WiTricity

Why is this taking so long to achieve?

Wireless energy promise powers up
A clean-cut vision of a future freed from the rat's nest of cables needed to power today's electronic gadgets has come one step closer to reality. US researchers have successfully tested an experimental system to deliver power to devices without the need for wires. The setup, reported in the journal Science, made a 60W light bulb glow from a distance of 2m (7ft).

WiTricity, as it is called, exploits simple physics and could be adapted to charge other devices such as laptops. "There is nothing in this that would have prevented them inventing this 10 or even 20 years ago," commented Professor Sir John Pendry of Imperial College London who has seen the experiments. "But I think there is an issue of time. In the last few years we have seen an exponential growth of mobile devices that need power. The power cable is the last wire to be cut in a wireless connection." Professor Moti Segev of the Israel Institute of Technology described the work as "truly pioneering".

Energy gap
The researchers from the Massachusetts Institute of Technology (MIT) who carried out the work outlined a similar theoretical setup in 2006, but this is the first time that it has been shown to work. "We had a strong faith in our theory but experiments are the ultimate test," said team member Assistant Professor Marin Soljacic. "So we went ahead and sure enough we were successful, the experiments behave very much like the theory."
...
"These results are encouraging. The numbers are not far from where you would want for this to be useful," said Professor Soljacic. The system exploits "resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied. When two objects have the same resonance they exchange energy strongly without having an effect on other surrounding objects. ... Instead of using acoustic resonance, WiTricity exploits the resonance of low frequency electromagnetic waves.

HOW WIRELESS POWER COULD WORK
1) Power from mains to antenna, which is made of copper
2) Antenna resonates at a frequency of about 10MHz, producing electromagnetic waves
3) 'Tails' of energy from antenna 'tunnel' up to 2m (6.5ft)
4) Electricity picked up by laptop's antenna, which must also be resonating at 10MHz. 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 10MHz [source]


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