Serrations are based on the bionic principle of the micro-structure of bird feathers and enable owls to glide almost silently. The trailing edge serrations (TES) have established themselves in wind power as a state-of-the-art solution to reduce noise emissions. WTS has developed an innovative 3D geometry for TES, allowing significantly greater noise reduction, of up to 3 dB(A), compared to the geometries based on 2D designs with triangles that have been in use to date.

Back-flow-flap retrofit

Back-flow-flaps are based on the bionic principle of how the covering feathers of birds’ wings flip upward during their landing approach. The breakdown of large vortices into smaller vortices leads to less resistance and more lift on the rotor blade. Particularly in the case of stall-controlled turbines, it is possible to boost energy by up to 1.5%, while at the same time reducing static and dynamic loads.

Back-flow-flaps can be attached to existing wind energy converters as a retrofit system. Due to the relatively large bonding surface of the base element and the material design, they remain affixed to the turbine for its entire service life. The passive flap elements move up and down on their own due to the aerodynamic forces exerted on the rotor blade. The material and design used allow the back-flow-flaps to function even when the rotor blade is bent.

Back-flow-flaps for new turbines

The yield of wind energy converters depends primarily on the area swept by the rotor blade. For the materials currently used in the design of rotor blades, the physical load limits have been reached with today’s turbine sizes. In the future, load-reducing measures such as the use of back-flow-flaps could enable the production of larger rotor blade diameters using current state-of-the-art materials. With smaller rotor blade diameters as well, e.g. with existing turbines, the load-reducing measures can optimise operating costs and service life. In the future, back-flow-flaps may also prove useful in reducing peak loads and vibration inductions on wind energy converters, such as in the event of cross-flow, in order to avoid unscheduled maintenance or to allow the wind energy converters to continue to be operated safely beyond the previously planned service life.