Insect wings are flexible without being flaccid. They change shape when air pressure is applied. The ability to bend the wings can change the direction of pressure forces on the wing. Flexible wings can bend in ways that improve thrust without input of extra energy. The flexible wings of a dragonfly are far more efficient than if the wings were stiff.
Engineers are interested in applying the lessons of flexible dragonfly wings to wind generators that use the power of the wind to rotate turbine blades. A group of engineers* created small scale turbine blades with no flexibility, high flexibility and moderate flexibility. The high flexibility blades performed poorly. However, the moderately flexible blades were up to 35% more efficient than blades with no flexibility.
This research has interesting possibilities. One of the issues is how to scale these results to large power generators of the type now in use. The very large blades must maintain their integrity under a variety of stressful conditions. A material with appropriate combinations of strength and flexibility will be a key to making these findings useful.
*V. Cognet, S. Courrech du Pont, I. Dobrev, F. Massouh, B. Thiria. Bioinspired turbine blades offer new perspectives for wind energy. Proceedings of the Royal Society A. February 17, 2017 http://rspa.royalsocietypublishing.org/