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Conundrum

Sat Mar 31 2012, 12:48PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Hi all.
Seems that someone found one of Tesla's lost wireless power patents circa 1912, added some 21st century technology in the form of high temperature superconductors and voila.
Essentially the system works like a virtual antenna which allows low frequency <100 kHz waves to be focussed into a coherent energy beam, so that there is next to no loss over distance.
The patent cited actually mentions using "cooled high conductivity barium metal oxides" so maybe Tesla had this all figured out nearly a century ago but couldn't get the HTS material to work reliably due to a lack of quantum theory.

From what I've been able to find out, the system generates the coherent radio waves by using a superconducting resonant cavity to build up energy, and then Q-switching the output window to allow out brief pulses of coherent energy exactly like a laser, propagating as a soliton wave effect through the air.
The difference here is that this happens at very low frequencies whereas all the current "state of the art" wireless systems use microwaves etc which are far too dangerous for such long distance applications.

Theoretical range could be up to 15000 miles with only a 3% energy loss, and the receiver can be a simple resonant coil and capacitor to convert the waves back into electricity.
The article also mentions the possibility of space to ground solar applications, as the atmospheric losses over 150 miles would be very low indeed.

The interference seems to be minimal, as low frequency waves pass through most substances without significant effects.
Judging by the high efficiency of underground radio using the low frequency band, it should even work where no other method can provide power such as underwater etc.

Obviously this is going to be in "Nature", "New Scientist" and many other magazines shortly with detailed schematics etc.

EDIT:- April fool guys.. That said, judging by the responses it seems that not all of the article is entirely wrong.

-A

Proud Mary

Sat Mar 31 2012, 02:10PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

D'you mean this, AndrÃ©?

Magnetic superlens-enhanced inductive coupling for wireless power transfer

Huang, Da; Urzhumov, Yaroslav; Smith, David R.; Hoo Teo, Koon; Zhang, Jinyun;
Center for Metamaterials and Integrated Plasmonics, Duke University, Durham, North Carolina 27708, USA

This paper appears in: Journal of Applied Physics
Issue Date: Mar 2012
Volume: 111 Issue:6
On page(s): 064902 - 064902-8
ISSN: 0021-8979
Digital Object Identifier: 10.1063/1.3692757
Date of Current Version: 22 March 2012

Abstract

We investigate numerically the use of a negative-permeability â€œperfect lensâ€ for enhancing wireless power transfer between two current carrying coils. The negative permeability slab serves to focus the flux generated in the source coil to the receiver coil, thereby increasing the mutual inductive coupling between the coils. The numerical model is compared with an analytical theory that treats the coils as point dipoles separated by an infinite planar layer of magnetic material [Urzhumov etal, Phys. Rev. B 19, 8312 (2011)]. In the limit of vanishingly small radius of the coils, and large width of the metamaterial slab, the numerical simulations are in excellent agreement with the analytical model. Both the idealized analytical and realistic numerical models predict similar trends with respect to metamaterial loss and anisotropy. Applying the numerical models, we further analyze the impact of finite coil size and finite width of the slab. We find that, even for these less idealized geometries, the presence of the magnetic slab greatly enhances the coupling between the two coils, including cases where significant loss is present in the slab. We therefore conclude that the integration of a metamaterial slab into a wireless power transfer system holds promise for increasing the overall system performance.

Inducktion

Sat Mar 31 2012, 05:21PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

It almost sounds like a RF laser actually. It'd be pretty interesting to see it put to use for true wireless laptops and whatnot!

Proud Mary

Sat Mar 31 2012, 05:43PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I have only the haziest idea about metamaterials, and found this basic outline very helpful in understanding the background to AndrÃ©'s post:

Metamaterials and the Control of Electromagnetic Fields

which is a pdf located here:

Steve Conner

Sat Mar 31 2012, 06:28PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I think as soon as superconductors are involved, the antenna design tradeoff between size and radiation efficiency goes away. If the antenna has zero loss resistance, then it's always 100% efficient.

There is still the issue of what us wireless power amateurs called "couch losses" though: the energy wasted in induction and dielectric heating your surroundings, which are far from being superconductors or lossless dielectrics.

Marko and I have theorized and experimented on using several intermediate LC resonators to enhance power transfer between wireless power coils. MIT's witricity system used two extra helical resonators operating at 27MHz, and I reproduced their experiment here and showed that the resonators improved power transfer. Marko got similar results at a lower frequency using tuned loops, as far as I know.

The metamaterial slab is probably just this in the limit, the metamaterial being composed of a large number of tiny resonators.

Conundrum

Sun Apr 01 2012, 06:01AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Yeah, metamaterials are indeed interesting.

Just a thought, did anyone read about the commercial induction heater based on MgB2 wires? seems that they saved a heck of a lot on electricity as the wires only lose 0.001% as heat instead of the normal copper losses.

I would theorise that if room temperature superconductors ever became cheap to make in wire form, then a lot of "science fiction" gadgets like ray guns and ultra high capacity batteries would be feasible.
Main problem is storing the energy which goes away if you have a superconducting storage coil with a Jc in the 100K amp range.

edit: saves admin deleting it.

-A

Proud Mary

Sun Apr 01 2012, 09:15AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

If an antenna had zero losses, then its Q would be infinite, and its bandwidth zero - and this, I believe, is at the heart of the problem in designing real world applications for superconducting microwave antenna arrays.

Steve Conner

Sun Apr 01 2012, 06:16PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

No, the radiation resistance would lower the Q.

It would still probably be too high for any data transmission, but fine for power.

Pinky's Brain

Sun Apr 01 2012, 06:32PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

What's the advantage over masers or microwave radiators and parabolic dishes?

Proud Mary

Sun Apr 01 2012, 07:24PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I have only a hazy idea about the behaviour of superconductive antennas, so perhaps Steve is right. I'd assumed that if the generator output impedance was losslessly matched to the radiation resistance of the antenna, and that the antenna reactance had been tuned out to zero, then a zero ohm superconductive antenna would radiate all the power that was given to it, and be 100% efficient.

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