Sunday, June 24, 2007

Wireless Power - Time to Cut the Cord!

Have you ever been at the airport with a laptop - searching around your gate for a seat within reach of a power outlet? I have - at airports, colleges, coffee shops and hotel lobbies. While ubiquitous wireless networks have become a productivity boon to business travelers, the lack of sufficient battery life and sources of power quickly . Even when you do find an available outlet, you're vying for it with a half dozen other road-warriors , resulting in a messy tangle of power cords. Fortunately, some very bright people at MIT are working on a solution they call - WiTricity.

Read more about it here -
MIT Harnesses Power Without Plugs. Summarizing, MIT physics professor Marin Soljacic and colleagues were able to light a 60 Watt bulb from 7 feet away - without wires! The device isn't ready for prime time, being only 40 to 45 percent efficient and way too big (2-ft diameter copper coils) to be practical and portable.

For you Electrical Engineers, here is the abstract of the original paper and a photo of the power transmitter in action
, from the magazine Science.

Wireless Power Transfer via Strongly Coupled Magnetic Resonances

André Kurs 1*, Aristeidis Karalis 2, Robert Moffatt 1, J. D. Joannopoulos 1, Peter Fisher 3, Marin Soljacic 1

1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3 Department of Physics and Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

* To whom correspondence should be addressed.
André Kurs , E-mail:

Using self-resonant coils in a strongly coupled regime, we experimentally demonstrate efficient non-radiative power transfer over distances of up to eight times the radius of the coils. We demonstrate the ability to transfer 60W with approximately 40% efficiency over distances in excess of two meters. We present a quantitative model describing the power transfer which matches the experimental results to within 5%. We discuss practical applicability and suggest directions for further studies.

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