Numerical Analysis of Critical Performance Parameters of the Sulzer Hexis Fuel Cell Stack

Pascal Held, Thomas Hocker

CCP – Center for Computational Physics ZHW – University of Applied Sciences Winterthur Winterthur, Switzerland

Jeannette Frei, Jan Hoffmann

Sulzer Hexis Ltd.

Winterthur, Switzerland

Introduction

• 1998 the CCP starts with SOFC simulation •

Goal:

support of the HEXIS SOFC development with “virtual experiments” • Partners: - Simulation - Software validation - Experimental setup - Hardware development - Program support - GUI development • The Project is supported by the Swiss Commission for Technology and Innovation (KTI) Fuel Cells - Science and Technology 2004

Contents

• Environment • Volume Averaging Method • Model • Sensitivity Analysis • Results Fuel Cells - Science and Technology 2004

Current collector (MIC) Air after burning zone

Hexis Fuel Cell System

Cell System HXS 1000 Premiere

electrolyte (YSZ ceramic) Fuel

Stack

Fuel Cells - Science and Technology 2004

Volume Averaging Method

Effective Parameters Fuel Cells - Science and Technology 2004

Vertical Temperature Gradient

Fuel Cells - Science and Technology 2004

Horizontal Temperatur Gradient

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MIC-Structure

VAM Applied to SOFC

Repetitive MIC-Element Simulation of Transport Phenomena Effective Parameters •

k eff

• 

eff

• 

eff

• 

eff

(

T,j q ,x H2 ,...

)

2D Effective Model:

• Reduced Geometric Complexity • Less computational effort Fuel Cells - Science and Technology 2004

Incorporation in 2D-Model

Comparing 3D with and without details Solving 3D with details Input: Nubs/element Sigma Kappa Permeability Diffusion Database: multi.sfc

MIC Gas Properties Database: reaction.sfc

Reaction prop. el. Cond.

th. Cond.

z-direction th. Cond.

x-direction Perm Diffusion Diffusion nubs Reaction Output: effective Parameters for 2D-Model Fuel Cells - Science and Technology 2004

Parameter Variation

Contact Resistance Different MIC-Designs

Manganite R Cont,Cath Nubs MIC

Direct Hole Original

Fuel Cells - Science and Technology 2004

Sensitivity Analysis

• Definition: Investigation into how projected performance varies along with changes in the key assumptions on which the projections are based. • Goals: Identify parameters of major importance to a) b) find out if more accurate measurements required concentrate on parameters with optimization potential Fuel Cells - Science and Technology 2004

Procedure

• Define upper and lower boundaries for input parameters (input parameters: material properties, geometries, operation condition) • Evaluate output variables for all possible combinations of input parameters • Statistical analysis of output variables Fuel Cells - Science and Technology 2004

Input Variables

Example:

• Free Volume in Anode/Cathode (Diff_x) • Ion conductivity of Electrolyte (SigmaTKx) • Contact Resistance (Contact_x) DesignEase Screenshot Fuel Cells - Science and Technology 2004

Required Simulations

DesignEase Screenshot Follows 2 n -law Fuel Cells - Science and Technology 2004

Output Variables

• According to optimization goals For example: • Area specific resistance (ASR) • Temperature Fuel Cells - Science and Technology 2004

Parameter F (contact resistance cathode) has a major impact on overall performance

Results

Fuel Cells - Science and Technology 2004

Further Information

http://www.ccp.zhwin.ch

CCP-ZHW Sulzer HEXIS Ltd.

http://www.hexis.ch

NM GmbH

http://www.nmtec.ch

NMSeses

NMSeses (public domain version) with reduced capabilities is available under http://www.nmtec.ch

Fuel Cells - Science and Technology 2004