DESIGN, ANALYSIS, AND PROTOTYPING OF VERTICAL AXIS WIND TURBINE FOR ENERGY HARVESTING

Abstract

Among renewable energy sources, wind energy is considered an efficient, cost-effective, and accessible source of energy. Wind energy can be converted into electricity using wind turbines. This research aims to enhance the aerodynamic performance parameters of a vertical axis wind turbine (VAWT) by design modification. The power coefficient (Cp) of existing Savonius turbines is lower compared to that of other types of VAWTs, however, they have a good self-starting capability. On the contrary, Darrieus turbines with fixed blade-type have starting problems specifically at low wind speeds. Furthermore, the wind turbine designed with a cambered airfoil has a better self-starting capability than a symmetric airfoil and more Cp as compared to the Savonius turbine. To address the shortcomings of existing wind turbines, an engineering solution was sought in the design of an innovative hybrid VAWT. The advantages of both lift-based (Darrieus) and drag-based (Savonius) VAWT were combined, and a Double-Darrieus hybrid VAWT was investigated in this research. Computational and experimental analyses of an innovative configuration were carried out. Design parameters such as chord length, number of blades, distance of blades from the central rotating shaft, pitch angle, and rotor height were optimized using the design of experiments. Computational analysis was performed using ANSYS Fluent software, and various datasets were employed in the design of experiments to determine the optimal configurations. A quadratic equation based on a regression model was established and response surface methodology was applied to determine the accuracy of the model by analysis of variance, goodness of fit, investigation of residuals, and 𝑅-squared values. The optimized chord length, number of blades, pitch angle, distance of blades from the central rotating shaft, and rotor height of the inner turbine were 0.547 m, 3, -3.410, 0.789 m, and 1.605 m, respectively. The adoption of cambered airfoils for the inner turbine in a hybrid system gives an improved Cp of 0.491 at a tip speed ratio of 3 as compared to a standard Darrieus rotor (0.4-0.45). The positive static torque coefficient at all azimuth angles indicates that the innovative hybrid wind turbine is completely self-starting. The maximum value of the static torque coefficient for the proposed configuration was 0.317 for a wind speed of 7.5 m/sec as compared to 0.251 for the standard Darrieus turbine. The self-starting speed of the innovative hybrid VAWT is as low as 2.81 m/sec with a rated power of 1.522 kW at a wind speed of 7.5 m/sec. To validate the computational results, a scaled-down model was developed by applying the theory of similarity. Experimental testing