Polymer Electrolyte Membrane Fuel Cell Stack Research Articles

A parametric study on the performance requirements of key fuel cell components for the realization of high-power automotive fuel cells

This study examined the performance limitations of polymer electrolyte membrane fuel cells (PEMFC) for high power operations. The effects of improving electron, heat, and oxygen transport within a PEMFC on the cell performance were investigated using a three-dimensional, multiscale, two-phase PEMFC model. For more realistic PEMFC simulations at high current densities, the model newly accounts for anisotropic electron and heat transport in porous components of the membrane electrode assembly (MEA) and the non-uniform MEA compression/deformation occurring during PEMFC stack assembly. The simulations revealed improved transport properties that can be realized by optimizing the component material and design, and the degree of performance improvement was examined for a wide range of operating current densities up to 3.0 A/cm2. The simulations showed that improving the through-plane electronic conductivity and thermal conductivity of MEA components is critical for achieving high-power PEMFC performance. By contrast, the properties of the cathode catalyst layer, such as the Pt particle size and oxygen permeation rate through the ionomer film, are relatively less important under high current density PEMFC operations.

Physically Motivated Water Modeling in Control-Oriented Polymer Electrolyte Membrane Fuel Cell Stack Models

Polymer electrolyte membrane fuel cells (PEMFCs) are prone to membrane dehydration and liquid water flooding, negatively impacting their performance and lifetime. Therefore, PEMFCs require appropriate water management, which makes accurate water modeling indispensable. Unfortunately, available control-oriented models only replicate individual water-related aspects or use oversimplistic approximations. This paper resolves this challenge by proposing, for the first time, a control-oriented PEMFC stack model focusing on physically motivated water modeling, which covers phase change, liquid water removal, membrane water uptake, and water flooding effects on the electrochemical reaction. Parametrizing the resulting model with measurement data yielded the fitted model. The parameterized model delivers valuable insight into the water mechanisms, which were thoroughly analyzed. In summary, the proposed model enables the derivation of advanced control strategies for efficient water management and mitigation of the degradation phenomena of PEMFCs. Additionally, the model provides the required accuracy for control applications while maintaining the necessary computational efficiency.

Quantitative analysis on cold start process of a PEMFC stack with intake manifold

To systematically explore the low-temperature operating characteristics of polymer electrolyte membrane fuel cell (PEMFC) stack, a three-dimensional PEMFC stack model with intake manifold is developed in this study. The characteristics of different cold start modes in the stack are compared and analyzed. The distribution and transmission characteristics of water, ice, and heat in each cell of the stack are analyzed in detail. The location of water accumulation in each cell of the stack is also explored. Finally, finite difference sensitivity is calculated for the cumulated charge transfer density to quantify the effects of operating parameters on the cold start process at low temperature. And how these parameters affect the operation of the PEMFC stack at low temperature is investigated. The results show that inconsistency exists in stack operation due to the position particularity of the intermediate cell. Irreversible heat is the main heat source for the cold start of the stack, and the cathode catalyst layer is the main heat-generating component. The heat production proportion of cathode catalyst layer can reach 90%, which decreases with the increment of current density and the running time, especially for the edge cell. The initial ionomer water content is most sensitive to the cold start process of the stack, followed by the porosity of cathode catalyst layer. These parameters are sensitive to the cold start process mainly because of the change in volumetric exchange current density and oxygen concentration.

Optimal Values of Unknown Parameters of Polymer Electrolyte Membrane Fuel Cells Using Improved Chaotic Electromagnetic Field Optimization

In this article, the improved chaotic electromagnetic field optimization (ICEFO) algorithm is adopted to generate the optimal values of unknown parameters of fuel cells (FCs). The mathematical model of polymer electrolyte membrane FC (PEMFC) considers nonlinear and complex optimization problems with different control variables. The sum of squared error between the measured and computed stack voltages is considered as the main objective function. The performance of the ICEFO algorithm is tested on three PEMFC stacks. Moreover, sensitivity and statistical measures are presented to confirm the reliability and accuracy of ICEFO. In addition, the effect of changing the cell temperature and reactants pressures is studied for more validation of ICEFO. Furthermore, the results obtained by ICEFO are competitive compared with other optimization methods. These results confirm the effectiveness of ICEFO in solving the optimization problem of PEMFC parameter estimation. Finally, based on the optimization results a Simulink model for PEMFC is developed to examine the dynamic performance of the PEMFCs.

Investigation on Mechanical Properties of a Carbon Paper Gas Diffusion Layer through a 3-D Nonlinear and Orthotropic Constitutive Model

The mechanical loads that gas diffusion layers (GDLs) withstand in polymer electrolyte membrane fuel cell (PEMFC) stacks are sensitive to the assembly and working conditions. The mechanical properties of GDLs mostly depend on their composition materials, microstructural characteristics, operation conditions, etc. An accurate and comprehensive understanding of the mechanical performance of GDLs is significant for predicting the stress distribution and improving the assembly technology of PEMFC stacks. This study presented a novel 3-D nonlinear and orthotropic constitutive model of a carbon paper GDL to represent the material stiffness matrix with its compressive, tensile, and shear properties. Numerical simulations were performed based on the 3-D constitutive model, and the proposed 3-D model was validated against the experimental data reported previously. It is found that the simulation results of the 3-D constitutive model show a good agreement with the experimental results. Besides, the novel 3-D nonlinear and orthotropic model was applied in the overall stress simulation of a simplified PEMFC unit cell, compared to a conventional 3-D linear and isotropic model, and the simulation results of the two models show a significant difference.

Optimal operating conditions of PEM fuel cells in commercial aircraft

This work investigates the integration of polymer electrolyte membrane fuel cells (PEMFC) into recently proposed hydrogen aircraft concepts. Based on a numerical optimization of the stack's operating conditions, the interrelated aspects of efficiency and system mass are explored. A novel 1D two-phase PEMFC stack model is developed that captures water management effects in detail and yet features sufficiently low computational cost to be used for system-level optimization. The stack model is validated for a wide range of temperatures, current densities and oxygen concentrations. In combination with auxiliary component models, it can relate the effects of the investigated parameters on cell-level water management to system-level effects. This allows for an improved understanding of the underlying design tradeoffs, particularly regarding pressurized operation and stack oversizing. The results show that the conditions that maximize the overall system efficiency for a given flight phase deviate significantly from those that merely maximize stack efficiency.

Electro-Thermal Characteristics of Hybrid TiO2-SiO2 Nanofluid Coolants in An Electrically-Active System

Thermal management in an electrically-active system is a challenging engineering branch due to the critical requirement for rapid cooling rates with inhibition of electrical discharge. A Polymer Electrolyte Membrane Fuel Cell (PEMFC) is an example of a system that needs both conditions to be critically fulfilled. The use of conventional deionized water with low electrical conductivity as the cooling fluid ensures insignificant electrical potential losses but large thermal capacities can only be achieved with a significant penalty to the PEMFC system size. Formulation of nanofluid coolants has been highly successful for systems working under normal environments, but research towards new nanofluid coolants for active electrical systems are relatively new. This paper reports a fundamental investigation on the electrical and thermal behaviors of a hybrid 1%v TiO2-SiO2 (at 50:50 ratio) nanofluid dispersed in 60:40 water/ethylene glycol solution. A test bench consisting of a heated rectangular channel combined with continuous electrical supply at 0.7 V and 3 A nominal current was developed to simulate the operating conditions of a PEMFC stack cooling. The test variables are the heater temperature and Reynolds number (300 to 700) of the coolants. The cooling profiles and changes in electrical properties of the system and coolants were analyzed. Significant increase in cooling rates were achieved by the hybrid nanofluids (200% to 250%) compared to water and water/ethylene glycol coolants. The electrical analysis indicates that the power drop is low for water and water/ethylene glycol but drops rapidly in an exponential profile (between 15% to 45%) which also leads to a visible increase in the electrical conductivity of the nanofluids coolants. As such, further research is needed to reduce the apparent electrical discharge problem before a suitable nanofluid coolant can be developed for electrically-active systems.

Effect of stacking pressure on the performance of polymer electrolyte membrane fuel cell with various channel types

Polymer electrolyte membrane fuel cell (PEMFC) stacks are assembled via the sequential stacking of a number of PEMFC unit cells. In such a process, stacking pressure is applied to the PEMFC stack. This compression pressure causes a change in mass transport and electrical conduction characteristics. In this paper, various stacking pressures were applied to three types of PEMFC unit cells with serpentine, parallel, and interdigitated cathode channels to understand the effect of stacking pressure on PEMFC performance. Numerical analyses were conducted with a validated 3-D PEMFC model. Deformation of the gas diffusion layer (GDL) by compression was not influenced by the channel type. However, the results of the electrochemical simulation showed different influence of stacking pressure depending on the operating voltage and cathode channel type. To improve PEMFC performance, it was concluded that the stacking pressure should be determined by considering the channel type and operating voltage.

Optimal parameter estimation of polymer electrolyte membrane fuel cells model with chaos embedded particle swarm optimization

Polymer electrolyte membrane fuel cells (PEMFC) are generally preferred in engineering applications due to their energy conversion efficiency, high power density, and low operating temperatures. In recent years, it has come to the fore in electric vehicles and unmanned aerial vehicle applications, which have critical and strategic importance. However, researchers use fuel cells in many different applied-theoretical studies. The models they use to increase the accuracy of these studies should be very similar to the real PEMFC. Therefore, in this paper, chaos embedded particle swarm optimization algorithm (CEPSO) and a new objective function are proposed for the first time in the literature to find the unknown parameters of PEMFC heaps more realistically. Three commercial types of PEMFCs stack namely 250 W Stack, BCS-500 W, and Nedstack PS6, which are commonly investigated in the literature, were numerically simulated to show the effectiveness of the proposes for parameter determining. The success of the suggestions is shown by the results obtained.

Design and Analysis of an Innovative Dead-end Cascade-type PEMFC Stack at Different Orientations

In this paper, the design and experimental study of a 4-cells cascade-type polymer electrolyte membrane (PEM) fuel cell stack with integrated humidifiers and water separators are presented. The PEM fuel cell stack is subdivided into two stages to minimize the quantity of exhaust gases during operation. A dead-end condition is applied for both cathode and anode sides of the PEM fuel cell stack. In a dead-end mode, the end-stage is designed to entirely use the reactant gases in the operation. Periodical purging is utilized to remove the accumulated water or impurities from the cascade-type PEM fuel cell stack. Comparison of cascade-type PEM fuel cell stack operation in a dead-end mode with a flow-through mode is performed. Results revealed that integrating humidifiers and water separators with the stack improved the volume power density of the PEM fuel cell stack. Moreover, since more liquid water was produced on the cathode side, the fluctuation of purge cell voltage of the cathode side is higher than that of the anode side. In addition, a technique is applied to control the pressure fluctuation of both sides of the PEM fuel cell.

Startup and Shutdown Study Applied in Polymer Electrolyte Membrane Fuel Cell System Operation

Automotive polymer electrolyte membrane (PEM) fuel cells (FC) have been increasingly under development, due to their ability to provide extended vehicle driving ranges at zero emission. However, PEM fuel cells still face several challenges, such as durability and cost. The lifetime of the PEM fuel cell stacks is determined by the durability of materials under fuel cell operation, in which catalyst, membrane and ionomer are exposed to strongly acidic and oxidizing conditions at elevated temperatures. In addition, the stack lifetime is affected by various operational modes and hydration conditions experienced through drive cycles, idling conditions and startup (SU) / shutdown (SD) cycles.1 System operation strategy can mitigate the stress to the materials and improve the lifetime of fuel cell stacks.This study investigated several SUSD cycles with a PtCo based membrane electrode assembly (MEA) in single cell testing. The schematics of SUSD cycles are shown in Figure 1. In general, a SUSD cycle includes four parts: FC operation, shutdown, soak, and startup. Figure 1(a) is an air-SUSD cycle, which represents a long term shutdown of the vehicle, when air penetrates into the anode. During startup, when hydrogen (H2) is supplied to the anode, there will be an air-hydrogen front at the anode, which causes substantial carbon corrosion and platinum (Pt) dissolution to occur on the cathode. Thus, in accelerated air-SUSD cycles, during the shutdown, air is introduced to the anode and the cell voltage drops to zero within a second. Then, the cell is allowed to soak under air/air for anode/cathode for 60 seconds. After the soak process, during SU, air supply to the anode is stopped and hydrogen is supplied to the anode. In order to improve the SUSD durability of PEM fuel cells in FC vehicles, hydrogen protection (H2-SUSD) has been proposed.2 Figure 2(b) presents a H2-SUSD cycle. In the soak portion of the cycle, the O2 in the cathode is consumed by the H2 permeated from the anode, when the cell voltage drops to zero slowly. At higher temperature, the voltage drop is faster. The H2-SUSD process reduces the development of loop currents within a cell that are associated with high half-cell potential reactions. Because high half-cell potentials are mostly avoided, the H2-SUSD suppresses severe carbon corrosion and Pt dissolution that are observed in air-SUSD cycles. However, we still observe carbon corrosion happening in H2-SUSD process, which is confirmed with catalyst layer failure analysis results. In order to prevent this carbon corrosion, in H2-SUSD, after shutdown, a small load is drawn to consume O2 at the cathode quickly and improve the H2 protection effect as shown in Figure 1(c). These SUSD processes are studied at different temperatures as well. For diagnostics, the voltage degradation at 0.02 A/cm2 and 1.2 A/cm2 and ECSA losses are recorded either at 100 cycle intervals for air-SUSD and 500 cycle intervals for H2-SUSD. Our results show that H2-SUSD with a load preserves the cell performance greatly. The MEA degradation results in these SUSD cycles provide a reference for the FC system team to develop automotive SUSD operation strategy, for example, to determine the minimum H2-protection time for the FC system operation. Y. C. Park, K. Kakinuma, M. Uchida, D. A. Tryk, T. Kamino, H. Uchida, and M. Watanabe, Electrochimica Acta, 91, 195 (2013).Y. Yamashita, S. Itami, J. Takano, K. Kakinuma, H. Uchida, M. Watanabe, A. Iiyama, and M. Uchida, J. Electrochem. Soc., 164 (4), F181 (2017). Figure 1

Adaptive Control of Fuel Cell Converter Based on a New Hamiltonian Energy Function for Stabilizing the DC Bus in DC Microgrid Applications

DC microgrid applications include electric vehicle systems, shipboard power systems, and More Electric Aircraft (MEA), which produce power at a low voltage level. Rapid developments in hydrogen fuel cell (FC) energy have extended the applications of multi-phase parallel interleaved step-up converters in stabilizing DC bus voltage. The cascade architecture of power converters in DC microgrids may lead to large oscillation and even risks of instability given that the load converters considered as loads feature constant power load (CPL) characteristics. In this article, the output DC bus voltage stabilization and the current sharing of a multi-phase parallel interleaved FC boost converter is presented. The extended Port-Hamiltonian (pH) form has been proposed with the robust controller by adding an integrator action based on the Lyapunov−Energy function, named “Adaptive Hamiltonian PI controller”. The stability and robustness of the designed controller have been estimated by using Mathematica and Matlab/Simulink environments and successfully authenticated by performing experimental results in the laboratory. The results have been obtained using a 2.5 kW prototype FC converter (by two-phase parallel interleaved boost converters) with a dSPACE MicroLabBox platform. The FC main source system is based on a fuel reformer engine that transforms fuel methanol and water into hydrogen gas H2 to a polymer electrolyte membrane FC stack (50 V, 2.5 kW).

An Energy Consumption Model for Designing an AGV Energy Storage System with a PEMFC Stack

This article presents a methodology for building an AGV (automated guided vehicle) power supply system simulation model with a polymer electrolyte membrane fuel cell stack (PEMFC). The model focuses on selecting the correct parameters for the hybrid energy buffering system to ensure proper operating parameters of the vehicle, i.e., minimizing vehicle downtime. The AGV uses 2 × 1.18 kW electric motors and is a development version of a battery-powered vehicle in which the battery has been replaced with a hybrid power system using a 300 W PEMFC. The research and development of the new power system were initiated by the AGV manufacturer. The model-based design (MBD) methodology is used in the design and construction of a complete simulation model for the system, which consists of the fuel cell system, energy processing, a storage system, and an energy demand models. The energy demand model has been developed based on measurements from the existing AGV, and the remaining parts of the model are based on simulation models tuned to the characteristics obtained for the individual subsystems or from commonly available data. A parametric model is created with the possibility for development and determination by simulation of either the final system or from the parameters of the individual models’ elements (components of the designed system). The presented methodology can be used to develop alternative versions of the system, in particular the selection of the correct size of supercapacitors and batteries which depend on the energy demand profile and the development of the DC/DC converter and controllers. Additionally, the varying topology of the whole system was also analyzed. Minimization of downtime has been presented as one of many possible uses of the presented model.

Enhancing polymer electrolyte membrane fuel cell system diagnostics through semantic modelling

Polymer electrolyte membrane fuel cells (PEMFC) are a promising technology for economic and environmentally friendly energy production. However, they haven’t reached their full potential in the market yet as only few reliable PEMFC systems have successfully passed the prototyping face. A drawback of the current diagnostic tools is that only a select few are of high genericity, reliability and can perform efficiently on-line at the same time. Furthermore, there is only limited research identifying both PEMFC stack faults and ancillary system faults simultaneously. While none of the existing tools can be interrogated by the end-user. In this research, we develop novel artificial intelligence-based technologies to overcome these existing barriers, i.e., (i) a semantically enriched integrating schema (ontology) of the overall operation and structure of the PEMFC that allows automatic inference engines to automatically deduce fault detection; (ii) a knowledge-based, light-weight, on-line fuel cell system diagnosis (FuCSyDi) platform. FuCSyDi detects and provides the location of failures by considering only the data from the reliable sensors. Additionally, it provides the reasons underpinning any forthcoming failures and enables the end-user to interrogate the platform for further information regarding its operation and structure. Our platform is validated by performing tests against common automotive stress conditions. This innovative approach enhances the reliability of the fuel cell system diagnosis and, hence, its lifetime performance.

Electrodeposited Ni–Mo–Cr–P coatings for AISI 1020 steel bipolar plates

Metallic bipolar plates (BPPs) are potential candidates to replace the conventional graphite BPPs in polymer electrolyte membrane fuel cells (PEMFCs) because they are cost-effective and easy to manufacture. In this present work, we report on the development of Ni–Mo–Cr–P electroplated AISI 1020 steel bipolar plates as a BPP material. The microstructure and composition of the Ni–Mo–Cr–P coatings were optimized varying pH of the electrolyte bath and deposition current. Compared to bare AISI 1020 steel, the coating electroplated at pH 5.5 and a pulse-current density of 0.075 A/cm2 showed an improvement in corrosion resistance by three orders of magnitude. The corrosion current densities of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel in the simulated anodic environment is 1.05 × 10−2 and 4.95 × 10−5 A/cm2, respectively, while that in the simulated cathodic environment it is 3.7 × 10−2 and 4.58 × 10−5 A/cm2, respectively. The enhancement of corrosion resistance is due to the formation of a Mo and Cr based passive oxide layer. The interfacial contact resistance (ICR) of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel is 53.2 and 40.06 mΩ, respectively. ICR of Ni–Mo–Cr–P is lower than the bare AISI 1020 because of the semiconducting nature of the two-layered Mo-based passive oxides. Additionally, Ni–Mo–Cr–P coated AISI 1020 steel shows a higher water contact angle than bare AISI 1020 carbon steel. A single-cell PEMFC stack with Ni–Mo–Cr–P coated AISI 1020 steel BPP shows similar polarization behavior as graphite BPP. However, the performance of Ni–Mo–Cr–P coated AISI 1020 steel BPP lacks durability, and further improvement is necessary before it can be commercially implemented.

Optimal parameter estimation for PEMFC using modified monarch butterfly optimization

The present study develops a new optimization method called monarch butterfly optimization algorithm for optimal parameter estimation of the polymer electrolyte membrane fuel cell (PEMFC). After designing the proposed methodology, it is implemented to 250 MW PEMFC stack under different operating conditions to show the system efficiency and the results are compared with some state-of-the-art methods including Grass Fibrous Root Optimization Algorithm, hybrid Teaching Learning Based Optimization-Differential Evolution Algorithm, and the basic MBO algorithm. Two operational conditions in 3/5 bar and 80°C and 2.5/3 bar, 70°C are used for model verification. The main idea is to minimize the sum of square error (SSE) between the estimated and the actual data. Simulation results in the first condition give an SSE of value 7.277667729 with 9.28434e−16 SD value and in the second condition, an SSE of value 4.52810115 with 0.043581628 standard deviations has been reached as the minimum value among the other compared methods that indicate the accuracy and the robustness of the suggested method toward the analyzed methods. The algorithm also gives a convergence speed of 540 iterations and 370 iterations for conditions 1 and 2, respectively that are the fastest in the study.

Analysis of water management in PEM fuel cell stack at dead-end mode using direct visualization

Abstract Polymer electrolyte membrane fuel cells (PEMFC) have the ability to be operated with open-end and dead-end modes. At the open-end mode the extra reactants are essential for obtaining the specified current density. The removal of impurities from channels at the dead-end mode at a specific period of time is a very important issue. Water accumulation leads to the non-uniform distribution of reactant flow in individual fuel cell plate and within the fuel cell assembly, which can result in the voltage instabilities and electrodes degradation. In this work, a transparent PEMFC stack has been suggested and designed to explore water flow within the cell through direct visualization as the simplest and most reliable tool for water management studies. Design steps are explained in details within the manuscript and the performance of PEMFC stack at open-end and dead-end modes is compared. The effect of liquid water flow regime on voltage and pressure variation is investigated. The different losses at stack and single cell are compared and analyzed. In addition, an empirical correlation has been extracted for setting the purge parameters in PEM fuel cell stacks at dead-end mode which can be useful for further research works in the field of dead-end PEMFC.

Data on the thermo-fluid simulation of open-cathode fuel cell stack depending on the location of the oxidizer/cooling supply system.

The content of this paper provides simulation data of the distribution of temperature fields, and oxidizer/cooling agent (air) flows in dependence with location of the oxidizer/cooling supply system in open-cathode polymer electrolyte membrane fuel cell (PEMFC) stack. The finite element method in Solid Works Simulation and Solid Works Flow Simulation software were used for bipolar plate strength calculation and thermo-fluid simulation of PEMFC stack with forced-air convection. The simulations were carried out for two variants of the oxidizer/cooling supply system location - at the entrance to the fuel cell stack (air injection) and at the outlet of the fuel cell stack (air intake).

Recent Advances in Synthesis and Utilization of Ultra‐low Loading of Precious Metal‐based Catalysts for Fuel Cells

AbstractCost of polymer electrolyte membrane fuel cells (PEMFC) is one of the most acute setbacks delaying this technology's worldwide deployment and commercialization. Platinum, the most common and effective catalyst for the oxygen reduction reaction (ORR), is a scarce element which accounts for more than 45 % of PEMFC stack cost. One of the preferred proposed paths to substantially reduce stack costs is by dramatically lowering precious metal loading in a membrane electrode assembly (MEA) to account for up to 11.3 gPt per midsize vehicle (US‐DOE 2020 target). This Minireview surveys the latest synthetical and methodical advances in making and utilizing ultra‐low loading precious metal ORR catalyst in PEM fuel cells.

Connected evaluation of polymer electrolyte membrane fuel cell with dehydrogenation reactor of liquid organic hydrogen carrier

Recently, hydrogen energy technologies attract attention as power systems. To develop hydrogen energy systems, hydrogen storage methods with high storage density and good safety are required. Liquid organic hydrogen carrier (LOHC) is one of the novel hydrogen storage technologies. LOHC has advantages of high storage density, good safety, and easy handling. In this study, a polymer electrolyte membrane fuel cell (PEMFC) stack is operated with hydrogen released from LOHC to evaluate the feasibility of the connected operation of the PEMFC stack and LOHC dehydrogenation reactor. Dibenzyltoluene (H0-DBT) is used as a LOHC material, and the dehydrogenation of perhydro dibenzyltoluene (H18-DBT) is conducted at 240–300 °C. Released hydrogen is purified by adsorbent of activated carbon to remove impurities. However, 100–1400 ppm of methane is observed after the purification, and the PEMFC stack power is reduced from 39.4 W to 39.0 W during the operation by hydrogen dilution and physical adsorption of methane. Then, to evaluate the irreversible damage, pure hydrogen was supplied to the PEMFC stack. The stack power is recovered to 39.4 W. It is concluded that the connected operation of the LOHC dehydrogenation reactor and PEMFC stack is feasible, and the activated carbon adsorbent can be a cost-effective purification method for LOHC.