Design and performance evaluation of a tunable rotational energy harvester with stress-uniform piezoelectric vibrator utilizing an air-solid coupling chamber

Energy harvesting technology plays a remarkable role in enabling self-powered wireless electronics, sensor networks, and the Internet of Things. One of the key issues hindering the application of existing piezoelectric rotational energy harvesters is how to enhance their structural robustness and environmental adaptability. Here, a tunable rotational energy harvester with a stress-uniform piezoelectric vibrator utilizing an air-solid coupling chamber was proposed. The energy harvester introduces an air-solid coupling chamber to transform the excitation force into air pressure to provide uniform stress on the piezoelectric vibrator, which can effectively avoid the damage of stress concentration. A combination of theoretical, numerical, and experimental approaches was employed to validate the structural feasibility and operational principles of the energy harvester. Results demonstrate that the peak voltage and effective frequency can be regulated by the combination of excitation ratio, chamber height, and excitation distance. A peak output power of 8.53 mW was obtained from the energy harvester at a load resistance of 18 kΩ. The 220 μF, 470 μF, and 1000 μF capacitors were saturated at 7.73 V, 7.55 V, and 6.99 V during 25 s, 50 s, and 100 s, respectively. Furthermore, the energy harvester successfully demonstrated sustainable power generation capabilities by continuously illuminating an array of 250 LEDs and simultaneously powering both a light strip and a digital thermometer.