A comprehensive multi-objective optimization study for the aerodynamic noise mitigation of a small wind turbine

Abstract

The noise emitted by small wind turbines is one of the main reasons for their poor public perception for use in urban areas. An optimization study was performed to mitigate the aerodynamic noise of a 750 W turbine through altering the geometry of solid and more importantly hollow blades for the first time. A validated in-house code simultaneously minimizes the aerodynamic noise and maximizes the output power. The inertia of the blades is another important design parameter for small turbines as it influences the starting performance. The minimization of starting time was added to the above-mentioned goals and another optimization was done. The outcomes highlight the great significance of two ends of the blade; the tip section has a key role in alleviation of the noise as well as the improvement of the power coefficient while the root part could speed up the starting. Quantitatively, the optimization of solid blades shows that a 1.9 dB reduction in aerodynamic noise is attainable at the expense of a 1.6% loss in the power coefficient. Compared to solid blades, the aerodynamic noise and the starting time were reduced for hollow ones by 1 dB and 30% respectively. The latter is very attractive for use of small turbines in low-wind areas.