Seeing the Middle: Reconstructing 3D Internal Electrode Microstructures from Low‐Resolution Surfaces with Generative Diffusion Artificial Intelligence

Integrated gasification fuel cell (IGFC) systems combining coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally friendly utilization of coal for power production. Most IGFC system analyses performed to-date have used nondimensional thermodynamic SOFC models that do not resolve the intrinsic constraints of SOFC operation. In this work a quasi-two-dimensional (2D) finite volume model for planar SOFC is developed and verified using literature data. Special attention is paid to making the model capable of supporting recent SOFC technology improvements, including the use of anode-supported configurations, metallic interconnects, and reduced polarization losses. Activation polarization parameters previously used for high temperature electrolyte-supported SOFC result in cell performance that is much poorer than that observed for modern intermediate temperature anode-supported configurations; thus, a sensitivity analysis was conducted to identify appropriate parameters for modern SOFC modeling. Model results are shown for SOFC operation on humidified H2 and CH4 containing syngas, under coflow and counterflow configurations; detailed internal profiles of species mole fractions, temperature, current density, and electrochemical performance are obtained. The effects of performance, fuel composition, and flow configuration of SOFC performance and thermal profiles are evaluated, and the implications of these results for system design and analysis are discussed. The model can be implemented not only as a stand-alone SOFC analysis tool, but also a subroutine that can communicate and cooperate with chemical flow sheet software seamlessly for convenient IGFC system analysis.

Commercialization of solid oxide fuel cell (SOFC) systemsrequiresimproved SOFC performance and durability, which is highly dependenton the coupling of the SOFC stack with other auxiliary components,SOFC stack configuration, and electrode microstructure. Optimizationof SOFC systems at the system/stack/cell/electrode scale via experimentationis expensive and challenging, whereas numerical modeling can be fastand cost-effective. Although many excellent reviews on SOFCs havebeen published, the previous articles lack practical problem-orientedliterature classification and do not cover new emerging models, suchas artificial intelligence (AI) assisted models, heterogeneous models,and so on. These models are important for accelerating the solutionof large-scale multiphysics models and describing mesoscopic electrodebehaviors. In this review, a top-down approach is adopted that cantruly guide SOFC system/stack/cell/electrode design to meet targetedapplications. Another distinct feature of this review is the inclusionof the latest developments in SOFC modeling. This review offers athorough summary and in-depth analysis of an extensive collectionof research on SOFC simulations, classifying the models into distinctcategories based on their varying scales, and serves as a valuabletool to assist researchers in selecting the most suitable models fordiverse research objects.

Recent approach based heterogeneous comprehensive learning Archimedes optimization algorithm for identifying the optimal parameters of different fuel cells

Integrated gasification fuel cell (IGFC) systems combining coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally friendly utilization of coal for energy production. Most IGFC system analyses performed to date have used non-dimensional thermodynamic SOFC models that do not resolve the intrinsic constraints of SOFC operation. In this work, a one-dimensional finite volume model for planar SOFC is developed and verified using literature data. Special attention is paid to making the model capable of supporting recent SOFC technology improvements, including the use of anode-supported configurations, metallic interconnects, and reduced polarization losses. Results are presented for SOFC operation on humidified hydrogen and methane-containing syngas, under co-flow and counter-flow configurations; detailed internal profiles of species mole fractions, temperature, current density and electrochemical performance are obtained. The effects of performance, fuel composition and flow configuration on SOFC performance and thermal profiles are evaluated, and the implications of these results for system design and analysis are discussed.

Simulation of a tubular solid oxide fuel cell stack using AspenPlusTM unit operation models

Introduction With the recent enhancement of renewable energy utilization, large scale energy conversion and storage become more important to control the surplus electric power due to the unsteady power generation. Reversible hydrogen energy storage system via solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) are expected as a high efficient device because of its high operating temperature (600℃~1000℃). It is possible to unify them to one device as reversible system (RSOFC/EC), but it is necessary to understand the mechanism of FC/EC reactions and design the device with a good balance between FC and EC in order to apply them for an actual energy system. While SOFC reaction models and many electrochemical data of electrodes have been developed and reported by many researchers, there are few reports to investigate the reaction model of SOEC. Thus, it is possible to predict the performance of SOEC based on a comprehensive SOFC/EC models and experimental data of SOFC, because the reactions of SOFC and SOEC are a reversible relationship and the equal value of IR loss can be applied. However, the comprehensive SOFC/EC electrochemical model has not been established. A series of experimental data of anodic and cathodic current density vs. the potential should be investigated at various conditions to develop the SOFC/EC model. In this work, a series of anodic and cathodic electrode performance was taken using a SOFC in various conditions. Furthermore, attempting to predict SOEC performance from SOFC performances, we proposed and discussed a new model of electrolysis based on our developed SOFC model. Experimental The Disks of 8 mol% Y2O3-ZrO2 (YSZ; 0.25 mm thickness, 20 mm diameter) were used as the electrolyte and the anode was a Ni/YSZ or Ni/GDC composite, and the cathode was a La0.8Sr0.2MnO3/ScSZ composite. We measured the dependence of the current density of anodes on oxygen activity with wide range to get both power generation and electrolysis data for various gas composition (PH2=0.3~0.99 atm, PH2O=0.01, 0.03, 0.05 atm). Results and Discussion 1. Method to fit parameters on the SOFC/EC model We have developed the electrochemical reaction model on the fuel electrode (=anode) based on the equilibrium of competitive adsorption and oxygen activity, ao , specified by anode potential (Eq.1, Table.1) [1]. The SOFC model was constructed by assuming competitive adsorption equilibrium of H2, H2O and O on Ni surfaces at three-phase boundary and the rate-determining step to be Langmuir-type reactions of H with O (Table.1). We obtained an equation of the electrical current density, i, as a function of the oxygen activity (ao ) calculated from the anode potential which is simply measured from experiments. To confirm effectiveness of the model, we fitted the model to actual experimental data described by i vs. ao . From the equations of model on Table.1, each current density of SOFC (ia ) and SOEC(ic ) are described as Eq.2. To draw the plot of i vs. ao on the model, the rate constants (ka, kc ) and the equilibrium constants (KO, KH, KH2O ) need to be defined as reliable value. Thus, from the equilibrium potential vs. 1 atm O2 (Eq.3), we defined the rate constant of kc as Eq.4. When the kc became a dependent variable of ka , then we fitted ia to power generation experimental data described by i vs. ao so that the values of KHKO/KH2O were fitted approximately. Finally, i c model could be drawn on the plot of i vs. ao and the maximum value of i c was obtained by Eq.5 which is independent of ao and Eq.6 was obtained using Eq.4. 2. Experimental results and parameter fitting on the SOFC/EC model As the expreimental results, the maximum power density of SOFC with Ni/YSZ was 588.5 mW/cm2 for FC mode at PH2=0.99 atm, PH2O=0.01 atm, and ic(max) was 0.285 A/cm2 for EC mode at PH2O=0.03 atm. However, ic(max) calculated by the model (Eq.6) was 0.050 A/cm2. Also, in case of SOFC with Ni/GDC, ic(max) was 0.400 A/cm2 for EC mode at PH2O=0.03 atm, while ic(max) calculated by the model (Eq.6) was 0.055 A/cm2. The electrolysis current density measured by our RSOFC/EC showed 6 times higher than model values approximately. This result suggested the possibility that additional parallel reaction path was existed. In this presentation, we will discuss the possible electrochemical paths to explain the disagreement between the model and the experimental data. Finally, the comprehensive SOFC/EC model will be proposed to predict EC performance using SOFC data.

This research focuses on the performance analysis and control of a solid oxide fuel cell (SOFC) with direct internal reforming using methane as fuel. Firstly, the steady state analysis is performed to design the optimal operational condition for this system. The direct internal reforming of methane in SOFC can utilize the heat from the exothermic electrochemical reaction to produce hydrogen-rich gas, leading to an increasing system efficiency. However, the coupling of the endothermic reforming and electrochemical reactions results in a complicated dynamic response. Therefore, the effect of input variables on the cell temperature and cell voltage is analyzed to investigate the dynamic behavior that is important for design a controller. It is found that the cell operating temperature and cell voltage are dependent on the fuel and air inlet temperature as well as the current density. Next, to achieve the efficient control system, the control structure design of the SOFC is considered to identify good controlled variables and manipulated variables. The concept of a controllability analysis is applied to the control system design of the SOFC for the selection of input-output pairings by considering the relative gain array (RGA). The result shows that the inlet molar flow rates of air and fuel are manipulated variables to control the cell temperature and the content of fuel, respectively. Finally, the conventional and advanced control techniques are designed and implemented to control the cell temperature, the content of methane and the cell voltage. In this research, the model predictive control (MPC) that is a model-based control strategy is proposed for SOFC control. In general, MPC requires the accurate and reliable model of the process to be controlled. However, the SOFC model is complicated and involves uncertain parameters. Therefore, an off-line robust MPC algorithm is developed and employed for controlling the SOFC. The robust MPC algorithm based on linear time-varying (LTV) and linear parameter varying (LPV) systems is also studied. The simulation results show that under the model uncertainty, the proposed robust MPC can control the SOFC and guarantee the stability of the SOFC. The robust MPC algorithm using the LPV model of the SOFC can achieve a better control performance because the model parameters are on-line updated and used in the control calculation.

Implementation of nano-catalyst materials into solid oxide fuel cell (SOFC) electrodes to improve performance and stability has been widely studied. Addition of the nano-catalysts into an electrode structure serves to enhance the electrochemical performance of the SOFC by increasing the Triple Phase Boundary (TPB) area, improving redox stabilization, and modifying reaction kinetics of hydrocarbon gases that cause anode degradation due to carbon deposition.Typical Ni-based cermet anodes suffer from anode deactivation due to carbon build up under hydrocarbon flows. Carbon builds up and covers the TPB area which results in poor electrochemical performance. Larger carbon deposits can block pores within the anode microstructure which leads to gas diffusion issues. Carbon buildup also causes mechanical stresses to the electrode due to volumetric changes which can lead to fracture and complete failure of the cell.This work studied nano-catalyst decoration of the Ni-based cermet anodes with catalysts that promote internal reforming to protect against coking. The addition of active metal components and ceramic reforming promoters were investigated. Multi-component systems with several catalysts were also examined. Uniform incorporation of nano-catalyst into the anode microstructure was achieved through a patented liquid phase surfactant assisted process (using various catechol surfactants). Deposition loading densities and distribution of nanoparticles was controlled by altering the surfactant and catalyst solution concentrations.This work defined initial morphology and studied the coarsening/annealing kinetics of nano-catalysts used for enhanced solid oxide fuel cell (SOFC) operation. Nano-catalyst depositions were performed on flat single crystal surfaces using a bio-inspired surface modification technique. 3D profiles of the nanoparticles at various coarsening stages were obtained using atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) was used to track the changes in composition. Figure 1 shows AFM imaging of single component cerium oxide and cobalt oxide depositions on flat single crystal yttrium stabilized zirconia (YSZ) before and after 24 h of annealing in reducing conditions.Impregnated SOFCs were tested for 200+ h in constant load while operating under high methane fuel streams. Fuel compositions were selected to have high hydrocarbon content to accelerate degradation. Deposition techniques were optimized for multi-component internal reforming catalysts to obtain sustained performance enhancement. Current-voltage-power (I-V-P) measurements and electrochemical impedance spectroscopy (EIS) results were used for evaluation. Post-mortem microstructure and chemistry characterizations were used in analysis.Impregnated SOFCs demonstrated greater than 50% sustained improvement in harsh environments in long-term tests where the anode was subjected to 40% CH4 for 200+ h. Acknowledgements: Work supported by a subcontract under the GE Aerospace’s US DOE- ARPA-E project (DE-AR0001344) entitled “FueL CelL Embedded ENgine (FLyCLEEN)”. Material characterization and imaging work was made possible with the support of the West Virginia University Shared Research Facilities. Figure 1

One way to increase the value of renewable energy is to use a high efficiency reversible solid oxide fuel cell (SOFC) as an energy storage device. The utilization of SOFC for distributed generation (DG) requires the development of inverters that convert variable DC power into AC power. This paper addresses the integration of the SOFC with a power electronic inverter as a distributed generation device. The SOFC model and power inverter blocks are implemented in MATLAB/Simulink with three competing inverter control schemes. Hardware tests are required in the future and the purpose of this research is to verify a stable SOFC power system.

Polarization resistance of solid oxide fuel cell electrodes consists of resistances due to mass transfer and chemical reaction. Therefore, higher ion conductivity, electron conductivity, and gas diffusivity and larger triple-phase boundary (TPB) density lead to lower polarization resistance. To increase effective conductivities and diffusivity, tortuosity factors in each mass-transfer path should be reduced. In this study, magnetic alignment method is developed to align the mass-transfer paths in the electrode microstructure. Since Ni as an electron-conducting material in anode has high magnetic permeability, the particles are polarized and aligned by a magnetic field. Therefore, the tortuosity factors can be reduced. In addition, this Ni alignment is expected to reduce the tortuosity factors of yttria-stabilized zirconia (YSZ) and pore phases as well. However, there is a risk for a decrease in TPB density. The effect of magnetic field on resultant microstructure and polarization resistance of Ni-YSZ anode are investigated by impedance measurement of anode symmetrical cells and by reconstruction of three-dimensional microstructure. The tortuosity factors of Ni and YSZ decreased and TPB density decreased by the magnetic field. As a result, the polarization resistance of anode was kept nearly unchanged. The effect of reducing Ni volume fraction is also investigated.

Solid Oxide Fuel Cells (SOFCs) represent one of the most promising technologies for clean and efficient energy conversion due to their high efficiency and fuel flexibility [1]. However, carbon deposition, which can occur due to the reaction of hydrocarbons in the fuel within the anode, leads to significant reduction of durability. Understanding the mechanisms of carbon-induced degradation is critical for improving the long-term stability and performance of SOFCs. Currently, some studies have conducted experimental tests on the microstructure of anode under carbon deposition [2,3] or simulated the deformation of electrode materials under long-term operation [4-7], but there is still a lack of microstructure simulation considering carbon deposition reaction kinetics.In this study, we employed a phase-field modeling (PFM) approach to investigate the carbon evolution in the nickel-based anode and combined it with a one-dimensional transient elementary reaction kinetic model. The PFM model incorporates a set of coupled partial differential equations, which describe the growth and diffusion of carbon species in the anode material. The PFM model accounts for the interactions between the carbon and Ni-YSZ crystal grains, using a free energy functional that includes the bulk free energy and gradient energy. The time evolution of the system is governed by the time-dependent Ginzburg-Landau equation and Cahn-Hilliard equations. The kinetic model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure and the charge and mass transport processes. The carbon deposition source term is calculated by the heterogeneous elementary chemical reactions using methane and water as fuels. Then to ensure the accuracy and reliability, the model is validated by experimental I-V curves. After validation, the size and distribution of carbon, the porosity of the anode, and the three phase boundary area can be analyzed under different temperatures and fuel compositions. This study provides valuable insights into the mechanisms of carbon-induced degradation in SOFCs and offers a predictive tool for optimizing operating conditions to enhance the long-term stability of SOFCs.

Steady-state and dynamic models of solid oxide fuel cells based on Satin Bowerbird Optimizer

Solid oxide fuel cell (SOFC) has excellent fuel flexibility for various fuels. Despite some drawbacks like storage and transportation, hydrogen stands up as the best fuel for SOFC. Hydrogen fuel is diluted non-reactive gas species before it is supplied to the SOFC. In this study, a quasi-three-dimensional SOFC model with real microstructure is used to analyse the effect of the diluted fuel mixture. The hydrogen fuel is diluted with nitrogen and a small amount of steam. The mole amount of hydrogen within fuel mixtures is kept constant. On the other hand, the air that is supplied to the air channel of the SOFC remains unchanged. It is found that the cell that is supplied with the highest concentration of hydrogen has the highest performance due to its high partial pressure of hydrogen within the fuel mixture. Such a high partial pressure promotes a low anode concentration loss. Also, the cell that is supplied with a low hydrogen concentration is unable to benefit from its high average cell temperature as its performance is drained by the low partial pressure of hydrogen within the fuel mixture.

SummaryA design study was undertaken of a 100 kW natural gas solid oxide fuel cell (SOFC)/gas turbine (GT) hybrid system to evaluate the impacts of the reforming process under a broad range of SOFC fuel utilizations. An equilibrium reformer model and a one‐dimensional SOFC model are employed to perform system study for this hybrid, while balance of plant model is built in Ebsion to simulate the associated performance of GT cycle. Fifty design cases with varied external fuel reforming temperatures are analyzed based on different SOFC fuel utilization levels. With the decrease of reforming temperature, optimal fuel utilization in terms of efficiency shift from 90% with external reforming to 60% with internal reforming. Highest efficiency up to 74% was achieved with internal reforming, but this came with 1275 K cathode inlet air temperature and 1673 K turbine inlet temperature, which no current fuel cell and few GTs can tolerate. High fuel pre‐reforming rates provided a higher design flexibility and showed opportunities of efficiency improvement with appropriate thermal integration strategy. And the feasibility of achieving high efficiencies in the hybrid system with thermally integrated external reforming will be explored in our future work.Novelty StatementBoth fuel reforming process and fuel utilization could affect the heat and energy balance in the hybrid gas solid oxide fuel cell (SOFC)‐gas turbine (GT) system. However, the optimal design condition considering different fuel reforming approaches and SOFC fuel utilization levels was not determined in the literature. In addition, appropriate integration strategies, used to balance the heat and power between the two subsystems (SOFC and GT), are imperative under different fuel reforming approaches and SOFC fuel utilization levels. But, the feasibility of those thermal integration strategies has not been examined in existing studies. This work studied the coupling effects of SOFC fuel utilization and fuel reforming process on system performance of a natural gas hybrid SOFC/GT cycle. Highest efficiency up to 74% was achieved with internal reforming, but this came with 1275 K cathode inlet air temperature and 1673 K turbine inlet temperature, which no current fuel cell and few GTs can tolerate. High fuel pre‐reforming rates provided a higher design flexibility and showed opportunities of efficiency improvement with appropriate thermal integration strategy.

The increase of DG penetration in the distribution networks makes more and more interesting the investigation of security issues which are typical of the large transmission grids (transient stability, voltage stability and small signal stability) as well as the study of the DG responses to load changes in the grid. This paper presents the model of a Solid Oxide Fuel Cell (SOFC) dedicated to perform dynamic simulations on MV distribution networks. In particular in the present paper transient stability and load following issues are tackled. The first part of the paper is aimed at describing the model of the SOFC which is then used in the test system. As also a gas turbine is inserted into the test system, a brief look at the gas turbine model is mandatory. The aforementioned models include both the slow dynamics (GT prime mover, electrochemical system time constants for SOFC) necessary to study the DG response to load variations and the fast dynamics (e.g the power converter control and protection systems for SOFCs) necessary to study the transient stability related issues. The results of the analysis (carried out on a test MV distribution network) are reported and some conclusions are drawn.