Generator For Energy Harvesting Research Articles

Kinetic AC/DC Converter for Electromagnetic Energy Harvesting in Autonomous Wearable Devices

A nano-power integrated circuit is designed to convert the ac output of an electromagnetic micro generator for wearable kinetic energy harvesting to dc usable power. The converter is designed to minimize the quiescent current and to maximize the energy conversion and maximum power point tracking efficiency from the kinetic energy harvester. The architecture implements an ac/dc chopper exploiting the intrinsic inductance of the transducer combined with a zero-drop rectifier. An optimal switching scheme is derived for the converter and a corresponding control circuit is developed and optimized for low power consumption. The converter is designed in an SMIC 130-nm process, and circuit simulations show an efficiency of 87%–88% with respect to the maximum power point of the transducer with a battery supply voltage ranging from 3.5 V to 4.2 V. The quiescent current of the converter is as low as 250 nA.

Modeling and experimental study of a linear power generator for road energy harvesting

There are a large number of vehicles running on the road, and the shape of the road surface varies accordingly. Thus, this kinetic energy can be harvested to power electrical equipment along the road, and this energy harvesting technology has good environmental adaptability because it will not be affected by the sun, wind, or other natural environmental factors. A permanent magnet linear generator is designed and tested for road kinetic energy harvesting. The generator is described by a single degree of freedom system model with mass-spring-damping. The system response is analysed on the basis of the system model. The mover's vibration response is modeled over two stages according to the vehicle's wheel load. The power generation process is simulated and calculated according to the aforementioned models. The magnetic force and magnetic field are calculated by use of the finite element method; because of the non-linear magnetic force, the output electromotive force (EMF) is subject to frequency multiplication under conditions of sinusoidal displacement input. A prototype is manufactured and embedded in the road for experimental research purposes. The test result shows that the maximum peak-to-peak value of the output EMF and average power are up to 484.18 V and 255.1 W, respectively, as a car passes over the generator at a speed 20 km/h. Moreover, the time-domain and amplitude-frequency characteristics agree well with those calculated. It is demonstrated that the proposed model is able to describe the road power generator.

A Review of On-Chip Micro Supercapacitors for Integrated Self-Powering Systems

Miniaturized self-powering systems that integrate both energy harvesters and energy storage units as the power sources are essential to realize maintenance-free wireless sensor networks, implantable medical devices, and active radio frequency identification systems. On-chip micro supercapacitors (MSCs) are promising candidates for energy storage in such systems by providing high power densities, fast charge/discharge rates, and long cycle life. Researchers have been improving the performances, especially energy and power densities, of MSCs in recent years. This paper reviews the fundamental working mechanisms and design considerations of on-chip MSCs with special emphasis on the advantages of 3-D configurations. Typical fabrication methods are summarized, and their effects on the device performance and system integration are analyzed. In particular, the power generation of micro energy harvesters and the power consumption of typical wireless micro systems are surveyed, providing the basic and targeting performance requirements of future MSCs that can be integrated with them. [2017-0069]

Design of An Electromagnetic Energy Harvesting System Applied to The Shock Absorber of A Sport Utility Vehicle : Part I. Single Permanent Magnet Layer Coreless Type

This paper deals with the design of an electromagnetic energy harvesting generator for the suspension system of a sport utility vehicle. The proposed generator is composed of a single coreless type permanent magnet layer, which increases flux density across the coil windings and eliminates flux leakage by using the Halbach PM array, thus improving the machine’s performance, including flux linkage and output power. The goal of the system is to regenerate energy from the kinetic energy of the suspension system of the sport utility vehicle. The proposed generator physically combines electrical and mechanical components, in which permanent magnets, coil windings, and back iron are attached to the body of the shock absorber. The design’s performance was investigated using the finite element method (FEM) and validated by comparison with experimental data.

Modeling and performance analysis of duck-shaped triboelectric and electromagnetic generators for water wave energy harvesting

Summary Triboelectric nanogenerator (TENG) is a newly proposed technology for effectively converting mechanical energy into electricity. Triboelectric nanogenerator has shown a great potential for harvesting the clean and abundant energy of ocean waves. Recently, a duck-shaped TENG device has been proposed as a lightweight, cost-effective, highly stable, and efficient system for scavenging the existing energy in water waves. In this paper, a detailed investigation on the performance of the duck-shaped TENG is presented. Then, a comparative analysis between the TENG device and an equivalent electromagnetic generator (EMG) for wave energy harvesting is performed. The electric output characteristics of both techniques under various mechanical and electrical conditions are obtained. The analysis demonstrates that at a low operating frequency of 2.5 Hz, the TENG and EMG achieve the peak power density of 213.1 and 144.4 W/m3, respectively. The present paper provides guidance for design and optimization of hybrid TENG and EMG technology toward scavenging the blue energy.

Flexible PET/EVA-based piezoelectret generator for energy harvesting in harsh environments

Stable and repeatable operation is paramount for practical and extensive applications of all energy harvesters. Herein, we develop a new type of flexible piezoelectret generator, which converts mechanical energy into electricity consistently even under harsh environments. Specifically, the generator, with piezoelectric coefficient (d33) reaching ~ 6300 pC/N, had worked stably for continuous ~ 90000 cycles, and the generator pressed by a human hand produced load peak current and power up to ~ 29.6 μA and ~ 0.444mW, respectively. Moreover, the capability to steadily produce electrical power under extreme moisture and temperature up to 70°C had been achieved for possible applications in wearable devices and flexible electronics.

Corrugated Textile based Triboelectric Generator for Wearable Energy Harvesting

Triboelectric energy harvesting has been applied to various fields, from large-scale power generation to small electronics. Triboelectric energy is generated when certain materials come into frictional contact, e.g., static electricity from rubbing a shoe on a carpet. In particular, textile-based triboelectric energy-harvesting technologies are one of the most promising approaches because they are not only flexible, light, and comfortable but also wearable. Most previous textile-based triboelectric generators (TEGs) generate energy by vertically pressing and rubbing something. However, we propose a corrugated textile-based triboelectric generator (CT-TEG) that can generate energy by stretching. Moreover, the CT-TEG is sewn into a corrugated structure that contains an effective air gap without additional spacers. The resulting CT-TEG can generate considerable energy from various deformations, not only by pressing and rubbing but also by stretching. The maximum output performances of the CT-TEG can reach up to 28.13 V and 2.71 μA with stretching and releasing motions. Additionally, we demonstrate the generation of sufficient energy from various activities of a human body to power about 54 LEDs. These results demonstrate the potential application of CT-TEGs for self-powered systems.

Double-folding paper-based generator for mechanical energy harvesting

Paper-based generators are essential elements for building all paper-based systems. To obtain robust paper-based generators with outstanding high power outputs, this paper introduced a new type of double-folding paper-based generator by folding two paper components together. The output performance levels of the double-folding generator were twice higher than that of the single-folding and parallel-plate generators. A peak power of ~3.24 mW was achieved under a stimulating frequency of 3 Hz. Furthermore, 47 light-emitting diodes (LEDs) were lit directly by a double-folding paper-based generator assembled to the crack of a door that opens and closes. This finding indicated the potential applications of the double-folding generator in the production of door ornaments or for security in places where doors frequently open and close.

A Study on Bandwidth and Performance Limitations of Array Vibration Harvester Configurations

Abstract Many researchers introduced an array of generators for broadband energy harvesting. The array has been studied in comparison to a single element from this array, but never compared to a single reference harvester with same volume as the whole array. This paper presents a theoretical study of evaluating the performance of the array harvester in comparison to the reference harvester. Power from the reference harvester as well as from the array is analytically calculated. The array is compared to the reference harvester when loaded by their optimal resistances which provide maximum power capability. The comparison is divided into two sections: firstly when the elements of the array are tuned to resonate at matching frequencies and secondly when they are tuned to non-matching resonance frequencies. The comparisons lead to two significant limits of the working bandwidth of the array: the lower and the upper limit. Between the two limits, the power produced from the array is less than the reference harvester, but with a small additional bandwidth. Below the lower limit, the array has no advantage over the reference harvester. Above the upper limit, output power of the array is inconsistent. Hence, design guidelines for the array are provided.

Capillary driven electrokinetic generator for environmental energy harvesting

We propose a novel electrokinetic generator driven by the capillary force. By coupling the capillary with water evaporation, the generator can output power as long as water evaporation exists, thus it can harvest environment energies from waste heat, wind power to solar energy. Experimental results show that a capillary driven electrokinetic generator, with evaporation area of 4.9cm2 and fluidic channel area of 2mm2, can output maximum electrical voltage of ∼40mV and current of 9.6μA. The voltage and current can both be greatly enhanced by reducing the area of fluidic channel, approaching maximum power of 0.22mW according to the theoretical calculations. In addition, a live-tree driven electrokinetic generator with an output electrical power of 2.7μW is demonstrated. These results show that the capillary driven electrokinetic generator is of promising potential in self-powered systems.

Assessing Stability and Predicting Power Generation of Electromagnetic Vibration Energy Harvesters Using Bridge Vibration Data

This paper presents the use of the power harvesting ratio (PHR) approach for evaluating the power harvesting capabilities of an electromagnetic vibration energy harvester. This is done for different electrical loads and measured bridge vibration data displaying multiple frequency components. Bridge vibration data are collected and characterized. The modes of the bridge are determined using a model sledge hammer, and the response of the bridge to a single vehicle is measured. Analysis of the data reveals that several of the modes contribute toward a response with multiple non-negligible frequency components. Measured bridge time-series data are then replayed on an experimental setup with an electromagnetic vibration energy harvester. Six electrical loads are implemented on the experimental platform: four passive loads and two active loads. The PHR approach is used to predict the average power from each load. Experimentally measured average power is within 6% of the predicted average power. The PHR approach is also used to successfully predict harvester instability for the active load dictated by the maximum power transfer theorem and validated experimentally. This paper demonstrates the utility of the PHR approach in evaluating harvester stability and performance for multifrequency excitations and sophisticated electrical loads, including active loads.

Synergetic effects in composite-based flexible hybrid mechanical energy harvesting generator

Tribo–piezoelectric composite generators are fabricated to analyze the contribution of each effect and to understand the impact of each material.

Broadband and three-dimensional vibration energy harvesting by a non-linear magnetoelectric generator

Vibration, widely existing in an ambient environment with a variety of forms and wide-range of scales, recently becomes an attractive target for energy harvesting. However, its time-varying directions and frequencies render a lack of effective energy technology to scavenge it. Here, we report a rationally designed nonlinear magnetoelectric generator for broadband and multi-directional vibration energy harvesting. By using a stabilized three-dimensional (3D) magnetic interaction and spring force, the device working bandwidth was largely broadened, which was demonstrated both experimentally and theoretically. The multidirectional vibration energy harvesting was enabled by three identical suspended springs with equal intersection angles, which are all connected to a cylindrical magnet. Numerical simulations and experimental results show that the nonlinear harvester can sustain large-amplitude oscillations over a wide frequency range, and it can generate power efficiently in an arbitrary direction. Moreover, the experimental data suggest that the proposed nonlinear energy harvester has the potential to scavenge vibrational energy over a broad range of ambient frequencies in 3D space.

Ferrofluid-based triboelectric-electromagnetic hybrid generator for sensitive and sustainable vibration energy harvesting

A vibration energy harvester that utilizes a liquid medium has been the subject of active research recently given its advantages of shape adaptability, scalability, and durability. In this work, a ferrofluid-based vibration energy harvester with a hybrid triboelectric-electromagnetic operating mechanism is proposed for the first time. The ferrofluid suspension solution is made with water and magnetic nanoparticles. Electrostatic induction between the polymer sidewall and the solvent water activates a triboelectric generator component, while electromagnetic induction between the suspended magnetic nanoparticles and an outer coil activates the electromagnetic generator component. Experimental results for the ferrofluid-embedded hybrid energy harvester showed an extremely low threshold amplitude and a wide operating frequency range, both of which can be particularly advantageous for harvesting subtle and irregular vibrations.

Fabrication and performance evaluation of a metal-based bimorph piezoelectric MEMS generator for vibration energy harvesting

This paper presents the development of a bimorph microelectromechanical system (MEMS) generator for vibration energy harvesting. The bimorph generator is in cantilever beam structure formed by laminating two lead zirconate titanate thick-film layers on both sides of a stainless steel substrate. Aiming to scavenge vibration energy efficiently from the environment and transform into useful electrical energy, the two piezoelectric layers on the device can be poled for serial and parallel connections to enhance the output voltage or output current respectively. In addition, a tungsten proof mass is bonded at the tip of the device to adjust the resonance frequency. The experimental result shows superior performance the generator. At the 0.5 g base excitation acceleration level, the devices pooled for serial connection and the device poled for parallel connection possess an open-circuit output voltage of 11.6 VP–P and 20.1 VP–P, respectively. The device poled for parallel connection reaches a maximum power output of 423 μW and an output voltage of 15.2 VP–P at an excitation frequency of 143.4 Hz and an externally applied based excitation acceleration of 1.5 g, whereas the device poled serial connection achieves a maximum power output of 413 μW and an output voltage of 33.0 VP–P at an excitation frequency of 140.8 Hz and an externally applied base excitation acceleration of 1.5 g. To demonstrate the feasibility of the MEMS generator for real applications, we finished the demonstration of a self-powered Bluetooth low energy wireless temperature sensor sending readings to a smartphone with only the power from the MEMS generator harvesting from vibration.

A structural bionic design: From electric organs to systematic triboelectric generators

Bioelectricity and triboelectrification are well-known and widely existing phenomena in nature, and the investigation of their mechanisms and utilizations has attracted much attention for a long time. As traditional investigations suggested, the mechanism of electric organs is that the electrocytes are lined up so a current of ions can flow through them, and thus they are stacked in a sequence so that each one adds up to form a potential difference. For varieties of triboelectric generators, most of them feature extremely high voltage but limited current, which is the major challenge to pracitcal utilization. Here, we present a structural bionic design based on the microstructure of electric organs to improve the output current of systematic triboelectric generators. This study correlating electric organs and triboelectric generators not only benefits the practical use of systematic triboelectric generators for energy harvesting, but also offers a new approach to imitate more compositive and tunable electronic devices from biological structures.

Optimization study of a piezoelectric bistable generator with doubled voltage frequency using harmonic balance method

Bistable generator for vibration energy harvesting is one of the most promising solutions to reach practically enhanced performance. Due to the buckled–spring–mass–specific behavior, the deformation of the piezoelectric transducer is nonlinearly dependent on the displacement, especially in the inter-well motion case. An analytical model is developed using harmonic balance analysis for the buckled–spring–mass generator architecture. Contrary to the usual method, a special doubled frequency voltage solution in the inter-well motion case is assumed in harmonic balance analysis to obtain an accurate predictive model, which is validated by experimental results. The influence of five critical parameters on the performance is thoroughly discussed. Design rules are then deduced: low damping ratio, properly high coupling level, matched load, optimal buckling level, and low characteristic frequency are required to get optimal performance in the inter-well motion case. Besides, we show some interesting results about the parameter optimization study.

Analytical Tools for Investigating Stability and Power Generation of Electromagnetic Vibration Energy Harvesters

This paper presents a general linear methodology for analyzing how the choice of electrical load affects stability and average power generation of an electromagnetic vibration energy harvester. Using bond graph techniques, the entire electromechanical harvesting system is modeled as a dynamically equivalent electrical circuit and ultimately recast as a feedback control system. This modeling approach enables the use of well-established linear control tools to assess the overall stability of the energy harvesting system. These tools are used to show: 1) why the load which would result in maximum power transfer from the harvester to the load, as established by the maximum power transfer theorem (MPTT), can only be achieved at a single frequency, and 2) how to ensure the system will always remain stable if the harvester is used in conjunction with an active load. Moreover, the presented modeling approach enables development of the power harvesting ratio—an analytical method for quantifying the harvester's power generation when multi-frequency excitation is involved. A custom harvester was constructed for experimental evaluation of the power harvesting ratio when varying: 1) the electrical load attached across the harvester leads and 2) the multifrequency vibrations used to excite the harvester.

Characterization of thermoelectric generator for energy harvesting

Abstract This paper presents a system for characterization of thermoelectric generators (TEGs) for energy harvesting. This system can monitor and characterize up to three TEGs simultaneously and it is comprised by two main electronic circuits: The first one is composed by twelve input channels being three for reading voltage, three for reading current by making use of instrumentation amplifiers (reference ACS712) and six thermocouples for signal reading (

Silk fabric-based wearable thermoelectric generator for energy harvesting from the human body

The development of flexible thermoelectric (TE) power generators for harvesting energy from the human body has attracted significant interest in recent years. However, thus far, a wearable TE power generator based on commercially available fabrics has not been realized. In this study, nanostructured Bi2Te3 and Sb2Te3 were synthesized and deposited on both sides of a silk fabric to form TE columns. These TE columns were connected with silver foils to fabricate a prototype integrating an array of 12 thermocouples. The generator could effectively convert thermal energy into electricity in the temperature difference (ΔT) range of 5–35K. The maximum voltage and power outputs were ∼10mV and ∼15nW, respectively, with no significant change in both, during 100cycles of bending and twisting. Different voltage output profiles were collected from an arm-attached generator before and after 30min of walking, to highlight the immense potential of the silk fabric-based TE generator. This study provides a new approach for developing fabric-based TE power generators for practical applications in wearable electronics.