Showing papers on "Energy harvesting published in 2012"
TL;DR: The TENG was systematically studied and demonstrated as a sustainable power source that can not only drive instantaneous operation of light-emitting diodes (LEDs) but also charge a lithium ion battery as a regulated power module for powering a wireless sensor system and a commercial cell phone, opening the chapter of impacting general people's life by nanogenerators.
Abstract: Harvesting energy from our living environment is an effective approach for sustainable, maintenance-free, and green power source for wireless, portable, or implanted electronics. Mechanical energy scavenging based on triboelectric effect has been proven to be simple, cost-effective, and robust. However, its output is still insufficient for sustainably driving electronic devices/systems. Here, we demonstrated a rationally designed arch-shaped triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polymer thin film and a metal thin foil. The working mechanism of the TENG was studied by finite element simulation. The output voltage, current density, and energy volume density reached 230 V, 15.5 μA/cm 2 , and 128 mW/cm 3 , respectively, and an energy conversion efficiency as high as 10−39% has been demonstrated. The TENG was systematically studied and demonstrated as a sustainable power source that can not only drive instantaneous operation of light-emitting diodes (LEDs) but also charge a lithium ion battery as a regulated power module for powering a wireless sensor system and a commercial cell phone, which is the first demonstration of the nanogenerator for driving personal mobile electronics, opening the chapter of impacting general people's life by nanogenerators.
1,018 citations
TL;DR: This work demonstrates a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation and extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting.
Abstract: By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm(3) at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting.
816 citations
TL;DR: This work considers transmission policies for rechargeable nodes with energy harvesting battery equipped nodes, and optimum solutions for two related problems are identified, including the transmission policy that maximizes the short term throughput.
Abstract: Wireless networks with energy harvesting battery equipped nodes are quickly emerging as a viable option for future wireless networks with extended lifetime Equally important to their counterpart in the design of energy harvesting radios are the design principles that this new networking paradigm calls for In particular, unlike wireless networks considered to date, the energy replenishment process and the storage constraints of the rechargeable batteries need to be taken into account in designing efficient transmission strategies In this work, such transmission policies for rechargeable nodes are considered, and optimum solutions for two related problems are identified Specifically, the transmission policy that maximizes the short term throughput, ie, the amount of data transmitted in a finite time horizon is found In addition, the relation of this optimization problem to another, namely, the minimization of the transmission completion time for a given amount of data is demonstrated, which leads to the solution of the latter as well The optimum transmission policies are identified under the constraints on energy causality, ie, energy replenishment process, as well as the energy storage, ie, battery capacity For battery replenishment, a model with discrete packets of energy arrivals is considered The necessary conditions that the throughput-optimal allocation satisfies are derived, and then the algorithm that finds the optimal transmission policy with respect to the short-term throughput and the minimum transmission completion time is given Numerical results are presented to confirm the analytical findings
784 citations
TL;DR: If unlimited energy can be stored in the battery with harvested energy and the full SI is available, it is proved the optimality of a water-filling energy allocation solution where the so-called water levels follow a staircase function.
Abstract: We consider the use of energy harvesters, in place of conventional batteries with fixed energy storage, for point-to-point wireless communications. In addition to the challenge of transmitting in a channel with time selective fading, energy harvesters provide a perpetual but unreliable energy source. In this paper, we consider the problem of energy allocation over a finite horizon, taking into account channel conditions and energy sources that are time varying, so as to maximize the throughput. Two types of side information (SI) on the channel conditions and harvested energy are assumed to be available: causal SI (of the past and present slots) or full SI (of the past, present and future slots). We obtain structural results for the optimal energy allocation, via the use of dynamic programming and convex optimization techniques. In particular, if unlimited energy can be stored in the battery with harvested energy and the full SI is available, we prove the optimality of a water-filling energy allocation solution where the so-called water levels follow a staircase function.
726 citations
TL;DR: One way of energy harvesting without such restraints is to utilize piezoelectric materials that can convert vibrational and mechanical energy sources from human activities such as pressure, bending, and stretching motions into electrical energy.
Abstract: Outdoor renewable energy sources such as solar energy (15 000 μ W/cm 3 ), [ 3 , 4 ] wind energy (380 μ W/cm 3 ), [ 5 ] and wave energy (1 000 W/cm of wave crest length) [ 6 , 7 ] can provide largescale needs of power. However, for driving small electronics in indoor or concealed environments [ 3 , 8 ] (such as in tunnels, clothes, and artifi cial skin) and implantable biomedical devices, innovative approaches have to be developed. One way of energy harvesting without such restraints is to utilize piezoelectric materials that can convert vibrational and mechanical energy sources from human activities such as pressure, bending, and stretching motions into electrical energy. [ 9–11 ]
604 citations
TL;DR: In this article, a dual-path architecture for energy harvesting is employed that has a peak efficiency improvement of 11-13% over the traditional two-stage approach, which is achieved by combining energy from solar, thermal, and vibration sources.
Abstract: A platform architecture combining energy from solar, thermal, and vibration sources is presented. A dual-path architecture for energy harvesting is employed that has a peak efficiency improvement of 11%-13% over the traditional two-stage approach. The system implemented consists of a reconfigurable multi-input, multi-output switch matrix that combines energy from three distinct energy-harvesting sources-photovoltaic, thermoelectric, and piezoelectric. The system can handle input voltages from 20 mV to 5 V and is capable of extracting maximum power from individual harvesters all at the same time utilizing a single inductor. A proposed time-based power monitor is used for achieving maximum power point tracking for the photovoltaic harvester. This has a peak tracking efficiency of 96%. The peak efficiencies achieved with inductor sharing are 83%, 58%, and 79% for photovoltaic boost, thermoelectric boost, and piezoelectric buck-boost converters, respectively. The switch matrix and the control circuits are implemented on a 0.35-μm CMOS process.
446 citations
TL;DR: A new design for an energy harvesting device is proposed in this paper, which enables scavenging energy from radiofrequency (RF) electromagnetic waves by proposing a dual-stage energy harvesting circuit composed of a seven-stage and ten-stage design, the former being more receptive in the low input power regions, while the latter is more suitable for higher power range.
Abstract: A new design for an energy harvesting device is proposed in this paper, which enables scavenging energy from radiofrequency (RF) electromagnetic waves. Compared to common alternative energy sources like solar and wind, RF harvesting has the least energy density. The existing state-of-the-art solutions are effective only over narrow frequency ranges, are limited in efficiency response, and require higher levels of input power. This paper has a twofold contribution. First, we propose a dual-stage energy harvesting circuit composed of a seven-stage and ten-stage design, the former being more receptive in the low input power regions, while the latter is more suitable for higher power range. Each stage here is a modified voltage multiplier, arranged in series and our design provides guidelines on component choice and precise selection of the crossover operational point for these two stages between the high (20 dBm) and low power (-20 dBm) extremities. Second, we fabricate our design on a printed circuit board to demonstrate how such a circuit can run a commercial Mica2 sensor mote, with accompanying simulations on both ideal and non-ideal conditions for identifying the upper bound on achievable efficiency. With a simple yet optimal dual-stage design, experiments and characterization plots reveal approximately 100% improvement over other existing designs in the power range of -20 to 7 dBm.
444 citations
TL;DR: In this paper, the importance of energy harvesting using ZnO nanostructures is discussed, mainly focusing on photovoltaics, piezoelectric nanogenerators, and hybrid approach to energy harvesting.
341 citations
Posted Content•
TL;DR: The optimal mode switching rule at the receiver is derived to achieve various tradeoffs between the minimum transmission outage probability for ID and the maximum average harvested energy for EH, which are characterized by the boundary of a so-called “outage-energy” region.
Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the narrowband flat-fading channel subject to time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy opportunistically via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any time due to the practical circuit limitation. Therefore, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference condition. In this paper, we derive the optimal mode switching rule at the receiver to achieve various trade-offs between wireless information transfer and energy harvesting. Specifically, we determine the minimum transmission outage probability for delay-limited information transfer and the maximum ergodic capacity for no-delay-limited information transfer versus the maximum average energy harvested at the receiver, which are characterized by the boundary of so-called "outage-energy" region and "rate-energy" region, respectively. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control, information and energy transfer scheduling, and the receiver's mode switching. Our results provide useful guidelines for the efficient design of emerging wireless communication systems powered by opportunistic WEH.
335 citations
TL;DR: An optimal switching policy that incorporates a-priori knowledge of the channel coefficients is proposed and solved by a mixed-integer linear programming formulation.
Abstract: This letter deals with a three-node cooperative network where the relay node harvests energy from radio frequency (RF) radiation. The source node is the only available RF generator and introduces a fundamental switching between energy harvesting and data relaying. A greedy switching (GS) policy where the relay node transmits when its residual energy ensures decoding at the destination is investigated. The GS policy is modeled as a Markov chain for a discretized battery; the stationary distribution and the outage probability of the system are derived in closed form expressions. In addition, an optimal switching policy that incorporates a-priori knowledge of the channel coefficients is proposed and solved by a mixed-integer linear programming formulation.
324 citations
TL;DR: A method to synthesize a lead zirconate titanate textile in which nanowires are parallel with each other and a procedure to make it into flexible and wearable nanogenerators, which can generate 6 V output voltage and 45 nA output current.
Abstract: Wearable nanogenerators are of vital importance to portable energy-harvesting and personal electronics. Here we report a method to synthesize a lead zirconate titanate textile in which nanowires are parallel with each other and a procedure to make it into flexible and wearable nanogenerators. The nanogenerator can generate 6 V output voltage and 45 nA output current, which are large enough to power a liquid crystal display and a UV sensor.
01 Jul 2012
TL;DR: This paper derives the optimal mode switching rule at the receiver to achieve various trade-offs between wireless information transfer and energy harvesting and provides useful guidelines for the efficient design of emerging wireless communication systems powered by opportunistic WEH.
Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the flat-fading channel subject to the time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any given time due to the practical circuit limitation. As a result, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference conditions. In this paper, we derive the optimal mode switching rule at the receiver to achieve various tradeoffs between the minimum transmission outage probability for ID and the maximum average harvested energy for EH, which are characterized by the boundary of a so-called “outage-energy” region. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control and scheduling for information and energy transfer with the receiver's mode switching. Our results provide useful insights to the optimal design of emerging wireless communication systems powered by opportunistic WEH.
TL;DR: In this article, a summary of published techniques for power conditioning within energy harvesting systems is presented, where the focus is on low power systems, e.g., <;10 mW, for kinetic energy harvesting.
Abstract: In this paper, a summary of published techniques for power conditioning within energy harvesting systems is presented. The focus is on low-power systems, e.g, <;10 mW, for kinetic energy harvesting. Published concepts are grouped according to functionality and results contrasted. The various techniques described are considered in terms of complexity, efficiency, quiescent power consumption, startup behavior, and utilization of the harvester compared to an optimum load. This paper concludes with an overview of power management techniques that aim to maximize the extracted power and the utilization of the energy harvester.
TL;DR: A modified circuit and an improved analysis for the self-powered SSHI (SP-SSHI) are proposed, with the modified circuit, direct peak detection and better isolation among different units within the circuit are achieved, both of which result in the further removal on the dissipative components.
Abstract: In piezoelectric energy harvesting (PEH), with the use of the technique named synchronized switch harvesting on inductor (SSHI), the harvesting efficiency can be greatly enhanced. Furthermore, the introduction of its self-powered feature makes this technique more applicable for stand-alone systems. In this paper, a modified circuit and an improved analysis for the self-powered SSHI (SP-SSHI) are proposed. With the modified circuit, direct peak detection and better isolation among different units within the circuit are achieved, both of which result in the further removal on the dissipative components. In the improved analysis, details in the open circuit voltage, switching phase lag, and intermediate voltages among different phases are discussed, all of which lead to a better understanding on the working principle of SP-SSHI. The total power dissipation from the piezoelectric source is also investigated. It is of concern but has not been considered in the previous literatures. Both analyses and experiments show that, in terms of the harvested power, the higher the excitation level, the closer between SP-SSHI and ideal (externally powered) SSHI; at the same time, the more beneficial the adoption of SP-SSHI treatment in PEH, compared to the standard energy harvesting (SEH) technique. Under the four excitation levels investigated, the SP-SSHI can harvest up to 200% more power than the SEH interface circuit.
TL;DR: A novel TE concept based on the spin Seebeck effect, called 'spin-thermoelectric (STE) coating', which is characterized by a simple film structure, convenient scaling capability, and easy fabrication is shown, which may pave the way for novel applications making full use of omnipresent heat.
Abstract: Energy harvesting technologies, which generate electricity from environmental energy, have been attracting great interest because of their potential to power ubiquitously deployed sensor networks and mobile electronics. Of these technologies, thermoelectric (TE) conversion is a particularly promising candidate, because it can directly generate electricity from the thermal energy that is available in various places. Here we show a novel TE concept based on the spin Seebeck effect, called 'spin-thermoelectric (STE) coating', which is characterized by a simple film structure, convenient scaling capability, and easy fabrication. The STE coating, with a 60-nm-thick bismuth-substituted yttrium iron garnet (Bi:YIG) film, is applied by means of a highly efficient process on a non-magnetic substrate. Notably, spin-current-driven TE conversion is successfully demonstrated under a temperature gradient perpendicular to such an ultrathin STE-coating layer (amounting to only 0.01% of the total sample thickness). We also show that the STE coating is applicable even on glass surfaces with amorphous structures. Such a versatile implementation of the TE function may pave the way for novel applications making full use of omnipresent heat.
TL;DR: A general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment, which includes models with continuous energy arrival as well as battery constraints.
Abstract: Energy harvesting has emerged as a powerful technology for complementing current battery-powered communication systems in order to extend their lifetime. In this paper a general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment. Assuming that the energy arrival process is known non-causally at the transmitter, the structure of the optimal transmission scheme, which maximizes the amount of transmitted data by a given deadline, is identified. Our framework includes models with continuous energy arrival as well as battery constraints. A battery that suffers from energy leakage is studied further, and the optimal transmission scheme is characterized for a constant leakage rate.
TL;DR: In this paper, the authors present the current state of the art with respect to the key challenges such as high power density and wide bandwidth of operation, and describe improvements in piezoelectric materials and resonator structure design, which are believed to be the solutions to these challenges.
Abstract: Piezoelectric microelectromechanical systems (MEMS) have been proven to be an attractive technology for harvesting small magnitudes of energy from ambient vibrations. This technology promises to eliminate the need for replacing chemical batteries or complex wiring in microsensors/microsystems, moving us closer toward battery-less autonomous sensors systems and networks. To achieve this goal, a fully assembled energy harvester the size of a US quarter dollar coin (diameter = 24.26 mm, thickness = 1.75 mm) should be able to robustly generate about 100 µW of continuous power from ambient vibrations. In addition, the cost of the device should be sufficiently low for mass scale deployment. At the present time, most of the devices reported in the literature do not meet these requirements. This article reviews the current state of the art with respect to the key challenges such as high power density and wide bandwidth of operation. This article also describes improvements in piezoelectric materials and resonator structure design, which are believed to be the solutions to these challenges. Epitaxial growth and grain texturing of piezoelectric materials is being developed to achieve much higher energy conversion efficiency. For embedded medical systems, lead-free piezoelectric thin films are being developed, and MEMS processes for these new classes of materials are being investigated. Nonlinear resonating beams for wide bandwidth resonance are also being developed to enable more robust operation of energy harvesters.
Patent•
22 Mar 2012
TL;DR: In this paper, the authors provide examples of preferred embodiments including systems for harvesting energy from variable output energy harvesting apparatus, including energy harvesting devices for providing energy input to a switched mode power supply and a control loop for dynamically adjusting the system output power.
Abstract: The disclosed invention provides examples of preferred embodiments including systems for harvesting energy from variable output energy harvesting apparatus. The systems include energy harvesting apparatus for providing energy input to a switched mode power supply and a control loop for dynamically adjusting energy harvesting apparatus input to the switched mode power supply, whereby system output power is substantially optimized to the practical. Exemplary embodiments of the invention include systems for harvesting energy using solar cells in boost, buck, and buck-boost configurations.
03 Apr 2012
TL;DR: A transformer-based self-starting boost converter architecture with low-power maximum power point tracking (MPPT) control for low-voltage thermoelectric generator applications and an improved MPPT sensing method is proposed to simplify the circuit.
Abstract: While the demand for micro-energy harvesters (μEHs) is increasing (for seamless energy source in applications such as wireless sensor node), two major problems still obstruct versatile use of them. The first problem is the self-startup capability. Because many wireless sensor nodes are likely to be located where human-maintenance is difficult, starting them up manually can be as difficult as replacing the battery. Its realization has been difficult because μEHs must be able to turn itself on without any stored energy. Some previous works have reported such a function: some needed high voltage [1] or vibration [2] and one used a transformer as a starter [3]. The other problem is the maximum power point tracking (MPPT) capability. Because it is known that MPPT algorithms usually require considerable power consumption [4], using them in μEHs is impractical. This paper suggests a new boost converter architecture and MPPT control method which can bring μEH into practical use.
TL;DR: In this article, a comprehensive experimental study was conducted to investigate the use of magnets for improving the functionality of energy harvesters under various vibration scenarios, and the optimal nonlinear configuration (in terms of distance between magnets) was determined to be near the monostable-to-bistable transition region.
Abstract: In recent years, several strategies have been proposed to improve the functionality of energy harvesters under broadband vibrations, but they only improve the efficiency of energy harvesting under limited conditions. In this work, a comprehensive experimental study is conducted to investigate the use of magnets for improving the functionality of energy harvesters under various vibration scenarios. First, the nonlinearities introduced by magnets are exploited to improve the performance of vibration energy harvesting. Both monostable and bistable configurations are investigated under sinusoidal and random vibrations with various excitation levels. The optimal nonlinear configuration (in terms of distance between magnets) is determined to be near the monostable-to-bistable transition region. Results show that both monostable and bistable nonlinear configurations can significantly outperform the linear harvester near this transition region. Second, for ultra-low-frequency vibration scenarios such as wave heav...
TL;DR: An energy model for self-powered nanosensor motes is developed, which successfully captures the correlation between the energy harvesting and the energy consumption processes and captures the dynamic network behavior.
Abstract: Wireless nanosensor networks (WNSNs) consist of nanosized communicating devices, which can detect and measure new types of events at the nanoscale. WNSNs are the enabling technology for unique applications such as intrabody drug delivery systems or surveillance networks for chemical attack prevention. One of the major bottlenecks in WNSNs is posed by the very limited energy that can be stored in a nanosensor mote in contrast to the energy that is required by the device to communicate. Recently, novel energy harvesting mechanisms have been proposed to replenish the energy stored in nanodevices. With these mechanisms, WNSNs can overcome their energy bottleneck and even have infinite lifetime (perpetual WNSNs), provided that the energy harvesting and consumption processes are jointly designed. In this paper, an energy model for self-powered nanosensor motes is developed, which successfully captures the correlation between the energy harvesting and the energy consumption processes. The energy harvesting process is realized by means of a piezoelectric nanogenerator, for which a new circuital model is developed that can accurately reproduce existing experimental data. The energy consumption process is due to the communication among nanosensor motes in the terahertz band (0.1-10 THz). The proposed energy model captures the dynamic network behavior by means of a probabilistic analysis of the total network traffic and the multiuser interference. A mathematical framework is developed to obtain the probability distribution of the nanosensor mote energy and to investigate the end-to-end successful packet delivery probability, the end-to-end packet delay, and the achievable throughput of WNSNs. Nanosensor motes have not been built yet and, thus, the development of an analytical energy model is a fundamental step toward the design of WNSNs architectures and protocols.
TL;DR: In this paper, a power management architecture that utilizes both supercapacitor cells and a lithium battery as energy storages for a photovoltaic (PV)-based wireless sensor network is proposed.
Abstract: This paper proposes a power management architecture that utilizes both supercapacitor cells and a lithium battery as energy storages for a photovoltaic (PV)-based wireless sensor network The supercapacitor guarantees a longer lifetime in terms of charge cycles and has a large range of operating temperatures, but has the drawback of having low energy density and high cost The lithium battery has higher energy density but requires an accurate charge profile to increase its lifetime, feature that cannot be easily obtained supplying the wireless node with a fluctuating source as the PV one Combining the two storages is possible to obtain good compromise in terms of energy density A statistic analysis is used for sizing the storages and experimental results with a 5-W PV energy source are reported
08 Oct 2012
TL;DR: This work presents a novel energy prediction model, named Pro-Energy (PROfile energy Prediction model), for multi-source energy harvesting WSNs, which is able to leverage past energy observations to provide accurate estimations of future energy availability.
Abstract: Energy harvesting is one of the most promising technologies towards the goal of perpetual operation of wireless sensor networks (WSNs). Environmentally-powered systems, however, have to deal with the variable behavior of ambient energy sources, which results in different amounts and rates of energy available over time. To alleviate the problem of the harvested power being neither constant nor continuous, energy prediction methods can be employed. Such models forecast the source availability and estimate the expected energy intake, allowing the system to take critical decisions about the utilization of the available energy. In this work, we present a novel energy prediction model, named Pro-Energy (PROfile energy prediction model), for multi-source energy harvesting WSNs, which is able to leverage past energy observations to provide accurate estimations of future energy availability. To assess the performance of our proposed solution, we use real-life solar and wind traces that we collected by interfacing TelosB nodes with solar cells and wind micro-turbines, as well as public available traces of solar and wind obtained from weather monitoring stations in the US. A comparative performance evaluation between Pro-Energy and energy predictors previously proposed in the literature, such as EWMA and WCMA, has shown that our solution significantly outperforms existing algorithms for both short and medium term prediction horizons, improving the prediction accuracy up to 60%.
TL;DR: This paper presents a novel rectenna architecture tunable for 900 MHz-2.45 GHz operation, able to process RF input power in the -30 to +30 dBm range with a peak efficiency of 80%.
Abstract: Wireless energy transfer has been demonstrated using microwave electromagnetic support. Significant efficiencies are reported in the case of large dimension systems. Lots of embedded systems require a small power supply but with a large degree of integration where standard contactless energy transfer techniques suffer from poor efficiency. In such systems, RF input energy is rectified using rectenna circuits. The latter circuits are optimized for a given input RF power and cannot accommodate the two possible ways of energy transfer: the dedicated transfer (high power) or the harvesting of ambient energy (low power). This paper presents a novel rectenna architecture tunable for 900 MHz-2.45 GHz operation, able to process RF input power in the -30 to +30 dBm (dB miliwatt) range with a peak efficiency of 80%.
TL;DR: In this article, a low-power energy harvesting system targeting to harvest several milliwatts from vibration is presented, and several low power design schemes to reduce power dissipation of the proposed system are described.
Abstract: A low-power energy harvesting system targeting to harvest several milliwatts from vibration is presented in this paper. Several low-power design schemes to reduce power dissipation of the proposed system are described, and sources of power loss are analyzed to improve the power efficiency. A discontinuous conduction mode (DCM) flyback converter with the constant on-time modulation is adopted for our system. The DCM operation of a flyback converter is chosen as for maximum power point tracking (MPPT) to be implemented with a single current sensor. The constant on-time modulation lowers the clock frequency of the controller by more than an order of magnitude for our system, which reduces the dynamic power dissipation of the controller. MPPT, executed by a microcontroller unit (MCU), is achieved through dynamic resistive matching, and the MPPT is executed at intermittent time intervals due to a relatively slow change of the operating condition. When MPPT is not active, the MCU operates at a lower clock frequency to save power. Experimental results indicate that the proposed system harvests up to 8.4 mW power under 0.5-g base acceleration with four parallel piezoelectric cantilevers and achieves 72% power efficiency around the resonant frequency of 47 Hz.
TL;DR: In this article, the authors used nonlinear numerical simulations in the slender body limit, based on an explicit description of the coupling between the fluid-solid and electric systems, to determine the harvesting efficiency of the system, namely the fraction of the flow kinetic energy flux effectively used to power the output circuit.
Abstract: Self-sustained oscillations resulting from fluid-solid instabilities, such as the flutter of a flexible flag in axial flow, can be used to harvest energy if one is able to convert the solid energy into electricity. Here, this is achieved using piezoelectric patches attached to the surface of the flag that convert the solid deformation into an electric current powering purely resistive output circuits. Nonlinear numerical simulations in the slender-body limit, based on an explicit description of the coupling between the fluid-solid and electric systems, are used to determine the harvesting efficiency of the system, namely the fraction of the flow kinetic energy flux effectively used to power the output circuit, and its evolution with the system's parameters. The role of the tuning between the characteristic frequencies of the fluid-solid and electric systems is emphasized, as well as the critical impact of the piezoelectric coupling intensity. High fluid loading, classically associated with destabilization by damping, leads to greater energy harvesting, but with a weaker robustness to flow velocity fluctuations due to the sensitivity of the flapping mode selection. This suggests that a control of this mode selection by a careful design of the output circuit could provide some opportunities of improvement for the efficiency and robustness of the energy harvesting process.
TL;DR: In this article, the authors proposed a linear motion electromagnetic (EM) device for both vibration damping and energy harvesting, where the kinetic energy caused by earthquakes, wind or traffic loads is not only dissipated by EM dampers, but also stored by energy harvesting electric circuits connected to them.
TL;DR: In this paper, a method based on the dynamical features of stochastic bistable oscillators employed to model nonlinear piezoelectric harvesters is discussed.
TL;DR: A novel RF power harvesting front-end whose conversion efficiency is significantly improved at low RF power levels (<;-20 dBm) as compared to existing technologies is designed, making a game changing technology for powering mobile devices.
Abstract: This study is focused on equipping wireless devices (including sensors) with novel, high-efficiency circuitry to harvest and convert ambient radio frequency (RF) power to direct current (dc). Key components of this technology are (a) miniaturised antenna and (b) high-efficiency rectifying circuit. The first is responsible for capturing the RF waves, and the latter converts the RF energy to dc. A major challenge is the design of novel circuitry to generate a battery-like voltage from very low incoming RF energy. Under this study, the authors designed a novel RF power harvesting front-end whose conversion efficiency is significantly improved at low RF power levels (<;-20 dBm) as compared to existing technologies. Thus, the new circuitry can harvest ambient and widely available RF energy, making a game changing technology for powering mobile devices. In this study, the authors demonstrate this technology by using it to power a commercially available temperature and humidity meter with an LCD display. The latter is powered using nothing more than ambient WiFi signals in an office environment.
TL;DR: In this article, a galloping beam is used to harvest wind energy from a D-shaped cross-section of the beam, which is then converted into electrical energy by piezoelectric sheets.
Abstract: Galloping of structures such as transmission lines and bridges is a classical aeroelastic instability that has been considered as harmful and destructive. However, there exists potential to harness useful energy from this phenomenon. This paper focuses on harvesting wind energy that is being transferred to a galloping beam. The beam has a rigid tip body with a D-shaped cross section. Piezoelectric sheets are bonded on the top and bottom surface of the beam. During galloping, vibrational motion is input to the system due to aerodynamic forces on the D-section, which is converted into electrical energy by the piezoelectric (PZT) sheets. The relative importance of various parameters of the system such as wind speed, material properties of the beam, electrical load and beam’s natural frequency are discussed. Experimental and analytical investigations of dynamic response and power output are performed on a representative device. A maximum output power of 1.14 mW was measured at a wind velocity of 10.5 mph on a prototype device of length 235 mm and width 25 mm. A potential application for this device is to power wireless sensor networks on outdoor structures such as bridges and buildings. [DOI: 10.1115/1.4004674]