Meso-scale piezoelectric energy harvester for low-frequency rotational motion

Wind energy has been seen as a most potential renewable energy. However, in shore environments, the wind turbine usually suffers constantly impact of sand and strong wind speed, which causes the surface deteriorate: cracks may appear. To reduce the wind turbine operations and maintenance (O&M) cost, assembling a self-powered surface condition monitoring system (SCMS) becomes the most important measures. In this paper, a meso-scale piezoelectric energy harvester (PEH) was fabricated, based on a tapered cantilever beam to scavenge the rotational energy to power SCMS. The advantages are to increase its output power density and its lifetime comparing to the traditional rectangular cantilever beam. A frequency up-conversion method was adopted to accommodate PEH to working under variety of rotational speed by using two opposing magnets. With different distances between two magnets, the output voltage and the daily output energy of the PEH were investigated under 5 rpm-30 rpm rotational speed. The maximum output voltage is 2.7 V, 9.1 V and 13.6 V when the magnets spacing is 3 mm, 2 mm and 1 mm, respectively. For the magnet spacing of 1 mm, the daily output energy of the PEH was estimated to be 5.26 J under periodic magnetic plucking at 30 rpm, much higher than the 0.2 J of SCMS's daily energy consumption, making this harvester an excellent solution for the abovementioned needs.