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Recently I'm working on a project aiming to convert the vibration of sound waves into electricity to charge batteries using a piezoelectric material (MFC type). I was trying to use the human voice as an input, but theoretically it was not enough, so do you have any ideas about some places that I can apply my project on it (that must be noisy or can give me vibrations)?

Moreover, has the MFC material been used before in this application? If I used many pieces of it in parallel would that help?

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  • \$\begingroup\$ Construction sites? The end of a runway at a busy airport? A little math will demonstrate that even in locations like these the amount of energy to be harvested is extremely low. \$\endgroup\$ – Nick Johnson Jun 29 '15 at 12:44
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    \$\begingroup\$ As @NickJohnson said, the vibrational energy of sound waves is extremely low. The real fact is that the human ear is an extremely sensitive "device", so even sounds that make you feel pain have a comparatively low energy level. \$\endgroup\$ – Lorenzo Donati Jun 29 '15 at 13:29
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    \$\begingroup\$ BTW this site has lots of info about acoustics. Note the table at the beginning. If you were standing at 50m away from a Jet aircraft you'd get 100W/m^2 of power, that is you would need a 1m^2 transdoucer to capture 100W (and that is the best case). Then you'll have to factor-in conversion losses (which I suspect will be large). If you get that near to an aircraft, probably you would get much more energy out of an alternator connected to a propeller exploiting the exhaust gas of the jet engine (if you don't get roasted first). \$\endgroup\$ – Lorenzo Donati Jun 29 '15 at 13:43
  • \$\begingroup\$ Jet planes are relatively rare (not so many airports out there) - a bridge, a roadway, a tram line, a railroad, a dam are all good candidates. \$\endgroup\$ – sharptooth Jun 29 '15 at 14:15
  • \$\begingroup\$ googling piezo and MFC ewh.ieee.org/r6/san_francisco/nntc/events/… \$\endgroup\$ – George Herold Jun 29 '15 at 15:06
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Try to harvest the vibrational energy from your car engine, because the energy is free and anything you get will improve fuel economy.

And if you could get enough to remove the alternator then you could get rich.

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Once in a National Geographic documentary they have said that:

If all the people on Earth would shout with all they can and this energy is harvested it will only raise the temperature of 100ml water by 15 degrees.

So you should try some serious energy sources like mentioned in Autistic's answer.

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By the time you get to sound amplitudes where the piezo would function as you want, it would probably be better to use a speaker voice coil. The latter is better for anything that has significant linear displacement. Piezo works best as small displacements and high frequencies.

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