Energy harvesting from self-sustained limit cycle rolling oscillations of rectangular wings

In the present work, we designed and tested 3 different aspect ratios of rectangular wings to produce self-sustained limit cycle rolling oscillations for energy harvesting. It is achieved by implementing a piezoelectric generator. The effect of air flow speed, angle of attack (AOA), aspect ratio and the location of the piezoelectric generator are parametrically investigated. It is shown that with proper chosen air speed and AOA, self-sustained rolling oscillations are successfully produced on the rectangular wings. The self-sustained rolling oscillations are associated with a dominant frequency of approximately 1 Hz. The frequency is increased with the piezoelectric generator attached. However, the amplitude is decreased. The measured minimum air speed and the critical AOA are 16 m/s and 15 degree respectively. The wing with smallest aspect ratio is easies to trigger the limit cycle rolling. Furthermore, the energy harvesting performance is maximized as the piezoelectric is attached in parallel with the oncoming flow streamline. The results show that approximately 50 mW electricity is produced from a wing with a surface area of 25312 mm² considering the internal resistance 100 kQ of the piezoelectric generator. Unlike conventional wind energy harvesting technology, the present work opens up new possible way to harvest energy from ambient environment via nonlinear limit cycle aeroelastic oscillations.