Nonlinear Vibration Energy Harvesting with High-Permeability Magnetic Materials

Abstract

In this chapter, we introduce the recent demonstrations of high energy density nonlinear vibration energy harvesting with high-permeability magnetic materials, which show great promise for compact and wideband vibration energy harvesting systems. Two generations of nonlinear vibration energy harvesting technology based on high-permeability magnetic material will be discussed in this chapter. The first generation energy harvester design consists of a high-permeability magnetic cantilever beam, in a solenoid, and a hard magnet pair that provides the biasing field. The mutual interaction between the vibrating highly permeable beam and the bias magnetic field of the magnets leads to maximized flux change and therefore a large induced voltage. This harvester has shown a maximum power output of 74 mW, a power density of 1.07 mW/cm³ at 54 Hz under an applied acceleration of 0.57 × g (with g = 9.8 m/s²), and a bandwidth of 10 Hz (or 18.5% of the operating frequency). The second generation energy harvester design, which has two solenoids fixed on two sides of a spring supported hard magnet pair, has demonstrated a significant increase of the output power when compared with the first generation device. The improved design has an output voltage of 2.52 V, a power density of 20.84 mW/cm³ at 42 Hz, and a half-peak working bandwidth of 6 Hz (or 14%). The coexistence of magnetostatic and elastic potential energies in both designs results in a nonlinear effect, which produces the wide working bandwidth. Details of the two generation energy harvester designs, their performance, and the origin of the nonlinear behavior are detailed in this chapter.