High performance metamaterial device with enhanced electromagnetic energy harvesting efficiency

Energy harvesting devices which convert low frequency mechanical energy sources such as human motions and ocean waves into electricity are attractive for powering portable devices and for green‐energy generation. To date the state‐of‐the‐art mechanical energy harvesting devices can only work efficiently at high vibration frequencies. Here, a biocompatible and flexible mechanical energy harvesting device is reported utilizing ionic diode as the transducer. This device utilizes the redistribution of cations and anions at the two hydrogel electrodes under stress to convert mechanical energy to electricity. It is shown that the device can be operated at low frequencies with high output current, e.g., 13.5 µA cm−2, owing to the high ion concentration and unique working mechanism of the device. Moreover, the output current density and power density can be improved further by employing a multilayer configuration. By stacking five units with parallel structure, the hydrogel diode device can generate an output current of 64.3 µA cm−2 and power density of 0.48 µW cm−2. Considering the very high electric energy density of ionic devices, the hydrogel energy harvesting device demonstrated herein paves a way for efficient mechanical energy harvesting from many common low frequency sources.

Efficiently harvesting the inherent kinetic energy carried by raindrops upon impact offers considerable potential for powering microdevices. However, the conversion efficiency of the raindrop energy is low. In this paper, we present a piezoelectric energy harvesting device with a superhydrophobic and low adhesive surface for significantly improving the raindrop energy conversion efficiency. The piezoelectric energy harvesting device was prepared using a macro fiber composite (MFC) with low operating frequency, high sensitivity, and a large electromechanical coupling coefficient as a functional element. The superhydrophobic surface allowed raindrops to rebound. At the same time, the raindrops can leave the surface of the device quickly after the end of their action so as to reduce the loss of kinetic energy generated by the collision of raindrops with solid surfaces. Compared to the untreated hydrophilic device, the energy conversion efficiency of the superhydrophobic piezoelectric energy harvesting device increased 172%. Under different test conditions, the device achieved a maximum peak power density of 338 W/m3. This approach provides a promising solution for efficient raindrop energy harvesting.

A metamaterial-based energy harvesting structure for harvesting 0.90 GHz, 1.80 GHz, 2.60 GHz GSM bands and a 5.80 GHz Wi-Fi frequency band is numerically and experimentally demonstrated. The metamaterial unit cell consists of four nested split-ring resonators (SRRs) interconnected on their split parts. Three resistors are used to harvest electromagnetic waves, which are sent to the structure with the electric field vector polarized in parallel to the gap of the SRRs. Under normal excitation, electromagnetic energy harvesting efficiencies are found to be 85.7%, 82.0%, 80.4% and 69.8% at 0.90 GHz, 1.80 GHz, 2.60 GHz and 5.80 GHz, respectively, by numerical analyses. Surface current distributions are utilized to gain insight into the relation between the harvesting frequencies and the structure. The effect of incidence angle upon harvesting efficiencies shows that the increase of absolute angle of incidence has different consequences for each harvesting band. The harvesting efficiency is increased to be as high as approximately 90% at 2.60 GHz and 5.80 GHz when the incidence angle is increased to 30°. The metamaterial sample is fabricated by conventional photolithography and the measured results in absorption performance are found to be in reasonable agreement with the numerical results. Moreover, it is demonstrated that the proposed metamaterial harvester structure has flexibility in terms of tailoring the harvesting frequencies and multi-band harvesting with more than four bands.

Renewable energy harvesting schemes in wireless sensor networks: A Survey

Halide double perovskite-based efficient mechanical energy harvester and storage devices for self-charging power unit

In today’s era of increasing energy constraints, harnessing the power of electromagnetic waves and converting them into directly usable energy has great potential in the field of renewable energy. This paper presents a highly efficient electromagnetic energy harvester with wide operation angles based on metasurface. The metasurface unit comprises four rotated copper rings plated on a Rogers RT5880 substrate. This unique design incorporates a 3.6 kΩ resistor within each of the four-cornered rotating metal rings, effectively emulating the input impedance circuit of a rectifier. Simulation results reveal that the metasurface achieves a remarkable electromagnetic wave harvesting efficiency of up to 92.3% at a frequency of 5.85 GHz. Additionally, it exhibits polarization insensitivity, enhancing its versatility and suitability for wide incident angles, which augments its practicality in various environments. The proposed metasurface energy harvester represents a significant advancement in electromagnetic energy collection technology, offering an efficient and reliable energy harvesting solution that contributes to addressing energy shortages and is applicable across multiple scenarios.

We developed a simple and efficient micro-electromagnetic energy harvester based on micro-electro-mechanical systems technology. For processes of electromagnetic vibration energy harvesters in the presence of the magnet, the compatibility with the micro-electro-mechanical systems processing is not good. Therefore, we have adopted a method of micro-assembly production energy harvester. The energy harvester mainly consists of a resonator chip processed by micro-electro-mechanical systems and a winding coil. The total volume of the energy harvesters is 0.95 cm3. Test results show that the energy harvester generated a maximum load power of 116.64 µW across 400 Ω load at 291.4 Hz for an acceleration of 0.5 g ( g = 9.8 m/s2) after the optimization of the parameters.

The technology of triboelectric nanogenerators (TENGs) has made great progress as a promising approach to generating electricity from ambient vibration energy. However, finding a way to generate enough electrical output efficiently from vibrations with a broadband of amplitudes is crucial when the relatively low current output of existing TENGs and the existence of natural vibrations with diverse amplitudes are considered. In this work, a freestanding and lightweight triboelectric nanogenerator with a capsule structure (namely, a capsule TENG) is demonstrated with an aim toward optional 3D integration and the efficient harvesting of energy from vibrations with a broadband of amplitudes. The capsule TENGs can be easily integrated to form 1D, 2D, and 3D structures to realize high electrical output. Under ideal conditions, the total output power of an integrated capsule-TENG pack can be approximately estimated as p × n2, where p is the peak output power per capsule TENG and n is the number of capsule TENGs. When capsule TENGs with hybrid structures, such as different lengths of the capsule tube and different numbers of paired electrodes, are assembled, energy can be more efficiently harvested from vibrations with a broadband of amplitudes. A total of three parameters (the active area-to-volume ratio, the power-to-volume ratio, and the power-to-weight ratio), which are important parameters for 3D-integrated TENGs, are proposed. The results of this research show that capsule TENGs are versatile devices that can potentially be used for the efficient harvesting of ambient vibration energy.

Implementation of energy harvesting technology can provide a sustainable, remote power source for soldiers by reducing the battery weight and allowing them to stay in the field for longer periods of time. Among multiple energy conversion principles, electromagnetic induction can scavenge energy from wasted kinematic and vibration energy found from human motion. Hip displacement during human gait acts as a base excitation for an energy harvesting backpack system. The placement of a permanent magnet in this vibration environment results in relative motion of the magnet to the coil of copper wire, which induces an electric current. This current can be saved to a battery or capacitor bank installed on the backpack to be used to power electronic devices. The purpose of this research is to construct a reliable simulation model for an electromagnetic vibration energy harvester and use it for a multi-variable optimization algorithm to identify an optimal coil and magnet layout for highest power output. Key components of the coupled equations of motion such as the magnetic flux density and coil inductance are obtained using ANSYS multi-physics software or by measuring them. These components are fed into a harvester simulation model (e.g. coupled field equations of motion for the backpack harvester) that generates the electrical power output. The developed simulation model is verified with a case study including an experimental test. Then the optimal design parameters in the simulation model (e.g., magnet layout, coil width, outer coil diameter, external load resistance) are identified for maximum power. Results from this study will pave the way for a more efficient energy harvesting backpack while providing better insight into the efficiency of magnet and coil layout for electromagnetic applications.

Acoustic metamaterials, capable of both sound insulation and energy harvesting, composed of Helmholtz resonators and built-in decorated membranes are proposed. It is theoretically and experimentally proved that the proposed metamaterial can obtain two sound insulation bands where the sound energy is also efficiently harvested at the same frequency simultaneously. The peak of the output power can reach up to 244 nW when the incident sound pressure is 1 Pa, which is about 14 times larger than structures composed of single membrane reported before with the same input. Moreover, considerable energy harvesting with average output power of about 20 nW can be achieved within wider frequency ranges (with bandwidth up to 90 Hz) by choosing proper parameters. Additionally, the hybrid resonance mechanism of the proposed metamaterials is explained well with an equivalent theoretical model. These novel properties of the proposed metamaterial can be applied in many potential applications in noise control and energy harvesting.

AlN piezoelectric thin films for energy harvesting and acoustic devices

Piezoaeroelastic energy harvesting based on an airfoil with double plunge degrees of freedom: Modeling and numerical analysis

The energy efficiency paradigm is a major bottleneck for the development of wireless sensor networks (WSNs) and Internet of Things (IoT) architectures and technologies. This edited book presents comprehensive coverage of energy harvesting sources and techniques that can be used for WSN and IoT systems

Insights and perspectives on graphene-PVDF based nanocomposite materials for harvesting mechanical energy

Energy harvesting from structure vibration, human motion or environmental source has been the focus of researchers in the past few decades. This paper proposes a novel design that is suitable to harvest energy from human motions such as dancing or physical exercise and use the device to engage young students in Science, Technology, Engineering and Math (STEM) fields and outreach activities. The energy harvester (EH) device was designed for a dominant human operational frequency range of 1–5 Hz and it can be wearable by human. We proposed to incorporate different genres of music coupled with energy harvesting technologies for motivation and energy generation. Students will learn both science and art together, since the energy harvesting requires understanding basic physical phenomena and the art enables various physical movements that imparts the largest motion transfer to the EH device. Therefore, the systems are coupled to each other. Young people follow music updates more than robotics or energy harvesting researches. Most popular videos on YouTube and VEVO are viewed more than 100 million times. Perhaps, integrating the energy harvesting research with music or physical exercise might enhance students’ engagement in science, and needs investigation. A multimodal energy harvester consisting of piezoelectric and electromagnetic subsystems, which can be wearable in the leg, is proposed in this study. Three piezoelectric cantilever beams having permanent magnets at the ends are connected to a base through a slip ring. Stationary electromagnetic coils are installed in the base and connected in series. Whenever the device is driven by any oscillation parallel to the base, the unbalanced rotor will rotate generating energy across the stationary coils in the base. In another case, if the device is driven by an oscillation perpendicular to the base, a stress will be induced within the cantilever beams generating energy across the piezoelectric materials.