Earth electric

摘要

Earth glows. Not in a fiery, intense visible light as the sun does. But lie down on the ground and you can feel its warmth. Take an infrared photo from orbit and you will see the heat radiation it constantly pumps out into the frigid void of space. It is an immense flow of energy - and one that currently goes to waste. But need it? Not if a bright idea from a group of researchers at Harvard University works out. They think we can use some of this heat radiation as it passes out into space to generate electricity. It is, on the face of it, an odd idea, using a heat flow away from us, rather than towards us, to make power. "To generate power by emitting, not by absorbing light, that's weird... it's highly counter-intuitive," says team leader Federico Capasso. But get it to work, and solar panels could be built that absorb light from below, as well as from above-and even continue delivering juice long after the sun has set. Too good to be true?