Optimum Power Density Research Articles

Significant Potential of Cocos nucifera L. Bunches Waste as Carbon Source for Sustainable Electrode Material Supercapacitors

The interest in utilizing biowaste materials to produce carbon source, especially for electrode materials in physicochemical energy storage devices like Li-ion batteries and supercapacitors, is driven by concerns regarding energy cost-effectiveness and environmental pollution. This study specifically concentrates on the utilization of waste from Cocos nucifera L. bunches as an eco-friendly source of carbon source designed for supercapacitor electrodes. The precursors chosen in this study were old Cocos nucifera L. bunches and young Cocos nucifera L. bunches. The preparation involves chemical activation of the waste using a 0.5 M potassium hydroxide solution at 900°C, with pyrolysis occurring in an nitrogen and carbon dioxide gas environment. The resultant activated carbon, configured as monolithic coins, retains its structure by optimizing the bonding characteristics of the precursor, eliminating the necessity for supplementary adhesives. Every coin-shaped monolith displays carbon structures ranging from turbostratic to highly amorphous. Electrochemical testing in a symmetric supercapacitor showed old Cocos nucifera L. bunches a high specific capacitance of 262 F g−1 at a constant density of 1.0 A g−1. Furthermore, the maximum energy density was determined to be 3.54 Wh kg−1 at an optimal power density of 85 W kg−1 in 1 M H2SO4 aqueous electrolyte. Utilizing waste, combined with a straightforward preparation process and remarkable electrochemical properties, positions carbon source derived from aged Cocos nucifera L. bunches as a prospective and sustainable electrode material for energy storage applications in supercapacitors.

Boosting energy harvesting of fully flexible magnetoelectric composites of PVDF-AlN and NiO-decorated carbon nanofibers

The increasing popularity of wearable electronics has sparked interest in flexible energy harvesters as alternatives to conventional batteries. Flexible magnetoelectric (ME) composites, known for converting ambient magnetic field energy into useable power, are emerging as promising autonomous energy sources for integration into wearable devices. In this study, we prepared flexible (PVDF-AlN)–(NiO–CNF) based ME composites using two different methods: solution-casting and electrospinning techniques. The ME coupling was confirmed by measuring the ferroelectric and magnetic properties of the composite, and it was qualitatively characterized through the ME coupling coefficient. The electrospinning fibers-based ME composite exhibited an optimal value of 10.6 V/cm.Oe, significantly higher than the solution-casting films-based ME composite (1.3 V/cm.Oe) under a 1 kHz AC magnetic field (off-resonance condition). Subsequently, a flexible magneto-mechano-electric (MME) generator was designed using electrospun-derived material, harvesting a sinusoidal wave with a maximum output peak-to-peak voltage of 9.02 V. The generator displayed an optimal DC power density of 97 μW/m2 when exposed to a weak AC magnetic field of 6 Oe at a frequency of 50 Hz. Consequently, it holds great promise as an efficient autonomous power supply for medical sensing and various miniature electronic applications.

Effect of laser shock peening on the retention ability of surface roughness in forged Cr5 steel

The roughness retention ability of the work roll surface during the cold rolling process is of great significance, especially in the production of the high-quality rolling section. Laser shock peening (LSP) is an advanced and effective surface treatment technique to improve the fatigue life, wear resistance, and other mechanical characteristics of metal components. Current studies commonly examined the reinforcement effect of single and multiple LSP treatments on Cr5 steel samples through XRD analysis, hardness testing, and residual stress measurements of different parameters. In addition, the abrasion test is widely conducted to determine the wear resistance. Compared to unprocessed samples, LSP could promote grain refinement and thus significantly increase the hardness and residual stress. Furthermore, the slight decrease in surface roughness shows that LSP treatment is an effective approach to slowing down the roughness decline rate and prolonging the roller service life. It is also found that multiple LSP impacts could remarkably improve the surface roughness retention of Cr5 steel, in which the optimal laser power density was around 23 GW/cm2.

The Application of Cows Rumen for Electricity Generation Through The Implementation of A Ceramic-Based Microbial Fuel Cell System

The growth in population is not adequately matched by the corresponding increase in energy demand. The imperative for prioritizing the exploration of alternative energy sources that possess attributes of safety, affordability, and ample access to raw materials cannot be overstated. An energy source with significant potential is a microbial fuel cell (MFC)-based energy source. This study aims to investigate the utilization of cow rumen as a substrate and source of nutrition in the bioenergy system of microbial fuel cells (MFCs). The present study aims to investigate the impact of substrate concentration and bacterial incubation duration derived from bovine rumen bacteria on the attainment of optimal power density. The research employed a Dual Chamber Microbial Fuel Cell (MFC) device using a Proton Exchange Membrane (PEM) constructed from ceramic materials. Daily observations were conducted over a period of 30 days. The performance of MFC was assessed utilizing the polarization technique. The findings indicated that altering the proportion of bovine rumen bacterial substrates and the duration of bacterial incubation had an impact on the power density seen in the Microbial Fuel Cell (MFC) system. The optimal conditions were attained when the substrate concentration reached 3640 ppm and after 7 days, resulting in a maximum power density of 864 mW/m2.

A Novel IPT System With Full-Range Soft-Switching Operation and Magnetic Integration Based on Dual-Decoupling Concept for Efficiency and Power Density Optimization

A Novel IPT System With Full-Range Soft-Switching Operation and Magnetic Integration Based on Dual-Decoupling Concept for Efficiency and Power Density Optimization

Highly Immobilized Bimetallic Fe/M‐N4 (M‐ Mg or Zn) Conductive Metal–Organic Frameworks on Nitrogen‐Doped Porous Carbon for Efficient Electrocatalytic Hydrogen Evolution and Oxygen Reduction Reactions

Herein, a simple method is proposed for developing bimetallic Fe/M‐N4/nitrogen‐doped porous carbon (NPC) (M‐Zn or Mg) conductive metal–organic framework (c‐MOF) composites because of their great potential in replacing conventional catalysts. The prepared composite MOF exhibits remarkable catalytic activity for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), surpassing the performance of the state‐of‐the‐art transition metal‐N4 cathode catalysts. These composites demonstrate excellent selectivity for a four‐electron transfer, facilitated by an associative reaction pathway that functions as the rate‐determining step. Therefore, they offer high half‐wave and onset potential values for ORR, i.e., 0.92 and 1.02 V for Fe/Mg‐N4‐NPC (hexaminobenzene (HAB)‐3@NPC) at a current density of 4.11 mA cm−2, and 0.89 and 0.99 V for Fe/Zn‐N4‐NPC (HAB‐2@NPC) at a current density of 3.8 mA cm−2, respectively. In addition, they provide low overpotentials of 21 and 64 mV at the current density of 10 mA cm−2 with Tafel slopes of 47.9 and 34.2 mV dec−1 for HER, respectively. Furthermore, when utilized as the cathode in bifunctional electrode assembly cells, they provide low cell voltages of 1.412 V at a current density of 20mA cm−2. In the membrane electrode assembly, the HAB‐3@NPC composite demonstrates an optimal power density of 0.861 Wcm−2, thus underscoring its potential in practical applications.

Spinel Ni-doped LiMn2O4 cathode material with high oxygen reduction catalytic performance for low temperature solid ceramic fuel cells

In this work, Ni-doped LiMn2O4 spinel oxides were studied as the cathode materials of low temperature proton ceramic fuel cell. Increasing the content of doping Ni to 0.5, the calculated active energy of the polarization process of the cell decreased from 0.62 to 0.49 eV. The cell performance increased with the Ni doping of LiMn2O4 cathode, and the optimal power density reached to 547 mW cm−2 at 550 °C with a low polar resistance of 0.42 Ω cm2 for LiNi0.5Mn1.5O4. Ni partially replacing Mn at the B site could increase the content of Mn4+, resulting in the increase of oxygen vacancy content to maintain the charge balance, which is beneficial to the oxygen reduction reaction. These results demonstrate that spinel oxide could be a promising cathode material with highly oxygen reduction activity for advanced low temperature solid ceramic fuel cells.

Numerical performance analysis of the solid oxide fuel cell for aviation hybrid power system

A detailed three-dimensional model of solid oxide fuel cell (SOFC) is established to explore its performance under special requirements in the aviation SOFC - gas turbine hybrid system. In this context, the SOFC has the distinction of pressurization, lightweight and low pressure loss compared to its conventional independent application. Based on this, the SOFC performance is fully investigated in terms of different operating conditions and geometric dimensions, and in addition to typical electrochemical parameters, the power-to-weight ratio is also considered as evaluation indicator. The results indicate that high operating pressure is beneficial for improving SOFC electrochemical performance, but the performance enhancement becomes slow when pressure exceeds 0.5 MPa. The inlet velocities of fuel and air both affect fuel utilization and power density of SOFC. And the high air velocity is favorable to reduce the SOFC temperature and temperature gradient, but it also increases the pressure drop. Therefore, the air inlet velocity of 2 m/s-15 m/s is more suitable under comprehensive consideration. In addition, the optimal power density and power-to-weight ratio correspond to different rib widths, with the former having wider ribs and differing within 0.5 mm. And this characteristic is maintained at different pressure, contact resistance and interconnect density.

Maximizing power density in proton exchange membrane fuel cells: An integrated optimization framework coupling multi-physics structure models, machine learning, and improved gray wolf optimizer

This study proposes an innovative optimization framework to optimize channel structure and maximize power density by coupling multi-physics structure models, machine learning, and swarm intelligence algorithms. First, proton exchange membrane fuel cells (PEMFC) imitated water-drop block channels are employed for constructing multi-physics structure models. A database of the PEMFC output performance under various structural parameters of imitated water-drop block is established. Then, a machine-learning-based surrogate model is constructed based on the adaptive boosting (AdaBoost) ensemble algorithm to predict the output performance under different channel parameters. Finally, the improved gray wolf optimizer (IGWO) fitness function is calculated using a surrogate model to establish an optimization framework for effectively optimizing the channel structure. Results show that the AdaBoost ensemble surrogate model predicts the PEMFC polarization curves with extremely high accuracy and efficiency within one second. The optimization framework is capable of swiftly predicting both the optimal channel structure and maximum power density in under two minutes. The predicted values are returned to the physical model for validation with an error of only 3.96%. Simultaneously, the optimal channel structure can effectively enhance the PEMFC performance. The proposed optimization framework will guide the performance prediction and channel structure multivariate optimization.

Dual-Anion Regulation for Reversible and Energetic Aqueous Zn-CO2 Batteries.

Aqueous Zn-CO2 batteries can not only convert CO2 into high-value chemicals but also store/output electric energy for external use. However, their performance is limited by sluggish and complicated CO2 electroreduction at the cathode. Herein, a dual-anion regulated Bi electrocatalyst is developed to selectively reduce CO2 to formate with a Faradaic efficiency of up to 97% at a large current density of 250mAcm-2. With O and/or F, the rate-determine step of CO2 electroreduction has been manipulated (from the first hydrogenation to *HCOOH desorption step) with a reduced energy barrier. Significantly, the fabricated Zn-CO2 battery exhibits a high discharge voltage of 1.2V, optimal power density of 4.51mWcm-2, remarkable energy density of 802Whkg-1, and energy-conversion efficiency of 70.74%, stability up to 200 cycles and 68h. This study provides possible strategies to fabricate reversible and energetic aqueous Zn-CO2 batteries by addressing cathodic problems.

Wind farm power density optimization according to the area size using a novel self-adaptive genetic algorithm

This work studies the power density (PD) optimization in wind farms, and its sensitivity to the available area size. A novel genetic algorithm (PDGA) is introduced, which optimizes PD and the turbine layout, by self-adapting to the PD and to the solutions diversity. PDGA uses the levelized cost of energy (LCOE) as cost function, which in turn employs the EPFL analytical wake model to derive the power output. For the baseline area size, PDGA reduces 2.25% the original LCOE, 2.6 times more than optimizing with constant PD. PDGA-driven solutions provide 11% and 6% LCOE reductions against the default layout for the smallest (6.4 km2) and largest (386 km2) scaled wind farm areas, respectively. Specially relevant for the industry, PDGA solutions depict convex fronts for area vs. LCOE or vs. PD, which allows determining the required area or turbine number given a target LCOE. Unlike default layouts, optimized ones reveal a linear relationship between LCOE and PD. The mean turbine spacing tends to 8-9D for very large areas. The economics-optimized PDs are below the estimated PD available in the atmosphere. This work is limited to a simplified, offshore wind climatology, a specific wind turbine model, and the LCOE specifications used herein.

Magnetoelectric coupling optimization in lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 and Ni0.5Zn0.5Fe2O4 nanocomposites for magneto-mechano-electric generator

Magneto-mechano-electric (MME) generators efficiently harness ubiquitous stray magnetic fields and convert them into electricity, capturing significant attention for powering innumerable wireless sensors. In this study, lead-free 0-3 particulate magnetoelectric (ME) nano-composite ceramics, specifically x(Ba0.85Ca0.15Zr0.1Ti0.9O3)-(1-x)Ni0.5Zn0.5Fe2O4 [x(BCT-BZT)–(1-x)NZFO], were synthesized using the sol-gel method. Subsequently, a flexible MME generator was designed, incorporating the optimized ME composite. Structural parameter calculations indicated higher tetragonal distortion of 0.4% in 0.4(BCT-BZT)-0.6NZFO, possibly due to uniform particulate distribution. The ME composites displayed uniform dual-phase microstructures, with 0.4(BCT-BZT)-0.6NZFO showing a higher NZFO concentration. The maximum values of the magnetodielectric (MD) and ME coupling coefficients have been determined to be -3.6% and 2.55 mV cm -1 Oe-1, respectively, for an x = 0.4 composite. The MME generator is designed using an optimized 0.4(BCT-BZT)-0.6NZFO ME composite with film thickness of 34 μm. This MME generator harvests a sinusoidal wave with a maximum output peak-to-peak voltage of 4.1 V when exposed to a weak AC magnetic field of 10 Oe at a frequency of 50 Hz. Additionally, the device demonstrates an exceptional optimal DC power density of 3.89 μW cm-3. The lead-free 0-3 particulate ME composite enables effective magnetic energy harnessing. As a result, it holds great promise as an efficient autonomous power supply for various Internet of Things based applications.

Integrated Taguchi and response surface methods in geometric and parameter optimization of PEM fuel cells

AbstractProton exchange membrane (PEM) fuel cell has emerged as a promising alternative to fossil fuels as it is employed to generate electricity for portable applications with low carbon emissions. However, the high cost of the technology hinders its widespread commercialization. Optimizing PEM fuel cell model parameters is crucial in performance improvement and production cost reduction. This study presents an optimization approach for a PEM fuel cell operating and design parameters by integrating Taguchi and Response Surface Methodology. A 3D‐CFD model of a PEM fuel cell is developed and used as a base model for the optimization study. Thirteen input parameters with notable effects on the fuel cell's performance are selected for this study. By the Taguchi method, these parameters decreased from thirteen to five. A response surface methodology (RSM) Box‐Behnken experimental design is employed to study the interactions of the parameters on the power density. The optimum working parameters that result in optimum power density of 0.8476 W cm−2 include an operating pressure (2.5 bar), temperature (80°C), flow channel width (1.30 mm), membrane thickness (0.036 mm), and catalyst layer thickness of 0.01 mm. This study provides a quick and efficient way of optimizing PEM fuel cell model for maximum power density.

Progress and perspectives in thermoelectric generators for waste-heat recovery and space applications

The direct conversion of thermal energy into electrical current via thermoelectric (TE) effects relies on the successful integration of efficient TE materials into thermoelectric generators (TEGs) with optimized characteristics to ensure either optimum output power density or conversion efficiency. Successfully employed for powering deep-space probes and extraterrestrial rovers since the 1960s, the development of this technology for waste-heat-harvesting applications faces several key issues related to the high temperatures and oxidizing conditions these devices are subjected to. This Perspective provides a brief overview of some prospective thermoelectric materials/technologies for use in radioisotope thermoelectric generators utilized in space missions and highlights the progress made in the field over the last years in the fabrication of TEGs. In particular, we emphasize recent developments that enable to achieve increased power densities, thereby opening up novel research directions for mid-range-temperature applications. In addition to showing how using lower quantities of TE materials may be achieved without sacrificing device performance, we provide an outlook of the challenges and open questions that remain to be addressed to make this technology economically and technologically viable in everyday-life environments.

Designing an asymmetric supercapacitor based on Co(OH)2@PANI nanocomposite synthesized via a facile hydrothermal method

The present study developed a Co(OH)2@PANI nanocomposite synthesized by a simple hydrothermal method as a novel electrode material for supercapacitor construction. The prepared nanocomposite is characterized through various techniques, including N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The prepared supercapacitor was subjected to evaluate using cyclic voltammetry and galvanostatic charge/discharge tests in a 6.0 M KOH electrolyte solution. The incorporation of Co(OH)2 microneedle-like structures into polyaniline (PANI) has greatly enhanced the performance of the supercapacitor. In a three-electrode setup, the supercapacitor utilizing Co(OH)2@PANI nanocomposite electrode exhibits a high specific capacitance of 385 F g−1 at 1 A g−1. Even when the current density was increased to 10 A g−1, the capacitance retention remains at 67 %. In the asymmetric device, the capacitance retention was maintained at nearly 74.8 % after 5000 cycles. Additionally, the supercapacitor yields an optimum energy density and power density of 31.2 Wh kg−1 and 1050 W kg−1, respectively.

(Digital Presentation) Biogenic Electrodes for Low-Temperature Solid Oxide Fuel Cells

Biogenic Electrodes for Low-Temperature Solid Oxide Fuel Cells Jyoti Bhattacharjee, Subhasis Roy* Department of Chemical Engineering, University of Calcutta, 92 A. P. C. Road, Kolkata-700009, India * Email: subhasis1093@gmail.com/srchemengg@caluniv.ac.in : Solid oxide fuel cells (SOFCs) are potential energy-generation devices. They operate at hightemperatures, typically between 800°C-1000°C, limiting their utility. The primary challengein developing these fuel cells is synthesizing strong biogenic electrodes that function at lowtemperatures, maintaining high performance. This experimental study examines how eco-friendly,facile, and novel techniques for synthesis can be used to make robust, effective, and affordableelectrodes for low-temperature recyclable SOFCs (LT-SOFC). A green approachwas implemented by using biomass waste and biochar, specifically coconut shells and ricehusks, as raw materials. The synthesis comprised the hydrothermal carbonization of biomassprecursors, such as lignocellulosic nanostructures, and carbon nanotubes under controlledconditions, followed by activation with potassium hydroxide(KOH). The resulting electrodeshad a large surface area, catalytic oxygen reduction, excellent conductivity, and sufficientelectrochemical performance. The efficacy of the biomass-derived electrodes was enhancedby employing transition metal oxides as electrocatalysts, such as nickel oxide(NiO) andcobalt oxide(Co3O4). The morphology and elemental composition of the electrode materialwere studied using the scanning electron microscope(SEM) and energy-dispersive X-rayspectroscopy(EDS). Electrochemical impedance spectroscopy(EIS)was used to examine theelectrochemical properties of cell electrolytes. Findings demonstrated that the hydrothermalstrategy led to the formation of homogeneous and porous electrode structures with highgalvanic activity. The biodegradable LT-SOFC stack achieved an optimal power density of346mW/cm2 at around 550°C, indicating a substantial increase over previous experiments.Our results have significant economic consequences for the expansion of sustainable andrenewable energy innovations in industry and nanotechnology, providing auxiliary power inautomobiles and hydrogen generation. Greenhouse gas emissions and carbon footprint can bediminished by using biomass waste streams as feedstocks, reducing the need for fossil fuels.The outcomes of this research provide important insights into the development, challenges,and future possibilities of biomass-derived electrodes, and minimal temperature electrolytesfor stable SOFCs. Keywords: Biomass-derived; carbon footprint; electrochemical efficiency; green energy; low-temperature solid oxide fuel cells; nanotubes.

Ni-Metal organic framework nanosheets and Ni3C/biomass porous carbon composite based long cycle life asymmetric supercapacitor

Asymmetric supercapacitors (ASCs), with their exceptional energy density and wider potential window while ensuring optimum power density, have gained substantial interest. Here, we introduce an ASC using Nickel-Metal Organic Framework (Ni-MOF) synthesized via On-pot solvothermal process as positive electrode and a hydrothermally grown composite encompassing Nickel-MXene with biowaste-derived brinjal carbon (MXAC) as negative electrode. The morphological analysis reveals the nanosheet-like morphology of Ni-MOF, whereas MXAC has a porous carbon skeleton bonded with MXene. In three-electrode configuration Ni-MOF shows specific capacitance of 536 F/g at 1 A/g at 0 to 0.4 V, while MXAC has 298 F/g at -1 to 0 V with 2M KOH. Further, the Ni-MOF//MXAC ASC device demonstrates specific capacitance of 146 F/g at 1 A/g with 1.5 V in 2M KOH, owing to the synergistic combination of Ni-MOF nanosheets with porous MXAC. Additionally, it provides 45.6 Wh/kg of energy density at power density of 750 W/kg and 85% capacitance retention after 10,000 cycles, signifying excellent stability.

Wearable Piezoelectric Films Based on MWCNT-BaTiO3/PVDF Composites for Energy Harvesting, Sensing, and Localization

Polymer-based lead-free piezoelectric composites provide environmentally friendly and scalable space for energy conversion and structural health monitoring. In this paper, multi-walled carbon nanotubes (MWCNT)-BaTiO3/polyvinylidene fluoride (PVDF) piezoelectric composite films for energy harvesting, sensing, and localization were prepared. The highest β-phase content of 90.21% in PVDF composite nanofibers was achieved owing to the synergistic effect of MWCNT and BaTiO3 nanoparticles. The open-circuit voltage of the flexible piezoelectric nanogenerator based on interdigital electrodes reached 11.4 V at 2 Hz and a bending strain of 4 mm with an optimal power and power density of 8.67 μW and 1.16 μW/cm2, respectively, and can light up to 8 LED lights simultaneously. The output voltage did not decay during 1800 cycles, which met the power and stability requirements of a commercial capacitor. In addition, the prepared piezoelectric sensors exhibited anisotropy and high sensitivity. They had a maximum amplitude sensitivity of 93 dB, which was superior to the reported PVDF-TrFE sensors and suitable for low-frequency signal monitoring in the range of 20–40 kHz. Localization accuracy was greater than 90% in linear and planar localization tests, demonstrating the potential of preparing acoustic emission sensors. These properties facilitate the reduction of the quantity of sensors required to identify the source of damage.

Transition metal sulfide/oxide nanoflowers decorated on poly (aniline-2-sulfonic acid) modified polyacrylamide derived carbon cathode catalyst for bioenergy generation in microbial fuel cells

Microbial fuel cells (MFCs) are promising carbon-free energy devices with the potential to harvest power and treat wastewater simultaneously, which is crucial to meet the emerging energy challenges. Despite the high theoretical power output, the performance of MFCs is dependent on the cathodic oxygen reduction reaction (ORR) to generate electricity. Herein, a hybrid nanostructure of nickel-cobalt sulfide (NiCo2S4) nanosheets over NiCo2O4 nanoflowers on in-situ nitrogen and sulfur-doped carbon (NSC) is prepared by direct pyrolysis. Deposition of NiCo2S4 nanosheets improves the effective contact with the electrolyte and increases the catalytic sites for ORR. NiCo2S4/NiCo2O4@NSC shows an oxygen reduction peak at 0.150 V, limiting current of -0.093 mA, close to -0.107 mA for Pt/C and generates optimal power density of 831.74 mW m−2 comparable to Pt/C (857.92 mW m−2) and higher than NiCo2O4@NSC (665.86 mW m−2), NSC (650.28 mW m−2) and NC (485.98 mW m−2) air cathodes. This could be attributed to the high degree of graphitization, appropriate N and S content, a synergistic effect between the metal species and the heteroatoms, and better catalytic surface area utilization. The results suggest that M-N-S-based carbons could be potential cathodes for microbial fuel cells and similar energy devices.

Power Density Optimization Based Parameter Design Method for the Capacitive Power Transfer System With Magnetic-Core Inductors

Power Density Optimization Based Parameter Design Method for the Capacitive Power Transfer System With Magnetic-Core Inductors