1. Innovative Solid Oxide Electrolyser Stacks for Efficient and Reliable Hydrogen production
Towards durable and efficient high temperature
steam electrolysis: the RelHy project
Florence Lefebvre-Joud

2. Concept of RelHy
RelHy Integration of
25-cell stack optimised materials and
prototype, innovative design in a
operated at reliable and efficient
800°C laboratory electrolyser
prototype
d
te
en
m 5-cell
tru
I ns Stacks
Design innovations
Thermo mechanics, Tightness,
SRUs Water management
State of the Art
• Good cells Cells Materials optimisation
• No compromise Durable electrodes/electrolyte, Sealing,
Material compatibility and stability,
in stacks nor SRUs
Cost effective materials and processes
between durability
and efficiency
constituting a bridge between current good performing cells and reliable and
efficient SOEC stack prototype operated at 800°C with cost effective materials.
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 2

3. SoA: Main results of Hi2H2
At the single cell level:
-High performances obtained on
SOFC cells operated in the
electrolysis mode
(ex: 2 A.cm-2 at 1.4V at 850°C)
-Low degradation rate obtained
up to 1500 hrs: ~3% per 1000 hrs
at -0.25A/cm² and -0.5A/cm² ,
800-850°C and absolute humidity
up to 70%.
-Degradation rate observed to
decrease with decreasing the
current density and with increasing
i-V curves obtained at DTU-Risoe on
5x5cm2 solid oxide cells
temperature.
Compromise between the cell
M. Mogensen, S. H. Jensen, A. Hauch,
I. Chorkendorff, and T. Jacobsen. Lucerne (2006). performance and its durability required
Jensen, S. H., Larsen, P. H., and Mogensen, M.
Inter. J. Hydrogen Energy (2008).
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 3

4. SoA: Main results of Hi2H2
At the Single Repeating Unit and short stack levels:
-Degradation rate ~ 10% per 1000hrs obtained with complete SRU
at -0.5A/cm² and 850°C (i.e. x3 compared to single cells)
-Degradation rate ≥ 15% per 1000hrs obtained with 5-cell SOEC Stack
at -0.3A/cm², 800°C, 50% absolute humidity and 50% steam to H2 conversion rate
over test duration of 2000 hrs.
-Adding a coated interconnect to the O2electrode lower cell performance and
lower the degradation rate of the cell
Major influence of stack environment
on cell performance and durability
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 4

5. SoA: Results at CERAMATEC / INL
Ageing curve at 800-830°C
Degradation rate ~ 10% per 1000hrs
25-cell Ceramatec Stack
Similar trends obtained in the US
C. Stoots, J.E. O’Brien, G.L. Hawkes, J.S. Herring, program on larger stacks
J.J. Hartvigsen, Workshop on HTE, Roskilde, Denmark, 2006
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 5

6. SoA: What about SOFC
performance/durability compromise ?
TOFC 75 cell stack concept
• SOFC stacks 1 - 10kW currently
tested with continuously increasing
performances and durability
(Real SOFC project, SECA prog., etc.)
• Ex: TOFC short stack operated
13000 hrs with an overall voltage
degradation rate ~ 1% per 1000 hrs,
• Ex: TOFC 50 or 75-cell stacks (≥1 kW)
Development of metallic interconnects
tested at FU up to 92% with with ceramic coating: ASR~0.5Ω.cm-2
degradation rates below 0.5% per
1000 hrs, especially by improvement
of metal alloy interconnects and
coatings
Major progresses achieved regarding Short stack ageing test
performance / durability compromise for 13000hrs
in SOFC environment
I.C. Vinke, R. Erben, R-H Song, J. Kiviaho Lucerne (2006)
N. Christiansen, J.B. Hansen, H. Holm-Larsen, M. Linderoth, P.H. Larsen, P.V. Hendriksen, M. Mogensen Lucerne (2006)
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 6

7. Ambition of the RelHy projet
RelHy
25-cell stack
Integration of
optimised materials and
• Take advantage of SOFC
prototype, innovative design in a
reliable and efficient
know-how (cell materials,
operated at
800°C laboratory electrolyser metallic interconnects and
prototype
nt
ed ceramic coating, seals, etc.)
e
m 5-cell
ru
I n st Stacks • Transfer the SOFC
Design innovations
Thermo mechanics, Tightness,
optimisation methodology to
SRUs
State of the Art
Water management
SOEC
• Good cells Cells Materials optimisation
• No compromise Durable electrodes/electrolyte, Sealing,
Material compatibility and stability,
in stacks nor SRUs
Cost effective materials and processes
between durability
and efficiency
Acheive high cell performances at 800°C
(~0.03 gH2/cm2/hr, i.e. ~ 1 A/cm2 at ≤1.5V with water conversion >60% )
Decrease degradation rate of SRUs to ~1% per 1000 hr.
Integrate most promising materials and design innovations at laboratory
scale in a 25-cell electrolyser stack prototype to be operated until the
end of the project.
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 7

8. HTSE specifications in 2 cases
coupled to nuclear and to renewable energy
Nuclear Wind
Short Medium Short Medium
Degradation (µ/h) 10 5 15 5
0,7% per 1000hrs at 1.5V
Lifetime (hrs) 10 000 20 000 16 000 40 000
Thermal cycles/year 2 5 7 14
Voltage/cell (V) 1.5 1.45 1.7 1.55
Current (A/cm2) 1.5 2.0 1.0 1.5
Pressure max (bar) 50 50 20 30
Active Area (cm2) 400 800 300 600
Start up from 600 C <4h < 4h <2 < 1h
Turn down to 20 % ? ? < 2 min. < 30 sec.
Pertinence of RelHy target: step from
current SoA towards industrial application
(Under pressure operations to be addressed)
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 8

9. Approach and project
structure
Testing &
Material Prototyping
Analysis
RelHy
Innovative
Laboratory
Modelling and simulation Electrolyser
Prototype
Competitiveness assessment
Key words: significance and reproducibility of results between partners
common single repeating units (SRUs) and short stacks
common testing and analysing protocols
definition of a reference performance/durability level to compare to
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 9

10. Reference material selection
• Cell materials – for the 2 geometries ESC and CSC
ESC (ECN) CSC (DTU Risoe)
– Electrode H2 : Ni-CGO - Electrode H2 : Ni-YSZ
– Electrolyte : 3YSZ - Electrolyte : 8YSZ
– Electrode O2 : YDC-LSCF - Electrode O2 : YSZ-LS
– Active surface : 100 cm² - Active Surface : 100 cm²
•Interconnects and coating • Seals
Crofer + LSM coating on the O2 side Pre-sintered glass bars for
and NiO coating on the H2 side reproducibility during assembly
LSM coating
oxidant side
NiO coating fuel side
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 10

11. SRU and short stack
development
Criteria for SRU geometry:
• Able to integrate ESC and CSC
• « Easy » to assemble
• « Easy » to model upper interconnect
• Close to standard TOFC geometry
cell (120mm by 120mm)
pre-sintered
Short stack: glass bars
• Based on TOFC Alpha standard
mica foil
design,
• Integrates CSC (DTU Risoe)
• Modified to integrate ESC from
lower interconnect
ECN as well (150mm by 150mm by
10mm) metallic bars for
current distribution
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 11

12. SRU ready for testing
H2/H2O side
Air side
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 12

13. Testing protocol definition
• Heating, Sealing and Ni reduction following cell manufacturer recommendations
• Test start-up
– OCV stabilisation at 800°C under H2 with 3 vol.% H2O
• Operation in fuel cell mode at 800°C to check SRU performance
– EIS at OCV , j-V curves and EIS = f(j)
• Operation in Electrolysis Mode at 800°C:
– Change of humidity 50 vol.% Hum (H2 10%/N2 40%) and stabilisation at OCV,
– EIS at OCV, j-V curves V≤1.5V, EIS = f(j),
– Change of humidity 70 vol.% Hum (H2 10%/N2 40%) and stabilisation at OCV,
– EIS at OCV, j-V curves V≤1.5V, EIS = f(j),
– Change of humidity 90 vol.% Hum (H2 10%/N2 40%) and stabilisation at OCV,
– EIS at OCV, j-V curves V≤1.5V, EIS = f(j),
– Back to 50 vol.% Hum to change operation temperature to 750°C
• Operation in Electrolysis Mode at 750°C
• Operation in Electrolysis Mode at 850°C:
• Durability test at 800°C (-1 A/cm2 under 90 vol.% Hum/10 vol.% H2)
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 13

14. Test matrix
Partner 1 Partner 2 Partner 3 Partner 4
Reference test Campaign (on going)
- Reference ESC - Reference ESC - Reference CSC - Short stack with
- Reference CSC + ageing - Reference CSC CSC + ageing
+ ageing - with Sh. Stack - Short stack with
- - coating ESC + ageing
- Reference ESC
with Sh. Stack
coating
Optimisation test campaign: with effect and reproducibility measurement on:
- Cathode material
- Electrolyte material
- Coating material
- Sealing material
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 14

15. ESC – Results in the SOFC mode
1,2 0,35
0,3
1
0,25
0,8
P (W.cm-2)
0,2
E (V)
0,6
0,15
0,4
0,1
800°C,
0,2
Air=1200 mL/min, 0,05
H2=1200 mL/min
0 0
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
i (A.cm-2)
Satisfactory tightness
Satisfactory cell ASR (0.9 Ω.cm2 @ 0.7 V)
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 15

16. ESC – First Results in the HTE mode
1,6
50% H2O-10% H2-40% N2
1,5
70% H2O-10% H2-20% N2
1,4
1,3
90% H2O-10% H2
E (V)
1,2
1,1
1
800°C,
Air=1200 mL/min, 0,9
H2O/H2/N2=1200 mL/min
0,8
I ( A.cm-2) -0,8 -0,6 -0,4 -0,2 0
i (A.cm-2)
OCV in agreement with pH2O
ASR ranging between 0.8 and 0.9 Ω.cm2 @ 1.32 V
First results not far from RelHy target on performance
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 16

17. ESC – Summary of First results in
the HTE mode at 800°C
Fuel Utilization /
ASR (ohm.cm2) Water conversion
Mélange @ H2 Production Production H2
Qtot=1200 @
0.7V SOFC @ 1.32V @ 1.5V
mL/min 0.7V SOFC,
1.32V EHT
1.32V et 1.5V
SOFC 100% H2 0.9 ± 0.01 25%
50%H2O - 50 A 70 A
EHT 0.86 ± 0.03 62% - 87%
10%H2- 40%N2 18.7 mg/cm2/h 26.2 mg/cm2/h
70%H2O - 53 A 75 A
EHT 0.84 ± 0.01 47% - 67%
10%H2- 20%N2 19.8 mg/cm2/h 28 mg/cm2/h
90%H2O - 56 A 80 A
EHT 0.77 ± 0.02 39% - 55%
10%H2 20.9 mg/cm2/h 29.9 mg/cm2/h
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 17

18. Conclusions
RelHy project: aims at reaching a pertinent compromise between
performance and durability
Quantified targets in agreement with industrial specifications in two cases
(nuclear and renewable coupling)
Experimental tools (SRUs and short stacks), protocols and test matrix
developed and available
Reference performances and reproducibility being established
Modelling tools from the microstructure level to the complete SRU level
under construction
Material developments (cathode, electrolyte, interconnect coating and
seals) for second iteration under progress
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 18

19. ☺Acknowledgment to the « RelHy team »
Gislaine Ehora and Jacob Bowen at DTU Risoe
Jan Peter Ouweltjes and Bert Rietveld at ECN
Annabelle Brisse and Mohsine Zahid at EIfER
Qiong Cai and Nigel Brandon at Imperial College
Thomas Nietsch at Helion
Jens Ulrik Nielsen at TOFC and
John Boegild Hansen at Haldor Topsoe
Marie Petitjean, Hervé Sassoulas, Gatien Fleury, ….. at CEA
3rd International Workshop on High Temperature Water Electrolysis / Karlsruhe Germany / 9-10 June 2009 19