Energy Harvesting Methods Research Articles

Throughput Maximization in Wireless Communication Systems Powered by Hybrid Energy Harvesting

Energy harvesting techniques have been increasingly employed in both consumer and industrial applications to provide clean energy supply. Among the many available energy harvesting techniques, ambient energy harvesting (AEH) is a promising one as it harvests free energy from the environment and, thus, is economically efficient. AEH techniques, however, heavily depend on the dynamic environment and are thus uncontrollable and unstable. More recently, the wireless power transfer (WPT) technique has attracted significant attentions due to its highly controllable feature when powering low-cost devices. Unfortunately, WPT faces strict regulatory limitations to provide high power density and requires charging infrastructures installed to perform effective wireless energy transfer. The pros and cons of the two techniques motivate this work to design a hybrid energy harvesting method by charging a device using a combination of AEH and WPT to maximize the throughput of a wireless system. Specifically, this work first proposes an optimal offline charging scheme to maximize the point-to-point data throughput of a wireless system by fully utilizing the ambient energy and providing extra power supply through WPT to determine the transmission rates. An online heuristic algorithm is further proposed to improve the computational efficiency for practical scenarios when the system has the estimation of future AEH patterns. Our experimental results show that the proposed approaches are effective in maximizing the data throughput when compared to the state of the art.

Energy Harvesting Methods for Transmission Lines: A Comprehensive Review

Humanity faces important challenges concerning the optimal use, security, and availability of energy systems, particularly electrical power systems and transmission lines. In this context, data-driven predictive maintenance plans make it possible to increase the safety, stability, reliability, and availability of electrical power systems. In contrast, strategies such as dynamic line rating (DLR) make it possible to optimize the use of power lines. However, these approaches require developing monitoring plans based on acquiring electrical data in real-time using different types of wireless sensors placed in strategic locations. Due to the specific conditions of the transmission lines, e.g., high electric and magnetic fields, this a challenging problem, aggravated by the harsh outdoor environments where power lines are built. Such sensors must also incorporate an energy harvesting (EH) unit that supplies the necessary electronics. Therefore, the EH unit plays a key role, so when designing such electronic systems, care must be taken to select the most suitable EH technology, which is currently evolving rapidly. This work reviews and analyzes the state-of-the-art technology for EH focused on transmission lines, as it is an area with enormous potential for expansion. In addition to recent advances, it also discusses the research needs and challenges that need to be addressed. Despite the importance of this topic, there is still much to investigate, as this area is still in its infancy. Although EH systems for transmission lines are reviewed, many other applications could potentially benefit from introducing wireless sensors with EH capabilities, such as power transformers, distribution switches, or low- and medium-voltage power lines, among others.

Piezoelectric vibration energy harvester: Operating mode, excitation type and dynamics

Nowadays, with the rapid development of the intelligent era and the concept of Internet of Things being proposed, more and more sensors will play a more important role. Providing a sustainable power source for sensors has become the focus of current research in microsystem power generation. The harvesting of widely available vibrational energy from the environment for use as an alternative power source for sensors is of great significance in efficient energy utilization. Researchers have been working on developing efficient energy harvesters for broadband and efficient energy harvesting. Nonlinear energy harvesting holds more significant promise. In this paper, we summarized and reviewed the research progress of three different harvesting methods from the perspective of varying energy harvesting methods. We also listed the operation of various harvesters under different excitation types. At the same time, nonlinear energy harvesters with different structural characteristics are reviewed, the benefits of nonlinearity on energy harvesting are effectively collected, and the practical applications are summarized. Finally, current methods and mechanisms to improve the collection efficiency of energy harvesters are described and summarized. Briefly, this review introduces the research development of existing energy harvesting technologies, summarizes the technically difficult problems faced by piezoelectric energy harvesting technologies, and provides an outlook for future research and development trends of piezoelectric vibration energy harvesting technologies.

Novel Structure for Electromagnetic Micro-Power Harvester

Energy harvester could supply electronic devices such as implantable biomedical systems. Among the different methods of energy harvesting, the mechanical approach with the electromagnetic transduction method converts mechanical vibrations into output electrical power. In this research, an electromagnetic micro-generator is designed. The proposed device consists of a spring and a planar coil, designed using the Micro-electromechanical Systems (MEMS) technology, and also, a magnet and magnetic core. Different configurations are proposed to optimize the output power of the micro-generator. An innovative structure for the magnetic core is used to maximize the output power. The results show that the output power is increased up to 1.0344 μW and the power density is 2.94 μW/cm3. The attained output power is higher than that reported in the literature. The proposed energy harvester is a suitable replacement for limited lifetime supplies.

Sub-watt power triboelectric generator via polarization switching charge carrier

Triboelectric nanogenerator (TENGs) is one of the promising energy harvesting methods, and is expected to serve as primary power source. Nevertheless, previous TENGs were only able to generate low-current outputs. Even when energy management systems (EMSs) are used for TENGs, electrical losses occurred owing to complicated EMS circuits. Accordingly, high-mechanical inputs were still necessary to match power levels for existing electronics. Therefore, film capacitor-based charge-carrier TENGs (FCC-TENGs) are fabricated herein. These can be easily utilized for various circuits owing to their ultrahigh output with low input. As film capacitor-covered charge-carrier cylinders are rolling, FCC-TENGs can produce high voltage and current outputs of about 5000 V and 10 A, respectively, and can effectively reduce friction and wear. By loading external load, the root mean square power of FCC-TENG is measured up to 720 mW. Given the generated outputs, FCC-TENG can be used as primary power source for several power supply circuits that can turn on 12 commercial 5 W light-emitting diodes, power electric device, and charge lithium-ion battery.

A Review on Rail Defect Detection Systems Based on Wireless Sensors.

Small defects on the rails develop fast under the continuous load of passing trains, and this may lead to train derailment and other disasters. In recent years, many types of wireless sensor systems have been developed for rail defect detection. However, there has been a lack of comprehensive reviews on the working principles, functions, and trade-offs of these wireless sensor systems. Therefore, we provide in this paper a systematic review of recent studies on wireless sensor-based rail defect detection systems from three different perspectives: sensing principles, wireless networks, and power supply. We analyzed and compared six sensing methods to discuss their detection accuracy, detectable types of defects, and their detection efficiency. For wireless networks, we analyzed and compared their application scenarios, the advantages and disadvantages of different network topologies, and the capabilities of different transmission media. From the perspective of power supply, we analyzed and compared different power supply modules in terms of installation and energy harvesting methods, and the amount of energy they can supply. Finally, we offered three suggestions that may inspire the future development of wireless sensor-based rail defect detection systems.

Harvesting Wind Energy Based on Triboelectric Nanogenerators

The utilization of various distributed energy is becoming a prominent research topic due to the rapid development of the Internet of Things and wireless condition monitoring systems. Among the various distributed energy sources, wind energy has the advantages of being widely distributed, renewable and pollution-free, and is a very promising mechanical energy for power supply. Traditional wind energy harvesting methods based on electromagnetic and piezoelectric effects have issues with complex structure, large size, severe mechanical structures, and high installation costs. The low frequency and irregular nature of ambient mechanical energy makes these methods generally inefficient and inevitably hinders the further exploitation of wind energy. The triboelectric nanogenerators (TENGs) based on frictional charging and electrostatic effects can also be used for wind power generation and are increasingly favored by researchers as TENGs are easier to be miniaturized and assembled, and can realize large-scale manufacturing in comparison. This paper reviews the research on TENGs for wind energy utilization in terms of structural design, material selection and potential applications. In addition, the potential difficulties and possible developments in this field are summarized and discussed.

Optimal energy-harvesting design for AF and DF two-way relay beamforming in 6G

Energy consumption is an important point which is crucial for green communications in 6G era, especially for those networks with limited life span or affected by dangerous environments where batteries are inconvenient to be changed. Therefore, energy harvesting (EH) has become a very attractive research field in recent years. In this paper, a new type of two-way EH relay beamforming system with two transceivers and many single-antenna relays is designed. All the transmit power of relay nodes is not restricted by the total quota or the personal quota and can be obtained entirely by energy harvesting. We use power splitting (PS) method for EH. We first establish a two-way system model for the amplify-and-forward and decode-and-forward relaying and then analyze the sum rate, and the gradient descent algorithm is used to solve the nonlinear joint PS factor optimization problem. Finally, the results of our analysis are verified by simulation, and they show that our method can not only optimize the PS factor efficiently, but also the model can improve the performance of the system.

Blockchain-Based Incentive Energy-Knowledge Trading in IoT: Joint Power Transfer and AI Design

Recently, edge artificial intelligence techniques (e.g., federated edge learning) are emerged to unleash the potential of big data from Internet of Things (IoT). By learning knowledge on local devices, data privacy preserving and Quality of Service (QoS) are guaranteed. Nevertheless, the dilemma between the limited on-device battery capacities and the high energy demands in learning is not resolved. When the on-device battery is exhausted, the edge learning process will have to be interrupted. In this article, we propose a novel wirelessly powered edge intelligence (WPEG) framework, which aims to achieve a stable, robust, and sustainable edge intelligence by energy harvesting (EH) methods. First, we build a permissioned edge blockchain to secure the peer-to-peer (P2P) energy and knowledge sharing in our framework. To maximize edge intelligence efficiency, we then investigate the wirelessly powered multiagent edge learning model and design the optimal edge learning strategy. Moreover, by constructing a two-stage Stackelberg game, the underlying energy-knowledge trading incentive mechanisms are also proposed with the optimal economic incentives and power transmission strategies. Finally, simulation results show that our incentive strategies could optimize the utilities of both parties compared with classic schemes, and our optimal learning design could realize the optimal learning efficiency.

Synthesis and characterization of green-functionalized graphene nanofluids as an enhanced working fluid in heat transfer applications

Energy crisis is one of the major concerns that requires significant attention around the world. An access to reliable, sustainable, and affordable energy will not be attractive if the safety of human and environmental is neglected. Hence, the advancement of energy harvesting method is expected not to be just efficient, but also clean, safe, and environmental-friendly. In this research work, synthesis, and characterization of a green-based functionalized graphene nanofluids is presented. Clove extract was prepared and functionalized on the graphene nanoplatelets (GNP) using apple cider vinegar, followed by dispersion in distilled water to produce clove with apple cider vinegar functionalized graphene (clove+ACV GNP) nanofluids at 0.1 wt.% concentration. Characterization of the clove+ACV GNP nanofluids was carried out using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) to examine the successfulness of the synthesis and functionalization, while the thermal conductivity was determined using KD2 Pro Thermal Properties Analyzer. The covalent bonds shown in the FTIR spectrum, and the morphological structure from the SEM images have indicated that the synthesis and functionalization of clove+ACV GNP have been successfully carried out. As for the thermal conductivity, 0.1 wt.% of clove+ACV GNP nanofluids have shown up to 24.4% enhancement when compared with distilled water, 3.9% enhancement when compared to clove-functionalized GNP at the same concentration, and up to 6.8% when compared with conventional GNP nanofluids. These findings have given a preliminary insight that this safe, non-toxic- clove+ACV functionalized graphene nanofluids is a promising alternative to the conventional, toxic- nanofluids as an enhanced and effective working fluid in heat transfer applications.

Enhanced Photoelectrochemical Water-Splitting through Application of Layer by Layer (LBL) and Hydrothermal (HT) Methods in TiO2 and α-Fe2O3 Hierarchical Structures

Improving solar energy conversion efficiency and reducing energy loss have become critical issues in recent decades. Photoelectrochemical (PEC) water splitting provides an ideal method for solar energy harvesting and is a key factor in decreasing the use of fossil fuels. Thus, it is extremely important to identify cost-effective, highly active, and robust semiconducting photoelectrodes that can reduce the overpotential reaction and increase electrocatalytic efficiency. However, for overall water splitting, it is challenging to identify suitable photocatalysts with efficient band structures and suitable charge separation for electron-hole pairs. Water splitting is conventionally performed using independent layer-by-layer (LBL) or hydrothermal (HT) techniques. However, this research aims to produce a photoanode by applying both HT and LBL methods in sequence to reduce energy loss during the electron transfer process between the two photosystems. In this study, a TiO2 layer was deposited onto fluorine tin oxide (FTO) glass using the LBL method (TiO2/FTO). Subsequently, hematite (α-Fe2O3) thin films that were synthesized using the HT method were deposited onto TiO2/FTO glasses (Fe2O3/TiO2/FTO). The as-prepared and newly-designed photoanode Fe2O3/TiO2/FTO demonstrates a significantly high photocatalytic activity of 7.68 mA/cm2.Thus, by combining the HT and LBL methods, excellent hydrogen production performance in regard to photocatalytic water splitting was achieved. Furthermore, this hierarchical structure provides good chemical stability and is an excellent candidate for large-scale applications.

High-power triboelectric nanogenerators by using in-situ carbon dispersion method for energy harvesting and self-powered wireless control

In the era of the Internet of Things (IoT), various wearable electronic devices and sensors are widely used in the production and life of society. Due to its energy conversion characteristics, the flexible triboelectric nanogenerator (TENG) can not only act as a sensor device, but also solve energy supply problems. Here, a high-performance TiO2/carbon (TC) nanostructures-based TENG is proposed for the first time. Unlike the carbon-based conductive materials introduced by blending, the carbon in this work is embedded in TiO2 in situ by a simple solvothermal and heat treatment method, which has excellent dispersibility and stability. After introducing TC hybrid particles into PDMS, the electron affinity, dielectric constant, and surface roughness of the composite film have been significantly improved, which makes the TC-TENG exhibit an excellent power density (75.2 W/m2). In applications, the TC-PDMS composites TENGs can effectively harvest energy from human motions, and power electronic devices (LED lights, calculators and thermo-hygrometers). Importantly, a 6-bit array (2 ×3) digital touch board based on the TC-TENG is constructed for self-powered wireless control, which can control electronics products up to 10 m away. Our work gives a compelling way for the energy harvest and self-powered wireless control of electronic devices.

Circuit Techniques for High Efficiency Piezoelectric Energy Harvesting.

This brief presents a tutorial on multifaceted techniques for high efficiency piezoelectric energy harvesting. For the purpose of helping design piezoelectric energy harvesting system according to different application scenarios, we summarize and discuss the recent design trends and challenges. We divide the design focus into the following three categories, namely, (1) AC-DC rectifiers, (2) CP compensation circuits, (3) maximum power point tracking (MPPT) circuits. The features, problems encountered, and suitable systems of various AC-DC rectifier topologies are introduced and compared. The important role of non-linear methods for piezoelectric energy harvesting is illustrated from the perspective of impedance matching. Energy extraction techniques and voltage flipping techniques based on inductors, capacitors, and hybrid structures are analyzed. MPPT techniques with different features and targets are discussed.

Recent Advances in Solar Energy Harvesting by Improving Efficiency and Storage

For confronting the majority of today’s mankind needles, this paper considers some under-developed and current methods or techniques for advancing solar (sunlight) energy harvesting. Usually, modern energy or power systems presume continuous accessibility of energy, but the energy of the sun or sunlight isn’t available or accessible at night time. So, storage of energy nowadays is an imperative concern. Moreover, the usage of current solar power is not so cheap it causes high production costs. Therefore, there is a need to introduce substantiate solar energy harvesting methods to improve efficiency and reduce costs. Therefore, this research highlighted that storage of solar energy can surely be increased by using flywheels or superconducting magnets, mimic. To uplift the storage of solar energy at night time antennas can be used. Moreover, solar energy efficiency can be surely increased by using gold nano-particles, changing solar panels connects ways.

Power Supply Based on Inductive Harvesting From Structural Currents

Monitoring infrastructure offers functional optimization, lower maintenance cost, security, stability, and data analysis benefits. Sensor nodes require some level of energy autonomy for reliable and cost-effective operation, and energy-harvesting methods have been developed in the last two decades for this purpose. Here, a power supply that collects, stores, and delivers regulated power from the stray magnetic field of current-carrying structures is presented. In cm-scale structures the skin effect concentrates current at edges at frequencies even below 1 kHz. A coil-core inductive transducer is designed. A flux-funneling soft magnetic core shape is used, multiplying power density by the square of funneling ratio. A power management circuit combining reactance cancelation, voltage doubling, rectification, supercapacitor storage, and switched inductor voltage boosting and regulation is introduced. The power supply is characterized in house and on a full-size industrial setup, demonstrating a power reception density of 0.36, 0.54, and 0.73 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> from a 25-A root-mean-square structural current at 360, 500, and 800 Hz, respectively, corresponding to the frequency range of aircraft currents. The regulated output is tested under various loads and cold starting is demonstrated. The introduced method may enable power autonomy to wireless sensors deployed in current-carrying infrastructure.

A Multi-Modal Energy Harvesting Device for Multi-Directional and Low-Frequency Wave Energy

As a kind of sustainable energy source, ocean wave energy has always attracted attention. Because of the characteristics of multi-directions and low-bandwidth, the harvesting of wave energy has always been difficult. To harvest broadband wave energy in multiple directions and improve power generation efficiency, we present a multi-modal energy harvesting device by using a cross beam structure. In this device, the efficient harvesting of multi-frequency vibration energy in multiple directions has been achieved by using the multi-modal characteristics of the structure and the high power generation efficiency of the electric device based on liquid metal. Contrast experiments in multiple directions show that the device not only has the capability of multi-directional energy harvesting but also can work in the sweep range of the full band. Under horizontal excitation, compared with traditional single cantilever structure, the peak power density increased to 2227% and the working frequency band increased to 6.25 times. The experimental results show that the device significantly improves the efficiency of low-bandwidth multi-directional energy harvesting, providing a new method for vibration energy harvesting.

Reverse Electrowetting-on-Dielectric Energy Harvesting Using 3-D Printed Flexible Electrodes for Self-Powered Wearable Sensors

Reverse electrowetting-on-dielectric (REWOD) presents a unique low-frequency motion energy harvesting method to self-power wearable sensors for human health monitoring in real-time. However, previous studies in REWOD energy harvesting have mainly focused on enhancing power density using rigid electrodes, which due to their rigidity, are not ideal to be implemented as wearable energy harvesting or motion sensing applications from human motion activities. To be considered as the next generation self-powered wearable sensors, self-powered wearable sensors should operate continuously and sustainably in any kind of electrode bending motion and without an external power source. Herein, we demonstrate ac current generation by repeatedly modulating a liquid droplet of microliter volume on an elastomer-based three-dimensional printed flexible electrode without any external bias source. Flexible electrodes were fabricated by deposition of ∼200 nm of titanium (Ti) and an additional ∼200 nm of aluminum oxide (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) along with ∼50 nm of chromium (Cr) as an interlayer between the metal and the dielectric layers, and all of these on a flexible polydimethylsiloxane substrate. Using a 50 μL electrolyte droplet and 2.5 mm of electrode displacement at a low-frequency motion of 1–2 Hz, a maximum peak-to-peak ac current of ∼340 nA was measured. Although significant progress has yet to be made toward implementing REWOD energy harvesting as a reliable source of power for wearable self-powered systems, this letter signifies the proof-of-concept in implementing flexible electrodes in REWOD energy harvesting.

The interplay of active energy harvesting and wastewater organic loading regulates fermentation products and microbiomes in microbial fuel cells

Fruit juice wastewater (FJW) contains high strength and acidic organics that are difficult to remove. We developed microbial fuel cells (MFCs) to treat FJW and employed new energy harvesting methods to investigate how different operation conditions influence system performance and microbial community assembly. Specifically, we found both energy harvesting regime and organic loading affected current production, organic matter decomposition, product distribution, and microbial community. The power output under maximum power harvesting (MFC-MPP) condition showed the most stable output of 300 mW/m2 under different organic loadings. The MFC reactors maintained good organic removal (82.10–94.65%) at low loading of 1500–3000 mg/L, but the removal decreased with high loadings (7500–15,000 mg/L), presumably due to insufficient retention time, acid accumulation, and reduced degradability. Accordingly, higher VFA concentrations were observed in high loading reactors with the dominant products, formic acid and acetic acid. Electrofermentation coefficients (0.02–23.85%) of MFCs suggested that microaerobic electrofermentation (MEF) occurred in all reactors. MFCs under active harvesting demonstrated lower community diversity of anode biofilms at high organic loadings. The majority of dominant populations in the anode biofilm was affiliated with Lactococcus, Veillonella, and Bacteroides. This work demonstrates active energy harvesting and organic loading had interplay effects on system performance and microbiome, and system operation should consider such impacts to improve performance. AEH also provides a new alternative to a poised potential strategy for electrofermentation controlling.

Enhanced Electricity Generation from Graphene Microfluidic Channels for Self-Powered Flexible Sensors.

As a novel energy harvesting method, generating electricity from the interaction of liquid-solid interface has attracted growing interest. Although several functional materials have been carried out to improve the performance of the flow-induced hydrovoltaic generators, there are few reports on influencing the droplet flow behavior to excavate its electricity generation by governing the device structure. Here, the output performance of the graphene microfluidic channel (GMC) structure is ∼13 times higher than that of the flat-open space graphene morphology. The strong slip flow and high surface charge density near the graphene-droplet interface originate from the GMC structure, which produces an effective liquid-solid interaction and rapid relative movement of the droplet. Additionally, based on the GMC structure a self-powered pressure sensor is designed. The droplet motion is regulated by external forces to generate specific voltages, which provide a new approach for the development of wearable self-powered electronics.

An Energy Harvester Coupled with a Triboelectric Mechanism and Electrostatic Mechanism for Biomechanical Energy Harvesting.

Energy-harvesting devices based on a single energy conversion mechanism generally have a low output and low conversion efficiency. To solve this problem, an energy harvester coupled with a triboelectric mechanism and electrostatic mechanism for biomechanical energy harvesting is presented. The output performances of the device coupled with a triboelectric mechanism and electrostatic mechanism were systematically studied through principle analysis, simulation, and experimental demonstration. Experiments showed that the output performance of the device was greatly improved by coupling the electrostatic induction mechanisms, and a sustainable and enhanced peak power of approximately 289 μW was produced when the external impedance was 100 MΩ, which gave over a 46-fold enhancement to the conventional single triboelectric conversion mechanism. Moreover, it showed higher resolution for motion states compared with the conventional triboelectric nanogenerator, and can precisely and constantly monitor and distinguish various motion states, including stepping, walking, running, and jumping. Furthermore, it can charge a capacitor of 10 μF to 3 V within 2 min and light up 16 LEDs. On this basis, a self-powered access control system, based on gait recognition, was successfully demonstrated. This work proposes a novel and cost-effective method for biomechanical energy harvesting, which provides a more convenient choice for human motion status monitoring and can be widely used in personnel identification systems.