In the past, beaming electromagnetic energy has proven difficult because it scatters broadly, radiating in all directions rather than to just the intended electrical device.

A series of successful experiments conducted at the Massachusetts Institute of Technology suggests otherwise, however. MIT physicists believe they can project a magnetic field from a length of wire whose ends nearly touch. The gap between the ends makes electrons surge back and forth at a specific rate, creating a magnetic field with a characteristic frequency. Since the electrons in a matching coil would have the same frequency, they would pick up the magnetic field.

Just as a singer can break a crystal glass that resonates at the same frequency as her voice, the MIT scientists discovered how to get a recharging device and a power-hungry gadget to resonate at the same frequency, allowing the efficient exchange of energy.

To prove their theory, the physicists -- who dubbed the process WiTricity -- used a pair of copper coils with a 2-foot diameter.
One was a transmitter attached to a power source, the other a receiver placed seven feet away and attached to a light bulb. When the power to the transmitter was turned on, the bulb lit up.

The process, MIT assistant physics professor Marin Soljacic tells The Associated Press, is "very reproducible. We can just go to the lab and do it whenever we want."

A wireless power system would have limited range, and the range would be even shorter for smaller receivers. But the research team calculates that an object the size of a laptop could be recharged within a few feet of the power source.

Theoretically, scientists say, placing one source in each room could provide coverage throughout your home for a host of devices, including phones and laptop computers.

Among the leading efforts to launch commercial devices capable of wireless recharging:

Powercast: Plans a 2008 launch of its Powercaster, a device that uses radio frequency signals to remotely and continuously recharge smaller electronics like MP3 players, computer peripherals, and cell phones.

WildCharger: Developing a line of charging pads that, when plugged into an outlet, will supply a steady stream of power to gadgets placed on top of it.

Fulton Innovation: Its eCoupled technology can be embedded into common household objects, from countertops to car consoles. The circuitry in the base automatically recognizes a device’s charging needs.

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