Superhydrophobic Piezoelectric Device for Efficient Raindrop Energy Harvesting

Inspired by shallow-water sloshing in a moving tank, a novel type of vibration-based piezoelectric energy harvesting device composed of a piezoelectric bimorph beam and an extension tank is proposed in this paper. The structure and working principle of the proposed device are provided. Then, the effects of different heights of water filling in the tank on the performances of the harvester are studied and analyzed. Experiments are set up to investigate the actual device performance by changing the base excitation frequency and load resistance for different water heights. The results show that by modulating the water height, the resonant frequency and bandwidth can be adjusted, which can enhance the energy harvesting performance of the device at different ambient vibration frequencies. This study provides some clues to improve the performance of the vibration-based energy harvesting devices.

Polymeric piezoelectric composites for energy harvesting applications are considered a significant research field which provides the convenience of mechanical flexibility, suitable voltage with sufficient power output, lower manufacturing cost, and rapid processing compared to ceramic‐based composites. This review focuses majorly on the basic theory and principles behind piezoelectric energy harvesting (PEH) devices, followed by specified materials used for the different devices. Different structural configurations associated with fabrication of PEH devices are discussed in detail along with their major advantages and drawbacks. Numerous classes of piezoelectric polymers such as polyvinylidene fluoride, polylactic acid, cellulose, polyamides, polyurea, polyurethanes, and their composites used for energy harvesting applications as a productive alternative of lead‐based piezo‐ceramics, are extensively addressed and explored. Additionally, current global and Indian scenarios associated with PEH devices, major challenges associated with them, and the future perspective of such devices are also reported in this review.

This review provides a detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferroelectrics. These properties are, in many cases, present in the same material, providing the intriguing prospect of a material that can harvest energy from multiple sources including vibration, thermal fluctuations and light. Piezoelectric materials are initially discussed in the context of harvesting mechanical energy from vibrations using inertial energy harvesting, which relies on the resistance of a mass to acceleration, and kinematic energy harvesting which directly couples the energy harvester to the relative movement of different parts of a source. Issues related to mode of operation, loss mechanisms and using non-linearity to enhance the operating frequency range are described along with the potential materials that could be employed for harvesting vibrations at elevated temperatures. In addition to inorganic piezoelectric materials, compliant piezoelectric materials are also discussed. Piezoelectric energy harvesting devices are complex multi-physics systems requiring advanced methodologies to maximise their performance. The research effort to develop optimisation methods for complex piezoelectric energy harvesters is then reviewed. The use of ferroelectric or multi-ferroic materials to convert light into chemical or electrical energy is then described in applications where the internal electric field can prevent electron–hole recombination or enhance chemical reactions at the ferroelectric surface. Finally, pyroelectric harvesting generates power from temperature fluctuations and this review covers the modes of pyroelectric harvesting such as simple resistive loading and Olsen cycles. Nano-scale pyroelectric systems and novel micro-electro-mechanical-systems designed to increase the operating frequency are discussed.

Effect of Nd-doping on 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3 ceramics: Enhanced electrical properties and piezoelectric energy harvesting capability

Water wave energy is a promising renewable energy source that may alleviate the rising concerns over current resource depletion, but it is rarely exploited due to the lack of efficient energy harvesting technologies. In this work, a hybrid system with a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) based on an optimized inner topological structure is reported to effectively harvest water wave energy. The TENG with etched polytetrafluoroethylene films and Cu electrodes utilizing the contact‐freestanding mode is designed into a cubic structure, in which the EMG is well hybridized. An integration of TENG and EMG achieves mutual compensation of their own merits, enabling the hybrid system to deliver satisfactory output over a broad range of operation frequency. The output performance of TENG with varied inner topological structures is experimentally and theoretically compared, and a concept is proposed to further clarify the energy conversion efficiency, which should be considered in designing energy harvesting devices. The influences of oscillation frequency, amplitude, and dielectric materials on the output performance of the hybrid system are comprehensively studied on different platforms. Furthermore, the optimum operation frequency ranges for TENG and EMG are concluded. The proposed hybrid nanogenerator renders an effective approach toward large‐scale blue energy harvesting over a broad frequency range.

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

When designing implantable biomedical MEMS devices, we must provide electric power source with long life and small size to drive the sensors and actuators work. Obviously, traditional battery is not a good choice because of its large size, limited lifetime and finite power storage. Living creatures all have non-electric energy sources, like mechanical energy from heart beat and pulse. Piezoelectric structure can convert mechanical energy to electric energy. In the same design condition, the more electric energy is generated, the better the piezoelectric structure design. This paper discusses the topology optimization method for the most efficient implantable piezoelectric energy harvesting device. Finally, a design example based on the proposed method is given and the result is discussed.

Metasurface energy harvesters (MEHs) lessen the dependence of wireless communication devices on batteries or other external power sources by capturing untapped electromagnetic energy in the surroundings. In this paper, we propose a multi-frequency and multi-mode microwave metasurface for efficient radio frequency (RF) and microwave energy harvesting. The MEH is comprised of a sub-wavelength resonant ring array, which can harvest RF energy in both Wi-Fi and 5 GHz bands. A feeding network is designed to integrate the TE and TM wave energy collected by the MEH into two separate networks that each gather AC energy and deliver them to the resistive loads. In terms of the simulation’s results, the efficiency of energy harvesting at frequencies of 2.4 GHz, 3.1 GHz, as well as 3.6 GHz is 91.3%, 88.9%, and 73.9%, specifically. We manufactured a 6 × 6 array sample and conducted experiments utilizing a microwave anechoic chamber. The simulation results and results from experiments were approximately identical. The proposed design has potential applications in various fields, such as efficient wireless energy harvesting systems, self-powered devices, which has a significant potential on the environment and the energy sector by reducing carbon emissions and reducing reliance on non-renewable energy sources.

This paper presents a novel approach for designing broadband piezoelectric harvesters by integrating multiple piezoelectric bimorphs (PBs) with different aspect ratios into a system. The effect of 2 connecting patterns among PBs, in series and in parallel, on improving energy harvesting performance is discussed. It is found for multifrequency spectra ambient vibrations: 1) the operating frequency band (OFB) of a harvesting structure can be widened by connecting multiple PBs with different aspect ratios in series; 2) the OFB of a harvesting structure can be shifted to the dominant frequency domain of the ambient vibrations by increasing or decreasing the number of PBs in parallel. Numerical results show that the OFB of the piezoelectric energy harvesting devices can be tailored by the connection patterns (i.e., in series and in parallel) among PBs.

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.

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.

A high performance metamaterial device for electromagnetic energy harvesting is presented. The unit cell of the metamaterial device consists of four identical omega ring resonators arranged in rotational symmetry, and each omega ring is loaded with a 50 Ω resistor that mimics the input impedance of a rectifier circuit. A proof-of-concept prototype is designed for operation at the frequency of 5.8 GHz. Here, the efficient energy harvesting is validated by the energy dissipated in each resistor. Based on the full absorption concept, the metamaterial device achieves a harvesting efficiency up to 93.1% under normal incidence. In addition, the energy harvester shows polarization independent and wide-angle incident frequency responses with good harvesting characteristics over the entire operating range. The surface current distribution is analyzed to gain an insight into the energy harvesting mechanism. Moreover, the harvester prototype is manufactured and measured, and the simulated and measured results are in good agreement. Due to the enhanced electromagnetic energy harvesting efficiency, the proposed device is a good candidate for microwave power transmission.

Three-dimensional (3D) printing technologies have unparalleled advantages in constructing piezoelectric devices with three-dimensional structures, which are conducive to improving the efficiency of energy harvesting. Among them, fused deposition modeling (FDM) is the most widely used thanks to its low cost and wide range of molding materials. However, as the best piezoelectric polymer, a high electroactive β-phase poly(vinylidene fluoride) (PVDF) piezoelectric device cannot be directly obtained by FDM printing because the β-crystal is unstable at the molten state. Herein, we develop for the first time ionic liquid (IL)-assisted FDM for direct printing of β-PVDF piezoelectric devices. An IL can induce and maintain β crystals during melt extrusion and FDM printing, ensuring that the β-crystal in the printed PVDF device is as high as 98.3%, which is the highest in 3D-printed PVDF as far as we know. Furthermore, the shearing force provided by the FDM facilitates the directional arrangement of the dipoles, resulting in the printed PVDF device having self-polarization characteristics without poling. Finally, the piezoelectric output voltage of the 3D-printed PVDF device is 4.7 times that of the flat PVDF device, and its area current density (17.5 nA cm-2) is more than that of the reported 3D-printed PVDF piezoelectric device in the literature by two orders of magnitude. The one-step 3D printing strategy proposed in this paper can realize the rapid preparation of complex-shaped and lightweight self-polarized β-PVDF-based piezoelectric devices for energy harvesting.

Energy harvesting in wireless sensor networks: A comprehensive review

In wind turbine tower (WTT) bolt health monitoring, traditional energy harvesting devices have low efficiency, insufficient energy conversion efficiency, high energy consumption of monitoring systems, and insufficient system integration and optimization. This paper proposed a new energy self-powered technology to achieve long-term and continuous health monitoring of WTT. It designed an efficient energy harvesting device that used natural energy such as wind turbine tower vibration and temperature change to achieve energy harvesting, optimized materials and structures, improved energy harvesting efficiency, and ensured a long-term stable supply of energy sources. The paper used an efficient energy conversion module to convert the collected mechanical energy and thermal energy into electrical energy, and uses high-capacity energy storage devices for storage, so that the system can operate stably without an external power supply. Energy self-power supply technology can be effectively integrated with the health monitoring system, and low-power sensors and wireless data transmission modules can be designed to reduce the system’s overall energy consumption and ensure the real-time collection and transmission of health monitoring data. Intelligent scheduling algorithms optimize energy usage strategies so that energy resources can be reasonably allocated, avoiding excessive consumption of limited energy by the system and realizing long-term stable operation of the WTT monitoring system. The experimental results show that the energy conversion rate of the designed energy harvesting device is 81.7% at a frequency of 100Hz and 79.4% at a high temperature of 100°C, showing obvious advantages in efficiency under vibration frequency and temperature changes. The power consumption of the wireless data transmission module of the self-powered system increases from 15 kW in 6 hours to 22 kW in 24 hours, and the power consumption of the energy management module increases from 12 kW to 18 kW. The power consumption remains low, which is suitable for long-term monitoring tasks.