A wireless structure health monitoring (SHM) system for wind turbine blades has been actively researched to realize its low cost and efficient maintenance. A sustainable power supply to the wireless SHM system installed in a rotating blade has been one of the most challenging issue. Vibration energy harvesting via piezoelectricity or electromagnetism can provide a solution, but varied blade rotation and the corresponding random natured vibration make it difficult to design a practical harvester. In this paper, an impact-driven piezoelectric energy harvester (PEH) is proposed to efficiently generate an electric power at PEH’s natural frequency for any rotation speed of blades. This harvester can be installed within the blade to power the wireless SHM system sustainably. The impact-driven PEH consists of a piezoelectric cantilever beam and a gravity-induced rotator. When the wind turbine blade rotates, the orientation of the cantilever changes but the orientation of the gravity-induced rotator remains fixed to a global coordinate system (defined on the earth). At every rotation cycle, the gravity-induced rotator strikes the cantilever tip, which causes vibration. Then, the piezoelectric cantilever beam generates electric power at PEH’s natural frequency. A testing setup for the proposed PEH is built, by installing the PEH prototype on the blades driven by a DC motor. Experimental result shows that the proposed PEH generates electric power at PEH’s natural frequency for any rotation speed, and average power generated from the proposed PEH is 1.56 mW at the typical blade’s rotation speed of 20 RPM.
Hyun Jun Jung, Stanley Chervin, Miles Smith, and Soobum Lee, "Design of an impact-driven piezoelectric energy harvester with gravity-induced rotator for wind turbine blade monitoring system (Conference Presentation)," Proc. SPIE 10595, Active and Passive Smart Structures and Integrated Systems XII, 105951Y (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 08, 2018; Published: 3 April 2018); https://doi.org/10.1117/12.2295625.5763085354001.
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