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Wind power generator

  1. Apr 13, 2008 #1
    I have to construct a wind power generator out of straws. It has to provide no less than 3V and .2W for a period of 1 minute and be able to withstand a horizontal force of 15N.
    How would I determine what size the rotor would have to be to create this voltage and current from 15N ?
  2. jcsd
  3. Apr 15, 2008 #2
    Can you say any more about how you're going to form the rotor out of straws?
  4. Apr 16, 2008 #3
    The tower is going to be made out of straws, the rotor can be made out of anything. Im not sure about what im going to use yet for the rotors, got any ideas?
    The only formula I have found for wind tower power output has a velocity variable and since I only know the force the wind will have I cant use it.
  5. Apr 16, 2008 #4
    Can you use an cup style anemometer as a rotor? I believe the formulas for these are readily available. How tall will your tower be?

  6. Apr 16, 2008 #5
    The tower has to be 40cm tall. Is that tall enough?
  7. Apr 17, 2008 #6
    They way I would approach this is:
    First I would have to figure out what motor I should use -- if you are provided with one, what motor RPM corresponds to an output voltage of 3V with a given load that would consume .2W (this can probably be tested).

    Once I know the RPM, I need to know what torque is required to maintain that rpm.
    As was said above, a cup anemometer is probably the easiest to build. The force on the device would be the the difference in drag between the cups facing one way and the other, and the bigger radius they sweep the larger the torque.
  8. Apr 17, 2008 #7
    I'm not sure why you're concerned about the height.
  9. Apr 17, 2008 #8
    What will be the velocity of the wind source used to test this device?

    How will you apply the 15N horizontal force to test the tower for rigidity?

  10. Apr 17, 2008 #9

    With a 350mm diamater, 3 blade household fan running at full speed.

  11. Apr 17, 2008 #10
    How did you determine that the fan exerts a force of 15N?

    Do you have a controlled way to rotate the electric motor? For example, an eggbeater crank style hand drill or a variable speed electric hand drill?

    Do you have a volt meter and some resistors so you can put a load on the motor and test it's output?

    What other materials besides straws can you use to assemble the tower? Are they paper or plastic straws?

    Regarding the design of the rotor the first thing you need to determine is how much rpm you need on the motor to output .2W at 3V. Unless you already have an rpm specification for the particular motor you're using you're going to have to measure it. Do you have a method in mind for doing that?

  12. Apr 18, 2008 #11
    It says in the assignment task sheet that the wind will be 15N.
    What do u mean by control the rotation of the rotor? Do you mean the speed? If so, then this would be unnecessary since the fan will provide a constant velocity wind.
    Do you think I should build it with 2 or 3 blades? We get marked down the heavier the tower is.
  13. Apr 18, 2008 #12
    What grade level is this project?

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