Harvester Architecture Research Articles

Predictive lumped model for a tunable bistable piezoelectric energy harvester architecture

In this article, we propose the modelling of a tunable bistable piezoelectric energy harvester (or BPEH) architecture. The latter is a type of ambient energy converter that continues to gain attention due to their wideband frequency response. As the non-linear dynamics of BPEHs imply significant modeling complexity, dynamic lumped models are necessary to predict BPEHs’ dynamic response and should fit the type of architecture studied. The BPEH architecture of interest uses post-buckled beams to create bistability and an amplified piezoelectric actuator (or APA) to convert the ambient vibrations. To date, no dynamic lumped models have been found in existing literature that account for both the electromechanical conversion and the dynamic behavior of buckled beams, with a specific focus on their axial and bending stiffness, for this BPEH architecture. Additionally, the proposed BPEH architecture offers buckling level tunability, which is achieved using an additional APA. Hence, the aim of this paper is to propose a new lumped model for a BPEH architecture that considers the effect of the post-buckled beams’ stiffness and of the additional APA through an elasticity factor κ― . This lumped model is established using Euler Lagrange equations and is experimentally validated on a tunable BPEH prototype. This validation shows an average relative error below 6% between the model predictions and experimental dynamic response of the prototype to an ascending frequency sweep, compared to an average relative error that is around 14% for the model proposed in literature. Moreover, numerical simulations using the proposed model lead to the conclusion that there is an optimal elasticity factor κ― that ensures the maximum power output while maintaining the frequency bandwidth.

A Sub-μW Energy Harvester Architecture With Reduced Top/Bottom Plate Switching Loss Achieving 80.66% Peak Efficiency in 180-nm CMOS

This article presents a 25 nW–2.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W switched-capacitor-based solar energy harvester with integrated maximum power point tracking (MPPT). The proposed dc–dc converter avoids charging and discharging of top and bottom plate parasitic capacitors by switching both the terminals of energy source as opposed to switching just one terminal. As a result, the energy lost in switching the top and bottom plate parasitic capacitors is zero joules, which helps to achieve highly efficient switched capacitor architecture for harvesting sub 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W energy. The proposed dc–dc converter achieves same charge redistribution loss (CRL) as that of a cross-coupled dc-dc converter with half the required number of capacitors. The proposed harvester is implemented in 180 nm CMOS process and achieves an efficiency of 80% while delivering 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W output and achieves a peak efficiency of 80.66% at 2.4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W output while maintaining a regulated output of 1.8 V.

Wireless Information and Power Transfer for IoT: Pulse Position Modulation, Integrated Receiver, and Experimental Validation

Simultaneous wireless information and power transfer (SWIPT) has emerged as a viable technique to energize and connect low-power autonomous devices and enable future Internet of Things (IoT). A major challenge of SWIPT is the energy consumption of the receiver of such low-power devices. An attractive low-power solution consists of an integrated information decoder (ID) and energy harvester (EH) architecture for SWIPT receiver (IntRx) where the received radiofrequency (RF) signal is first rectified before being used for information decoding. Such architecture eliminates the need for energy-consuming RF components, such as local oscillators and mixers. This article proposes a novel modulation and demodulation method for the IntRx SWIPT architecture based on pulse position modulation (PPM) where information is encoded in the position of the pulse. The new method transmits high amplitude pulses to increase the peak-to-average power ratio (PAPR) of the transmit signal and exploits the EH’s nonlinearity so as to boost the harvested dc power. Simultaneously, the information can be decoded from the rectifier signal by simply finding the position of the pulse in a certain symbol duration. We have analyzed both the information and the power transfer performance of the newly proposed PPM for IntRx SWIPT theoretically, numerically, and experimentally. To that end, we have established a SWIPT system testbed in an indoor environment by prototyping a base station to transfer information-power signal and the IntRx SWIPT receiver, including ID and EH blocks. The performance evaluation of the PPM was carried out in various conditions, and the results have been compared and contrasted to conventional signals. Theoretical, numerical, and experimental results highlight the significant benefits of the proposed PPM scheme to enhance the power transfer performance and operate information decoding with low-power consumption.

A Simple WiFi Harvester with a Switching-Based Power Management Scheme to Collect Energy from Ordinary Routers

This paper shows the design process of a simplified harvesting circuit for WiFi at the 2.4 GHz frequency band based on the analysis of the environment available signals. Those signals and their power level define an antenna design to maximize captured energy and select the proper number of stages for a voltage multiplier so that an impedance matching network is no longer required. With this, it is possible to maintain the harvester architecture simple without sacrificing performance. The use of supercapacitors is preferred over batteries due to their high-power capacity, the ability to deliver high peak currents, long-life cycle size, and low cost. Hence, supercapacitor availability allows to devise a novel switching scheme that employs two units that favor energy use and speed up the recharging process. The built harvester exhibits a power conversion efficiency greater than 50% under an incident signal of 0 dBm in the rectenna. The tests are carried out in an academic environment using a multi SSID router, collecting 494 mJ without requiring special modifications in the router used as an energy source.

Fatigue in piezoelectric ceramic vibrational energy harvesting: A review

Piezoelectric energy harvesters have been thoroughly investigated from a material or mechanical application viewpoint. The need to understand the potential lifespan of these materials in mechanical applications requires information from both fields. This review presents methods on how these crystal structures are grown, doping agents for these materials, the architecture of transduction patches, and the vibrational energy harvester architecture that these transduction patches are placed. The cyclic nature of the vibrational energy harvester induces cyclic fatigue in these patches depending on fabrication defects and transduction material. Cyclic strain induces fatigue life, but cyclic polarization also induces crack expansion in the transduction material. This review also consolidates existing energy harvesting systems to give a basis on the current modeling and performance to show the lack of knowledge on important lifespan degradation. Critical discussions and future recommendations are provided to direct focus onto fatigue investigations to push vibrational energy harvester development forward.

Large Power Amplification in Magneto‐Mechano‐Electric Harvesters through Distributed Forcing

AbstractEnergy harvesting from extremely low frequency magnetic fields using magneto‐mechano‐electric (MME) harvesters enables wireless power transfer for operating Internet of Things (IoT) devices. The MME harvesters are designed to resonate at a fixed frequency by absorbing AC magnetic fields through a composite cantilever comprising of piezoelectric and magnetostrictive materials, and a permanent magnetic tip mass. However, this harvester architecture limits power generation because volume of the magnetic end mass is closely coupled with the resonance frequency of the device structure. Here, a method is demonstrated for maintaining the resonance frequency of the MME harvesters under all operating conditions (e.g., 60 Hz, standard frequency of electricity in many countries) while simultaneously enhancing the output power generation. By distributing the magnetic mass over the beam, the output power of the harvester is significantly enhanced at a constant resonance frequency. The MME harvester with distributed forcing shows 280% improvement in the power generation compared with a traditional architecture. The generated power is shown to be sufficient to power eight different onboard sensors with wireless data transmission integrated on a drone. These results demonstrate the promise of MME energy harvesters for powering wireless communication and IoT sensors.

Linear thermomagnetic energy harvester for low-grade thermal energy harvesting

Low-grade thermal energy, either from waste heat or from natural resources, constitutes an enormous energy reserve that remains to be fully harvested. Harvesting low-grade heat is challenging because of the low Carnot efficiency. Among various thermal energy harvesting mechanisms available for capturing low-grade heat (temperature less than 100 °C), the thermomagnetic effect has been found to be quite promising. In this study, we demonstrate a scalable thermomagnetic energy harvester architecture that exhibits 140% higher power density compared to the previously published spring–mass designs. The alternating force required to oscillate the thermomagnetic mass is generated through the interaction between two magnetic forces in opposite directions. We employed numerical modeling to illustrate the behavior of a thermomagnetic device under different operating conditions and to obtain the optimal hot-side and cold-side temperatures for continuous mode operations. A miniaturized thermomagnetic harvester was fabricated and experiments were conducted to systematically evaluate the performance. The prototype was found to exhibit an oscillation frequency of 0.33 Hz, a work output of 0.6 J/kg/cycle, and a power density of 0.2 W/kg of gadolinium under the temperature difference of 60 K.

Analysis and design of an integrated RF energy harvester for ultra low‐power environments

SummaryRadio‐frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the available RF power in three typical environments (urban, semi‐urban, and rural) is investigated. Measurements show that in the surveyed urban and semi‐urban environments, an average input power above −22 and −29 dBm, respectively, is available in the [700, 1,000] MHz band.A mathematical model of the interface between the RF rectifier and the DC‐DC converter is provided. The analysis demonstrates that the energy can be efficiently transferred to the external accumulator coupling the rectifier with a strobed, input control DC‐DC converter.Based on the measurements and the analysis, an RF harvester architecture has been designed in 65 nm Complementary Metal‐Oxide Semiconductor (CMOS) technology to operate over the [−40, 85]oC temperature and the [1.1, 2.5] V battery voltage ranges. The input control strategy adopted for the converter allows the adaptation of the harvester to the available RF power and enables a real maximum power point tracking (MPPT).Post‐layout simulation of the harvester, recharging a large capacitor, precharged at 2 V, at 950 MHz of input frequency returned a 33.4% peak efficiency with an input power of 15 μW (−18 dBm). The minimum input power leading to a positive energy balance is −30 dBm with an output voltage of 1.1 V.

Harvester : an edge service harvesting heterogeneous resources for ATLAS

The Production and Distributed Analysis (PanDA) system has been successfully used in the ATLAS experiment as a data-driven workload management system. The PanDA system has proven to be capable of operating at the Large Hadron Collider data processing scale over the last decade including the Run 1 and Run 2 data taking periods. PanDA was originally designed to be weakly coupled with the WLCG processing resources. Lately the system is revealing the difficulties to optimally integrate and exploit new resource types such as HPC and preemptible cloud resources with instant spin-up, and new workflows such as the event service, because their intrinsic nature and requirements are quite different from that of traditional grid resources. Therefore, a new component, Harvester, has been developed to mediate the control and information flow between PanDA and the resources, in order to enable more intelligent workload management and dynamic resource provisioning based on detailed knowledge of resource capabilities and their real-time state. Harvester has been designed around a modular structure to separate core functions and resource specific plugins, simplifying the operation with heterogeneous resources and providing a uniform monitoring view. This paper will give an overview of the Harvester architecture, current status with various resources, and future plans.

Architectures for wrist-worn energy harvesting

This paper reports the simulation-based analysis of six dynamical structures with respect to their wrist-worn vibration energy harvesting capability. This work approaches the problem of maximizing energy harvesting potential at the wrist by considering multiple mechanical substructures; rotational and linear motion-based architectures are examined. Mathematical models are developed and experimentally corroborated. An optimization routine is applied to the proposed architectures to maximize average power output and allow for comparison. The addition of a linear spring element to the structures has the potential to improve power output; for example, in the case of rotational structures, a 211% improvement in power output was estimated under real walking excitation. The analysis concludes that a sprung rotational harvester architecture outperforms a sprung linear architecture by 66% when real walking data is used as input to the simulations.

A velocity-amplified electromagnetic energy harvester for small amplitude vibration

Dedicated, self-powered wireless sensors are widely being studied for use throughout many industries to monitor everyday operations, maintain safety, and report performance characteristics. To enable sensors to power themselves, harvesting energy from machine vibration has been studied, however, its overall effectiveness can be hampered due to small vibration amplitudes and thus limited harvestable energy density. This paper addresses the issue by proposing a novel vibration energy harvester architecture in which a compliant mechanism and proof mass system is used to amplify the vibrational velocity of machine vibration for a linear electromagnetic generator. A prototype has been fabricated and experimentally characterized to verify its effectiveness. When operating at its natural frequency in a low base amplitude, 0.001 inch (25.4 μm) at 19.4 Hz, during lab tests, the harvester has been shown to produce up to 0.91 V AC open voltage, and a maximum power of 2 mW, amplifying the relative proof mass velocity by approximately 5.4 times. This method of locally increasing the machine vibrational velocity has been shown to be a viable option for increasing the potential power output of an energy harvester. In addition, a mathematical model is created based on pseudo-rigid-body dynamics and the analysis matches closely with experiments.

Characterization of Real-world Vibration Sources and Application to Nonlinear Vibration Energy Harvesters

Abstract A tremendous amount of research has been performed on the design and analysis of vibration energy harvester architectures with the goal of optimizing power output. Often, little attention is given to the actual characteristics of common vibrations from which energy is harvested. In order to shed light on the characteristics of common ambient vibration, data representing 333 vibration signals were downloaded from the NiPS Laboratory “Real Vibration” database, processed, and categorized according to the source of the signal (e. g. vehicle, machine, etc.), the number of dominant frequencies, the nature of the dominant frequencies (e. g. stationary, band-limited noise, etc.), and other metrics. By categorizing signals in this way, the set of idealized vibration inputs (i. e. single stationary frequency, Gaussian white noise, etc.) commonly assumed for harvester input can be corroborated and refined. Furthermore, some heretofore overlooked vibration input types are given motivation for investigation. The classification determined that, of the set of signals used in the study, 64 % of the animal source signals are best described with nonstationary dominant frequencies, 58 % of machine source signals are best described with stationary frequencies, and vehicle source signals are poorly described by any one signal type used in the classification. Nonlinear harvesters with a cubic stiffness term have received extensive attention in the scholarly literature; a numerical simulation and optimization procedure were performed using several representative signals as vibration inputs to determine the prevalence with which such a nonlinear harvester architecture might provide improvement to power output. The analysis indicated that a nonlinear harvester architecture may prove beneficial in increasing power output over a linear counterpart if the signal contains a single, dominant frequency that is not stationary in time, as evidenced by a 14 % increase in harvester power output when employing an architecture with a nonlinear cubic stiffness function. Other studies have indicated that nonlinear architectures may be beneficial for signals with nonstationary frequencies or filtered noise. 53 % of the all characterized signals fall into categories that could potentially benefit from a nonlinear oscillator architecture.

Comparative Analysis of Wrist-worn Energy Harvesting Architectures

This paper reports the simulation-based analysis of six dynamical structures with respect to their wrist-worn vibration energy harvesting capability. This work approaches the problem of maximizing energy harvesting potential at the wrist by considering multiple mechanical substructures independently of any specific transduction mechanism; rotational and linear motion-based architectures are considered. The addition of a linear spring element to the structures has the potential to improve power output. The analysis concludes that a sprung rotational harvester architecture outperforms a sprung linear architecture by 58% when real walking data is used as input to the simulations. The power output of a rotational prototype device was measured for various inputs and compared against simulation in order to corroborate the rotational device model.

Dual band harvester architecture for autonomous remote sensors

In this work we present a high dynamic range and high efficiency energy harvesting system for low power sensors architecture. This system constitutes an autonomous device potentially showing an infinite lifelong cycle of use. The designed circuit has been conceived as a dual band architecture able to capture the largest amount of EM radiation in the urban or indoor environment, since the receiver is tuned at both GSM and WiFi frequencies. The harvester power battery loading circuitry is also available on board and guarantees the required energy for the autonomous sensor to work. The system handles an incoming power typically ranging from −20dBm to 20dBm and rectifies the variable input signals into a DC voltage source with a high conversion efficiency. Theoretically speaking the rectified power is greater than 50% for an incoming power between −5dBm and 15dBm. Test measurements of the proposed system succeeded with compliant results. As a typical applications load, we have considered a commercial gas sensor, for Carbon Dioxide (CO2) detection, so proving the system capability to be employed in wireless sensors networks. The whole system, designed as discrete element board, has been conceived in order to be completely integrated in a standard CMOS technology.

Comprehensive and practical explorations of nonlinear energy harvesting from stochastic vibrations

Conversion of ambient vibrational energies to electrical power is a recent, popular motivation for research that seeks to realize self-sustaining electronic systems including biomedical implants and remote wireless structural sensors. Many vibration resources are stochastic with spectra concentrated at extremely low frequencies, which is a challenging bandwidth to target in the design of compact, resonant electromechanical harvesters. Exploitation of design-based nonlinearities has uncovered means to reduce and broaden a harvester's frequency range of greatest sensitivity to be more compatible with ambient spectra, thus dramatically improving energy conversion performance. However, studies to date draw differing conclusions regarding the viability of the most promising nonlinear harvesters, namely, those designed around the elastic stability limit, although the investigations present findings having limited verification. To help resolve the outstanding questions about energy harvesting from stochastic vibrations using systems designed near the elastic stability limit, this research integrates rigorous analytical, numerical, and experimental explorations. The harvester architecture considered is a cantilever beam, which is the common focus of contemporary studies, and evaluates critical, practical factors involved for its effective implementation. From the investigations, the most favorable incorporations of nonlinearity are identified and useful design guidelines are proposed.

Integrated bistable generator for wideband energy harvesting with optimized synchronous electric charge extraction circuit

Bistable generators have been proposed as potential solutions to the challenge of variable vibration frequencies. In the authors' previous works, a specific BSM (Buckled-Spring-Mass) harvester architecture has been suggested. It presents some properties of interests: simplicity, compactness and wide bandwidth. Using a normalized model of the BSM generator for design and optimization at different scales, this paper presents a new integrated BSM bistable generator design with the OSECE (Optimized Synchronous Electric Charge Extraction) technique which is used for broadband energy harvesting. The experimental results obtained from an initial prototype device show that the BSM generator with the OSECE circuit exhibits better performance for low coupling cases or reverse sweep excitations. This is also confirmed by simulations for the proposed integrated generator. Good applications prospective is expected for the bistable generator with the nonlinear OSECE circuit.

An Antenna Co-Design Dual Band RF Energy Harvester

RF energy is widely available in urban areas and thus presents a promising ambient energy harvesting source. In this paper, a CMOS harvester circuit is modeled and analyzed in detail at low environmental power levels. Based on the circuit analysis, a design procedure is given for a narrowband energy harvester. The antenna and harvester co-design methodology is discussed to improve RF to DC energy conversion efficiency. We demonstrate that it is difficult to harvest RF energy over a wide frequency band if the ambient RF energy sources are weak, owing to the voltage requirements. Since most ambient RF energy lies in a few narrow bands, a dual/multi-band energy harvester architecture should be able to harvest much of the available RF energy. A dual-band CMOS energy harvester is designed and fabricated using an IBM 0.13 μm process. The simulated and measured results demonstrate a dual-band energy harvester that obtains over 9% efficiency for two different bands (around 900 MHz and around 1900 MHz) at an input power as low as -19.3 dBm. The DC output voltage of this harvester is over 1 V, which can be used to recharge the battery to form an inexhaustibly powered communication system.

Analysis of two dimensional, wide-band, bistable vibration energy harvester

In this paper a new strategy for developing broadband, bi-directional, vibration energy harvesters is presented. Often energy harvesting systems address unidirectional incoming energy, however this is a strong limitation when considering real applications; in fact it is very likely that incoming vibrations will not be aligned with the direction of motion of the harvester. Therefore the presence of irregular vibrations along several orientations reduces the energy conversion and the harvester efficiency.Furthermore, often the ambient vibrations come with energy distributed over a wide spectrum of frequencies, with predominance of low frequency components such as vibration generated by: highway traffic, human motions, trains, electrical machines and generic noise-induced vibrations.The classical approach is based on vibrating mechanical bodies (linear systems) able to collect energy through the adoption of smart materials, magnetic or electrostatic solutions. Moreover this family of systems performs poorly for off-resonance conditions.For this reasons suitable harvester architecture for collecting energy from vibrations having a broad spectrum and distributed along different directions is needed.This work addresses both these issues by proposing a double nonlinear bi-stable oscillator with a large amplitude response over a broad range of frequencies. Such system improves traditional scavengers based on linear mechanical principles, which only give a suitable response if the dominant ambient vibration frequency is tuned to the mechanical resonance. Moreover a suitable topology of the double bistable oscillator is proposed such to obtain a bi-axial vibrations energy harvester. The system proposed here is composed of two magnetically coupled bi-stable beams, having orthogonal directions of deflection, with piezoelectric output; in presence of mechanical vibrations the beams will respond to both the inertial excitation and the magnetic coupling. Therefore the total output power, being the sum of the two piezoelectric outputs, will be optimized independently of the direction of the incoming vibrations.In this paper the two dimensional wide-band energy harvester is first described and analytically modeled, extensive simulations have been performed to evaluate the behavior of the two magnetically coupled beams. A macro-prototype has been conceived and realized and a measurement campaign has been performed in order to validate the principle.

Two Dimensional Bistable Vibration Energy Harvester

Abstract In this paper a new strategy for broadband, bi-directional, vibration energy harvester is presented. Often energy harvesting systems address unidirectional incoming energy, however this is a strong limitation when considering real applications; in fact it is very likely that incoming vibrations will not be aligned with the direction of motion of the harvester. Irregular vibrations along several orientations reduce the energy conversion and the harvester efficiency. A suitable harvester architecture for collecting energy from vibrations distributed along different directions is needed. Furthermore, often the ambient vibrations come with energy distributed over a wide spectrum of frequencies, with predominance of low frequency components. This work addresses both these issues by proposing a nonlinear bistable oscillator based on two-dimensional, magnetically-coupled, PZT-based beams able to extract energy from ambient vibrations with arbitrary directions. The basic idea will be presented together with the experimental prototype realized and the results obtained.