ABSTRACT
Global warming and greenhouse gas emissions are of great concern. To reduce such emissions, there is a global trend towards cleaner energy sources. Promising alternatives for coal and other fossil fuels are nuclear power and renewable energy sources. One of the most promising renewable sources is wind energy. However, concerns exist with wind turbine technology, and one of the main ones is in the noise that occurs during operation. In order to successfully reduce or prevent the noise generated, the sources of noise must be identified. Two major sources of noise are present during operation: mechanical and aerodynamic. Mechanical noise generally originates from the many different components within the wind turbine, such as the generator, the hydraulic systems and the gearbox. Various mechanical noise prevention strategies exist, such as vibration suppression, vibration isolation and fault detection techniques, which will be described in this paper. Prevention strategies for aerodynamic noise are
also discussed because it is the dominant source of noise from wind turbines. The largest contribution to aerodynamic noise comes from the trailing edge of wind turbine blades. Strategies for reducing aerodynamic noise include adaptive solutions and wind turbine blade modification methods. Adaptive noise reduction techniques include varying the speed of rotation of the blades and increasing the pitch angle. Although such strategies have been successfully implemented for noise reduction purposes, they can cause significant power loss. Therefore, alternative adaptive solutions are sought. Blade modification methods such as adding serrations have proven to be beneficial in reducing noise without any power loss.
