The Woodruff School

SUMMARY

Due to escalating energy costs and limited fossil fuel resources, much attention has been given to Polymer Electrolyte Membrane (PEM) fuel cells. Gas Diffusion Layers (GDLs) play a vital role in a fuel cell such as (1) water removal, (2) cooling, (3) structural backing, (4) electrical conduction and (5) the transport of gases towards the active catalyst sites where the reactions take place. Conventional carbon paper and carbon cloth GDLs exhibit higher in-plane permeability than through-plane permeability. However, innovative design concepts which may increase the power density of the system require the through-plane gas permeability to dominate over the in-plane gas permeability. In this research, numerical simulations are developed to create an anisotropic resistance profile in the GDL, while maintaining similar performance to conventional GDL designs. The effects of (1) changing the permeability profile in the in-plane and through-plane direction, (2) changing the thickness of the GDL and (3) changing the gas stoichiometry on the current density and pressure drop through the GDL are investigated. Woven gas diffusion layer samples are made in-house, and their gas permeability is tested to match specifications from numerical simulations. The gas permeability of the woven samples is characterized with respect to their structure.

SUBJECT:	M.S. Thesis Presentation

BY:	Terry Caston

TIME:	Monday, April 19, 2010, 11:00 a.m.

PLACE:	Love Building, 109

TITLE:	Design of a Gas Diffusion Layer for a Polymer Electrolyte Membrane Fuel Cell with a Graduated Resistance to Flow

COMMITTEE:	Dr. Tequila Harris, Chair (ME) Dr. Mostafa Ghiaasiaan (ME) Dr. Sankar Nair (ChE)

SUMMARY Due to escalating energy costs and limited fossil fuel resources, much attention has been given to Polymer Electrolyte Membrane (PEM) fuel cells. Gas Diffusion Layers (GDLs) play a vital role in a fuel cell such as (1) water removal, (2) cooling, (3) structural backing, (4) electrical conduction and (5) the transport of gases towards the active catalyst sites where the reactions take place. Conventional carbon paper and carbon cloth GDLs exhibit higher in-plane permeability than through-plane permeability. However, innovative design concepts which may increase the power density of the system require the through-plane gas permeability to dominate over the in-plane gas permeability. In this research, numerical simulations are developed to create an anisotropic resistance profile in the GDL, while maintaining similar performance to conventional GDL designs. The effects of (1) changing the permeability profile in the in-plane and through-plane direction, (2) changing the thickness of the GDL and (3) changing the gas stoichiometry on the current density and pressure drop through the GDL are investigated. Woven gas diffusion layer samples are made in-house, and their gas permeability is tested to match specifications from numerical simulations. The gas permeability of the woven samples is characterized with respect to their structure.