Energy Scavenging Research Articles

Suspended-Load Backpacks to Reduce the Cost of Carrying Loads with Energy Scavenging Potential—Part 1: Pre-Compression Design

Backpack transportation is commonly used in daily life. Reducing the cost of the backpack on the human body is a widely researched subject. Suspended-load backpacks (SUSBs) based on forced vibration can effectively reduce the cost during movement. The intrinsic frequency of the SUSB is determined by the elastic components of the SUSB. Previous researchers used pulleys and rubber ropes as the elastic components. We propose a pre-compression design strategy based on pre-compression springs. Compared with previous studies, the use of pre-compression springs as elastic elements improves the reliability of the SUSB structure, avoids the inconvenience of nonlinearity and material aging, and adds the ability to flexibly adjust the sliding distance of the backpack. Moreover, previous studies utilized the relative motion between the carrying part and the backpack part to scavenge the vibration energy. We propose that the vibration energy can also be scavenged by the relative motion between the elastic components. A theoretical model is developed for the pre-compression SUSB. We experimentally confirm the performance of the pre-compression SUSB. This work provides new design ideas for SUSBs with reduced energy costs. In Part 2, we propose a bio-inspired pre-rotation design that has the advantage of occupying less space.

Nonlinear Electromagnetic Energy Harvester–Structure System under Seismic Excitation: Vibration Mitigation and Energy Scavenging

Nonlinear Electromagnetic Energy Harvester–Structure System under Seismic Excitation: Vibration Mitigation and Energy Scavenging

Optimization of MEMS-based Energy Scavengers and output prediction with machine learning and synthetic data approach

Micro-electromechanical systems (MEMS) based energy scavengers can serve as perpetual small-scale power sources. In this context, this work presents a novel approach for optimizing MEMS-based energy scavengers by predicting output power and natural frequency of operation through Synthetic Data and Machine Learning (ML) algorithms. For optimization, the work considers a bimorph cantilever-based energy scavenger, which consists of an elastic layer sandwiched between two piezoelectric layers. Various design parameters and their effect on the performance of the energy scavengers were evaluated through different ML models. The exploratory data analysis and preprocessing steps were carried out over the generated data, and subsequently, prediction of frequency and power was performed; 80% of the data was used for training purposes, and 20% of the data was used for testing purposes. Extreme Gradient Boost (XGBoost) was observed to be the best among the ML models for predicting frequency and power - with the R2 score of 97% and 86%, respectively. The optimized scavenger can generate an output power of 5.06 mW with an output voltage of 11.02 V. This approach can help the researchers by predicting the output power and resonant frequency, opening new research opportunities in the optimization of MEMS-based Energy Scavengers.

Ultra-high output hybrid nanogenerator for self-powered smart mariculture monitoring and warning system

Remote monitoring of distributed mariculture based on Internet of Things (IoT) has become an important part of smart marine agriculture, however, attaining stable and long-lasting power supply from conventional commercial batteries remains challenging, which significantly restricts the development of blue economic toward intelligent and diversified. Herein, a self-powered monitoring and warning system (SMWS) for smart mariculture based on a nodding duck structured multi-layer hybrid triboelectric-electromagnetic generator (MHTEG) is developed that endows improved electrical output performances and energy conversion efficiency. The structure of multi-electrode pairs is investigated with various ratios of nylon rod diameter to electrode width for optimizing the charge transfer efficiency of MHTEG. A peak output power density of 20.9 W/m3, ultra-high output energy of 39.6 mJ and excellent energy conversion efficiency of 22.61% can be achieved by the MHTEG with a high charge transfer efficiency of over 88%. Moreover, combining the MHTEG with an anti-theft and seawater sensor module, the remote SMWS is designed for monitoring and providing early-warning in marine farming. Such a design renders a practicable strategy and generic energy solution for efficient ocean wave energy scavenging and enabling distributed mariculture with intelligence.

Chicken skin based Milli Watt range biocompatible triboelectric nanogenerator for biomechanical energy harvesting

This work reports a high-performance, low-cost, biocompatible triboelectric nanogenerator (TENG) using chicken skin (CS). The device is suitable to power wearable devices, which is critical to adapt electronics in monitoring, predicting, and treating people. It also supports sustainability by providing a cost-effective way to reduce the poultry industry's waste. It has been shown here that CS-derived biowaste is an effective means of generating tribopositive material for TENGs. The CS contains amino acid functional groups based on (Glycine, Proline, and Hydroxyproline), which are essential to demonstrate the electron-donating ability of collagen. The skin was cut into 3 × 3 cm2 and used as the raw material for fabricating the TENG device with a stacking sequence of Al/Kapton/spacing/CS/Al. The chicken skin-based TENG (CS-TENG) is characterized at different frequencies (4–14 HZ) using a damping system. The CS-TENG produces an open-circuit voltage of 123 V, short-circuit current of 20 µA and 0.2 mW/cm2 of a power density at 20 MΩ. The biocompatible CS-TENG presents ultra-robust and stable endurance performance with more than 52,000 cycles. The CS-TENG is impressively capable of scavenging energy to light up to 55 commercial light-emitting diodes (LEDs), a calculator, and to measure the physiological motions of the human body. CS-TENG is a step toward sustainable, battery-less devices or augmented energy sources, especially when using traditional power sources, such as in wearable devices, remote locations, or mobile applications is not practical or cost-effective.

Hygromachines: Humidity-Powered Wheels, Seesaws, and Vehicles.

Hygroscopic soft actuators offer an attractive means to convert environmental energy to mechanical motions as they use water vapor, a ubiquitous substance in the atmosphere. To overcome the limits of existing hygroactuators, such as simplistic actuation mode, slow response, and low efficiency, here we present three kinds of humidity-powered soft machines adopting directionally electrospun hygroresponsive nanofibrous sheets. The wheels, seesaws, and vehicles developed in this work utilize spatial humidity gradient naturally established near moist surfaces such as human skin, so that they operate spontaneously, realizing energy scavenging or harvesting. We also constructed a theoretical framework to mechanically analyze their dynamics, which allowed us to optimize their design to obtain the highest motion speed physically possible.

Multiple textile triboelectric nanogenerators based on UV-protective, radiative cooling, and antibacterial composite yarns

In addition to energy scavenging and self-powered sensing, there is growing interest in expanding the capabilities of textile-based triboelectric nanogenerators (T-TENGs). In this study, we present a novel approach to developing T-TENGs with advanced features, such as antibacterial, ultraviolet (UV) protection, and radiative cooling performance. We use core − shell yarns consisting of conductive stainless steel wires (SS) as the electrode and anti-UV cotton yarns with antibacterial properties (UV/OM-CY) combined with polyethylene (PE) yarns that are tightly twined around the core SS fibers as the basic building blocks (PE/UV/OM-CY). The resulting fabric (PE/UV/OM-CF TENG), woven from these composite yarns, not only exhibits remarkable UV-protection capabilities with a UPF value of up to 328, but also demonstrates exceptional personal temperature management performance, with a surface temperature approximately 6.9 °C lower than that of cotton fabrics under intense direct sunlight. Moreover, the PE/UV/OM-CF TENG exhibits remarkable antibacterial activity against Escherichia coli and Staphylococcus aureus. Additionally, the fabricated PE/UV/OM-CF TENG displays excellent capability as a self-powered movement sensor, which could assist patients in modifying their exercise routines. Our multifunctional and consumer-centric design of T-TENG technology shows great potential for wearable electronics and could advance the development of artificial intelligence.

Low-cost environment-friendly energy scavenging system

The purpose of this work is to design an energy scavenging system. The system scavenges ambient energy from indoor Wi-Fi routers. It makes use of low cost, environment-friendly and widely available corrugated cardboard substrate. The circuit design is realized on metallic layers made of low-cost copper tape. A Villard rectifier is used to convert the RF energy into dc. The measured scavenged power of the system at the power density of 10 μW cm−2 is −15.76 dBm (26.5 μW). The measured conversion efficiency is 58.6%. The presented design has the lowest cost among other similar works.

Enhanced thermoelectric properties of bismuth telluride (Bi2Te3) and multiwall carbon nanotube (MWCNT) composites

Solid solutions based on bismuth telluride are the traditional thermoelectric materials that are commercially utilized in the industry close to room temperature applications, where energy scavenging is a big challenge due to low quality and energy density. However, their broader applications are still limited due to low efficiency. The focus of the present work is to enhance the energy conversion efficiency of Bi2Te3 by mixing one-dimensional (1D) multiwall carbon nanotubes (MWCNTs) via facile powder processing by synergistically utilizing the nanostructuring and quantum confinement effects. Thus, different vol% of MWCNTs ranging from 0.5, 1.0, 1.5, and 2 were uniformly dispersed in a fine powder of Bi2Te3 that was ball milled from course Bi2Te3 in an inert environment. The coarse Bi2Te3 and fine composite powders were consolidated in a spark plasma-sintering furnace at ∼400 °C under uniaxial pressure of ∼40 MPa. Thermoelectric properties of Bi2Te3-based MWCNTs composites were evaluated in the temperature range from ∼300 to ∼525 K. The electrical conductivity of 1.5 vol% MWCNT composite has significantly enhanced from pristine Bi2Te3. This increase indicates that electrical transport dominantly involves a percolating network of MWCNTs. The concomitant increase in the Seebeck coefficient of 1.5 vol% Bi2Te3 composite suggests the enhanced energy-dependent scattering of charge carriers. Consequently, a substantially improved power factor is observed for the composite. The thermal conductivity of all the composites decreases, and considerable reduction is achieved for 0.5 vol% due to enhanced phonon scattering through nanostructuring and uniform distribution of the nanotubes. Hence, the significant decrease in thermal conductivity with improved power factor leads to substantial improvement in the thermoelectric figure of merit of 1.5 vol% Bi2Te3 composite from pristine Bi2Te3.

Magnetic Bistability for a Wider Bandwidth in Vibro-Impact Triboelectric Energy Harvesters.

Mechanical energy from vibrations is widespread in the ambient environment. It may be harvested efficiently using triboelectric generators. Nevertheless, a harvester's effectiveness is restricted because of the limited bandwidth. To this end, this paper presents a comprehensive theoretical and experimental investigation of a variable frequency energy harvester, which integrates a vibro-impact triboelectric-based harvester and magnetic nonlinearity to increase the operation bandwidth and improve the efficiency of conventional triboelectric harvesters. A cantilever beam with a tip magnet was aligned with another fixed magnet at the same polarity to induce a nonlinear magnetic repulsive force. A triboelectric harvester was integrated into the system by utilizing the lower surface of the tip magnet to serve as the top electrode of the harvester, while the bottom electrode with an attached polydimethylsiloxane insulator was placed underneath. Numerical simulations were performed to examine the impact of the potential wells formed by the magnets. The structure's static and dynamic behaviors at varying excitation levels, separation distance, and surface charge density are all discussed. In order to develop a variable frequency system with a wide bandwidth, the system's natural frequency varies by changing the distance between the two magnets to reduce or magnify the magnetic force to achieve monostable or bistable oscillations. When the system is excited by vibrations, the beams vibrate, which causes an impact between the triboelectric layers. An alternating electrical signal is generated from a periodic contact-separation motion between the harvester's electrodes. Our theoretical findings were experimentally validated. The findings of this study have the potential to pave the way for the development of an effective energy harvester that is capable of scavenging energy from ambient vibrations across a broad range of excitation frequencies. The frequency bandwidth was found to increase by 120% at threshold distance compared to the conventional energy harvester. Nonlinear impact-driven triboelectric energy harvesters can effectively broaden the operational frequency bandwidth and enhance the harvested energy.

Flexible BaTiO3 Thin Film-Based Coupled Nanogenerator for Simultaneously Scavenging Light and Vibration Energies

Ferroelectric materials have a variety of properties, such as piezoelectricity, pyroelectricity, and the ferroelectric photovoltaic effect, which enable them to obtain electrical energy from various external stimuli. Here, we report a coupled nanogenerator based on flexible BTO ferroelectric films with a cantilevered beam structure. It combines the photovoltaic and flexoelectric effects in a ferroelectric materials-based coupled nanogenerator for simultaneously scavenging vibration energy and light energy, thus improving energy scavenging performance. As compared with the photovoltaic effect individually, simultaneous vibration and light illumination under a light intensity of 57 mW/cm2 at 405 nm can produce a photo-flexoelectric coupling current of 85 nA, where the current peak has been enhanced by 121%. Due to the photo-flexoelectric coupling effect, the device has outstanding charging performance, where a 4.7 μF capacitor can be charged to 60 mV in 150 s. These devices have potential applications in multi-energy scavenging and self-powered sensors.

A high performance lead-free flexible piezoelectric nanogenerator based on AlFeO3 nanorods interspersed in PDMS matrix for biomechanical energy scavenging to sustainably power electronics

Since lead-based piezoelectric nanogenerators (PENGs) possess serious health risks, environmental problems, proper disposal issues, and biocompatibility concerns, this work presents the fabrication of a flexible piezoelectric nanogenerator utilizing lead-free orthorhombic AlFeO3 nanorods for biomechanical energy scavenging to sustainably power electronics. Hydrothermal technique is used to synthesize the AlFeO3 nanorods and the PENG was fabricated on Indium tin oxide (ITO) coated Polyethylene terephthalate (PET) flexible film with AlFeO3 nanorods interspersed in polydimethylsiloxane (PDMS). transmission electron microscopy proved that the AlFeO3 nanoparticles are of nanorods shape. Through x-ray Diffraction, it is validated that AlFeO3 nanorods have orthorhombic phase and crystalline structure. A high piezoelectric charge coefficient (d 33 ) of 400 pm V−1 is obtained from the piezoelectric force microscopy of AlFeO3 nanorods. With optimized concentration of AlFeO3 in the polymer matrix, an open circuit voltage (V OC) of 30.5 V, current density (J C) of 0.7888 μA cm−2 and an instantaneous power density of 240.6 mW m−2 are obtained under the application of a force of 1.25 kgf. To investigate the nanogenerator’s practical utility, the PENG is used for lighting multiple LEDs, charging of a capacitor and as a pedometer via biomechanical energy harvesting. Hence, it can be employed for developing various self-powered wearable electronics such as flexible skin, artificial cutaneous sensors, etc.

Evolution of Micro-Nano Energy Harvesting Technology—Scavenging Energy from Diverse Sources towards Self-Sustained Micro/Nano Systems

Facing the energy consumption of a huge number of distributed wireless Internet of Things (IoT) sensor nodes, scavenging energy from the ambient environment to power these devices is considered to be a promising method. Moreover, abundant energy sources of various types are widely distributed in the surrounding environment, which can be converted into electrical energy by micro-nano energy harvesters based on different mechanisms. In this review paper, we briefly introduce the development of different energy harvesters according to the classification of target energy sources, including microscale and nanoscale energy harvesters for vibrational energy sources, microscale energy harvesters for non-vibrational energy sources, and micro-nano energy harvesters for hybrid energy sources. Furthermore, the current advances and future prospects of the applications of micro-nano energy harvesters in event-based IoT systems and self-sustained systems are discussed.

An introduction to triboelectric nanogenerators

Today, there is a continuous rise in the requirement for upgraded healthcare systems that are self-driven, dynamic and very low in maintenance. With a steep rise in the evolution of devices and their applications, such as sensors, there is an increment in the supply of sustainable energy without the replacement and recharging of the installed charge storage devices. Among the various energy scavengers, triboelectric nanogenerators (TENGs) have garnered huge attention as they have a high instantaneous output power and can be developed from a broad selection of available materials, like aluminium (Al) and copper (Cu) metal films, fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and green materials like cellulose-based materials. TENGs have a great ability to convert extracted mechanical energies into electrical energies very effectively due to the coupling effects of contact electrification and electrostatic induction. They have tremendous potential in a diverse range of applications, such as medical therapies that include biomedical applications, energy scavenging and active sensing. TENGs are devices made of self-energizing materials that are non-polluting, long-lasting and small sized. They can be developed through inexpensive fabrication processes and are environmentally friendly. In this paper, the mechanism by which the triboelectric nanogenerators perform their applications and how strategies are being developed to improve their performance have been discussed. We have also discussed the future research directions that are being undertaken to advance development in this field. So far, TENGs have mainly been used as mechanical and chemical stimuli to detect sensors and as an electrical source for electronic equipment and devices. Most of the studies found in the literature have reported that TENGs are primarily focused on optimization of systems and circuit designs or on the application of TENGs. A thorough review of the fundamentals of TENGs has been presented here.

Development of Highly Efficient Energy Harvester Based on Magnetic Field Emanating From a Household Power Line and Its Autonomous Interface Electronics

A magnetic energy harvester and its interface electronics are developed to operate a surface acoustic wave (SAW) oscillator sensor that requires at least 5–6 V dc (50–100 mW) to drive and transmit the measured sensor signals to the reader system wirelessly via antennas. The developed energy harvester system comprises a magnetic energy harvester with a coil wound around a magnetic core, an energy storage interface, and a power management interface. From a 220-V, 3-A household ac power line, a 12-V dc is harvested in the storage capacitor via a 5-min energy scavenging process to activate the SAW oscillator sensor. After 2 min of operation using the sensor system, the power management interface is completely shut down to recharge the storage capacitor and then restarted after sufficient charges are accumulated in the storage capacitor to reoperate the SAW oscillator sensor. This autonomous sequence is continuously repeated. The entire interface electronics is developed on a single printed circuit board (PCB) to reduce the energy loss by the board and to facilitate installation in the desired applications. A simulation is performed in COMSOL to determine the optimal energy harvester parameters and to predict the magnetic flux density that forms the induced current around the ferrite magnetic core based on the magnetic core shape. Experimental results show that the developed energy harvester system can harvest sufficient energy from the household power line in a short period to operate the complex RF SAW sensor and the sensor interface electronics. Furthermore, it can be used to operate the SAW oscillator sensor for the time required to obtain valid information to be transmitted wirelessly to the reader system.

A Highly Wearable Single-electrode Mode Triboelectric Nanogenerator Made of Flexible Polyvinylidene Fluoride Transparent Film for Muscular Motion Monitoring

The present study reports the design and fabrication of a single-electrode mode triboelectric nanogenerator (TENGs) which can overcome the drawbacks present in the conventional triboelectric nanogenerator which works on two electrodes and two dielectric layers. The proposed concept eliminates the dual electrodes thereby reducing the complexity of the device and the higher fabrication cost enabling the device to be used for extended applications. The fabricated TENG device uses Polyvinylidene fluoride (PVDF) as the active material that is capable to generate the electrical response upon contact with the human skin when the device was worn on the skin. The device generates the highest electrical output of ~ 50 V and a current of ~ 600 nA under a 1 Hz operating frequency. The device also shows good stability and durability by powering continuously for 300 s without any interruption in its electrical output response. The device shows its applicability in utilizing it powering low-power electronic devices, bio-mechanical energy scavenging upon actuated by hand and foot tapping, as well as demonstrated for the self-powered muscular monitoring system. The study greatly expands the opportunity of using TENGs for applications in the field of healthcare, bio-medical, and the Internet of Things (IoT).

Jamming-and-Relaying Strategy for Non-linear Energy Scavenging Networks

Jamming-and-Relaying Strategy for Non-linear Energy Scavenging Networks

Energy Harvesting Technologies and Devices from Vehicular Transit and Natural Sources on Roads for a Sustainable Transport: State-of-the-Art Analysis and Commercial Solutions

The roads we travel daily are exposed to several energy sources (mechanical load, solar radiation, heat, air movement, etc.), which can be exploited to make common systems and apparatus for roadways (i.e., lighting, video surveillance, and traffic monitoring systems) energetically autonomous. For decades, research groups have developed many technologies able to scavenge energy from the said sources related to roadways: electromagnetism, piezoelectric and triboelectric harvesters for the cars’ stress and vibrations, photovoltaic modules for sunlight, thermoelectric solutions and pyroelectric materials for heat and wind turbines optimized for low-speed winds, such as the ones produced by moving vehicles. Thus, this paper explores the existing technologies for scavenging energy from sources available on roadways, both natural and related to vehicular transit. At first, to contextualize them within the application scenario, the available energy sources and transduction mechanisms were identified and described, arguing the main requirements that must be considered for developing harvesters applicable on roadways. Afterward, an overview of energy harvesting solutions presented in the scientific literature to recover energy from roadways is introduced, classifying them according to the transduction method (i.e., piezoelectric, triboelectric, electromagnetic, photovoltaic, etc.) and proposed system architecture. Later, a survey of commercial systems available on the market for scavenging energy from roadways is introduced, focusing on their architecture, performance, and installation methods. Lastly, comparative analyses are offered for each device category (i.e., scientific works and commercial products), providing insights to identify the most promising solutions and technologies for developing future self-sustainable smart roads.

Cellulose Gel Mechanoreceptors – Principles, Applications and Prospects

AbstractIn order to effectively harness varieties of mechanical waves or vibrations for the purpose of monitoring and/or powering, developments in responsive materials and conversion technologies are taking place driven by the world's current and future demands. One of the most popular novelties of the last two decades is represented by hydrogel‐ or ionogel‐based flexible iontronics which constitute a wide family of innovative smart (self‐powered) mechanoreceptors relevant for various applications such as personal health care, identity and safety monitoring, intelligent human‐machine operation interfaces, underwater listening and communication, and so on. Cellulosic gels (CGs), as a promising green substitute for fossil fuel‐derived materials, are extensively studied due to the possibility to choose between different cellulose types and to formulate networks chemically or physically, according to the adaptability requirements for each target application. The aim of this review is to showcase the cellulose structural versatility and to provide a summary of the principles during the formulation of CGs used for mechanosensing and mechanical energy scavenging, as well as their practical applications. Such an outlook of current challenges and overall prospects will serve as a stimulus for research on CG‐based mechanoreceptors in the future.

Mylar Interlayer-Mediated Performance Enhancement of a Flexible Triboelectric Nanogenerator for Self-Powered Pressure Sensing Application

A triboelectric nanogenerator (TENG) is a green energy harvester that transforms mechanical energy from the surroundings and body movements into useful electrical energy by the combined effect of triboelectrification and electrostatic induction. Here, we have developed a flexible organic–inorganic film-based contact separation mode TENG with polyvinyl butyral (PVB) and indium oxide (IO) films as contact materials. A biaxially oriented polyethylene terephthalate (BoPET) film (known as “Mylar”) has been used as the charge transition-blocking interlayer between the PVB triboelectric layer and the electrode, which prevents the recombination of generated charges with the interfacial charges on the electrode and thereby enhances the electrical output performance. The fabricated flexible PVB-IO TENG having a contact area of 4 cm2 and a separation gap of 5 mm generates an output voltage and a short-circuit current density of ∼700 V and ∼1.52 mA/m2, respectively. An enhancement of ∼85-fold in the peak power density is obtained for the PVB-IO TENG with the BoPET layer at a load resistance of 200 MΩ in comparison with the one without the BoPET interlayer. The as-fabricated device was used for capacitor charging and powering electronic gadgets such as digital thermometers, calculators, and LEDs. Also, the developed PVB-IO TENG has been demonstrated for the mechanical energy scavenging from human motions such as finger tapping, palm tapping, finger bending, and elbow bending. Moreover, the PVB-IO TENG was structurally modified into a self-powered pressure sensor by reducing its contact area and separation gap, which exhibits an excellent sensitivity of ∼4.38 V/kPa in the pressure range from 0.5 to 16 kPa.