A miniaturized electromagnetic energy harvester with off-axis magnet and stacked flexible coils

In this study, a semi-analytic approach to optimizing the external load resistance of a bi-stable electromagnetic energy harvester is presented based on the harmonic balance method. The harmonic balance analyses for the primary harmonic (period-1T) and two subharmonic (period-3T and 5T) interwell motions of the energy harvester are performed with the Fourier series solutions of the individual motions determined by spectral analyses. For each motion, an optimization problem for maximizing the output power of the energy harvester is formulated based on the harmonic balance solutions and then solved to estimate the optimal external load resistance. The results of a parametric study show that the optimal load resistance significantly depends on the inductive reactance and internal resistance of a solenoid coil––the higher the oscillation frequency of an interwell motion (or the larger the inductance of the coil) is, the larger the optimal load resistance. In particular, when the frequency of the ambient vibration source is relatively high, the non-linear dynamic characteristics of an interwell motion should be considered in the optimization process of the electromagnetic energy harvester. Compared with conventional resistance-matching techniques, the proposed semi-analytic approach could provide a more accurate estimation of the external load resistance.

Download Full-text

Linear electromagnetic energy harvester system embedded on a vehicle suspension: from modeling to performance analysis

Energy ◽

10.1016/j.energy.2021.119991 ◽

2021 ◽

pp. 119991

Author(s):

B. Lafarge ◽

S. Grondel ◽

C. Delebarre ◽

O. Curea ◽

C. Richard

Keyword(s):

Performance Analysis ◽

Energy Harvester ◽

Electromagnetic Energy ◽

Vehicle Suspension

Download Full-text

Study of the Properties of a Hybrid Piezoelectric and Electromagnetic Energy Harvester for a Civil Engineering Low-Frequency Sloshing Environment

Energies ◽

10.3390/en14020391 ◽

2021 ◽

Vol 14 (2) ◽

pp. 391

Author(s):

Nan Wu ◽

Yuncheng He ◽

Jiyang Fu ◽

Peng Liao

Keyword(s):

Output Power ◽

Energy Harvester ◽

Civil Engineering ◽

Maximum Output Power ◽

Low Frequency ◽

Electromagnetic Energy ◽

Maximum Output ◽

Piezoelectric Film ◽

Hybrid Energy ◽

Level Height

In this paper a novel hybrid piezoelectric and electromagnetic energy harvester for civil engineering low-frequency sloshing environment is reported. The architecture, fabrication and characterization of the harvester are discussed. The hybrid energy harvester is composed of a permanent magnet, copper coil, and PVDF(polyvinylidene difluoride) piezoelectric film, and the upper U-tube device containing a cylindrical fluid barrier is connected to the foundation support plate by a hinge and spring. The two primary means of energy collection were through the vortex street, which alternately impacted the PVDF piezoelectric film through fluid shedding, and the electromotive force (EMF) induced by changes in the magnetic field position in the conducting coil. Experimentally, the maximum output power of the piezoelectric transformer of the hybrid energy harvester was 2.47 μW (circuit load 270 kΩ; liquid level height 80 mm); and the maximum output power of the electromagnetic generator was 2.72 μW (circuit load 470 kΩ; liquid level height 60 mm). The low-frequency sloshing energy collected by this energy harvester can drive microsensors for civil engineering monitoring.

Download Full-text

Frequency Tuning of a Nonlinear Electromagnetic Energy Harvester

Journal of Vibration and Acoustics ◽

10.1115/1.4025445 ◽

2013 ◽

Vol 136 (1) ◽

Cited By ~ 10

Author(s):

Longhan Xie ◽

Ruxu Du

Keyword(s):

Magnetic Field ◽

Permanent Magnets ◽

Energy Harvester ◽

Frequency Tuning ◽

Nonlinear Behavior ◽

Stretch Ratio ◽

Electromagnetic Energy ◽

Elastic Strings ◽

Simulation And Experiment ◽

Frequency Tunable

This paper investigates a frequency-tunable nonlinear electromagnetic energy harvester. The electromagnetic harvester mainly consists of permanent magnets supported on the base to provide a magnetic field, and electrical coils suspended by four even-distributed elastic strings to be an oscillating object. When the base provides external excitation, the electrical coils oscillate in the magnetic field to produce electricity. The stretch length of the elastic strings can be tuned to change their stretch ratio by tuning adjustable screws, which can result in a shift of natural frequency of the harvester system. The transverse force of the elastic strings has nonlinear behavior, which broadens the system's frequency response to improve the performance of the energy harvester. Both simulation and experiment show that the above-discussed electromagnetic energy harvester has nonlinear behavior and frequency-tunable ability, which can be used to improve the effectiveness of energy harvesting.

Download Full-text