Showing papers on "Energy harvesting published in 2014"
TL;DR: The TENG can be a sensor that directly converts a mechanical triggering into a self-generated electric signal for detection of motion, vibration, mechanical stimuli, physical touching, and biological movement and is a new paradigm for energy harvesting.
Abstract: Triboelectrification is one of the most common effects in our daily life, but it is usually taken as a negative effect with very limited positive applications. Here, we invented a triboelectric nanogenerator (TENG) based on organic materials that is used to convert mechanical energy into electricity. The TENG is based on the conjunction of triboelectrification and electrostatic induction, and it utilizes the most common materials available in our daily life, such as papers, fabrics, PTFE, PDMS, Al, PVC etc. In this short review, we first introduce the four most fundamental modes of TENG, based on which a range of applications have been demonstrated. The area power density reaches 1200 W m−2, volume density reaches 490 kW m−3, and an energy conversion efficiency of ∼50–85% has been demonstrated. The TENG can be applied to harvest all kinds of mechanical energy that is available in our daily life, such as human motion, walking, vibration, mechanical triggering, rotation energy, wind, a moving automobile, flowing water, rain drops, tide and ocean waves. Therefore, it is a new paradigm for energy harvesting. Furthermore, TENG can be a sensor that directly converts a mechanical triggering into a self-generated electric signal for detection of motion, vibration, mechanical stimuli, physical touching, and biological movement. After a summary of TENG for micro-scale energy harvesting, mega-scale energy harvesting, and self-powered systems, we will present a set of questions that need to be discussed and explored for applications of the TENG. Lastly, since the energy conversion efficiencies for each mode can be different although the materials are the same, depending on the triggering conditions and design geometry. But one common factor that determines the performance of all the TENGs is the charge density on the two surfaces, the saturation value of which may independent of the triggering configurations of the TENG. Therefore, the triboelectric charge density or the relative charge density in reference to a standard material (such as polytetrafluoroethylene (PTFE)) can be taken as a measuring matrix for characterizing the performance of the material for the TENG.
1,169 citations
TL;DR: A detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferro-electrics can be found in this article.
Abstract: This review provides a detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferroelectrics. These properties are, in many cases, present in the same material, providing the intriguing prospect of a material that can harvest energy from multiple sources including vibration, thermal fluctuations and light. Piezoelectric materials are initially discussed in the context of harvesting mechanical energy from vibrations using inertial energy harvesting, which relies on the resistance of a mass to acceleration, and kinematic energy harvesting which directly couples the energy harvester to the relative movement of different parts of a source. Issues related to mode of operation, loss mechanisms and using non-linearity to enhance the operating frequency range are described along with the potential materials that could be employed for harvesting vibrations at elevated temperatures. In addition to inorganic piezoelectric materials, compliant piezoelectric materials are also discussed. Piezoelectric energy harvesting devices are complex multi-physics systems requiring advanced methodologies to maximise their performance. The research effort to develop optimisation methods for complex piezoelectric energy harvesters is then reviewed. The use of ferroelectric or multi-ferroic materials to convert light into chemical or electrical energy is then described in applications where the internal electric field can prevent electron–hole recombination or enhance chemical reactions at the ferroelectric surface. Finally, pyroelectric harvesting generates power from temperature fluctuations and this review covers the modes of pyroelectric harvesting such as simple resistive loading and Olsen cycles. Nano-scale pyroelectric systems and novel micro-electro-mechanical-systems designed to increase the operating frequency are discussed.
882 citations
TL;DR: An overview of SWIPT systems with a particular focus on the hardware realization of rectenna circuits and practical techniques that achieveSWIPT in the domains of time, power, antennas, and space is provided.
Abstract: Energy harvesting for wireless communication networks is a new paradigm that allows terminals to recharge their batteries from external energy sources in the surrounding environment. A promising energy harvesting technology is wireless power transfer where terminals harvest energy from electromagnetic radiation. Thereby, the energy may be harvested opportunistically from ambient electromagnetic sources or from sources that intentionally transmit electromagnetic energy for energy harvesting purposes. A particularly interesting and challenging scenario arises when sources perform simultaneous wireless information and power transfer (SWIPT), as strong signals not only increase power transfer but also interference. This article provides an overview of SWIPT systems with a particular focus on the hardware realization of rectenna circuits and practical techniques that achieve SWIPT in the domains of time, power, antennas, and space. The article also discusses the benefits of a potential integration of SWIPT technologies in modern communication networks in the context of resource allocation and cooperative cognitive radio networks.
870 citations
TL;DR: The idea of wireless power transfer (WPT) has been around since the inception of electricity and Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an?all-surpassing importance to man? as discussed by the authors.
Abstract: The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an ?all-surpassing importance to man? [1]. A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays [2], contact-lens-based augmented reality [3], and smart dust [4], among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla?s work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed.
745 citations
TL;DR: In this paper, the pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored, as well as pyro-electric architectures and systems that can be employed to improve device performance.
Abstract: This review covers energy harvesting technologies associated with pyroelectric materials and systems. Such materials have the potential to generate electrical power from thermal fluctuations and is a less well explored form of thermal energy harvesting than thermoelectric systems. The pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored. Materials of interest are discussed and pyroelectric architectures and systems that can be employed to improve device performance, such as frequency and power level, are described. In addition to the solid materials employed, the appropriate pyroelectric harvesting circuits to condition and store the electrical power are discussed.
589 citations
14 Oct 2014
TL;DR: In this article, various ambient energy harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed.
Abstract: In this paper, various ambient energy-harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed. Specifically, far-field low-power-density energy-harvesting technology is thoroughly investigated and a benchmarking prototype of an embedded microcontroller-enabled sensor platform has been successfully powered by an ambient ultrahigh-frequency (UHF) digital TV signal (512-566 MHz) where a broadcasting antenna is 6.3 km away from the proposed wireless energy-harvesting device. A high-efficiency dual-band ambient energy harvester at 915 MHz and 2.45 GHz and an energy harvester for on-body application at 460 MHz are also presented to verify the capabilities of ambient UHF/RF energy harvesting as an enabling technology for Internet of Things and smart skins applications.
527 citations
TL;DR: This paper reviews the current state of research on piezoelectric energy harvesting devices for low frequency (0–100 Hz) applications and the methods that have been developed to improve the power outputs of the piezoesterday's energy harvesters.
Abstract: In an effort to eliminate the replacement of the batteries of electronic devices that are difficult or impractical to service once deployed, harvesting energy from mechanical vibrations or impacts using piezoelectric materials has been researched over the last several decades. However, a majority of these applications have very low input frequencies. This presents a challenge for the researchers to optimize the energy output of piezoelectric energy harvesters, due to the relatively high elastic moduli of piezoelectric materials used to date. This paper reviews the current state of research on piezoelectric energy harvesting devices for low frequency (0–100 Hz) applications and the methods that have been developed to improve the power outputs of the piezoelectric energy harvesters. Various key aspects that contribute to the overall performance of a piezoelectric energy harvester are discussed, including geometries of the piezoelectric element, types of piezoelectric material used, techniques employed to match the resonance frequency of the piezoelectric element to input frequency of the host structure, and electronic circuits specifically designed for energy harvesters.
506 citations
TL;DR: In this article, a broadband piezoelectric based vibration energy harvester with a triple-well potential induced by a magnetic field was proposed and the parameters of the linear energy harvesting system without magnetic force actuation were obtained through intelligent optimization of the minimum error between numerical simulations and experimental responses.
483 citations
TL;DR: In this paper, a spherical three-dimensional triboelectric nanogenerator (3D-TENG) with a single electrode is designed, consisting of an outer transparent shell and an inner polyfluoroalkoxy (PFA) ball.
Abstract: A spherical three-dimensional triboelectric nanogenerator (3D-TENG) with a single electrode is designed, consisting of an outer transparent shell and an inner polyfluoroalkoxy (PFA) ball. Based on the coupling of triboelectric effect and electrostatic effect, the rationally developed 3D-TENG can effectively scavenge ambient vibration energy in full space by working at a hybridization of both the contact-separation mode and the sliding mode, resulting in the electron transfer between the Al electrode and the ground. By systematically investigating the output performance of the device vibrating under different frequencies and along different directions, the TENG can deliver a maximal output voltage of 57 V, a maximal output current of 2.3 μA, and a corresponding output power of 128 μW on a load of 100 MΩ, which can be used to directly drive tens of green light-emitting diodes. Moreover, the TENG is utilized to design the self-powered acceleration sensor with detection sensitivity of 15.56 V g-1. This work opens up many potential applications of single-electrode based TENGs for ambient vibration energy harvesting techniques in full space and the self-powered vibration sensor systems.
364 citations
TL;DR: The question of power conversion is addressed by reviewing various circuit solutions and the work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions.
Abstract: This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions.
339 citations
TL;DR: This paper addresses the fundamental tradeoffs for maximizing energy efficiency (EE) versus spectrum efficiency (SE) for a point-to-point additive white Gaussian noise (AWGN) channel with the transmitter powered solely via energy harvesting from the environment and proposes a new online algorithm under the practical setup with only the past and present energy state information (ESI) known at the transmitter.
Abstract: Characterizing the fundamental tradeoffs for maximizing energy efficiency (EE) versus spectrum efficiency (SE) is a key problem in wireless communication. In this paper, we address this problem for a point-to-point additive white Gaussian noise (AWGN) channel with the transmitter powered solely via energy harvesting from the environment. In addition, we assume a practical on-off transmitter model with non-ideal circuit power, i.e., when the transmitter is on, its consumed power is the sum of the transmit power and a constant circuit power. Under this setup, we study the optimal transmit power allocation to maximize the average throughput over a finite horizon, subject to the time-varying energy constraint and the non-ideal circuit power consumption. First, we consider the off-line optimization under the assumption that the energy arrival time and amount are a priori known at the transmitter. Although this problem is non-convex due to the non-ideal circuit power, we show an efficient optimal solution that in general corresponds to a two-phase transmission: the first phase with an EE-maximizing on-off power allocation, and the second phase with a SE-maximizing power allocation that is non-decreasing over time, thus revealing an interesting result that both the EE and SE optimizations are unified in an energy harvesting communication system. We then extend the optimal off-line algorithm to the case with multiple parallel AWGN channels, based on the principle of nested optimization. Finally, inspired by the off-line optimal solution, we propose a new online algorithm under the practical setup with only the past and present energy state information (ESI) known at the transmitter.
TL;DR: In this article, an inertial device that combines the frequency up-conversion principle with a rotating proof mass was presented for energy harvesting from human motion, in the form of piezoelectric beam plucking through magnetic coupling.
Abstract: Energy harvesting from human motion faces the challenges of low frequency and random excitation. One strategy that has been successful in the past is frequency up-conversion. This paper introduces an inertial device that combines this principle, in the form of piezoelectric beam plucking through magnetic coupling with a rotating proof mass. The advantages rotational systems can have for body movements are discussed. The prototype is described and tested in a real world environment during a running race and later on in a laboratory environment on a custom built linear excitation table. Throughout these tests it is confirmed that such a device can operate over a broad range of frequencies and under varying orientations, making it suitable for this intended application. Across frequencies between 0.5 and 4 Hz and accelerations between 1 and 20 m/s2 power outputs in the range of tens of microwatts were achieved, with a peak value of 43 μW at 2 Hz and 20 m/s2 when the rotor went into a continuous rotation.
TL;DR: A comprehensive review on the history and current state-of-the art of piezoelectric energy harvesting is presented and the issues that need to be addressed for realization of practical piezOElectricEnergy harvesting devices are discussed.
Abstract: Piezoelectric energy harvesting has attracted wide attention from researchers especially in the last decade due to its advantages such as high power density, architectural simplicity, and scalability. As a result, the number of studies on piezoelectric energy harvesting published in the last 5 years is more than twice the sum of publications on its electromagnetic and electrostatic counterparts. This paper presents a comprehensive review on the history and current state-of-the art of piezoelectric energy harvesting. A brief theory section presents the basic principles of piezoelectric energy conversion and introduces the most commonly used mechanical architectures. The theory section is followed by a literature survey on piezoelectric energy harvesters, which are classified into three groups: (i) macro- and mesoscale, (ii) MEMS scale, and (iii) nanoscale. The size of a piezoelectric energy harvester affects a variety of parameters such as its weight, fabrication method, achievable power output level, and potential application areas. Consequently, size-based classification provides a reliable and effective basis to study various piezoelectric energy harvesters. The literature survey on each scale group is concluded with a summary, potential application areas, and future directions. In a separate section, the most prominent challenges in piezoelectric energy harvesting and the studies focusing on these challenges are discussed. The conclusion part summarizes the current standing of piezoelectric energy harvesters as possible candidates for various applications and discusses the issues that need to be addressed for realization of practical piezoelectric energy harvesting devices.
TL;DR: In this article, a beam-based paradigmatical design was proposed for flexoelectric energy harvesting under harmonic mechanical excitation. And the authors showed that the output power density and conversion efficiency increase significantly when the beam thickness reduces from micro-to nanoscale and flexolectricity-based energy harvesting can be a viable alternative to piezoelectrics.
TL;DR: In this article, the authors present the state of the art of the application of energy harvesting in commercial and residential buildings and show that typical harvested powers are: (1) indoor solar cell (active area of 9 cm2, volume of 2.88 cm3): 2 µW from a vibration acceleration of 0.25 m s−2 at 45 Hz; (2) thermoelectric harvester (volume of 1.4 cm3), 6 mW from thermal gradient of 25 °C; (3) periodic kinetic energy harvesters, (4) electromagnetic
Abstract: This review presents the state of the art of the application of energy harvesting in commercial and residential buildings. Electromagnetic (optical and radio frequency), kinetic, thermal and airflow-based energy sources are identified as potential energy sources within buildings and the available energy is measured in a range of buildings. Suitable energy harvesters are discussed and the available and the potential harvested energy calculated. Calculations based on these measurements, and the technical specifications of state-of-the-art harvesters, show that typical harvested powers are: (1) indoor solar cell (active area of 9 cm2, volume of 2.88 cm3): ~300 µW from a light intensity of 1000 lx; (2) thermoelectric harvester (volume of 1.4 cm3): 6 mW from a thermal gradient of 25 °C; (3) periodic kinetic energy harvester (volume of 0.15 cm3): 2 µW from a vibration acceleration of 0.25 m s−2 at 45 Hz; (4) electromagnetic wave harvester (13 cm antenna length and conversion efficiency of 0.7): 1 µW with an RF source power of −25 dBm; and (5) airflow harvester (wind turbine blade of 6 cm diameter and generator efficiency of 0.41): 140 mW from an airflow of 8 m s−1. These results highlight the high potential of energy harvesting technology in buildings and the relative attractions of various harvester technologies. The harvested power could either be used to replace batteries or to prolong the life of rechargeable batteries for low-power (~1 mW) electronic devices.
TL;DR: In this article, a knitted single-structure piezoelectric generator consisting of high β-phase (∼80%) polyamide multifilaments as the spacer yarn interconnected between silver (Ag) coated polyamide multilament yarn layers acting as the top and bottom electrodes is presented.
Abstract: The piezoelectric effect in poly(vinylidene fluoride), PVDF, was discovered over four decades ago and since then, significant work has been carried out aiming at the production of high β-phase fibres and their integration into fabric structures for energy harvesting. However, little work has been done in the area of production of “true piezoelectric fabric structures” based on flexible polymeric materials such as PVDF. In this work, we demonstrate “3D spacer” technology based all-fibre piezoelectric fabrics as power generators and energy harvesters. The knitted single-structure piezoelectric generator consists of high β-phase (∼80%) piezoelectric PVDF monofilaments as the spacer yarn interconnected between silver (Ag) coated polyamide multifilament yarn layers acting as the top and bottom electrodes. The novel and unique textile structure provides an output power density in the range of 1.10–5.10 μW cm−2 at applied impact pressures in the range of 0.02–0.10 MPa, thus providing significantly higher power outputs and efficiencies over the existing 2D woven and nonwoven piezoelectric structures. The high energy efficiency, mechanical durability and comfort of the soft, flexible and all-fibre based power generator are highly attractive for a variety of potential applications such as wearable electronic systems and energy harvesters charged from the ambient environment or by human movement.
TL;DR: In this article, the authors considered a multiantenna system where the receiver should harvest energy from the transmitter by wireless energy transfer to support its wireless information transmission, and they derived two wireless energy and information transfer tradeoff schemes by maximizing an upper bound and an approximate lower bound of the average information transmission rate.
Abstract: In this paper, we consider a multiantenna system where the receiver should harvest energy from the transmitter by wireless energy transfer to support its wireless information transmission. To maximize the harvesting energy, we propose the performance of adaptive energy beamforming according to the instantaneous channel state information (CSI). To help the transmitter obtain the CSI for energy beamforming, we further propose a win-win CSI quantization feedback strategy to improve the efficiencies of both power and information transmission. The focus of this paper is on the tradeoff of wireless energy and information transfer by adjusting the transfer duration with a total duration constraint. By revealing the relationship between transmit power, transfer duration, and feedback amount, we derive two wireless energy and information transfer tradeoff schemes by maximizing an upper bound and an approximate lower bound of the average information transmission rate, respectively. Moreover, the impact of imperfect CSI at the receiver is investigated, and the corresponding wireless energy and information transfer tradeoff scheme is also given. Finally, numerical results validate the effectiveness of the proposed schemes.
TL;DR: This article provides an overview of the RF-powered CRNs and discusses the challenges that arise for dynamic spectrum access in these networks, and focuses on the trade-off among spectrum sensing, data transmission, and RF energy harvesting.
Abstract: Spectrum efficiency and energy efficiency are two critical issues in designing wireless networks. Through dynamic spectrum access, cognitive radios can improve the spectrum efficiency and capacity of wireless networks. On the other hand radio frequency (RF) energy harvesting has emerged as a promising technique to supply energy to wireless networks and thereby increase their energy efficiency. Therefore, to achieve both spectrum and energy efficiencies, the secondary users in a cognitive radio network (CRN) can be equipped with the RF energy harvesting capability, and such a network can be referred to as an RF-powered cognitive radio network. In this article we provide an overview of the RF-powered CRNs and discuss the challenges that arise for dynamic spectrum access in these networks. Focusing on the trade-off among spectrum sensing, data transmission, and RF energy harvesting, we then discuss the dynamic channel selection problem in a multi-channel RF-powered CRN. In the RF-powered CRN a secondary user can adaptively select a channel to transmit data when the channel is not occupied by any primary user. Alternatively, the secondary user can harvest RF energy for data transmission if the channel is occupied. The optimal channel selection policy of the secondary user can be obtained by formulating a Markov decision process (MDP) problem. We present some numerical results obtained by solving this MDP problem.
TL;DR: The TENG is invented that is based on a wavy-structured Cu-Kapton-Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect, and it is proved to be a much more efficient friction mode for energy harvesting.
Abstract: We invented a triboelectric nanogenerator (TENG) that is based on a wavy-structured Cu–Kapton–Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect. This structure design allows the TENG to be self-restorable after impact without the use of extra springs and converts direct impact into lateral sliding, which is proved to be a much more efficient friction mode for energy harvesting. The working mechanism has been elaborated using the capacitor model and finite-element simulation. Vibrational energy from 5 to 500 Hz has been harvested, and the generator’s resonance frequency was determined to be ∼100 Hz at a broad full width at half-maximum of over 100 Hz, producing an open-circuit voltage of up to 72 V, a short-circuit current of up to 32 μA, and a peak power density of 0.4 W/m2. Most importantly, the wavy structure of the TENG can be easily packaged for harvesting the impact energy from wa...
TL;DR: In this paper, the concept of an acoustic black hole (ABH) is explored as a main design framework for performing dynamic structural tailoring of mechanical systems for vibration energy harvesting applications.
Abstract: This paper explores the concept of an acoustic black hole (ABH) as a main design framework for performing dynamic structural tailoring of mechanical systems for vibration energy harvesting applications. The ABH is an integral feature embedded in the host structure that allows for a smooth reduction of the phase velocity, theoretically approaching zero, while minimizing the reflected energy. This mechanism results in structural areas with high energy density that can be effectively exploited to develop enhanced vibration-based energy harvesting. Fully coupled electro-mechanical models of an ABH tapered structure with surface mounted piezo-transducers are developed to numerically simulate the response of the system to both steady state and transient excitations. The design performances are numerically evaluated using structural intensity data as well as the instantaneous voltage/power and energy output produced by the piezo-transducer network. Results show that the dynamically tailored structural design enables a drastic increase in the harvested energy as compared to traditional structures, both under steady state and transient excitation conditions.
TL;DR: The fabrication and performance of a wearable biofuel cell printed directly onto textile substrates and such textile-based non-invasive biofuel cells can be expected to serve in the future as the power unit for wearable electronics and biomedical devices.
Abstract: The fabrication and performance of a wearable biofuel cell printed directly onto textile substrates are reported. The textile biofuel cell utilizes physiologically produced sweat lactate as the fuel to generate electrical energy, producing up to 100 μW cm−2 at 0.34 V during in vitro experimentation, even after repeated bending stress. Furthermore, the wearable and flexible biofuel cell can be easily integrated with a portable energy storage device for on-demand powering of wearable electronics. To validate energy harvesting, the biofuel cell is integrated into a headband and a wristband, and with the help of an on-board DC/DC converter, extracts energy from perspiring human subjects for direct powering of an LED or a digital watch. Convenient incorporation and removal from a variety of garments are achieved by printing the biofuel cell on a detachable care label. Such textile-based non-invasive biofuel cells can be expected to serve in the future as the power unit for wearable electronics and biomedical devices.
Posted Content•
TL;DR: This paper surveys the energy-efficient CR techniques and the optimization of green-energy-powered wireless networks, and discusses research challenges in designing CR networks that are powered by energy harvesters.
Abstract: Green energy powered cognitive radio (CR) network is capable of liberating the wireless access networks from spectral and energy constraints. The limitation of the spectrum is alleviated by exploiting cognitive networking in which wireless nodes sense and utilize the spare spectrum for data communications, while dependence on the traditional unsustainable energy is assuaged by adopting energy harvesting (EH) through which green energy can be harnessed to power wireless networks. Green energy powered CR increases the network availability and thus extends emerging network applications. Designing green CR networks is challenging. It requires not only the optimization of dynamic spectrum access but also the optimal utilization of green energy. This paper surveys the energy efficient cognitive radio techniques and the optimization of green energy powered wireless networks. Existing works on energy aware spectrum sensing, management, and sharing are investigated in detail. The state of the art of the energy efficient CR based wireless access network is discussed in various aspects such as relay and cooperative radio and small cells. Envisioning green energy as an important energy resource in the future, network performance highly depends on the dynamics of the available spectrum and green energy. As compared with the traditional energy source, the arrival rate of green energy, which highly depends on the environment of the energy harvesters, is rather random and intermittent. To optimize and adapt the usage of green energy according to the opportunistic spectrum availability, we discuss research challenges in designing cognitive radio networks which are powered by energy harvesters.
TL;DR: In this paper, a piezoelectric NEMS vibrational energy harvester is fabricated through the development of a synthesis process for vertically aligned barium titanate (BaTiO3) nanowire (NW) arrays directly on a conductive substrate.
Abstract: Nano-electromechanical systems (NEMS) developed using piezoelectric nanowires (NWs) have gained immense interest in energy harvesting applications as they are able to convert several different forms of mechanical energy sources into electric power and thereby function as reliable power sources for ultra-low power wireless electronics. In this work, a piezoelectric NEMS vibrational energy harvester is fabricated through the development of a synthesis process for vertically aligned barium titanate (BaTiO3) nanowire (NW) arrays directly on a conductive substrate. These poled ferroelectric NW arrays are characterized through direct vibration excitation and demonstrated to provide efficient harvesting of mechanical vibrational energy producing an average power density of ∼6.27 μW cm−3 from 1g acceleration. In order to substantiate the superior energy harvesting performance of the newly developed BaTiO3 NW arrays, a direct comparison is made with conventional ZnO NW arrays. Here, we clearly report that the ferroelectric BaTiO3 NW NEMS energy harvester has ∼16 times greater power density than the ZnO NW NEMS energy harvester from the same acceleration input.
TL;DR: A 0.25 cm3 autonomous energy harvesting micro-platform is realized to efficiently scavenge, rectify and store ambient vibration energy with batteryless cold start-up and zero sleep-mode power consumption.
Abstract: A 025 cm
3
autonomous energy harvesting micro-platform is realized to efficiently scavenge, rectify and store ambient vibration energy with batteryless cold start-up and zero sleep-mode power consumption The fabricated compact system integrates a high-performance vacuum-packaged piezoelectric MEMS energy harvester with a power management IC and surface-mount components including an ultra-capacitor The power management circuit incorporates a rectification stage with ~30 mV voltage drop, a bias-Ωip stage with a novel control system for increased harvesting efficiency, a trickle charger for permanent storage of harvested energy, and a low power supply-independent bias circuitry The overall system weighs less than 06 grams, does not require a precharged battery, and has power consumption of 05 μW in active-mode and 10 pW in sleep-mode operation While excited with 1 g vibration, the platform is tested to charge an initially depleted 70 mF ultra-capacitor to 185 V in 50 minutes (at 155 Hz vibration), and a 20 mF ultra-capacitor to 135 V in 75 min (at 419 Hz) The end-to-end rectification efficiency from the harvester to the ultra-capacitor is measured as 58-86% The system can harvest from a minimum vibration level of 01 g
TL;DR: The energy harvesters here reported produce a power between 6 nW and 7.2 mW; these values are comparable with the supply requirements of the most common implantablemedical devices; this demonstrates that energy harvesting techniques is a valid solution to design batteryless implantable medical devices.
Abstract: Implantable medical devices usually require a battery to operate and this can represent a severe restriction. In most cases, the implantable medical devices must be surgically replaced because of the dead batteries; therefore, the longevity of the whole implantable medical device is determined by the battery lifespan. For this reason, researchers have been studying energy harvesting techniques from the human body in order to obtain batteryless implantable medical devices. The human body is a rich source of energy and this energy can be harvested from body heat, breathing, arm motion, leg motion or the motion of other body parts produced during walking or any other activity. In particular, the main human-body energy sources are kinetic energy and thermal energy. This paper reviews the state-of-art in kinetic and thermoelectric energy harvesters for powering implantable medical devices. Kinetic energy harvesters are based on electromagnetic, electrostatic and piezoelectric conversion. The different energy harvesters are analyzed highlighting their sizes, energy or power they produce and their relative applications. As they must be implanted, energy harvesting devices must be limited in size, typically about 1 cm 3 . The available energy depends on human-body positions; therefore, some positions are more advantageous than others. For example, favorable positions for piezoelectric harvesters are hip, knee and ankle where forces are significant. The energy harvesters here reported produce a power between 6 nW and 7.2 mW; these values are comparable with the supply requirements of the most common implantable medical devices; this demonstrates that energy harvesting techniques is a valid solution to design batteryless implantable medical devices.
24 Dec 2014
TL;DR: The maximum output current was improved by 240% as compared to the conventional charge pump design using only the forward body bias, and the low-power adaptive dead-time (AD) circuit is used.
Abstract: Design of low-voltage and efficient energy-harvesting circuits is becoming increasingly important, particularly, for autonomous systems. Since the amount of energy that can be harvested from the surrounding environment is limited, the available output voltage of a harvester is low. Therefore, the design of a low-input-voltage (low-VIN) up-converter is critical to self-powered systems [1-3]. Moreover, the form factor is very constrained in applications such as wearable electronic devices and sensor networks. Recently, low-VIN charge pumps (CPs) for energy harvesting has been compared with DC-DC converters using a large inductor [1-3]. CPs introduced in [1] and [2] use the advanced process technology to push VIN down to the subthreshold region. The CP in [1] introduces a forward-body-biasing (FBB) technique, which improves the voltage conversion efficiency (VCE) for low VIN but shows poor power conversion efficiency (PCE). The CP in [2] achieves the lowest operation voltage. However, the design with a 10-stage CP provides low output power. This paper presents a CP with switching-body-biasing (SBB), adaptive-dead-time (AD), and switch-conductance (SW-G) enhancement techniques to improve the PCE for low VIN as well as to extend the maximum load current.
19 Sep 2014
TL;DR: This work presents the details of the nanowatt PMU required to power the electronics and focuses on the low-power circuit design techniques needed to realize a nW power converter that is applicable to a broad spectrum of emerging biomedical applications with ultra-low energy-harvesting sources.
Abstract: A wireless sensor that is powered from the endocochlear potential (EP), a 70-to-100mV bio-potential inside the mammalian ear, has been demonstrated in [1]. Due to the anatomical size and physiological constraints inside the ear, a maximum of 1.1 to 6.25nW can be extracted from the EP. The nanowatt power budget of the sensor gives rise to unique challenges with power conversion efficiency and quiescent current reduction in the power management unit (PMU). While [1] presents the system aspects of the biomedical harvesting including the biologic interface and system measurements, this work presents the details of the nanowatt PMU required to power the electronics. More specifically, it focuses on the low-power circuit design techniques needed to realize a nW power converter that is applicable to a broad spectrum of emerging biomedical applications with ultra-low energy-harvesting sources.
TL;DR: This study concludes that the system is applicable to wireless tire sensor systems after making minor improvements and ascertained that the use of a strain field is suitable for this purpose.
TL;DR: This work addresses design and implementation issues of a 24 GHz rectenna, which is developed to demonstrate the feasibility of wireless power harvesting and transmission techniques towards millimeter-wave regime.
Abstract: This work addresses design and implementation issues of a 24 GHz rectenna, which is developed to demonstrate the feasibility of wireless power harvesting and transmission (WPT) techniques towards millimeter-wave regime. The proposed structure includes a compact circularly polarized substrate integrated waveguide (SIW) cavity-backed antenna array integrated with a self-biased rectifier using commercial Schottky diodes. The antenna and the rectifier are individually designed, optimized, fabricated and measured. Then they are integrated into one circuit in order to validate the studied rectenna architecture. The maximum measured conversion efficiency and DC voltage are respectively equal to 24% and 0.6 V for an input power density of 10 mW/cm
2
.
TL;DR: The goal of this survey is to present a comprehensive review of the recent literature on the various possible energy harvesting technologies from ambient environment for WSNs.
Abstract: In recent years, wireless sensor networks (WSNs) have grown dramatically and made a great progress in many applications. But having limited life, batteries, as the power sources of wireless sensor nodes, have restricted the development and application of WSNs which often requires a very long lifespan for better performance. In order to make the WSNs prevalent in our lives, an alternative energy source is required. Environmental energy is an attractive power source, and it provides an approach to make the sensor nodes self-powered with the possibility of an almost infinite lifetime. The goal of this survey is to present a comprehensive review of the recent literature on the various possible energy harvesting technologies from ambient environment for WSNs.