Advancement in piezoelectric nanogenerators for acoustic energy harvesting

Hybrid Energy-Harvesting Systems Based on Triboelectric Nanogenerators

Enhancement of acoustic properties of carbon fibrous membrane (CFM) by in-situ crystallization of PZT nanogenerators (PENGs) inside the fibers for a low-frequency acoustic energy harvesting

Piezoelectric nanogenerators (PNGs) have recently received significant attention because of their great potential for harvesting electricity from wasted mechanical energy resources. In spite of many studies on piezoelectric energy harvesters, a comprehensive review that summarizes alternative types of piezoelectric materials is yet to be reported. This article categorizes piezoelectric materials into two types: piezoelectric perovskite and wurtzite micro‐/nanostructures ceramics and ferroelectric polymers and compares their energy harvesting capabilities and piezoelectric properties. Piezoelectric inorganic materials with a perovskite structure, such as lead magnesium niobate−lead titanate (PMN−PT, d33 = 2500 pCN−1) and lead zirconate titanate, d33 = 500–600 pCN−1) PNGs, generate the highest output voltage and current density among all piezoelectric materials. However, the piezoelectric coefficient d31 (−28 to ≈−69 pC N−1) of PMN−PT is lower than PZT (−175 pC N−1) and its toxicity and expensive fabrication process have limited its utilization. Cellular polypropylene (PP) as a ferroelectret polymer offers a high piezoelectric coefficient d33 (250−1400 pC N−1), although their d31 is lower than piezoelectric poly(vinylidene fluoride) (PVDF) polymer. Piezoelectric natural polymers such as cellulose (d33 ≈ 8−28 pC/N, silk (d33 ≈ 0.3−0.8 pC/N, and collagen (d33 ≈ 22 pC/N are also introduced for bio‐PNG applications to tackle environmental problems. There is still a research gap on rationally designed self‐powered, wearable, stretchable, and biocompatible PNGs with high and controllable energy conversion efficiency.

Converting acoustic energy into electric energy can not only suppress environmental noise but also provide energy supply, which is a potential way to solve the bottleneck problem of energy supply in wireless sensor networks (WSNs). An acoustic energy harvester structure and circuit system combining Helmholtz resonance effect with piezoelectric effect are proposed in this article. The band gap characteristics of the designed acoustic energy harvester are analyzed by plane wave expansion (PWE) theory and experiment. The substrate of Helmholtz resonator is made from piezoelectric sheet, and the acoustic energy harvester structure is arranged periodically. When the incident noise frequency keeps coincidence with the resonant frequency, the conversion efficiency goes high up to 21.3%. The influence of series and parallel connection of piezoelectric elements on the acoustic to electric energy is observed. The AC-DC conversion circuit is designed with rectifier bridge, and the energy storage circuit is designed with supercapacitor. The power obtained from the acoustic to electric energy conversion system is 1523 mW. Application tests indicate that the noise suppresses, energy conversion, and energy storage can be realized at the same time by the proposed acoustic energy harvester system.

Flexible and ferroelectric electrospun PVDF- non-stoichiometric PZT nanogenerators (PENGs) membranes for low-frequency acoustic energy harvesting

The design, fabrication, and analysis of omnidirectional gradient-index (GRIN) phononic crystals (PnCs) for acoustic wave focusing and energy harvesting have been demonstrated both numerically and experimentally. Despite that omnidirectional functionality is a key factor to alleviate the directivity dependence issues, the concept has not yet been incorporated into acoustic energy harvesting. In this work, a symmetrical GRIN PnC structure consisting of cylinders with variation in filling fractions has been presented to tailor the spatial acoustic refractive index, thus enforcing the acoustic waves in any direction toward the targeted center area for focusing purposes. Both a numerical simulation and experimental validation confirm substantial sound energy amplification of the designed GRIN PnC over a broad frequency range from 250 Hz to 1 kHz. Notably, the maximum sound amplification occurs at the hybrid resonant frequency of the GRIN PnC structure and the acoustic duct system used to generate incident plane waves. Numerical simulation reveals that the cavity resonance and the refraction of the GRIN PnC mainly contribute to enhanced sound amplification in addition to the reflection from the acoustic duct. The GRIN PnC structure coupled with the acoustic duct system leads to enhanced harvesting output performance when integrated with a piezoelectric energy harvesting device.

Enhanced metamaterial vibration for high-performance acoustic piezoelectric energy harvesting

Sound pollution has been capturing more and more attention around the world. Piezoelectric materials convert acoustic energy into electrical energy and actively attenuate the sound simultaneously. In this paper, an electro-spun nonwoven polyvinylidene difluoride nanofiber membrane as a high-performance piezoelectric material is found to have an ultra-high acoustoelectric conversion capability at the low sound frequency range. The novelty of the material in this paper is the proposed electro-spun piezoelectric nano-fiber web, which presents a strong acoustic-to-electric conversion performance. The piezoelectric acoustic energy harvester consists of the polyvinylidene difluoride nanofiber membrane that vibrates under the sound wave excitation. The piezoelectric acoustic energy harvester device can precisely detect the sound of 72.5 Hz with a sensitivity as high as 711.3 mV Pa-1 which is higher than the sensitivity of a commercial piezoelectric poly (vinylidene fluoride) membrane device. The energy harvesting performance of the piezoelectric acoustic energy harvester device is simulated by the comsol software and then validated with the experimental results to illustrate its excellent energy harvesting ability. Based on the validated simulation model, a regression parameter model is developed from the comsol software simulation results using the response surface method. The empirical regression parameter model is applied to predict the energy harvesting performance of the acoustic energy harvester from input design parameters or material property parameters where the sensitivity of the design parameters or material property parameters and their interactions can be analyzed. The design or material property parameters can be optimized for the best energy harvesting performance based on the regression parameter model. The optimization results show a significant improvement in the energy harvesting performance. The sensitivity of the parameters on the energy harvesting performance also indicates the potential of the large-scale application of this acoustic energy harvester.

Reprogrammable acoustic metamaterials for multiband energy harvesting

A renewable low-frequency acoustic energy harvesting noise barrier for high-speed railways using a Helmholtz resonator and a PVDF film

This paper reports a suspended coil, electromagnetic acoustic energy harvester (AEH) for extracting acoustical energy. The developed AEH comprises Helmholtz resonator (HR), a wound coil bonded to a flexible membrane and a permanent magnet placed in a magnet holder. The harvester’s performance is analyzed under different sound pressure levels (SPLs) both in laboratory and in real environment. In laboratory, when connected to 50 Ω load resistance and subjected to an SPL of 100 dB, the AEH generated a peak load voltage of 198.7 mV at the resonant frequency of 319 Hz. When working under the optimum load resistance, the AEH generated an optimum load power of 789.65 µW. In real environment, the developed AEH produced a maximum voltage of 25 mV when exposed to the acoustic noise of a motorcycle and generated an optimum voltage of 60 mV when it is placed in the surroundings of a domestic electrical generator.

The future of ultrasonic cameras in industrial inspection

<span>Acoustic energy harvesting is one o</span><span lang="EN-US">f</span><span> many ways to harness </span><span lang="EN-US">acoustic </span><span>noises as wasted energy into use</span><span lang="EN-US">f</span><span>ul </span><span lang="EN-US">electical </span><span>energy using an acoustic </span><span>energy harvester. </span><span>Acoustic </span><span>energy harvester t</span><span lang="EN-US">h</span><span>at tested by Dimastya (2018) </span><span lang="EN-US">which is consisted of loudspeake</span><span>r </span><span lang="EN-US">and Helmholtz resonator, </span><span>produced two-peak spectrum. It is </span><span lang="EN-US">suspected</span><span> that the </span><span lang="EN-US">f</span><span>irst peak </span><span lang="EN-US">is due t</span><span>o </span><span lang="EN-US">Helmholtz</span><span> resonator resonance and the second peak </span><span lang="EN-US">comes</span><span lang="EN-US">from the resonance of the conversion </span><span>loudspeaker. </span><span lang="EN-US">This research is to experimentally confirm the guess of the origin of the first peak. The experiments are performed by adding silencer materials on the resonator inner wall which are expected to be able to reduce the height of first peak and to know </span><span>how </span><span lang="EN-US">they</span><span> a</span><span lang="EN-US">ff</span><span>ect t</span><span>he output electric power spectrum o</span><span lang="EN-US">f</span><span> t</span><span>he acoustic energy harvester. </span><span lang="EN-US">Three different silencer materials are used, those are</span><span> glasswool, acoustic </span><span lang="EN-US">f</span><span>oam, and styro</span><span lang="EN-US">f</span><span>oam</span><span lang="EN-US">,</span><span> with</span><span lang="EN-US"> the same thickness of</span><span> 12 cm. </span><span lang="EN-US">The r</span><span>esult</span><span lang="EN-US">s</span><span> show that glasswool absorb</span><span lang="EN-US">s</span><span> sound more e</span><span lang="EN-US">ff</span><span>ectively than acostic </span><span lang="EN-US">f</span><span>oam and styro</span><span lang="EN-US">f</span><span>oam. The use o</span><span lang="EN-US">f</span><span> glasswool, acoustic </span><span lang="EN-US">f</span><span>oam, and styro</span><span lang="EN-US">f</span><span>oam with 12 cm thickness lowered the </span><span lang="EN-US">f</span><span>irst peak </span><span lang="EN-US">by</span><span> 90% (</span><span lang="EN-US">f</span><span>rom 39 mW to 0,5 mW), 82% (</span><span lang="EN-US">f</span><span>rom 39 mW to 0,7 mW), and 82% (</span><span lang="EN-US">f</span><span>rom 39 mW to 0,7 mW), respectively. </span><span lang="EN-US">Based on these results, it is concluded that the guess of the origin of the first peak is confirmed.</span>

Piezoelectret films prepared by irradiated cross-linked polypropylene (IXPP) not only feature a large figure of merit (d33 · g33, FoM) and a nearly flat response of the sensitivity as a microphone (4 mV Pa−1) in the audio range, but also exhibit a good impedance match to air. Therefore, this material is appropriate for air-coupled sonic and ultrasonic applications. In this work, we report acoustic energy harvesting using IXPP piezoelectret films without mass loading both in ultrasonic and low-frequency ranges. Under an input sound pressure level (SPL) of 100 dB (or 2 Pa) and a resonance frequency of 53 kHz, a maximum output power of 7.2 nW is obtained for an IXPP film harvester. Despite its high resonance frequency, the large FoM of IXPP piezoelectret films suggests itself to be a promising candidate also for low-frequency acoustic energy harvesting with the help of Helmholtz resonators. An output power of 10.3 nW is achieved for a harvester with a 16 cm2 large IXPP film within a Helmholtz resonator, which features a resonance frequency of 900 Hz, with an optimized load resistance of 962 kΩ under an input SPL of 100 dB. In comparison to acoustic energy harvesters based on ferroelectric polymer polyvinylidene fluoride cantilever beams, our devices have much higher output power density under the same conditions and much broader bandwidth. Theoretical analysis and numerical simulations are performed to confirm the experimental results. Moreover, the output power of the IXPP acoustic energy harvesters can be further improved by increasing the active area of the piezoelectret films.

To harvest acoustic energy from urban railways, a novel and practical acoustic energy harvester is developed. The harvester consists of a piezoelectric circular plate and a Helmholtz resonator. Based on the field test data of urban railways, the resonance frequencies of the piezoelectric circular plate and the Helmholtz resonator are near 800 Hz. The Helmholtz resonator is designed to amplify the sound pressure. Thus, a lumped parameter model is established. The piezoelectric circular plate is used to convert mechanical energy into electrical energy. The simulation results show that the output power of the harvester is approximately 25 μW and the maximum voltage is 0.149 V under the excitation of urban railway noise. The experiment device is also developed. The maximum output power of the harvester is 8.452 μW, and the maximum voltage is 0.082 V. The experimental and the numerical results are in good agreement and demonstrate the effectiveness of the proposed acoustic energy harvester.