Bladeless rotational piezoelectric energy harvester for hydroelectric applications of ultra-low and wide-range flow rates

Abstract

In this paper, a bladeless rotational piezoelectric energy harvester using a tipping bucket is proposed to overcome the energy collection problem from liquid with ultra-low flow and ultra-low head. It is typically difficult to collect ultra-low flow liquid energy using the blade rotation of hydro turbines. To overcome this problem, a magnetic wheel fixed to the tipping bucket is introduced in the proposed structure, which is intermittently turned multiple times through the shaft under the continuous excitation of ultra-low flow. Consequently, the mechanical energy of the ultra-low flow can be intermittently converted into rotational energy throughpassively adjustingthe center of gravity of the tipping bucket. Then, the rotational energy is converted to electric energy through the non-contact nonlinear magnetic interaction between the magnetic wheel and a piezoelectric cantilever beam with a small magnetic mass at the free end. Based on the theoretical model of the proposed structure, the various parameters affecting the energy harvesting performance are discussed in detail. Experiments were also conducted to validate the energy harvesting performance of the proposed structure. The results show that 940 μJ of electrical energy can be stored in the capacitor for powering small electronic devices when the proposed structure is used to charge the 470 μF capacitor using the rectifier circuit at 1000 mL/min.