It probably comes as no surprise that your microwave leaks a little energy. Every time you heat up last night’s leftovers, a few electromagnetic waves seep out the door and through the window. It’s nothing to worry about (as long as you don’t stick your head in front and set the thing for a hour-long nuke). And the relevant authorities allow a little waste, as long as manufacturers stay within agreed limits.
Researchers at the University of Tokyo and Georgia Institute of Technology wondered if this energy could be used for something, because these days we can’t afford to waste too much.
And, sure enough, they found that it could. They rigged up a small harvester in front of a microwave door “with a 1-cm-long microwave antenna to generate an electric current that could charge a circuit,” according to an article in the New Scientist. Then, they set the machine for two minutes. The energy they gathered was enough to run low-power gadgets like thermometers, timers, and scales.
For now, the experiment is just a proof-of-concept. But energy harvesting in general is a growing field of research. Scientists are looking at all kinds of ways of capturing more of the free, ambient energy that’s currently lost from equipment all around us. For example earlier this year, a German student showed how to recharge batteries from the energy seeping from power lines, refrigerators, and coffee machines.