Wireless Power May Cut the Cord for Plug-In Devices, Including Cars


A mobile phone that charges in your pocket, a flat-screen TV that needs no power cord, a car fueled by a cordless panel in the floor: In a nondescript building just outside Boston, these and other applications of wireless electricity signal a future with fewer snaking cables.

WiTricity, a company spun off from research at the Massachusetts Institute of Technology (MIT), aims to redefine how people use energy, making it possible to power devices without ever plugging them into an outlet. In WiTricity’s lab, various devices run on power transmitted via electric coils through the air.

“It is not hard to imagine that in the next few years, you go to a coffee shop, sit down in a chair, sign into a power zone, and charge your phone or laptop,” said Richard Martin, editorial director for Pike, a market research group that focuses on smart-energy solutions. “We predict this technology taking off in a similar fashion to how Wi-Fi got its start a decade or so ago.”

Martin says the industrial potential for wireless power is huge, especially in the realm of electric vehicles and wireless sensors, where harsh environments make it difficult to run wiring. In addition, he says wire-free electricity transmission is often a more convenient, greener alternative to conventional plug-in charging. (See related blog post: “Wireless Power Can’t Yet Replace Utility Poles, but Could Offer More Options for Electronic Charging”) “Part of this is that there is an obviously big space in the market waiting to be filled,” Martin said.

WiTricity CEO Eric Giler imagines a future where power devices are embedded in the walls and carpets of homes, making for a truly wire-free household. He says with a big enough power supply and small wireless repeaters, one could even power a grocery store or office building.

Conventional charging devices such as the cord for a cell phone use electromagnetic induction to transmit power. Through electromagnetic induction, an electric current is sent through a magnetic field generated by a power conductor to a smaller magnetic field generated by a receiving device. (See related quiz: “What You Don’t Know About Electricity”)

“Think of your electric toothbrush,” Giler says. “It works very efficiently, but the problem is that it can only transmit power wirelessly a few inches.”

WiTricity devices share energy through magnetic fields as well. However, unlike those generated by your toothbrush or iPod cable, WiTricity’s devices produce magnetic fields through a process called resonant magnetic coupling, which allows power to be transmitted several meters in distance.

Resonant coupling is a well-understood concept illustrated by many everyday examples. A child pumps her legs at the resonant frequency of a swing to fly through the air, or an opera singer shatters a wine glass by singing a single note at a frequency that matches the acoustic resonance of the glass.

WiTricity founder and MIT professor of physics Marin Soljačić wondered whether electricity could be passed from a wall outlet to an electronic device in a similar manner after he was awoken late one night in 2007 by the beeping of his wife’s dying cellphone.

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