R & D

Research in wind energy


Introduction
        For wind turbine manufacturers, the basic aim of research and development of wind turbines is to be able to manufacture ever more cost effective machines.


Basic aerodynamic research
CFD simulation        Wind turbines engineers use techniques such as stall, which aircraft designers try to avoid at all costs. Stall is a very complex phenomenon, because it involves air flows in three dimensions on wind turbine rotor blades (e.g. the centrifugal force will induce an airflow which makes the air molecules move radially along the rotor blade from its root towards the tip of the blade).

3D computer simulations of air flows are rarely used in the aircraft industry, so wind turbine researchers have to develop new methods and computer simulation models to deal with these issues.

Computational Fluid Dynamics (CFD) is a group of methods that deal with simulating air flows around e.g. rotor blades for wind turbines. The picture shows a computer simulation of the air flows and pressure distributions around a wind turbine rotor blade moving towards the left.



Aerodynamic improvement devices
        A number of technologies known from the aircraft industry are increasingly being applied to improve the performance of wind turbine rotors.
        One example is vortex generators, which are small fins, often only about 0.01 m tall, which are fitted to the surface of aircraft wings. The fins are alternately slightly skewed a few degrees to the right and the left. The fins create a thin current of turbulent air on the surface of the wings. The spacing of the fins is very accurate to ensure that the turbulent layer automatically dissolves at the back edge of the wing. Curiously, this creation of minute turbulence prevents the aircraft wing from stalling at low wind speeds. Wind turbine blades are prone to stalling even at low wind speeds close to the root of the blade where the profiles are thick. Consequently, on some of the newest rotor blades you may find a stretch of one metre or so along the back side of the blade (near the root) equipped with a number of vortex generators.