Efficient Energy Harvesting Research Articles

Enhancing the piezoelectric performance of composite PVDF flexible films through optimizing β phase content, investigating additive effects, step‐wise polarization, and thermal pressing time for energy harvesting applications

AbstractPolyvinylidene fluoride (PVDF), known for its piezoelectric versatility, emerges as a key contender for advancing efficient and sustainable energy harvesting in nanogenerators. This study explores the potential enhancement of piezoelectric properties in flexible PVDF polymers, employing a comprehensive approach through the solution casting method. The investigation integrates diverse additives, thermal treatments, and polarization methods to optimize performance, focusing on the impact of the β phase transition on electrical voltage generation. Utilizing the Taguchi experimental design, the study identifies optimal conditions for the composite PVDF film (OPT‐PVDF) through FT‐IR, XRD, and DSC analyses, with output voltage measurements confirming superior performance compared to pure PVDF (P‐PVDF). Specifically, BN‐doped PVDF films, with an 80% β phase content, achieve an impressive 6.48 V output voltage. This research underscores PVDF's potential for energy harvesting, emphasizing the pivotal role of optimizing β phase content, additive strategies, and the effects of polarization and thermal treatments. The study further evaluates the effect and necessity of subsequent thermal treatment and step‐wise polarization effects on the composite PVDF film material. The findings indicate that BN‐doped composite PVDF films, produced under optimal conditions, exhibit advanced piezoelectric properties.

Design and investigation of small-scale long-distance RF energy harvesting system for wireless charging using CNN, LSTM, and reinforcement learning

Introduction: The energy supply challenge in wireless charging applications is currently a significant research problem. To address this issue, this study introduces a novel small-scale long-distance radio frequency (RF) energy harvesting system that utilizes a hybrid model incorporating CNN, LSTM, and reinforcement learning. This research aims to improve RF energy harvesting and wireless charging efficiency.Method: The methodology of this study involves data collection, data processing, model training and evaluation, and integration of reinforcement learning algorithms. Firstly, RF signal data at different distances are collected and rigorously processed to create training and testing datasets. Next, the CNN-LSTM model is trained using the prepared data, and model performance is enhanced by adjusting hyperparameters. During the evaluation phase, specialized test data is used to assess the accuracy of the model in predicting RF energy harvesting and wireless charging efficiency. Finally, reinforcement learning algorithms are integrated, and a reward function is defined to incentivize efficient wireless charging and maximize energy harvesting, allowing the system to dynamically adjust its strategy in real time.Results: Experimental validation demonstrates that the optimized CNN-LSTM model exhibits high accuracy in predicting RF energy harvesting and wireless charging efficiency. Through the integration of reinforcement learning algorithms, the system can dynamically adjust its strategy in real time, maximizing energy harvesting efficiency and charging effectiveness. These results indicate significant progress in long-distance RF energy harvesting and wireless charging with this system.Discussion: The results of this study validate the outstanding performance of the small-scale long-distance RF energy harvesting system. This system is not only applicable to current wireless charging applications but also demonstrates potential in other wireless charging domains. Particularly, it holds significant prospects in providing energy support for wearable devices, Internet of Things (IoT), and mobile devices.

Smart Footstep Energy Harvesting System

This research paper introduces a novel approach to footstep energy harvesting by integrating piezoelectric sensors into flooring surfaces. The project aims to generate sustainable electrical power from footsteps, contributing to the development of energy-efficient systems. The proposed system incorporates a unique feature that enables users to easily identify and address sensor failures or damages. The core components of the system include piezoelectric sensors strategically placed in high-traffic areas, an Arduino microcontroller for signal processing and energy management, and a rechargeable battery for energy storage. A rectifier circuit is employed to convert AC signals generated by the sensors to DC, while a voltage regulator ensures a stable output voltage. The energy harvested is stored in the battery, which is connected to a USB charging module capable of charging electronic devices. To enhance the system's usability and maintenance, LEDs are integrated with each piezoelectric sensor. These LEDs act as indicators for sensor status, allowing users to visually identify any damaged or failed sensors. The Arduino code is designed to continuously monitor sensor values and activate the corresponding LED when a sensor falls below a predefined threshold, signaling a potential issue. This unique feature enhances user awareness, simplifies troubleshooting, and aids in the efficient maintenance of the energy harvesting infrastructure. The research focuses on the practical implementation of the system, exploring its effectiveness in real-world scenarios. Various aspects, such as energy generation efficiency, adaptability to different environments, and the ease of sensor failure identification, are evaluated through extensive experimentation. The paper discusses the system's potential applications, including sustainable power generation for small electronic devices and its integration into smart infrastructure. The proposed Smart Footstep Energy Harvesting System with Sensor Failure Identification addresses a crucial aspect of sustainability and smart infrastructure management. The findings from this research contribute to the growing field of energy harvesting technologies and pave the way for future developments in efficient, user-friendly, and maintainable footstep energy harvesting systems.

Event-driven piezoelectric energy harvesting for railway field applications

Piezoelectric energy harvesters (PEHs) hold promises for revolutionizing railway structural health monitoring (SHM). However, the challenges of designing high-robust PEHs for handling complex and ever-shifting vibrations in practical railway scenarios remain formidable. Unlike conventional methods that align the fundamental frequency of the PEH with the dominant frequency of the vibration source, this study employs an event-driven enhancement method. This study commences by employing a high-fidelity dynamic model of the PEH and an advanced vehicle-track coupled dynamic model to evaluate energy harvesting efficiency across various railway scenarios. The vehicle-induced track vibrations are predicted across various train speeds, track structures, and track irregularities, considering 12 distinct vehicle-track conditions and totaling 3600 simulation datasets, each representing a specific event. We employ the particle swarm optimization (PSO) algorithm to identify optimal PEH designs for different events. To streamline this process, instead of offering one optimal solution for each event, we employ the K-means algorithm to cluster similar events. Subsequently, we choose the centroid design for each cluster as the representative solution for events within that cluster. This approach allows us to use a limited number of representative PEHs to effectively address most events across different clusters. Finally, we thoroughly examine and evaluate the dynamic responses of these representative designs to demonstrate their robust performance. This study explores PEH design optimization from a fresh perspective, bridging the gap between theoretical design and practical implementation in rail transportation systems.

Uniaxially drawn poly (L-lactic acid)/ poly (vinylidene fluoride) polymer blend as a promising piezoelectric material: Hysteresis and resonance spectroscopy study

This study explores the potential for piezoelectricity in a blend of polyvinylidene fluoride (PVDF) and poly-L-lactic acid (PLLA) prepared using the solution casting method. Dielectric frequency measurements across a range of 102 to 106 Hz revealed piezoelectric resonance within a broader dielectric relaxation regime. Analysis of the resonance spectra for length and width vibrational modes enabled the determination of the piezoelectric tensor components of the PVDF/PLLA blend. The blend exhibited enhanced ferroelectric polarization reversal, remnant polarization, and coercive field compared to pristine PVDF samples. The piezoelectric constants d31 and d14 (d36 of the blend) were determined. Mechanical drawing and poling techniques were employed to generate multiple piezoelectric constants, allowing for efficient energy harvesting from various directions. This flexible blend offers promising prospects for versatile energy conversion applications.

Designing umbrella-shaped heat-induced channels for oriented heat transfer in asphalt mixtures

In order to regulate the directional transfer and collection of heat in pavements, a novel solution has been proposed, named Umbrella-Shaped Heat-induced Channels (UHC). This UHC is composed of carbon fibers with high axial thermal conductivity and a heat-induced layer. A finite element heat transfer model is employed to analyze the heat transfer behaviors of asphalt mixtures. And an indoor irradiation experiment is conducted for feasibility verification. The results indicate that enhancing the thickness of the heat-induced layer or increasing the disparity in thermal conductivity between the heat-induced layer and asphalt mixtures can enhance the oriented heat transfer effect of UHC. The heat-induced layer boosts the horizontal heat flux of the UHC by 60.3% compared to the side without the heat-induced layer. This enhancement is attributed to the secondary thermal convergence effect of the heat-induced layer, which further amplifies the thermal induction and heat collection capabilities of UHC. This phenomenon is crucial for achieving directed heat conduction. The designed UHC can enhance the heat transfer efficiency of the asphalt pavement in the designated direction. Furthermore, it can alleviate the heat island effect, address permafrost thawing and high-temperature rutting issues, and enhance the efficiency of solar energy harvesting on pavements.

Fully passive model-based numerical analysis of the trailing-edge flexibility of hydrofoil on energy harvesting performance

The oscillating hydrofoil, a device used for collecting environmentally friendly tidal energy, is the focus of the study. The flexibility of the hydrofoil's trailing edge can impact its surface pressure distribution, lift, and moment characteristics. To improve the energy harvesting performance of oscillating hydrofoils, it is important to conduct thorough research on their energy harvesting mechanism. Therefore, numerical analysis is employed to develop a numerical model of the fully passive oscillating hydrofoil with the flexible trailing edge. The dynamic development behavior of surface vortices on hydrofoils is analyzed, demonstrating that the fluid–structure interaction between the hydrofoil and the surrounding fluid alters the hydrofoil's motion. The vortex patterns and pressure distribution on the hydrofoil surface are also affected, ultimately influencing the energy harvesting performance. By optimizing the flexibility coefficient of the fully passive oscillating hydrofoil with a flexible trailing edge, the energy harvesting performance of the oscillating hydrofoil is improved. When the maximum chord offset δm= 0.1c and the flexibility coefficient n= 2, the energy harvesting efficiency is 31.37%, and the average power coefficient is 1.17. Therefore, increasing the tail flexibility can be considered to enhance energy harvesting performance when designing the fully passive oscillating hydrofoil. The research provides a comprehensive analysis of energy harvesting performance, addressing the dynamic problem of the fully passive oscillating hydrofoils with flexible trailing edges. The findings of this study may provide guidance for the design and optimization of tidal energy harvesting devices with similar structures.

Development of a dual-axis solar tracker for efficient sun energy harvesting

Climate change, global warming, and rising fossil fuel pose significant challenges in present days across worldwide. To combat these issues, governments and organizations are promoting renewable energy sources, such as solar power, which converts sunlight into electricity or thermal energy. In the current scenario, static-oriented Photovoltaic (PV) panels are hampered by fluctuations in the sun's trajectory, leading to suboptimal solar energy conversion. To address these issues, this manuscript proposes a low-cost prototype of a two-axis solar tracker that integrates four optical sensor modules as feedback sensors and two direct current geared motors to maximize solar energy harvesting. Comparative analysis between a fixed-oriented PV panel and the solar tracker, using conventional on–off and artificial intelligence-based fuzzy logic control methods, verifies the two-axis solar tracker's performance. The fuzzy logic controller-based solar tracker net energy gains approximately 14.2% more power than the fixed-oriented PV panel daily and boasts an average tracking error of 0.29°, indicating its reliability.

Dual Frequency Energy Harvesting System Based on Planar Inverted F-shaped Antenna

<p>With the expansion of Internet of things (IoT) scale and the extension of its application fields, node energy acquisition has become one of the constraints on the development and application of IoT technology. Wireless energy acquisition is faced with the challenge of how to enhance power conversion efficiency under low input power in the broadband range. This study aimed to improve the capability of energy collection and transmission in wireless communication, an efficient dual-frequency energy harvesting system was proposed, moreover a novel dual-frequency planar inverted-f antenna (PIFA) and its energy conversion circuit for Radio frequency (RF) energy harvesting were designed by studying the characteristics of ambient RF energy and antenna. The developed antenna is designed and manufactured for GSM 900mhz or DCS 1.8 GHz to harvest the ambient energy provided by nearby devices. It is proved that the new dual-frequency antenna still has high efficiency when the input power is less than -20 dbm, and can maximize the receiving energy. The system works with an energy conversion and storage module to convert weak signals into required voltages, the simulation and test results show that the maximum conversion efficiency of the prototype is about 65% at 920MHZ and 1.8GHz at -20 dBm input power.</p> <p> </p>

Study on energy capture characteristics of piezoelectric stack energy harvester for railway track

Railway traffic plays a pivotal role within the current transportation system, with ensuring its safety being of paramount importance. Real-time monitoring of train track health through sensor technology has emerged as a significant approach for achieving this objective. However, a persistent challenge lies in providing cost-effective and stable power to sensors in remote areas. This paper proposes the utilization of a novel piezoelectric stack energy harvester in railway systems to address this issue. The substantial and consistent vibration energy produced by railway operations makes it an ideal source for energy harvesting, unaffected by environmental conditions. Through simulation analysis and experimental verification, this study explores the impact of load size, load frequency, and external resistance on the energy harvesting efficiency of the proposed piezoelectric stack energy harvester. The results indicate that the output power of the energy harvester increases with the load size. Furthermore, the frequency significantly influences the energy capture efficiency when below 8 Hz, with minimal impact on frequencies above 8 Hz. Interestingly, the load dramatically affects the energy capture efficiency, even at higher frequencies. With the external resistance set to 250 kΩ, the harvester achieves a maximum output power of 42.76 mW.

Tunable topological edge states and energy harvesting of piezoelectric-inductance phononic crystals based on Su-Schrieffer-Heeger model

Based on Su-Schrieffer-Heeger (SSH) model, a one-dimensional tunable topological phononic crystal (PnC) was designed. Piezoelectric column with an inductance was designed as a scatterer embedded in the epoxy resin matrix. And the introduce of an inductance into each piezoelectric column resulted in a new Dirac point in band structure. Subsequently, the new Dirac point was operated to open/close by altering the intracell distance, and the trivial and non-trivial phase transition occurred simultaneously, which demonstrated the topological properties of PnC. The results showed that the obvious edge state was observed at the frequencies of 16.334–27.226 kHz by varying the inductance from 2.5mH to 9.5mH. And the immune of the edge state to the local defects was also verified. Furthermore, the energy harvesting of the wave propagation was performed, and the energy harvesting efficiency of the edge state case was about 40 times larger than that of bulk state case.

Ionic Rectification by Dynamic Regulation of the Electric Double Layer at the Hydrogel Interface.

Hydrogels play a pivotal role in the realm of iontronics, contributing to the realization of futuristic human-machine interactions. The electric double layer (EDL) between the hydrogel and electrode provides an essential ionic-electronic coupling interface. While prior investigations primarily delved into elucidating the formation mechanism of the EDL, our study shifts the focus to showcasing the current generation through the mechanical modulation of the EDL at the hydrogel-metal interfaces. The dynamic EDL was constructed by the mechano-driven contact-separation process between the polyacrylamide (PAAm) hydrogel and Au. Influencing factors on the dynamic regulation of the EDL such as ion concentration, types of salt, contact-separation frequency, and deformation degree were investigated. Dehydration usually limits the practical applications of hydrogels, and it is a long-standing and difficult problem. However, it seemed to be able to slow the EDL formation process here, resulting in a sustained continuous direct current signal output. Such hydrogel iontronics could rectify the displacement electronic current of a triboelectric nanogenerator by the ionic current. The directional migration of ions could be further enhanced by using charge-collecting metals with different work functions, for example, Au and Al. It offers a paradigm to enable ionic rectification that could be seamlessly incorporated into electronic systems, ushering in a new era for efficient energy harvesting and biomimetic nervous systems.

Multifunctional Models in Digital and Physical Twinning of the Built Environment—A University Campus Case Study

The digital twin (DT) concept has been developed for a single function in previous studies. This study aims to empower DTs with a layered integration of multifunctional models in the built environment. It develops a framework of DT modules in three hierarchical tiers: region, asset, and system; defines a new concept of the degree of digital twinning (DODT) to the real world by the number of models enabled by a common DT platform; and enables spatiotemporal analysis in multiple scales to couple nonstructural with structural building components and connect the built environment to planning constructions. While the asset and system DTs focus on the lifecycle management of buildings and infrastructure systems, the region DT addresses diverse modeling approaches for a comprehensive management of the built environment as demonstrated on a university campus. The DODT allows the value-driven digital replication of a physical twin at different levels. For the campus case study, the DODT is eight, for building and infrastructure planning, condition assessment of building envelopes, construction management for efficiency and quality, damage/cost scenario studies under earthquake events, energy harvesting efficiency, environmental planning for flood zone susceptibility, master planning for green space development, and security protocol development.

Rational designing of phenothiazine dioxide based hole transporting materials for efficient perovskite solar cells

In this study, we design five novel non-fullerene end capped acceptor based efficient hole transporting materials (HTMs) from phenothiazine dioxide-based core. MPW1PW91 functional with a 6-31G basis set was employed for all DFT calculations and simulation analysis. By substituting acceptor groups in PDO2, numbers of parameters like band gaps, the frontier molecular orbitals (FMOs), higher absorption parameters, and electronic properties like ionization potential, electron affinity, binding energy, and light harvesting efficiency (LHE) were well tuned. In addition, significant variations in other geometrical parameters such as dipole moment, and reorganizational energy parameters were also noticed for the derived molecules compared to the reference molecule (R). Device performance was analyzed by performing calculations of open circuit voltage (VOC) and fill factor (FF). Consequently, all the designed derivatives demonstrated an improved VOC of 0.84 V for an optimized designed structure. In comparison, it was limited to a VOC of 0.57 V for the reference (R) PDO2, displaying an increment in efficiency which is essential to use these molecules as highly efficient HTMs for perovskite solar cell devices in the future.

Performance analysis of transmit antenna selection and maximum‐ratio combining in overlay networks powered by harvested energy

AbstractWe aim to improve both the energy harvesting efficiency and communication reliability of overlay networks powered by harvested energy. To this end, multiple antennas are considered to collect energy efficiently and perform reliable decoding by selecting the transmitting antenna and applying maximum‐ratio combining. To further improve communication reliability, nonorthogonal multiple access (NOMA)‐relied decoding is applied to the secondary receiver. For performance evaluation, exact formulas for the secondary/primary outage probability are derived in a closed form. The evaluation results show that the proposed method substantially outperforms a baseline without the NOMA‐relied decoding in all the system settings. The performance of the proposed method is determined by multiple specifications and optimized by allocating the times for energy harvesting and information processing.

Perovskite Nanocrystals Induced Core-Shell Inorganic-Organic Nanofibers for Efficient Energy Harvesting and Self-Powered Monitoring.

The emerging field of wearable electronics requires power sources that are flexible, lightweight, high-capacity, durable, and comfortable for daily use, which enables extensive use in electronic skins, self-powered sensing, and physiological health monitoring. In this work, we developed the core-shell and biocompatible Cs2InCl5(H2O)@PVDF-HFP nanofibers (CIC@HFP NFs) by one-step electrospinning assisted self-assembly method for triboelectric nanogenerators (TENGs). By adopting lead-free Cs2InCl5(H2O) as an inducer, CIC@HFP NFs exhibited β-phase-enhanced and self-aligned nanocrystals within the uniaxial direction. The interface interaction was further investigated by experimental measurements and molecular dynamics, which revealed that the hydrogen bonds between Cs2InCl5(H2O) and PVDF-HFP induced automatically well-aligned dipoles and stabilized the β-phase in the CIC@HFP NFs. The TENG fabricated using CIC@HFP NFs and nylon-6,6 NFs exhibited significant improvement in output voltage (681 V), output current (53.1 μA) and peak power density (6.94 W m-2), with the highest reported output performance among TENGs based on halide-perovskites. The energy harvesting and self-powered monitoring performance were further substantiated by human motions, showcasing its ability to charge capacitors and effectively operate electronics such as commercial LEDs, stopwatches, and calculators, demonstrating its promising application in biomechanical energy harvesting and self-powered sensing.

Numerical study on the energy-harvesting performance of a semi-activated coupled-pitching hydrofoil in shear flows

A two-dimensional numerical model of a semi-activated coupled-pitching hydrofoil was established using the computational fluid dynamics software ANSYS Fluent. The kinematic response, hydrodynamic characteristics, and energy-harvesting performance of the hydrofoil in shear flow were investigated. The coupled-pitching hydrofoil achieved a stable limited-cycle passive-pitching motion and efficient energy harvesting in shear flows under various shear rates, pitching amplitudes, and reduced frequencies. The flow structures, pressure distributions, and hydrodynamic torque were analyzed to reveal the mechanism of the stable passive-pitching motion of the coupled-pitching hydrofoil in shear flow. The stable passive-pitching motion was dominated by the hydrodynamic torque, which was equivalent during the upward and downward strokes. Shear flow has a certain degree of influence on energy-harvesting efficiency. The energy-harvesting efficiency decreased with increasing shear rate. When the activated-pitching amplitude is small, the effect of shear rate on energy-harvesting performance was limited. The effect of shear rate was enhanced as the activated-pitching amplitude increased. The average relative difference in the energy-harvesting efficiency in the uniform and shear flows was 15 %, when the activated-pitching amplitude was 70° and the shear rate was 1.0. The peak value of the efficiency can reach 19.8 % when the shear rate was 1.0. The coupled-pitching hydrofoil is adaptable to shear flows. The results of this study provide valuable information for the application of coupled-pitching hydrofoils under real tidal flow conditions.

A real-time, self-powered wireless pressure sensing system with efficient coupling energy harvester, sensing, and communication modules

Self-powered wireless sensing systems (SP-WSSs) based on triboelectric nanogenerators (TENGs) are promising in the era of the Internet of Things. However, due to the complex structure, SP-WSSs have high power consumption and cannot work in real time. Here, through efficient coupling among energy harvesting, sensing, and communication modules, the structure of SP-WSS is simplified and the power consumption is reduced for real-time sensing. Firstly, since the sensing and communication are coupled by an LC circuit composed by a handmade capacitive pressure sensor and an inductance coil, the energy for one sensing-communication cycle is reduced to 9 μJ, and the SP-WSS can send a signal every 27 ms at 1 Hz working frequency of TENG. Then, the sensing LC circuit is directly triggered by the TENG using the triboelectric plasma as a switch. Since the ultra-fast switching characteristics of triboelectric plasma (13.2 ns), the communication frequency can reach 72.55 MHz for real-time pressure sensing. And the equivalent impedance of TENG is reduced by triboelectric plasma to achieve impedance matching with the LC circuit, which leads to the energy conversion efficiency of 56% and enables signal transmission distance up to 40 m with a peak-to-peak voltage (Vp-p) of 3 V. These results are new records for SP-WSSs. Finally, a photodetector is incorporated into the circuit, demonstrating the system's capability for collaborative sensing of light intensity and pressure. This work presents a feasible scheme of real-time SP-WSSs, which will greatly promote the practical application of SP-WSSs.

Multifunctional Piezoelectric Yarns and Meshes for Efficient Fog Water Collection, Energy Harvesting, and Sensing

Given global water scarcity and the quest for sustainable energy, there's a pressing need for integrated approaches addressing water‐energy interdependence worldwide. A practical approach for this challenge involves the implementation of fog water collectors. Herein, a polyvinylidene fluoride (PVDF) multifunctional device capable of harvesting water and electricity from wind is developed and tested, collecting up to 365 mg cm−2 h−1 of fog water. Due to the piezoelectric nature of electrospun PVDF, these yarns and meshes not only serve as piezoelectric sensors, enabling the detection of incoming fog flow and determination of its speed and, bust also harvest electricity by charging a capacitor, making it a green and renewable power source. In this study, promising insights are offered into developing efficient fog water collection methods and utilizing piezoelectric fiber‐based yarns and meshes for multifunctional applications in sustainable water management, energy harvesting, and sensing in a single device.

Preventing degradation of thermoelectric property after aging for Bi2Te3 thin film module

In response to growing environmental consciousness and the global commitment to reduce carbon emissions, the advancement of efficient energy harvesting has become an imperative objective. A thermoelectric device stands out for its quiet and dependable operation devoid of moving components, directly translating waste heat into electrical energy. For practical applications, the metal electrodes will be deposited on both ends of the thermoelectric thin films. The migration of atoms from these electrodes significantly influences module performance. The significance of long-term aging is critical when modules are intended for practical application. In this study, Cu and Ni were selected as electrode materials due to their commendable electrical conductivity. The investigation delves into the diffusion behavior and interfacial stability of Cu/Bi2Te3/Cu and Ni/Bi2Te3/Ni samples, unraveling insights through prolonged aging process. Cu atoms diffused into the Bi2Te3 film and formed Cu2−xTe intermetallic compounds on Bi2Te3 surface. Conversely, Ni atoms diffuse into the Bi2Te3 layer by approximately 50 nm. Long-term aging, inevitably, results in degradation in the power factor (PF) of Ni/Bi2Te3/Ni samples, attributed to the transformation of n-type Bi2Te3 to p-type owing to the formation of BiTe. antisite defects. However, Cu diffusion exerts a significant influence on Cu/Bi2Te3/Cu samples. The incorporation of Cu diffusing from the electrodes mitigates PF deterioration following extended aging. This study focuses on the effect of diffusion on thermoelectric properties and offers promising insights for enhancing the durability, efficiency, and application of thermoelectric thin film modules.