The world's domestic refrigerators and air-conditioners all work on the same principle. A liquid is evaporated under low pressure, absorbing the latent heat of evaporation. Elsewhere the vapour is condensed under high pressure, returning that latent heat to a different system. The cycle then repeats. The snag is that the best fluid to use is a halocarbon, which damages the ozone layer. This wouldn't matter except that all refrigerators — especially those in cars — leak. New halocarbon is needed to top them up. So the whole halocarbon problem is merely one of bad plumbing.

Daedalus now has a way out: invent a solid working medium, which cannot leak, and the problem will go away. Most solids are so incompressible that only a small change of temperature with pressure seems feasible. Rubber, of course, warms when you stretch it, as the entropy of the molecules is increased. But Daedalus recalls that carbon nanotube is a valuable probe in an atomic-force microscope. If the force is excessive, the nanotube buckles and folds up totally. This solid collapse destroys the chemically resonant structure of the tube, but is fully reversible — remove the load and it springs straight and true again. Its resonance energy must be absorbed as heat in its collapse, and re-emitted in its recovery.

So DREADCO chemists are packing as much carbon nanotube as possible into a flexible solid, possibly rubber, looking for truly dramatic changes in temperature when the composition is deformed. A small bending or squashing should collapse the nanotubes strongly, so they lose their resonant energy and absorb heat. When the solid relaxes, the nanotubes will reform, lose energy as they reorganize, and deliver it as heat again. The result should be a working solid for a refrigerator.

A solid-state refrigerator poses unusual design problems. A big disc, cylinder or belt will carry the working solid, and will be rotated by a motor. Wheels on the periphery will deform it where cooling is desired, and release it to recover heat. The whole thing will be simple rather than efficient.

The DREADCO team reckon they will be lucky to get more than a few tens of watts of cooling; but with no plumbing to worry about, the new refrigerator should find a useful niche in the market. The automotive market is the obvious one. Efficiency is not very important, the device will not leak or stop working, and cooling power can be increased merely by speeding it up.