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Me116 Project Wind Energy


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Heat Transfer Presentation on Wind Energy

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Me116 Project Wind Energy

  1. 1. Wind Energy Group Leader: Matthew Gross Team Members: Eli Brewer, Rafael Chavez, Vicki Chen, Jason McMillan, and Daniel Norris 116A: Heat Transfer Spring 2011 Group 9
  2. 2. History of Wind Power 5000B.C. 500B.C. 1000A.D. 1850 A.D. Today Future
  3. 3. Percent of Total Energy From Wind Energy
  4. 4. Positive Aspects <ul><ul><li>Renewable energy </li></ul></ul><ul><ul><li>Clean energy </li></ul></ul><ul><ul><li>Simplicity of technology required: developing countries </li></ul></ul><ul><ul><li>Inexpensive alternative energy: 4-6 cents/kWh </li></ul></ul><ul><ul><li>Concurrent land usage  </li></ul></ul><ul><ul><li>Offshore locations </li></ul></ul>
  5. 5. Negative/Limiting Aspects <ul><ul><li>Functions 1/3 of the time </li></ul></ul><ul><ul><li>Unpredictable wind strength </li></ul></ul><ul><ul><ul><li>land features, surface roughness, obstacles </li></ul></ul></ul><ul><ul><li>Limited operation </li></ul></ul><ul><ul><ul><li>8-55 mph </li></ul></ul></ul><ul><ul><li>Limited by Betz law (60%) </li></ul></ul><ul><ul><li>Capital costs </li></ul></ul><ul><ul><ul><li>  $1000 /kW </li></ul></ul></ul><ul><ul><ul><li>high transmission costs </li></ul></ul></ul><ul><ul><li>Environmental concerns </li></ul></ul><ul><ul><ul><li>disruption of wildlife </li></ul></ul></ul><ul><ul><ul><li>noise pollution </li></ul></ul></ul>
  6. 6. Extracting Energy from the Wind <ul><ul><li>Kinetic energy of airflow : </li></ul></ul><ul><li>KE=½ρv 3 A </li></ul><ul><ul><li>Power extracted: </li></ul></ul><ul><li>P = ½*m’(v 1 2 -v 2 2 ) </li></ul><ul><ul><li>Normalized Coefficient of Power: </li></ul></ul><ul><li>Cp = ½{[1-(v 2 /v 1 ) 2 ](1+v 2 /v 1 )} </li></ul><ul><ul><li>Theoretical limit of the power extracted from the wind: </li></ul></ul><ul><li>59.3% ≈ 1/3 </li></ul><ul><li>Betz Law </li></ul>
  7. 7. Utilizing Drag Force & Lift Force <ul><ul><li>Vertical rotor uses drag force </li></ul></ul><ul><ul><li>Tip speed ratio: </li></ul></ul><ul><li>λ = u/v </li></ul><ul><ul><li>Energy captured: </li></ul></ul><ul><li>P = λ[C D1 (1- λ) 2 -C D2 (1+ λ) 2 ] </li></ul><ul><ul><li>Theoretical Limit: </li></ul></ul><ul><li>16% ≈ 1/6 </li></ul><ul><ul><li>Horizontal rotor uses lift force </li></ul></ul><ul><ul><li>Power extracted depends on lift to drag ratios (typically 400), tip speed ratio, rotor profile, and angle of attack </li></ul></ul>
  8. 8. Bearing and Gearbox Failures <ul><ul><li>Main Bearing must support the weight of the blade and hub assembly: 48,000 lbs. in a 1.5 MW turbine </li></ul></ul><ul><ul><li>The gearbox is the primary cause of turbine failure.   </li></ul></ul><ul><ul><li>Overheating is the second leading cause of bearing failure. </li></ul></ul>
  9. 9. Combating Heat Buildup <ul><ul><li>Gearbox and main bearing housings dissipate heat at the same rate it generates using convection. </li></ul></ul><ul><ul><li>Induction heaters on bearings help maintain even heat distribution </li></ul></ul><ul><ul><li>Heat exchangers lower the lubricant temperature within the gearbox </li></ul></ul>
  10. 10. Potential for Improvement <ul><ul><li>Problem: </li></ul></ul><ul><ul><li>Intermittent Wind Speed </li></ul></ul><ul><ul><ul><li>Variable Output </li></ul></ul></ul><ul><ul><ul><li>Gearboxes Failure </li></ul></ul></ul><ul><ul><li>Solution: </li></ul></ul><ul><ul><ul><li>  Energy Storage </li></ul></ul></ul><ul><ul><ul><ul><li>Electrical </li></ul></ul></ul></ul><ul><ul><ul><ul><li>CAES with biomass </li></ul></ul></ul></ul><ul><ul><ul><ul><li>PAC </li></ul></ul></ul></ul><ul><ul><ul><li>Stabilized Output  </li></ul></ul></ul>
  11. 11. Improving Turbine Technology <ul><ul><li>Problem: </li></ul></ul><ul><ul><li>Low Output </li></ul></ul><ul><ul><li>Large Turbine Bearing Stress </li></ul></ul><ul><ul><li>Solution: </li></ul></ul><ul><ul><ul><li>Larger Turbines </li></ul></ul></ul><ul><ul><ul><li>Taller Towers </li></ul></ul></ul>
  12. 12. Conclusion <ul><ul><li>Renewable resource </li></ul></ul><ul><ul><li>Highly dependent on location </li></ul></ul><ul><ul><li>Intermittent resource, concern with system reliability, failure due to cyclic loading on the blades </li></ul></ul><ul><ul><li>Current research is focused on finding simpler, lighter, more efficient systems with larger rotors, taller towers, and energy storage </li></ul></ul><ul><ul><li>Future designs will depend on economic, market, and certification factors as well as technical ones </li></ul></ul>