Technology

29. First Step to Wireless Electricity

By Jeffrey WintersDec 21, 2007 12:00 AM

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Thanks to wireless technology, rechargers could become a thing of the past. In July, researchers at MIT extended the Wi-Fi concept to allow the beaming of power to anything that uses electricity. Freeing electrical transmission from power lines has been a dream since the days of pioneering electrical engineer Nikola Tesla. Today electricity can be transmitted via magnetic induction in such things as security swipe cards. But sending electricity this way is practical over only the smallest of distances.

The MIT Wi-Fi power demonstration, first published in the journal Science, uses two precisely tuned coils to boost efficiency. Power is loaded into one large coil a couple of feet in diameter, causing electricity to surge back and forth more than a million times a second. These pulses of electricity create a flickering magnetic field that passes over most objects, except the powered coil’s mate (which can be made small enough to fit into consumer electronics). The mate strongly resonates with the magnetic field, inducing electrical surges that can be tapped to recharge a cell phone or power a computer.

“We think this can be useful over distances of a few meters,” says physicist André Kurs, who was a member of the team. “It could supply power to just about any household object that needs electricity.”

People might think twice about this technology if it meant turning their living rooms into microwave ovens, but the pulsing magnetic fields of the MIT system don’t interact much with walls, people, or even tinfoil. “When I was in the lab, I had various gadgets on me—a watch, credit cards—and everything continued working fine,” Kurs says. “And I certainly didn’t feel myself heating up.”

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