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Re: About wireless energy transfer



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 08:35 PM 2/5/2007, you wrote:
Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

There is a note in the Scientific American magazine about recent research on wireless energy transfer: http://www.sciam.com/article.cfm?chanID=sa004&articleID=E87D47E5-E7F2-99DF-3AE75A880501B215
With a link to a paper:
http://arxiv.org/abs/physics/0611063

Antonio Carlos M. de Queiroz"

Did you find anything in that paper which was new other than the fancy simulations and graphics and obscure terminology? I read it when it first came out and seems to me those guys think they're the first ones to discover that two resonant circuits tuned to the same frequency will couple energy and that the higher the Q the better the coupling? They don't seem to claim anything unreasonable in the way of efficiency. Although they mention a Tesla patent (Wardenclyffe transmitter with no receiver mentioned) I don't think they are at all aware of his World Power System patents or what he was doing at Colorado Springs over 100 years ago. His big "primary around the room" with tuned coils inside it pretty well represents their proposed laptop computer charging setup.

I'd be interested in your comments as the paper annoyed me and I was surprised it got published.
I don't see anything new on the paper, except for the simulations trying to evaluate quantitatively what can be achieved. The result is the expected low efficiency. The authors appear to be aware of the work by Tesla. I think that with the fast progress in the development of very low power electronic devices, it may be practical to power some devices without wires, as is already done with RFID tags. But due to the low efficiency, this technique will never be used to power anything needing more than microwatts, a few meters away at most.

Antonio Carlos M. de Queiroz


I find that about every 10-15 years, someone pops up with a "hey we can send power by RF" scheme of one sort or another. Back in the 1970s, the consulting firm Arthur D. Little did a bunch of studies for solar power satellites that would beam power back to rectenna arrays. There were rectenna powered helicopters, etc. too. Then, people did the same efficiency calcualtions we all do, and said.. gosh, wire works better. Popped up again in the late 80s (as a use for the Shuttle and the "never was" heavy lift shuttle) , and even spawned some potboiler thrillers (solar power satellite runs amok and cooks things on the ground when beam runs astray... typical title "Sunstroke"). Popped up again in the late 90s, early 00s...Hey, we can power rovers on the surface of Mars (notwithstanding that it's cheaper and easier just to fly a small radioactive thermal generator, or, just not drive around at night, as opposed to launching a big old solar panel array, a bunch of high power microwave tubes, etc....)

They're all cursed by the inverse square law and the inevitable conversion efficiency problems.

But hey.. why not keep poking at it. Each time they poke, some practical applications come out (e.g. RFID powered by the incident RF), some new technology gets developed (rectennas), etc.