Numerical Analysis of the Effect of Different Channel Geometries and Electrode Materials on the Performance of Microfluidic Fuel Cells

2010 ◽  
Author(s):  
Ali Ebrahimi Khabbazi ◽  
Andrew Richards ◽  
Mina Hoorfar
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Laminar Flow ◽  
Power Density ◽  
Porous Electrode ◽  
Pem Fuel Cells ◽  
Porous Electrodes ◽  
Electrochemical Reactions ◽  
Flow Through ◽  
Microfluidic Fuel Cell

A typical microfluidic fuel cell is comprised of a Y- or T-shaped microchannel. The fuel and the oxidant streams are introduced from the two different inlets. The anodic and cathodic flows meet each other at the beginning of the main channel and start to travel together along the channel. Due to the fact that the viscous forces dominate the inertia forces in microchannels, the oxidant and the fuel streams establish a side-by-side co-laminar flow which makes the anolyte and catholyte flow together without turbulent mixing. Laminar flow in microfluidic fuel cells plays the role of the membrane in proton exchange membrane (PEM) fuel cells by maintaining the separation of the fuel and oxidant. This eliminates the need for the membrane and overcomes the membrane-related issues such as the ohmic overpotential and water management which are relevant to PEM fuel cells. In addition to the above advantage, the high surface-to-volume ratio of these micron-scale devices contributes to their high power density. This advantage is due to the fact that the electrochemical reactions in fuel cells are surface-based. The electrodes on which the electrochemical reactions are occurring are installed appropriately on the walls of the channel in a way that reacting flows are restricted to the proper electrodes. Since the flow is laminar the performance of the microfluidic fuel cell significantly depends on the device geometry. In this paper, different channel geometries and different electrode configurations are modeled and their performances are compared through the polarization curves. It has been found that the high aspect ratio provides the largest power density. In this work, the performance of the flow-through porous electrode was also modeled and compared against the conventional non-porous electrode microfluidic fuel cells. The flow-through porous electrode design is based on cross-flow of aqueous vanadium redox species through the electrodes into an exit channel, where the waste solutions meet and establish a co-laminar flow. This co-laminar flow of reacted species facilitates ionic charge transfer in a membraneless configuration. It has been found that the flow-through porous architecture provides an increased active surface area which contributes to a higher power density as opposed to the fuel cells with non-porous electrodes.

Up-Scaled Microfluidic Fuel Cells With Porous Flow-Through Electrodes

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
D. Fuerth ◽  
A. Bazylak
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Surface Area ◽  
Electrode Surface ◽  
Porous Electrode ◽  
Porous Electrodes ◽  
Carbon Paper ◽  
Platinum Black ◽  
Flow Through ◽  
Microfluidic Fuel Cell

In this work, an experimental microfluidic fuel cell is presented with a novel up-scaled porous electrode architecture that provides higher available surface area compared to conventional microfluidic fuel cells, providing the potential for higher overall power outputs. Our proof-of-concept architecture is an up-scaled flow-through fuel cell with more than nine times the active electrode surface area of the flow-through architecture first proposed by Kjeang et al. (2008, “A Microfluidic Fuel Cell With Flow-Through Porous Electrodes,” J. Am. Chem. Soc., 130, pp. 4000–4006). Formic acid and potassium permanganate were employed as the fuel and oxidant, respectively, both dissolved in a sulfuric acid electrolyte. Platinum black was employed as the catalyst for both anode and cathode, and the performances of carbon-based porous electrodes including cloth, fiber, and foam were compared to that of traditional Toray carbon paper (TGP-H-120). The effects of catalyst loading were investigated in a microfluidic fuel cell containing 80 pores per linear inch carbon foam electrodes. A discussion is also provided of current density normalization techniques via projected electrode surface area and electrode volume, the latter of which is a highly informative means for comparing flow-through architectures.

“Bleaching” glycerol in a microfluidic fuel cell to produce high power density at minimal cost

2018 ◽  
Vol 54 (2) ◽  
pp. 192-195 ◽  
Author(s):  
Cauê A. Martins ◽  
Omar A. Ibrahim ◽  
Pei Pei ◽  
Erik Kjeang
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Power Density ◽  
High Power ◽  
High Power Density ◽  
Minimal Cost ◽  
Flow Through ◽  
Microfluidic Fuel Cell

Glycerol/bleach flow-through microfluidic fuel cells are presented.

Modeling of Microfluidic Fuel Cells With Flow-Through Porous Electrodes

2010 ◽  
Author(s):  
Ali Ebrahimi Khabbazi ◽  
Mina Hoorfar
Keyword(s):  
Fuel Cell ◽  
Solid Phase ◽  
Porous Electrode ◽  
Porous Electrodes ◽  
Metal Catalyst ◽  
Redox Species ◽  
Redox Couples ◽  
Flow Through ◽  
Microfluidic Fuel Cell ◽  
Vanadium Redox

This paper presents a modeling of a microfluidic fuel cell with flow-through porous electrodes using vanadium redox couples as the fuel and oxidant. There are advantages associated with the use of vanadium redox species in microfluidic fuel cell: 1) vanadium redox couples have the possibility of producing high open-circuit potential (up to 1.7 V at uniform PH [1]); 2) they have high solubility (up to 5.4 M) which causes more species available to the electrodes; 3) they do not require metal catalyst for electrochemical reactions so the reactions take place on the bare carbon electrodes. This characteristic of the vanadium redox couple make them a great candidate as reactants as they do not need expensive catalyst coatings on the electrodes. The fuel and the oxidant can be brought into contact with the electrode in two different ways: flowing over the electrodes or flowing through the electrodes. In the presented fuel cell design, the vanadium redox species are forced to flow through the porous electrodes. They finally come to meet each other in the middle microchannel and establish a side-by-side co-laminar flow traveling down the channel. In this paper, the effect of the inlet velocity and electrode porosity has been investigated. As it is expected, the higher velocity results in the higher power densities. For the porosity, however, there is an optimum value. In essence, there is a trade-off between the available electrode surface area and electric conductivity of the solid phase (i.e., the porous carbon electrode). The modeling shows that a porous electrode with a 67% porosity results in the highest power output.

Model-based analysis of geometrical effects in microfluidic fuel cell with flow-through porous electrodes

2019 ◽  
Vol 34 (01n03) ◽  
pp. 2040022
Author(s):  
Qiang Xu ◽  
Yiyi She ◽  
Li Li
Keyword(s):  
Fuel Cell ◽  
Reaction Rate ◽  
Fluid Velocity ◽  
Porous Electrode ◽  
Three Dimensional ◽  
Porous Electrodes ◽  
Aspect Ratios ◽  
Electrode Length ◽  
Flow Through ◽  
Microfluidic Fuel Cell

Porous electrodes in microfluidic fuel cell (MFC) operate with nonuniform reaction rate. It is intriguing to improve the utilization degree of the porous electrodes. In this work, a three-dimensional computational model is developed for MFC with flow-through porous electrodes. Characteristics of the reaction rate distributions under different electrode geometries are examined. The results show that reaction rate varies noticeably along the electrode width direction, but minimally along the electrode length direction. High reaction rate region locates in the vicinity of the interface between the porous electrode and the middle channel. A relatively high aspect ratio, defined as the ratio of the electrode length to width, is beneficial to improve the utilization degree of the porous electrodes. Yet, concentration losses increase due to the decreased fluid velocity. Considering the cell performance, optimal electrode aspect ratios are derived for the anode and cathode, respectively.

A Microfluidic Fuel Cell with Flow-Through Porous Electrodes

2008 ◽  
Vol 130 (12) ◽  
pp. 4000-4006 ◽  
Author(s):  
Erik Kjeang ◽  
Raphaelle Michel ◽  
David A. Harrington ◽  
Ned Djilali ◽  
David Sinton
Keyword(s):  
Fuel Cell ◽  
Porous Electrodes ◽  
Flow Through ◽  
Microfluidic Fuel Cell

Optimal design of current collectors for microfluidic fuel cell with flow-through porous electrodes: Model and experiment

2017 ◽  
Vol 206 ◽  
pp. 413-424 ◽  
Author(s):  
Li Li ◽  
Wenguang Fan ◽  
Jin Xuan ◽  
Michael K.H. Leung ◽  
Keqing Zheng ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Optimal Design ◽  
Porous Electrodes ◽  
Current Collectors ◽  
Flow Through ◽  
Microfluidic Fuel Cell

Air-Breathing Membraneless Laminar Flow Fuel Cell With Flow-Through Anode

2011 ◽  
Author(s):  
Seyed Ali Mousavi Shaegh ◽  
Nam-Trung Nguyen ◽  
Siew Hwa Chan
Keyword(s):  
Fuel Cell ◽  
Laminar Flow ◽  
Power Density ◽  
Maximum Power Density ◽  
Reference Case ◽  
Higher Power ◽  
Flow Through ◽  
Fabrication And Characterization ◽  
Porous Anode

This paper reports the fabrication and characterization of a new concept of flow-through anode for membraneless laminar flow fuel cell (LFFC). To establish a reference case, a fuel cell with flow over and planar anode was fabricated as well. Experimental results indicated that maximum power density was improved from 17 mW/cm2 in planar design to 23 mW/cm2 using the flow-through design. The higher power density of flow-through design is an indicative of higher fuel utilization in the porous anode. Images of the flow obtained experimentally showed that mixing was reduced at the liquid-liquid interface in the channel with flow-through anode leading to increased fuel concentration over anode.

scholarly journals Numerical Simulations of Gaseous Mixture Flow in Porous Electrodes for PEM Fuel Cells by the Lattice Boltzmann Method

2005 ◽  
Author(s):  
Pietro Asinari ◽  
Marco Coppo ◽  
Michael R. von Spakovsky ◽  
Bhavani V. Kasula
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Lattice Boltzmann ◽  
Applied Pressure ◽  
Gaseous Mixture ◽  
Pem Fuel Cells ◽  
Proton Exchange ◽  
Porous Electrodes ◽  
Extended Model ◽  
Gaseous Mixtures

Throughout the last decade, a considerable amount of work has been carried out in order to obtain ever more refined models of proton exchange membrane (PEM) fuel cells. While many of the phenomena occurring in a fuel cell have been described with ever more complex models, the flow of gaseous mixtures in the porous electrodes has continued to be modeled with Darcy’s law in order to take into account interactions with the solid structure and with Fick’s law in order to take into account interactions among species. Both of these laws derive from the macroscopic continuum approach, which essentially consists of applying some sort of homogenization technique which properly averages the underlying microscopic phenomena for producing measurable quantities. Unfortunately, these quantities in the porous electrodes of fuel cells are sometimes measurable only in principle. For this reason, this type of approach introduces uncertain macroscopic parameters which can significantly affect the numerical results. This paper is part of an ongoing effort to address the problem following an alternative approach. The key idea is to numerically simulate the underlying microscopic phenomena in an effort to bring the mathematical description nearer to actual reality. In order to reach this goal, some recently developed mesoscopic tools appear to be very promising since the microscopic approach is in this particularly case partially included in the numerical method itself. In particular, the lattice Boltzmann models treat the problem by reproducing the collisions among particles of the same type, among particles belonging to different species, and finally among the species and the solid obstructions. Recently, a procedure based on a lattice Boltzmann model for calculating the hydraulic constant as a function of material structure and applied pressure gradient was defined and applied. This model has since been extended in order to include gaseous mixtures with different methods being considered in order to simulate the coupling strength among the species. The present paper reports the results of this extended model for PEM fuel cell applications and in particular for the analysis of the fluid flow of gaseous mixtures through porous electrodes. Because of the increasing computational needs due to both three–dimensional descriptions and multi-physics models, the need for large parallel computing is indicated and some features of this improvement are reported.

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