Sony prototype sends electricity through the air

Despite the numerous technologies that send data through the air, there's one cable that most gadgets can't do without at some time. The power cable remains a necessary but sometimes unsightly part of many electronic appliances, but even that might be on the way out.

Sony said today it has developed a prototype power system that can send enough electricity to power a television set wirelessly over a short distance. In tests, the company succeeded in sending a conventional 100-volt electricity supply over a distance of 50 centimeters (about 19 inches) to power a 22-inch LCD television.

The system achieves this feat through magnetic resonance. A power supply feeds electricity into a square coil of wires 40 cm (about 15 inches) across, called the primary coil, to produce a magnetic field. A secondary coil brought within the magnetic field causes a current to be induced, and the electricity transfer is completed.

Both devices have to be tuned to the same resonant frequency for the power transfer to be successful, but alignment of the two coils isn't necessary, Sony said. It also means that metallic devices placed inside the magnetic field won't cause the coils to heat up.

There are drawbacks, including the system's efficiency and the distance over which it works. Sony's prototype set-up was 80% efficient, which meant a fifth of the power fed into it was wasted. Further losses occurred in circuitry connected to the secondary coil so the original 80 watts of power was cut by roughly a quarter to 60 watts once it had made its way through the system.

To extend the distance, the company said it has developed passive relay units that, when placed between the primary and secondary coils, can extend the total range up to 80 cm.

Sony's announcement discussed development of the basic technology for the system. There are no details on when it might reach the commercialization stage or begin appearing in products.

Copyright © 2009 IDG Communications, Inc.

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