Anisotropic self-biased dual-phase low frequency magneto-mechano-electric energy harvesters with giant power densities (original) (raw)
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Magnetostrictive–piezoelectric composite structures for energy harvesting
Journal of Micromechanics and Microengineering, 2012
In this paper, harvesters coupling magnetostrictive and piezoelectric materials are investigated. The energy conversion of quasi-static magnetic field variations into electricity is detailed. Experimental results are exposed for two macroscopic demonstrators based on the rotation of a permanent magnet. These composite/hybrid devices use both piezoelectric and magnetostrictive (amorphous FeSiB ribbon or bulk Terfenol-D) materials. A quasi-static (or ultra-low frequency) harvester is constructed with exploitable output voltage, even in quasi-static mode. Integrated micro-harvesters using sub-micron multilayers of active materials on Si have been built and are currently being characterized.
Actuators, 2015
Recent advances in phase transition transduction enabled the design of a non-resonant broadband mechanical energy harvester that is capable of delivering an energy density per cycle up to two orders of magnitude larger than resonant cantilever piezoelectric type generators. This was achieved in a [011] oriented and poled domain engineered relaxor ferroelectric single crystal, mechanically biased to a state just below the ferroelectric rhombohedral (F R)-ferroelectric orthorhombic (F O) phase transformation. Therefore, a small variation in an input parameter, e.g., electrical, mechanical, or thermal will generate a large output due to the significant polarization change associated with the transition. This idea was extended in the present work to design a non-resonant, multi-domain magnetoelectric composite hybrid harvester comprised of highly magnetostrictive alloy, [Fe 81.4 Ga 18.6 (Galfenol) or Tb x Dy 1´x Fe 2 (Terfenol-D)], and lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) domain engineered relaxor ferroelectric single crystal. A small magnetic field applied to the coupled device causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. We have demonstrated high energy conversion in this magnetoelectric device by triggering the F R-F O transition in the single crystal by a small ac magnetic field in a broad frequency range that is important for multi-domain hybrid energy harvesting devices.
Vibration energy harvesting by magnetostrictive material
Smart Materials and Structures, 2008
A new class of vibration energy harvester based on magnetostrictive material (MsM), Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsM harvesting device and an energy harvesting circuit. Compared to piezoelectric materials, the Metglas 2605SC offers advantages including higher energy conversion efficiency, longer life cycles, lack of depolarization and higher flexibility to survive in strong ambient vibrations. To enhance the energy conversion efficiency and alleviate the need of a bias magnetic field, Metglas ribbons are transversely annealed by a strong magnetic field along their width direction. To analyze the MsM harvesting device a generalized electromechanical circuit model is derived from Hamilton's principle in conjunction with the normal mode superposition method based on Euler-Bernoulli beam theory. The MsM harvesting device is equivalent to an electromechanical gyrator in series with an inductor. In addition, the proposed model can be readily extended to a more practical case of a cantilever beam element with a tip mass. The energy harvesting circuit, which interfaces with a wireless sensor and accumulates the harvested energy into an ultracapacitor, is designed on a printed circuit board (PCB) with plane dimension 25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0-5.5 V. In experiments, the maximum output power and power density on the resistor can reach 200 μW and 900 μW cm −3 , respectively, at a low frequency of 58 Hz. For a working prototype under a vibration with resonance frequency of 1.1 kHz and peak acceleration of 8.06 m s −2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve 576 μW and 606 μW cm −3 , respectively, which compete favorably with piezoelectric vibration energy harvesters.
Experimental study of power harvesting from vibration using giant magnetostrictive materials
The interest in research and development of smart actuators, sensors and power generators that used Giant Magnetostrictive Materials (GMM) is growing. Both academia and industry are actively looking for bread utilization of GMM technology for different applications (active vibration and noise control, structural health monitoring, self-powered electronic equipments and systems, MEMS, robotics, etc.). In the paper we present results of experimental study of vibration-to-electric energy conversion using giant magnetostrictive materials. The magnetostrictive power harvesting device was built using Terfenol-D rod. The fundamental base for development of the device is a Villari effect. That is, by applying a mechanical stress to a magnetostrictive material, the magnetization along the direction of the applied stress of the material varies due to the magnetostrictive effect. The flux variation obtained in the material induces an emf in a coil surrounding the material. Test rig's measurement data have confirmed the expected function of the developed magnetostrictive power harvesting device. Electrical power of the device for different input parameters of external vibration field was examined. The experimental results are presented for Terfenol-D rod with 50 mm in length and 15 mm in diameter which have shown that efficiency of the developed magnetostrictive power harvesting device varies from 8% to 25%.
Development of Novel Magnetostrictive Energy Harvester
2017
In this paper, a novel vibration-based harvester using machineable magnetostrictive materials (MSM), Galfenol, is presented. Galfenol, an alloy of iron and gallium, is able to convert stress to magnetic field. Galfenol is malleable, strong with high magnetic permeability. The presented setup exploits a 50 mm length and 10 mm diameter Galfenol rod which is clamped in the middle of a cantilever beam. With the provided setup, the beam only has vertical adjustable vibrations. The output signal of 1500 turns pickup coil shows 250 mV for 27 Hz (natural frequency of cantilever beam with Galfenol) which is an acceptable result for a harvester. The results of the experiments show the capability of Galfenol to be used in harvesters.
Increased mechanical robustness of piezoelectric magnetoelastic vibrational energy harvesters
Microelectronic Engineering, 2018
This work presents a cantilever based broadband piezoelectric magnetoelastic vibration energy harvester with increased mechanical robustness. The energy harvester is fabricated using KOH etching to define the cantilever and the proof mass is made using micromachined Fe foils which together with a pair of miniature magnets provides the magnetoelastic properties. KOH etching leads to very sharp corners at the anchoring point of the cantilever which makes the cantilever fragile. The mechanical robustness of the energy harvesters is increased using a lithography-free two-step fabrication process where a thermal oxidation is used for corner rounding. The corner rounding at the anchoring point lowers the stress concentration and thereby increases the robustness of the device. The radius of curvature for the corner depends linearly on the thickness of the oxide. Both enhanced and non-enhanced beams are excited at increasing frame accelerations. The conventional beams break at frame accelerations of around 3 g while the enhanced break at almost twice as much, 5.7 g. The devices are characterized electrically by impedance measurements in both their linear and non linear regime. The magnetoelastic behaviour can be adjusted by varying the beam-magnet distance which allows for both spring softening and spring hardening.
Bulletin of the Polish Academy of Sciences Technical Sciences
In this paper, the performance and frequency bandwidth of the piezoelectric energy harvester (PZEH) is improved by introducing two permanent magnets attached to the proof mass of a dual beam structure. Both magnets are in the vicinity of each other and attached in such a way to proof mass of a dual beam so that they create a magnetic field around each other. The generated magnetic field develops a repulsive force between the magnets, which improves electrical output and enhances the bandwidth of the harvester. The simple rectangular cantilever structure with and without magnetic tip mass has a frequency bandwidth of 4 Hz and 4.5 Hz, respectively. The proposed structure generates a peak voltage of 20 V at a frequency of 114.51 Hz at an excitation acceleration of 1 g (g= 9.8 m/s 2). The peak output power of a proposed structure is 25.5 µW. The operational frequency range of a proposed dual beam cantilever with a magnetic tip mass of 30 mT is from 102.51 Hz to 120.51 Hz, i.e., 18 Hz. The operational frequency range of a dual beam cantilever without magnetic tip mass is from 104.18 Hz to 118.18 Hz, i.e., 14 Hz. There is an improvement of 22.22% in the frequency bandwidth of the proposed dual beam cantilever with a magnetic tip mass of 30 mT than the dual beam without magnetic tip mass.
High power density vibration energy harvester with high permeability magnetic material
Journal of Applied Physics, 2011
An alternative design of vibration energy harvester was demonstrated to significantly increase the output power density. This design had two magnetic solenoids fixed at two sides of a spring supported hard magnet pair with anti-parallel magnetization, which produced a spatially inhomogeneous bias magnetic field for switching the flux inside the solenoids during vibration. Experimental results showed an output voltage of 2.52 V and a power density 20.84 mW/cm3 at 42 Hz, with a half peak working bandwidth of 6 Hz. This vibration energy harvester design leads to high output voltage, power and power density that are critical for real applications.