R. Zaera Universidad Carlos III de Madrid This work has been partially supported by project ENE2008-06683-C03-02 of the spanish Ministerio de Ciencia e Innovación An anisotropic nonlinear FEM model of the inhomogeneous compression of PEMFC gas diffusion layers P. A. García-Salaberri M. Vera R. Zaera Universidad Carlos III de Madrid

Outline Motivation FEM Model Description Validation Results Hypothesis Geommetry Mechanical Charaterization Validation Results Conclusions Future Work Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 1

Motivation Fuel cell assembly Nitta [1] Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 2

Model Description: Geometry Reference geometry Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 3

Model Description: Hypothesis Elastic GDL deformation Large deformation theory Plane strain Non-linear orthotropic properties Imposed through-plane deformation Gasket thickness GDL affected by membrane deformation Hygro-thermal cycling Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 4

Mechanical Charaterization BP → linear elastic, isotropic E = 10 GPa, ν = 0.25 GDL → non-linear elastic, orthotropic Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 5

GDL Mechanical Characterization Ex & Ez Gxy Kleemann et al. [2] Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 6

GDL Mechanical Characterization E y(εy) Ey (Mpa) εy Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 7

Porosity and Diffusivity Fields Porosity field Diffusivity field (e.g. Brugemann correction) Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 8

Non-linear Orthotropic model Model Validation Porosity field Non-linear Orthotropic model Present work Isotropic model Zhou et al. [8,9] Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 9

Model Validation Channel intrusion Lai et al. [7] Present work Kandlikar [6] Present work Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 10

BP Width Ф WBP WBP Intrusion Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 11

GDL Thickness tGDL Ф tGDL Intrusion Similar effect to Gxy Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 12

Orthotropic vs. Isotropic Models Isotropic models may lead to incorrect predictions Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 13

Membrane Swelling (I) Nafion membrane Model parameters → Linear-elasto-plastic with isotropic hardening T and RH dependent properties [10] Model parameters → Homogeneus BP, GDL & membrane temperature Homogeneus RH in the membrane Tassembly = 20ºC RHassembly = 30% Toperation = 85ºC RHoperation = 100% Kusoglu et al. [10] Assembly Operation Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 14

Membrane Swelling (II) Membrane swelling decreases porosity and improves contact resistances during FC operation Operation Assembly Operation Assembly Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 15

Conclusions A non-linear orthotropic FEM model has been developped to study the effects of inhomogeneous compression in PEMFC GDLs during FC assembly and operation Parametric studies Geom. parameters: BP width, GDL thickness Mech. properties: Ex, Ez, Gxy, Orthotrop./Isotropic Isotropic models may lead to incorrect predictions Membrane swelling ↓ porosity and ↓contact resistances during FC operation Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 16

Future Work Evaluate the effect of inhomogeneous GDL compression in fuel cell performance Effect of variable porosity on Effective diffusion coefficients Multiphase transport Water transport in PEMFC CO2 transport in DMFC BP-GDL / membrane-GDL contact resistances Channel obstruction due to GDL intrusion Hygro-thermal membrane loading Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 17

References [1] Nitta (2008) Inhomogeneous compression of PEMFC gas diffusion layers, Doctoral dissertation, Helsinki (Finland). [2] Kleemann, Finsterwalder & Tillmetz (2009) J. Power Sources 190:92–102. [3] Mathias, Roth, Fleming & Lehnert (2003) in Handbook of Fuel Cells–Fundamentals, Technology and Applications, Volume 3: Fuel Cell Technology and Applications, Chapter 46, W. Vielstich, H.A. Gasteiger, A. Lamm (Editors), John Wiley & Sons, Ltd. [4] Matsuura, Kato & Hori (2006) J. Power Sources 161:74–78. [5] Escribano, Blachot, Ethève, Morin & Mosdale (2006) J. Power Sources 156:8–13. [6] Kandlikar, Lu, Lin, Cooke & Daino (2009) J. Power Sources 194:328–337. [7] Lai, Rapaport, Ji & Kumar (2008) J. Power Sources 184:120–128. [8] Zhou, Wu & Ma (2006) J. Power Sources 159:115–1122. [9] Zhou, Wu & Ma (2007) J. Power Sources 163:874–881. [10] Kusoglu, Karlsson, Santare, Cleghorn & Johnson (2007) J. Power Sources 170:345–358. Session 1B – 06/10/2010 P.A. García-Salaberri, M. Vera & R. Zaera – UC3M 18