Numerical modeling and simulation of PEM fuel cells: Progress and perspective

This paper provides a comprehensive review on the research and development in multi-scale numerical modeling and simulation of PEM fuel cells. An overview of recent progress in PEM fuel cell modeling has been provided. Fundamental transport phenomena in PEM fuel cells and the corresponding mathematical formulation of macroscale models are analyzed. Various important issues in PEM fuel cell modeling and simulation are examined in detail, including fluid flow and species transport, electron and proton transport, heat transfer and thermal management, liquid water transport and water management, transient response behaviors, and cold-start processes. Key areas for further improvements have also been discussed.

Synthesis of Platinum Nanoparticles Modified with Nafion and the Application in PEM Fuel Cell

Nafion modified Pt nano-particles with size about 4nm were synthesized.The modified particles were absorbed on the surface of carbon nanotubes and used as electro-catalysts for proton exchange membrane fuel cell. Due to the plentiful proton channels provided by the modifying Nafion ionomers, the single fuel cell with the modified Pt catalyst has a promised performance. The output was 0.282W/cm2 with Pt loading of 0.1mg/cm2, better than that of unmodified one, which was 0.273W/cm2 with Pt loading of 0.11mg/cm2.

Modeling and identification of a PEM fuel cell humidification system

A theoretical model of a humidifier of proton exchange membrane （PEM） fuel cell systems is developed and analyzed first in this paper. The model shows that there exists a strong nonlinearity in the system. Then, the system is identified using a wavelet networks method. To avoid the curse-of-dimensionality problem, a class of wavelet networks proposed by Billings is employed. The experimental data acquired from the test bench are used for identification. The one-step-ahead predictions and the five-step-ahead predictions are compared with the real measurements, respectively. It shows that the identified model can effectively describe the real system.

Optimization study of a PEM fuel cell performance using 3D multi-phase computational fluid dynamics model

An optimization study using a comprehensive 3D, multi-phase, non-isothermal model of a PEM (proton exchange membrane) fuel cell that incorporates significant physical processes and key parameters affecting fuel cell performance is pre-sented and discussed in detail. The model accounts for both gas and liquid phase in the same computational domain, and thus allows for the implementation of phase change inside the gas diffusion layers. The model includes the transport of gaseous species, liquid water, protons, energy, and water dissolved in the ion-conducting polymer. Water is assumed to be exchanged among three phases: liquid, vapour, and dissolved, with equilibrium among these phases being assumed. This model also takes into account convection and diffusion of different species in the channels as well as in the porous gas diffusion layer, heat transfer in the solids as well as in the gases, and electrochemical reactions. The results showed that the present multi-phase model is capable of iden-tifying important parameters for the wetting behaviour of the gas diffusion layers and can be used to identify conditions that might lead to the onset of pore plugging, which has a detrimental effect on the fuel cell performance. This model is used to study the effects of several operating, design, and material parameters on fuel cell performance. Detailed analyses of the fuel cell per-formance under various operating conditions have been conducted and examined.

Environmental Impact of High Altitudes on the Operation of PEM Fuel Cell Based UAS

Fuel cell is a device that converts the chemical energy in the reactants into the electrical energy after steps of sequential electrochemical processes with no significant impact on the environment. For high altitude long endurance (HALE) of unmanned aircraft system (UAS) where fuel cell operates as a prime source of power, the operation and performance of a PEM fuel cell at different level of altitudes is vitally important. In this paper, the impact of direct using extracted air from high altitudes atmosphere in order to feed the stack is investigated, and the governing equations of the supplied air and oxygen to the PEM fuel cell stack are developed. The impact of high altitudes upon the operation and the consumption of air are determined in order to maintain certain level of delivered power to the load. Also the implications associated with operating the PEM fuel cell stack at high altitudes and different technical solutions are proposed. Various modes of Integral, Proportional-Integral, and Proportional-Integral-Derivative controller are introduced and examined for different time setting responses in order to determine the most adequate trade-off choice between fast response and reactants consumption which provides the necessary optimization of the air consumption for the developed model of PEM fuel cell used for UAS operation.

Experimental Testing and Validation of the Mathematical Model for a Self-Humidifying PEM Fuel Cell

This paper presents an experimental testing and validation results for a zero-dimensional self-humidifying PEM (Proton Exchange Membrane) fuel cell stack. The model incorporates major electric and thermodynamic variables and parameters involved in the operation of the PEM fuel cell under different operational conditions. The mathematical equations are modelled by using Matlab-Simulink tools in order to simulate the operation of the developed model with a commercially available 1 kW Horizon (H-1000) PEM fuel cell stack, which is used for the purposes of model validation and tuning of the developed model. The model is mathematically modelled and presented in the recent published work of authors. The observations from model simulations provide sufficient evidence and support to the results and observations obtained from testing 1 kW Horizon (H-1000) PEM fuel cell stack used in this research. The developed model can be used as a generic model and simulation platform for a self-humidifying PEM fuel cell with an output power varying from 50 W to 1 kW, with extrapolation to higher powers is also possible.

Dynamic Analysis of a Stand Alone Operation of PEM Fuel Cell System

In this paper, the dynamic mathematical model of a proton exchange membrane (PEM) fuel cell is presented. Dynamic performance of a PEM fuel cell system by experimental and simulation using matlab/simulink is investigated. The V-I load characteristics of a 1.2 kW PEM fuel cell are presented. Result shows that the starting current of the PEM fuel cell operated at rated load reaches to approximately twice of its rated current in just less than 0.015 second before it reached to its steady state condition. Step change load responses of this PEM fuel cell were experimented and simulated. It was found out, from the results obtained, that PEM fuel cell had a very fast response to load changes. Moreover, results show that the experimental and the result computed by using the simulation of the model are very close to each other which validates the model. Hence, this model could be used to implement a controller design in order to come up with an optimal and efficient operation of PEM fuel cell. Based also on the results, a suitable power conditioning can be constructed and designed for safe and reliable operation of PEM fuel cell especially in integrating and connecting it to a hybrid wind/PV distributed generation system.

Effect of Terminal Design and Bipolar Plate Material on PEM Fuel Cell Performance

Bipolar plates perform as current conductors between cells, provide conduits for reactant gases, facilitate water and thermal management through the cells, and constitute the backbone of a fuel cell stack. Currently, commercial bipolar plates are made of graphite composite because of its relatively low interfacial contact resistance (ICR) and high corrosion resistance. However, graphite composite’s manufacturability, permeability, and durability of shock and vibration are unfavorable in comparison to metals. Therefore, metals have been considered as a replacement material for graphite composite bipolar plates. The main objective of this study is to evaluate the effect of terminal connection design and bipolar plate material on PEM fuel cell overall performance. The study has indicated that single cell performance can be improved by combining terminals into metallic bipolar plates. This terminal design reduces the internal cell resistance and eliminates the need for additional terminal plates. The improved single cell performance by 18% and the increased savings in hydrogen consumption by 15% at the current density of 0.30 A/cm2 was attributed to the robust metal to metal contact between the terminal and the metallic bipolar plates. However, connecting metal terminal directly into graphite bipolar plates did not exhibit similar improvement in the performance of graphite fuel cells because of their brittleness that could have caused damage in the plates and poor contacts.

Micro PEM Fuel Cells and Stacks

1 Results The effects of different operating parameters on micro proton exchange membrane (PEM) fuel cell performance were experimentally studied for three different flow field configurations (interdigitated,mesh,and serpentine).Experiments with different cell operating temperatures and different backpressures on the H2 flow channels,as well as various combinations of these parameters,have been conducted for three different flow geometries.The micro PEM fuel cells were designed and fabricated in-house t...

Optimization of a serpentine flow field with variable channel heights and widths for PEM fuel cells

The present study proposes a modified serpentine flow field design in which the channel heights vary along each straight flow path to enhance reactant transport and liquid water removal. An optimization approach, combining a simplified conjugate-gradient method (inverse solver) and a three-dimensional, two-phase, non-isothermal fuel cell model (direct solver), has been developed to optimize the key geometric parameters. The optimal design has tapered channels for channels 1, 3 and 4 and increasing heights for channels 2 and 5 with the flow widths first increasing and then decreasing. The optimal channel heights and widths enhance the efficiency by 22.51% compared with the basic design having all heights and widths of 1 mm. The diverging channels have a greater impact on cell performance than fine adjustments of the channel widths for the present simulation conditions. The channel heights have more effect on the sub-rib convection, while the channel widths affect the uniformity of the fuel delivery more. The reduced channel heights of channels 2–4 significantly enhance the sub-rib convection to effectively transport oxygen to and liquid water out of the diffusion layer. The final diverging channel prevents significant leakage of fuel to the outlet via sub-rib convection.

Modeling and Experimental Study of PEM Fuel Cell Transient Response for Automotive Applications

This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane （PEM） fuel cell stack to step changes in load, which are charactedstic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and expedment are based on a low pressure 5 kW proton exchange membrane fuel cell （PEMFC） stack, which is similar to those used in several of Tsinghua＇s fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008.

Performance Characteristics of an Irreversible Proton Exchange Membrane (PEM) Fuel Cell

A model of an irreversible proton exchange membrane (PEM) fuel cell working at steady-state was established, in which overpotentials, internal currents, and crossover losses were taken into account. The expressions of some key parameters of the fuel cell were derived from the point of electrochemistry and thermodynamics. Based on the irreversible model of the PEM fuel cell, the influence of multi-irreversibilities on fuel cell performance were characterized and compared systematically. The general performance characteristic curves were generated. Moreover, when the electrical circuit was closed with a load in it, the relations between the load resistance and power output density and efficiency were analyzed. The results provide a theoretical basis for both the operation and optimal design of real PEM fuel cells.

Fluorinated bimetallic nanoparticles decorated carbon nanofibers as highly active and durable oxygen electrocatalyst for fuel cells

The low activity and durability are still the critical barriers for non-precious metal electrocatalyst,mainly involving M-N/C(M=Fe,Co,Mn et al),applied in fuel cell.Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms.However,this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance.Here we create novel fluorinated iron(Fe)and cobalt(Co)bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers(CNFs)for oxygen reduction reaction(ORR).The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 m V in 0.1 M HCl O_(4)and 1.6 times power density improvement for the proton exchange membrane fuel cell device.Importantly,the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts,which leads to an ultra-stable electrocatalyst.The fuel cell voltage can keep stable even after 110 h,instead of the continuingly decrease in the traditional M-N/C.

Hybrid dynamic model of polymer electrolyte membrane fuel cell stack using variable neural network

The polymer electrolyte membrane（PEM） fuel cell has been regarded as a potential alternative power source,and a model is necessary for its design,control and power management.A hybrid dynamic model of PEM fuel cell,which combines the advantages of mechanism model and black-box model,is proposed in this paper.To improve the performance,the static neural network and variable neural network are used to build the black-box model.The static neural network can significantly improve the static performance of the hybrid model,and the variable neural network makes the hybrid dynamic model predict the real PEM fuel cell behavior with required accuracy.Finally,the hybrid dynamic model is validated with a 500 W PEM fuel cell.The static and transient experiment results show that the hybrid dynamic model can predict the behavior of the fuel cell stack accurately and therefore can be effectively utilized in practical application.

光伏-PEM储氢系统建模与仿真

光伏发电存在间歇性的缺点,需要一个可持续的储能系统来满足需求。介绍光伏-PEM(质子交换膜)储氢系统,将电能转化为氢气储存,后期再通过PEM燃料电池将氢气转化为电能。该系统包含光伏发电系统、PEM制氢电解槽以及燃料电池等,通过电解水产生氢气,氢气在高压下储存在压缩储罐中以备后用,后期系统有需要时,氢气将通过PEM燃料电池重新转化为电能。光伏发电系统的输出电流由PI控制器控制,以稳定电解槽的输入电流。对于光伏-PEM储氢系统,主要问题是对天气条件的依赖。通过系统建模来模拟光伏-PEM储氢系统的运行过程,评估与太阳能光伏输出电流相关的光照强度对氢气生产、氢气储存以及后期氢气再电气化的影响,为后续有助于缓解与太阳能、风力发电和其他间歇性发电相关的储能问题奠定基础。

Iron and Nitrogen containing Carbon Catalysts with Enhanced Activity for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

Iron and nitrogen containing carbon catalysts were prepared by the pyrolysis of iron (III) tetramethoxyphenylporphyrin complex adsorbed on as-received as well as nitric acid treated carbon black and employed them as oxygen reduction electrodes for hydrogen-oxygen PEM fuel cells. The influence of carbon surface functional groups on the dispersion of active species and electrocatalytic performance is investigated using electron microscopic and electrochemical techniques. The existence of quinone functional groups on the nitric acid treated carbon was evident from X-ray photoelectron spectroscopy and cyclic voltammetry. Rotating disk electrode voltammetry results affirmed the good electrocatalytic activity and stability of pyrolyzed macrocyclic complex adsorbed on nitric acid treated carbon compared to that of as-received carbon. This is ascribed to the greater number of Fe/N active species as well as good dispersion of metal clusters over nitric acid treated carbon support. Fuel cell tests depicted the comparable performance of pyrolyzed complex adsorbed on nitric acid treated carbon with commercial Pt/C at 353 K. Durability measurements performed under fuel cell operating conditions for 120 h indicate the good stability of the catalysts.