A new concept to mitigate loads for wind turbines based on a passive flap

This paper considers the preliminary investigation of a passive flap for the mitigation of loads on wind turbines. The flap moves passively in response to blade vibrations, opposing them, thereby yielding an attenuation of loads. In comparison to active flaps, this solution has the advantage of not requiring sensors nor actuators, resulting in a particularly simple implementation, with potential benefits in manufacturing and maintenance costs. The paper first describes the concept of the novel passive flap, highlighting its main characteristics. A proof of concept of the new idea is then given by a simulation study conducted with the combination of a sectional model of the flap and a multibody model of the rest of the machine. Results, obtained for a 10MW wind turbine, indicate the ability of the passive flap in attenuating blade vibrations in a significant frequency range, which in turn yield a reduced fatigue damage to the structure without noticeable effects in terms of power production.