Wireless revolution is about to deliver power, too - without cables

In a conference room at WiTricity Corp.’s Watertown headquarters, a television set sits on a clear plastic stand. No power cables run from the wall to the TV, nor does it have a battery, yet the set is broadcasting a documentary.

The power source is hidden behind a painting on the wall, three feet to the rear.

Likewise, a laptop computer on a desk on the opposite side of the room has been modified to show that it has no battery, but is also running without a cable to an electric outlet. The power source is a coil embedded in a bulletin board hanging above the desk.

“In five years, all of this will be stuff people consider normal,’’ said Eric Giler, WiTricity’s chief executive.

WiTricity is developing technology that allows electricity to be transferred through the air over short distances - up to several feet.

Just as a wireless Internet connection does, the technology eliminates the need for cables and batteries, which can be expensive, cumbersome, and may ultimately end up in a landfill.

But Giler sees bigger benefits than mere convenience. The technology, he said, will make electric cars more practical and may one day power implantable medical devices, such as pacemakers.

Giler said he expects the first commercial use of the technology this year, most likely as a charging system for a hand-held device like a cellphone or an MP3 player.

The system was developed by Marin Soljacic, a Massachusetts Institute of Technology professor who last year received a prestigious MacArthur Fellowship - known as a “genius grant’’ - for his breakthrough work in electricity delivery.

Soljacic’s technology is based on resonance and uses a magnetic field that has about the same density as the earth’s.

Giler described the transfer as being similar to the movement of energy through a transformer, where electricity “jumps’’ from one coil to another. Soljacic figured out how to make the energy travel over a greater distance.

“It’s not electricity going through the air; it’s actually a magnetic field,’’ Giler said.

A similar, competing system uses induction, a process in which electricity flowing through a wire creates a magnetic field that can jump to nearby objects. The cellphones and other hand-held devices to be charged are placed on a mat that’s plugged into a wall outlet. But the mats are fickle, and the devices need to be placed precisely, Giler said.

With the WiTricity system, a standard desk is outfitted with a energy-emitting coil underneath the surface. Any object placed on the desk - cellphone, laptop, or optical mouse - can draw power from the coil. The objects don’t have to be arranged in any specific way.

WiTricity’s biggest market, however, may be the auto industry.

Drivers have been reluctant to buy fully electric cars, partly because they need to be plugged in to recharge.

The company said its system could be used to develop a mat that could be placed on a garage floor or even on a driveway. The car could be parked on the mat, eliminating the need for cables.

Soljacic came up with the concept one night while being kept awake by the beeping of his wife’s cellphone, which was low on power.

“On this particular phone, the beeping would only stop when you plugged it in,’’ Giler said.

Soljacic realized he had three options: Get up, find the phone and plug it in; take out its battery; or smash it, Giler said.

“After the third night, he got to thinking about all the electricity running through the walls of his home and figured there had to be a way to harness that energy,’’ he said. “It’s funny to think a whole industry may have been born out of the lousy design of a cellphone.’’