Wireless power transfer pursued

SAN FRANCISCO, CALIFORNIA - Imagine juicing up your laptop computer or cell phone without plugging into an electrical socket. That luxury could be provided by wireless power transmission, a concept bandied about for decades that is creeping closer to becoming viable.

Building off work unveiled last year by Massachusetts Institute of Technology researchers, Intel Corp. demonstrated how to make a 60-watt light bulb glow from an energy source 3 feet away. The Intel team did it with relatively high efficiency, losing only a quarter of the energy the researchers started with.

"That to me is the most striking part about it – transmitting 60 watts at 75 percent efficiency over several feet," Intel's chief technology officer, Justin Rattner, said in an interview. "The power pack for your laptop isn't that efficient... it's one of those things that's almost too good to be true."

Wireless transmission of electricity makes use of some basic physics – electric coils that resonate at the same frequency can transmit energy to each other at a distance.

But this technology has a long way to evolve before it becomes a commercial product. In both the MIT and the Intel work, researchers used charging coils far too large for wide-scale use.

Eventually, a homeowner could attach a large transmitter to a wall – or even bury it inside the wall – and plant smaller receivers inside nearby tables and chairs and other pieces of furniture, creating the ultimate in recharging convenience.