The reduction in low-frequency noise of horizontal-axis wind turbines by adjusting blade cone angle.

In the present paper, the effect of blade cone angle on low-frequency noise of horizontal-axis wind turbines is studied to investigate the noise reduction, by adjusting the blade cone angle in different wind speeds. In wind turbines, a significant part of the noise is in infrasound range to which exposure could have adverse effects on human health. In this study, a small turbine is selected as a test case, and the sound field is simulated for different blade cone angles from 0^° to 10^° with a wind speed range between 5 and 25 m/s. The results of flow simulation show that the change in the output power is < 5% in comparison with the planar turbine. In addition, the calculated results for the low-frequency noise demonstrate that the blade cone angle significantly affects the noise value and the directivity pattern. The investigation of the directivity pattern shows that blade cone angle could have opposite effects on different observer positions, and therefore, the noise calculation at only one position is not enough to conclude about the effect of blade cone angle. The obtained directivity also shows that the turbines with blade cone angles of 2.5^° and 5^° are preferred in order to reduce the maximum noise, in comparison with the planar turbine. Overall, it is concluded that the adjustment of blade cone angle in different wind speeds can be an effective solution for reducing the low-frequency noise. [ABSTRACT FROM AUTHOR]