Modelling and simulation of the steady-state and dynamic behaviour of a PEM fuel cell

The performance of a fuel cell can be expressed by the voltage–load current (V–I) characteristics. In this study, two mathematical modelling for computing the steady-state and dynamic voltage–current (V–I) characteristics of PEM fuel cell stacks have been developed. For determining the humidity of the membrane in steady-state conditions, mathematical and theoretical equations are considered. This value is not an adjustable parameter. The goal of dynamic modelling is to find the response of the system against the load variations. In this research, in addition to the charge double layer phenomenon, the effects of temperature and gas flows are taken into account, then the fuel cell system is divided into three control volumes and thus a lumped-parameter model for these sub-systems is established using the mass and heat transfer equations. The proposed models are implemented in Matlab/Simulink environment. Additionally, these models were tested for the SR-12Modular PEM Generator, the Ballard Mark V FC, the BCS 500-W stack and various experimental data in open literature. They exhibit excellent agreement with other simulation and experimental results.     

A simple model of a high temperature PEM fuel cell

We develop a simple analytical model of a high temperature hydrogen fuel cell with proton exchange membrane. The model is validated against experimental results obtained in our group. The model is pseudo two dimensional, steady-state and isothermal, it accounts for the crossover of reactant gases through the membrane and it can be solved analytically. The role of the crossover is considered in detail.     

Computational model of a PEM fuel cell with serpentine gas flow channels

A three-dimensional computational fluid dynamics model of a PEM fuel cell with serpentine flow field channels is presented in this paper. This comprehensive model accounts for the major transport phenomena in a PEM fuel cell: convective and diffusive heat and mass transfer, electrode kinetics, and potential fields. A unique feature of the model is the implementation of a voltage-to-current (VTC) algorithm that solves for the potential fields and allows for the computation of the local activation overpotential. The coupling of the local activation overpotential distribution and reactant concentration makes it possible to predict the local current density distribution more accurately. The simulation results reveal current distribution patterns that are significantly different from those obtained in studies assuming constant surface overpotential. Whereas the predicted distributions at high load show current density maxima under the gas channel area, low load simulations exhibit local current maxima under the collector plate land areas.     

A systematic approach for matching simulated and experimental polarization curves for a PEM fuel cell

Matching simulated and experimental polarization curves is an essential step in the modelling of polymer electrolyte membrane (PEM) fuel cells, but the numerical values of many input parameters like exchange current densities, charge transfer coefficients, protonic conduction coefficient and water removal coefficient are hard to be found experimentally. In this paper, the influence of these input parameters on the performance of PEM fuel cells has been investigated using the ANSYS PEM Fuel Cell Module. The simulation results show how the exchange current densities and charge transfer coefficients influence the activation losses; membrane resistance and contact resistance between the different components of a fuel cell contribute to the ohmic losses; and the coefficient of liquid water removal affects the concentration losses. A systematic procedure to match a simulated polarization curve with an experimental curve is presented and illustrated by application to an experimental PEM fuel cell with 5 cm² active area.     

Parametric sensitivity analysis of PEM fuel cell electrochemical Model

In order to obtain an adequate PEM Fuel Cell model, it is necessary to define the values for a specific group of modeling parameters. The disagreements between the experimental and simulation results arise because of uncertainties stemming not only from the experimental measurements, but also from the modeling parameters used in the theoretical calculations. The modeling parameters were analyzed using Multi-Parametric Sensitivity Analysis (MPSA). This paper presents a sensitivity investigation of PEMFC electrochemical models and aims to determine the relative importance of each parameter on the modeling results. A computer program is written in Dev-cpp environment to calculate the sensitivity index for each parameter. As a result, the parameters were classified according to their influence in the modeling results as: insensitive, sensitive and highly sensitive. Thus it is possible to evaluate the relative importance of each parameter to the simulation accuracy. The present work benefits to understand the most effecting parameters, thus it helps the manufacturer to be more cautious in defining the exact value for them.     

Numerical simulation of mass and charge transfer for a PEM fuel cell

A three-dimensional, steady state, single phase model is developed to study the mass and charge transfer within a proton exchange membrane (PEM) fuel cell. A single set of conservation equations is used for all PEM fuel cell layers and the governing equations are solved numerically using a finite-volume-based computational fluid dynamics technique. The numerical results for the flow field, species transport and phase potential are presented for two designs, namely a PEM fuel cell with conventional and interdigitated flow fields for the reactant supply.     

Modelling CO poisoning and O2 bleeding in a PEM fuel cell anode

Fuel gas containing carbon monoxide severely degrades the performance of a polymer electrolyte membrane (PEM) fuel cell. However, CO poisoning can be mitigated by introducing oxygen into the fuel (oxygen bleeding). A mathematical PEM fuel cell model is developed that simulates both CO poisoning and oxygen bleeding, and obtains excellent agreement with published, experimental data. Modelling efforts indicate that CO adsorption and desorption follow a Temkin model. Increasing operating pressure or temperature mitigates CO poisoning, while use of reformate fuel increases the severity of the poisoning effect. Although oxygen bleeding mitigates CO poisoning, an unrecoverable performance loss exists at high current densities due to competition for reaction sites between hydrogen adsorption and the heterogeneous catalysis of CO. Copyright © 2003 John Wiley & Sons, Ltd.     

Dynamic modeling of a PEM fuel cell with temperature effects

With the aim of dynamic simulation and control, a new non-linear state-space dynamic non-isothermal polymer electrolyte membrane fuel cell (PEMFC) model is developed in this paper. This mathematical model is developed based on mass and energy equation. The present model takes in account subsequent factors as the effects of charge double layer capacitance, the geometrical capacity and the effect of temperature gradient. In this paper, the authors propose a combination of several dynamic equations to study the effect of suddenly variation of some operating parameters like load resistance, gas pressure and gas temperature input. The results are compared to those of an isothermal model. This model will be extremely functional for the best possible design and real-time control of PEMFC systems. The present model is executed in MATHCAD software and the fuel cell is symbolized by an equivalent circuit which incorporates gas diffusion layer, membrane and electrodes. The analysis results show that the main elements that influence the performance of the cell are load resistance and functioning temperature.     

Characterization and experimental results in PEM fuel cell electrical behaviour

A control oriented electrochemical static model of a proton exchange membrane fuel cell (PEMFC) stack is developed in this paper. Even though its validation is performed on a specific 7-cell PEMFC stack fed by humidified air and pure hydrogen, the methodology and fit parameters can be applied to different fuel cell systems with minor changes. The fuel cell model was developed combining theoretical considerations and semi-empirical analysis based on the experimental data. The proposed model can be successfully included into a larger dynamic subsystem to complete the power generation system.     

Transport mechanisms and performance simulation of a PEM fuel cell

A three‐dimensional, gas–liquid two‐phase flow and transport model has been developed and utilized to simulate the multi‐dimensional, multi‐phase flow and transport phenomena in both the anode and cathode sides in a proton exchange membrane (PEM) fuel cell and the cell performance with different influencing operational and geometric parameters. The simulations are presented with an emphasis on the physical insight and fundamental understanding afforded by the detailed distributions of velocity vector, oxygen concentration, water vapor concentration, liquid water concentration, water content in the PEM, net water flux per proton flux, local current density, and overpotential. Cell performances with different influencing factors are also presented and discussed. The comparison of the model prediction and experimental data shows a good agreement. Copyright © 2007 John Wiley & Sons, Ltd.     

LPV observer design for PEM fuel cell system: Application to fault detection

In this paper, the modelling of an energy generation system based on polymer electrolyte membrane fuel cell (PEMFC) system through a parameter varying approach (LPV model), that takes in to account model parameter variation with the operating point, is presented. This model has been obtained through a Jacobian linearization of the PEMFC non-linear dynamic model that was previously calibrated using real data from lab. In order to illustrate the use of the LPV model obtained its application to model-based fault detection is used. For this purposes a set of common fault scenarios, which could appear during a normal PEMFC operation, is used as case study.     

Modelling of proton exchange membrane fuel cell performance based on semi-empirical equations

Using semi-empirical equations for modeling a proton exchange membrane fuel cell is proposed for providing a tool for the design and analysis of fuel cell total systems. The focus of this study is to derive an empirical model including process variations to estimate the performance of fuel cell without extensive calculations. The model take into account not only the current density but also the process variations, such as the gas pressure, temperature, humidity, and utilization to cover operating processes, which are important factors in determining the real performance of fuel cell. The modelling results are compared well with known experimental results. The comparison shows good agreements between the modeling results and the experimental data. The model can be used to investigate the influence of process variables for design optimization of fuel cells, stacks, and complete fuel cell power system.     

Operating line analysis of fuel processors for PEM fuel cell systems

At least three different definitions of fuel processor efficiency are in widespread use in the fuel cell industry. In some instances the different definitions are qualitatively the same and differ only in their quantitative values. However, in certain limiting cases, the different efficiency definitions exhibit qualitatively different trends as system parameters are varied. In one limiting case that will be presented, the use of the wrong efficiency definition can lead a process engineer to believe that a theoretical maximum in fuel processor efficiency exists at a particular operating condition, when in fact no such efficiency optimum exists. For these reasons, the objectives of this paper are to: (1) quantitatively compare and contrast these different definitions, (2) highlight the advantages and disadvantages of each definition and (3) recommend the correct definition of fuel processor efficiency.     

Modelling water intrusion and oxygen diffusion in a reconstructed microporous layer of PEM fuel cells

The hydrophobic microporous layer (MPL) in PEM fuel cell improves water management but reduces oxygen transport. We investigate these conflict impacts using nanotomography and pore-scale modelling. The binary image of a MPL is acquired using FIB/SEM tomography. The water produced at the cathode is assumed to condense in the catalyst layer (CL), and then builds up a pressure before moving into the MPL. Water distribution in the MPL is calculated from its pore geometry, and oxygen transport through it is simulated using pore-scale models considering both bulk and Knudsen diffusions. The simulated oxygen concentration and flux at all voxels are volumetrically averaged to calculate the effective diffusion coefficients. For water flow, we found that when the MPL is too hydrophobic, water is unable to move through it and must find alternative exits. For oxygen diffusion, we found that the interaction of the bulk and Knudsen diffusions at pore scale creates an extra resistance after the volumetric average, and that the conventional dusty model substantially overestimates the effective diffusion coefficient.     

Modelling and simulation of two-chamber microbial fuel cell

Microbial fuel cells (MFCs) offer great promise for simultaneous treatment of wastewater and energy recovery. While past research has been based extensively on experimental studies, modelling and simulation remains scarce. A typical MFC shares many similarities with chemical fuel cells such as direct ascorbic acid fuel cells and direct methanol fuel cells. Therefore, an attempt is made to develop a MFC model similar to that for chemical fuel cells. By integrating biochemical reactions, Butler–Volmer expressions and mass/charge balances, a MFC model based on a two-chamber configuration is developed that simulates both steady and dynamic behaviour of a MFC, including voltage, power density, fuel concentration, and the influence of various parameters on power generation. Results show that the cathodic reaction is the most significant limiting factor of MFC performance. Periodic changes in the flow rate of fuel result in a boost of power output; this offers further insight into MFC behaviour. In addition to a MFC fuelled by acetate, the present method is also successfully extended to using artificial wastewater (solution of glucose and glutamic acid) as fuel. Since the proposed modelling method is easy to implement, it can serve as a framework for modelling other types of MFC and thereby will facilitate the development and scale-up of more efficient MFCs.     

Performance of novel bimetallic carbonyl clusters as PEM fuel cell anodes,a comparative study

This work describes the performance of novel bimetallic catalysts, prepared from ruthenium, rhodium and iridium carbonyl clusters by a thermolysis procedure in o-dichlorobenzene. The electrochemical characterization by the rotating disk electrode technique in 0.5 mol L⁻¹ H₂SO₄ showed that the Ru_xIr_y(CO)_n, Ru_xRh_y(CO)_n and Rh_xIr_y(CO)_n clusters are able to perform both the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR), even in the presence of fuel cell contaminants such as CO and methanol, respectively. These promising results led us to evaluate the new materials as electrodes in a single fuel cell, using a Fuel Cell Test System designed and built in our group. The performance results of the three bimetallic clusters as anodes in a hydrogen PEM fuel cell are presented in this work. In the tests different H₂ and O₂ gas flows were fed into the cell to determine the most adequate ratio for maximum power. In the absence of CO, the results showed that although the three bimetallic materials had a similar performance to that of platinum with low flows of both reactants, Ru_xIr_y(CO)_n showed the best electrocatalytic parameters. When the hydrogen fuel feed was contaminated with 100 ppm and 0.5% CO, the commercial platinum activity decreased considerably or was completely lost. However, while the current density of the novel materials also decreased in the presence of CO, it was significantly above that of platinum nanoparticles, the Rh_xIr_y(CO)_n and Ru_xIr_y(CO)_n catalysts showing the best performance in the presence of 100 ppm CO and 0.5% CO respectively. These results are promising in the context of PEM fuel cells using reforming hydrogen.     

Numerical simulation of water and heat transport in the cathode channel of a PEM fuel cell

Cathode channel of a PEM fuel cell is the critical domain for the transport of water and heat. In this study, a mathematical model of water and heat transport in the cathode channel is established by considering two-phase flow of water and air as well as the phase change between water and vapor. The transport process of the species of air is governed by the convection-diffusion equation. The VOSET (coupled volume-of-fluid and level set method) method is used to track the interface between air and water, and the phase equilibrium method of water and vapor is employed to calculate the mass transfer rate on the two-phase interface. The present model is validated against the results in the literature, then applied to investigate the characteristics of two-phase flow and heat transfer in the cathode channel. The results indicate that in the inlet section, water droplets experience three evolution stages: the growing stage, the coalescence stage and the generation stage of dispersed water drops. However, in the middle and outlet sections of the channel, there are only two stages: the growth of water droplets, and the formation of a water film. The mass transfer rate of phase change in the inlet section of the channel varies over time, exhibiting an initial increase, a decrease followed, and a stabilization finally, with the maximum and stable values of 1.78 × 10^?4 kg/s and 1.52 × 10^?4 kg/s for Part 1, respectively. In the middle and outlet sections, the mass transfer rate increase firstly and then keeps stable gradually. Furthermore, regarding the distribution of the temperature and vapor mass fraction in the channel, near the upper surface of the channel, the temperature and vapor mass fraction first change slightly (x < 0.03 m) and then rapidly decrease with fluctuations (x > 0.03 m). In the middle of the channel, the temperature and vapor mass fraction slowly decrease with fluctuation.     

An analysis of fluidic voltage statistical correlation for a diagnosis of PEM fuel cell flooding

The fault diagnosis is one of the most important topics on Proton Exchange Membrane Fuel Cell (PEMFC) stacks. Statistical methodologies for diagnosis are considered as one of the most relevant. This paper is dedicated to the diagnosis of flooding, using statistical methodology.     

质子交换膜燃料电池堆的热力学分析

建立了质子交换膜燃料电池(PEMFC)堆的热力学分析模型,研究了运行温度、气体分压和阳极流量等工作参数对燃料电池堆能量效率和火用效率的影响。结果表明:对气体加压,能提高热力学能效率和火用效率;温度升高时,系统性能无明显变化;阳极流量增加时,系统的热力学能效率和火用效率有所降低。     

Optimal design and operational tests of a high-temperature PEM fuel cell for a combined heat and power unit

Development of new materials for polymer electrolyte membranes has allowed increasing the operational temperature of PEM fuel cell stacks above 120 °C. The present paper summarizes the main results obtained in a research devoted to the design, fabrication and operational tests performed on a high-temperature PEMFC prototype. A 5-cell stack has been assembled with commercial Celtec P-1000 high-temperature MEAs from BASF Fuel Cells, but the rest of elements and processes have been developed at LIFTEC research facilities. The stack includes different novelties, such as the way in which reactant gases are supplied to the flowfield, the design of the flowfield geometry for both anode and cathode plates, the concept of block that eases the assembling and maintenance processes, and the heating strategy for a very fast start-up. The different procedures comprising the assembly, closing and conditioning stages are also widely described and discussed. Results obtained in the preliminary operational tests performed are very promising, and it is expected that the 30-cells HT-PEMFC stack will deliver an electric power 2.3 times larger than the one initially predicted.