Aerodynamic noise from wind turbines and rotor blade modification. JOULE 2 Final report

A major limitation on the use of wind turbines in Europe is their noise radiation. The amount of wind energy generation capacity that can be installed at a site is directly dependent on the noise radiated. A noise reduction in the order of only 2 dB(A) can increase the number of installations by about 50%. The tip noise experiments on commercial wind turbines have confirmed the results obtained in the wind tunnel. Tip designs generating strong tip vortices (e.g. extreme curvature at the leading edge) interacting with the TE (trailing edge longer than the leading edge) cause additional noise in the high frequency range (a second maximum in the 2 kHz frequency range of the sound power spectra is an indication of tip noise). Reductions of the overall sound power level up to 4 dB(A) can be reached by designs avoiding these effects (see Annex I and III). The measurements in the open and in the wind tunnel showed that the tip noise radiation is very sensitive to the angle of attack. This leads to the conclusion that the following design criteria should be followed: - Cutting away of the trailing edge - modest leading edge sweep - reduction of the angle of attack at the tip. (orig./AKF)Available from TIB Hannover: F97B1178+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEEuropean Union (Euro), Brussels (Belgium)DEGerman