Physics promises wireless power

[tak22]

Here's part of an article from the BBC on wireless power transmission using resonance at 6.4MHz

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"And because we're physicists we asked, 'what kind of physical phenomenon can we use to do this wireless energy transfer?'."

The answer the team came up with was "resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied.
   This would work in a room let's say but you could adapt it to work in a factory
Marin Soljacic

"When you have two resonant objects of the same frequency they tend to couple very strongly," Professor Soljacic told the BBC News website.

Resonance can be seen in musical instruments for example.

"When you play a tune on one, then another instrument with the same acoustic resonance will pick up that tune, it will visibly vibrate," he said.

Instead of using acoustic vibrations, the team's system exploits the resonance of electromagnetic waves. Electromagnetic radiation includes radio waves, infrared and X-rays.

Typically, systems that use electromagnetic radiation, such as radio antennas, are not suitable for the efficient transfer of energy because they scatter energy in all directions, wasting large amounts of it into free space.

To overcome this problem, the team investigated a special class of "non-radiative" objects with so-called "long-lived resonances".

When energy is applied to these objects it remains bound to them, rather than escaping to space. "Tails" of energy, which can be many metres long, flicker over the surface.

"If you bring another resonant object with the same frequency close enough to these tails then it turns out that the energy can tunnel from one object to another," said Professor Soljacic.


Hence, a simple copper antenna designed to have long-lived resonance could transfer energy to a laptop with its own antenna resonating at the same frequency. The computer would be truly wireless.

Any energy not diverted into a gadget or appliance is simply reabsorbed.

The systems that the team have described would be able to transfer energy over three to five metres.

"You could also scale it down to the microscopic or nanoscopic world."

Old technology

The team from MIT is not the first group to suggest wireless energy transfer.

Nineteenth-century physicist and engineer Nikola Tesla experimented with long-range wireless energy transfer, but his most ambitious attempt - the 29m high aerial known as Wardenclyffe Tower, in New York - failed when he ran out of money.

HOW WIRELESS POWER COULD WORK
1) Power from mains to antenna, which is made of copper
2) Antenna resonates at a frequency of 6.4MHz, emitting electromagnetic waves
3) 'Tails' of energy from antenna 'tunnel' up to 5m (16.4ft)
4) Electricity picked up by laptop's antenna, which must also be resonating at 6.4MHz. Energy used to re-charge device
5) Energy not transferred to laptop re-absorbed by source antenna. People/other objects not affected as not resonating at 6.4MHz


http://newsvote.bbc.co.uk/mpapps/pagetools/print/news.bbc.co.uk/1/hi/technology/6129460.stm

[alan2here]

Look down 2 Threads, and you will see the main thread for this descussion, posted yesterday.
http://www.overunity.com/index.php/topic,1703.0.html