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Author Topic: Wireless power with non-radiative magnetic resonances !  (Read 9144 times)

hartiberlin

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Wireless power with non-radiative magnetic resonances !
« on: May 17, 2007, 08:41:59 AM »
Hi All,
this is a new and very interesting wireless power transfer technology.

Have a look at this:


http://www.mit.edu/~soljacic/wireless_power.html

and their papers:

http://www.aip.org/ca/2006/soljacic.pdf

and more technical:

http://arxiv.org/ftp/physics/papers/0611/0611063.pdf

It seems it is based on the High Q of an LC circuit.

So at resonance the receiver just pickups the energy of the transmitter
but otherwise not.

Very interesting.

Regards, Stefan.
« Last Edit: May 17, 2007, 09:09:09 AM by hartiberlin »

hartiberlin

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #1 on: May 17, 2007, 08:51:52 AM »
There was somebody over here,
who had claimed to have built a simular device with a magnetic resonance
transmitter and an array of at least 2 high Q   LC circuit coil  receivers
and he claimed to have gotten overunity with it, so that the
receiver also "sucks" adiitional power at the resonance frequency
from the stray environment magnetic radiation....

So here is now a professor from MIT that seems to do simular things...
although not claiming overunity...

When I find again the other thread here I will post again the link,
but I don?t find it right now, maybe one of you ?
Thanks.


Regards, Stefan.
« Last Edit: May 17, 2007, 09:12:23 AM by hartiberlin »

exnihiloest

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #2 on: May 17, 2007, 03:10:38 PM »
Hi All,
this is a new and very interesting wireless power transfer technology.

Have a look at this:


http://www.mit.edu/~soljacic/wireless_power.html

and their papers:

http://www.aip.org/ca/2006/soljacic.pdf

and more technical:

http://arxiv.org/ftp/physics/papers/0611/0611063.pdf

It seems it is based on the High Q of an LC circuit.

So at resonance the receiver just pickups the energy of the transmitter
but otherwise not.

Very interesting.

Regards, Stefan.

Hi all,

The coupling between two high Q resonnant circuits in order to transfer power is not really new. The system works, some are used at very short distance to power implants in the human body, but generally it has little practical applications for the following reasons:

- the source circuit must operate at low frequency otherwise it radiates too much. An example from Marin Soljačić is a 1 meter loop operating at 10 Mhz. Such loops are real HF antennas that radiate up to several thousands Km around (they are used by ham radio operators). They are not convenient for short range distance.

- when the circuits operate at low frequencies (some tens to hundreds Khz), they radiate nearly nothing but:
   *the range distance is shorter
   *it is harder to get a high Q at a stable frequency
   *the coupling and resonnant frequency are very changing, depending on the proximity of conductive materials -human body included- that influence the resonnant frequency, or on the relative position and orientation of the loops.
Then the power at the receiving loop can change from several order of magnitude.

I think this system is quite intended for very short distance (< 1 mtr) between not moving objects requiring low power.

Fran?ois




sypherios

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #3 on: May 17, 2007, 10:15:23 PM »
I must admit this idea sounds great and all, but we already know that power lines and such are causing dementia and tamper with our natural physiology. I cannot believe that energy being sent out wireless would be safe, it would do alo of harm to people in the room. it sounds good but there would have to be decades of testing done before release.


          Sincerely Sypherios

otto

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #4 on: June 08, 2007, 06:19:51 PM »
Hello all,

@Stefan

a few minutes ago I readed in our newspapers and it was onTV that Soljacic was the first who did this.

In the same moment I sent a email to Soljacic and explained him that the news here claimed he was the first.

For all to know, TESLA WAS THE FIRST!!!!!

Im waiting what Soljacic has to say.

Otto

Super God

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #5 on: June 11, 2007, 11:31:46 PM »
Right on.  Tesla did nearly everything we are 'discovering' about a hundred years ago.  He was a true genius!

Paul-R

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #6 on: June 12, 2007, 03:47:30 PM »
Soljacic seems to be saying that the radiator radiates power, and the
receiver receives power by virtue of being tuned. But the power which
radiates out and does not hit the receiver is NOT wasted. How can
this be?
Paul.

omnispace

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #7 on: July 04, 2007, 02:52:45 AM »
Soljacic seems to be saying that the radiator radiates power, and the
receiver receives power by virtue of being tuned. But the power which
radiates out and does not hit the receiver is NOT wasted. How can
this be?
Paul.

I believe it is re-absorbed by the radiator.  The physics might be a little beyond my capabilities but I will try to explain it anyway:

If there is no receiver present, the radiator acts like a normal inductor.  It doesn't have any significant resistance; it just stores energy and returns it later.

If a receiving coil (with the same resonant frequency) is within a few meters, the magnetic field energy isn't just stored, it is transferred to the receiver.  The receiver isn't close enough for the coils to act like a transformer, though.  Instead the waves (photons?) are able to "jump" across a few meters of air, similar to quantum tunneling.  Here's an informative link:

http://en.wikipedia.org/wiki/Evanescent_wave_coupling

Evanescent waves are also mentioned in my undergrad-level electromagnetics book, so I don't think this is fringe science, just new technology.

hartiberlin

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Re: Wireless power with non-radiative magnetic resonances !
« Reply #8 on: July 04, 2007, 03:13:02 AM »
This sounds right, as a parallel L C circuit has a very high ohmical resistance, so at the resonance frequency the transmitter just sees a very high output resistance only and thus the transmitter does not draw much power...
I wonder, how this changes, if a receiver L C circuit with the same resonance frequency is near by. Then probably the Q of the transmitter LC tank will change and thus it will draw more power from the power supply.