AbstractContinuous depletion in the fossil fuel reserve coupled with ever-increasing energy demands has led researchers to study and develop renewable sources of energy. Wind energy being one of the cheapest and easily available forms of energy, has been able to bag significant interest from a plethora of researchers working globally in recent times. Over the years, various forms of wind turbines have been developed with an aim to maximize the energy harvesting efficiency. Broadly, wind turbines are classified based on the axis of rotation namely: horizontal axis wind turbine (HAWTs) and vertical axis wind turbines (VAWTs). VAWTs are known for their low operating and maintenance cost, easy installation, and insensitivity to the direction of wind flow. These qualities have led to their applications in decentralized electricity grids. However, VAWTs are characterized as low-efficiency energy convertors. In this study, Savonius-style wind turbines (VAWT) are studied experimentally with an aim to improve their efficiency. Rotation of Savonius-style wind turbines are caused mainly due to the drag forces applied to the concave (advancing blade) and convex (returning blade) rotor profiles. Additionally, the lift forces contribute to the rotation of the blades about the vertical axis. The presence of a large negative torque generated on the returning blade of these types of VAWTs acts as a resistance to the motion of the rotors. Consequently, this decreases their power generation ability.Savonius-style wind turbines are mainly gauged by two types of coefficients, namely: (i) coefficient of power (CP) and (ii) coefficient of torques (CT). The coefficient of power is defined as the ratio of power generated by the turbine to the total power available to the turbine from the free-flowing wind. This is synonymous to the operational efficiency of the wind turbine. The coefficient of torque reflects the torque generating ability of the turbine. In this study, experiments have been performed using three different types of rotor profiles for Savonius-style wind turbines namely: classical profile, Benesh profile and semi-elliptical profiles which have been studied by oriented jets. Using deflector plates the orientation of jets has been varied from 10 to 70 degrees. The addition of deflector plates to the wind turbines assists in maximizing the utilization of wind energy. Experiments have also been performed in the laminar air flow. Mechanical loads have been used to study CP and CT as functions of tip speed ratio (TSRs) for various values of wind velocities. The velocity of the wind has been adjusted by varying the rheostat that controls the AC motor for the wind tunnel systems. Experimental results indicated that optimum performance could be achieved from all the three types of Savonius-style wind turbine variants at TSR = 0.70. Out of the three designs investigated in this study, the semi-elliptic design yielded the best coefficient of performance equaling to 0.42 at TSR = 0.70.Keywords: Savinous-style wind turbine, vertical axis wind turbine, semi-elliptic design, wind energy, coefficient of performance

Experimental Investigation of Performance Characteristics for Savonius-Style VAWTs: A Comparative Study

Paper Proceedings: https://asmedigitalcollection.asme.org/GTINDIA/GTINDIA2021/volume/85536

ASME 2021 Gas Turbine India Conference (GTINDIA2021)

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