In contemplating all this EM, I now 'get' the reasoning for the potential use of magnetostrictive materials for their higher Qs for the reception circuit. I'm wondering though, how Kapanadze does it though, if you could elaborate/guess?
@tao, sorry just saw your post. Well, for the longest time I thought he was just demonstrating a resonant converter. From the videos I saw him displaying a battery and inverter to feed his green box, and looking at his diagram from the patent it looked like it was just a step down transformer (outside coil), so I kind of dismissed the importance of the single ground cable. But then when I revisited his patent and realized he mentioned 50 Hz, it clicked for me.
So, If magnetistrictive materials play a part they most likely are inside that coil, if not, no big deal. He seems to describe in his patent a "difference in magnetic fields" produced between the primary and secondary, and he filters this to get the pure 50 Hz. So he is generating a beat frequency of 50 Hz, or a mixing product of 50 Hz, depending on the linearity of his coil/system. If it's linear, it generates a 50 Hz beat frequency, if it's non-linear, he generates an actual 50 Hz frequency.
@ all,
check this out, imagine we have a beat frequency of 50 Hz, with a frequency of 5000 hz. If this type of signal is flowing through a coil, as the current flows at 5000 Hz through the coil, there is always a repulsion between the coil turns, and if the coil is flexible, it can mechanicaly oscillate, and we can tune it to 50 Hz, or the beat frequency. This is a way to use this 50 Hz beat frequency and let it resonat something, in this case, the coil mechanical resonance. Now, a coil that changes its shape alters it's inductance, and so we have a non-linear inductor. We can use this to our advantage and build a parametric oscillator that operates off of this changing inductance. And there you have it, a non-magnetic way of implementing a low frequency resonator, through mechancial vibration.
But what does this do for us?
What it does is simple, if there are magnetic frequencies given off the power grid in your specific country that uses 50 Hz, then this mechanicaly vibrating coil will also be pumped by these frequencies and begin to amplify and capture more energy out of the thin "air".

@ tao, you asked me to guess ...

EM
PS, In my office, I can get about 80 V induced on a wire from the florescent lights, but not much usefull current. However imagine I can drive current from an oscillator in sync with the 60 hz voltage waveform induced from the lights, now we are talking. That's how energy capture works in a nut shell. It's a type of regaging. In many respects, the Tariel Kapanadze extraction of energy should be more powerfull since the electric fields are stronger than magnetic fields, but he is tied to the ground which is a disadvantage if mobility is important.
In summary:
TK is using a monopole antenna, and SM a magnetic loop antenna. Two forms of implementation going after the same energy source! I like the SM version so we can put in a vehicle, but for a house application, the TK device is not bad.