Impact-Based Electromagnetic Energy Harvester with High Output Voltage under Low-Level Excitations

Abstract

Abstract:To expand the applications of vibrational energy harvesters (VEHs) as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs) are usually low, which complicates the power management circuit by an indispensable voltage boosting element. To this end, an impact-based non-resonant EMVEH mainly composed of an outer frame and an inner frame on rollers is proposed. Numerical simulations based on a mathematical model of the harvester are conducted to analyze the effects of structural parameters on the output performance. Under base excitation of 0.1 and 0.3 (where g is the gravitational acceleration, 1 g = 9.8 m·s −2 ), the experimental maximum root mean square voltages of a harvester prototype across a resistor of 11 kΩ are as high as 7.6 and 16.5 V at 6.0 and 8.5 Hz, respectively, with the maximum output powers of 5.3 and 24.8 mW, or the power densities of 54.6 and 256 µW cm −3 . By using a management circuit without a voltage boosting element, a wireless sensor node driven by the prototype can measure and transmit the temperature and humidity every 20 s under base excitation of 0.1 g at 5.4 Hz.

A Nonlinear Electromagnetic Energy Harvesting System for Self-Powered Wireless Sensor Nodes

“…Horizontal base excitations make the inner frame move with respect to the outer frame on the rollers; as a result, the magnetic flux through the coils changes and an induced electromotive force occurs in the coils. The springs are helpful to decrease the energy loss during the collisions between the inner and outer frames [26].…”

“…The influences of the initial gap and the stiffness of the springs on the electrical outputs have been numerically analyzed in our previous work [26]. To further improve the energy-scavenging efficiency, the gap between two adjacent magnet rows decreases from 7 mm to 5 mm.…”

“…The circuit may be denoted by a resistor with a full-bridge rectifier and a regulating capacitor. A nonlinear electromagnetic energy harvester connecting to a linear resistive has been studied [26]. Non-resistive components connecting to linear electromagnetic energy harvesters may be expressed by a signum function [27].…”

“…First, a linear electromagnetic energy harvester is connected to a linear interface circuit, which is a pure resistive electrical load [25]. Second, a nonlinear electromagnetic energy harvester is connected to a linear circuit [26]. Third, a linear electromagnetic energy harvester is connected to a nonlinear circuit containing non-resistive components [27].…”

“…Our group has developed an impact-based nonlinear EMEH with arrays of magnet and coil [26]. The most prominent characteristic of this device is the high output voltage, with the voltage of 16 V across an 11 kΩ resistor under the base excitation of 0.3 g at 8.5 Hz.…”