Sustainable energy development technique of vertical axis wind turbine with variable swept area - An experimental investigation

The vertical axis wind turbine is one of the most attractive propulsion systems for sustainable energy generation around the globe. The performance of a vertical axis wind turbine is greatly dependent on wind speed, blade set angle and more importantly the rotational speed. The effective utilization of wind speed and rotational speed on power generation would be enhanced by the improvement of energy capturing capability. Therefore, an attempt has been made to develop the vertical axis wind turbine with a variable swept area of blades to enhance the torque and power output over a wide range of rotational speeds and set angles. In the first phase, the wind turbine is designed with flexibility in blade set angles through modification on the swept area and the developed wind turbine has been subjected to various wind speeds and rotational speeds in a wind tunnel. The experimental results revealed that the torque and power are increased with an increase in wind speed and rotational speeds under blade set angle of 30 degrees to 120 degrees. The peak torque and power have been attained at the average speed of the turbine and it has been eventually increased for a higher blade set angle. For constant set angle, the performance characteristics are also improved due to the enhancement in energy capturing ability of wind turbine at the variable swept area. Furthermore, torque and power coefficient are evident in a similar pattern at all wind speeds and rotational speeds under different tip speed ratios. The maximum torque coefficient would be around 0.3 for the tip speed ratio of 0.2-0.3 and the attainment of the peak value of power and torque coefficient has been shifted towards higher speed due to the improvement in blade dimensions. Thus, it is revealed that the vertical axis wind turbine with enhanced swept blade area would be an attractive propulsion system for sustainable energy generation.