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Joel Young
Joel Young

So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?

July 28, 2009

Okay - well I acknowledge that, as cool as Tesla’s work was, it probably isn’t very practical in today’s world for all of the obvious reasons.    Nonetheless, we can still learn a lot from this work as to how it relates to other wireless power solutions under development today.  Unfortunately, while promising experimentally, wide availability of products has not yet been realized, but it is only a matter of time and I’m convinced that we will see easy to use, cost effective, personal area wireless power within in the next few years.   But how will it work?Other than solutions like harvesting RF (which we talked about a few blogs ago), the cornerstone for practical wireless power is related to some type of inductive coupling.  I recognize that some of you physics purists might take exception to my terminology.  In any event, the idea is to extend near-field effects over a distance.    In the Tesla solution discussed in the last blog, the earth was turned into a giant coaxial cable where energy was transferred via magnetic field, guided by the earth’s atmosphere acting as a dielectric, thereby extending the distance of inductive coupling.   In my searching, I’ve come across another approach for extending the reach of inductive coupling to form what I will call personal area wireless power.

The most intriguing methods of promise are variants of something called Resonant Induction.  This work has been pioneered by some really smart people at MIT as part of the MIT Wireless Power Project.   Other work, using slightly different techniques has also been developed at the University of Florida.  The concept is to use resonance to extend the distance and “guide” the magnetic flux.  I know this sounds a bit strange and I readily admit that I don’t completely understand it completely.  But you should think about it in the same way you think about a tuning fork.  If you strike a tuning fork, you might not be able to hear the sound of its vibrations over much distance, but another tuning fork that has the same resonant frequency, will easily vibrate over some distance.  Remember that the resonant frequency is the natural frequency of vibration. In the concept of the tuning fork, the sound vibrations appear to “tunnel” between the two forks.  To do this electromagnetically, we take a Tesla coil and bend it in a circular shape.   Next the really cool part - on the ends, where the Tesla coil would typically touch the ground and the air, capacitance plates are placed so the ends look like a capacitor.  See the figure below.

blog1.jpg

From your old circuit days, you might think of it as creating a sort of LC resonator where the resonant frequency is related to the product of the inductance and capacitance.  Using a high resonant frequency, the magnetic flux appears to be “tunneled” to the receiver as long as the receiver has the same resonant frequency.   Even though we use the term “tunneling” as a metaphor, just like the tuning fork, it appears directionless.    Of course distance is still limited to single digit meters and the amount of power will be limited by emissions constraints.  Finally for those of you movie fans out there, I personally notice a resemblance to the “Flux Capacitor” - just imagine what could happen if Doc Brown put 1.2 Giga-Watts into one.

Posted by Joel Young on July 28, 2009 | Comments (7)

September 15, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
MaxwellFan commented:

The coolest thing about Tesla's work was his deep understanding of Maxwell's original 20 equations of 20 variables... not the emasculated 4 vectorized Heaviside versions being taught today in engineering classes.
In one of his 'power transmission' experiments, Tesla noted that there was more power being received by the receiver than it should have gotten (based upon the integration methods used in electrical engineering governing power and distance variables). This was the basis of his electric car, which was powered by a distant transmitter. This was also what scared the crap out of J. Pierpont Morgan (the energy sector super magnate of the day)and why he eagerly bought out Westinghouse and 51% interest in all of Tesla's existing and future patents, then pulled the financial rug out from under Tesla to keep his ideas from ever becoming reality. We may never know for sure what Tesla saw. But, an ansatz of Maxwell's and P.A.M. Dirac's theories may provide an answer without necessarily frying some poor soul's pacemaker in the process.


September 15, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
MaxwellFan commented:

The coolest thing about Tesla's work was his deep understanding of Maxwell's original 20 equations of 20 variables... not the emasculated 4 vectorized Heaviside versions being taught today in engineering classes.
In one of his 'power transmission' experiments, Tesla noted that there was more power being received by the receiver than it should have gotten (based upon the integration methods used in electrical engineering governing power and distance variables). This was the basis of his electric car, which was powered by a distant transmitter. This was also what scared the crap out of J. Pierpont Morgan (the energy sector super magnate of the day)and why he eagerly bought out Westinghouse and 51% interest in all of Tesla's existing and future patents, then pulled the financial rug out from under Tesla to keep his ideas from ever becoming reality. We may never know for sure what Tesla saw. But, an ansatz of Maxwell's and P.A.M. Dirac's theories may provide an answer without necessarily frying some poor soul's pacemaker in the process.


August 29, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
newark commented:

This blog is a joke. Stop writing about stuff you don't understand.


August 1, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
Jeff Prystupa commented:

It could have an application in power distribution, but that is a significant loss of power to design around.


August 1, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
kc6zut commented:

Not to mention all the RFI issues. Even wireless digital communication modes are susceptible to very high fields in close proximity. And don't get me started on the interferrence potential to analog signals.


August 1, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
Santhoff commented:

It appears the statement "What is old is new again" applies here. A variation on Tesla but still the basic fundamentals. What really strikes me here is one of efficiency. Numbers I've seen for even Resonant Induction are in the 10% to 20% range. With the whole "Green" movement will consumers and environmentalists tolerate putting 1000 watts into a device to yield 200 watts at the other end? Even more concern is who will want to stand in the beam of 1000 watts going through the air? Even at lower powers it would be hundreds of watts going over the air. What about potential health effects of such long term exposure. Neat idea but it appears to need a lot more thought and work before we see this in the market any time soon.


August 1, 2009
In response to: So all of Tesla’s work was cool, but how about a practical use of wireless power for say 10 to 20 feet?
Lev commented:

It strikes me, that bad ideas die hard. By now my attitude hardened to the point, that the MIT "inventors" deserve a juicy lawsuit to knock some sense into them. I am referring to the unavoidable stray fields affecting pacemakers and similar devices. If you bother to look closely, the fields are NOT constrained any way.
Hence, accidents are inevitable. If you disagree, please put your money on the line.

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