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Wireless Transfer of Electrical Power Possible

By Jay Lyman
Nov 16, 2006 2:13 PM PT

A Massachusetts Institute of Technology researcher has explained how the batteries of portable electronic devices could be wirelessly -- and safely -- recharged.

Wireless Transfer of Electrical Power Possible

Such a technological feat could be accomplished by matching the source and receiver in frequency, similar to radio, MIT Assistant Professor Marin Soljacic said at a physics conference in San Francisco this week. The method could enable efficient power transfer over short distances.

Soljacic, who coauthored a paper on the subject with MIT colleagues, recognized the real-world complexities that stand in the way of widespread use of such a technology. Still, it could enable such "novel applications" as powering handheld devices in a room or robotic devices in a factory, he suggested.

New Twist on Old Dream

The MIT team investigated how energy can be transferred efficiently from one long-lifetime resonant electromagnetic state to another through the use of long-tailed, nonradiative modes, Soljacic reported.

Tuning the drain and the source of energy to the same long-lifetime frequency should enable very efficient energy exchange with negligible interaction with other off-resonant objects, he explained.

Real-world intricacies make the model more complex, he noted, but researchers were still able to use detailed theoretical and numerical analyses of real-world situations, along with realistic material parameters, to establish that the nonradiative scheme could be practical for middle-range wireless energy transfers.

"The emerging vast acceptance of autonomous electronic devices (e.g. radios, cell phones, laptops, robots), which are currently being powered by on-site conversion of chemical energy, justifies revisiting the old dream of the pioneers of electrical applications (e.g. Tesla, Edison): transporting electrical energy wirelessly," reads an abstract on Soljacic's talk.

Power Web

Considering the number of laptops, mobile phones and other devices that presently require wires to recharge their power sources, Soljacic's talk has already generated significant buzz in the industry.

While freely radiative transfer models work for data transfer -- including the 802.11 WiFi wireless technology widely used in offices, homes and public places -- the model does not work for power transfer because most of the energy ends up wasted.

However, Soljacic and fellow researchers contend that if the source and receiving device are both resonating on the same frequency, a wireless power transfer could take place in a room or even a factory pavilion.

Keeping the Cord

Given the challenges and possible hazards of such a technology, it would take a more compelling reason than the replacement of a three-foot electrical cord to justify its development, DataComm President Ira Brodsky told TechNewsWorld.

While he recognized the potential for specialized applications of the wireless energy technology -- particularly in such areas as radio frequency identification (RFID) -- Brodsky said he remains skeptical.

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