The next big thing in solar energy could be microscopic. Scientists at MIT and Harvard University have devised a way to store solar energy in molecules that can then be tapped to heat homes, water or used for cooking. The best part: The molecules can store the heat forever and be endlessly re-used while emitting absolutely no greenhouse gases. Scientists remain a way's off in building this perpetual heat machine but they have succeeded in the laboratory at demonstrating the viability of the phenomenon called photoswitching. "Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle," MIT researchers said in statement about the paper published in the journal Nature Chemistry. "Exposing them to sunlight causes them to absorb energy and jump from one configuration to the other, which is then stable for long periods of time." To liberate that energy all you have to do is expose the molecules to a small amount of light, heat or electricity and when they switch back to the other shape they emit heat. "In effect, they behave as rechargeable thermal batteries: taking in energy from the sun, storing it indefinitely, and then releasing it on demand," the scientists said. The researchers used a photoswitching substance called an azobenzene, attaching the molecules to substrates of carbon nanotubes. The challenge: Packing the molecules closely enough together to achieve a sufficient energy density to generate usable heat. It appeared that the researchers had failed when they were only able to pack fewer than half the number of molecules needed as indicated by an earlier computer simulation of the experiment.
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