[Editors] EMBARGOED: MIT: Wireless energy could power laptops, more

[Elizabeth Thomson]

EMBARGOED FOR RELEASE, TUESDAY, NOV. 14, 2006, 6:20 P.M. EDT

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT: Wireless energy could power consumer, industrial electronics

--Dead cell phone inspired researcher's innovation
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EMBARGOED FOR RELEASE
TUESDAY, NOV. 14, 2006, 6:20 P.M. EDT
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

PHOTO AVAILABLE

CAMBRIDGE, Mass.--Recharging your laptop computer, your cell phone 
and a variety of other gadgets may one day be as convenient as 
surfing the Web-wirelessly.

Marin Soljacic, an assistant professor in MIT's Department of 
Physics, will describe his and his MIT colleagues' research on that 
wireless future on Tuesday, Nov. 14 at the American Institute of 
Physics Industrial Physics Forum in San Francisco.

Like many of us, Soljacic (pronounced Soul-ya-CHEECH) often forgets 
to recharge his cell phone, and when it is about to die it emits an 
unpleasant noise. "Needless to say, this always happens in the middle 
of the night," he said. "So, one night, at 3 a.m., it occurred to me: 
Wouldn't it be great if this thing charged itself?" He began to 
wonder if any of the physics principles he knew of could turn into 
new ways of transmitting energy.

After all, scientists and engineers have known for nearly two 
centuries that transferring electric power does not require wires to 
be in physical contact. Electric motors and power transformers 
contain coils that transmit energy to each other by the phenomenon of 
electromagnetic induction. A current running in an emitting coil 
induces another current in a receiving coil; the two coils are in 
close proximity, but they do not touch.

Later, scientists discovered electromagnetic radiation in the form of 
radio waves, and they showed that another form of it-light-is how we 
get energy from the sun. But transferring energy from one point to 
another through ordinary electromagnetic radiation is typically very 
inefficient: The waves tend to spread in all directions, so most of 
the energy is lost to the environment.

Soljacic realized that the close-range induction taking place inside 
a transformer-or something similar to it-could potentially transfer 
energy over longer distances, say, from one end of a room to the 
other. Instead of irradiating the environment with electromagnetic 
waves, a power transmitter would fill the space around it with a 
"non-radiative" electromagnetic field. Energy would only be picked up 
by gadgets specially designed to "resonate" with the field. Most of 
the energy not picked up by a receiver would be reabsorbed by the 
emitter.

In his talk, Soljacic will explain the physics of non-radiative 
energy transfer and the possible design of wireless-power systems.

While rooted in well-known laws of physics, non-radiative energy 
transfer is a novel application no one seems to have pursued before. 
"It certainly was not clear or obvious to us in the beginning how 
well it could actually work, given the constraints of available 
materials, extraneous environmental objects, and so on. It was even 
less clear to us which designs would work best," Soljacic said. He 
and his colleagues tackled the problem through theoretical 
calculations and computer simulations.

With the resulting designs, non-radiative wireless power would have 
limited range, and the range would be shorter for smaller-size 
receivers. But the team calculates that an object the size of a 
laptop could be recharged within a few meters of the power source. 
Placing one source in each room could provide coverage throughout 
your home.

Soljacic is looking forward to a future when laptops and cell phones 
might never need any wires at all. Wireless, he said, could also 
power other household gadgets that are now becoming more common. "At 
home, I have one of those robotic vacuum cleaners that cleans your 
floors automatically," he said. "It does a fantastic job but, after 
it cleans one or two rooms, the battery dies." In addition to 
consumer electronics, wireless energy could find industrial 
applications powering, for example, freely roaming robots within a 
factory pavilion.

Soljacic's colleagues in the work are Aristeidis Karalis, a graduate 
student in the Department of Electrical Engineering and Computer 
Science, and John Joannopoulos, the Francis Wright Davis Professor of 
Physics. It is funded in part by the Materials Research Science and 
Engineering Center program of the National Science Foundation.

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