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Horizontal and Vertical Axis Wind Turbines: Comparisons in Design and Application

Horizontal and Vertical Axis Wind Turbines: Comparisons in Design and Application. Term Paper Presentation. Robert Ty. Outline. Introduction General Aspects of Wind Turbines History Basis of Power Generation VAWT Design Studies HAWT Design Studies Pros and Cons of Each Design Conclusion.

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Horizontal and Vertical Axis Wind Turbines: Comparisons in Design and Application

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  1. Horizontal and Vertical Axis Wind Turbines:Comparisons in Design and Application Term Paper Presentation Robert Ty

  2. Outline • Introduction • General Aspects of Wind Turbines • History • Basis of Power Generation • VAWT Design Studies • HAWT Design Studies • Pros and Cons of Each Design • Conclusion

  3. Introduction • Wind power is the generation of useful energy (usually electricity) from wind energy • Represents an alternative to fossil fuel combustion as a source of energy • In 2001, energy needs of 20 million people were met by global wind power, and estimated to grow to 200 million people by 2020

  4. Introduction (2) [Alihan et al., 2009]

  5. Wind Power History • 5000 years ago: Sails for boating vessels in Egypt • 900 AD: Windmills, rotating about a vertical axis, used to grind grain and pump water in Persia (Iran) • Middle Ages: Development of horizontal axis windmills in Europe

  6. Wind Power History (2) • 1882: First wind turbine used to generate electricity, developed by Charles Brush • 1920’s: 3-bladed turbine produced by Marcellus Jacobs, which has become the standard design of most wind turbines today

  7. Wind Power History (3) [Charles F. Brush – Wikipedia, Accessed 02/03/2010] [Jacobs Wind Generator Systems, Accessed 07/03/2010]

  8. Wind Power History (4) • 1922: Savonius rotor VAWT, invented by S. J. Savonius • 1931: Darrieus rotor VAWT, invented by Georges Darrieus [Eriksson et al., 2008]

  9. Basis of Power Generation • Wind turbines convert the kinetic energy in wind into electric potential energy • P = power (W) • ρ = air density (kg m-3) • A = swept rotor area (m2) • C = wind speed (m s-1) P = 0.5×ρ×A×C3 [Alihan et al., 2009]

  10. Basis of Power Generation (2) • Theoretical limit of power capture from wind is 59.3% (Betz Limit) • Inefficiencies due to friction and other losses further reduce the power captured • Coefficient of Performance (Cp) incorporated to reflect the energy captured by the wind turbine P = 0.5×Cp×ρ×A×C3

  11. VAWT #1: Savonius Rotor • Savonius Rotor • Two or three ‘scoop’ blades attached to a vertical shaft • Drag force responsible for blade rotation [Islam et al., 2008]

  12. VAWT #1: Savonius Rotor (2) • Kamoji et al., 2009 • Improve Cp in Savonius rotors by optimizing overlap ratio (m/D), aspect ratio (H/D), blade arc angle (ψ) and blade shape factor (p/q) [Kamoji et al., 2009]

  13. VAWT #1: Savonius Rotor (3) • Tip Speed Ratio (TSR or λ) is the ratio of the speed of the blade’s tip to the speed of incoming wind = ωD/2U [Kamoji et al., 2009]

  14. VAWT #1: Savonius Rotor (4) [Kamoji et al., 2009]

  15. VAWT #1: Savonius Rotor (5) • Simple Savonius Rotors have low torque at certain rotor angles, causing rotor to not start • Introduction of helical structure can reduce this effect, but efficiency is reduced [Kamoji et al., 2009] [Kamoji et al., 2009b]

  16. VAWT #2: Savonius-Darrieus Rotor • Darrieus Rotor • Curved blades forming an egg-beater shape • Lift force responsible for blade rotation • Suffers from low starting torque • Can attach Savonius blades to improve torque [Islam et al., 2008]

  17. VAWT #2: Savonius-Darrieus Rotor (2) • Gupta et al., 2008 • Improve Cp in Savonius rotors by combining with a Darrieus rotor • Overlap ratio in Savonius component varied to determine highest Cp [Gupta et al., 2008]

  18. VAWT #2: Savonius-Darrieus Rotor (3) Savonius rotor, overlap ratio of zero Savonius-Darrieus rotor, overlap ratio of zero [Gupta et al., 2008]

  19. VAWT #2: Savonius-Darrieus Rotor (4) • Overlap ratio of zero produces the highest Cp for the Savonius-Darrieus combination • Higher efficiencies than pure Savonius • Higher starting torque than pure Darrieus [Gupta et al., 2008]

  20. HAWT #1: Mie Vanes • Horizontal axis wind turbine • Generally two or three blades • Most common turbine design • Lift force responsible for blade rotation [Basic Aerodynamic Operating Principles of Wind Turbines, Accessed 05/03/2010]

  21. HAWT #1: Mie Vanes (2) • Shimizu et al., 2003 • Attach Mie vanes to the blade tips to improve Cp • Determine the effect of number of blades, blade aspect ratio and presence of Mie vanes on Cp [Shimizu et al., 2003]

  22. HAWT #1: Mie Vanes (3) • Three-bladed rotor produced a marginally higher maximum Cp, but was smaller at higher λ values • Addition of Mie vanes to a two-bladed rotor increases Cp by 8.75% [Shimizu et al., 2003]

  23. HAWT #1: Mie Vanes (4) • Aspect Ratio: (blade length)2/(blade area) • Mie vanes more effective at lower AR’s [Shimizu et al., 2003]

  24. HAWT #2: Double-Pitch • Lanzafame and Messina, 2009 • Numerical study to improve upon the design of a HAWT blade • Two current designs • Non-twisted • Twisted [Lanzafame and Messina, 2009]

  25. HAWT #2: Double-Pitch (2) • New blade design proposed: two subdivisions in blade • Root section: 12.8° pitch angle • Tip section: 3.8° pitch angle • Sections connected by a winglet [Lanzafame and Messina, 2009]

  26. HAWT #2: Double-Pitch (3) • Simulated data vs. past experimental data of the twisted blade design shows a good fit [Lanzafame and Messina, 2009]

  27. HAWT #2: Double-Pitch (4) • Simulated results of new blade design shows that it generally performs better than the non-twisted model, but worse than the twisted model • Experimental tests have not been done to validate results [Lanzafame and Messina, 2009]

  28. Advantages of VAWT’s/HAWT’s • VAWT’s • Omni-directional • Easier installation and maintenance (components can be built closer to ground) • Simpler safety features • Small VAWT’s suitable for urban areas • Less noise pollution • Lower risk to birds and bats

  29. Advantages of VAWT’s/HAWT’s (2) • HAWT’s • Produce more energy (blades can access high-altitude winds) • Generally have greater power efficiencies (0.40 to 0.50) • Can be built offshore (does not use guy wires) • Well-known design: Lower cost of production

  30. Conclusions • Wind power has been a useful source of energy for thousands years • Efforts have been made to improve turbine power efficiency • VAWT: Optimization of Savonius and Savonius-Darrieus rotors • HAWT: Mie vanes and Double-pitch blades • HAWT/VAWT designs may be suitable for different size scales and applications

  31. End • References • Ahilan, T., Mohammed, K. P., and Arumugham, S. (2009). "A critical review of global wind power generation." American Journal of Applied Sciences, 6(2), 204-213. • Charles F. Brush. <http://en.wikipedia.org/wiki/Charles_F._Brush> Accessed 02/03/2010. • Eriksson, S., Bernhoff, H., and Leijon, M. (2008). "Evaluation of different turbine concepts for wind power." Renewable and Sustainable Energy Reviews, 12(5), 1419-1434. • Gupta, R., Biswas, A., and Sharma, K. K. (2008). "Comparative study of a three-bucket Savonius rotor with a combined three-bucket Savonius-three-bladed Darrieus rotor." Renewable Energy, 33(9), 1974-1981. • Islam, M., Ting, D. S. K., and Fartaj, A. (2008). "Aerodynamic models for Darrieus-type straight-bladed vertical axis wind turbines." Renewable and Sustainable Energy Reviews, 12(4), 1087-1109. • Jacobs Wind Generator Systems. <http://www.wincharger.com/jacobs/index.htm> Accessed 07/03/2010. • Kamoji, M. A., Kedare, S. B., and Prabhu, S. V. (2009). "Experimental investigations on single stage modified Savonius rotor." Applied Energy, 86(7-8), 1064-1073. • Kamoji, M. A., Kedare, S. B., and Prabhu, S. V. (2009b). "Performance tests on helical Savonius rotors." Renewable Energy, 34(3), 521-529. • Lanzafame, R., and Messina, M. (2009). "Design and performance of a double-pitch wind turbine with non-twisted blades." Renewable Energy, 34(5), 1413-1420. • Shimizu, Y., Ismaili, E., Kamada, Y., and Maeda, T. (2003). "Rotor configuration effects on the performance of a HAWT with tip-mounted Mie-type vanes." Journal of Solar Energy Engineering, Transactions of the ASME, 125(4), 441-447.

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