1 / 26

Wind power Part 3: Technology

Wind power Part 3: Technology. San Jose State University FX Rongère February 2009. Wind Turbine Aerodynamics. Energy balance over the stream tube. Inlet: index 1 Outlet: index 2 Turbine: index T. Betz’s Simplified Approach.

howe
Télécharger la présentation

Wind power Part 3: Technology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wind powerPart 3: Technology San Jose State University FX Rongère February 2009

  2. Wind Turbine Aerodynamics • Energy balance over the stream tube Inlet: index 1 Outlet: index 2 Turbine: index T

  3. Betz’s Simplified Approach • The turbine is perfect: there is no internal entropy generation Then, when air considered as an incompressible fluid:

  4. Betz’s Simplified Approach • Energy balance equation is reduced to: • In addition, we assume that the wind speed stay axial through the turbine: • Balance of Forces: The power of the torque absorb by the turbine is equal to the power taken from the air flow

  5. Betz’s Simplified Approach • Momentum equation on the system: Then: And:

  6. Betz’s Simplified Approach • Introducing a the interference factor: Then:

  7. Betz’s Simplified Approach • The power absorbed by the turbine is maximum if: Betz’s law Then

  8. Other factors • Other factors limit the performance of wind turbines • Wake rotation • Aerodynamic drag • Finite number of blades and interaction between them • Blade tip losses

  9. Wake rotation • In fact, the air is rotating downstream the rotor by reaction to the torque applied to the rotor

  10. Maximum conversion rate with wake rotation: Glauert’s law • To characterize this effect we introduce: • Angular velocity of the rotor : ΩT • Angular velocity imparted to the flow: ω • Angular induction factor: a’ = ω/2ΩT • Axial interference factor: • Blade tip speed : λ = ΩTR/v1 • We can then show that the transfer power is maximum if:

  11. Maximum conversion rate with wake rotation: Glauert’s law • Then the maximum conversion rate is given by the following equation: With a(λ) defined by: Betz’s law corresponds to: and:

  12. Maximum conversion rate with wake rotation: Glauert’s law • By drawing CpMax we can show that: • Larger is the blade tip ratio higher is the conversion rate • For blade tip ratio greater than 4 conversion rate is close to Betz’s law • The optimal axial interference factor is close to 1/3 for large enough blade tip ratio Angular induction factor λ λ

  13. Aerodynamic drag • The aerodynamics of a blade is defined by: L: Lift force v: Wind speed on the blade c: Chord of the blade D: Drag force l: Span of the blade α: Angle of attack

  14. Lift and Drag • Lift and Drag are related: • Lift transfers power • Drag generates losses • Bearings • Viscous Friction • Noise • About 10 -15% of aerodynamic inefficiencies

  15. Design optimization • Blade shape may be optimized using laboratory test and numerical modeling • See: Wind Energy, Explained by J.F. Manwell, J.G. McGowan and A.L.Rogers, John Wiley, 2002, for detailed explanations • See also: Riso DTU – National Laboratory for Renewable Energy http://www.risoe.dtu.dk/

  16. Two Blade Wind Turbine Three Blade Wind Turbine Vertical axis Wind Turbine (Darrieus) Multiblade Wind pump Interaction between blades • Blade tip speed is limited by the interaction between the blades. Typically, if the rotation is too fast (λ>λMax) then the flow for each is perturbed by the previous one λ

  17. Blade tip losses • Local rotating airflow at the tip of the blades due to the difference of pressure between the faces of the blades • Similar to aircraft wings • Thesis at DTU has shown a gain of 1.65% but with an increase in thrust of 0.65% Performance glider with winglets Wingtip loss of Boeing 737 Source: Mads Døssing Vortex Lattice Modelling of Winglets on Wind Turbine Blades Risø-R-1621(EN) Aug. 2007

  18. Actual Wind Turbine Conversion Rate • Example: Liberty of Clipper Windpower Power curve

  19. Actual Turbine Conversion rate • Power curve and Conversion rate

  20. Optimization Parameters Max Power Cut out Cut in Efficiency

  21. Generated Energy • Generated Energy = Wind Speed Distribution x Turbine Power Curve

  22. Capacity Factor • Lower Capacity factor allows higher energy capture • Generally preferred CF is between 30% and 40% Characteristics of the tested turbine

  23. Wind Turbine Optimization

  24. Wind and Power Distribution CF=24% Captured Energy =33%

  25. Wind and Power Distribution vm = 9m/s CF=44% Captured Energy =22%

  26. Companies to follow • GE: www.ge.com • Clipper Windpower: www.clipperwind.com • Vestas: www.vestas.com • Repower: www.repower.com • Gamesa: www.gamesa.com • Suzlon: www.suzlon.com • Mitsubishi: www.mitsubishi.com

More Related