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SOFC Development at GE Global Research
Matt AlingerGE Global ResearchNiskayuna, NY SOFCSOFC
12th Annual SECA WorkshopPittsburgh, PAJuly 26-28, 2011
2SECA Annual Workshop
July 2011
Aligned for growth
GE Capital
Home & Business Solutions
Energy
Oil & Gas
Power & Water
Healthcare
Aviation
Transportation
GE today
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July 2011
Global reach and connectivity
Business Program Offices
Software Sciences & Analytics
Electrical Technologies & Systems
Manufacturing & Materials Technologies
China
India
Germany
O&G
40,000 technologists across GE
Global TechnologyDomains
Technology Center Leaders
Aero-Thermal & Mechanical Systems
Chemistry & Chemical Engineering
Diagnostics & Biomedical Technologies
Appliances WaterLightingEnergy TransportationAviation Healthcare
Brazil
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Global Research annual funding
• Advanced Technology programs
• New ideas
• High-risk/high reward
• Next generation product technology
• Short-term technical challenges
• Joint technology
• Specific customer focus
~$600 M
52%55%
28%
17%
GE business programs
GE corporate programs
External partnerships and gov’t. funded
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Technology Challenges for SOFCs
• Materials set High power densityLow degradation / stable
• Scale-upLarger cellsBigger stacks
• System design & integration Improved design for reliabilityOperability (start-up, shut down, transients, …)
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Presentation Outline
• Materials Set– Cost– Performance– Degradation
• Scale-up– Manufacturing
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Materials Set
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Anode Supported Solid Oxide Fuel CellLayer Function Material Thickness
Air Side
Interconnect Gas & Electron Transport Ferritic Stainless Steel 500 m
Protective Coating Prevent interconnect Cr from poisoning cathode (Mn,Co)3O4 10 m
Cathode Contact Paste
Electrically connect cell with air interconnect (La,Sr)CoO3 100 m
Cathode Air electrode (La,Sr)(Co,Fe)O3 40 m
Barrier Layer Prevent cathode Sr from reacting with electrolyte Zr
GDC(Ce0.8Gd0.2)O2
10 m
Electrolyte Permit O2- transport, prevent air/fuel mixing
YSZ(ZrO2 + 8 mol Y2O3)
10 m
Fuel Side
Functional Anode Fuel electrode NiO/YSZ 20 m
Anode Support Mechanically supports Anode & Electrolyte NiO/YSZ 200 m
Anode Contact Paste
Electrically connect cell with fuel interconnect NiO 100 m
Interconnect Gas & Electron Transport Ferritic Stainless Steel 500 m
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21 atm, 800oC, 64%H2-36%N2, 80% Fuel Utilization (Uf), 0.7V
Significant performance improvementSufficient to meet cost targets, though higher
performance directly impacts stack cost
Performance status
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0
0.25
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0.75
1
Baseline Cost Increased PowerDensity
Low-costinterconnect
Nor
mal
ized
sta
ck c
ost
0.5
W/c
m2 ,
E-Br
ite
0.75
W/c
m2 ,
E-Br
ite
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W/c
m2 ,
441S
S
Stack cost status
Cost reduction through performance improvement and interconnect alloy
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Degradation reduction
-Developed interconnect coating-Stabilized cathode-Validated low-cost interconnect alloy
Degradation mechanisms identified and mitigation
strategies validated
Cost and degradation risk significantly reduced
Engineering solutions exist, however, significant work remains to understand degradation
fundamentals.
800oC, 1.25A/cm2, 441SS
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Location-specific degradation can be measured from embedded gold mesh
(voltage point)
Measurement of location-specific degradation
Steel Interconnect V1
V2
Gold Interconnect
Anode votlage lead
Gold current collectorSteel current collector
V1
V2
Anode
ElectrolyteCathode
Contact paste
Gold mesh
Test Conditions: 800oC1.25 A/cm2
H2+3%H2O
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ASR degradation from power curves
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1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0
F S S 1
F S S 2
F S S 3
A u 1
A u 2
A u 3
ASR
, m
-cm
2
t im e , h
18 m - c m 2 /1 0 0 0 h
63 m - c m 2/ 10 0 0h
7 4 m - c m 2 /1 00 0 h2 5 m - c m 2/ 10 0 0h
8 m - c m 2 /1 00 0 h
15 m - cm 2 /1 0 0 0 h
ASR degradation consistent with traditional cell construction
Test conditions800oC
1.25 A/cm2
H2+3%H2O
ASR from weekly power curves @ 0.7V
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Non-ohmic degradation
Generally indicative of loss of electrochemical
contact
No catalytic activity loss
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FSS 1
FSS 2
FSS 3
Au 1
Au 2
Au 3
A
SRno
n-oh
mic, m
-c
m2
time, h
-2 m-cm2/1000h
35 m-cm2/1000h
39 m-cm2/1000h
3 m-cm2/1000h
-1 m-cm2/1000h
0 m-cm2/1000h
Non-ohmic degradation is nearly zero
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Ohmic Degradation
Measured degradation is nearly all ohmic in nature
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0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0
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A u 1A u 2A u 3
A
SRoh
mic, m
-c
m2
t im e , h
2 0 m - cm 2 /1 00 0 h
28 m -c m 2/ 10 0 0 h
3 5 m - cm 2 /1 00 0 h
2 2 m -c m 2/ 10 0 0h
9m - cm 2 /1 0 0 0 h
1 5 m - cm 2 /1 00 0 h
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Interfacial ASR
Confirms contact resistance data
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A
SRco
ntac
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-c
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time, h
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FSS 1
FSS 2
FSS 3
Au 1
Au 2
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-cm
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time, h
3 m-cm2/1000h
3 m-cm2/1000h
8 m-cm2/1000h
0 m-cm2/1000h
0 m-cm2/1000h 0 m-cm2/1000h
ASR(contact resistance testing)
V
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Manufacturing
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Metal supported cell
Advantages:Integrated anode sealElectrolyte in compressionImproved anode electrical
contactIncreased active areaLower anode polarizationAllows redesign of structures
Challenges:Dense / hermetic electrolytePorous metal substrate degradation
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Low-cost manufacturing
Thermal Spray
Extrusion Lamination
Electrolyte
Electrode Layers
Thin Electrolyte Bilayer
Cutting Sintering Electrode Application
FiringSintered Cell Manufacturing
Leverage GE thermal spray expertise
Sheet Metal Fab Joining
Complete Interconnect
PreSealing StackingAdvantages
Larger area / ScalableSimplified sealingLow Capex / ModularLean Manufacturing
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Cell Manufacturing Processes
Enable larger, thinner cellsExploration of different processes and cell structuresGoal is to demonstrate scalability
Disruptive to stack manufacturing cost structure
Atmospheric Plasma Sprayporous cathode
dense electrolyte
porous anode
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High throughput, many different structures / compositions / formats can be tested
Cell and stack design tailored to deposition processes
Performance reaching sintered cell levels
Scale-up to 4’’ and 12’’ cell on-going
Deposition Technology Progress
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Discontinuous coating Continuous coating
Smooth Anode Development
Minimum thickness required for deposition of a continuous anode on a porous substrate.
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Anode thickness
Ano
de ro
ughn
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on Ni foam Aon Ni foam BSupport ASupport B
0.001
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10
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1000
Anode thickness
Leak
rate
(sc
cm/c
m2)
on Ni foam Aon Ni foam Bblank
Support ASupport B
foam roughness
Anode roughness initially decreases with increasing thickness, then stabilizes to a fairly constant value. Transition is indicative of full foam coverage.
Leak rate decreases with increasing anode thickness until it stabilizes, which is indicative of full foam coverage.
foam leak rate
Minimum thickness established for full foam coverage with smooth anode
Smooth Anode Development
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Smooth Anode Development
Deposition condition developed for smooth anode deposition onto foam support
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1” diameter foam coated with smooth anode. Surface is generally smooth, however a few localized defects can be identified.
Manufacturing defects may impact cell performanceImproved process control for removal
Smooth Anode Development
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Effect of surface asperities on stress-state of thermal sprayed coating
• Asperities cause local stress gradients in electrolyte
• Effect enhanced after anode reduction
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2 mm
5 mm
Top-down view of deposited coating on 1” diameter button cell
Electrolyte optimization
With a smooth anode & control of defects, high quality electrolytes can be deposited.
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Thermal spray heat flux modeling
Thermal heat flux modeling to support large area cell
thermal management
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In-situ measurements in the spray cell permit rapid feedback for development
OCV measurement
OCV mapping can be performed across entire cell
Thermal Imaging
In-situ characterization for thermal sprayed cells
Touch probe
OCV reading Gas feed
Back-heating
Imaging during OCV testing helps in further cell characterization
IR camera image
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Thermal Sprayed Cells (25 cm2)
Optimizing electrodes and electrolyte for improved power density
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Improved structures
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Summary• Identified high-impact fundamental degradation mechanisms and
developed cost-effective mitigation solutions.
• Demonstrated high, stable performance of LSCF-based cathode SOFCs with gold current collectors.
• Demonstrated parabolic power density degradation behavior with ferritic stainless steel (AL441HP) current collectors that is indicative of chromia scale growth.
• Implemented and tested an integrated thermal spray manufacturingsystem for SOFCs.
• Identified anode roughness as a key criteria to enable hermeticelectrolytes.
• Developed thermal spray conditions to produce a smooth fuel electrode (anode) on a porous metal support.
• Demonstrated operational performance on 25cm2 thermal sprayed cells.
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Acknowledgements
• Joe Stoffa, Briggs White, Travis Shultz, Heather Quedenfeld and Shailesh Vora of DOE/NETL
• Funding provided by the US Department of Energy through cooperative agreement DE-NT0004109.
• SECA partners• GE SOFC Team
This material is based upon work supported by the Department of Energy underAward Number DE-NT0004109. However, any opinions, findings, conclusions, orrecommendations expressed herein are those of the authors and do not necessarilyreflect the views of the DOE.