Energy from radio waves - Page 1
Forum section: electronics / general

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 14, 2010, 09:11:37 pm
content: http://amasci.com/tesla/tesceive.htmlMaybe half of the problem of wirelessly providing power to cars is already solved by existing radio stations. Now make a resonant antenna out of superconductor, tune it to the frequency of a nearby radio station, and build an electric car to use that energy.

author: Unknown
author_rank: Unknown
timestamp: July 14, 2010, 09:58:05 pm
content: Apart from the crackpot-that-disproves-current-phyics factor, I won't comment on that since I'm not a physicist, there's still the issue of conservation of energy. The antenna might be really large, but any energy received must be transmitted somewhere, I doubt that your average AM radio station is set up for this. If an electrical car uses around 1kW (probably much more), how many cars are there within the area of such an antenna? Tuning an (electrically) huge antenna to an AM radio station would probably kill the reception. He also mentions that you have to get the antenna further off the ground for these frequencies, probably not that practical on top of a car.

author: EEVblog
author_rank: Unknown
timestamp: July 14, 2010, 10:41:41 pm
content: Take the basic theory in my Airnergy de-bunk video and do the math...It's a safe bet you'll get more energy from Flintstones style peddle power (about 500W max).Dave.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 14, 2010, 10:48:59 pm
content: Perhaps the first prototype would be installed on a tall stationary tower instead of a vehicle. It could still be used to power cars by recharging batteries or making hydrogen.It is a source of "free" energy in that drawing from it does not increase the load on the grid, although it is limited.QuoteThe distance might need to be closer than would be practical. It is definitely possible to extract very significant amounts of energy without superconductors as long as you could get it really close.It would be best to shut down those radio stations and use the freed-up power directly, but it's not going to be easy...

author: Unknown
author_rank: Unknown
timestamp: July 14, 2010, 11:06:50 pm
content: Quote from: EEVblog on July 14, 2010, 10:41:41 pmI believe the claim is that the effective area of this antenna is much larger than the physical size, if that's true, it could extract some significant amount of energy from the waves. AM transmitters are also much more powerful than access points. I won't comment on the physics side, but I wouldn't bet on it being true.Quote from: NiHaoMike on July 14, 2010, 10:48:59 pmHow are the radio transmitters fed?Quote from: NiHaoMike on July 14, 2010, 10:48:59 pmOr conserve energy some other way, I doubt that the energy used by radio stations is a significant part of the total power draw for most regions. Might as well not go through the trouble of trying to defy the current understanding of physics just to turn off a few 100kW or so loads, just claiming that AM radio increases the chance of cancer in children on national TV might have the same effect.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 14, 2010, 11:47:42 pm
content: QuoteThey're already running, so recovering the energy is not going to increase the load on the grid. Shutting them down is more effective, but also a lot more difficult.

author: Time
author_rank: Frequent Contributor
timestamp: July 15, 2010, 12:19:17 am
content: I have worked with a traveling wave resonanting ring oscillator where a source magnetron pumps a few MW (2-4 MW) of rf power into a rectangular waveguide system arranged in a circle. With a rough vacuum pulled on the pipes, this was a relatively low loss structure. By pumping the power into the ring in phase so that the rf power interacts constructively with the currently propagating waves power levels of 100s of MWs were achievable with only a MW or so being strategically injected.This is really just a proof of concept point that if you have a resonanting medium with low losses (or totally lossless in the case of super conduction) its possible to create significant amounts of power with enough time.

author: EEVblog
author_rank: Unknown
timestamp: July 15, 2010, 01:17:11 am
content: Quote from: NiHaoMike on July 14, 2010, 10:48:59 pmBingo.And if you are that close you might as well just connect to the grid and void all the ridiculous loses in such a transmitter system.The whole idea is brain dead.Eventually we'll have some form of in-ground resonant coupling chargers for electric cars though. Pull into your garage over the coil and your car gets charged automatically.But pulling energy from remote transmitters on a mass scale is just bunk.Dave.

author: jahonen
author_rank: Super Contributor
timestamp: July 15, 2010, 08:44:53 am
content: Quote from: NiHaoMike on July 14, 2010, 09:11:37 pmThat page says "1KHz resonant, infinite Q", which is not realizable by any known technology. Superconductors work great with DC, but generally don't work with AC at all. Even if you magically had zero resistance everywhere in the resonance circuit, your capacitor would still experience dielectric losses. And once you start loading the resonant circuit to extract useful energy out of it (by putting resistor across it to convert the "free energy" to heat), it sees resistive load and Q will drop dramatically, or, should I say catastrofically. You can get voltage amplification by resonance but not power amplification.I posted this on the airnergy topic, but I'll attach this measurement also here:That is the channel power received from very near cellular base station, not very high power indeed.Regards,Janne

author: saturation
author_rank: Super Contributor
timestamp: July 15, 2010, 10:52:41 am
content: Quite the near ideal Gaussian distribution that...Quote from: jahonen on July 15, 2010, 08:44:53 am

author: Unknown
author_rank: Unknown
timestamp: July 15, 2010, 11:29:26 am
content: AM would probably be a lot more, depending on your distance to the transmitter, you might actually get something approaching 1W if you're close to the transmitter and have a good antenna. Something like a crystal radio produces sound from just the energy in the radio signal, can't imagine this working on anywhere close to 100pW, probably several orders of magnitude more. But the author does appear to confuse voltage and power, and I expect several theoretical and practical issues with the article.

author: jahonen
author_rank: Super Contributor
timestamp: July 15, 2010, 02:47:21 pm
content: In fact it is 140 nW (-38 dBm, which is quite strong actually, GSM is specified to work down to -102 dBm), when the power is integrated across 500 kHz bandwidth. But still not very significant. The spectrum shape should indeed be gaussian, since it is GSM signal which uses GMSK (Gaussian Minimum Shift Keying).If simple resonance would gain so much, then it would be used in all telecommunications systems and deep space communication problems would be solved without huge dish antennasRegards,Janne