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Aerodynamics 1: Energy Conversion

Aerodynamics 1: Energy Conversion. References: NREL (Pat Moriarty, Tony Jimenez). Wind Turbine Components. Courtesy: Alternative Energy Institute. Energy and Power. Energy is the ability to do work Energy = Force * Distance Electrical energy usually measured in kWh Power = Energy / Time

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Aerodynamics 1: Energy Conversion

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  1. Aerodynamics 1: Energy Conversion References: NREL (Pat Moriarty, Tony Jimenez)

  2. Wind Turbine Components Courtesy: Alternative Energy Institute Wind Energy

  3. Wind Energy

  4. Energy and Power • Energy is the ability to do work • Energy = Force * Distance • Electrical energy usually measured in kWh • Power = Energy / Time • Electrical power usually measured in kW Wind Energy

  5. Kinetic Energy • Kinetic energy (KE) is the energy of motion • Air molecules have mass, and wind is moving air. Thus, wind has kinetic energy. • Wind turbines convert the wind’s kinetic energy into mechanical kinetic energy (spinning the rotor). • Mass = density * volume: • What is the kinetic energy of a 1m cube of air moving at 5 m/s in Colorado (r = 1 kg/m3)? Wind Energy

  6. Energy Conservation and Energy Conversion • When the turbine extracts kinetic energy from the wind, the speed of the wind is reduced. • Some of the wind’s kinetic energy is converted into mechanical kinetic energy, i.e., the rotation of the turbine rotor. • Some of the wind’s kinetic energy remains in the wind (conservation of energy). • What would happen if all of the wind’s kinetic energy were converted? Wind Energy

  7. Power • Power available in the wind • r = air density • v = wind speed • A = cross sectional area swept by rotor (“swept area”) Wind Energy

  8. Energy and Power – II • Consider the units of the kinetic energy equation:and the units of the power equation: • Recall: Power = (Energy) / (Time) and Mass = (Density)*(Volume) Wind Energy

  9. Power Coefficient • Power coefficient Cp is a measure of the aerodynamic efficiency of the wind turbine • Q = turbine’s aerodynamic torque • W = rotor rotational speed • Betz limit - theoretical maximum Wind Energy

  10. Tip-Speed Ratio • Ratio of the linear speed of the tip of the blade to the wind speed • Linear speed of a rotating object is angular speed times distance from center of rotation • l = tip-speed ratio • R = rotor radius • w = angular speed • v = wind speed • What is the tip-speed ratio of a 20 m diameter rotor rotating at 6 rad/s in 10 m/s wind? Wind Energy

  11. Cp for Various Configurations Wind Energy

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