Visualization of Transport in Fuel Cell Porous Media

An Alternative Energy Technology Topic

Advisors:Dr. E Caglan Kumbur & Dr. Minjun Kim

Peter CarrionDean Galarowicz

Karl Gutwein-GuentherAnthony Salvatore

Trevor Smith

OverviewIntroduction

Fuel Cell BackgroundProblem StatementMethod of Solution

Task 1: FIB/SEM Imaging of MPLTask 2: Resin Impregnation of GDLTask 3: MicroCT Imaging of GDL

Summary of ResultsFIB/SEM Imaging of MPLMicroCT Imaging of GDL

Other ConsiderationsEnvironmental and Societal ImpactsEconomic AnalysisProject Management and Timeline

Questions

Electrochemical devices – convert chemical energy directly to electrical energy

Used for power generationStationaryMobile

Different TypesAlkalinePhosphoric AcidSolid OxideMolten CarbonatePolymer Electrolyte (PEFC)

http://blog.fuelcellstore.com/wp-content/uploads/2008/03/purecell_200.jpg

http://www.khulsey.com/dp_gm_hydrogen-fuel-cell_cutaway.jpeg

IntroductionFuel Cells

Gas Diffusion Layer (GDL)

Fuel

Oxidizer

Exhaust

Electrolyte

GDLMPLCL

Structure: PTFE coated carbon

fibers. (5-30% by wt) Weave and Paper Conductive (50-200 S/cm)

Function: Reactant transport to CL Thermal insulation for CL Mechanical support for

electrolyte/CL Properties:

Porosity: 0.7-0.9 Pore Size: 1 -50 μm Thickness: 175-400 μm

(BAZYLAK – Water Visualization in Fuel Cells – A Review)

Cloth

Paper

IntroductionFuel Cell Components

Microporous Layer (MPL)

Fuel

Oxidizer

Exhaust

Electrolyte

GDLMPLCL

Structure: Carbon PTFE slurry Conductive

Function: Serves as moisture barrier

between CL and the GDL Improves conductivity Highly hydrophobic

Properties: Pore Size: 0.01-0.5μm Thickness: 5-100 μm 5-20% PTFE content SEM image showing profile of MPL

(Kumbur)

IntroductionFuel Cell Components

Figure 1 Polarization Curve for PEM fuel cell with and without flooding losses (Mench 2008)

IntroductionPolarization Curve

Volt

ag

e

Current

Problem StatementThe exact water transport mechanism within

the GDL and MPL is not fully understood.

There are prohibitive limitations to real time visualization of these components during steady-state operation.

Method of SolutionTask 1: FIB/SEM Imaging of MPL

Selection of resin:Procedure 1: Large tube encompassing entire

sampleProcedure 2: Small tube centralized injectionProcedure 3: Heated flexible pressure vessel

Method of SolutionTask 2: Resin Impregnation of GDL

Quantifying resinCalculations:Resin ρ (g/mm^3)0.001043GDL ρ (g/mm^3)0.000213MPL ρ (g/mm^3)0.000993 Sample Volume = Length * Height * ThicknessSample wo/ MPL = sample volume * .86MPL Weight = (sample volume-sample wo/ MPL)*MPL ρGDL Weight = weight-MPL WeightResin Surface V = Length * Height * (thickness after resin-thickness before resin)Resin Volume = ((weight after resin-weight before resin)/Resin ρ)-resin surface

volumeVoid Volume = sample wo/MPL*.8% void filled = resin volume/void volume

Method of SolutionTask 2: Resin Impregnation of GDL

Large Tube

Large Tube w/ heated resin (30˚c)

Large tube w/ heated resin

(89.4)

Heated pressure chamber

Trial 1 Trial 2 Trial 3 Trial 5 Trial 4 Trial 6

53.1% 54.8% 60.6% 67.2% 64.4% 67.3%

The plan:Selection of the wetting fluid

The wetting fluid chosen will have similar material properties to water

A small specimen of carbon paper will be impregnated with the selected wetting fluid

Use of MicroCT to provide a full 3D internal structure and composition of specimens

Method of SolutionTask 3: MicroCT Imaging of GDL

Summary of ResultsFIB/SEM Imaging of MPL

Summary of ResultsMicroCT Imaging of GDL

www.technacular.com/2007/04/19/car-of-the-future-toy-version/

Improvements in fuel cell efficiency could lead to acceptance of fuel cell technology in automobiles

Reduction of greenhouse gases

Increase of on-site or local energy production

Building a hydrogen economy to support fuel cell demand

www.idatech.com/Products-and-Services-ElectraGen-System2.asphttp://

www.hydrogenforecast.com/ArticleDetails.php?articleID=300

Other ConsiderationsSocietal and Environmental Impact

Increased durability and reliabilityEnable PEFC use in vehiclesGreater efficiency than ICE, lower cost of energy

vs useful workMinimum Cost

Resource Cost Time Total CostFIB/SEM $85/hr 6 hrs $510.00

MicroCT - Imaging $82.90/use 4 hrs $82.90

MicroCT - Reconstruction $16.58

8 hrs $16.58

Resin $50.00

N/A $50.00

Hard Drive $100.00 N/A $100.00

Total $759.48

Additional Costs

MicroCT Total $99.48 2 Times $198.96

Misc Expenses $150.00 $150.00

Total $1,108.44

Other ConsiderationsEconomic Analysis

Other ConsiderationsTime Line