all, and you don't see a plethora of nanotube products on the market, other than the occasional nanotube-enhanced tennis racket. A number of startups in the early 2000s promised cheap memory chips with an infinite life based on carbon nanotubes. The chips might last forever -- but the companies didn't. This is the cutting edge of material science: it's not easy.
Still, it's a striking idea, and if Grossman and Kolpak can pull it off, start passing out the lifetime achievement awards. You could also see cross-breeding with other solar storage concepts at MIT, where Daniel Nocera is already working on a catalyst that can allow sunlight to produce hydrogen from water. The research is the basis of startup Sun Catalytix.