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Piezoelectric energy harvester (PEH) arrays are practical solutions to the low and unreliable power output of a single PEH. However, most PEH circuits are developed for addressing the one-channel ac input from a single PEH. In this article, an extensible rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) array interface with the maximal power point tracking (MPPT) function to manage the multiple ac inputs from the PEH arrays is designed. The ac–dc conversion is performed by the ReL-SSHI topology with passive peak switches featured with self-powered characteristic and fast cold-start. Only one shared inductor is employed, greatly reducing the circuit volume and cost. The MPPT module for each channel is implemented by a simple envelope detector and an ultra-low power hysteresis controller and achieves continuous energy extraction by adapting the fractional normal-operation voltage method. A developed discrete array interface able to handle three PEHs effectively executes the MPPT for each channel with the uphill and downhill response speeds of 2.0 and 7.1 V/s, and a maximal MPPT efficiency of 97.1%. This circuit boosts the power output by 485% compared with that by the traditional full-bridge rectifier, around 33% higher than that from existing synchronous electric charge extraction array interfaces. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvester (PEH) arrays are promising in many application scenarios. However, few interface circuits have been developed to manage the multiple ac inputs from PEHs. This article proposes an extensible parallel synchronized switch harvesting on inductor array interface scheme to realize a multiinput conversion from PEH arrays. We develop a split-inductor-capacitor topology that can extract electrical energy from multiple PEHs. The proposed circuit topology effectively handles the inductor access conflict in the cases of PEHs with close, identical, and opposite vibration phases, insensitive to ac input phase changes. For demonstrating the capability of dealing with multiple ac inputs from PEHs and the enhancement effect on power output, we construct and test a self-powered three-channel array circuit with the passive peak detection function. Excited by sinusoidal vibrations, our circuit effectively avoids the energy return and efficiently achieves the power combination of the three PEHs. Compared with the classic full-bridge circuit, the proposed circuit helps increase the power output by 4.8 times. Also, to show the universality of the circuit, the circuit's operation under various excitations istested and analyzed. [ABSTRACT FROM AUTHOR]

Inspired by hand push whisk blenders that are widely used in the kitchen, we here propose an energy harvester that enables conversion of low-frequency translational vibration to high-speed rotations and further generates electricity via the electromagnetic effect. The whisk-inspired energy harvester (W-EH) is composed of an internal thread sleeve, an external thread driving shaft, a spring, and a buoy. Compared with transmission approaches used by the electromagnetic power generators, the proposed design has the superiority of low cost, ultralow operation frequency (lower than 1 Hz), and high-power output. Tests in water indicate that the normalized power density is 300% higher than state of the art. Excited by mimicking ocean waves at 1.5 Hz, the W-EH prototype generates a maximum power of 64.4 mW and succeeds in lighting up 115 LEDs simultaneously, whose power is enough for continuous operations of most wireless sensors. [ABSTRACT FROM AUTHOR]

To merge the gap between the low-power output of piezoelectric energy harvesters (PEHs) and the high-power demand of sensors of Internet of Things, researchers recently start to explore PEHs arrays. However, few circuits have been developed to manage the multiple ac inputs from PEHs arrays. This article presents a self-powered PEH array interface circuit based on the synchronized switching and discharging to a storage capacitor through an inductor (SSDCI) technique. The array interface can output a maximum total power greater than the sum of each individual peak power, and achieve a high efficiency when multiple PEHs connect to the SSDCI array circuit. Simulation and experiment are performed to demonstrate the advantages of the SSDCI array interface. The tested results show that the designed SSDCI array circuit achieves an efficiency of 82.3% with three input sources, and allows a gain up to 300% in terms of maximal output power compared to the full-bridge rectifier. In addition, only the peak detection is utilized for the switching control; therefore, the SSDCI array circuit is realized more easily and with fewer components compared to the existing synchronous electric charge extraction array interfaces. [ABSTRACT FROM AUTHOR]

In this paper, we propose a truss-based compressive-mode piezoelectric energy harvester to harness energy from low frequency vibrations with a wide bandwidth and a high-power output. The design is an integration of mainly three modules: separated excitation mechanism from transduction mechanism for low resonant frequency, truss mechanism for magnification of the applied force onto the piezoelectric element, and amplitude limit mechanism to induce impact forces. We then formulate the harvester as a two-degrees-of-freedom system featured by superposition of harmonic and impact-induced nonlinear responses. Based on our structure design, we fabricate a prototype to conduct experimental studies. The experimental results show that the harvester is capable of harnessing energy efficiently from vibrations at the resonant frequencies of 3.3 and 6.09 Hz. The total bandwidth is expanded to 4.2 Hz owing to the structure nonlinearity and bifurcation. The open circuit voltage reaches 83.3 V and maximum power gets up to 38.2 mW with the matching impedance. Also, the harvester exhibits excellent charging performance in terms of saturated voltage and charging time. [ABSTRACT FROM AUTHOR]

Nonlinear vibration is capable of effectively extending the frequency bandwidth of energy harvesters. Either hardening or softening nonlinearity has been used in various designs to achieve broad-bandwidth energy harvesting. In this paper, we propose a new method to achieve reversible hysteretic responses, i.e., both hardening and softening nonlinear responses, mechanically without additional magnetic interactions. This tunable nonlinearity endows energy harvesters with a great adaptability to environment. The proposed energy harvester is composed of a flexural center and two mass blocks, supported by a pair of elastic rods that are fixed on a vibration base. Different nonlinear responses are invoked by tilting the fixed–fixed elastic rods at different angles. A lumped-parameter model is developed to simulate the nonlinear electromechanical coupling system, and that is analytically solved by virtue of the high-order perturbation technique. The dynamic responses under different frequencies and accelerations are analytically characterized and compared well with the experimental data measured from a fabricated prototype. Furthermore, a nonlinear conditioning circuit (self-powered series synchronized switch harvesting on inductor) is constructed and tested with the proposed nonlinear energy harvester, with which the performance is enhanced about 200% for both resistive loads and capacitive loads. [ABSTRACT FROM PUBLISHER]

We propose a new concept for harvesting vibration energy from multiple directions. Our approach effectively exploits the nonlinear vibration of a doubly clamped elastic rod, converting and amplifying excitations to compressive loads in piezoelectric materials. The proposed multidirectional compressive-mode piezoelectric energy harvester (MC-PEH) is capable of isotropically harnessing vibration energy from any angle in a plane. Meanwhile, the MC-PEH demonstrates a high-voltage output and a wide working bandwidth, along with the distinct softening nonlinear phenomena. Theoretical analysis and experimental testing are performed and exhibit good agreement over a range of excitation frequencies. This study enhances the practicability and adaptability of using energy harvesters in a complex environment. [ABSTRACT FROM PUBLISHER]