Theory Promises Wireless Power

By Geoff Duncan November 15, 2006

A group of U.S. researchers have outlined a system which, in theory, could be used to send power wirelessly over short distances to electronic devices. If practical, the technology might one day eliminate the need for power cables, adapters, and plugs to charge devices like mobile phones, music players, and computers over a range of a few meters—and the system could be scaled up to handle larger areas or scaled down to power microscopic devices.

Electrical pioneer Nicola Tesla expermented with broadcast power—dubbed “radiant energy”—at the beginning of the 20th century; although he made substantil progress, JP Morgan withdrew funding for the project in part because Tesla envisioned wireless power as a free, unregulated resource rather than a money-generating utility.

According to the BBC, the theory outlined by MIT assistant professor Marin Soljacic, Aristeidis Karalis, and John Joannopoulos is fundamentally different than Tesla’s intended system. The new theory proposes that energy can be transfered between two resonant objects—in this case, two copper antennas vibrating at 6.4 GHz—via frequency resonation. The idea is that one antenna is connected to a wired power source and begins resonating, producing “tails” of energy which can tunnel from one resonant object to another—say, another copper antenna in a mobile phone or laptop. The researchers say any energy not transferred via sympathetic resonance is non-radiant and re-absorbed by the source antenna, and thus may not present the health or safety hazards of transmitting energy via microwaves or infrared radiation. The system could operate over distances of three to five meters, and would not require a line-of-sight between the antennas.

Soljacic was to present the paper at the American Institute of Physics Industrial Physics Forum in San Francisco on November 14.

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