Showing papers on "Savonius wind turbine published in 2010"

Experimental and Numerical Investigations on Aerodynamic Characteristics of Savonius Wind Turbine with Various Overlap Ratios

Abstract: Savonius wind turbine is the simplest type of vertical axis rotor that has a relatively low efficiency. Operation of the Savonius wind turbine is based on the difference of the drag force on its semi-spherical blades, depending on whether the wind is striking the convex or the concave part of the blades. This turbine is being used in various countries around the world due to the simplistic design, cheap technology for construction, and a good starting torque independent of wind direction at low wind speeds. Due to its simple design and low construction cost, this rotor is mainly used for water pumping as well as wind power on small scale. The main goal of this current research is to investigate the aerodynamic performance of Savonius wind turbine. Wind tunnel investigation was carried out to find the aerodynamic characteristics like, drag coefficient, torque coefficient, and power coefficient of three blade Savonius wind turbine rotor models with and without overlap ratio (ratio of overlap distance between two adjacent blades and rotor diameter ,OR = a/D) at various Reynolds numbers. Numerical investigation was also carried out to find those aerodynamic characteristics. For numerical investigation, commercial computational fluid dynamic (CFD) software GAMBIT and FLUENT were used. Afterwards those two results were compared for verification. Three different models with different overlap ratio were designed and i fabricated for the current study to find the effect of overlap ratios. The results from the experimental part of the research show a significant effect of overlap ratio and Reynolds number on the improvement of aerodynamic performance of the Savonius wind turbine. At higher Reynolds number turbine Model without overlap ratio gives better aerodynamic coefficients and at lower Reynolds number Model with moderate overlap ratio gives better results.

Vertical axis wind turbine with continuous blade angle adjustment

Abstract: The author presents a concept for a vertical axis wind turbine that utilizes each blade's entire rotational cycle for power generation. Each blade has its own vertical axis of rotation and is constrained to rotate at the rate of one half of a revolution per full revolution of the rotor. For a rotor of radius r and blades of width b, a technical analysis predicts a theoretical maximum power coefficient of CP = b 2r+b, neglecting wind flow interference by upwind blades. This theoretical power coefficient is generally greater than the efficiency of a typical Savonius wind turbine (CP ~~ 0.15), and it reaches CP = 0.5 at the limiting blade width, b = 2r. The analysis also predicts a static torque and optimal tip-speed ratio that are both greater than those of a Savonius wind turbine with similar blade dimensions. Design considerations for implementing the kinematic constraint and for blade adjustment to account for changes in wind direction are discussed, and the author's prototype is presented. Testing of the prototype demonstrated that implementation of the kinematic constraint is feasible, and that efficiencies greater than those achievable by a Savonius turbine are plausible. In 4 m s wind conditions, the prototype yielded an estimated CP of 0.15, with much room for improvement through design changes and blade optimization in future iterations of this style of turbine.

Savonius wind turbine with curved vane

Abstract: PROBLEM TO BE SOLVED: To provide a structure which increases output without sacrificing the characteristics of a Savonius wind turbine with simple structure, and prevents breakage of the impeller to be caused by overspeed in strong wind. SOLUTION: In a position close to an outer end of a curved vane of the Savonius wind turbine, the vane is curved in an inverted-Z shape or a Z shape so that a portion close to the outer end of the vane is relatively shifted on a wind receiving recessed curved face side. Hence, the strength is increased, and a wind force received by an outer face of a step plate connecting a vane face close to a rotational center with a vane face close to the outer end sandwiching the stepped part therebetween, acts to assist the wind power received by an original recessed curved face. As a result, a rotative force of the Savonius wind turbine is increased to increase the output torque. Although wind flowing around on a recessed curved face side of the other curved vane hits on an inner face of the step plate and acts in a direction pushing back the vane, since the torque is smaller than the assist torque, net torque increase and output increase are achieved. COPYRIGHT: (C)2010,JPO&INPIT

Aerodynamic Performance Analysis of Three Bladed Savonius Wind Turbine with Different Overlap Ratios and at various Reynolds Number

Abstract: Considerable improvements in the aerodynamic performance of a vertical axis wind turbine (VAWT) can be achieved by integrating computational fluid dynamics (CFD) simulation and wind tunnel investigation in their design improvement. With the growing demand for energy worldwide, conventional sources are becoming more scarce and expensive. Wind is among the most popular and fastest growing sources of alternative energy in the world. It is an inexhaustible, indigenous resource, pollution-free, and available almost any time of the day, especially in coastal regions. Industry experts predict that, with proper development, wind energy could provide 20% of the nation’s energy needs. Vertical axis wind turbines (VAWTs) may be as efficient and practical as, and simpler, and significantly cheaper to build and maintain than, horizontal axis wind turbines (HAWTs). They have other inherent advantages; for example, they always face the wind. VAWTs include both a drag-type configuration, such as the Savonius rotor, and a lift-type configuration, such as the Darrieus rotor. The Savonius wind turbine is the simplest. Its operation depends on the difference in drag force when the wind strikes either the convex or concave part of its semi-cylindrical blades. It is good at self-starting and works independently of wind direction. However, its efficiency is relatively lower than that of the lift-type VAWTs. Due to its simple design and low construction cost, Savonius rotors are primarily used for water pumping and to generate wind power on a small scale and its large starting torque makes it suitable for starting other types of wind turbines that have inferior starting characteristics. Recently, some generators with high torque at low rotational speed, suitable for small-scale wind turbines, have been developed, suggesting that Savonius rotors may yet be used to generate electric power. The main goal of this research work is to improve the aerodynamic performance of the three bladed vertical axis Savonius wind turbine. Based on this goal, the objective of this project is to study the performance characteristics of the Savonius wind turbine scale models both experimentally and numerically. The turbine scale models will have different designs with different overlap ratios (ratio of gap between two adjacent blades and the rotor diameter) and without overlap within three blades. The experimental measurements and testing will be conducted in front of a low speed subsonic wind tunnel at different Reynolds number and the computational fluid dynamic (CFD) flow simulation around those design models will be performed by commercial CFD software FLUENT and GAMBIT.Copyright © 2010 by ASME