Designing and testing a flexible trailing edge for wind energy turbine blades

Abstract

Decreasing reserves of fossil energy resources are a major challenge for future power generation. Therefore, regenerative energy sources are increasingly investigated. Especially wind energy offers a potential for electric power supply. In order to use the limited sites for wind turbines most efficiently, the nacelle height and rotor diameter of the wind turbines have increased tremendously in the last decades. A drawback of this growth arises from the fact, that the parts of bigger plants are much more loaded by their own weight. Therefore, especially cyclic bending moments at the blade root caused by the weight of the blade, wind shear and gust loads are limiting the blade lifetime with larger scale. Lowering these loads would allow larger blades, a longer lifetime or a lighter construction. Load reduction can be achieved by a trailing edge flap at the outer region of the blade comparable to a rudder at aircrafts, which is able to be moved multiple times every revolution of the blade. By this, the lift of the blade can be altered which allows a load reduction. In contrast to aircrafts, sealing against environmental media, such as rain, dust, insects and so on is much more important to allow a high lifetime. Therefore, a flexible and gapless trailing edge is designed for the mentioned purpose. Beginning from a concept study, finite element models are created to derive a structural approach of the flexible trailing edge. Based on this approach, a demonstrator is built, which can be used for spinning tests at a special facility at the Technical University of Denmark (DTU). In this paper, an overview is given about the design process of the flexible trailing edge, the instrumentation of the demonstrator and the testing in the laboratory.