![REFERENCES
24-08-2022 25
Department of Mechanical Engineering
[1] Wang Z, Wang Y, Zhuang M. Improvement of the aerodynamic performance
of vertical axis wind turbines with leading-edge serrations and helical blades
using CFD and Taguchi method. Energy Convers Manage 2018;177:107–21.
[2] Saeidi D, Sedaghat A, Alamdari P, Alemrajabi AA. Aerodynamic design and
economical evaluation of site specific small vertical axis wind turbines.
Appl Energy 2013;101:765–75.
[3] Kumar R, Raahemifar K, Fung AS. A critical review of vertical axis wind
turbines for urban applications. Renew Sustain Energy Rev 2018;89:281–91.
[4] J. Chen, L. Chen, H. Xu, H. Yang, C. Ye, D. Liu, Performance improvement
of a vertical axis wind turbine by comprehensive assessment of an airfoil
family, Energy 114 (2016) 318e331.
[5] A. Betz. Das Maximum der theoretisch möglichen Ausnützung des Windes
durch Windmotoren. 1920.](https://image.slidesharecdn.com/shivalingtsvawt-220824063726-ed9c2389/85/Technical-Seminar-on-Vertical-Axis-Wind-Turbines-25-320.jpg)
Technical Seminar on Vertical Axis Wind Turbines
- 1. VISVESWARAYA TECHNOLOGICAL UNIVERSITY BRINDAVAN COLLEGE OF ENGINEERING Dwarakanagar, Yelahanka, Bengaluru-63 TECHNICAL SEMINAR Presentation on “VERTICAL AXIS WIND TURBINES” Presented by Name: SHIVALING USN: 1BO18ME020 Under the Guidance of Dr. R VARA PRASAD KAVITI HOD, Professor Dept of Mechanical Engineering Brce,Bengaluru DEPARTMENT OF MECHANICAL ENGINEERING
- 2. CONTENTS ⚫ INTRODUCTION ⚫ LITERATURE REVIEW ⚫ OBJECTIVES ⚫ METHODOLOGY ⚫ TYPES OF VAWT ⚫ PRINCIPLES AND AERODYNAMICS ⚫ BETZ’S LAW ⚫ CURRENT SCENARIO ⚫ CONCLUSION ⚫ REFERENCE 24-08-2022 2 CONTENTS Department of Mechanical Engineering
- 3. INTRODUCTION 24-08-2022 3 Department of Mechanical Engineering • A wind turbine is a device that converts the kinetic energy of wind into electrical energy. They are an increasingly important source of intermittent renewable energy, and are used in many countries to lower energy costs and reduce reliance on fossil fuels. • There are two major types of wind turbine determined based on the axis in which the turbine rotates. Horizontal Axis Wind Turbine (HAWT) Vertical Axis Wind Turbine (VAWT) Fig.: World’s tallest VAWT, in Cap-Chat, Quebec
- 4. VERTICALAXIS WIND TURBINE A vertical-axis wind turbine (VAWT) is a type of wind turbine where the main rotor shaft is set transverse to the wind while the main components are located at the base of the turbine. A vertical axis wind turbine has its axis perpendicular to the wind streamlines and vertical to the ground. A more general term that includes this option is "transverse axis wind turbine" or "cross-flow wind turbine.“ Computer modelling suggests that wind farms constructed using vertical-axis wind turbines are 15% more efficient than conventional horizontal axis wind turbines as they generate less turbulence. 24-08-2022 Department of Mechanical Engineering 4
- 5. 24-08-2022 Department of Mechanical Engineering 5 Fig. 2: VAWT Fig. 2: HAWT
- 6. LITERATURE REVIEW 24-08-2022 6 Department of Mechanical Engineering Sl. No. Authors Contributions Publication 1. Joachim Toftegaard Hansen, Mahak Mehak, Iakovos Tzanakis Numerical modelling and optimization of vertical axis wind turbine pairs Renewable Energy Int. Journal, 2021 2. Zhenzhou Zhao, Dingding Wang, Tongguang Wang, Ming Chen Approaches for aerodynamic performance improvement of lift- type vertical axis wind turbine Sustainable Energy Technologies and Assessments, 2022 3. F Th¨onnißen, M Marnett, B Roidl, W Schr¨oder A numerical analysis to evaluate Betz's Law for vertical axis wind turbines Journal of Physics, 2016
- 7. OBJECTIVES 24-08-2022 7 Department of Mechanical Engineering To study the requirement of Vertical Axis Wind Turbines (VAWT). To study the reliability of VAWT. To produce electrical energy at lower wind speeds. Reduce reliance on fossil fuels at residential purposes.
- 8. METHODOLOGY 24-08-2022 8 Department of Mechanical Engineering Start Literature Review Types of VAWT Principles of Working Comparative Results End
- 9. COMPONENTS OF VAWT 24-08-2022 Department of Mechanical Engineering 9 The construction of a typical Vertical Axis Wind Turbine includes the following components: • Blades • Rotor (shaft) • Lower Hub • Lower Bearing • Power and Control Unit • Generator and Transformer • Equipment Station • Support Stand Fig. 4: Components of VAWT
- 10. TYPES OF VAWT Vertical Axis Wind Turbines are classified into two major categories: Drag Types (Savonious) VAW Turbines. Lift Type (Darrieus) VAW Turbines. 24-08-2022 Department of Mechanical Engineering 10 Fig. 5: Lift Type VAWT Fig. 5: Drag Type VAWT
- 11. All VAWTs have the same fundamental physical principle. The blade rotates in the counter-clockwise direction, and the resultant velocity W is formed due to the incoming velocity V∞ and the tangential velocity U. The resultant velocity is expressed by: 𝑊 = 𝑈 + 𝑉∞ 24-08-2022 Department of Mechanical Engineering 11 PRINCIPLES AND AERODYNAMICS Fig. 6: Velocity and Force Vectors of VAWT The angle between the resultant velocity and the chord is defined as the angle of attack (AoA).
- 12. The resultant velocity and AoA dictate the forces acting on the blade, namely lift, drag, and their normal and tangential components. The blade is positive in the upstream half-cycle and negative in the downstream half-cycle. 24-08-2022 Department of Mechanical Engineering 12 Fig. 7: Velocity Vectors at different azimuth angles
- 13. SAVONIUS WIND TURBINES The Savonius Turbine is an extremely simple vertical axis turbine that works entirely because of thrust force of wind. The turbine consists of a number of aero foils, usually - but not always - vertically mounted on a rotating shaft or framework, either ground stationed or tethered in airborne systems. Aerodynamically, it is a drag-type turbine, consisting of two or three scoops. 24-08-2022 Department of Mechanical Engineering 13 Fig. 8: Savonius Wind Turbine
- 14. Looking down on the rotor from above, a two-scoop machine might resemble the letter "S" in cross section. Because of the curvature, the scoops experience less drag when moving against the wind than when moving with the wind. The differential drag causes the Savonius turbine to spin. Because they are drag-type devices, Savonius turbines extract much less of the wind's power than other similarly-sized lift- type turbines. Savonius turbines are used whenever cost or reliability is much more important than efficiency. 24-08-2022 Department of Mechanical Engineering 14 Fig. 9: Anemometers and Buoys
- 15. 24-08-2022 Department of Mechanical Engineering 15 The turbine consists of a number of curved aero foil blades mounted on a rotating shaft or framework. Two or more flexible blades are attached to the shaft. The blades bow outward, taking approximately the shape of a parabola, and are of symmetrical aero foil section. Aerodynamically, it is a lift – type turbine. DARRIEUS WIND TURBINES Fig. 10: Darrieus Wind Turbines
- 16. 24-08-2022 Department of Mechanical Engineering 16 At first sight it appears that the forces on the blades at the two sides of shaft should be same, producing no torque. In fact, the torque is zero when the rotor is stationary. It develops a positive torque only when it is already rotating. This means that such a rotor has no starting torque and has to be started using some external means. Fig. 11: Working of Darrieus Turbine
- 17. Betz's law indicates the maximum power that can be extracted from the wind, independent of the design of a wind turbine in open flow. The law is derived from the principles of conservation of mass and momentum of the air stream flowing through an idealized "actuator disk" that extracts energy from the wind stream. According to Betz's law, no turbine can capture more than 16/27 (59.3%) of the kinetic energy in wind. The factor 16/27 (0.593) is known as Betz's coefficient. 24-08-2022 Department of Mechanical Engineering 17 BETZ’s LAW
- 18. The Betz limit is based on an open-disk actuator. Betz’s Law and Coefficient of Performance: • The power obtainable from a cylinder of fluid with cross-sectional area S and velocity v1 is • The reference power for the Betz efficiency calculation is the power in a moving fluid in a cylinder with cross-sectional area S and velocity v1 • The "power coefficient“ Cp (= P/Pwind) is dimensionless ratio of the extractable power P to the kinetic power Pwind available in the undistributed stream. • Modern large wind turbines achieve peak values for Cp in the range of 0.45 to 0.50, about 75–85% of the theoretically possible maximum. 24-08-2022 Department of Mechanical Engineering 18
- 19. ADVANTAGES & DISADVANTAGES Advantages: • Omni-directional VAWTs may not need to track the wind. No need of complex mechanism and additional components to yaw the rotor and pitch the blades. • Strong Supporting tower is not needed as in the case of HAWT, because the complicated components are placed at ground/sea level. • Simple Blade geometry. • Low production cost as compared to HAWT. • Low cost of installation and maintenance. • Low risk foe humans and birds because blades move at relatively slow speeds. • Suitable for Urban, residential areas where wind speed is low and reliability can be more. 24-08-2022 Department of Mechanical Engineering 19
- 20. Disadvantages • Less efficient as compared to HAWT, This is mainly due to the nature of their design and operational characteristics. • On average, the efficiency of a horizontal axis wind turbine lays between 40 to 50 %, On the other hand, a Savonius vertical axis wind turbine has an average efficiency of 10 to 17 %, while the Darrieus vertical axis wind turbine reaches 30 to 40 %. • Components wear down as VAWT’s face more turbulences and vibrations, can result in more maintenance cost. • Some VAWT’s rely on additional starting mechanism. • VAWTs often suffer from dynamic stall of the blades as the angle of attack varies rapidly. 24-08-2022 Department of Mechanical Engineering 20
- 21. CURRENT SCENERAIO • Vertical-Axis Wind Turbines Work Well Together – Tzanakis and Hansen ran some 11,500 hours of computer simulations of 30-odd configurations of vertical turbines. – They found that the optimal arrangement of vertical-axis turbines turns out to be having turbines three diameters from each other, offset by 60 degrees. – This setup increased the turbines’ efficiency by 15 percent. It also meant that the turbines could be more tightly grouped in a much smaller farm than horizontal turbines would allow. 24-08-2022 Department of Mechanical Engineering 21 Fig. 12: 30 VAWT simulations
- 22. • IYSERT partnered with Government of India for Smart City Project – They have produced Variety of VAWT for public areas and rooftops applications. These models are hybrid Solar and Wind Turbines. 24-08-2022 Department of Mechanical Engineering 22 Fig. 13: Projects by IYSERT
- 23. • Vertical turbines to boost the efficiency of wind farms – New research from Oxford Brookes University has found that vertical turbine design is more efficient than traditional turbines in large-scale wind farms. When set in pairs, vertical turbines increase each other’s performance by up to 15%. 24-08-2022 Department of Mechanical Engineering 23
- 24. CONCLUSIONS 24-08-2022 24 Department of Mechanical Engineering The idea for Vertical Axis Wind Turbines (VAWT) has been blowing around for decades, but despite many advantages the technology has so far attracted little interest. A major benefit of vertical-axis wind turbines (VAWTs) compared with their (upwind) horizontal counterparts (HAWTs) is that they can draw wind from all directions while not needing a yaw system. In addition, VAWT can be built lower, so they are less visible and can withstand much harsher environments and do not need to be shut down when wind speeds exceed 64mph, even the structures are claimed to withstand speeds of up to 110mph.
- 25. REFERENCES 24-08-2022 25 Department of Mechanical Engineering [1] Wang Z, Wang Y, Zhuang M. Improvement of the aerodynamic performance of vertical axis wind turbines with leading-edge serrations and helical blades using CFD and Taguchi method. Energy Convers Manage 2018;177:107–21. [2] Saeidi D, Sedaghat A, Alamdari P, Alemrajabi AA. Aerodynamic design and economical evaluation of site specific small vertical axis wind turbines. Appl Energy 2013;101:765–75. [3] Kumar R, Raahemifar K, Fung AS. A critical review of vertical axis wind turbines for urban applications. Renew Sustain Energy Rev 2018;89:281–91. [4] J. Chen, L. Chen, H. Xu, H. Yang, C. Ye, D. Liu, Performance improvement of a vertical axis wind turbine by comprehensive assessment of an airfoil family, Energy 114 (2016) 318e331. [5] A. Betz. Das Maximum der theoretisch möglichen Ausnützung des Windes durch Windmotoren. 1920.
- 26. Queries ??? 24-08-2022 26 Department of Mechanical Engineering
- 27. 24-08-2022 27 Department of Mechanical Engineering