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Piezoelectricity from wind on cars

  1. Dec 21, 2014 #1
    Would it be possible to put piezoelectric devices on the front of a car so that when the car is moving forward, the pressure from the wind on the car and piezo devices produces power to charge a battery?
    If the wind is strong enough, do you think there would be a considerable amount of energy produced?
     
  2. jcsd
  3. Dec 21, 2014 #2

    phinds

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    Any power you get from doing that will come ultimately from the gasoline in the engine. If you think you could get something "free" in this way, you are mistaken.
     
  4. Dec 21, 2014 #3
    No a piezoelectric device requires a change of force to generate electricity so under steady speed conditions there would be no power generated.
     
  5. Dec 21, 2014 #4
    I don't think it would be that free, just reclaiming some of the energy used.

    Oh okay. But, would the slowing down and speeding up of a car be able to produce the change of force?
     
  6. Dec 21, 2014 #5

    NascentOxygen

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    It might be better to arrange a flapping flag to repeatedly hit against an array of piezo devices. More suited to a sail boat, maybe.
     
  7. Dec 21, 2014 #6

    phinds

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    But you would NOT be "reclaiming some of the energy used", you would be requiring the use of MORE gas and wasting some of it in various inefficiencies to get an end result that you can already get from the car's alternator. Your statement makes me think that you DO somehow believe that there would be something free involved.
     
  8. Dec 21, 2014 #7
    How would it use more gas if the car is moving anyway?
     
  9. Dec 21, 2014 #8

    phinds

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    Ah ha ! You DO think it's free energy. Certainly, you could generate energy but this would be at the expense of the kinetic energy of the car, as provided by the gas engine. If you wanted to keep the car running at the same speed as it would if you were not harvesting energy the way you suggest, you would have to supply more energy via the engine. Can you not see that were it otherwise this would be free energy? Free energy leads to perpetual motion machines. They don't work.
     
  10. Dec 22, 2014 #9

    russ_watters

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    Adding such a device would reduce the aerodynamic efficiency of the car/increase drag.
     
  11. Dec 22, 2014 #10
    Oh I see, so the small amount of energy it would generate wouldn't be worth the tradeoff from using more gas
     
  12. Dec 22, 2014 #11

    phinds

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    Correct ... it would be a net loss of energy, as I have said repeatedly.
     
  13. Dec 22, 2014 #12

    OCR

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    Lol, absolutely nothing gets past you... as I have seen repeatedly... :oldeyes: ... :biggrin:
     
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