This thesis investigates the potential of a semi-passive trailing-edge flap on a large conceptual wind turbine. The mechanism passively reacts to blade and tower accelerations by changing the airfoil camber, opposing the dynamic loads on the turbine. An active element is present, which influences the mean of the flap oscillation. First, a low-fidelity, parameter study was done in MATLAB. Next, the flap model was implemented in the aeroelastic code HAWC2, to capture dynamic and structural effects due to blade accelerations. Results show that the semi-passive design reduces ultimate and fatigue loads, during normal power production. Effects on AEP are minimized by the active element and are an improvement to the passive model. The present study motivates simulation of more design load cases, e.g. parked or grid failure. Also, the benefits of the mechanism should be investigated in combination with a new, enlarged, rotor at similar key loads.