Unitized Regenerative Fuel Cell Performance Using Polymer Wicks for Passive Water Management

2013 ◽  
Author(s):  
Sandeep S. Lele ◽  
Michael A. Sizemore ◽  
Sutyen S. Zalawadia ◽  
Aitor P. Zabalegui ◽  
Abdie H. Tabrizi ◽  
...  
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Transport ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Cathode Side ◽  
Membrane Electrode ◽  
Flow Channels ◽  
Operating Current ◽  
Regenerative Fuel Cell

Proton Exchange Membrane (PEM) fuel cells rely on effective internal water transport to provide stable performance. Many water management schemes require high heat, high pressure, or high flow rates — effectively introducing parasitic losses and reducing round-trip efficiency. In this work, a radial, non-recirculating, unitized regenerative fuel cell prototype with passive water transport is designed and tested. The cell features a 5 cm2 active area with 1.2 mm wide by 0.6 mm high gas flow channels. Porous polymer wicks are fabricated in the cathode side flow channels and coupled with a bulk water storage structure. The resulting wicks are 0.3 mm wide and 0.6 mm high. Discharge operating voltage measured during current control testing resulted in 1 V at open circuit, 0.8 V at 0.3 A·cm−2, and 0.2 V at 1 A·cm−2. Charge operating current density measured during voltage control testing resulted in 0.1 A·cm−2 at 1.5 V, 0.3 A·cm−2 at 1.6 V, and 0.8 A·cm−2 at 2 V. During the membrane electrode assembly (MEA) conditioning procedure, degradation in operating current density is seen over a 30–100 minute time span.

A Critical Review of Water Transport Models in Gas Diffusion Media of PEM Fuel Cell

2008 ◽  
Author(s):  
Jacob LaManna ◽  
Satish G. Kandlikar
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Transport ◽  
Combustion Engine ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Cathode Side ◽  
Small Scale

Proton Exchange Membrane (PEM) fuel cells are gaining popularity as a replacement to the internal combustion engine in automobiles. This application will demand high levels of performance from the fuel cell making it critical that proper water management is maintained. One of the areas of interest in water management is the transport of water through the Gas Diffusion Medium (GDM) on the cathode side of the cell. Research is currently being conducted to understand how water moves through the porous structure of the GDM. Due to the small scale of the GDM, most work done is analytical modeling. This paper will focus on reviewing current models for water transport within the GDM of a PEM fuel cell to address state of the art and provide recommendations for future work to extend current models.

Fabrication and Performance Evaluation of Miniaturized Proton Exchange Membrane (PEM) Fuel Cells

2003 ◽  
Author(s):  
Tao Zhang ◽  
Pei-Wen Li ◽  
Qing-Ming Wang ◽  
Laura Schaefer ◽  
Minking K. Chyu
Keyword(s):  
Mass Transfer ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Free Convection ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Proton Exchange ◽  
Cathode Side ◽  
Ohmic Loss ◽  
Fuel Cell Performance

Two types of miniaturized PEM fuel cells are designed and characterized in comparison with a compact commercial fuel cell device in this paper. One has Nafion® membrane electrolyte sandwiched by two brass bipolar plates with micromachined meander-like gas channels. The cross-sectional area of the gas flow channel is approximately 250 by 250 (μm). The other uses the same Nafion® membrane and anode structure, but in stead of the brass plate, a thin stainless steel plate with perforated round holes is used at cathode side. The new cathode structure is expected to allow oxygen (air) being supplied by free-convection mass transfer. The characteristic curves of the fuel cell devices are measured. The activation loss and ohmic loss of the fuel cells have been estimated using empirical equations. Critical issues such as flow arrangement, water removing and air feeding modes concerning the fuel cell performance are investigated in this research. The experimental results demonstrate that the miniaturized fuel cell with free air convection mode is a simple and reliable way for fuel cell operation that could be employed in potential applications although the maximum achievable current density is less favorable due to limited mass transfer of oxygen (air). The relation between the fuel cell dimensions and the maximum achievable current density is also discussed with respect to free-convection mode of air feeding.

An Improved Model to Predict Flooding/Dehydration in PEM Fuel Cells

2005 ◽  
Author(s):  
S. Maharudrayya ◽  
S. Jayanti ◽  
A. P. Deshpande
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Vapour ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Operating Conditions ◽  
Fickian Diffusion ◽  
Closed Form Expression ◽  
Water Vapour Diffusion ◽  
Improved Model

Maintaining proper water balance between the production of water due to reaction and its removal by evaporation is very important for the successful operation of a Polymer Electrolyte Membrane (PEM) fuel cell. Imbalance between the two processes can result in either flooding of the electrodes/ gas channels or the dehydration of the membrane. The water management issue is especially critical for ambient temperature operation of the fuel cell. Several experimental and theoretical studies relevant to water management have been carried out to investigate means of reducing the flooding of electrodes/channels or the dehydration of membrane. Bernardi [9] and Wang et al. [11] have developed theoretical models for the prediction of when flooding/dehydration may take place. In the present study, an improved model is developed which combines the advantages of these two models. The Bernardi [9] model is extended to include mass transfer resistances. Following Wang et al. [11], the Stefan-Maxwell description of multicomponent diffusion is replaced by Fickian diffusion. In addition, water vapour diffusion to both anode and cathode sides is included in the model. The overall model is in the form of a closed-form expression for the critical or threshold or balance current density at which the water production rate and the water vapour evacuation rate are exactly balanced. The model shows that the balance current density is a function of operating conditions, properties of electrode, flow and geometric parameters in the gas channels. It has been validated by comparing the predictions with the experimental data of Tu¨ber et al. [5] and Eckl et al. [8].

Three-Dimensional Simulation of Water Droplet Movement in PEM Fuel Cell Flow Channels with Fluid-Mechanics Properties and Different Deformations of GDL

2012 ◽  
Vol 625 ◽  
pp. 53-56 ◽  
Author(s):  
Ning Bao ◽  
Qing Du ◽  
Yan Yin
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Liquid Water ◽  
Water Droplet ◽  
Three Dimensional ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Cathode Side ◽  
Gas Channel ◽  
Flow Channels

Water management plays a significant role in enhancing performance of proton exchange membrane fuel cell (PEMFC). Successful water management requires effective removal of liquid water produced by electrochemical reactions. Therefore, it is a critical challenge to understand liquid water movements in flow channels. In the present study, a three-dimensional unsteady two-phase model for the cathode side of PEMFC consisting of gas channel (GC), gas diffusion layer (GDL) and catalyst layer (CL) is developed using FLUENT software with a volume-of-fluid (VOF) method and user-defined-function (UDF). When fuel cells are assembled, the cross sections of gas channel change, resulting in different water droplet movements. The effects of GDL deformations on water droplet movements are discussed.

The Effect of Variable Catalyst Loading in Electrodes on PEM Fuel Cell Performance

2005 ◽  
Author(s):  
R. Roshandel ◽  
B. Farhanieh
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Cell Performance ◽  
Cathode Side ◽  
Catalyst Loading ◽  
Fuel Cell Performance ◽  
Reactant Concentration

Catalyst layers are one the important parts of the PEM fuel cells as they are the main place for electrochemical reaction taking place in anode and cathode of the cells. The amount of catalyst loading of this layer has a large effect on PEM fuel cell performance. Non-uniformity of reactant concentration could lead to a variation of current density in anode and cathode catalyst layer. The main reason for this phenomenon is porosity variation due to two effects: 1. compression of electrode on the solid landing area and 2. Water produced at the cathode side of diffusion layer. In this study the effect of variable current density in anode and cathode electrode on cell performance is investigated. It has shown that better cell performance could be achieved by adding a certain amount of catalyst loading to each electrode, with respect to the reactant concentration.

Modeling Water Content Distribution in the Polymer Electrolyte Membrane of PEM Fuel Cell

2011 ◽  
Author(s):  
Bahareh Alsadat Tavakoli ◽  
Ramin Roshandel
Keyword(s):  
Fuel Cell ◽  
Water Content ◽  
Current Density ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Cell Polarization ◽  
Proton Exchange ◽  
Membrane Electrode ◽  
Isothermal Model

Models play an important role in fuel cell design and development. One of the critical problems to overcome in the proton exchange membrane (PEM) fuel cells is the water management. In this work a steady state, two dimensional, isothermal model in a single PEM fuel cell using individual computational fluid dynamics code was presented. Special attention was devoted to the water transport through the membrane which is assumed to be combined effect of diffusion, electro osmotic drag and convection. The effect of current density variation distribution on the Water content (λ) in membrane/electrode assembly (MEA) was determined. After that detailed distribution of oxygen concentration, water content in membrane, net water flux and different overpotentials were calculated. Simulation results show that the reduction of reactant concentration in flow channels has a significant effect on electrochemical reaction in the gas diffusion and catalyst layer. Different fluxes are compared to investigate the effect of operating condition on the water fluxes in membrane. The amount of different fluxes is a strong function of current density which is related to external load. The model prediction of water content curves are compared with one dimensional model predictions data reported in the validated open literature and good compatibility were observed. In addition, the model predicted fuel cell polarization curves compared well with experimental and numerical data.

A Study of Water and Oxygen Distributions in the Cathode Flow Channels of a PEM Fuel Cell

2006 ◽  
Author(s):  
Han-Sang Kim ◽  
Taehun Ha ◽  
Kyoungdoug Min
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Saturation ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Experimental Results ◽  
Fuel Cell Performance ◽  
Flow Channels

Water management is a critical operation issue for achieving the highest possible performance of proton exchange membrane (PEM) fuel cells. Quantitative determination of water and species distribution is needed to understand the water management and reactant distribution effects. In this study, the measurement of water and oxygen distributions along cathode flow channels was carried out using gas chromatography (GC). Generally, it is difficult to measure water distribution where water concentration is too high. Here, the measurement of high levels of water saturation in cathode channels was performed according to fuel cell operating conditions. GC measurement was also carried out for flooding and non-flooding conditions. To compare the experimental results with computational results, the three-dimensional CFD simulation of a unit fuel cell was performed using es-pemfc, which is the PEM fuel cell module of commercial CFD code STAR-CD. For the entrance of flow channel that has relatively lower level of water content, the calculated results showed good agreement with measured results. However, some discrepancy between calculated and experimental results was still found for the flow channels near the cathode outlet. The study provides the necessity of the development and adoption of a comprehensive multidimensional PEM fuel cell models including two-phase flow and cathode flooding phenomena for the optimization of fuel cell performance.

Critique and Improvement of a One-Dimensional Semianalytical Model of a Direct Methanol Fuel Cell

2012 ◽  
Vol 9 (5) ◽  
Author(s):  
C. C. Kuo ◽  
W. E. Lear ◽  
J. H. Fletcher ◽  
O. D. Crisalle
Keyword(s):  
Fuel Cell ◽  
Polarization Curve ◽  
Current Density ◽  
Direct Methanol Fuel Cell ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
One Dimensional ◽  
Implicit Equation ◽  
Direct Methanol ◽  
Methanol Fuel Cell

A constructive critique and a suite of proposed improvements for a recent one-dimensional semianalytical model of a direct methanol fuel cell are presented for the purpose of improving the predictive ability of the modeling approach. The model produces a polarization curve for a fuel cell system comprised of a single membrane-electrode assembly, based on a semianalytical one-dimensional solution of the steady-state methanol concentration profile across relevant layers of the membrane electrode assembly. The first improvement proposed is a more precise numerical solution method for an implicit equation that describes the overall current density, leading to better convergence properties. A second improvement is a new technique for identifying the maximum achievable current density, an important piece of information necessary to avoid divergence of the implicit-equation solver. Third, a modeling improvement is introduced through the adoption of a linear ion-conductivity model that enhances the ability to better match experimental polarization-curve data at high current densities. Fourth, a systematic method is advanced for extracting anodic and cathodic transfer-coefficient parameters from experimental data via a least-squares regression procedure, eliminating a potentially significant parameter estimation error. Finally, this study determines that the methanol concentration boundary condition imposed on the membrane side of the membrane-cathode interface plays a critical role in the model’s ability to predict the limiting current density. Furthermore, the study argues for the need to carry out additional experimental work to identify more meaningful boundary concentration values realized by the cell.

Effect of Vibration on the Liquid Water Transport of PEM Fuel Cells

2009 ◽  
Author(s):  
Luis Breziner ◽  
Peter Strahs ◽  
Parsaoran Hutapea
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Water Transport ◽  
Liquid Water ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Cell Performance ◽  
Sinusoidal Vibration ◽  
Fuel Cell Performance ◽  
Liquid Water Transport

The objective of this research is to analyze the effects of vibration on the performance of hydrogen PEM fuel cells. It has been reported that if the liquid water transport across the gas diffusion layer (GDL) changes, so does the overall cell performance. Since many fuel cells operate under a vibrating environment –as in the case of automotive applications, this may influence the liquid water concentration across the GDL at different current densities, affecting the overall fuel cell performance. The problem was developed in two main steps. First, the basis for an analytical model was established using current models for water transport in porous media. Then, a series of experiments were carried, monitoring the performance of the fuel cell for different parameters of oscillation. For sinusoidal vibration at 10, 20 and 50Hz (2 g of magnitude), a decrease in the fuel cell performance by 2.2%, 1.1% and 1.3% was recorded when compared to operation at no vibration respectively. For 5 g of magnitude, the fuel cell reported a drop of 5.8% at 50 Hz, whereas at 20 Hz the performance increased by 1.3%. Although more extensive experimentation is needed to identify a relationship between magnitude and frequency of vibration affecting the performance of the fuel cell as well as a throughout examination of the liquid water formation in the cathode, this study shows that sinusoidal vibration, overall, affects the performance of PEM fuel cells.

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