The demand of affordable, renewable energy is still increasing. Wind energy is seen as one of the most promising resources for electric energy supply. To reduce the cost of wind energy the dimensions of wind energy turbines are still increasing. This leads to higher power output due to the larger rotor diameters, but also due to the higher wind speeds above the boundary layer. This increase in rotor diameter comes on the price of much higher structural loads especially in the rotor blade root. These are mainly caused by gravity, wind shear, gusts and the tower influence to the blade.

A reduction of these loads would allow further increase of rotor diameter, a longer lifetime or a lighter design and therefore be advantageous for the turbine. Load reduction can be achieved by using a trailing edge flap at the outer region of the blade, comparable with an aircraft’s rudder, which is capable of moving several times per blade revolution enabling the manipulation of the flow to alleviate changes in the aerodynamic loading. In contrast to aircraft, 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 has been designed within the SmartBlades project for the mentioned purpose. Based on this design, a demonstrator was built, which was tested in a wind tunnel and on a rotational test site for its performance.

The paper will present the approach beginning with some design and modelling considerations of the flexible trailing edge and the demonstrator, which was used for testing. Afterwards, results from the wind tunnel experiment at Oldenburg University and the rotational experiment at the field research site of the Technical University in Denmark (DTU) \[RJ1\] will be shown. In these experiments, the effectiveness of the trailing edge flap could be demonstrated in the wind tunnel as well as in free field. Based on pressure taps and force sensors, the change in the lift of the airfoil due to the deflection of the flexible trailing edge was measured. Furthermore, the result of different simple control strategies for the trailing edge in terms of load reduction will be presented.


Design and Experimental Investigation of a Flexible Trailing Edge for Wind Energy Turbine Blades

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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