The idea of wireless power or a need for it is not new but I believe i have a tenable solution. The power is transmitted through sound waves/air vibrations. A Large sub woofer in your living room, cafe, hot spot for example plays a constant, loud, low note (below human hearing range).
The frequency used is fixed and universal and all 'wireless' products have a power generator tuned to this frequency. The sound waves are at a fixed frequency so they resonant a piezo strip in the device which develops a small, but constant current. This will probably be too little for current laptops but phones and pda's could well get enough.-- AliMon, Sep 24 2005 Power of sound waves http://www.cord.edu...8/lecture99_35.html3/4 down. Search for 'power'. [spidermother, Mar 03 2006] Oven at regulo 4... http://news.bbc.co....hnology/6129460.stm [Dub, Nov 15 2006] Wireless power transmission http://news.bbc.co....hnology/6129460.stmWhat do you think? [Ling, Nov 15 2006] Goodbye wires… http://web.mit.edu/.../wireless-0607.htmlMIT team experimentally demonstrates wireless power transfer, potentially useful for powering laptops, cell phones without cords (Via MeFi - http://www.metafilter.com/61953/Wireless-electricity) [Dub, Jun 10 2007] The DRUMS! THE DRUMS!!!!-- jutta, Mar 02 2006 I feel sick.-- wagster, Mar 02 2006 Homework assignment: i) How much energy does the average PDA use? ii) How much energy (or power) can you extract from a sound wave?
I seem to remember some comment about the amount of energy used to heat a cup of tea from room temperature compared to the length of time that one would have to shout to produce the same amount of energy & the shouting time was in the order of thousands of years...-- Jinbish, Mar 02 2006 I've heard something similar - like a stadium full of people shouting might boil a teaspoonful of water.-- hippo, Mar 02 2006 To be fair to AliMon, the lower the frequency, the more power it contains. Unfortunately, low frequencies are omnidirectional and so the power you can extract from the wave decreases with the square of the distance. Much power sent, little power received.-- wagster, Mar 02 2006 [wagster] It's the other way around. Power of a sound wave is proportional to the square of the amplitude and the square of the frequency (link). You might be getting confused by the fact that you need large and powerful subwoofers to have a big effect - our ears don't respond well to these low frequencies so their amplitude has to be large.
Also, [AliMon], objects small relative to the wavelength of sound do not interact much with the sound. That's precisely why good subwoofers are physically large, and why elephants can produce and hear what is infrasound to us. PDAs etc would be too small to extract energy from infrasound. Unless you made them really big.-- spidermother, Mar 03 2006 I stand corrected [spidermum]. You are correct both about power/frequency and the reason for my confusion. Shall read more. Like the idea of a 20m pda though.-- wagster, Mar 03 2006 //20m pda// Reminds me of the one where, due to Moore's law, in a decade or so Macintosh laptop screens will be the size of tennis courts.-- spidermother, Mar 03 2006 I saw one in the Apple store the other day that was too big to work on (I think it was a 32") unless you stood several feet away.-- wagster, Mar 03 2006 I am sick of batteries, so if you can get it to work, croissant!-- ProblemSolver, Mar 30 2006 Odd that this surfaced when the BBC news had a similar topic. See link.-- Ling, Nov 15 2006 (Which is remarkable because it also coincided with the fact that I also happened to post a link to the BBC news item which coincidently covered a similar topic)-- Dub, Nov 15 2006 Oops: Oven at regulo 4. Remarkable indeed, that I should have checked all the dates more carefully. By the way, I will believe it (wireless) when I see it.-- Ling, Nov 15 2006 [link] Not quite the same - as it doesn't require a medium...-- Dub, Jun 10 2007 Omni directional power transmission isn't practical for distances more than a few meters. Theres a few companies working on devices that use resonance and induction to transmit enough energy to run electronics like cell phones pdas and laptops in a room sized aria, basically wifi that charges your battery, But for long range transmission you would have to use something directional like lazers aimed at solar cells.-- Livingfishguy, Aug 25 2007 random, halfbakery