Graduated Flow Resistance Through a GDL in a Novel PEM Stack

2009 ◽  
Author(s):  
Terry B. Caston ◽  
Kanthi L. Bhamidipati ◽  
Haley Carney ◽  
Tequila A. L. Harris
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte Membrane ◽  
Catalyst Layer ◽  
Current Density Distribution ◽  
Pem Fuel Cell ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Electrolyte Membrane

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability, and therefore a graduated resistance to flow throughout the GDL. It has been shown that using conventional materials the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack, where the reactant gases are supplied through the side of the GDL rather than through flow field channels, which are machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, and thickness of the GDL on the expected current density distribution at the catalyst layer are studied. Three different thicknesses are investigated, and it is found that as GDL thickness increases, more uniform reactant distribution over the face of the GDL is obtained. Results also show that it is necessary to design a GDL with a much higher in-plane resistance than through-plane resistance for the unconventional PEM stack studied.

3D Modeling of Polymer Electrolyte Membrane Fuel Cells

2003 ◽  
Author(s):  
Sacheverel Eldrid ◽  
Mehrdad Shahnam ◽  
Michael T. Prinkey ◽  
Zhirui Dong
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte Membrane ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Hydrogen Ions ◽  
Electrolyte Membrane ◽  
Diffusion Layers ◽  
Flow Channels ◽  
Porous Anode

Polymer Electrolyte Membrane (PEM) fuel cell performance can be optimized and improved by modeling the complex processes that take place in the various components of a fuel cell. Operability over a range of conditions can be assessed using a robust design methodology. Sensitivity analysis can identify critical characteristics in order to guide hardware and softgoods development. A computational model is necessary which captures the critical physical processes taking place within the cell. Such a model must be validated against experimental data before it can be used for product development. A computational model of an experimental PEM fuel cell has been developed. The model is based on the FLUENT CFD solver with the addition of user-defined functions supplied by FLUENT. These functions account for local electrochemical reactions, electrical conduction within diffusion layers and current collectors, mass and heat transfer in the diffusion layers and the flow channels along with binary gas diffusion. The results of this model are compared to experimental data. A PEM fuel cell consists of an ion conducting membrane, anode and cathode catalyst layers, anode and cathode gas diffusion layers, flow channels, and two bipolar plates. Hydrogen and oxygen are supplied to the anode and cathode respectively. As a result of hydrogen oxidation at the anode catalyst layer, hydrogen ions and electrons are produced. The hydrogen ions are conducted through the membrane to the cathode catalyst layer where they combine with oxygen and electrons to produce water and heat. Therefore, a PEM fuel cell model has to take into account: • Fluid flow, heat transfer, and mass transfer in porous anode and cathode diffusion layers; • Electrochemical reactions; • Current transport and potential field in porous anode, cathode, and solid conducting regions. FLUENT Inc. has developed such a model based on their commercially available FLUENT CFD code. This model was exercised on an experimental Plug Power fuel cell. The voltage characteristic of the model was compared to the experimentally measured values. The preliminary comparison between the predicted polarization curve and the experimental results are very favorable.

Heat and Mass Transport Analysis of Polymer Electrolyte Membrane Fuel Cell With Bipolar Plates

2009 ◽  
Author(s):  
Pavan Kumar Konnepati ◽  
Pradip Majumdar
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Current Density ◽  
Gas Flow ◽  
Polymer Electrolyte Membrane ◽  
Pem Fuel Cell ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Electrolyte Membrane

Fuel cells convert chemical energy of fuels into electricity directly. Their higher efficiency and low emissions made them prime candidates for next generation power requirements. The Polymer Electrolyte Membrane (PEM) fuel cell has gained attention of both transportation and stationary power generation industries. In this study a three-dimensional computational model for the simulation of Polymer Electrolyte Membrane (PEM) fuel cell unit cell is developed to understand the complex internal mechanisms, and evaluate the effects of bipolar plate designs on the cell performance. The model includes combined heat and mass transfer processes due to convection and diffusion in the gas flow channels of bi-polar plates as well in the gas diffusion layers of the electrodes, and associated electrochemical reactions in a tri-layer PEM fuel cell. Simulation is carried out with straight parallel channels for operating current density in the range from 0.5–1.5 A/cm2 showed significant insight details of PEM fuel cell in terms of distribution of reactant gases, and heat and water transport across the cell. A significantly high variation in gas concentration across the electrode–membrane interfaces and along the channel length is noticed, requiring higher stoichiometric ratios to increase the limiting current density.

Development of a PEM Fuel Cell Electrode Coating Testbed

2010 ◽  
Author(s):  
Casey J. Hoffman ◽  
Daniel F. Walczyk
Keyword(s):  
Fuel Cell ◽  
Large Scale ◽  
Platinum Catalyst ◽  
Polymer Electrolyte Membrane ◽  
Quality Measurement ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Electrode Coating

Two of the largest barriers to PEMFC commercialization are the materials costs for individual components, especially platinum catalyst, and the fact that few large-scale manufacturing capabilities currently exist. This paper focuses on the development of a testbed which will be used for evaluating coating technologies for use in the manufacture of polymer electrolyte membrane (PEM) fuel cell electrodes. More specifically, the focus is on diffusion electrode architecture, in which the catalyst layer is applied to a gas diffusion layer (GDL) rather than on the membrane. These electrodes are used for both low- and high-temperature PEM fuel cells. A flexible web coating testbed has been designed and built to allow for testing of different gas diffusion electrode (GDE) and GDL deposition methods. This testbed, which is approximately two meters in length, includes a variety of both coating and drying capabilities as well as additional space for quality measurement and control system testing. Testbed capabilities and planned experimentation is discussed in detail. In the future, various non-contact deposition methods for the microlayer and catalyst inks will be investigated (e.g., direct spray, ultrasonic spray) to determine those that will provide higher throughput and repeatability through increased process control capability, while improving electrode performance.

CFD Simulation of Flow Through the Reconstructed Microstructure of Fibrous Gas Diffusion Layer in a Polymer Electrolyte Membrane Fuel Cell

2018 ◽  
Vol 13 (1) ◽  
Author(s):  
Venkata Suresh Patnaikuni ◽  
Sreenivas Jayanti
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Diffusion Layer ◽  
Polymer Electrolyte Membrane ◽  
Effective Diffusion ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Electrolyte Membrane

AbstractThe gas diffusion layer (GDL) is one of the key components in a polymer electrolyte membrane (PEM) fuel cell. Generally it is a carbon-based fibrous medium that allows for the transport of electrons through the fibers and distributes the reactants through the void space to the catalyst layer in a PEM fuel cell. In the present work, a microstructure study of reactant transport is carried out by reconstructing the typical fibrous microstructure of the GDL and investigating the transport characteristics of the porous medium using computational fluid dynamics (CFD) simulations. The results confirm the applicability of Darcy’s law formulation for permeability determination and Bruggemann correction for calculation of effective diffusivity for typical conditions encountered in PEM fuel cells. Macroscopic material properties such as through-plane and in-plane permeabilities and effective diffusion coefficient are determined and compared against experimental values reported in the literature.

Graduated Resistance to Gas Flow Through a GDL in an Unconventional PEM Stack

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Terry B. Caston ◽  
Kanthi L. Bhamidipati ◽  
Haley Carney ◽  
Tequila A. L. Harris
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Gas Flow ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Oxygen Utilization ◽  
Average Current Density ◽  
Reactant Distribution

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability and thereby graduating the resistance to flow throughout the GDL. It has been shown that in using conventional materials, the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack where the reactant gases are supplied through the side of the GDL rather than through flow field channels machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, GDL thickness, and oxygen utilization on the expected current density distribution at the catalyst layer are studied. Three different thicknesses and three different utilizations are investigated. It has been found that a thinner GDL with a lower utilization yields a higher current density on the electrode. A quantitative metric to measure uniformity of reactant distribution and the ratio of the standard deviation of the current density to the average current density was introduced, and it was found that while the uniformity of the reactant distribution is independent of thickness of the GDL, it is inversely proportional to utilization.

Probing the influence of the gas diffusion layer on water retention in membrane electrode assemblies via electrochemical impedance spectroscopy

2018 ◽  
Author(s):  
Foroughazam Afsahi ◽  
E. Bradley Easton
Keyword(s):  
Fuel Cell ◽  
Electrochemical Impedance ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Cell Performance ◽  
Carbon Paper ◽  
Membrane Electrode ◽  
Fuel Cell Performance ◽  
Electrode Assemblies

The effect of the relative humidity (RH) of supplied gases on PEM fuel cell performance was monitored by electrochemical impedance spectroscopy (EIS). Two different Nafion®-based membrane electrode assemblies (MEAs) were prepared from two commercially available gas diffusion layers (GDLs) based on carbon paper and carbon cloth. By performing EIS measurements under condition where the transmission line model was applicable, both the ionic resistance in catalyst layer (RΣ) and the membrane resistance (Rmem) could be probed. The extent of this impact, however, depends on the GDL substrate properties and the electrode side to which the dry gas was fed. Overall, the carbon paper based MEA provided better fuel cell performance when the dry gas condition was applied, whereas the cloth based MEA revealed better fuel cell performance with fully saturated reactant gases. Moreover, the later one demonstrates a better capability to address the flooding issue at high current density even when symmetric dry gas arrangement (both dry fuel and oxidant gases) was studied. Variation of fuel gas RH at the anode perturb the fuel cell performance less strongly compared with the other arrangements. This implies that with the fully hydrated cathode gas water transport via back diffusion from the cathode to the anode could maintain the hydrated membrane and catalyst layer to some extent. By using this EIS methodology, the interplay of GDL properties and reactant gases RH on PEM fuel cell performance can be more clearly understood.

Determination of the Relationship Between Capillary Pressure and Saturation in PEMFC Gas Diffusion Media

2008 ◽  
Author(s):  
Joshua D. Sole ◽  
Michael W. Ellis
Keyword(s):  
Capillary Pressure ◽  
Liquid Water ◽  
Polymer Electrolyte Membrane ◽  
Catalyst Layer ◽  
Gas Diffusion ◽  
Carbon Cloth ◽  
Electrolyte Membrane ◽  
Diffusion Media ◽  
Capillary Pressures ◽  
The Relationship

This paper describes a method of measuring the relationship between capillary pressure and porous media saturation in the gas diffusion layer (GDL) of a polymer electrolyte membrane fuel cell (PEMFC). Such a relationship is commonly used to model the liquid water flow in the GDL. The method utilized to characterize the GDL behavior mimics the actual transport of liquid water within the GDL by utilizing the actual fluids of interest in a PEMFC cathode (water and air), and by introducing all water from a single face to simulate the water production at the catalyst layer. Other porosimetry methods rely on totally non-wetting or totally wetting fluids to achieve saturation and consequently the resulting capillary pressure measurements must be scaled to the emulate the situation in the PEMFC GDL. Capillary pressure versus saturation curves for two different GDL materials (one paper, one cloth), each with four different bulk loadings of PTFE (0, 10, 20 and 30 wt%), were measured. Results show that the PTFE loading has a relatively small effect on the capillary pressure within the pressure range normally associated with PEMFC water transport. The results also show that carbon cloth based GDL materials require greater capillary pressures than paper materials to achieve significant saturation and that compression has a homogenizing effect on the pore structure and the slope of the capillary pressure – saturation Pc(S) behavior of both materials. Representative curves for the derivative of the Pc(S) function are developed for each type of diffusion media within the appropriate saturation range.

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