Energy Scavenging Research Articles

A 3D-Printed Piezoelectric Microdevice for Human Energy Harvesting for Wearable Biosensors.

The human body is a source of multiple types of energy, such as mechanical, thermal and biochemical, which can be scavenged through appropriate technological means. Mechanical vibrations originating from contraction and expansion of the radial artery represent a reliable source of displacement to be picked up and exploited by a harvester. The continuous monitoring of physiological biomarkers is an essential part of the timely and accurate diagnosis of a disease with subsequent medical treatment, and wearable biosensors are increasingly utilized for biomedical data acquisition of important biomarkers. However, they rely on batteries and their replacement introduces a discontinuity in measured signals, which could be critical for the patients and also causes discomfort. In the present work, the research into a novel 3D-printed wearable energy harvesting platform for scavenging energy from arterial pulsations via a piezoelectric material is described. An elastic thermoplastic polyurethane (TPU) film, which forms an air chamber between the skin and the piezoelectric disc electrode, was introduced to provide better adsorption to the skin, prevent damage to the piezoelectric disc and electrically isolate components in the platform from the human body. Computational fluid dynamics in the framework of COMSOL Multiphysics 6.1 software was employed to perform a series of coupled time-varying simulations of the interaction among a number of associated physical phenomena. The mathematical model of the harvester was investigated computationally, and quantification of the output energy and power parameters was used for comparisons. A prototype wearable platform enclosure was designed and manufactured using fused filament fabrication (FFF). The influence of the piezoelectric disc material and its diameter on the electrical output were studied and various geometrical parameters of the enclosure and the TPU film were optimized based on theoretical and empirical data. Physiological data, such as interdependency between the harvester skin fit and voltage output, were obtained.

Tribo-piezoelectric synergistic BaTiO3/PDMS micropyramidal structure for high-performance energy harvester and high-sensitivity tactile sensing

Triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs) represent some of the most promising strategies for converting mechanical deformation and friction into electrical energy. This energy can be used to power electronic devices, such as wearables, and detect mechanical stimuli. Here, we have demonstrated the synergistic integration of piezoelectric and triboelectric effects by incorporating barium titanate (BaTiO3) nanoparticles into a pyramidal polydimethylsiloxane (PDMS) elastomer. This integration aims to enhance the performance of both pressure sensor devices and electrical energy harvesters. The pressure sensitivity of our proposed tribo-piezoelectric device reaches as high as 3.71 V∙kPa−1 for pressure sensing within the range of 0.1–100 kPa, the output voltage increasing to ∼ 370 V at 100 kPa. Our theoretical simulation of electrical power density at this specific pressure reveals that the mechanical deformation of the PDMS elastomer, combined with the polarization of BaTiO3 nanoparticles, synergistically generate tribo-piezoelectric charge on the surface. Therefore, our synergistic combination of triboelectric and piezoelectric effects opens a promising avenue for effectively converting mechanical action into electrical signals. This enables highly efficient energy scavenging and the development of high-sensitivity pressure sensors.

Triboelectric nanogenerator based on coastal bio-waste Ulva lactuca from Jeju island for sustainable energy harvesting

In the past, the occurrence of macro alga Ulva lactuca on the coastal areas of Jeju Island, Korea, has resulted in the expansion of devastating green tides, thus affecting coastal sustainability, aesthetic appearances, and tourism activities. Taking consideration of the above scenario, substantial economic costs are required for the environmental protection of the island, and it is highly recommended to employ Ulva lactuca in an alternative useful way. Hence, this paper proposes a new strategy to utilize Ulva lactuca as a tribopositive layer in a triboelectric nanogenerator (TENG). Based on the coastal bio-waste Ulva lactuca, the fabricated TENG device generates a maximum output voltage of 875 V, output current of 52 μA, and power density of 272.72 μW/cm2. Furthermore, the device presents excellent cyclic stability with no degradation in the output voltage even after 10000 consecutive cycles at a frequency of 2 Hz. The proposed TENG is further employed to charge the various commercially available capacitors, lightning LEDs, power stopwatches, and scavenge energy from body motions. It is anticipated that the proposed TENG device will pave a new way towards Ulva lactuca management for sustainable energy harvesting and clean coastlines.

High-Temperature Wireless Sensor Platform Powered by Energy Scavenging

High-Temperature Wireless Sensor Platform Powered by Energy Scavenging

Energy Scavenging for IoT in Harsh Environments

Energy Scavenging for IoT in Harsh Environments

Energy Scavenging for IoT in Harsh Environments

Energy Scavenging for IoT in Harsh Environments

Ultralow-Frequency Biomechanical Energy Scavenging and Human Activity Recognition at Different Positions Using a Multifunctional Wearable Energy Harvester

Ultralow-Frequency Biomechanical Energy Scavenging and Human Activity Recognition at Different Positions Using a Multifunctional Wearable Energy Harvester

Energy Harvesting Opportunities in Geoenvironmental Engineering

Geoenvironmental engineering involves defining solutions for complex problems, such as containment systems management, contaminant transport control, wastewater management, remediation of contaminated sites and valorization of geomaterials and wastes. In the last years, energy harvesting (EH)—or energy scavenging—methods and technologies have been developed to reduce the dependence on traditional energy sources, namely fossil fuels, and nuclear power, also responding to the increase in energy demands for human activities and to fulfill sustainable development goals. EH in geoenvironmental works and the surrounding soil and water environment includes a set of processes for capturing and accumulating energy from several sources considered wasted or unusable associated with soil dynamics; the stress and strain of geomaterials, hydraulic, vibrations, biochemical, light, heating and wind sources can be potential EH systems. Therefore, this work presents a review of the literature and critical analysis on the main opportunities for EH capturing, accumulating and use in geoenvironmental works, among basic electric concepts and mechanisms, analyzing these works in complex conditions involving biological-, chemical-, mechanical-, hydraulic- and thermal-coupled actions, concluding with the main investigation and challenges within geoenvironmental aspects for EH purposes.

Enhanced energy harvesting ability of bismuth sodium titanate/polyvinylidene fluoride composite film-based piezoelectric nanogenerators for mechanical energy scavenging and safety-walker applications

Herein, we proposed a piezoelectric Bi0.5Na0.5TiO3 (BNT)/polyvinylidene fluoride (PVDF) flexible composite film-based peizoelectric nanogenerator (PNG) device as a highly efficient mechanical energy harvester. Initially, the BNT nanoparticles (NPs) with high dielectric constant were synthesized and loaded into a PVDF polymer matrix. The effect of BNT loading on the chemical property, dielectric property, and β phase of PVDF-based composite films was analyzed in depth. The various PNG devices based on the PVDF piezoelectric films with different concentrations of BNT NPs and aluminum electrodes were fabricated. The external force was applied to all the PNGs and their electrical output was systematically investigated to find the optimal concentration of BNT NPs inside the PVDF. The optimized 0.5 wt% BNT loaded PVDF composite film-based PNG device produced a highly efficient electrical output of about 19 V, 1.2 μA, and 3.5 mW/m2. The fabricated PNG device was robust and could generate highly stable electrical output over a long period. A highly efficient external electrical circuit was developed to effectively store the generated electricity from the PNG into various energy storage devices. Furthermore, the generated electrical energy was utilized to charge various energy storage capacitors and to power small electronics. Additionally, the flexible PNG device was demonstrated as a biomechanical energy harvester to convert various human movements into electricity successfully. Owing to the high flexibility, robustness, and energy conversion efficiency of the fabricated PNG device, it is expected to be utilized to harvest various mechanical movements available in daily life through large-scale technology. The unique PNG-powered self-illuminating bracelet-based safety walker system was proposed, which can be utilized in daily life to avoid accidents on roads and for many other applications.

A methodology for low-frequency rotational energy harvesting with synergistic effects of centrifugal softening and passive adaptive barrier reduction

Energy harvesting in rotating environments is significant to realize the condition monitoring of mechanical equipment. In this paper, to accommodate the low-frequency rotating environment, a piezoelectric energy harvester with two magnetic coupled cantilevers perpendicular to each other is designed. The harvester exhibits the magnet-induced nonlinearity, centrifugal softening effect and passive adaptive barrier reduction effect. The influences of these characteristics on the dynamic performance are investigated comprehensively by establishing the electromechanical coupling equations in a rotational coordinate system through the extended Hamiltonian principle. The correctness of the mathematical model and simulation analysis is verified by experiments. Compared with single cantilever based harvester, the system output voltage is boosted by more than 10.56 times over the whole test frequency band (0.6–4 Hz). The significant enhancement of the energy scavenging capability proves its potential for low-frequency rotating applications.

A wearing orientation-independent electromagnetic self-powered sensor for human activity recognition based on biomechanical energy scavenging

Self-powered human activity recognition (HAR) using vibration energy harvesters attracts broad interest in wearable electronics. To address the challenge of making such sensors adaptive to human motions, we design a novel electromagnetic self-powered HAR sensor with an eccentric-rotor-based vibration pick-up structure. Its adaptability to the low-dominant-frequency (<5 Hz) and volatile-direction wrist movement is realized by the low resonant frequency and in-plane rotary responses of this magnetic rotor, promoting the biomechanical motion pick-up. Particularly, its capability of providing repeatable and human-activity-related voltage signals is revealed and proved wearing orientation-independent. On this basis, walking, jogging, and running at 2–8 km/h are recognized precisely by multi-feature-based signal representation and random forest models, achieving comparable classification accuracies over 97% with different wearing orientations. The practicality of this sensor is also enhanced by its light weight and small volume. The proposed sensor and signal analyzing method offer a promising and versatile solution to convenient HAR.

Practical asymmetry and its effects on power and bandwidth performance in bi-stable vibration energy harvesters

Scavenging energy from ambient vibrations using piezoelectric bi-stable energy harvesters (BEHs) has been a research focus in recent years. The typical assumption that BEHs have perfectly symmetric potential profiles is hardly attainable in practice. Unlike previous works which model asymmetry as a quadratic restoring force term, we present a physically quantifiable concept of practical asymmetry degree γ which can be utilized in both theory and experiment. Also, we optimize the nondimensional method by normalizing to the inherent parameters, which guarantees consistent and comparative model analysis. Based on above, a comprehensive study of practical asymmetry’s effect on BEH’s performance is experimentally validated. Results show that for stable inter-well oscillation, asymmetry increases BEH’s output power due to enlarged phase orbit space, but decreases BEH’s bandwidth due to elevated potential barrier. Compared with symmetric BEH, asymmetric BEH improves power by 57.56 % and 26.93 % but reduces bandwidth by 73.81 % and 57.38 % in simulation (γ = 4.08) and in experiment (γ = 4.11), respectively. Initial position in the shallow well improves both power and bandwidth of the asymmetric BEHs. Compared with deep well initial position, shallow well initial position exhibits 41.72 % power improvement and 50.00 % bandwidth increase in experiment (γ = 4.11). Sufficiently large excitation level is required to reach above conclusions, as asymmetric BEHs under small excitations might not reach optimal performance. These results provide instructive insights for designing practical BEHs with improved power and bandwidth performance.

Direct Current Triboelectric Nanogenerators, a Perspective from Material Selections

With the global energy shortages, sustainable energy scavenging from the natural environment is desperately needed. Unlike solar cell or wind power, which depends heavily on weather conditions, triboelectric nanogenerator (TENG) has received extensive attention as an efficient all–weather energy–harvesting technology. Based on the coupling principle of contact electrification (CE) and electrostatic induction, conventional TENGs convert mechanical energy into an alternating current (AC) output. However, the typically distributed sensor systems in the ubiquitous Internet of Things (IoTs) request a direct current (DC) input. Direct current triboelectric nanogenerators (DC-TENGs) with the constant output characteristic are critical to satisfy the above requirements. Here, DC-TENGs were reviewed from the perspective of material selections. As device performance is mainly determined by material properties, the development of DC-TENGs could be divided into three categories based on dielectric materials, semiconductor materials, and materials for iontronic rectifications. The operating mechanism and influencing factors of various types of DC-TENG were summarized, representative applications were demonstrated, and the main challenges of future developments were also discussed.

Air‐cored axial flux permanent magnet generator for direct driven micro wind turbines

AbstractThis paper presents the development of an Air‐Cored Axial Flux Permanent Magnet Generator (ACAF PMG) integrated for direct battery charging scheme for urban and rural micro‐wind turbine applications rated at 1 kW. The proposed generator has a Single Stator Double Rotor configuration with a relatively short axial length. In this paper, the analytical model for generator sizing is presented and the main parameters are defined. Novel analytical model is presented to determine the required number of turns for each phase in order to produce a balanced voltage in the three phases. The generator is electromagnetically analyzed using Finite Element model and simulated using Matlab/Simulink to predict its performance under several operating conditions. The effect of retainment ring type on the generator performance is also demonstrated. The machine is harnessed to a battery bank via a three‐phase fully controlled converter using six bridge thyristors to regulate the output voltage delivered from the generator to the battery. Generator model and simulation results are validated via experimental tests. The preliminary experimental results showed a good match with the simulation results. Moreover, the proposed machine is compared favourably with other counter machines of similar configuration and power ratings in terms of machine size, power‐to‐weight ratio, and voltage regulation. This paper therefore demonstrates the concrete benefits of utilizing the axial flux PMG in scavenging energy to generate electrical power from micro wind turbines.

Coupled iterative partitioning analysis for flow-driven piezoelectric energy harvesters

Scavenging of energy from the environment is an important engineering challenge. Recently, many researchers have investigated flow-driven piezoelectric energy harvesters, which harvest electricity from flow-induced vibration via the piezoelectric effect, and have applied them to drive low-power devices. Such harvesting is a complicated multi-physics problem involving fluid–structure interactions, piezoelectricity, and circuit design. The purpose of this study is to model such harvesting in detail and to solve the detailed model by strong coupling approaches. Although a few studies based on monolithic approaches have been recently reported, there is no study based on iterative partitioning approaches, which offer the advantage of allowing the use of existing sub-solvers. The novelty of the present study is to develop the iterative partitioning method-based analysis system. In this paper, we formulate nonlinear equations for flow-driven piezoelectric energy harvesting, of which unknown is structural displacement. We then provide an algorithm based on the iterative partitioning method. The proposed analysis system comprises an arbitrary Lagrangian–Eulerian-based fluid analysis solver, a monolithic structure–piezoelectricity interaction analysis solver, and a circuit analysis solver. Finally, we show the results of two numerical simulations to validate our proposed analysis systems. The first involves an analysis of piezoelectric energy harvesting in the absence of the effects of the surrounding fluid. The second considers flow-driven piezoelectric energy harvesting. The results of both simulations are in good agreement with those reported in previous studies.

A high-power and high-efficiency mini generator for scavenging energy from human foot movement

A high-power and high-efficiency mini generator for scavenging energy from human foot movement

Enhanced thermoelectric performance via quantum confinement in a metal oxide semiconductor field effect transistor for thermal management

The performance of thermoelectric devices is gauged by the dimensionless figure of merit {{{{{boldsymbol{ZT}}}}}}. Improving {{{{{boldsymbol{ZT}}}}}} has proven to be a formidable challenge given the interdependence of its constitutive quantities, namely Seebeck coefficient, electrical conductivity, thermal conductivity, and temperature. Here, we use quantum confinement to decouple Seebeck coefficient and electrical conductivity to demonstrate an order of magnitude quantum-based enhancement to the thermoelectric figure of merit {{{{{boldsymbol{ZT}}}}}} in complimentary metal-oxide-semiconductor field-effect transistors. While most quantum-based enhancement is done through physical confinement using two-dimensional materials, our approach uses electrical confinement. Because of this, our device is more robust than the two-dimensional materials currently used. We further articulate that improvement by as much as a factor of 50 could be achieved in a practical setting. Our approach further provides a path for monolithic integration of on-chip coolers and energy scavengers with virtually no deviation from the fabrication flow of standard electronics.

Discussion on Secure Standard Network of Sensors Powered by Microbial Fuel Cells.

Everyday tasks use sensors to monitor and provide information about processes in different scenarios, such as monitoring devices in manufacturing or homes. Sensors need to communicate, with or without wires, while providing secure information. Power can be derived from various energy sources, such as batteries, electrical power grids, and energy harvesting. Energy harvesting is a promising way to provide a sustainable and renewable source to power sensors by scavenging and converting energy from ambient energy sources. However, low energy is harvested through these methods. Therefore, it is becoming a challenge to design and deploy wireless sensor networks while ensuring the sensors have enough power to perform their tasks and communicate with each other through careful management and optimization, matching energy supply with demand. For this reason, data cryptography and authentication are needed to protect sensor communication. This paper studies how energy harvested with microbial fuel cells can be employed in algorithms used in data protection during sensor communication.

Exploring the potential of onboard energy scavenging subsystems for generating valuable data

We propose implementing an onboard energy scavenging subsystem utilizing piezoelectric materials, which serves the dual purpose of generating electrical energy and facilitating data acquisition for multifaceted applications. In a practical demonstration, we have engineered a fully functional prototype adept at gathering data via a piezoelectric-centric energy scavenging mechanism. This gathered data is seamlessly synchronized with GPS coordinates and timestamps, meticulously organized within a system architecture, and harnessed through meticulously crafted Python code. The wealth of data that we obtain from an onboard energy scavenging subsystem holds significant potential. It empowers us to discern road irregularities and potholes through intricate analytical methodologies while also facilitating a thorough assessment of asphalt quality. Furthermore, it enables real-time surveillance of vehicular suspension system health and offers a nuanced exploration of driver behavior patterns. In a pragmatic pursuit of actionable insights, the amassed data can be expeditiously conveyed to relevant authorities. These authorities can perform even deeper Artificial Intelligence (AI), Machine Learning (ML), and Deep Learning (DL) to proactively initiate timely corrective measures, thereby elevating road safety standards and ensuring the maintenance of critical infrastructure. The Results and Discussion section underscores the attainment of substantial and noteworthy outcomes, further affirming the significance of our findings.

Suspended-Load Backpacks to Reduce the Cost of Carrying Loads with Energy Scavenging Potential—Part 2: Bio-Inspired Pre-Rotation Design

Backpack transportation is everywhere in daily life. Suspended-load backpacks (SUSBs) based on forced vibration have attracted lots of attention because of their ability to effectively reduce the cost on the body during motion. The smaller the natural frequency of SUSBs, the better the cost reduction. The natural frequency is determined by the elastic components of SUSBs. It is currently common to use rubber ropes and pulleys as elastic components. In the first part of this paper, we propose a pre-compression design for SUSBs, which has a simple structure and breaks through the limitation of rubber material. To make the natural frequency small enough, rubber ropes and compression springs require sufficient space. This leads to the current SUSBs being large and, therefore, not suitable for children to carry. Inspired by biology, here we propose a new design strategy of pre-rotation with pre-rotation spiral springs as elastic components. The pre-rotation design not only has the advantages of avoiding the inconvenience of material aging and the ability to adjust the downward sliding distance of the backpack but also greatly saves the space occupied by the elastic components, which can be adopted by small SUSBs. We have developed a theoretical model of the pre-rotation SUSBs and experimentally confirmed the performance of the pre-rotation SUSBs. This work provides a unique design approach for small SUSBs and small suspended-load devices. And the relative motion between the components inside the SUSB has a huge potential to be used by triboelectric nanogenerators for energy scavenging.