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Homework Help: Power from a wind turbine

  1. Mar 31, 2005 #1
    I have a Thermo I problem:
    Given: 80m diameter wind turbine rotating at 20rpm under steady wind conditions at an average wind velocity of 30kph. The eff of the system is 35%.

    Need: Power generated

    Assumptions (made by me):delta PE ~0; mass=constant; operating at Steady Sate; T~constant

    Now, since the eff is = W/Energy and E=delta U +deltaKE +deltaPE this should reduce to:
    Eff=W/deltaKE with my assumptions

    deltaKE=1/2 m (V2^2 - V1^2)
    I know that V2 should be larger than V1 and p2 should be less than p1 but this is where I get stuck, finding V2.
    With T~constant specific enthalpy is 0, and entropy will also be 0......
    How about a hint to get me on the right path?
  2. jcsd
  3. Mar 31, 2005 #2
    This is less about thermodynamics and more about flow.

    Bernoulli's equation gives us the Kinetic Energy per unit volume. From the diameter of the blades we can work out the acceptance area and hence the volume flowing through the turbine per second using the wind velocity.

    Then the maximum power can be found.

    Don't forget the efficieny!!
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