Increase In Power Density Research Articles

Natural hematite as low-cost auxiliary material for improving soil remediation by in-situ microbial community.

Microbial-mineral interaction has a broad application prospect in the field of environmental remediation of organic pollutants. However, the disadvantages of long repair cycle and low repair rate limit its industrial application. In this study, natural hematite was used as an auxiliary material for soil remediation in a bio-electrochemical system. It was found that the power density of soil microbial fuel cell (SMFC) system composed of 2.0mm hematite was 2.889 mW/m2, which is 2.7 times compared with the blank group (1.068 mW/m2) in the particle size optimization experiment. A similarly increased power density (1.068 to 2.467 mW/m2) was observed when the hematite content changed from 0 to 20% in the concentration optimization experiment. Under 20% and 2.0-mm hematite condition, the phenol removal rate was closed to 99% after 7days, which is 1.9-folds compared with blank control (53%). These results suggest that addition of hematite enhances soil porosity and conductivity, and increases the number of electron acceptors in soil. These findings inspire that this economic and abundant natural mineral is expected to be a potential auxiliary material in the field of soil organic pollutant purification, and expand the understanding of interactions between hematite and microorganisms in nature.

Differential Sintering and Self‐Stress Effects on YSZ Ionic Conductivity

Thermomechanical stress simulations are combined with experimental tests to assess the effects of rigid inclusions on the sintering of 8 mol% yttria‐stabilized zirconia (8YSZ) green compacts and the phenomena of restricted and differential sintering on microstructure development and electrical properties are investigated. Rigid inclusions of sintered ceramic particles with different shapes (spherical and jagged) and compositions (alumina, 3YSZ, and 8YSZ) are added in different volume fractions (1, 5, and 15 vol%) to 8YSZ commercial powders, which are formed by isostatic pressing and sintered by conventional method. Restricted and differential sintering effects are observed in the development of the microstructure varying in function of volume fraction, shape, structural composition, and thermomechanical properties of the inclusions, resulting in different combinations of tensile and compressive strain states in the matrix, and varying electrical behaviors. The addition of 1 vol% of 8YSZ irregular rigid inclusions leads to an increase of 36% in total electrical conductivity and a 33% increase in power density under solid oxide fuel cells operation conditions compared to samples without inclusions.

Model-based quantitative characterization of anode microstructure and its effect on the performance of molten carbonate fuel cell

This paper presents research on the impact of the material microstructure on the performance of Molten Carbonate Fuel Cells (MCFC). The study is motivated by the need to increase the operation time of MCFC stacks. As the MCFC stacks are mainly composed of porous materials, the paper shows the impact of the porosity on both fuel cell performance and degradation rate. The study is based on the mathematical model, validated through experiments with varying microstructure parameters, achieving an overall relative error of 8%. The study evaluated the performance of MCFC using anodes with different porosity and found that increasing anode porosity from 40% to 70% led to a nearly two-fold increase in maximum power density. However, from both the degradation test and polarization curves, the optimal level of porosity for the anode is around 55%. The porosity level at 55% ensures the highest catalytic surface of the electrodes and is a compromise between the mechanical properties of the electrode and its electrochemical properties.

Transport Phenomena in a Banded Solid Oxide Fuel Cell Stack—Part 2: Numerical Analysis

Solid oxide fuel cells are recognized as a promising energy conversion technology. Crucial to the field is the opportunity to reduce the costs of prototyping methodology. Due to the difficulty of conducting direct measurements inside the electrodes and fuel cell’s channels, numerical modeling remains the primary tool for improving the understanding and analyzing a fuel cell operation. Here, a computational fluid dynamic simulation of a banded solid oxide fuel cell’s stack, applied to enhance the geometrical design, is shown. A mathematical model, which includes momentum, heat, mass, and charge transport phenomena, was developed and used for the numerical simulation. The model was validated against the experimental study and confirmed its accuracy. The gas flow rate influence on the performance was investigated in details. Various arrangements of fuel and air channels were simulated and analyzed, including extending the system into a short stack. The proposed design modifications led to an increase in the volumetric power density of the stack compared to the existing prototype design. The proposed mathematical and numerical models were shown to be useful for testing further design modifications to the stack, including performance analysis, by changing the operating parameters of the system or applying new materials.

Comparison of discharge mode transition of air plasma under pulsed and sinusoidal excitations

The transition from O3 to NO x discharge mode is common for air plasma with an increase of discharge power density, which greatly changes the chemistry of the plasma as well as its application effect. Although this discharge mode transition has been intensively studied in recent years, differences between plasmas subject to pulsed or sinusoidal excitations have rarely been reported on. In this study, a surface dielectric barrier discharge is excited using either a microsecond pulsed voltage or a sinusoidal voltage. The discharge mode transition of these two excitations is then comparatively studied. The results indicate that pulsed excitation produces more O3 in O3 mode discharge; the O3 concentration for pulsed excitation is 27.7% higher than that for sinusoidal excitation at the same power density of P = 0.08 W cm−2. On the contrary, it produces less NO and NO2 in NO x mode discharge; the NO concentration for pulsed excitation is 13.2% lower than that for sinusoidal excitation at P = 0.32 W cm−2. As a result, pulsed excitation delays the transition of the discharge mode when the discharge power density increases. This can be attributed to the higher electron and lower gas temperature of the pulse-excited plasma, which promotes O3 and inhibits NO x production.

Reactivity of high active aluminum powder with RDX and HMX mixtures

In order to reveal the interaction law of high active aluminum powder with RDX and HMX mixture, the thermal decomposition behavior of highly active Al powder and its interaction with typical nitramine explosive RDX and HMX were studied by differential scanning calorimetry (DSC), thermogravimetry (TG), thermo-mass spectrometry (TG-DTG-DSC-MS) and CO2 laser ignition technology. Results show that when the nanometer aluminum powder and RDX and HMX respectively, two typical nitramine explosive mixing action is of little influence on the mixing action to respond to the thermal decomposition of HMX, depress RDX points liberation degree of temperature, both the thermal decomposition process of mixed system for random nucleation and subsequent growth process, the ignition delay time decreases with the increase of laser ignition power density. The ignition delay time and ignition energy of the mixture of high active aluminum powder and RDX are greater than that of the mixture of high active aluminum powder and HMX and the high active aluminum powder.

Direct Deposition of Dense YSZ/Ni-YSZ Thin-Film Bilayers on Porous Anode-Supported Cells with High Performance and Stability

We present an approach for integrating a thin-film bilayer combination comprising a Ni(O)-YSZ nanocomposite layer and a YSZ thin-film electrolyte prepared using pulsed laser deposition into the architecture of porous Ni-YSZ-supported cells. Achieving a minimum bilayer thickness threshold of ~1.5 µm is found to be critical to achieve a high open circuit voltage value, as well as a significant decrease in the ohmic resistance to ~0.06 Ωcm2 at 750 °C and increase in maximum power density to 1.83 W/cm2. Short-term durability tests up to 45 h at a constant potential of 0.8 V showed stable operation with current densities reaching ~1.7 A/cm2. Cells utilizing thin-film bilayers can overcome issues associated degradation in conventionally sintered cells, in terms of maintaining excellent contact with the anode support and significantly suppressing Ni diffusion into the YSZ electrolyte.

Evaluation of Blended Wind Products and Their Implications for Offshore Wind Power Estimation

The Cross-Calibrated Multi-Platform (CCMP) wind analysis is a satellite-based blended wind product produced using a two-dimensional variational method. The current version available publicly is Version 2 (CCMP2.0), which includes buoy winds in addition to satellite winds. Version 3 of the product (CCMP3.0) is being produced with several improvements in analysis algorithms, without including buoy winds. Here, we compare CCMP3.0 with a special version of CCMP2.0 that did not include buoy winds, so both versions are independent of buoy measurements. We evaluate them using wind data from buoys around the coasts of the United States and discuss the implications for the wind power industry and offshore wind farms. CCMP2.0 uses ERA-Interim 10 m winds as the background to fill observational gaps. CCMP3.0 uses ERA5 10 m neutral winds as the background. Because ERA5 winds are biased towards lower values at higher wind conditions, CCMP3.0 corrected this bias by matching ERA5 wind speeds with satellite scatterometer wind speeds using a histogram matching method. Our evaluation indicates that CCMP3.0 has better agreement with the independent buoy winds, primarily for higher winds (>10 m/s). This is reflected by the higher correlation and lower root-mean-squared differences of CCMP3.0 versus buoy winds, especially for higher wind conditions. For the U.S. coastal region (within 200 km), the mean wind speed of CCMP3.0 is enhanced by 1–2%, and the wind speed standard deviation is enhanced by around 3–5%. These changes in wind speed and its standard deviation from CCMP2.0 to CCMP3.0 cause an 8–12% increase in wind power density. The wind power density along the U.S. coastal region is also correlated with various climate indices depending on locations, providing a useful approach for predicting wind power on subseasonal to interannual timescales.

Topology optimization for structural mass reduction of direct drive electric machines

Topology optimization is well suited to computationally achieve highly optimized designs with respect to objective and constraint functions, and when coupled with additive manufacturing, enables the fabrication of complex structures that can offer improved generator performance and increased power density. Here, topology optimization was used for light-weighting high power direct drive generators. The rotor of a 5 MW wind turbine generator was analyzed to determine geometric avenues of mass reduction with varying safety factors. Three designs were created with safety factors between 1 and 2 which resulted in structural mass reductions ranging between 54%–67% compared to a baseline design leading to a 13%–25% increase in power density. These designs represent a ∼50% structural mass reduction compared to a previous structural optimization design using triply periodic minimal surfaces. All deflections were less than their critical limits and the topology optimized rotor designs exhibited 64% lower radial deflection than baseline. Deflections of the topology optimized designs were verified with commercial code and supported through experimental validation using digital image correlation with additively manufactured rotors. Computational resource use was reduced as compared to past parameter optimization approaches, and manufacturability studies demonstrated that topology optimization holds potential for significant mass reduction of direct drive generators.

Whispering gallery mode micro-lasing in CsPbI3 quantum dots coated on TiO2 microspherical resonating cavities.

Whispering gallery mode (WGM) lasing in CsPbI3 quantum dots (QDs) coated on TiO2 spherical microcavities is demonstrated. The photoluminescence emission from a CsPbI3-QDs gain medium strongly couples with a TiO2 microspherical resonating optical cavity. Spontaneous emission in these microcavities switches to a stimulated emission above a distinct threshold point of 708.7 W/cm2. Lasing intensity increases three to four times as the power density increases by one order of magnitude beyond the threshold point when the microcavities are excited with a 632-nm laser. WGM microlasing with quality factors as high as Q∼1195 is demonstrated at room temperature. Quality factors are found to be higher for smaller TiO2 microcavities (∼2 µm). CsPbI3-QDs/TiO2 microcavities are also found to be photostable even after continuous laser excitation for 75 minutes. The CsPbI3-QDs/TiO2 microspheres are promising as WGM-based tunable microlasers.

A 2 μm Dual-Wavelength Laser at Cryogenic Temperature with Balanced Simultaneous Emission

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature dependence of the laser spectra. The optimal temperature for balanced output evidently diminishes as the pump power density increases, thereby manifesting a rate of change quantified at 1.19 K/W. At the optimal temperature of 43.1 K, the optical-to-optical conversion efficiency of the Tm,Ho:YAP simultaneous dual-wavelength laser (SDWL) with a pump power of 11.8 W is 12.7%, corresponding to a slope efficiency of 15.8%.

High Step-Up Gain Converter Based on Two-Phase Interleaved Coupled Inductor Without Right-Hand Plane Zero

This paper proposed a novel two-phase interleaved Coupled Inductor (CI) based high step-up gain converter without Right Half Plane (RHP) zeros for a wide operating range of duty cycle. A coupled inductor between input and output is used in the proposed converter to eliminate RHP zero. The energy of CI is transferred to output capacitor when switch is ON to eliminate RHP zero. Furthermore, the converter has a wide operating range to eliminate RHP zero with a coefficient coupling of CI near one. Thus, the converter achieves higher bandwidth and a wide range of control over output voltage. The small-signal model of proposed converter is derived to verify the proposed claim. The single loop voltage control is sufficient to regulate output voltage of the converter with a good stability margin and faster dynamic response for a wide range of load changes. In addition, proposed converter has a high voltage step-up gain and low voltage stress on switching devices compared to the boost converter. Moreover, interleaved operation at input side reduces ripple and increases power density. All theoretical findings are verified by simulation and experimental results. Experimental results are provided from implemented laboratory prototype of input voltage of 24 V to output voltage of 100 V and 200 W power.

Airborne ultrasound catalyzed saltwater Al/Mg-air flow batteries

In this work, we demonstrate an ultrasonic catalysis method for promoting the ORR rate and enhancing discharge performance of saltwater Al/Mg-air flow batteries, in which focused airborne ultrasound (FAU) is utilized. Experimental results show that compared with the batteries not sonicated, the percentage increase of peak power density of batteries catalyzed by FAU can reach 28.61% for the Al-air flow battery and 33.77% for the Mg-air flow one, respectively, when the ultrasonic frequency is 608.4 kHz. The measured optimal peak power densities are up to 18.9 mW cm−2 and 73.4 mW cm−2 for the Al/Mg-air flow batteries catalyzed by FAU, respectively, when the electric catalysts loaded with Pt/C are employed for the cathode. Our numerical simulation indicates that the sound pressure and acoustic streaming on the cathode surface may enhance the oxygen diffusion. To the best of our knowledge, this is the first attempt to utilize the gas-borne ultrasonic catalysis effect to promote the ORR of metal-air flow batteries.

Recent Advances and Prospects of FeOOH-Based Electrode Materials for Supercapacitors

Supercapacitors (SCs) offer a potential replacement for traditional lithium-based batteries in energy-storage devices thanks to the increased power density and stable charge–discharge cycles, as well as negligible environmental impact. Given this, a vast array of materials has been explored for SCs devices. Among the materials, iron oxyhydroxide (FeOOH) has gained significant attention in SC devices, owing to its superior specific capacitance, stability, eco-friendliness, abundance, and affordability. However, FeOOH has certain limitations that impact its energy storage capabilities and thus implicate the need for optimizing its structural, crystal, electrical, and chemical properties. This review delves into the latest advancements in FeOOH-based materials for SCs, exploring factors that impact their electrochemical performance. To address the limitations of FeOOH’s materials, several strategies have been developed, which enhance the surface area and facilitate rapid electron transfer and ion diffusion. In this review, composite materials are also examined for their synergistic effects on supercapacitive performance. It investigates binary, ternary, and quaternary Fe-based hydroxides, as well as layered double hydroxides (LDHs). Promising results have been achieved with binder-free Fe-based binary LDH composites featuring unique architectures. Furthermore, the analysis of the asymmetric cell performance of FeOOH-based materials is discussed, demonstrating their potential exploitation for high energy-density SCs that could potentially provide an effective pathway in fabricating efficient, cost-effective, and practical energy storage systems for future exploitations in devices. This review provides up-to-date progress studies of novel FeOOH’s based electrodes for SCs applications.

Structural optimization of distribution zone for large-sized PEMFC with high power density

Proton exchange membrane fuel cell (PEMFC) is an important device to convert clean-fuel hydrogen into electricity, which has the potential to reduce pollutant emission and our dependence on fossil fuels. Of the many development and manufacturing challenges that need to overcome before large-scale commercialization can be realized, one of the most pivotal ones is flow distribution uniformity. To this end, a distribution zone with partially dotted matrix was proposed, and showed much more effectiveness when compared with the un-optimized distribution zone with an empty chamber. The positional and size effect of the dotted matrix was investigated, and results showed that flow uniformity was maximized when the dotted matrix was placed near the gas inlet. Interestingly, less dotted matrix size could achieve better performance, indicating the potential of this approach to reduce manufacturing cost. The optimized system could achieve more uniform flow with standard deviation of 1.808 × 10-8, maldistribution factor of 3.967 × 10-3 and variable coefficient of 0.4143%, more superior to other similar models reported. Furthermore, a full cell-level simulation was also conducted, affirming the superiority of the proposed model with increased power densities and water distribution uniformities.

Efficient hydrogen production from sugarcane bagasse and food waste by thermophilic clostridiales consortium and Fe–Mn impregnated biochars

In this research, a thermophilic Clostridiales consortium was enriched with pretreated sugarcane bagasse (PSCB). Then the hydrogen production of Clostridiales consortium through dark fermentation had been greatly improved through two-step strengthening. Firstly, food waste was added to optimize C/N ratio of substrate to 10.47. Secondly, Fe–Mn impregnated biochars (Fe·Mn·SB) were supplemented to the co-substrate fermentation system to further improve hydrogen production. Overall, the hydrogen production (1.71 mL H2/mL-culture) and yield (586.19 mL H2/g-carbohydrate) of Clostridiales were increased by 113.75% and 32.48% compared with that of fermentation from single PSCB, respectively. The mechanism of Fe·Mn·SB promoting hydrogen production was further elucidated. Microbial community analysis demonstrated that Fe·Mn·SB could increase the relative abundances of dominant hydrogenogen and stabilize community structure. PICRUSt analysis indicated Fe·Mn·SB boosted substrate degradation and carbon metabolism. Electrochemical analysis implied Fe·Mn·SB promoted reducing power and release of cytochrome c, stimulating extracellular electron transfer (an 18.39% increase in power density). Carbon metabolism analysis indicated that Fe·Mn·SB enhanced hydrogen-producing pathways and suppressed hydrogen-consuming pathways. The present work established a feasible process for hydrogen production by Clostridiales consortium fermentation from co-substrate, deepened the understanding of metal-modified biochars improving hydrogen production, and provided references for future research.

Electromagnetic design and performance analysis of coreless superconducting machine

With the development of offshore wind power generation, there is an urgent demand for high-power wind turbines. Superconducting machines with high power density and efficiency are one of the solutions for wind turbines of 10 MW and above. This paper summarizes the existing superconducting synchronous generators in several structural forms and features, and considers that the coreless machine can avoid the impact of core oversaturation on the power density increase of the machine, which is the development direction of the superconducting machine. In this paper, the structural topology of a coreless superconducting machine is established and the similarities and differences between its structure and that of a conventional one are analyzed. Since the conventional magnetic circuit method is no longer applicable, a designing model based on the analytical method is established for the designing of coreless machines, which considers the effects of slotless armature, the superconducting excitation winding thickness and the nonlinearity of the ferromagnetic material. Based on this method, the magnetic field distribution is solved and verified with the finite element method. Further, the effect of the superconducting excitation winding opening angle on the magnetic field in the air gap of the machine is investigated, and the machine structure is optimized based on this. The steady-state and transient performance analysis of the machine is carried out to illustrate the operating characteristics of the coreless superconducting machine. The design method and analysis results of this paper can provide a reference for building higher power density coreless superconducting wind turbines.

Studies on the Platinum Thick Film Sensor Conformally Written by Laser Micro-Cladding: Formability, Microstructure, and Performance

In this paper, laser micro-cladding technology (LMC) was conducted to prepare high-temperature Pt thick film sensors in situ. The formability, microstructure, sintering mechanism, and electrical properties of the LMCed Pt thick films were first studied systematically. Results indicated that with the increase of laser power density, the sintering degree of the Pt thick film increased obviously, improving its adhesion strength and reducing its resistivity. However, when the laser power density exceeded the threshold, holes or grooves were formed in the Pt film, leading to the degeneration of its properties. A Pt thick film with good adhesion strength, excellent conductive networks, and the minimum resistivity (46 ± 2 μΩ·cm) was obtained at a laser power density of 1.37 × 106 W·cm-2. Then, Pt thick film temperature sensors (including Pt thermal resistance temperature (RTD) and Pt-Pt10%Rh thermocouple sensors) were conformally prepared by LMC. Their temperature-sensing performance became stable after the initial high-temperature calibration, with a linearity of 0.9985 for the RTD with a TCR of 2.46 × 10-3/°C (at 920 °C) and a linearity of 0.9905 for the thermocouple with a Seebeck coefficient of 9.7 μV/°C, both of which are better than that made by direct DC magnetron sputtering deposition. Therefore, this work provides a novel feasible way to conformally integrate high-performance Pt film sensors in situ.

Scale-up single chamber of microbial fuel cell using agitator and sponge biocarriers

ABSTRACT Despite the high efficiency of microbial fuel cells (MFCs), MFCs cannot be a suitable alternative for treatment plants because of insufficient power generation and tiny reactors. Additionally, the increased reactor size and MFC stack result in a reduction in production power and reverse voltage. In this study, a larger MFC with a volume of 1.5 L has been designed called LMFC. A conventional MFC, called SMFC, with a volume of 0.157 L, was constructed and compared with LMFC. Moreover, the designed LMFC can be integrated with other treatment systems and generate significant electricity. In order to evaluate MFC's ability to integrate with other treatment systems, the LMFC reactor was converted into MFC-MBBR by adding sponge biocarriers. A 9.5 percent increase in reactor volume resulted in a 60 percent increase in power density from 290 (SMFC) to 530 (LMFC). An agitator effect was also investigated for better mixing and circulating substrate, which positively affected the power density by about 18%. Compared with LMFCs, the reactor with biocarriers generated a 28% higher power density. The COD removal efficiency of SMFC, LMFC, and MFC-MBBR reactors after 24 h was 85, 66, and 83%, respectively. After 80 h of operation, the Coulombic efficiency of the SMFC, LMFC, and MFC-MBBR reactors was 20.9, 45.43, and 47.28%, respectively. The doubling of coulombic efficiency from SMFC to LMFC reactor shows the design's success. The reduction of COD removal efficiency in LMFC is the reason for integrating this reactor with other systems, which was compensated by adding biocarriers.

Neutronic investigation of prospective dual-cooled micro-heterogeneous duplex fuel for small modular long-life reactors: Assembly level design and analysis

Nuclear fuel is a critical component of any nuclear reactor, influencing both its safety and economic viability. Continuous fuel quality improvements resulted in a significant reduction in failure rate, and assembly design changes contributed to a significant increase in power density and performance during irradiation. In terms of fuel development, a new fuel type called “dual-cooled annular fuel” has recently been proposed to be used in nuclear reactors. The dual-cooled annular fuel design benefits from heat transfer to the coolant at both the outer and inner channels. Another emerging trend in nuclear fuel development is the use of thorium-based fuel in the form of duplex fuel design. As a result, the current work is an attempt to incorporate potential dual-cooled annular duplex fuels into the assembly of an innovative Small Modular Reactor (SMR). This paper, therefore, compares the neutronic properties of annular duplex fuel to those of annular UO2 fuel. Considering the dual-cooled feature, this study presents both duplex configurations (i.e. ThO2– UO2 and UO2–ThO2). The neutronic properties include fissile loading determination, multiplication factors, discharge burnup, and isotopic concentration. This analysis also determined the reactivity coefficients, power peaking factors, energy-dependent neutron flux, and an analysis of possible burnable absorbers and configurations. The results of this study show that both annular duplex fuels can achieve 6% higher discharge burnup than annular UO2 fuel, despite nearly identical reactivity values at the beginning of the cycle. The production of plutonium and other minor actinides has been greatly reduced. Annular duplex fuels have lower power peaking factors, which are beneficial for reactor operation, and the UO2–ThO2 configuration performs better. The calculated reactivity feedback coefficients show negative patterns and are within the annular UO2 fuel's range. The proposed annular duplex fuel designs have additional intriguing neutronic properties that open up possibilities for future research.