Fully-passive tethered flapping airfoil to harvest high-altitude wind energy

Abstract

Airborne Wind Energy (AWE) system is an emerging technology aiming at harvesting high-altitude wind energy, which cannot be exploited by tower-mounted wind turbines. In the state-of-the-art AWE system, airborne actuators and ground-based drivers are necessary to control the posture and movements of the airborne component because it generates power through a complicated reciprocating motion. However, the control units required in the traditional AWE system inevitably introduce additional weight and decrease the system reliability, posing a challenge to designing a light airborne component with full automation. To address this issue, we developed a highly compact AWE system without any mechanical driver or control module. By adopting a biomimetic flapping airfoil, the new AWE system avoids the unnecessary power consumption of traditional design and yields consistent power output via a fully-passive flapping motion. Through a systematic optimization of structural parameters in a numerical wind tunnel, the fully-passive AWE system demonstrated efficient energy harvesting with a power coefficient of 0.825 and an efficiency of 18.9%. This advanced technology cannot only solve the fundamental issues that have persisted in the AWE system, but also offer a low-cost approach to enhance high-altitude wind power generation.