Study on the aerodynamic brake of small gyro-mill type vertical axis wind turbine: 1st report, method of the rotational speed continuous control under the strong wind

The vertical axis wind turbine can correspond to the wind direction change in principle and is possible to increase the output by stack it up vertically. However, it is pointed out that the control is difficult, because the self-start is weak and the rotational speed rises rapidly. In this study, we report on the method by which the generating operation can be continued at ease when the wind of the mean speed from 12m/s to 15m/s blows to the small giro-mill type vertical axis wind turbine and under the situation with large wind speed fluctuation in the vicinity of ground. In this method, firstly, the slide shaft is installed squarely to the rotation axis of the vertical axis wind turbine. The flat plate wing in the tip of this slide shaft is parallel to the plane of rotation under a usual rotational speed, and the axial resistance torque is small. However, the flat plate wing begins to tilt when the rotational speed exceeds a certain value, and it becomes finally right-angled to the plane of rotation, and large axial resistance torque is generated. By this method, the runaway of the vertical axis wind turbine is prevented. In the paper, various problems on this are clarified and are verified through the wind tunnel experiment, and the practicable method has been clarified.