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Can piezoelectric concept be used to generate electricity on a large scale

  1. Jan 28, 2010 #1
    I was going through few books and i found out that piezoelectric concept generates good amount of current but not enough power(wattage) ... As I was thinking of making a project on this concept can somebody tell me how can huge amount of voltage as well as current be generated from piezoelectric cells?

    I have read in one of the threads somebody claimed that constant pressure cannot be used to generate energy!( Can somebody tell me whether its true?)
     
  2. jcsd
  3. Jan 28, 2010 #2
    Hello WBG,

    Kinda backwards on the current voltage thing. Generally, piezo devices move little in the way of charge, but they can develop some fairly high voltages if unloaded (hence peizo lighters in grills & such)

    Piezo devices have been used for transformers in special applications (high isolation an laptop back lighting), but for the most part, magnetic transformers have proven more practical.

    As for energy due to constant force, trying to lift a box that never raises from the floor doesn't impart energy to the box. It actually has to move upwards. And then again, if the box weighs next to nothing, moving it up a bit doesn't represent much energy. It's the weight and the distance upwards that represents work done to raise the energy imparted to the box.

    Constant force on your piezo device will impart energy at the instant the force is applied and the device flexes a bit. Continuing to apply force doesn't impart any more energy. Circuits that use piezo transformers must operate at high frequencies, because each flex imparts very little energy.
     
  4. Jan 28, 2010 #3

    sophiecentaur

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    A million monkeys and a million old cigarette lighters, perhaps?
    Click, click, click
     
  5. Feb 24, 2010 #4
    what concept did you have in mind??
     
  6. Feb 24, 2010 #5
    what if the piezo material is a ceramic ring in which a rotor type motor is played into effect??? the only moving part would be what puts pressure on the ring in the form of rpm (sphere)
     
  7. Feb 24, 2010 #6

    sophiecentaur

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    Power generation is based on the work done in moving something (force times distance) and you need to 'match' your moving source of energy to the generator. To generate piezoelectric power would involve a really really massive force moving through a very small distance.
    The only example of this that I could envisage would be using the movement of the Earth's crust during earthquakes. So you'd need a couple of huge blocks of stone (100s of m square, one in the ground and the other one on top of it. In between would be a large crystal of some piezoelectric material. When an Earthquake happened nearby, the rocks would move relative to each other and you would get a few milliseconds of high power out as the rocks moved relative to each other.

    Perhaps a very long bar of piezo material could be moved (twisted or bent). You are always up against the problem of the high mechanical modulus of such materials which aren't matched to real world sources of mechanical work / energy.
     
  8. Feb 24, 2010 #7
    One of my classmates made a piezoelectric device that turns sound into electricity. It was his senior design project. He put the crystals in a tube that was a resonant chamber for a certain frequency. He barely got any juice out of it but it was a cool experiment.

    Anyway, the way piezos work is that when you bend them, the tend to squeeze charges out of one side. If you bend them back and forth. They can generate a little signal. They won't do anything if you just bend them and leave 'em.
     
  9. Feb 24, 2010 #8

    sophiecentaur

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    Piezo has two problems - matching the mechanical power in and the electrical power out. It seems that you just can't beat coils and rotating magnets!:smile:
     
  10. Feb 24, 2010 #9
    i dont like the term work in physics. its all labor. that being said, the process of using the blocks and a peizo bar is a phase labor and would never work (no idle power) . also piezo crystal are not the way to go , its ceramic. i do however like the novel concept in the sense that out of destruction comes power.

    it terms of large-scale operation. it could work, but only with hyrdo-electric operations.

    @sophiecentaur : agreed / but there is a way to match this ratio with flying colors by using what i like to call a sphere rotor and ceramic based piezo-ring
     
  11. Feb 24, 2010 #10

    sophiecentaur

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    "i dont like the term work in physics."
    I suspect you just like 'playing'!

    "no idle power"
    Not sure I understand what you mean but if you can produce charge displacement and a PD, what else do you need?

    "sphere rotor and ceramic based piezo-ring" Wouldn't you still have the problem of 'source impedance' and matching, even if you can 'wobble' something wildly?
     
  12. Feb 25, 2010 #11
    Peizoelectric material are like electrical sponges. By squeezing the atoms, you displace electrons.But you have to let go for the electrons to 'return back to place'. As proven before, high conductive material are better fit to generate powerful electrical current. Unless you manage to create some quasi superconductive piezoelectroc, and build a good pressure system, it wont be as efficient as a coil/magnet generator.
     
  13. Feb 25, 2010 #12

    sophiecentaur

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    How could it be superconductiong if, at the same time, you expect it to Polarise?
     
  14. Sep 10, 2011 #13
    So, is it true that the magnets in a generator are exciting the electrons in the copper of the windings into outer shells and then they move down the wire as the electricity that we use? If this is true....... then aren't the number of electrons in a finite amount of copper..... finite? If so then how is a generator able to just continue producing electricity indefinitely? Also wouldn't the mass of the copper windings decrease over time?
     
  15. Sep 11, 2011 #14

    sophiecentaur

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    You don't change the number of electrons. You just move them all a few mm in one direction or another. Total charge has to stay at zero.
     
    Last edited: Sep 11, 2011
  16. Sep 11, 2011 #15
    Thanks Sophiecentaur but that makes no sense to me. Can you tell me a good book or website that will give me a good explanation (with graphics) of how generators produce electricity...... how it all works.....
     
  17. Sep 12, 2011 #16

    sophiecentaur

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    There's an awful lot to this subject. Q an A doesn't really suit foundation level learning. Best to look in Wiki about the way electric current flows. No "shells" involved, for example.
     
  18. Sep 12, 2011 #17

    sophiecentaur

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    Have you tried Wiki?
     
  19. Dec 22, 2012 #18
    Is it plausible to use a piezo bending generator mounted with an offset rudder, set up in tidal water flows to generate a meaningful amount of power? The offset rudder would cause it to rapidly bend in alternating directions and under great strain.

    Or would this still not be as efficient as a typical rotary turbine?
     
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