Sony prototype sends electricity through the air

Despite the numerous technologies that exist for sending 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 modern electronic appliances -- but now even that might be on the way out.

Sony has developed a prototype power system that can send enough electricity to power a television set wirelessly over a short distance, it said Friday. In tests the company succeeded in sending a conventional 100 volt electricity supply over a distance of 50 centimeters 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 across, called the primary coil, to produce a magnetic field. When a secondary coil is brought within the magnetic field this causes a current to be induced and so the electricity transfer is completed.

Both devices have to be tuned to the same resonant frequency for the power transfer to be successful but that also means exact alignment of the two coils isn't necessary, said Sony. It also means that metallic devices placed inside the magnetic field won't cause them 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 percent efficient, which meant a fifth of the power fed into it was wasted. Further losses occured 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 on Friday was of development of the basic technology for the system. As such there are no details on when it might reach the commercialization stage and begin appearing in products.

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