Reducing blade noise

Serrations on the trailing edge of a blade can break up the turbulent boundary layer and reduce the aerodynamic noise from a 1.5 MW turbine to that of a 600 kW machine. As a result the amount of electric power production can be doubled with no increase in noise emissions. This is the main conclusion of a series of European projects under the European DATA (low noise blade design) program involving a string of major industry names, including rotor blade makers Aerpac and LM Holland, wind turbine manufacturer Lagerwey, the Delft university in the Netherlands and Dutch national laboratory ECN. The project was financed with grants from the EU and from Dutch energy agency NOVEM. The noise reduction achieved is 4-6 dB(A). "Optimised blade designs are realised that yield reductions of 2-4 dB," the study team told participants at the European special topic conference, Wind Power for the 21st Century, held in Kassel, Germany, in September. Team member Werner Hoffmans from Delft says the research has improved the potential for accurately predicting noise emissions in the design stage. "We believe this is a valuable tool and we regret that its existence is not yet known to many manufacturers."