Wireless power: no batteries, no cables

MIT researchers say they will soon be able to charge a computer or cell-phone battery from across a room, perhaps making the annoyance of wires or dead batteries a thing of the past.

Massachusetts Institute of Technology scientists and their wireless energy transfer technology may soon eliminate wires that tether our machines to wall sockets, or may keep batteries topped up and ready to go.

"This invention could free us from power cables and ideally replace batteries to a good extent, at least in the context of a home or office setting," said Aristeidis Karalis, a student member of the MIT team that worked four years on the problem.

The team at MIT, a top US academic laboratory, has shown their fledgling "WiTricity" technology can power a 60 watt bulb from a power source two meters (seven feet) away.

That is enough juice to power an average laptop, said Marin Soljacic, a professor of physics at MIT in Cambridge, Massachusetts, who called the experiment a "major milestone."

"The technology is almost at the point where it could be used for a practical application," he added.

The technology is simple and based on resonance, which causes an object to vibrate when energy of a certain frequency is applied to it, Soljacic explained.

Two resonant objects on the same resonance frequency can exchange energy efficiently, while interacting weakly with objects that are not on the same wavelength.

For the light bulb experiment, the MIT team used electromagnetic resonators in the form of copper coils.

One of the coils was attached to a power source. The other acted as a receiver.

The transmitter emitted electrical vibrations of a certain frequency which rippled across an electromagnetic field to the receiver or "resonator."

The researchers now plan to make the WiTricity technology more efficient, perhaps by using different materials, though they do not believe its range will reach beyond a room or a factory floor.

However they are confident the system can improved to the point that consumers can dispense with power cords for their laptops, PDAs, Blackberries or cellphones if they are being used in the same room as the power source.

"This is a major milestone," said Soljacic. "The technology is almost at the point where it could be used for a practical application."

Details of the experiment appear in the journal Science.

Inherent limits mean the technology could only recharge gadgets within a few meters – effectively in the same room.

The technology has already piqued the interest of some big names in consumer electronics, and venture capitalists have been lining up with offers for the six MIT researchers who are now figuring how to turn their pet project into a marketable commodity.


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Wireless power: no batteries, no cables