Biomimetic flow fields for proton exchange membrane fuel cells: A review of design trends

Bipolar Plate design is one of the most active research fields in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) development. Bipolar Plates are key components for ensuring an appropriate water management within the cell, preventing flooding and enhancing the cell operation at high current densities. This work presents a literature review covering bipolar plate designs based on nature or biological structures such as fractals, leaves or lungs. Biological inspiration comes from the fact that fluid distribution systems found in plants and animals such as leaves, blood vessels, or lungs perform their functions (mostly the same functions that are required for bipolar plates) with a remarkable efficiency, after millions of years of natural evolution. Such biomimetic designs have been explored to date with success, but it is generally acknowledged that biomimetic designs have not yet achieved their full potential. Many biomimetic designs have been derived using computer simulation tools, in particular Computational Fluid Dynamics (CFD) so that the use of CFD is included in the review. A detailed review including performance benchmarking, time line evolution, challenges and proposals, as well as manufacturing issues is discussed.Ministerio de Ciencia, Innovación y Universidades ENE2017-91159-EXPMinisterio de Economía y Competitividad UNSE15-CE296

Transient analysis of proton electrolyte membrane fuel cells (PEMFC) at start-up and failure

A two-dimensional, transient, single-phase computational model, incorporating water transport in the membrane and the flow and transport of species in porous gas diffusion electrodes is developed to evaluate the transient performance of a PEMFC with interdigitated gas distributors. The co-flow and counter-flow of the anode and cathode reactants are discussed to address their effects on PEMFC performance and transients. The important role of water transport in the membrane on the transients is demonstrated. The membrane’s water intake or outtake determines the duration of the transients. The effect of the operating conditions on steady state and transient performances is outlined. Overshoots and undershoots are observed in the average current density, due to a step change in the cell voltage and the cathode pressure under start-up conditions. Simulation results are used to address the role of auxiliary components in the failure modes of the PEMFC

Numerical simulation of two-phase cross flow in the gas diffusion layer microstructure of proton exchange membrane fuel cells

The cross flow in the under-land gas diffusion layer (GDL) between 2 adjacent channels plays an important role on water transport in proton exchange membrane fuel cell. A 3-dimensional (3D) two-phase model that is based on volume of fluid is developed to study the liquid water-air cross flow within the GDL between 2 adjacent channels. By considering the detailed GDL microstructures, various types of air-water cross flows are investigated by 3D numerical simulation. Liquid water at 4 locations is studied, including droplets at the GDL surface and liquid at the GDL-catalyst layer interface. It is found that the water droplet at the higher-pressure channel corner is easier to be removed by cross flow compared with droplets at other locations. Large pressure difference Δp facilitates the faster water removal from the higher-pressure channel. The contact angle of the GDL fiber is the key parameter that determines the cross flow of the droplet in the higher-pressure channel. It is observed that the droplet in the higher-pressure channel is difficult to flow through the hydrophobic GDL. Numerical simulations are also performed to investigate the water emerging process from different pores of the GDL bottom. It is found that the amount of liquid water removed by cross flow mainly depends on the pore's location, and the water under the land is removed entirely into the lower-pressure channel by cross flow

Modeling and Simulation of Biologically Inspired Flow Field Designs for Proton Exchange Membrane Fuel Cells

abstract: Various biologically inspired flow field designs of the gas distributor (interconnector) have been designed and simulated. Their performance using Nafion-212 with humidified H[subscript 2] and Air at 80 °C with the ANSYS Fluent Fuel Cell module software was evaluated. Novel interdigitated designs were optimized by obeying biologically inspired branching rules. These rules allow for more mathematically formal descriptions of flow field designs, enabling relatively simple optimization. The channel to land ratio was kept equivalent between designs with typical values between 0.8 and 1.0. The pressure drop and the current density distribution were monitored for each design on both anode and cathode sides. The most promising designs are expected to exhibit lower pressure drop however, low pressure drop can also be an indication of potential water flooding at higher operating current density. A biologically inspired interdigitated design with 9 inlet channels exhibited reduced pressure drop and improved current density distribution compared to all other interdigitated designs evaluated in this study. The simulated fuel cell performance data at ambient pressure with humidified H[subscript 2] and air compares well with the experimental data using a single serpentine flow field design.The final version of this article, as published in The Open Electrochemistry Journal, can be viewed online at: https://benthamopen.com/ABSTRACT/TOELECJ-6-

Computational investigation of polymer electrolyte membrane fuel cell with nature-inspired Fibonacci spiral flow field

Polymer electrolyte membrane fuel cells (PEMFC) are promising clean energy devices. The flow field design has crucial role in PEMFC performance for effective distribution of reactants and removal of products. Several nature-inspired flow field designs have recently been proposed in the literature. Common characteristics of these designs were sudden changes in the flow direction through sharp bends and flow field geometries restrained to areas having corners. In this thesis, Fibonacci spiral configuration, which is found in the nature from hurricanes to seashells, was considered for flow field pattern of a PEMFC. Contrary to the bio-inspired designs proposed in previous studies, continuous smooth change in the flow direction through curved spiral channel and flow field geometry restrained to the rounded area was attained. Computational studies for the PEMFC performance with Fibonacci spiral flow channel were conducted by solving the governing electrochemical equations using the Ansys Fluent software. In addition to the Fibonacci spiral geometry, a novel rectangular spiral design and the conventional parallel design were also simulated for performance comparisons. Polarization, power density, and fuel cell power output per required compressor power curves were computed in addition to distribution contours of pressure, velocity, reactant concentrations, and water mass fractions for all three flow field designs. Fibonacci spiral design exhibited uniform reactant distribution, improved water management, and extremely low-pressure drop compared to the rectangular spiral and conventional parallel designs --Abstract, page iii

Optimization of Flow Channel Design and Operating Parameters on Proton Exchange Membrane Fuel Cell Using MATLAB

Operating parameters like pressure, temperature, the stoichiometric ratio of reactants, relative humidity and design parameters like rib width to channel width (L:C), the shape of the flow channel and the number of passes on the flow channel are influencing the performance of the Proton Exchange Membrane Fuel Cell (PEMFC). In this paper, optimization of operating and design parameters such as pressure, temperature, inlet reactant mass flow rate and various rib width to channel width (L:C) 1:1, 1:2, 2:1 and 2:2 on serpentine and interdigitated flow channel of 25cm2 active area of the PEMFC was considered. Creo Parametric 1.0 and CFD Fluent 14.0 software packages were used to create the 3 Dimensional (3- D) model and simulation of PEMFC. The optimization was carried out on the various parameters with MINITAB 17 software and MATLAB software. From the first stage, the Landing to channel width (L: C) - 1:1 of serpentine and the interdigitated flow channel has the maximum influence on fuel cell performance and square of response factor (R2) was achieved from the Taguchi method by MINITAB 17 software as 99.48 and 99.71 % respectively. In the second stage, the regression equation or mathematical model obtained from MINITAB 17 software were fed into the MATLAB software to get optimized parameters. Further the power densities were obtained corresponding to the optimized parameters using the CFD Fluent 14.0 software

Experimental and numerical study of feeding channel in Proton Exchange Membrane Fuel Cell

The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) using different feeding configurations has been studied, with a focus on the water flooding due to electrochemical reaction. Feeding channel or Bipolar plate in Proton Exchange Fuel Cell is a dominating part. As feeding channel keeps direct contact with the gas diffusion layer, it helps efficiently supplying fuel and air into the gas diffusion layer for efficient production of electricity. Experimental data have been taken at hydrogen flow rates of 20,40,60,80,100 sccm for various bipolar plate arrangements. Three bipolar plates, namely serpentine, straight channel and interdigitated designs, were arranged in different combinations for the PEMFC anode and cathode sides. Nine combinations in total were tested under different flow rates, working temperatures and loadings. The cell voltage versus current density and the cell power density versus current density curves were obtained. Experimental results showed that for different feeding configurations, interdigitated bipolar plate in anode side and serpentine bipolar plate in cathode side had the best performance in terms of cell voltage-current density curve, power density output rate, percentage of flooded area in the feeding channels, the pattern of water flooding and the fuel utilization rate. It is found that the water patterns had a most dominating role for the cell performance. Naturally water forms due to the chemical reaction. The water could accumulate in the cell and lead to a lower cell performance. After operating the PEMFC under high current densities, the cell was split and the water flooding pattern in the feeding channels was visually inspected. Detailed studies of cell performance using a single channel bipolar plate have been performed. Experimental data for one channel were taken under a variety of flow rates. Computational simulations have been conducted for this one channel ‘cell’ and the simulation results were compared with the experimental results. Comparison shows very little difference between the experimental and the simulation work. It is expected that the outcomes of this study could help the future design of Proton Exchange Fuel Cell

Experimental and numerical analysis of fuel cells

Fuel Cells are attractive power source for use in electronic applications. Physical phenomena (water generation, saturation effect in fuel cell, poisoning, and thermal stress) are studied that governs the operation of a Proton Exchange Membrane Fuel Cell (PEMFC) and Solid Oxide Fuel cell (SOFC). Additionally, experimental studies and numerical simulations on PEMFC gas flow channel, the determination of the impact of the single channel fuel cell are presented. Furthermore, preliminary study is done for the application of APS (Air Plasma Spray) to SOFC and adhesion of anode and cathode with electrolytes for the determination of parameters involved in manufacturing the components of fuel cell. The new aspects on physical phenomena are significantly different from the currently popular relationships used in fuel cells as they are simplified from simulation and experimental results. In prior work, the physical phenomena such as water generation, saturation effect in fuel cell, poisoning, and thermal stress etc. are either assumed or used as adjustment parameters to simplify them or to achieve best fits with polarization data. In this work, physical phenomena are not assumed but determined via newly developed experimental and numerical techniques. The experimental fixtures and procedures were used to find better ways to control parameters of gas flow channel configurations for optimizing gas flow rates and performance, and gas flow channel pressure swing for CO poisoning recovery. The experimental results reveal controlling parameters for the mentioned cases and innovative design for Fuel cells. Numerical modeling were used to 2D and later 3D for simplification of single channel fuel cell model, transient localized heating to the catalyst layer for CO recovery, thermal stress that developed during SOFC fabrication by High Temperature vacuum Tube Furnace (HTVTF), and Gas Diffusion Layer and Gas Flow Channel (GDL-GFC) interfacial conditions with results based on commonly used relationships from the PEMFC literature. The modeling works reveal substantial impact on predicted GDL saturation, and consequently cause a significant impact on cell performance. Computational parametric relations and polarization curve results are compared to experimental polarization behavior which achieved a comparable relation

Parametric Analysis of Proton Exchange Membrane Fuel Cell (PEMFC) Performed by the Taguchi Method

The proton exchange membrane fuel cell (PEMFC) performance depends on the design parameters like landing-to-channel width ratio (L:C), channel depth, shape and number of passes on the flow channel, and operating parameters like temperature, pressure, the stoichiometric ratio of reactants, relative humidity, back pressure on the anode, and cathode flow channels. In this paper, optimization of design and operating parameters such as various landing -to-channel width ratios (L:C -1:1, 1:2, 2:1, and 2:2) of the interdigitated flow channel, pressure, temperature, and the anode and cathode inlet reactant masses on the 25cm^2 electrode surface active area of the PEMFC was carried out. A three dimensional (3-D) PEMFC model was created by Creo Parametric 1.0, meshed by ICEM 14.0 and simulated using the CFD Fluent 14.0 software packages. The optimization of the design and operating parameters was carried out in two stages using Minitab 17 with a standard orthogonal array of the Taguchi method. From the first stage of analysis, it was inferred that the landing-to-channel width ratio (L:C - 1:1) has the biggest influence on the PEMFC performance and the square of response factor (R^2) was achieved by the Taguchi method at 97.95%. In the second stage of analysis, fine-tuned optimization was performed on selected factors which cause an increase in power density of 0.81. Also, R^2 was achieved at 100 % and the results were also validated using the CFD Fluent 14.0 software packages

Comparative study of conventional and unconventional designs of cathode flow fields in PEM fuel cell

The choice of an appropriate flow field distributor is crucial to circumvent mass and charge transfer resistance-related issues in proton exchange membrane fuel cells (PEMFCs). In this work, incorporating all the anisotropic nature of the gas diffusion layers (GDLs), a three-dimensional, multiphase CFD model is built to perform a comparative study of several types of cathode flow field designs. Three conventional (i.e. parallel, serpentine and interdigitated) and two recently-introduced (i.e. parallel with blocks and the metal foam) flow field designs were considered for the cathode side. The results showed that the best fuel cell performance is obtained with the metal foam flow field as it induces the lowest water saturation, the lowest values and more uniform distribution of current density and temperature as well as relatively medium pressure drop. Compared with the parallel flow field case, the peak power density increases by about 50% when using the metal foam flow field and by about 10% when using the other three investigated flow fields (i.e. serpentine, interdigitated and parallel with blocks). The parametric analysis reveals that the metal foam outperforms other designs at intermediate and high humidity conditions whereas the interdigitated flow field design outperforms other designs at low humidity conditions