Average Output Voltage Research Articles

High Capacity and Ultralong Lifespan Aqueous Lithium-Bromine Batteries Realized by Low-Cost Concentrated Electrolyte Coupled with Dependable Lithium Titanium Phosphate.

Aqueous halogen batteries are gaining recognition for large-scale energy storage due to their high energy density, safety, environmental sustainability, and cost-effectiveness. However, the limited electrochemical stability window of aqueous electrolytes and the absence of desirable carbonaceous hosts that facilitate halogen redox reactions have hindered the advancement of halogen batteries. Here, a low-cost, high-concentration 26 m Li-B5-C15-O6 aqueous solution incorporating lithium bromide (LiBr), lithium chloride (LiCl), and lithium acetate (LiOAc) was developed for aqueous batteries, which demonstrated an expanded electrochemical stability window of ca. 2.5 V. In addition, the electrochemical performance of the electrolyte in various carbonaceous hosts (graphene, activated carbon, and nitrogen-doped activated carbon (NAc)) was systematically investigated. In-depth analysis using X-ray photoelectron spectroscopy and Raman spectroscopy revealed that the NAc host promoted the redox kinetics of active bromine species and improved the delivery capacity of the battery. Results revealed that the electrolyte in the NAc host achieved a discharge specific capacity exceeding 376 mA h g-1 while maintaining a capacity retention rate of up to 97% after 7800 cycles. When paired with hierarchically porous LTP@C/CNTs anode material, a LTP@C/CNTs-NAc full cell was constructed, which delivered a discharge specific capacity of 238.4 mA h g-1 and an average output voltage of 1.24 V. Moreover, it demonstrated a reversible specific capacity of 158.2 mA h g-1 with near-complete Coulombic efficiency over more than 10,000 cycles.

The Impacts of Different Salinities on the CW-MFC System for Treating Concentrated Brine

This paper aims to comprehensively explore the performance and influencing factors of the constructed wetland–microbial fuel cell (CW-MFC) system when treating brine with different concentrations. The main objective is to determine how different salinity levels affect the operation and treatment efficiency of the CW-MFC system. The research results show that Bruguiera gymnorrhiza exhibits strong salt tolerance and can be used as a wetland plant for the CW-MFC system. The closed-circuit CW-MFC system with planted plants has the best performance, with a chemical oxygen demand (COD) removal rate of 84.8%, a total nitrogen (TN) removal rate of 68.12%, and a chloride ion (Cl−) removal rate of 29.96%. The maximum power density is 64.79% higher than that of the system without planted plants. The power generation performance of the system first increases and then decreases with the increase in salinity, while the internal resistance keeps decreasing. When the salinity is 2%, the power generation effect is the best, with an average output voltage of 617.3 ± 25.7 mV and a power density of 45.83 mW/m2. The removal rates of COD and TN are inhibited with the increase in salinity, while the removal rate of total phosphorus (TP) is not significantly affected. The microbial community grows well under salt stress, but its structure is different. When the salinity is 1%, the optimal distance between electrodes is 10 cm. Considering the pollutant removal performance, the optimal hydraulic retention time is 3 days, and considering the power generation performance, the optimal hydraulic retention time is 2 days. This research provides important value for improving the performance of the CW-MFC system in treating brine.

Investigating ultrasonic piezoelectrics for photovoltaic cooling: Effects of the height and temperature of submerged water

In this study, ultrasonic piezoelectrics submerged in water are utilized to generate cold-water vapor for cooling a photovoltaic panel. The research experimentally investigates the impact of water temperature (5–25 °C), water height (5–7 cm), and the number of piezoelectrics (1–5) on the average temperature, temperature distribution, output voltage, and output power of the panel. To ensure consistent environmental conditions for comparison, all tests were conducted within a solar simulator. The results indicated that the photovoltaic panel performance improves with lower water temperature and height, and an increased number of piezoelectrics. Specifically, the steady-state temperature of the panel, which was 58.23 °C without cooling, was reduced to 34.36 °C by using five piezoelectrics in water at 5 °C and a height of 5 cm. Additionally, analysis revealed that as the water height decreases from 7 cm to 5 cm at water temperatures of 5 °C and 25 °C, the panel’s output voltage increases by 2.64 % and 2.86 %, respectively. Moreover, it was demonstrated that lowering the water temperature from 25 °C to 5 °C and decreasing the water height from 7 cm to 5 cm resulted in a 5.80 % increase in the panel’s power output, rising from 6.03 to 6.38.

Engineering π‐Electron Bridge Enables Low‐Potential 2D Redox Polymer Anodes for High‐Voltage Aqueous All‐Organic Batteries

AbstractAqueous all‐organic batteries (AAOBs) have emerged as a hot topic but their development was plagued by limited choices of anode materials, generally facing an intractable trade‐off between low potential and high stability. Here, we propose a novel π‐electron bridge engineering strategy to explore a class of 2D dioxin‐bridged redox covalent organic polymer (RCOP) as trade‐off‐breaking anodes for high‐voltage AAOBs. By establishing a tunable RCOP platform, we perform theoretical study to scrutinize how bridge units between active sites affect the electrode potential and redox activity for the first time. We discover that compared to common pyrazine bridge, the weakened conjugation and strong electron donor character of the proposed dioxin bridge can induce elevated LUMO level and enriched π‐electron populations in active sites, heralding a low electrode potential and enhanced redox activity. Besides, the nonaromaticity‐induced molecular flexibility of dioxin bridge mitigates intermolecular stacking for sufficient active sites exposure. To experimentally corroborate this, a new dioxin‐bridged 2D RCOP (D‐HATN) and its pyrazine‐bridged analogue (P‐HATN) are synthesized for proof‐of‐concept demonstration. D‐HATN displays excellent compatibility with Na+/Zn2+/NH4+/H3O+ and obviously lower redox potentials in various dilute electrolytes compared to P‐HATN and most reported organic anodes, while featuring rapid Grotthuss‐type proton conduction and unprecedented durability in acid – 91.8 % capacity retention after 20000 cycles. Thus, the D‐HATN‐involved all‐organic proton battery delivers an average output voltage of 0.75 V, which can be further elevated to 1.63 V with alkaline‐acidic hybrid electrolyte design, affording markedly‐increased specific energy.

Engineering π-Electron Bridge Enables Low-Potential 2D Redox Polymer Anodes for High-Voltage Aqueous All-Organic Batteries.

Aqueous all-organic batteries (AAOBs) have emerged as a hot topic but their development was plagued by limited choices of anode materials, generally facing an intractable trade-off between low potential and high stability. Here, we propose a novel π-electron bridge engineering strategy to explore a class of 2D dioxin-bridged redox covalent organic polymer (RCOP) as trade-off-breaking anodes for high-voltage AAOBs. By establishing a tunable RCOP platform, we perform theoretical study to scrutinize how bridge units between active sites affect the electrode potential and redox activity for the first time. We discover that compared to common pyrazine bridge, the weakened conjugation and strong electron donor character of the proposed dioxin bridge can induce elevated LUMO level and enriched π-electron populations in active sites, heralding a low electrode potential and enhanced redox activity. Besides, the nonaromaticity-induced molecular flexibility of dioxin bridge mitigates intermolecular stacking for sufficient active sites exposure. To experimentally corroborate this, a new dioxin-bridged 2D RCOP (D-HATN) and its pyrazine-bridged analogue (P-HATN) are synthesized for proof-of-concept demonstration. D-HATN displays excellent compatibility with Na+/Zn2+/NH4 +/H3O+ and obviously lower redox potentials in various dilute electrolytes compared to P-HATN and most reported organic anodes, while featuring rapid Grotthuss-type proton conduction and unprecedented durability in acid - 91.8 % capacity retention after 20000 cycles. Thus, the D-HATN-involved all-organic proton battery delivers an average output voltage of 0.75 V, which can be further elevated to 1.63 V with alkaline-acidic hybrid electrolyte design, affording markedly-increased specific energy.

Removal of nutrients and bioelectricity generation from institutional wastewater using constructed wetland-microbial fuel cell

This study evaluated the removal of nutrients from institutional wastewater and the generation of bioelectric power using a microcosm-scale constructed wetland system integrated with a microbial fuel cell (CW-MFC). The research explored the impact of vegetation on both bioelectric production and wastewater treatment within the wetland matrix. Results indicated that the CW-MFC system with vegetation outperformed the unplanted system in terms of treatment efficiency. The planted modules achieved average total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 94.6 % and 90.0 %, respectively, compared to 90.59 % and 83.5 % in the unplanted system. Notably, the CW-MFC planted with Scirpus atrovirens exhibited the highest average output voltage (0.648 V) and power density (232 mW/m³). In contrast, the unplanted CW-MFC produced a maximum voltage of 0.537 V and a power density of 220 mW/m³. These findings suggest that Scirpus atrovirens enhances both the treatment efficiency and bioelectricity generation by facilitating microbial activity involved in the biodegradation of organic compounds and improving electron flow from the anode to the cathode. The significant nutrient removal efficiencies and bioelectric power generation demonstrate the potential of using a vegetated CW-MFC system to achieve sustainable wastewater treatment while simultaneously producing renewable energy, thus contributing to more eco-friendly waste management practices

Changes in the microbial community structure and diversity during the electricity generation process of a microbial fuel cell with algal-film cathode

Abstract A two-chamber microbial fuel cell (MFC) with algal-film cathode was constructed. It showed good electric-generating performance with three electric-generating stages: start-up, development, and stable. An average output voltage reached ~0.412 V during the stable period. A maximum power density during continuous operation was 19.76 mW/m2. Bacterial samples were collected from the anode in the three stages (A1, A2, and A3), and their community structure and diversity were analyzed using Illumina MiSeq high-throughput sequencing technology. A total of 4238 operational taxonomic units were identified based on the number of taxa. At the phylum level, Proteobacteria and Bacteroidetes played a dominant role in the three stages and increased significantly during electricity generation. Compared with A1, the relative abundances of Proteobacteria in A2 and A3 increased by 23.30% and 32.06%, respectively, whereas those of Bacteroidetes in A2 and A3 increased by 5.56% and 14.50%, respectively. At the genus level, there were differences in the composition of bacterial communities among the three stages. Acinetobacter and Chlorobium became the dominant genera in A2, replacing Nitrospira and norank_f__Saprospiraceae in A1, and Sphingobacterium and Ochrobactrum became the dominant genera in A3. According to the sample cluster and principal component analyses, A1 was clustered into one class, and A2 and A3 were clustered into a second class. This work revealed bacterial community succession at the anode of an algal-film cathode MFC during the electricity generation process, which provides a theoretical basis for the subsequent promotion of electricity generation by algal-film cathode MFCs.

Polymer-assisted dispersion of reduced graphene oxide in electrospun polyvinylidene fluoride nanofibers for enhanced piezoelectric monitoring of human body movement

Electrospun graphene oxide (GO)/polyvinylidene difluoride (PVDF) and reduced graphene oxide (rGO)/PVDF piezoelectric hybrid nanofibers were prepared via electrospinning to enhance the β-phase content of the PVDF crystal structure. The addition of rGO increased the number of nucleation sites in the PVDF matrix, leading to an improved β-phase content in the nanofibers. Although the inclusion of GO also increased the β-phase content, rGO addition resulted in higher output voltages due to its greater conductivity compared to GO. rGO/PVDF produced higher output voltages than GO/PVDF because rGO has few oxygen-containing groups on its carbon atoms. The 1 wt% GO/PVDF nanofibers exhibited an 86.24 % β-phase content and an average output voltage of 3.2 V under a 15 N load. The 0.5 wt% rGO/PVDF nanofibers demonstrated an 84.09 % β-phase content and an average output voltage of 3.66 V under the same load. The nonionic surfactant Triton X-100 improved rGO dispersal, enhancing its effectiveness in inducing β-phase formation, and increasing the number of stress concentration points in the nanofibers. A piezoelectric device composed of TX-100/rGO/PVDF nanofibers exhibited stable performance even after 1,500 load cycles, generating an average output voltage of 7.13 V under a 15 N load. This device serves as both an energy harvester and a footwear sensor, offering potential applications in new sports monitoring technologies and self-powered wearables.

Computational and Experimental Study of a Sustainable Lithium Acetate and Urea-Based Electrolyte for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are the most widely used energy storage systems in portable devices, electric vehicles, large-scale energy storage power, and other applications. The optimal performance and safety of LIBs are mainly determined by the electrolyte, which facilitates the transport of Li+ ions and promotes the formation of the SEI layer. Since commercial LIBs are predominantly composed of organic-based electrolytes, these present elevated costs, safety risks, and environmental hazards due to their elevated flammability and fluorinated composition. To address these concerns, aqueous electrolytes have been explored as safer alternatives to organic solvents. However, the use of aqueous LIB electrolytes is restricted due to the narrow electrochemical stability window of water (ESWH2O ≈ 1.23 V). This problem is usually overcomed by using superconcentrated electrolytes, including "water-in-salt" and "water-in-bisalt," which extend the ESW. However, their practicality remains uncertain due to the high concentration of fluorinated salts, which leads to increased cost and toxicity.1 In this study, we employed computational and experimental methods to investigate the use of non-fluorinated aqueous electrolytes prepared by combining different ratios of LiCH3COOH and a water-urea mixture of fixed composition (LiCH3COO-H2O-CO(NH2)2) for their use as an electrolyte for LIBs. ESWs were determined by cyclic voltammetry using GCE, Pt, and Al as working electrodes. The electrolyte with the highest ESW (3.2 V) was probed to be compatible with commercial electrodes such as TiO2, LTO, LMO, and LFP, and was used to assemble a LIB cell with LTO and LMO as electrodes. This cell presented an average output voltage of 2.3 V and a specific capacity of 105 mAh/g over 200 cycles at a current density of 0.5 A/g. Furthermore, the thermodynamic and kinetic factors associated with the electrochemical stability of the electrolyte have been studied using DFT and molecular dynamics (MD), respectively. Adiabatic redox potentials of the electrolyte species obtained by DFT show calculated ESWs higher than 4.5 V. Transport properties of the species in the electrolyte were studied via molecular dynamics and these show that the diffusion of Li+ is comparable to the diffusion observed in organic electrolytes.2 Structurally, we also observed that urea disrupts the Li-water structure, leading to a decrease in the coordination number of water molecules to Li+ (CNLi-H2O = 1.4). This result has been experimentally confirmed using NIR and Raman spectroscopy. Overall, these results demonstrate the effectiveness of employing a lithium acetate-urea-based aqueous electrolyte as an alternative to organic electrolytes for the development of more secure, environmentally friendly, and sustainable LIBs.1. Brown, J.; Grimaud, A. With Only a Grain of Salt. Nat. Energy 2022, 7 (2), 126–127.2. Galvez-Aranda, D. E.; Seminario, J. M. Ion Pairing, Clustering and Transport in a LiFSI-TMP Electrolyte as Functions of Salt Concentration Using Molecular Dynamics Simulations. J. Electrochem. Soc. 2021, 168 (4), 040511.

Precision Calibration and Linearity Assessment of Thin Film Force-Sensing Resistors

In this study, we thoroughly analyzed the linearity and repeatability of force-sensing resistor (FSR) sensors through static load tests to ensure their reliability. The novelty of this research lies in its comprehensive evaluation and direct comparison of two widely used FSR sensors, i.e., Flexiforce A201-1 and Interlink FSR-402, under various loading conditions by employing a robust calibration methodology. This study provides detailed insights into the sensors’ performances, offering practical calibration equations that enhance measurement precision and reliability, which have not been extensively documented in previous studies. Our results demonstrate that the linearity of thin film FSR sensors is highly accurate, closely resembling a straight line. We employed M1 Class weights, applying loads ranging from 20 g to 300 g. The resistance of the FSR sensors, which varies with the applied load, was measured using a voltage divider circuit and an analog-to-digital converter of a microcontroller. MATLAB was used to calculate the average output voltage for each applied load and fixed resistance. Additionally, we examined the relationships among load, FSR sensor resistance, and conductivity. Our research indicates that with precise calibration, thin film FSR sensors can be highly reliable for force measurement applications.

Improving energy harvesting through femtosecond laser surface modification of PVDF/ZnS composite nanofibrous nanogenerators for electronic applications

Surface modification in ceramic/polymer composites holds paramount importance for electronic devices applications. Laser is a versatile and flexible device for modifying the surface characteristics of various materials. Here, we propose a novel approach to enhance the energy harvesting efficiency of polyvinylidene fluoride (PVDF) and zinc sulfide (ZnS) composite nanofibrous membranes through femtosecond laser surface modification. The electrospinning technique is used to produce nanofibers with a high β-phase content in a single step. The PVDF membrane was further enriched with ZnS nanoparticles to enhance the β-phase content. The membranes were systematically investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Electron Energy Loss spectroscopy (EELS), and Fourier-transform infrared spectroscopy (FTIR) to characterize their morphological and chemical properties. Femtosecond laser was employed to induce controlled surface modifications, resulting in hierarchical microstructures and surface functionalization. The results showed patterned tracks on the fiber surface while preserving its inherent nature. To validate its utility as an energy harvesting device, the membrane's capability was assessed by measuring the open circuit voltage. The results revealing average output voltages for nanogenerators treated with laser fluences of 0.5 J/cm2, 0.7 J/cm2, and 0.9 J/cm2 are 15.6 V, 25 V, and 17 V, respectively. The maximum output voltage is observed for a laser fluence of 0.7 J/cm2, attributed to the deeper structure created, increasing the surface area of contact and deformation in the structure. This work offers promising avenues for enhancing energy harvesting efficiency and expanding the scope of electronic devices such as sensors and actuators.

Electricity Harvesting from Water Evaporation on Hierarchical Pore Gradient Silica Aerogel-Based Generators.

In this study, the electric energy harvesting capability of the hierarchical pore gradient silica aerogel (HPSA) is demonstrated due to its unique porous structure and inherent hydroxyl groups on the surface. Taking advantage of the positively charged surface of unwashed HPSA credited by the preparation strategy, poly(4-styrene sulfonic acid) (PSS) can be spontaneously adsorbed onto unwashed HPSA and shows gradient distribution due to the pore-gradient structure of HPSA. By virtue of the gradient distribution and the stronger ionization of PSS, PSS-modified HPSA (PSS-HPSA) shows enhanced electricity generation performance from natural water evaporation with an average output voltage of 0.77 V on an individual device. The water evaporation-induced electricity property of PSS-HPSA can be maintained in the presence of a low concentration of salt. The desirable salt resistance capability benefits from the unique 3D hierarchical porous structure of HPSA which ensures rapid water replenishment so as to effectively avoid the salt accumulation. The HPSA-based devices with the advantages of unique porous structure, easy functionalization, good physicochemical stability, good salt resistance capability, and eco-friendliness show great potential as water evaporation-induced electricity generators.

Flexible Tribo‐Enhanced Piezoelectric Nanogenerator Based on Aluminium Ferrite Electrospun Hybrid Nanofibers for Energy Harvesting and Patient Rehabilitation Application

AbstractMechanical energy harvesters have recently emerged as promising options for self‐powering sensors and small electronic devices. In this work, aluminum ferrite (AlFeO3)/PVDF hybrid perovskite electrospun nanofiber‐based tribo‐enhanced piezoelectric nanogenerators (TPENGs) are developed for energy harvesting. The as‐fabricated TPENG achieves an average voltage output of 52.3 V and an average current output of 1.23 µA. Additionally, the power density of the TPENG is calculated to be 0.085 W.m−2 at an 80 MΩ external resistance load. A 3D‐printed device is fabricated, containing nylon fabric (tribo‐positive) as a rotor attached to printed fins, while six (AlFeO3)/PVDF hybrid perovskite electrospun nanofiber piezoelectric nanogenerators (PENGs) wrapped with Kapton tape (tribo‐negative) serve as the stator. The three printed fins of the device are moved by a string‐based pulley, generating an open circuit voltage of 200 V and a short circuit current of 4.5 µA. The as‐fabricated 3D‐printed device with TPENGs is used to power small electronics (e.g., LEDs and watch) and an exercise setup, allowing patients to generate power by pulling the attached string, thereby estimating the level of impairment. Integrating energy harvesting into rehabilitation motivates patients to move impaired body parts, enhancing TPENG's application in healthcare as a practical and engaging tool for patient rehabilitation.

Superimposed frequency adaptive droop control strategy with balanced battery state of charge for distributed battery energy system

The conventional droop method for load sharing control in DC microgrid suffers from poor power sharing and voltage regulation, which affects the State of Charge (SoC) balance of distributed Battery Energy Units (BEUs). In this paper, an adaptive droop method based on superimposed frequency is proposed to balance the SoC among distributed BEUs. Accurate current sharing is achieved by using the introduced AC reactive power to adjust the reference voltage according to differences in line resistance. With the proposed SoC balance control method, the SoC balance among BEUs can be guaranteed by the accurate current sharing regardless of the different line resistances in the DC microgrid. In addition, voltage restoration is performed to maintain the average output voltage of the BEU at the nominal value. The effectiveness of the proposed control system is verified by simulation and HIT experimental tests.

A 8.83 ppm/°C temperature coefficient, 75 dB PSRR subthreshold CMOS voltage reference with piecewise curvature compensation

A subthreshold CMOS voltage reference (CVR) with low temperature coefficient (TC) over a wide temperature range and low power is proposed in this paper. The proposed CVR utilizes the ΔVGS of different-threshold and same-threshold nMOS pairs to generate complementary-to-absolute-temperature (CTAT) and proportional-to-absolute-temperature (PTAT) voltages, respectively. To compensate for the low-temperature and high-temperature segments of the temperature characteristic curve, the nonlinear compensation currents generated by the exponential-like relationship between the drain current and the gate-source voltage of two MOSFETs work in the subthreshold region is used. Based on a 0.18-μm CMOS process, post-layout simulation results show that the proposed CVR achieves an average output voltage of 263 mV. The power supply ripple rejection (PSRR) is −75 dB at 10 Hz and the line sensitivity (LS) is 0.0069 %/V when the supply voltage varies from 0.8 V to 2.5 V. The average TC is 8.83 ppm/°C for a wide temperature range of −40 °C–120 °C, and the minimum TC is only 3.65 ppm/°C.

Design and experimental investigation of a positive feedback magnetic-coupled piezoelectric energy harvester

A positive feedback magnetic-coupled piezoelectric energy harvester (PFM) is proposed to address the limitations of current piezoelectric energy collectors, including restricted acquisition direction, limited acquisition bandwidth, and low energy output. Firstly, the dynamic theoretical model of the energy harvester was established, and the optimization factors were explored, providing a solid theoretical foundation for subsequent research endeavors. The energy capture characteristics of rectangular beam and compound trapezoidal beam were compared through finite element simulation analysis. Subsequently, an experimental platform was constructed and an optimized experimental methodology was devised to analyze the energy capture characteristics and enhance the performance of the energy harvester. The results demonstrate that the positive feedback magnetic-coupled PFM with a trapezoidal beam exhibits superior energy capture efficiency. Furthermore, it is observed that the optimized energy harvester possesses wide frequency coverage, multi-directional capabilities, low-frequency adaptability, and facilitates easy vibration. When the 45 kΩ resistor is connected in series and subjected to a longitudinal external excitation amplitude of 0.5 g, it is capable of generating an average voltage and power output of 4.20 V and 0.39 mW respectively at a vibration frequency of 9 Hz. Similarly, when exposed to a transverse external excitation amplitude of 1 g, it can produce an average voltage output of 6.2 V and power output of 0.85 mW at a vibration frequency of 19 Hz. When the inclination angle of the energy harvester is set to 35 degrees, the maximum voltage output occurs at a frequency of 18 Hz and the Z-axis to X-axis force ratio of the energy harvester is 1.428. These research findings can serve as valuable references for piezoelectric energy harvesting applications in self-powered microelectronic systems.

Smart interference galloping energy harvester with optimally tunable gap between the bluff body and interference

This study focuses on the development of a piezoelectric wind energy harvester that utilizes the wake interference galloping phenomenon. We found that depending on the applied wind velocity, there exists an optimal gap distance between the oscillating bluff body and the interference, which produces the required wake interference galloping. Accordingly, we aimed to design a novel interference galloping–based energy harvester that can smartly adjust the bluff body location to its optimal position in response to the external wind velocity. The optimal gap distance between the two bodies for the wind velocity range considered in this study was found to be 9–15 mm, which strongly depends on the applied wind velocity. It was also observed that the phase delay of the lift force with respect to the displacement of the oscillating body plays a major role in determining the state of the system stability and that the wake interference galloping can also occur due to the memory effect. The phase angle of π/2 rad was found to be an important indicator for determining whether wake interference galloping occurs. The balance of forces on the bluff body is vital for determining the optimal location of the bluff body. The mathematical modeling was performed using the extended Hamilton principle, the Galerkin method, eigen- and multi-modal analyses, the extended Fourier theorem, and novel energy/power balance conditions that yielded the four additional equations required to compute the aerodynamic lift in an autonomous form. To identify the physical parameters for analyzing the proposed energy harvester system, a main experiment and several preliminary experiments were conducted. The analytical results were compared with the experimental data in terms of both the dynamic behavior and energy production, and they were observed to be sufficiently close (the maximum error in the averaged output power was 9.8%). The average output power from the proposed energy harvester was also compared with that from conventional interference galloping–based energy harvesters having an immobile bluff body; the results showed that the proposed energy harvester outperformed the conventional harvesters by up to 128.8%. Specifically, it generated an average output voltage of 71 V (rms) and an output power of 6.88 mW at a wind velocity of 10 m/s.

VIV array for wind energy harvesting

Harvesting energy from flow using vortex-induced vibration (VIV) piezoelectric transducers has gained significant attention in recent decades due to their advantages, such as simple structure, blade-less layout, and low maintenance costs. However, most existing studies have focused on designing and analyzing a single piezoelectric energy harvester (PEH), without investigating the fluid-structure interaction and coupling of multiple PEH arrays. Here, we conducted an experimental study using a 2 × 2 PEH array to investigate its dynamic response under different wind speeds and spacings. Results show that the output voltage of the PEH array increases as the vertical spacing decreases, and the maximum average output voltage of 20.6 V per PEH is obtained when the minimum vertical spacing, maximum horizontal spacing, and resonance wind speed conditions are met. Compared to a single PEH, the 2 × 2 array arrangement increases the average output voltage by up to 168%. Additionally, the average output power under the resistance of 1 MΩ increases by 629% to 4.3×10−4 W per PEH, and the maximum output power increases by 792% to 5.3×10−4. Experiments indicate that the vortex shedding coupling can induce higher vibration in a well-defined array, which paves a new way for developing bladeless wind farms.

EFFICIENT SYNTHESIS OF ZNO AS AN ELECTRODE OF PIEZOELECTRIC NANOGENERATORS

Piezoelectric nanogenerators (NGs) hold immense promise as self-powered devices for harvesting mechanical energy from the environment. This study introduces an efficient and scalable synthesis method for zinc oxide (ZnO) nanorods, a pivotal material in piezoelectric nanogenerators (NGs), with several key results. A Chemical Bath Deposition technique is employed, optimizing parameters such as growth time, temperature, and precursor concentrations to achieve well-aligned and high-quality ZnO nanorods. The structural and morphological characteristics of the synthesized nanorods are systematically investigated using advanced characterization techniques. The synthesized ZnO nanorods exhibit an average length of 400nm, demonstrating their slender shape. Furthermore, the study determines an energy gap value of 3.5 eV for multilayer zinc oxide thin films, indicating the transition from the valence band to the conduction band. Notably, thermal annealing at 500°C leads to a substantial increase in average output voltage, reaching 1.95 V, a fourfold improvement compared to as-deposited nanopowders. These findings emphasize the efficiency and potential of the proposed synthesis method and underscore its practical applications in enhancing energy harvesting capabilities for sustainable power generation from mechanical sources in piezoelectric NGs.

Flexographic printed microwave-assisted grown zinc oxide nanostructures for sensing applications.

The development of flexible electronics has increased the demand for wearable pressure sensors that can be used to monitor various biomedical signals. In this context, pressure sensors based on zinc oxide (ZnO) have great potential since, besides the biocompatibility and biodegradability of this metal oxide, it also has piezoelectric properties. The common feature of these sensors is the alignment of the ZnO nanostructures in the strain direction. This alignment is achieved through a three-stage procedure: deposition of a ZnO nanoparticle layer (seed layer) followed by its patterning and the subsequent growth of nanostructures from the seed layer nanoparticles. Herein, a process compatible with industrial scale for depositing seed layers by flexographic printing is proposed, allowing seed layers to be deposited and patterned swiftly and efficiently in a single step on flexible indium tin oxide coated polyethylene terephthalate substrates, significantly decreasing the time and cost required to produce pressure sensors. The growth conditions of ZnO nanorods on these substrates were also studied to analyze their influence on the morphological and structural characteristics of the nanostructures. Nanorods with length of (0.27 ± 0.04) μm and density of (296 ± 6) nanorods per μm2 were obtained in microwave-assisted hydrothermal syntheses carried out at 100 °C for 30 min, with a 1 M zinc acetate seed layer and using an equimolar growth solution of zinc nitrate and hexamethylenetetramine. These conditions were used to produce ZnO-based pressure sensors with two patterns (one square and 16 individual squares). Although the single square sensors displayed a higher average output voltage ((12 ± 5) V for an impact pressure of 150 kPa), their response was considerably more variable than the patterned sensors (with 16 squares), which displayed an average output voltage of (8 ± 2) V under an applied pressure of 150 kPa and sensitivity values of (0.06 ± 0.01) V kPa-1, demonstrating their potential for wearables and portable electronics.