Commercialization of lithium-oxygen batteries faces many challenges, such as electrolyte decomposition, short cycle life, low energy and power density, and high cell mass. However, the ...commercialization of LiO2 batteries for aeronautics is more challenging due to additional safety constraints on cyclability and performance (high specific-power and specific-energy). In this paper, we perform experiments and use the results to calibrate a 1-D finite element model to simulate discharge profiles up to 5 mA cm-2. The calibrated model is used to perform parametric studies of geometrical, microstructural, transport, and material properties for different discharge times, and discharge current densities. Next, a simulation-based optimization study shows optimal cell designs for various electrolytes for high specific-power.
Results show that a high specific-power LiO2 cell needs to have a cathode with a thickness equal to oxygen diffusion length, thin separator, optimized anode, and other components with low mass. The specific-power is sensitive to discharge time, discharge current density, and microstructural and geometrical properties. Also, in some cases, electrolytes with high oxygen solubility or high external partial pressure can compensate for electrolytes with low oxygen diffusivity. However, reducing the cell mass is the most straight forward path to improving specific-power.
•Cathode in cells for high specific power applications need to be thin and porous.•High specific power cells need to be optimized for high current and low cell mass.•Li-O2 for aviation is a challenging problem but not a significant barrier.•Oxygen transport properties in an electrolyte is crucial to maximize specific power.
•Electric field distribution of various electrospinning geometries was studied.•Various collector, auxiliary electrodes, and multi-nozzle designs were reported.•Macroscopic fiber properties can be ...controlled by manipulating electric field.•Fiber alignment, spatial deposition, and productivity were analyzed.
Electrospinning has emerged as one of the most versatile and extensively used approaches to synthesize nanofibers for a diverse range of applications. The production of custom nanofibrous assemblies with controlled fiber orientation, spatial deposition, and high productivity is desirable for emerging applications that demand new electrospinning system designs. The electric field plays a major role in determining the jet trajectory and thereby its manipulation can provide us with a tool to create desired fibrous architectures. In this work, we have systematically studied the three aspects of electrospinning system, specifically, collector/target designs, auxiliary electrodes, and multi-nozzle configurations using finite element simulation. The electric field distribution for different designs were analyzed and correlated with the literature-reported experimental studies to envisage the resultant macroscopic properties of the fibers. It was established that the alteration in electric field distribution can be exploited to control and enhance the fiber alignment, spatial deposition, and productivity.
To develop efficient and cost-effective desalination technologies is crucial for addressing the globally increasing needs for drinking water. One such desalination technology that is growing is ...capacitive deionization (CDI), wherein ions are electrically removed from water passing through or between two porous conducting electrodes. As the CDI field grows, design principles for scaling from small CDI cells to larger units and modules will become increasingly important. Thus, we have investigated the flow distribution in single flow-through CDI cells and interconnected modules to determine architectural principles that can feasibly reduce the pressure drop with good throughput, thus increasing energy efficiency. The most important principles found include massive parallelism, open regions to symmetrically distribute flow, and tailoring the permeability of the electrodes and spacers. Crucially, we demonstrate how simply rerouting the flow reduces the pressure drop through the cell by a factor of four in a two-cell system. Finally, we leverage the found principles to a cylindrical CDI cell well-adapted to modular up-scaling. In conclusion, implementing the design principles leads to a significant reduction in pressure drop and energy consumption of a CDI system, which is essential for upscaling to larger modular systems for practical use.
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•Simulations of water flow in capacitive deionization cell stack•Pumping energy cost reduced through efficient cell stacking design.•Pressure drop reduces to a quarter in two-cell stack.•Structural principles such as parallelism, tailored permeability, and symmetry•Novel cylindrical structure for efficient operation for upscaling
This paper reports the preparation of a new class of eco- friendly sorbents as well as the study of the continuous dynamic sorption of diclofenac (DF) chosen as a model representative of ...pharmaceutical pollutants. Biomass based on palm waste was used as base material in the presence of 27% commercial polymer carbopol as granular support, 10% tween 80 as surfactant and NaOH in the preparation of hydrophobic and organophilic effective sorbent grains. Multiple experiments were conducted to investigate the impact of initial diclofenac concentration (20–50 mg/L), flow rate (1.11–1.82 L/h), and column height (10–15 cm) on the breakthrough curve. The maximum adsorption capacity was found to be 137 mg/g under a flow rate of 1.11 L/h, column height 15 cm and inlet concentration of diclofenac of 20 mg/L. The experimental data obtained data were fitted using the empirical models of Thomas, Yoon - Nelson and Adam-Bohart. The reusability assessment demonstrated the potential for reusing this active biomass for a minimum of three adsorption –desorption cycles. The breakthrough curves indicated a positive correlation between breakthrough time and column height, while initial diclofenac concentration and flow rate exhibited negative correlations. The utilization of the Thomas model effectively described the sorption process, supported by a highly satisfactory correlation coefficient (R² > 0.98). However, a marginal decrease in the sorption capacity of diclofenac was observed with the number of sorption-desorption cycles, with reductions of 24%, 10%, and 5%, respectively.
The energy transition can also be promoted by the sustainable use of biomass. Residual biomass in the Mediterranean areas can be exploited to a greater extent through highly efficient fuel cell ...systems. The Direct Biomass-SOFC project is based on a direct coupling between biomass power supply and SOFC tubular cells. This research project stems from the need to cover the electricity demand, avoiding the use of non-renewable sources. It will be investigated the unused or little-used biomass sources that can be exploited from the Mediterranean area.
To this purpose, analyses were conducted to model a SOFC tubular cell stack by investigating the optimal configuration. The basic objective is to design a SOFC tubular cell stack, fed by syngas to produce at least 200 W. Two configurations were chosen: a square and a circular arrangement. Another objective of the study is to choose the best temperature control system. It have been selected a pressurised water system and an air system. The results show that the best performance is guaranteed by a square arrangement with an air temperature control system. The circular configuration provides less power than the square configuration, being limited by the multiple series connection to the lowest current value. The maximum electrical power produced with the square configuration is 225 W.
•The Direct Biomass SOFC system was developed numerically for 25 tubolar cells.•25 tubolar cells were able to produce 225 W from syngas.•The square tubolar cell arrangement showed better results.•The air temperature control system showed better results.
The stationary-head prototypes unusually are designed using low cost manufacture and simple construction, without bolt or nut to join both the stationary-head and shell. The shell has four holes to ...supply hot/cold fluid, and next to the tube-sheet hole to supply cold/hot fluid, the position both of them are inside the stationary-head. The calculation of the dimensions of the heat exchanger aims to determine the quality of the heat exchanger based on the overall heat transfer coefficient, impurity factor, and the pressure drop that will occur.Calculations using the LMTD method, obtained that receive heat released has a large unity with time Q, then the heat received by cold fluid is Q = 4565.16 W, LMTD produced also shows the number 20, with a proven factor (F) is 1. Comparison obtained from the calculation of the tube side and shell side is the value of Re generated is greater than the value of Re on the shell side.
Enabling fuel cell operation at high current density is critical for developing competitive alternative power system to replace internal combustion engine. However, liquid water management continues ...to be a challenge for high humidity or high current density operation. Water condensation in the porous media hinders efficient oxygen transport to the catalyst layer, which in turns, reduces fuel cell performance. To improve water management capability, the gas diffusion layer is often impregnated with Polytetrafluoroethylene (PTFE) and coated with a thin microporous layer, which have shown to improve fuel cell performance, especially under wet conditions. However, the fundamental mechanism that drives the performance enhancement is still not well understood. In this work, the effects of PTFE impregnation and MPL were studied using both experimental and computational techniques. Both limiting current and polarization tests under dry and wet operating condition are conducted to study the oxygen transport resistance and fuel cell performance. In addition, a 2-D, two-phase, multi-physics PEMFC model is developed to simulate performance and gain a fundamental understanding of local water saturation and oxygen concentration. The combined results show that 5 wt% PTFE impregnation with MPL significantly enhances liquid water management, which enables higher current density operation of a fuel cell.
•Effects of PTFE impregnation and MPL are studied experimentally and computationally.•EDX images show more PTFE exists on the surface of the GDL than in the bulk.•The tortuosity to porosity ratio of the MPL is around 6.2 under compression.•Increasing PTFE loading in the GDL is not sufficient to prevent electrode flooding.•Adding hydrophobic MPL on the cathode is crucial for wet operating conditions.
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•COMSOL Multiphysics reveal the electric field distribution of synthetic samples.•Discharge channel developed along the magnetite edge and retains the complete form.•Magnetite alters ...the distribution state of electric field within synthetic samples.•Quartz particles hinders the development of certain discharge channels.
Herein, COMSOL Multiphysics is proposed to discuss the electric field distribution of synthetic sample during the high voltage pulse discharge crushing. The pulses number required for high voltage pulse discharge to crush the synthetic sample filled with magnetite is lower than that required for quartz-filled samples. The embedding mode that the magnetite is located on the central line between the high voltage electrode and the grounding electrode of the synthetic sample is most conducive to electrical breakdown of synthetic sample. The discharge channel developed along the magnetite edge and retains the complete crystal form of magnetite. Differences in dielectric constants are responsible for variations in electric field distribution. Magnetite alters the distribution state of electric field within synthetic samples to derive higher electric field intensity and more extensive areas with high electric field intensity. The peak electric field intensity at the interface of magnetite particles is higher than that of quartz. The presence of quartz particles hinders the development of certain discharge channels.
Sodiophilic Au nanoparticles on CNT/CC can effectively reduce the sodium metal nucleation overpotential and guide the sodium metal deposition. Sodium metal is uniformly deposited into Au-CNT/CC hosts ...investigated by in-situ optical microscopy and the simulation results.
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Na metal anode has attracted increasing attentions as the anode of sodium ion batteries (SIBs) due to its high theoretical capacity, low redox potential and high abundance. However, the formation of uncontrollable Na dendrite during repeated plating/stripping cycles hinders its further development and application. Herein, a sodiophilic Na metal anode host is developed by sputtering gold nanoparticles (Au NPs) into interconnected carbon nanotube modified carbon cloth (CNT/CC) to form a Au-CNT/CC architecture. Sodiophilic Au NPs effectively guide the Na metal uniform deposition and three-dimensional (3D) microporous structure offers a large surface area for nucleation and reducing the current densities. The regulated uniform Na metal deposition mechanism is investigated by the in-situ optical microscopy and simulation analysis. As a result, Au-CNT/CC electrode exhibits a low nucleation overpotential (2.2 mV) and stable cycle performance for 1600 h at 1 mA cm−2 with 2 mAh cm−2. Moreover, it even exhibits a long cycle stability for more than 800 h at 5 mA cm−2 with 2 mAh cm−2. To explore its application, a full cell coupled with a sodium vanadium phosphate coated with carbon layer (NVP@C) cathode is assembled and delivers an average discharge capacity of 80.6 mAh g−1 and coulombic efficiency of 99.6% for 400 cycles at 100 mAh g−1. Furthermore, a flexible pouch cell with Na@Au-CNT/CC as the anode is fabricated and demonstrated good flexibility and future application of wearable electronics.
The strong covalent bonding of SiC makes it difficult to be fully sintered using conventional sintering techniques. Therefore, electrical current-assisted sintering techniques such as spark plasma ...sintering are needed to sinter SiC. The finite numerical simulations have been generally used to predict and guide sintering processes of ceramics (i.e.TiC,AlO3). In this work, the numerical simulations of the temperature distribution, electrical field and thermal field on the porous SiC cylindrical samples by Comsol were investigated in details. The influence of porosity on the temperature distribution and electrical field distribution of the SiC samples were analyzed. Both the maximum current density (1.19 × 107A/m2) and the maximum temperature (2030 °C) of the SPS device occurred at the punch/spacer interface. The temperature values at the centre of the samples were proportional to the porosity, and the temperatures at the center of the samples increased from ∼1960 °C to ∼2010 °C at t = 2000s, with the porosity increasing from 1% to 60%. The uniformity of the temperature distribution deteriorated as the porosity increases, and the temperature gradients between the center and edge of the samples with the porosity of 1% and 60%, were ∼80 °C and ∼130 °C at t = 2000s, respectively.
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