The Smart Rotor Concept on Wind Turbines - Actuators and Structures

Wind turbines suffer heavily from fatigue loads but current load control concepts are not effective in mitigating them. This thesis contributes to the development of a novel concept in which the air flow over the blade is controlled through spanwise distributed devices. The work is aimed at implementing adaptive materials, such as shape memory alloys and piezo electrics to the blade's surface creating a continuously deforming surface which influences the aerodynamics. Wind tunnel tests that were conducted show that a substantial decrease in dynamic loads can be observed with a well designed system. The work is further aimed at implementing shape memory alloys into a actively deforming surface that can act as a flap on wind turbines. Shape memory alloys show an incredible power density, but once embedded the biggest limitation is the actuation frequency because the lattice transformation that drives the actuation function is driven by heat which has to be dissipated. In this thesis we present a concept for an actuator with internal cooling channels which result in a ten times faster cooling rate of the shape memory alloy and which brings the actuator in the frequency range that is needed for large wind turbines. To demonstrate this, a fuzzy logic controller to control the surface's deformation was implemented and the actuator was applied on a structural concept. The conclusion of the thesis is that the load alleviation concept through spanwise distributed devices, based on adaptive materials, shows a lot of potential. Moreover, several technical barriers for implementation of the system have been removed, but the durability of the actuator needs to be improved