Magnetic coupling and flextensional amplification mechanisms for high-robustness ambient wind energy harvesting

Abstract

Harvesting wind energy is becoming increasingly significant for its availability and abundance in the ambient environment, which is a promising strategy to develop self-powered small-scale electromechanical systems. However, the drawbacks of the current small-scale wind energy harvesters, namely, low robustness, narrow wind speed range, and low output power hinder the application in natural environment. Here, we propose an innovative approach for rotational piezoelectric wind energy harvesting using magnetic coupling and force amplification mechanisms, which has a higher equivalent piezoelectric coefficient, better robustness and broader wind speed range for application. Thanks to the reasonable symmetrical opposite magnetic arrangement, the resistance torque has been reduced significantly while the effective force can be maximized. The effective magnetic coupling modes are clarified, and the corresponding dynamic models are established. The effects of key parameters on the output performance are analyzed and the effects of assembly errors on reluctance torque are discussed as well. The performances of the proposed harvester are investigated through laboratory experiments and outdoor natural wind tests. The results show that the established model can characterize the energy harvester precisely. In an outdoor natural wind environment, the prototype is able to work continuously for more than 12,000 s with the wind speed from ~3 m/s to ~10 m/s. After a long period of experiments, no damage to the prototype is observed. Besides, the proposed harvester can generate high and relatively stable open-circuit voltages from low wind speeds to high wind speeds. These results reveal that the proposed harvester has high robustness and broad wind speed range for the application.