Energy Harvesting System Research Articles

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.

Vibration Energy Harvesting with Printed P(VDF:TrFE) Transducers to Power Condition Monitoring Sensors for Industrial and Manufacturing Equipment

A vibration energy harvesting system based on fully printed piezoelectric transducers is realized. The transducers have a butterfly‐like architecture based on two single‐optimized cantilevers with a resonance frequency tuned to 49.5 Hz and can be easily mounted to an industrial engine. By comparing single‐ and multistack configurations of the piezoelectric layers combined with full‐wave or voltage doubler rectifiers, the power transfer characteristics and impedance can be matched to the electrical requirements of the sensing circuitry. A single stack with 21 μm thickness results in the maximum power output of 14.4 μW at a vibration velocity of 11.5 mm s−1, typical for industrial engines. The system is used to power a wireless sensor node on a 1 kW rotary pump in normal operation. The system can harvest up to 138 mJ within 24 h, sufficient for daily remote monitoring of the engine's vibration spectrum and temperature state. The system is thus suitable as a low‐cost, ecofriendly power source for industrial IoT applications.

Triboelectric nanogenerators based on hydrated lithium ions incorporated double-network hydrogels for biomechanical sensing and energy harvesting at low temperature

Conductive hydrogels with flexibility, anti-freezing ability and functionality have garnered significant attention in developing of advanced triboelectric nanogenerators (TENGs). Herein, a tough, adhesive, and anti-freezing ionic double-network conductive hydrogel (referred as Glu/P(HEA-co-AA)-Fe/LiCl) was prepared by choosing glucan as the first network, Fe3+-COO- metal coordination crosslinked poly(2-Hydroxyethyl acrylate-co-acrylic acid) (P(HEA-co-AA) as the second network, which were crosslinked by multiple hydrogen bonds in the presence of hydrated lithium ions ([Li(H2O)n]+). The hydrogel exhibited excellent mechanical properties (toughness of 16.26 MJ/m3, tensile stress of 4.15 MPa, tensile strain of 1213%, compressive stress of 2.98 MPa under 80% compressive strain), strong adhesion (30.84 kPa for Ecoflex), and satisfactory conductivity (0.43 S/m) even at −18°C. The TENGs based on Glu/P(HEA-co-AA)-Fe/LiCl hydrogel (GP-TENGs) proved its applicability to display excellent electrical output performance (VOC = 182.42 V, ISC = 2.61 μA, and QSC = 63.37 nC) at 25°C, outstanding fatigue resistance (> 5000 consecutive taps), and long-term anti-freezing ability (a VOC of 163.58 V after one-month cryostorage). Furthermore, GP-TENGs can be utilized as biomechanical sensor with ultra-low pressure detection limit (0.016 kPa) and high pressure sensitivity of 0.336 kPa−1 (0.016–1.6 kPa), capable of accurately detecting various human motions, also as energy harvesting devices to power small electronic devices with self-powered systems operating at −18°C. This study developed a strategy for building an anti-freezing hydrogel with high strength and strong adhesion, further expanding the potential applications of hydrogel-based sensors and energy harvesting systems in low temperature environment.

Vortex-plate interaction in wake-induced vibration: A study of single and parallel flat plates behind a cylinder

This numerical study investigates the wake-induced vibration of single or parallel flat plates mounted in the wake of a circular cylinder in laminar flow. The results highlight the critical role of flat plate positioning, as it influences their ability to act as control mechanisms or experience significant vibrations. For a single plate, mounting outside the critical position initiates large amplitude vibrations, gradually decreasing as the plate moves away from the horizontal axis. Additionally, vibrations with moderate amplitudes are observed at specific short horizontal positions due to variations in the near-wake structure. In the case of parallel plates constrained to vibrate independently, vibrations only occur when there is sufficient space for shear-layer interaction. Different vortex suppression and plate vibration mechanisms are identified by adjusting the vertical gap, where increasing the gap reduces the non-vibrating zone. The study also examines a range of reduced velocities, revealing that although the plate(s) follow the upstream cylinder's shedding frequency in all configurations, this frequency may be affected and altered in short gaps. Comparing single and parallel plates demonstrates their potential for designing energy harvesting systems. However, parallel plates offer a slight advantage due to using independent objects within a relatively identical area.

Research on a rotary piezoelectric energy harvester based on movable magnets

A hybrid energy harvester (HEH) is designed using a movable magnet to harvest the mechanical energy for rotational motion. One movement of the movable magnet can generate electricity from piezoelectric nanogenerators (PENG) and electromagnetic generators (EMG), improving the energy conversion efficiency of HEH. The main factors affecting the motion characteristics of active magnets (number of magnets and magnet diameter) are illustrated through theoretical modeling and simulation, and the voltage characteristics of EMG and vibration characteristics of PENG are analyzed. According to the main factors affecting the motion characteristics, the experimental testing system was set up. The results show that the voltage of PENG and EMG can be up to 6.55 V and 1.37 V, respectively as the magnet diameter is 10 mm and the number of magnets is 5. The maximum power of PENG is 2.4 mW at 30 kΩ, and the power of EMG is 0.49 mW at 4 kΩ. The application experiment also proves the feasibility of the practical application of R-PEH, which provides a new solution for the research of hybrid energy harvesting systems.

Designs of Energy Harvester for Wireless Sensor Networks

An essential part of the IoT architecture are wireless sensor networks. There has been extensive study done to identify alternative methods of powering wireless sensor networks because the nodes of wireless sensor networks are mostly power constrained. This study mainly introduces three energy collector solutions that can power wireless sensors. They are an electromagnetic vibration energy harvesting system that powers the light source of the fiber Bragg grating sensor, a solar energy collection system that uses ambient photovoltaic energy, and a wind energy harvester that uses gas elastic vibration to convert wind energy into electrical energy. The solar energy collection system is based on maximum power point tracking, in which the solar panels can provide 3W of power with a high efficiency of up to 96%; the wind energy harvester is composed of a wind generator and a power management unit, capable of operating at wind speeds of 2-9m/s, providing 70mW of power. Besides, the electromagnetic vibration energy harvesting system provides an average power output of approximately 40mW when subjected to acceleration levels greater than 0.05g. These results can serve as solutions for sustainable power output.

Green Energy Harvesting and Management Systems in Intelligent Buildings for Cost-Effective Operation

Nowadays, the rise of Internet of Things (IoT) devices is driving technological upgrades and transformations in the construction industry, the integration of IoT devices in buildings is crucial for both the buildings themselves and the intelligent cities. However, large-scale IoT devices increase energy consumption and bring higher operating costs to buildings. Therefore, harvesting the ambient cost-effective and clean energy sources is essential for the future development of intelligent buildings. In this work, we investigate the feasibility of integrating a typical triboelectric droplet energy harvester (DEH) into buildings. We demonstrate the energy harvesting capabilities of DEH on different sloped roof surfaces and complex curved building surfaces by simulating rainy weather with various rainfall intensities. The results indicate energy harvesting efficiency increases with larger tilt angles, which guides future smart architectural designs. This work is significant for the future integration of diversified, all-weather green energy collection and management systems, including raindrop energy, wind power generation, and solar energy, which will contribute to energy conservation and cost control in the next generation of smart buildings.

A complete artificial intelligence pipeline for radio frequency energy prediction in cellular bands for energy harvesting systems

Radio Frequency (RF) energy harvesting has been used to power wireless and low-powered devices. However, RF energy harvesting has limitations in terms of the amount of power that can be collected based on signal availability. Hence, energy prediction is essential to improve energy harvesting circuits' performance. Previous research has mainly focused on improving power harvesting policies or theoretically estimating the harvested energy. Very few works have considered the prediction of the RF signal as time series data using real RF measurements. Moreover, challenges such as the power consumed by the circuit's harvesting decisions and the impact of outliers on the model performance haven't been addressed yet. This paper presents a complete pipeline for developing the best predictive model for RF energy in cellular frequency bands. Real-time measurements are taken in different frequency bands using software-defined radio technology. We use four artificial intelligence techniques to model the RF energy signal. Additionally, we propose an optimized model with an enhanced loss function, which makes the model more resilient to anomalies, saving computational power and time consumed in cleaning the data. The four algorithms are investigated, and their prediction accuracies are compared. The average power of a period of 5 min is accurately forecasted. Numerical results in the 1960 MHz band show that long short-term memory has the best performance, followed by the DeepAR algorithm with prediction accuracies of 95.76% and 95.02%, respectively. Moreover, the proposed optimized model showed a 32.2% lower prediction error than the traditional models.

Impact of the structural interplay between methyl amine cation and inorganic lead-halide cage of organic perovskites on the optoelectronic properties

Energy harvesting systems using organic–inorganic metal perovskite materials are the subject of active research and development. The synthesis protocols as well as the composition, structure, and stability of these materials are still up for dispute. There are relatively few studies available correlating the relation between the optical band gap and the composition of bulk perovskite materials. Given this, the primary goal of this work is to investigate the influence of structural interplay between methyl amine cation and an inorganic lead-halide cage of organic perovskites by varying the halide functionality of lead halide. Three different products have been synthesised, namely: Methyl ammonium lead iodide-chloride (CH3NH3PbICl2), methyl ammonium lead iodide-bromide (CH3NH3PbIBr2) and methyl ammonium lead iodide (CH3NH3PbI3). This work is a first-hand report that sheds light on the importance of the interplay between the electrostatic forces generated by the methyl ammonium group and the metal halide framework of organic perovskite on its optoelectronic properties.

Exploring challenges and potential for a commercially viable piezoelectric energy harvesting system—Can Energy-as-Data concept thrive?

Over the past two decades, piezoelectric energy harvesting systems have undergone extensive research, spanning from materials to devices and electronics. Recently, there has been a notable introduction of the term “self-powered sensors,” which essentially refers to conventional, older passive sensors, associated with piezoelectric (or triboelectric) nanogenerators. Unfortunately, neither approach has yet yielded a successful market example. The primary challenge seems to lie in the intermittent nature of ambient kinetic energy input to these harvesters, despite the high output power density of piezoelectric energy harvesters. This article emphasizes the concept of Energy-as-Data, holding promise for a potentially brighter future for commercializable piezoelectric energy harvesting systems. The key advantage offered by this concept is the substantial extension of battery life through the optimization of data acquisition protocols. This involves transitioning from the traditional passive sensing mode with a high sampling rate to an extremely low duty cycle. This transition allows the harvested energy, accumulated in an energy storage unit over a specific interval, to be translated into critical information regarding kinetic environmental changes during that period. The article also discusses the broader context that necessitates the Energy-as-Data concept, establishing it as one of the few viable pathways to cultivate specialized markets for piezoelectric energy harvesting.

Decoding Niobium Carbide MXene Dual-Functional Photoactive Cathode in Photoenhanced Hybrid Zinc-Ion Capacitor.

The coupling of energy harvesting and energy storage discrete modules in a single architecture as a "two-in-one" concept is significant in off-grid energy storage devices. This approach can decrease the device size and the loss of energy transmission in common integrated energy harvesting and storage systems. This work systematically investigates the photoactive characteristics of niobium carbide MXene, Nb2CTx, in a photoenhanced hybrid zinc-ion capacitor (P-ZIC). The unique configuration of the Nb2CTx photoactive cathode absorbs light to charge the capacitor and enables it to operate continuously in the light-powered mode. The Nb2CTx-based P-ZIC shows a photodriven capacitance enhancement of over 60% at the scan rate of 10 mV s-1 under 50 mW cm-2 illumination with 435 nm wavelength. Furthermore, a photoenhanced specific capacitance of ∼27 F g-1, an impressive photocharging voltage response of 1.0 V, and capacitance retention of ∼85% (over 3000 cycles) are obtained.

Flutter-Driven Piezoelectric Wind Energy Harvesting System Based on PVDF Nanofiber for Low Power Applications

Flutter-Driven Piezoelectric Wind Energy Harvesting System Based on PVDF Nanofiber for Low Power Applications

Synergistic Hybrid Marine Renewable Energy Harvest System

This paper proposes a novel hybrid marine renewable energy-harvesting system to increase energy production, reduce levelized costs of energy and promote renewable marine energy. Firstly, various marine renewable energy resources and state-of-art technologies for energy exploitation and storage were reviewed. The site selection criteria for each energy-harvesting approach were identified, and a scoring matrix for site selection was proposed to screen suitable locations for the hybrid system. The Triton Knoll wind farm was used to demonstrate the effectiveness of the scoring matrix. An integrated energy system was designed, and FE modeling was performed to assess the effects of additional energy devices on the structural stability of the main wind turbine structure. It has been proven that the additional energy structures have a negligible influence on foundation/structure deflection (<1%) and increased system natural frequency by 6%; thus, they have a minimum influence on the original wind system but increased energy yield.

Research and development of a new combination of piezo-thermoelectric energy harvester systems from roadways

Due to the problems associated with fossil fuels, scientists and governments are investigating alternative energy sources. In recent decades, there has been an increase in interest in initiatives involving the collection of clean, limitless energy. This paper focuses on two renewable energy harvesting combination technologies: mechanical vibration utilizing piezoelectric technology and thermal sources utilizing thermoelectric technology. Existing scientific literature proposes various techniques for producing and modeling each system individually. This study proposes a novel piezo-thermoelectric pavement model with piezo-thermoelectric coupling. Due to the lack of typical experimentation in the scientific literature, a new laboratory experimental prototype proposes to reproduce artificially and simultaneously heat harvesting on the artificial road surface and mechanical vibration caused by passing vehicles. Testing the laboratory-developed prototype has determined the efficacy of the piezo-thermoelectric coupling electronic model. This study demonstrated that a hybrid piezo-thermoelectric system is more suitable for road pavement applications than a piezo-thermoelectric coupling system. A hybrid combination system can continue to produce energy even if one of the energy sources is unavailable or malfunctioning, whereas a coupling combination system cannot. In laboratory testing, the combined piezo-thermoelectric harvester proposed could generate up to 1.75 μW without optimizing the materials or power generation. This innovative study demonstrates the feasibility and applicability of combining thermoelectric and piezoelectric technology to harvest energy from road surfaces.

Energy harvesting system using broadband textile antennas

Taking advantage of the benefits provided by the energy harvesting from ambient radio frequency sources, a multiband receiver is designed and manufactured using broadband antennas constructed with textile materials to be adapted into a Tshirt. The antennas connected to the rectifier allow to capture energy from the environment from four mobile bands: 1700, 1800, 1900 and 2100 MHz, and from the 2400 MHz WiFi band.

The Internet of Batteryless Things

Batteryless, energy-harvesting systems could reshape the Internet of Things into a more sustainable societal infrastructure.

Performance analysis of electromagnetic vibration energy harvester under square excitation

Harvesting energy from surrounding vibrations is an effective method for powering various low-power electronic devices. The energy output performance of vibration energy harvesters under some special excitations remains to be investigated. In this paper, a vibration energy harvester (VEH) system based on a rack and pinion mechanism and a bevel gear set is proposed, and a detailed electromechanical coupling modeling of the system under general excitation and square wave excitation is carried out. The energy output characteristics of the proposed system under square wave excitation are explored through simulation and experiment. When the energy output is the target, the priority of adjusting the constituent parameters in the equivalent mass parameter, equivalent damping parameter and equivalent stiffness parameter of the system can be obtained based on the simulation results. The experimental results under periodic square wave excitation force show that the maximum output power of the proposed system is 2.7 W at an amplitude of 4 kN and a frequency of 3 Hz. This is a 55 % increase in the maximum power compared to the sinusoidal excitation under the same conditions. It is demonstrated that the proposed system has great potential to power various low-power electronic devices.

Wearable All-Fabric Hybrid Energy Harvester to Simultaneously Harvest Radiofrequency and Triboelectric Energy.

Distributed micro-energy harvesting devices offer the flexibility, sustainability, and multi-scenario applicability that will be critical to wearable electronic products in the Internet of Things. The radiofrequency and triboelectric (RF-TE) hybrid energy harvester (HEH) concept and prototype is presented for the first time, to simultaneously capture the energy from ambient electromagnetic waves and biological motions. The proposed hybrid energy harvesting system consists of a wearable rectenna, a triboelectric nanogenerator (TENG), and a power management circuit (PMC). Among them, the all-fabric rectenna exhibits good impedance matching characteristics in the ISM frequency. The flexible TENG unit can generate a maximum power density of 0.024µWcm-2. The designed multifunctional fabric-based PMC can considerably enhance the controllability of harvested hybrid energy. Additionally, a normalizable fabric circuit board quasi surface mount technology (FCB-SMT) is proposed to integrate all modules on the same fabric substrate in one step, making the entire system superior mechanical robustness. The proposed wearable fabric-based RF-TE hybrid energy harvester is capable of successfully driving consumer electronics (such as sensors, watches, etc.). It provides a new energy solution strategy for self-powered wearable electronic devices and is anticipated to encourage the efficient utilization of renewable energy.

A power prediction approach for a solar-powered aerial vehicle enhanced by stacked machine learning technique

This study aims to enhance the solar energy harvesting capabilities of Unmanned Aerial Vehicles (UAVs), with a focus on integrating solar power to improve overall energy harvesting systems. The proposed method combines two independent renewable systems to extract electricity from the environment. UAV wings equipped with solar panels capture solar energy, employing optimal power point tracking for increased efficiency. Simulation results utilize an ensemble machine learning algorithm, incorporating environmental variables and UAV data to predict solar power output. A comparative analysis involving various machine learning algorithms provides additional insights gleaned from the UAV dataset.

Low-Wind-Speed Galloping Wind Energy Harvester Based on a W-Shaped Bluff Body

Galloping-based piezoelectric energy harvesting systems are being used to supply renewable electricity for low-power wireless sensor network nodes. In this paper, a W-shaped bluff body is proposed as the core component of a piezoelectric wind energy harvester. Experiments and simulations have shown that the W-shaped bluff body can improve harvesting efficiency at low wind speeds. For the W-shaped structure, the finite element simulation results indicate that the structure can help improve the aerodynamic performance to obtain high aerodynamic force. The experimental results demonstrate that compared with the traditional bluff bodies, the piezoelectric wind energy harvester with the W-shaped bluff body (WEHW) can generate higher output voltages and has a lower cut-in speed. When the length L is 30 mm and the rear groove angle β is 30°, the W-shaped structure can induce the best harvesting performance. When an external load resistance of 820 KΩ is connected and the wind speed is 5 m/s, the WEHW generates an average output power of 0.28 mW.