Energy Scavenging Research Articles

A comprehensive numerical study on flow-induced vibrations with various groove structures: Suppression or enhancing energy scavenging

This paper focuses on the enhancement or suppression effect of flow-induced vibration (FIV) caused by symmetrically installed groove structures with different shapes under high Reynolds numbers. The fluid flow field is simulated using the non-constant two-dimensional Reynolds-averaged Navier-Stokes (2D-RANS) equation and the SST k-ω turbulence model. A cylinder attached to four different groove shapes (square, triangular, semicircular, and two quarter-circle splices) is simulated for each shape of the groove with five mounting angles. The oscillatory amplitude, frequency response, displacement time history curve, vortex shedding mode, and energy harvesting characteristics are analyzed for each working condition at 2 < U* < 14 and 2.02 × 104 <Re < 1.44 × 105. The results show that the cylinder with different groove shapes and installation angles have different dynamic responses. The oscillatory amplitude of the square groove bluff body with α = 30°, 60°, and 150° is basically enhanced compared to the smooth cylinder, and the working bandwidth is increased as well. For the square groove placed at α = 60°, the oscillatory amplitude increases by 100% compared to the smooth cylinder, and the working bandwidth of the square groove at α = 90° is reduced by 50%. For the square groove body with α = 120°, the amplitude is enhanced, but the working bandwidth is reduced. The working bandwidth of the triangular groove is widened at all five angles, with the α = 60° groove being optimal, widening by 75%. Except for the triangular groove with α = 90°, the amplitude is improved to some extent compared with the smooth cylinder. The working bandwidths of the semicircular grooves are widened, and the improvement effect of α = 150° is the smallest of the five angles. For the two quarter-circle splices grooves, the grooves arranged at α = 30°, 90°, 120°, and 150° have a decrease in amplitude when U* = 6, and more pronounced at 90° and 120°. Two quarter-circle spliced groove cylinders with α = 120° have the best amplitude enhancement effect.

Thermal analysis of oscillating thermomagnetic devices beyond the lumped approximation

The temperature (T) dependent magnetization of materials near the Curie temperature has been leveraged for thermomagnetic energy harvesting and thermal rectification. In these thermal devices, a translating shuttle containing a ferromagnet (e.g., gadolinium) experiences a T-dependent magnetic attraction to a stationary permanent magnet, leading to steady-periodic mechanical oscillations of the shuttle between the hot and cold surfaces. Prior analytical work investigating thermomagnetic devices has focused on the small-Biot (Bi) number regime in which the shuttle T is thermally lumped due to the small interfacial thermal contact conductances. Here, we use a separation of variables technique to derive analytical expressions to the governing heat conduction equation for the full spatiotemporal T profile considering a thin magnetic foil mounted on a thick shuttle. The results show that the lumped solution prediction for the time-averaged heat flow Q is accurate within <5% when either the hot or cold surface Bi is <0.1. In the moderate-to-large Bi regime, analytical solutions and numerical validations show that Q approaches a maximum value determined by conduction through the shuttle, while the oscillation frequency f increases with increasing Bi. The analytical solutions developed here can be used to design and evaluate the thermal performance of thermomagnetic devices proposed for use in energy scavenging and thermal rectification applications.

Hydrokinetic energy harvesting from flow-induced vibration of a hollow cylinder attached with a bi-stable energy harvester

This paper proposes an electromagnetic bi-stable energy harvester (EBEH) with tunable stiffness for scavenging the hydrokinetic energy from flow-induced vibration (FIV) scenarios. A mathematical model of the magneto-mechanical–electrical coupling system is established considering vortex-induced forces, wake oscillator effect, negative linear stiffness and hybrid excitations. The bi-stable system with adjustable barrier height is employed to enhance state-of-the-art energy scavenging performance of vortex-induced vibration (VIV). Preliminary verification with regard to VIV within a lock-in wind speed range has been implemented by means of CFD simulation. The nonlinear energy transfer capacity and energy conversion performance of the FIV based EBEH are evaluated under solitary vortex-induced vibration (VIV) and hybrid excitations. Simulation results show that EBEH with larger negative linear stiffness has higher energy conversion efficiency and target energy transfer capacity in a wide range of inlet velocities. The large amplitude and low frequency vibration of the VIV of the cylinder is mainly caused by the lift pulsation, meanwhile the small amplitude and high frequency galloping are caused by the perpendicular component pulsation of the drag force. The fluctuations of the lift/drag coefficient at different inflow velocities are directly related to the VIV or galloping amplitude of the cylindrical bluff body. Specifically, the frequency fD is approximately twice the frequency fL in a wide inflow velocity range; The amplitude of fluctuating lift exceeds 2.0 in a wide range of inflow velocity from 1.0 m/s to 20 m/s. The nonlinear energy transfer efficiency of the FIV based EBEH with smaller barrier height is greater than 60% when the inflow velocity ranges from 20 m/s to 30 m/s. The nonlinear energy transfer capability of EBEH with appropriate negative stiffness outperforms its counterpart of cubic stiffness more than ten times. The maximum mean harvested power achieved from EBEH can be increased over 900% than that of the cubic stiffness case. Regardless of negative stiffness alteration, the optimal external load that maximizes the EBEH output power is around 50 Ω. Additionally, when the vortex-induced vibration cannot be woken, intervention of base excitation causes considerable chaotic motion consisting of aperiodic intra-well and inter-well snap-throughs at low inflow velocities. Nevertheless, nonlinear energy transfer efficiency of bi-stable energy harvester is slightly crippled with the increase of the base excitation intensity.

A typical phenotypes due to NDUFV1 mutations

Mitochondria have a critical role in energy metabolism, generating and scavenging of free radicals, intracellular Ca2+ regulation, and cell mitophagy. Dysfunction of the mitochondrial oxidative phosphorylation complex is the most frequent inborn errors of metabolism. Mitochondrial diseases are highly diverse in etiology, age of the disease onset, involvement of multiple organ systems, and genetic causes. NDUFV1 is a core subunit of mitochondrial Complex I (CI), and mutations cause CI deficiency. Clinically, CI deficiency is associated with severe infantile lactic acidosis, cardiomyopathy, encephalomyopathy, leukoencephalopathy, and Leigh syndrome. The cellular biology and molecular mechanisms of mitochondrial diseases are still elusive due to the heterogeneous genetic background and lack of phenotype-genotype correlation. Neurological abnormalities are the second most frequent presentations of mitochondrial diseases, including white matter abnormalities, psychomotor regression, and mental disability. The defects in myelin sheath or glial cells cause leukodystrophy which is a progressive genetical syndrome. To date, no therapy is available to cure mitochondrial diseases; exploration of the phenotype and molecular background are crucial for disease diagnosis, supportive treatments, proper genetic counselling, prenatal diagnosis, and experimental treatments. This article underscores the atypical clinical presentations of NDUFV1 mutations and the importance of a multidisciplinary approach to correlate phenotypes, biochemical, radiological, and molecular diagnosis. Implementation of multidisciplinary approach will enhance the possibility of discovering the therapeutic targets to treat mitochondrial disorders and ensure prenatal diagnosis to prevent inherited diseases.

High performance additional mass enhanced film structure triboelectric nanogenerator for scavenging vibration energy in broadband frequency range

It is highly desired to develop high performance vibration energy scavengers to power amounted and distributed sensors along with the era of Internet of Things. This study proposes a novel additional mass enhanced film structure triboelectric nanogenerator (AMF-TENG) for efficiently scavenging broadband vibration energy. The AMF-TENG is composed of an additional mass, a fluorinated ethylene propylene (FEP) film with a carbon electrode, and a conductive fabric fixed on a hollow frame. The additional mass can enhance the electrical output of the AMF-TENG by 25.5 times due to the vibration amplitude and contact forces between the FEP film and conductive fabric are greatly amplified. The utilization of a hollow frame makes the electrical output of AMF-TENG 150% higher than the enclosed frame. Theoretical analysis and experimental studies were carried out to investigate the design parameters. The experimental results indicate that the AMF-TENG shows good electrical performance in the broadband frequency range from 15 to 70 Hz. Under the vibration condition of 40 Hz and 30 m/s2, it can generate a maximum power density of 622.59 W/m3, which is higher than previous studies by 155.2%. Finally, the AMF-TENG is proven to power temperature and humidity sensors continuously under actual machine vibration. In brief, the AMF-TENG provides a new method for efficiently scavenging of vibration energy in the broadband frequency range.

Toward Large-Scale Energy Harvesting by a UV-Curable Organic-Coating-Based Triboelectric Nanogenerator.

Triboelectric nanogenerators (TENGs) stand out as an attractive form of technology for the efficient harvest of mechanical energy and the powering of wearable devices due to their light weight, simplicity, high power density, and efficient vibration energy scavenging capabilities. However, the requirement for micro/nanostructures and/or complex and expensive instruments hinders their cheap mass production, thus limiting their practical applications. By using a simple, cost-effective, fast spray-coating process, we develop high-performance UV-curable triboelectric coatings for large-scale energy harvesting. The effect of different formulations and coating compositions on the triboelectric output is investigated to design triboelectric coatings with high output performance. The TENG based on a hybrid coating exhibits high output performance of 54.5 μA current, 1228.9 V voltage, 163.6 nC transferred charge and 3.51 mW output power. Moreover, the hybrid coatings show good long-term output stability. All the results indicate that the designed triboelectric coatings show great potential for large-scale energy harvesting with the advantages of cost-effectiveness, fast fabrication, easy mass production and long-term stability.

An electrospun PVDF-KNN nanofiber based lead-free piezoelectric nanogenerator for mechanical energy scavenging and self-powered force sensing applications

We have developed a lead-free piezoelectric nanogenerator based on PVDF-KNN nanofibers and demonstrated the same as self-powered flexible force sensor with high sensitivity (3 V/N).

First-principles investigation on structural and optoelectronic properties of buckled SnO monolayer for effective solar energy scavenging

Two-dimensional (2D) materials have gathered considerable attention for next-generation optoelectronic devices owing to their intriguing optical and electronic properties. The semiconductor SnO has shown potential for flexible electronics, optoelectronics, gas sensing, and Li-ion battery applications due to its indirect bandgap, and high carrier mobility. In the present work, we investigate the physical properties of a buckled tin oxide (SnO) monolayer using density functional theory (DFT) calculations. The structural analysis reveals that buckled SnO monolayer is energetically stable and exhibits the hexagonal crystal structure. Phonon dispersion analysis depicts the dynamical stability of the buckled SnO monolayer and obtained the quadratic behavior of flexural acoustic modes (ZA) near the zone center. Further, the electronic property calculation shows that the buckled SnO is an indirect semiconductor with a bandgap of 1.71 eV and the transparent behavior of the material is disclosed by analyzing the optical parameters. Moreover, the computed solar power conversion efficiency of 16.76% for buckled SnO monolayer demonstrates the potential as a light absorber in the field of solar energy scavenging.

A hybrid piezoelectric and electrostatic energy harvester for scavenging arterial pulsations

Implantable and wearable biomedical devices suffer from a limited lifespan of on-board batteries which require change causing physical discomfort. In order to overcome this, various energy harvesters have been developed as the human body possesses several types of energy available for scavenging through appropriately designed energy harvesting devices, while the cardiovascular system in particular represents a constant reliable source of mechanical energy from vibration. Most conventional energy harvesters exploit only a single phenomenon, such piezo- or triboelectricity, thus producing reduced power density. As an improvement, hybridisation of energy harvesters intends to negate this drawback by simultaneously scavenging energy by multiple harvesters. In the present work, the reverse electrowetting on dielectric (REWOD) phenomenon is combined with the piezoelectric effect in a proof-of-concept hybrid harvester for scavenging biomechanical energy from arterial or other type pulsations. A mathematical model of the harvester was developed; and, an investigation using computational fluid dynamics simulations was carried out using the COMSOL Multiphysics software. The effect of the materials of piezoelectric film and geometrical features of the harvester on parameters such as the displacement, the frequency of pulsations and the energy produced were studied. An experimental setup that could model the time-varying pressures and displacements caused from arterial pulsations was designed and the characteristics of the produced piezoelectrical energy were analysed. A comparison between experimental and computational data was carried out demonstrating a good agreement. The dependencies between geometrical parameters and electrical output were determined and recommendations on piezoelectric materials and design solutions were provided.

Zero Energy IoT Devices in Smart Cities Using RF Energy Harvesting

The invention of batteries made it possible to store electricity for many purposes. One of the purposes is to keep the operations of WSN running without any interruptions. The main drawback of sensor nodes is their limited energy sources. The researcher introduces the energy harvesting (EH) concept for IoT-based WSNs to overcome energy limitations and charge the IoT devices. Many energy harvesting techniques have been introduced, such as solar, thermal, and flow-based ones, but radio frequency (RF)-based EH techniques received great attention from researchers due to their easy availability (from TV, radio, and wireless frequencies). In this paper, we have conducted a real-world experiment on Powercast energy harvesting devices and examined the behavior of sensed data in different scenarios, such as indoor, distance (feet/meters), and directional antennas. In our experiments, we have observed that when a device is removed from the charger, the energy scavenging process degrades and reaches a dead state. To stop a device from entering a dead state, we introduce a mobile charger technique to charge the device and find the optimal place for chargers and sensor devices. During mobile charging, we have also observed that when the directional antennas change their angle, the energy scavenging process degrades. To tackle these problems, we introduced two algorithms for directional and omni-directional antennas that efficiently solve the problem. Furthermore, we have obtained results for these scenarios and show that this technique has a promising output.

Photovoltaic-triboelectric hybridized nanogenerator for simultaneously scavenging light and liquid-droplet energies

Hybridized nanogenerator has made breakthroughs in multiple types of energy scavenging, however, introduction of new materials that make hybridized structure more simplified and environmentally friendly is needed further research. Here, we developed a hybridized nanogenerator composed of photovoltaic cell (PVC) and triboelectric nanogenerator (TENG), which can scavenge both light and liquid-droplet energies. In this device, the PVC share bottom electrode with the TENG. The device exhibits good hybridized process, generating peak current and peak voltage of 16.96 μA and 0.83 V, by scavenging light and liquid-droplet energies simultaneously. The hybridized output show that the maximum hybridized peak power was determined by the peak power of TENG who exhibited pulselike output, while the maximum hybridized output energy was much more affected by the output energy of PVC who generated continuous signals. This work enables the simultaneously scavenging light and liquid-droplet energies through individual device, which will open up unexplored avenues for simultaneously scavenging liquid-droplet energy and other types of energies.

Bifurcation analysis and nonlinear dynamics of a rolling magnet multistable electromagnetic energy harvester

The objective of this study is to provide a rolling magnet multistable electromagnetic-induction energy harvester (RM-MEH) for scavenging energy from a wide frequency range. The RM-MEH designed based on a magnetic levitation rolling magnet possesses the merit of small damping. By clarifying the mechanics of the RM-MEH, the static bifurcation behavior is investigated and results demonstrate that monostable, bistable, and tristable configurations with different types of potentials can be obtained with proper parameters. Numerical simulations under sweep frequency excitation indicate that the monostable, bistable, and tristable configurations with proper potential functions achieve large-amplitude oscillation in a wide frequency range. Under constant frequency excitation, the nonlinear dynamics are analyzed utilizing the bifurcation diagram, phase orbit, and Poincaré map, and the multiple vibrational patterns are verified. Finally, the vibration isolation characteristics of the system are briefly discussed considering the electromagnetic force of the RM-MEH. In summary, the demonstration of the novel RM-MEH expands the approach to achieving multistable oscillation and provides a new way of thinking for designing nonlinear energy harvesters.

A droplet-based triboelectric-piezoelectric hybridized nanogenerator for scavenging mechanical energy

Water droplet energy has received much attention as a newborn renewable energy source. Triboelectric nanogenerators (TENGs) demonstrates enormous application in scavenging mechanical energy. Nowadays, the water droplet nanogenerator based on liquid-solid TENG has been greatly improved. However, these water droplet nanogenerators scavenge the mechanical energy of liquid-solid contact of water droplets by TENG, but not the deformation energy of the substrate. Here, we propose a new design strategy to increase the current of the water droplet nanogenerator through simultaneous scavenging of the mechanical energy of the liquid-solid contact and the deformation energy. A droplet-based triboelectric-piezoelectric hybridized nanogenerator (TPiHNG) with cantilever beam structure was fabricated under the strategy. The TPiHNG has a significantly higher current compared to TENG. The response time difference between piezoelectric nanogenerator (PiENG) and TENG is proposed for the first time as an important parameter of TPiHNG. This work provides a novel approach to scavenge water droplet energy more efficiently.

Performance evaluation of nonlinear energy scavenging overlay networks

SummaryThis paper investigates a nonlinear energy scavenging overlay network (NLESON) wherein a primary source (PS) communicates with a primary destination (PD) probably under aid of a secondary source (SS) who communicates with a secondary destination (SD). SS is a power‐constrained device, and thence, its operation relies on energy harvested by a practical nonlinear energy scavenger. To support PS and exploit the harvested energy at most, SS adaptively switches between single and superposition modes where the single mode allows SS to transmit solely its signal with the entire harvested energy and the superposition mode asks SS to transmit both—its signal and amplified primary signal—with different power fractions. Moreover, for increasing the probability of successfully decoding primary signal at PD and SD, which then reduces considerably primary interference on secondary signal in the superposition mode, we leverage both direct channels (PS‐PD and PS‐SD) and apply both signal combining paradigms (maximum ratio combining and selection combining). The outage/throughput performance of the NLESON is assessed quickly through the proposed closed‐form expressions over shadowed fading channels. Various results exposed the effectiveness of the aforementioned solutions for the NLESON and their flexibility in controlling system performance.

Design, modelling and testing of a compact piezoelectric transducer for railway track vibration energy harvesting

To enable wireless sensor networks to monitor rail infrastructures in real-time, a cost-effective power source is in need. This work presents the design, modelling and testing of a piezo stack energy harvester with frequency up-conversion mechanism for scavenging energy from railway track vibration. The proposed harvester is designed to meet railway track applications’ size, frequency, and stress requirements. A compact design integrating the inertial mass and the piezo stack transducer systems is used to enable the mechanical collision for realising the frequency up-conversion mechanism and ensure the size of the energy harvester is suitable for the limited space on the railway track. The frequency bandwidth of the energy harvester is broadened by utilizing the longitudinal and torsional oscillation of the designed plate springs which enable the system to have two adjacent natural frequencies. The mechanical transformer of the piezo stack transducer system is designed to achieve the required stress level under both the impact force caused by the collision motion and the inertial force generated by the random vibration of the rails. A finite element model (FEM) analysing the free vibration of the piezo stack transducer caused by the frequency up-conversion mechanism is developed to analyse the dynamic characteristics of the coupled system. Lab tests are carried out to validate the proposed FEM and evaluate the impact of different factors such as load resistance, acceleration, initial interval, plate spring, and pulse excitation on power generation. Experimental results show that the energy harvester has two resonant frequencies of 17 Hz and 20 Hz. The frequency up-conversion mechanism can convert this low-frequency vibration into the piezo stack transducer’s high resonant frequency vibration of 94 Hz. A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration. • A piezo stack energy harvester for railway track vibration is designed, modelled and tested. • A compact design is proposed to enable the mechanical collision for realising the frequency up-conversion mechanism. • Two adjacent natural frequencies are achieved to broaden the frequency bandwidth. • The mechanical transformer is designed to achieve the required stress level under the impact force and inertial force. • A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration.

Recent Advances in Energy Harvesting from the Human Body for Biomedical Applications

Energy harvesters serve as continuous and long-lasting sources of energy that can be integrated into wearable and implantable sensors and biomedical devices. This review paper presents the current progress, the challenges, the advantages, the disadvantages and the future trends of energy harvesters which can harvest energy from various sources from the human body. The most used types of energy are chemical; thermal and biomechanical and each group is represented by several nano-generators. Chemical energy can be harvested with a help of microbial and enzymatic biofuel cells, thermal energy is collected via thermal and pyroelectric nano-generators, biomechanical energy can be scavenged with piezoelectric and triboelectric materials, electromagnetic and electrostatic generators and photovoltaic effect allows scavenging of light energy. Their operating principles, power ratings, features, materials, and designs are presented. There are different ways of extracting the maximum energy and current trends and approaches in nanogenerator designs are discussed. The ever-growing interest in this field is linked to a larger role of wearable electronics in the future. Possible directions of future development are outlined; and practical biomedical applications of energy harvesters for glucose sensors, oximeters and pacemakers are presented. Based on the increasingly accumulated literature, there are continuous promising improvements which are anticipated to lead to portable and implantable devices without the requirement for batteries.

Scavenging energy from aeroelastic vibrations for hybrid stall control in a fixed-wing micro aerial vehicle

Scavenging energy from aeroelastic vibrations was considered for a self-powered hybrid passive-active stall control system intended to improve the aerodynamic performance of fixed-wing micro aerial vehicles without exhausting available batteries. It was found that the passive component of the system generates intense streamwise vortices, which give rise to vortex-induced vibrations. Measured frequency response functions indicated accelerations in a wing prototype up to 0.1 g at relatively low frequencies, when it was operated at simulated flight conditions in a wind tunnel. Aiming to use this resource for additional power, a piezoelectric energy harvesting device was installed inside the wing and tuned for resonant response. Two electromechanical modeling approaches for the piezoelectric harvester were investigated, namely, an analytical model and finite elements simulations. A comparison with experimental results has shown that the latter approach is better equipped to deal with advanced designs, yielding accurate predictions in the present study. Extracted power and generated voltage were quantified as a function of the electric loading resistance. The reported data demonstrated that the proof of concept was achieved, so that a lightweight, low-consumption actuator for the active component of the stall control system can be powered by the energy of structural vibrations.

The Future of Clean Computing May Be Dirty

The emergence of the Internet of Things and pervasive sensor networks have generated a surge of research in energy scavenging techniques. We know well that harvesting RF, solar, or kinetic energy enables the creation of battery-free devices that can be used where frequent battery changes or dedicated power lines are impractical. One unusual yet ubiquitous source of power is soil (earth itself) - or more accurately, bacterial communities in soil. Microbial fuel cells (MFCs) are electrochemical cells that harness the activities of microbes that naturally occur in soil, wetlands, and wastewater. MFCs have been a topic of research in environmental engineering and microbiology for decades, but are a relatively new topic in electronics design and research. Most low-power electronics have traditionally opted for batteries, RF energy, or solar cells. This is changing, however, as the limitations and costs of these energy sources hamper our ability to deploy useful systems that last for decades in challenging environments. If large-scale, long-term applications like underground infrastructure monitoring, smart farming, and sensing for conservation are to be possible, we must rethink the energy source.

Powering Solutions for Biomedical Sensors and Implants Inside the Human Body: A Comprehensive Review on Energy Harvesting Units, Energy Storage, and Wireless Power Transfer Techniques

For implantable medical devices, it is of paramount importance to ensure uninterrupted energy supply to different circuits and subcircuits. Instead of relying on battery stored energy, harvesting energy from the human body and any external environmental sources surrounding the human body ensures prolonged life of the implantable devices and comfort of the patients. In this article, we present existing issues and challenges related to the state-of-the-art solutions used for harvesting energy to power implantable devices. In addition, the details on existing energy storage technologies and various wireless power transfer techniques incorporating external or internal energy sources and sensors have been discussed. The authors have outlined the performance and power constraints of existing biomedical devices and provided a brief overview of various power architectures found in the literature. This survey has been conducted on existing implantable solutions in terms of output voltage, current, device dimension, application, generated power, energy density, and so on. Finally, the advantages and drawbacks of different solutions have been discussed and compared. Therefore, this article can be considered as an expedient reference for researchers conducting research in the field of energy scavenging, internal energy storage, wireless power transfer techniques, and power management of implantable medical devices.

Magnetic Force-Assisted Nonlinear Three-Dimensional Wideband Energy Harvester Using Magnetostrictive/Piezoelectric Composite Transducers.

This paper presents a nonlinear magnetoelectric energy harvester which has the potential to harvest vibrational energy over a wide bandwidth in arbitrary motion directions. Three springs with equal intersection angles are adopted to absorb the multi-directional vibration energy. Magnetic interaction between the magnets and ME transducers allows the nonlinear motion with enhanced harvesting frequency range. Very good agreement is observed between the numerical and experimental open-circuit voltage output frequency response curves. The experimental results show that the harvester can harvest vibrational energy in an arbitrary direction, exhibiting a further bandwidth of 5.2 Hz. This study provides a new solution to effectively use the magnetoelectric energy harvester for multi-directional and bandwidth vibrational energy scavenging in the surrounding environment.