Re: About wireless energy transfer

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gav D" <gdingley@xxxxxxxxx>

It's just coupling into an antennas near field isn't it? Like the
close range transmission between to TCs, only here it is coupling
through the electric rather than magnetic field. The near field is
strong near the antenna, but rolls-off at 1/r^3 or worse (depending on
the structure). However the far-field is usually much weaker, but
rolls-off at 1/r^2 - hence it is used for communications.

The problem I have is that the near-field is reactive, the E and H
fields are out of phase, as soon as you draw real power they start to
come back in phase and energy is drawn. This in turn means your
Q-factor will drop and eventually resonance will cease. I guess the
system would have a free-space source impedance ;-)

Gavin

On 2/9/07, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> At 04:01 PM 2/7/2007, you wrote:
> >Original poster: Ed Phillips <evp@xxxxxxxxxxx>
> >
> >Original poster: westland <westland@xxxxxx>
> >
> >A couple of wikipedia articles at
> >http://en.wikipedia.org/wiki/Evanescent_wave_coupling
> >and
> >http://en.wikipedia.org/wiki/Evanescent_wave "
> >
> >    Not clear to me that there are any real "waves" involved in
> > coupling via mutual inductance or capacitance.  Evanescent wave
> > sounds great but.........
> >
> >Ed
>
>
> If the wavelength is very long compared to the distance, then the
> wave coupling reduces to the conventional mutual L or capacitive
> coupling.. (that is, you can ignore the propagation speed of the wave
> from source to sink, and consider it as a quasi static
> system)..{coincidentally, a coworker who's teaching a fields and
> waves class was discussing this the other day}
>
> But, you're right.. evanescent sounds much cooler...
>
> Especially if you can represent a macro phenomenon that everyone
> knows about (electromagnetics) using a more obscure notation with a
> less obvious model (quantum tunneling)... I'm surprised he didn't
> talk about using photons for energy transfer.
>
> And, of course, as others have noted..
> "The team is now trying to develop a prototype device. "