Wireless power transfer (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 8 Jun 2007 11:21:05 -0600
From: S&JY <youngs@xxxxxxxxx>
To: Tesla List <tesla@xxxxxxxxxx>
Subject: Wireless power transfer

FYI - an article in the June 8, 2007 Wall Street Journal.  If any of you
have more details on the "magnetically coupled resonators", please post it
on this list.  For example, how is it different from magnetically coupled
electric toothbrush chargers?

--Steve Y.

 

 

MIT Scientists Pave the Way

For Wireless Battery Charging

 

By WILLIAM M. BULKELEY

June 8, 2007; Page B6

 

CAMBRIDGE, Mass. -- A 60-watt light bulb that glows even though it isn't
wired to a power source could pave the way for wireless recharging of
cellphone and laptop batteries and the operation of mobile robots without
batteries, scientists reported.

 

A team of researchers at Massachusetts Institute of Technology reported in
the online publication of the journal Science, that they had demonstrated
wireless transmission of electric power by magnetically coupled resonators.
They dubbed their technology "WiTricity" for wireless electricity.

 

 

Marin Soljacic, the physics professor who led the team, said the technology
is sufficiently proved and that "now is a good time to start thinking about
commercializing it." He said that while further development is needed to
improve efficiency, he thinks commercial products could be on sale in "a few
years, if you started working very seriously." He said MIT would handle
licensing of the technology.

 

Prof. Soljacic said that over short distances, wireless transmission appears
to be about 80% as efficient as wired transmission. The resonant devices
interact with each other without interfering with either biological
processes or other electrical devices. Prof. Soljacic also noted that
electricity pioneer Nicola Tesla worked on similar methods for wireless
transmission in the early 20th century, but dropped the idea because it
didn't work over long distances.

 

While wireless transmission of electricity over radio waves is well known,
it's very inefficient because most of the power is dissipated in directions
other than the device that needs the power. Prof. Soljacic's team theorized
that two copper coils tuned to resonate in identical magnetic fields would
assure the power would go only where it was needed.

 

Resonant objects interact only with objects of the same resonance. For
example, if an opera singer holds a high note in a room of wine glasses
filled to different levels, only one glass, which resonates with that note,
is likely to shatter.

 

The researchers' technology uses a copper coil attached to a power outlet to
transmit electromagnetic waves at set frequencies. A receiving coil attached
to the base of the light bulb, can receive the power for a distance up to
seven feet, making it appropriate for rooms.

 

Prof. Soljacic, a 33-year-old who joined MIT from Croatia, said he thinks
manufacturers could include such coils in battery-powered devices such as
laptop computers to make automated, wireless recharging possible.

 

He said he started considering the problem several years ago because he was
often awakened at night by the sound of his cellphone beeping because its
battery was getting low and he had forgotten to put it on its charger.

 

The technology doesn't work over long distances, but it functions well
within average sized rooms in homes, he said. That might make it possible to
build wireless devices that don't require batteries. He noted that many
devices such as robot vacuum cleaners and laptop computers run on less
energy than the light bulb his team lit up.