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Ultimate Wireless: Cableless Recharging |
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Written by Adam Gosling
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Wednesday, 15 November 2006 |
Wouldn't it be great
if you didn't have to plug in your laptop or mobile phone to recharge
it? Sounds like a pipe dream doesn't it. But we may not be that far
from achieving it thanks to the insight and hard work of a researcher
at MIT.
Marin
Soljacˇic´ (pronounced Soul-ya-cheech)
of the Massachusetts Institute of Technology has presented research which shows how wireless energy could power future gadgets.
The MIT team, which includes researchers Aristeidis Karalis and John
Joannopoulos, is working on a demonstration of the technology.
It's
a pretty widely known (and used) physics phenomena that you don't need
wires to transmit power - electric motors rely on this.
Electric motors
and power transformers contain coils that transmit
energy to each other by electromagnetic induction, but it has never
been used to transfer energy from one point to
another because it is typically very
inefficient, and can even be dangerous. The waves tend to spread in all
direction, so most of the energy is lost to the environment.
The key to the solution was to work out how close-range induction could potentially
transfer energy over longer distances, say, from one end of a room to
the other.
The system would use what non-radiative energy transfer, something
well known, but never used in this way. 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
(apparently?).
"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," says Marin
Soljacˇic´.
With the proposed 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.
In addition to consumer electronics, wireless energy
could find industrial applications, for example powering freely-roaming
robots within a factory pavilion.
Abstract at http://www.aip.org/ca/2006/soljacic.htm
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