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Nature is the inspiration behind a project to reduce the fluctuating loads on wind turbine blades by changing their geometry, currently ongoing at Denmark's national laboratory at Risø. "The objective is to achieve the same level of regulation as when a hawk holds its head fixed and thereby is able to hover in the wind through a combination of active and passive regulation of the wings," according to the project description.

The study is modelling the performance of a 33 metre blade for a Vestas V66 turbine. The profile of the trailing edge of the outermost 11 metres of the blade is adjustable -- and there are six adjustable segments. A sophisticated control system is used to monitor the deflections and adjust the blade geometry to dampen the fluctuations in load. The analysis suggests the flapwise blade root bending moments can be reduced by 40-60%. If that can be achieved without adding undue complexity to the blade, it should enable worthwhile reductions in blade strength -- and hence weight and cost.

Once the aerodynamic and aeroelastic modelling is complete, wind tunnel tests will be used to verify the accuracy of the modelling predictions and to test the operation of the advanced control systems required.