scholarly journals Entropy generation analysis of a Solid Oxide Fuel Cell by Computational Fluid Dynamics: Influence of electrochemical model and its parameters

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 577-589 ◽  
Author(s):  
José Ramírez-Minguela ◽  
Juan Mendoza-Miranda ◽  
José Rodríguez-Muñoz ◽  
Vicente Pérez-García ◽  
Jorge Alfaro-Ayala ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Entropy Generation ◽  
Current Density ◽  
Solid Oxide ◽  
Entropy Generation Rate ◽  
Ohmic Loss ◽  
Oxide Fuel ◽  
Thermodynamic Irreversibility ◽  
Electrochemical Model

The aim of this paper is to evaluate numerically the effect of varying the electrochemical model and its parameters on the performance and entropy generation of a mono-block-layer build (MOLB) type geometry of a solid oxide fuel cell. Particularly, the influence of the exchange of current density, the electrical conductivity of the electrodes and the electrolyte has been studied and the prediction of the thermodynamic irreversibility by means of an entropy generation analysis is considered. The numerical analysis consider a 3-D CFD model that takes into account the mass transfer, heat transfer, species transport, and electrochemical reactions. Several numerical simulations were performed and each contribution to the local entropy generation rate was computed. The results show different trends of the current density, temperature, species, activation loss, ohmic loss, and concentration loss along the fuel cell. Also, the results show strong variations of the local and global entropy generation rates between the cases analyzed. It is possible to conclude that the fuel cell performance and the prediction of thermodynamic irreversibility can be significantly affected by the choice of the electrochemical models and its parameters, which must be carefully selected.

Entropy Generation Minimization in a Tubular Solid Oxide Fuel Cell

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Entropy Generation ◽  
Energy Equation ◽  
Solid Oxide ◽  
Geometrical Parameters ◽  
Oxide Fuel ◽  
Cell Geometry ◽  
Cell Efficiency ◽  
Entropy Generation Minimization

The aim of the paper is to investigate possible design modifications in tubular solid oxide fuel cell geometry to increase its performance. The analysis of the cell performances is conducted on the basis of the entropy generation. The use of this technique makes it possible to identify the phenomena provoking the main irreversibilities, understand their causes and propose changes in the system design and operation. The different contributions to the entropy generation are analyzed in order to develop new geometries that increase the fuel cell efficiency. To achieve this purpose, a CFD model of the cell is used. The model includes energy equation, fluid dynamics in the channels and in porous media, current transfer, chemical reactions, and electrochemistry. The geometrical parameters of the fuel cell are modified to minimize the overall entropy generation.

Performance Metrics for Solid Oxide Fuel Cell Cross-Section Design

2009 ◽  
Author(s):  
George J. Nelson ◽  
Comas Haynes ◽  
William Wepfer
Keyword(s):  
Fuel Cell ◽  
Partial Pressure ◽  
Solid Oxide Fuel Cell ◽  
Correction Factor ◽  
Current Density ◽  
Performance Metrics ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Pressure Distributions ◽  
Button Cell

Analytical models have been developed to describe the partial pressure distributions of reactants within solid oxide fuel cell (SOFC) electrodes and introduce the concept of a reactant depletion current density. These existing analytical expressions for two-dimensional reactant partial pressure distributions and the reactant depletion current density are presented in non-dimensional form. Performance metrics for SOFC electrodes are developed including a correction factor that can be applied to button-cell predictions of pressure distribution and two forms of dimensionless reactant depletion current density. Performance predictions based on these metrics are compared to numerical predictions of partial pressure and depletion current density based on a finite element solution of the dusty-gas model (DGM) within SOFC electrodes. It is shown that the pressure correction factor developed provides a reasonable prediction of interconnect geometry effects. Thus, it is presented as a modeling tool that can be applied to translate component level fidelity to cell and stack level models. The depletion current density metrics developed are used to present basic design maps for SOFC unit cell cross-sections. These dimensionless forms of the depletion current density quantify the influence of sheet resistance effects on reactant depletion and can predict the deviation from the limiting current behavior predicted using a button-cell model.

Modeling, parametric analysis and optimization of an anode-supported planar solid oxide fuel cell

2015 ◽  
Vol 229 (17) ◽  
pp. 3125-3140 ◽  
Author(s):  
Mehdi Borji ◽  
Kazem Atashkari ◽  
Nader Nariman-zadeh ◽  
Mehdi Masoumpour
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Temperature Difference ◽  
Current Density ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Multi Objective Optimization ◽  
Average Current Density ◽  
Multi Objective ◽  
Average Current

Solid oxide fuel cell is a promising tool for distributed power generation systems. This type of power system will experience different conditions during its operating life. The present study aims to simulate mathematically a direct internal reforming planar type anode supported solid oxide fuel cell considering mass and energy conservation equations along with a complete electrochemical model. Two main reactions, namely water–gas shift reaction and methane steam reforming reaction, are considered as two dominant reactions occurring in a fuel cell. Such a model may be employed to examine the effect of different operating conditions on main solid oxide fuel cell parameters, such as temperature gradients, power, and efficiency. Furthermore, using such mathematical model, a multi-objective optimization procedure can be applied to determine maximum cell efficiency and output power under constraints such as the allowable temperature difference and limited operating potential. The selected design variables are air ratio, fuel utilization, average current density, steam to carbon ratio, and pre-reforming rate of methane. It has been revealed that any increase in pre-reforming rate of methane and steam to carbon ratio of the entering fuel will lead to efficiency penalty and more uniform temperature distribution along the cell. In addition, the more average current density increases, the less electric efficiency is achieved, and on the other hand, the more temperature difference along the cell is seen. Besides, it is shown that some interesting and important relationships as useful optimal design principles involved in the performance of solid oxide fuel cells can be discovered by Pareto based multi-objective optimization of the mathematically obtained model representing their electric performance. Such important optimal principles would not have been obtained without the use of both mathematical modeling and the Pareto optimization approach.

Electrochemical and Exergetic Modeling of a Combined Heat and Power System Using Tubular Solid Oxide Fuel Cell and Mini Gas Turbine

2013 ◽  
Vol 10 (5) ◽  
Author(s):  
M. Y. Abdollahzadeh Jamalabadi
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Combined Heat And Power ◽  
Solid Oxide ◽  
Entropy Generation Rate ◽  
Oxide Fuel ◽  
Exergy Destruction ◽  
Cell Temperature ◽  
Destruction Rate

In this article, a combined heat and power (CHP) system using a solid oxide fuel cell and mini gas turbine is introduced. Since a fuel cell is the main power generating source in hybrid systems, in this investigation, complete electrochemical and thermal calculations in the fuel cell are carried out in order to obtain more accurate results. An examination of the hybrid system performance indicates that increasing of the working pressure and rate of air flow into the system, cause the cell temperature to reduce, the efficiency and the power generated by the system to diminish, and the entropy generation rate and exergy destruction rate to increase. On the other hand, increasing the flow rate of the incoming fuel, the rise in cell temperature causes the efficiency, generated power, and exergy destruction rate of the system to increase.

Optimization of the Anode Current Collector Layer Thickness for the Cathode-Supported Solid Oxide Fuel Cell

2013 ◽  
Vol 712-715 ◽  
pp. 1325-1329 ◽  
Author(s):  
Wei Kong ◽  
Shi Chuan Su ◽  
Xiang Gao ◽  
Dong Hui Zhang ◽  
Zi Dong Yu
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Layer Thickness ◽  
Current Density ◽  
High Performance ◽  
Current Collector ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Anode Current ◽  
Output Current

The influence of anode current collector layer (ACCL) thickness is studied for different ACCL porosity and different pitch width. The results shows conclusively that the output current density depends strongly on the ACCL thickness and a suitable choice of the ACCL thickness is very important for the high performance of a SOFC stack. Furthermore, the optimal ACCL thickness is found to be dependent linearly on the pitch width and the parameters for the linearity are given.

Effects of Electrode Microstructure on Intermediate Temperature Solid Oxide Fuel Cell Performance

2010 ◽  
Vol 7 (5) ◽  
Author(s):  
Edward J. Naimaster ◽  
A. K. Sleiti
Keyword(s):  
Grain Size ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Phase Boundary ◽  
Pore Size ◽  
Current Density ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Triple Phase Boundary ◽  
Microstructure Parameters

In this study, the effects of electrode microstructure and electrolyte parameters on intermediate temperature solid oxide fuel cell (ITSOFC) performance were investigated using a one-dimensional solid oxide fuel cell model from the Pacific Northwest National Laboratory (PNNL). The activation overpotential was investigated through the exchange current density term, which is dependent on the cathode activation energy, the cathode porosity, and the pore size and grain size at the cathode triple phase boundary. The cathode pore size, grain size, and porosity were not integrated in the PNNL model, therefore, an analytical solution for exchange current density from Deng and Petric (2005, “Geometric Modeling of the Triple-Phase Boundary in Solid Oxide Fuel Cells,” J. Power Sources, 140, pp. 297–303) was utilized to optimize their effects on performance. Through parametric evaluation and optimization of the electrode microstructure parameters, the activation overpotential was decreased by 29% and the overall ITSOFC maximum power density was increased by almost 400% from the benchmark PNNL case. The effects and importance of electrode microstructure parameters on ITSOFC performance were defined. Optimization of such parameters will be the key in creating viable ITSOFC systems. Although this was deemed successful for this project, future research should be focused on numerically quantifying and modeling the electrode microstructure in two- and three-dimensions for more accurate results, as the electrode microstructure may be highly multidimensional in nature.

Electrochemical Characterization and Mechanisms of Solid Oxide Fuel Cells by Electrochemical Impedance Spectroscopy Under Different Applied Voltages

2010 ◽  
Author(s):  
Li Sun ◽  
Gianfranco DiGiuseppe
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Fuel Cell ◽  
Impedance Spectroscopy ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Electrochemical Impedance ◽  
Density Measurement ◽  
Electrical Circuit ◽  
Solid Oxide ◽  
Oxide Fuel

In this paper, the behavior of an anode-supported solid oxide fuel cell is studied by using voltage-current density measurement and electrochemical impedance spectroscopy. The cell total polarization obtained from electrochemical impedance spectroscopy results is shown to be consistent with the area-specific resistance calculated from the voltage-current density curve. An electrolyte-supported solid oxide fuel cell is then used to build an equivalent electrical circuit model using reference electrodes and electrochemical impedance spectroscopy. A four-constant phase element model is proposed to analyze the anode-supported solid oxide fuel cell. The model is used to evaluate an anode-supported solid oxide fuel cell under different cell voltages. The individual resistances are also studied as a function of applied voltage, and their physical meaning is explained in terms of reaction mechanisms occurring at the cathode and anode. It is shown that some of the obtained resistances are independent of diffusion while others have both a charge transfer and diffusion component.

Oscillation Phenomenon of the Cell Performance for an Anode-Supported Solid Oxide Fuel Cell with a Low-Porosity/High-Thickness Anode Structure

2015 ◽  
Vol 656-657 ◽  
pp. 124-128 ◽  
Author(s):  
Wei Xin Kao ◽  
Tai Nan Lin ◽  
Yang Chuang Chang ◽  
Maw Chwain Lee
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Concentration Polarization ◽  
Cell Voltage ◽  
Solid Oxide ◽  
Constant Current ◽  
Oxide Fuel ◽  
Oscillation Phenomenon ◽  
Low Porosity

The anode-supported solid oxide fuel cell (SOFC) with low-porosity anode structure is fabricated and the electrochemical characteristics are investigated. The electrochemical characterization of the cell shows a periodic oscillation phenomenon of the cell voltage under the constant current density operation. The low-porosity anode structure results in the decrease in the effective diffusion coefficient and the accumulation of water vapor. The cell voltage oscillation is mainly caused by the concentration polarization as well as the boundary migration of the reaction zone. The profound influence on the concentration polarization can be observed when the cell test is executed with operation condition of higher current density, lower hydrogen concentration, and lower hydrogen flow rate in the anode side.

A Thermo-Fluid/Electrochemical Model for Micro-SOFC

2005 ◽  
Author(s):  
Yan Ji ◽  
J. N. Chung ◽  
Kun Yuan
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Electrical Potential ◽  
Concentration Field ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Concentration Difference ◽  
Local Current Density ◽  
Local Current

In this paper, a three dimensional thermo-fluid/electro-chemical model is proposed to simulate the heat and mass transfer phenomena in a micro-geometry co-flow solid oxide fuel cell. Governing equation of mass, momentum and energy conservation are simultaneously solved. A network circuit is applied to simulate the electrical potential, ohmic losses and activation polarization. Cyclic boundary conditions are imposed at the top and bottom of the model domains, while the lateral walls were assumed adiabatic and insulation. A parametric study examines the effect of micro-channel on the temperature field, concentration field, local current density and power density. Results demonstrate that microchannels can reduce temperature or concentration difference between reaction locations and stream. The local current density is much more uniform and output voltage is also improved. Numerical simulation will be expected to help optimize the design of a micro solid oxide fuel cell.

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