Insect wings don’t have this problem. Because they’re flexible, the wings of bees and dragonflies are able to direct the aerodynamic load in the direction of their flight, increasing the power. And because they naturally bend in the wind, they can minimize drag to avoid damage.
To see whether such flexibility would improve the efficiency of wind turbines, Cognet and his team built small-scale turbine prototypes with three different rotor styles. One was completely rigid, one was somewhat flexible, and one was very flexible. All three turbines had three rotors, but the flexible ones were made with a pliable material called polyethylene terephthalate, whereas the rigid version was made with a stiff synthetic resin.
In wind tunnel tests, the most flexible blades proved to be a bit too flaccid, and they failed to produce as much power as their stiffer brethren. But the moderately flexible blades outperformed the rigid ones, creating up to 35% more power and allowing the blades to operate efficiently in a wider range of wind conditions, the team reports today in the Proceedings of the Royal Society A: Mathematical and Physical Sciences.
