Wind power is becoming more and more popular, but one of the major reasons that it is so expensive is that the wind is not uniform. On some days the wind blows very slowly but on others it blows very hard or even worse provides vicious gusts. This means that you have to build a wind turbine that can survive the worst gusts which makes it far heavier than it has to be for 99% of its normal use. Most turbines can feather or change the angle of their blades in very high winds to avoid damage, but this can be too slow to avoid damage from a quick gust.
A group from Risø DTU in Denmark is working on a technology which may help. In the same way that you can change the amount of lift on a plane wing using flaps, or aerolons to control the plane, if you add a trailing edge flap to the wind turbine blade you can greatly alter the amount of lift it is producing and therefore the forces on the structure.
The big difference between a wind turbine blade and a wing is that an aeroplane is moveable and can be regularly maintained, where as wind turbines are usually in inaccessable places, and maintainance would stop them being economic anyway. This means that conventional mechanical flaps wouldn't work, so the group is working on flexible rubber or plastic flaps which can be activated by pumping air or hydraulic fluid into specially designed cavities at the rear of the flap.
As the flap is much lighter than the whole blade it can be activated far more quickly than the feathering system so it can adapt to individual gusts without a huge use of energy, which should enable wind turbines to be built lighter and therefore cheaper.
They have built laboratory models which are very promising, and the group is now moving onto building a real test wind turbine.
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