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Showing papers on "Energy harvesting published in 2015"


Journal ArticleDOI
TL;DR: This paper presents an overview of the RF-EHNs including system architecture, RF energy harvesting techniques, and existing applications, and explores various key design issues according to the network types, i.e., single-hop networks, multiantenna networks, relay networks, and cognitive radio networks.
Abstract: Radio frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to power the next-generation wireless networks As this emerging technology enables proactive energy replenishment of wireless devices, it is advantageous in supporting applications with quality-of-service requirements In this paper, we present a comprehensive literature review on the research progresses in wireless networks with RF energy harvesting capability, which is referred to as RF energy harvesting networks (RF-EHNs) First, we present an overview of the RF-EHNs including system architecture, RF energy harvesting techniques, and existing applications Then, we present the background in circuit design as well as the state-of-the-art circuitry implementations and review the communication protocols specially designed for RF-EHNs We also explore various key design issues in the development of RF-EHNs according to the network types, ie, single-hop networks, multiantenna networks, relay networks, and cognitive radio networks Finally, we envision some open research directions

2,352 citations


Journal ArticleDOI
TL;DR: The current state of the art for wireless networks composed of energy harvesting nodes, starting from the information-theoretic performance limits to transmission scheduling policies and resource allocation, medium access, and networking issues are provided.
Abstract: This paper summarizes recent contributions in the broad area of energy harvesting wireless communications. In particular, we provide the current state of the art for wireless networks composed of energy harvesting nodes, starting from the information-theoretic performance limits to transmission scheduling policies and resource allocation, medium access, and networking issues. The emerging related area of energy transfer for self-sustaining energy harvesting wireless networks is considered in detail covering both energy cooperation aspects and simultaneous energy and information transfer. Various potential models with energy harvesting nodes at different network scales are reviewed, as well as models for energy consumption at the nodes.

829 citations


Journal ArticleDOI
TL;DR: A novel integrated power unit realizes both energy harvesting and energy storage by a textile triboelectric nanogenerator (TENG)-cloth and a flexible lithium-ion battery (LIB) belt, respectively.
Abstract: A novel integrated power unit realizes both energy harvesting and energy storage by a textile triboelectric nanogenerator (TENG)-cloth and a flexible lithium-ion battery (LIB) belt, respectively. The mechanical energy of daily human motion is converted into electricity by the TENG-cloth, sustaining the energy of the LIB belt to power wearable smart electronics.

629 citations


Journal ArticleDOI
TL;DR: In this paper, the authors provide detailed design guidelines regarding the properties of the material, device dimensions, and gap fillers by performing realistic device simulations with important parasitic losses taken into account and discuss the feasibility of scalable and cost-effective manufacturing of thermoelectric energy harvesting devices with desired dimensions.
Abstract: In this paper, we review recent advances in the development of flexible thermoelectric materials and devices for wearable human body-heat energy harvesting applications. We identify various emerging applications such as specialized medical sensors where wearable thermoelectric generators can have advantages over other energy sources. To meet the performance requirements for these applications, we provide detailed design guidelines regarding the properties of the material, device dimensions, and gap fillers by performing realistic device simulations with important parasitic losses taken into account. For this, we review recently emerging flexible thermoelectric materials suited for wearable applications, such as polymer-based materials and screen-printed paste-type inorganic materials. A few examples among these materials are selected for thermoelectric device simulations in order to find optimal design parameters for wearable applications. Finally we discuss the feasibility of scalable and cost-effective manufacturing of thermoelectric energy harvesting devices with desired dimensions.

497 citations


Journal ArticleDOI
26 Feb 2015-ACS Nano
TL;DR: Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, the TENG-NW renders an innovative and effective approach toward large-scale blue energy harvesting from the ocean.
Abstract: With 70% of the earth’s surface covered with water, wave energy is abundant and has the potential to be one of the most environmentally benign forms of electric energy. However, owing to lack of effective technology, water wave energy harvesting is almost unexplored as an energy source. Here, we report a network design made of triboelectric nanogenerators (TENGs) for large-scale harvesting of kinetic water energy. Relying on surface charging effect between the conventional polymers and very thin layer of metal as electrodes for each TENG, the TENG networks (TENG-NW) that naturally float on the water surface convert the slow, random, and high-force oscillatory wave energy into electricity. On the basis of the measured output of a single TENG, the TENG-NW is expected to give an average power output of 1.15 MW from 1 km2 surface area. Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, ...

444 citations


Journal ArticleDOI
TL;DR: The excellent performance of the hybrid cell enhances the energy-harvesting efficiency significantly, and enables self-powered sensing, which will lead to a variety of advanced applications.
Abstract: A triboelectric-pyroelectric-piezoelectric hybrid cell, consisting of a triboelectric nanogenerator and a pyroelectric-piezoelectric nanogenerator, is developed for highly efficient mechanical energy harvesting through multiple mechanisms. The excellent performance of the hybrid cell enhances the energy-harvesting efficiency significantly (by 26.2% at 1 kΩ load resistance), and enables self-powered sensing, which will lead to a variety of advanced applications.

392 citations


Journal ArticleDOI
TL;DR: In this paper, a rolling-structured TENG is demonstrated to be capable of harvesting blue energy from oceans and lakes using a rolling ball inside a rocking spherical shell, with a peak current of 1 μA over a wide load range from a short-circuit condition to 10 GΩ with an instantaneous output power of up to 10 mW.
Abstract: Water waves are increasingly regarded as a promising source for large-scale energy applications. Triboelectric nanogenerators (TENGs) have been recognized as one of the most promising approaches for harvesting wave energy. This work examines a freestanding, fully enclosed TENG that encloses a rolling ball inside a rocking spherical shell. Through the optimization of materials and structural parameters, a spherical TENG of 6 cm in diameter actuated by water waves can provide a peak current of 1 μA over a wide load range from a short-circuit condition to 10 GΩ, with an instantaneous output power of up to 10 mW. A multielectrode arrangement is also studied to improve the output of the TENG under random wave motions from all directions. Moreover, at a frequency of 1.43 Hz, the wave-driven TENG can directly drive tens of LEDs and charge a series of supercapacitors to rated voltage within several hours. The stored energy can power an electronic thermometer for 20 min. This rolling-structured TENG is extremely lightweight, has a simple structure, and is capable of rocking on or in water to harvest wave energy; it provides an innovative and effective approach toward large-scale blue energy harvesting of oceans and lakes.

356 citations


Journal ArticleDOI
TL;DR: A novel two-phase protocol for efficient energy transfer and information relaying, in which the relay operates in full-duplex mode with simultaneous energy harvesting and information transmission, and enables the so-called self-energy recycling.
Abstract: This letter studies a wireless-powered amplify-and-forward relaying system, where an energy-constrained relay node assists the information transmission from the source to the destination using the energy harvested from the source. We propose a novel two-phase protocol for efficient energy transfer and information relaying, in which the relay operates in full-duplex mode with simultaneous energy harvesting and information transmission . Compared with the existing protocols, the proposed design possesses two main advantages: 1) it ensures uninterrupted information transmission since no time switching or power splitting is needed at the relay for energy harvesting; and 2) it enables the so-called self-energy recycling, i.e., part of the energy (loop energy) that is used for information transmission by the relay can be harvested and reused in addition to the dedicated energy sent by the source. Under the multiple-input single-output (MISO) channel setup, the optimal power allocation and beamforming design at the relay are derived. Numerical results show a significant throughput gain achieved by our proposed design over the existing time switching based relay protocol.

314 citations


Journal ArticleDOI
TL;DR: A survey on potential renewable energy resources along with their characteristics and applications in WSN and various battery recharging techniques and their applications with respect to WSN are presented.
Abstract: In recent years there has been several technological advances in Wireless Sensor Networks (WSN), but energy still remains a paramount resource. The amount of available energy has a direct effect on the performance, functionality and lifetime of WSN. Being bound by cost and size, sensor nodes are usually equipped with limited amount of energy and therefore requires a replacement of batteries occasionally. But replacement might not always be feasible option and in some scenarios might even be prohibitive. This indicates the need for more viable solutions, these involve generating energy at the sensor nodes or have it delivered to them i.e., energy harvesting or wireless energy transfer. The objective of this paper is threefold: first we present a survey on potential renewable energy resources along with their characteristics and applications in WSN. Second, this study also describes various battery recharging techniques and their applications with respect to WSN. Finally, we discuss formidable issues, challenges and future research directions.

269 citations


Journal ArticleDOI
TL;DR: In this article, a comprehensive literature review has been presented on vibration based micro power generation using two most common transducer mechanisms: electromagnetic and piezoelectric transduction systems.

230 citations


Proceedings ArticleDOI
09 Mar 2015
TL;DR: The simulation platform in this paper is calibrated using measured results from a fabricated nonvolatile processor and used to explore the design space for a nonVolatile processor with different architectures, different input power sources, and policies for maximizing forward progress.
Abstract: Energy harvesting has been widely investigated as a promising method of providing power for ultra-low-power applications. Such energy sources include solar energy, radio-frequency (RF) radiation, piezoelectricity, thermal gradients, etc. However, the power supplied by these sources is highly unreliable and dependent upon ambient environment factors. Hence, it is necessary to develop specialized systems that are tolerant to this power variation, and also capable of making forward progress on the computation tasks. The simulation platform in this paper is calibrated using measured results from a fabricated nonvolatile processor and used to explore the design space for a nonvolatile processor with different architectures, different input power sources, and policies for maximizing forward progress.

Journal ArticleDOI
TL;DR: This work demonstrates a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectrics generator, derived from the simultaneous use of piezOElectric and triboelectedric mechanisms in one press-and-release cycle.
Abstract: Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA · cm(-2), and average power density of ~4.44 mW · cm(-2). The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics.

Journal ArticleDOI
TL;DR: In this article, the authors characterize the energy availability associated with specific human activities (e.g., relaxing, walking, cycling) and develop energy allocation algorithms that take into account practical IoT node design considerations, and evaluate the algorithms using the collected measurements.
Abstract: Numerous energy harvesting wireless devices that will serve as building blocks for the Internet of Things (IoT) are currently under development. However, there is still only limited understanding of the properties of various energy sources and their impact on energy harvesting adaptive algorithms. Hence, we focus on characterizing the kinetic (motion) energy that can be harvested by a wireless node with an IoT form factor and on developing energy allocation algorithms for such nodes. In this paper, we describe methods for estimating harvested energy from acceleration traces. To characterize the energy availability associated with specific human activities (e.g., relaxing, walking, cycling), we analyze a motion dataset with over 40 participants. Based on acceleration measurements that we collected for over 200 hours, we study energy generation processes associated with day-long human routines. We also briefly summarize our experiments with moving objects. We develop energy allocation algorithms that take into account practical IoT node design considerations, and evaluate the algorithms using the collected measurements. Our observations provide insights into the design of motion energy harvesters, IoT nodes, and energy harvesting adaptive algorithms.

Journal ArticleDOI
TL;DR: The presented theory is supported with an experimental implementation of orthogonal frequency division multiplexing (OFDM), thus, proving the validity of the analysis and demonstrating the feasibility of the proposed receiver.
Abstract: This paper proposes a novel design of an optical wireless communications (OWC) receiver using a solar panel as a photodetector. The proposed system is capable of simultaneous data transmission and energy harvesting. The solar panel can convert a modulated light signal into an electrical signal without any external power requirements. Furthermore, the direct current (DC) component of the modulated light can be harvested in the proposed receiver. The generated energy can potentially be used to power a user terminal or at least to prolong its operation time. The current work discusses the various parameters which need to be considered in the design of a system using a solar panel for simultaneous communication and energy harvesting. The presented theory is supported with an experimental implementation of orthogonal frequency division multiplexing (OFDM), thus, proving the validity of the analysis and demonstrating the feasibility of the proposed receiver. Using the propounded system, a communication link with a data rate of 11.84 Mbps is established for a received optical signal with a peak-to-peak amplitude of $\hbox{0.7}\times \hbox{10}^{-3}\ \hbox{W}/\hbox{cm}^{2}$ .

Journal ArticleDOI
TL;DR: In this paper, a metamaterial medium for electromagnetic energy harvesting based on the full absorption concept is proposed, where the power absorption is mostly dissipated across a resistive load instead of the dielectric substrate.
Abstract: We present the design of a metamaterial medium for electromagnetic energy harvesting based on the full absorption concept. A metamaterial slab was designed comprising 13 × 13 electrically small cells, each loaded with an 82 Ω resistor which mimics the input impedance of a rectification circuitry. Unlike earlier designs of metamaterial absorbers, here the power absorption is mostly dissipated across a resistive load instead of the dielectric substrate. This implies that effective electromagnetic energy harvesting can be achieved. The power is channeled through a via connected to each cell. For a design optimized at 3 GHz, simulation and experimental results show power absorption efficiency of 97% and 93%, respectively.

Journal ArticleDOI
K Ylli, D Hoffmann, A Willmann, Philipp Becker, Bernd Folkmer, Yiannos Manoli1 
TL;DR: In this paper, the authors presented the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait and achieved an average power output of up to 0.84 mW with two test subjects on a treadmill.
Abstract: Modern compact and low power sensors and systems are leading towards increasingly integrated wearable systems. One key bottleneck of this technology is the power supply. The use of energy harvesting techniques offers a way of supplying sensor systems without the need for batteries and maintenance. In this work we present the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait. A multi-coil topology harvester is presented which uses the swing motion of the foot. The second device is a shock-type harvester which is excited into resonance upon heel strike. Both devices were modeled and designed with the key constraint of device height in mind, in order to facilitate the integration into the shoe sole. The devices were characterized under different motion speeds and with two test subjects on a treadmill. An average power output of up to 0.84 mW is achieved with the swing harvester. With a total device volume including the housing of 21 cm3 a power density of 40 μW cm−3 results. The shock harvester generates an average power output of up to 4.13 mW. The power density amounts to 86 μW cm−3 for the total device volume of 48 cm3. Difficulties and potential improvements are discussed briefly.

Journal ArticleDOI
TL;DR: An interference aided energy harvesting scheme is proposed for cooperative relaying systems, where energy-constrained relays harvest energy from the received information signal and co-channel interference signals, and then use that harvested energy to forward the correctly decoded signal to the destination.
Abstract: Radio-frequency energy harvesting constitutes an effective way to prolong the lifetime of wireless networks, wean communication devices off the battery and power line, benefit the energy saving and lower the carbon footprint of wireless communications. In this paper, an interference aided energy harvesting scheme is proposed for cooperative relaying systems, where energy-constrained relays harvest energy from the received information signal and co-channel interference signals, and then use that harvested energy to forward the correctly decoded signal to the destination. The time-switching scheme (TS), in which the receiver switches between decoding information and harvesting energy, as well as the power-splitting scheme (PS), where a portion of the received power is used for energy harvesting and the remaining power is utilized for information processing, are adopted separately. Applying the proposed energy harvesting approach to a decode-and-forward relaying system with the three-terminal model, the analytical expressions of the ergodic capacity and the outage capacity are derived, and the corresponding achievable throughputs are determined. Comparative results are provided and show that PS is superior to TS at high signal-to-noise ratio (SNR) in terms of throughput, while at low SNR, TS outperforms PS. Furthermore, considering different interference power distributions with equal aggregate interference power at the relay, the corresponding system capacity relationship, i.e., the ordering of capacities, is obtained.

Journal ArticleDOI
TL;DR: This work analyzes the on-demand mobile charging problem using a simple but efficient Nearest-Job-Next with Preemption (NJNP) discipline for the mobile charger, and provides analytical results on the system throughput and charging latency from the perspectives of theMobile charger and individual sensor nodes, respectively.
Abstract: Recently, adopting mobile energy chargers to replenish the energy supply of sensor nodes in wireless sensor networks has gained increasing attention from the research community. Different from energy harvesting systems, the utilization of mobile energy chargers is able to provide more reliable energy supply than the dynamic energy harvested from the surrounding environment. While pioneering works on the mobile recharging problem mainly focus on the optimal offline path planning for the mobile chargers, in this work, we aim to lay the theoretical foundation for the on-demand mobile charging (DMC) problem, where individual sensor nodes request charging from the mobile charger when their energy runs low. Specifically, in this work, we analyze the on-demand mobile charging problem using a simple but efficient Nearest-Job-Next with Preemption (NJNP) discipline for the mobile charger, and provide analytical results on the system throughput and charging latency from the perspectives of the mobile charger and individual sensor nodes, respectively. To demonstrate how the actual system design can benefit from our analytical results, we present two examples on determining the essential system parameters such as the optimal remaining energy level for individual sensor nodes to send out their recharging requests and the minimal energy capacity required for the mobile charger. Through extensive simulation with real-world system settings, we verify that our analytical results match the simulation results well and the system designs based on our analysis are effective.

Patent
Nadim Khlat1
07 Jul 2015
TL;DR: In this article, a wireless charging circuit comprising a radio frequency (RF) power harvesting circuit was proposed to provide fast charging to the battery while protecting the battery from overcharging damage.
Abstract: Aspects disclosed in the detailed description include a wireless charging circuit comprising a radio frequency (RF) power harvesting circuit. In one aspect, the RF power harvesting circuit is configured to harvest a wireless RF charging signal provided by a wireless charging station to generate a direct-current (DC) charging signal to charge a battery, for example, a lithium-ion (Li-ion) battery, in a battery-operated electronic device. In another aspect, a wireless charging controller controls the RF power harvesting circuit to dynamically increase or decrease an effective charging power of the DC charging signal according to a target charging power determined according to a charging profile of the battery. By dynamically adjusting the effective charging power provided to the battery according to the charging profile of the battery, it is possible to provide fast charging to the battery while protecting the battery from overcharging damage.

Journal ArticleDOI
TL;DR: In this article, a survey of the energy-efficient cognitive radio (CR) techniques and the optimization of green-energy-powered wireless networks is presented, and the state of the art of energy efficient CR-based wireless access networks is discussed in various aspects, such as relay and cooperative radio and small cells.
Abstract: A 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, whereas dependence on the traditional unsustainable energy is assuaged by adopting energy harvesting 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 CR 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 CR networks that are powered by energy harvesters.

Journal ArticleDOI
TL;DR: A resonant bowtie antenna that has been optimized to produce highly enhanced localized fields at the bow tip that is critical in producing DC current directly from THz signals without the application of an external electric source, particularly for energy harvesting applications is demonstrated.
Abstract: The increasing energy demands of the world's population and the quickly diminishing fossil fuel reserves together suggest the urgent need to secure long-lasting alternative and renewable energy resources. Here, we present a THz antenna integrated with a rectifier (rectenna) for harvesting infrared energy. We demonstrate a resonant bowtie antenna that has been optimized to produce highly enhanced localized fields at the bow tip. To benefit from this enhancement, the rectifier is realized between the overlapped antenna's arms using a 0.7 nm copper oxide. The thin film diode offers low zero bias resistance of 500 Ω, thus improving the impedance matching with the antenna. In addition, the rectenna prototype demonstrates high zero bias responsivity (4 A/W), which is critical in producing DC current directly from THz signals without the application of an external electric source, particularly for energy harvesting applications.

Journal ArticleDOI
TL;DR: In this paper, the electrical responses of a textile substrate-based triboelectric nanogenerator (T-TENG), including nanostructured surface configurations provided by Al nanoparticles and PDMS, were reported.

Journal ArticleDOI
15 Jun 2015-Energy
TL;DR: In this article, a dual-mass piezoelectric bar harvester is developed for energy harvesting from ambient vibrations of a vehicle suspension system subjected to roughness of road surfaces.

Journal ArticleDOI
TL;DR: In this article, a simple and cost-effective laser engraving technique for fabricating a flexible self-charging micro-supercapacitor power unit (SCMPU) was proposed.
Abstract: The rapid development of portable and wearable electronic devices has increased demand for flexible and efficient energy harvesting and storage units. Conventionally, these are built and used separately as discrete components. Herein, we propose a simple and cost-effective laser engraving technique for fabricating a flexible self-charging micro-supercapacitor power unit (SCMPU), by integrating a triboelectric nanogenerator (TENG) and a micro-supercapacitor (MSC) array into a single device. The SCMPU can be charged directly by ambient mechanical motion. We demonstrate the ability of the SCMPU to continuously power light-emitting diodes and a commercial hygrothermograph. This investigation may promote the development of sustainable self-powered systems and provide a promising new research application for supercapacitors.

Journal ArticleDOI
TL;DR: In this article, mathematical derivations for unimorph piezoelectric energy harvester are presented Simulation is done using MATLAB and COMSOL Multiphysics software to study the effect of varying the length and shape of the beam to the generated voltage.

Journal ArticleDOI
TL;DR: In this paper, a flexible hybrid piezoelectric fiber based two-dimensional fabric nanogenerator which can be easily integrated with clothing and convert the mechanical energy of human body motion into electric energy.

Journal ArticleDOI
TL;DR: In this article, a curved piezoelectric generator for wearable applications is presented, which can operate at low frequencies below 50 Hz, generating 55 V of output voltage and 250 mA of output current at 35 Hz, and even works at frequencies as low as 1 Hz.

Journal ArticleDOI
TL;DR: In this article, the tradeoff between energy harvesting and information transmission was analyzed in a large-scale wireless powered communication network, and the authors showed that the optimal charging design is not unique, due to the sufficient energy stored in the battery.
Abstract: Wireless charging is a promising way to power wireless nodes' transmissions. This paper considers new dual-function access points (APs), which are able to support the energy/information transmission to/from wireless nodes. We focus on a large-scale wireless powered communication network (WPCN), and use stochastic geometry to analyze the wireless nodes' performance tradeoff between energy harvesting and information transmission. We study two cases with battery-free and battery-deployed wireless nodes. For both cases, we consider a harvest-then-transmit protocol by partitioning each time frame into a downlink (DL) phase for energy transfer, and an uplink (UL) phase for information transfer. By jointly optimizing frame partition between the two phases and the wireless nodes' transmit power, we maximize the wireless nodes' spatial throughput subject to a successful information transmission probability constraint. For the battery-free case, we show that the wireless nodes prefer to choose small transmit power to obtain large transmission opportunity. For the battery-deployed case, we first study an ideal infinite-capacity battery scenario for wireless nodes, and show that the optimal charging design is not unique, due to the sufficient energy stored in the battery. We then extend to the practical finite-capacity battery scenario. Although the exact performance is difficult to be obtained analytically, it is shown to be upper and lower bounded by those in the infinite-capacity battery scenario and the battery-free case, respectively. Finally, we provide numerical results to corroborate our study.

Journal ArticleDOI
TL;DR: In this article, a flexible and implantable piezoelectric generator (PG) was used to generate electric power from the ascending aorta of a porcine.

Journal ArticleDOI
07 Apr 2015-ACS Nano
TL;DR: This work realized a self-powered smart window system through integrating an electrochromic device (ECD) with a transparent TENG driven by blowing wind and raindrops that display reversible variations due to electrochemical redox reactions.
Abstract: The self-powered system is a promising concept for wireless networks due to its independent and sustainable operations without an external power source. To realize this idea, the triboelectric nanogenerator (TENG) was recently invented, which can effectively convert ambient mechanical energy into electricity to power up portable electronics. In this work, a self-powered smart window system was realized through integrating an electrochromic device (ECD) with a transparent TENG driven by blowing wind and raindrops. Driven by the sustainable output of the TENG, the optical properties, especially the transmittance of the ECD, display reversible variations due to electrochemical redox reactions. The maximum transmittance change at 695 nm can be reached up to 32.4%, which is comparable to that operated by a conventional electrochemical potentiostat (32.6%). This research is a substantial advancement toward the practical application of nanogenerators and self-powered systems.