1. High Temperature Electrolysis
Experimental Activities At The
Idaho National Laboratory
Carl Stoots
James O’Brien
J. Stephen Herring
Idaho National Laboratory
Joseph Hartvigsen
Ceramatec Inc., Salt Lake City, UT
Thomas L. Cable
University of Toledo, Cleveland, OH, USA
High Temperature Electrolysis Limiting Factors
Karlsruhe, Germany, June 9 – 10, 2009
2. Overview
• INL HTE is funded by the US DOE Nuclear Hydrogen Initiative (NHI)
• The goal of the NHI is to demonstrate the economic, commercial-scale
production of hydrogen using nuclear energy.
• INL is lead lab under the NHI for studying HTE
• Historically we have concentrated on SOEC designs from Ceramatec Inc.
• With increasing interest in H2 production, we have tested more designs from
various vendors
• My talk – overview of experimental activities at INL with some Lessons Learned
Rolls Royce Fuel Cell Systems
Typical Ceramatec SOEC Stack
NASA BSC Stack
Stoots, HTE Limiting Factors, Karlsruhe, 2009
3. Electrolysis Experimental Activities
Button cell testing
Bench scale test stands
Bench Scale
different cell designs & vendors Multi-cell (Stack) Testing
cell material performance
long term performance -- degradation ILS Facility (15kW)
Integrated Laboratory Scale (15kW)
BOP issues
• thermal management / heat recuperation
• H2 recycle
multi-stack manifolding / interconnects
assess technology readiness
Stoots, HTE Limiting Factors, Karlsruhe, 2009
4. INL Bench Scale Electrolysis Test Apparatus
(Button Cell)
To Roof
Cooling Vent
Water
Air
T
T T
T T
Nitrogen
T P H H P
T T
Hydrogen Ts Ts
T
V
D I Water SV
Ts I T
T
V
Bench Scale Capabilities
INL can simultaneously test:
• two button cells
• two stacks
• special stand for single cell testing
Stoots, HTE Limiting Factors, Karlsruhe, 2009
7. NASA Bi-Supported Cell (BSC)
Construction:
• Structurally symmetric
• Electrolyte supported by both
electrodes
• Electrodes made by freeze casting and
infiltration (nitrate solution)
• YSZ scaffolding
• Graded porosity
• Ni cathode
• LSF anode
• YSZ electrolyte
• High power-to-weight ratio (1 kW/kg?)
Stoots, HTE Limiting Factors, Karlsruhe, 2009
8. NASA BSC Sweeps
1.4 Initial Sweep 1
Initial Sweep 2 Inlet Dew Point T = 50 C
1.3 Sweep at 20 hours
Sweep at 40 hours
Voltage (V)
1.2 Sweep at 80 hours
1.1
1
0.9
Inlet Dew Point T = 62 C
0.8
T = 850 C
furnace
0.5
H = 50 sccm Inlet Dew Point T = 50 C
2,inlet
0.4 N = 350 sccm
ASR (Ωcm )
2
2,inlet
0.3
0.2
0.1
0
Cell area = 2.25 cm2 0 0.2 0.4 0.6 0.8 1 1.2 1.4
2
T = 850 C Current Density (A/cm )
H2,inlet = 50 sccm
N2,inlet = 350 sccm
Tdp,inlet = 50 C, 62 C
yH2O,inlet = 0.35
Stoots, HTE Limiting Factors, Karlsruhe, 2009
9. NASA BSC Long Duration Test
2.6 0.45
ASR
2.5 0.4
T = 850 C
Cell area = 2.25 cm2 2.4
furnace
V = 1.2 V
ref 0.35
T = 850 C Inlet Dew Point = 62 C
ASR (Ωcm )
Current (A)
H = 50 sccm
2
H2,inlet = 50 sccm 2.3 N = 350 sccm
2 0.3
N2,inlet = 350 sccm
2
Sweep
Tdp,inlet = 50 C, 62 C 2.2 0.25
Sweep
Added insulation to valves
Sweep
yH2O,inlet = 0.35
Temporary shut down
Lost power
Current (A)
2.1 0.2
2 0.15
0 100 200 300 400
Elapsed Time (hours)
Experimental disruptions affect degradation
• Erratic steam flow due to condensation
• Power losses
• Thermal transients
Stoots, HTE Limiting Factors, Karlsruhe, 2009
10. Typical Steam Electrolysis Stack Test
Ceramatec 10 cell, 20cm x 20cm
Stack Voltage (V)
14 2
H Production (dew points) 8000 15 Stack T #1 (C) ASR (Ωcm ) 830
2
H Production (current) Stack T #2 (C)
2
13 7000
Stack T #3 (C) 820
Stack
H2 production measured by:
Stack Internal Temperature (C)
12 6000
Stack Operating Voltage (V)
Stack Operating Voltage (V)
Voltage
H Production Rate (sccm)
Stack
2
Voltage 10 810
• Change in dew points 11 5000
ASR (Ωcm )
2
H
• Cell current 10
Production
2
4000 800
Measurement of internal stack 9 3000
5 790
temperatures 8 2000
780
7 1000
Per-Cell ASR
6 0 0 770
0 20 40 60 80 100 0 20 40 60 80 100
Stack Current (A) Stack Current (A)
Stoots, HTE Limiting Factors, Karlsruhe, 2009
11. Typical Steam Electrolysis Stack Test
Ceramatec 10 cell, 10cm x 10cm
15
10 Shunt Current (A)
Vint #1
Vint #2
Vint #3
Vint #4
Power Supply Voltage (V)
Stack Operating Voltage (V)
5 ASR
0
50 100 150 200 250 300
Elapsed Time (hrs)
Humidifier performance erratic -- humidifier float valve failed and had to be replaced.
Stoots, HTE Limiting Factors, Karlsruhe, 2009
12. INL 15 kW Integrated Laboratory Scale Test
Designed to study BOP issues:
• thermal management
• heat recuperation
• H2 recycle
• multi-stack gas manifolding
• multi-stack electrical interconnects
• technology readiness
Stoots, HTE Limiting Factors, Karlsruhe, 2009
13. INL 15 kW Integrated Laboratory Scale Test
Full operation – September 2008
• 3 parallel semi-independent loops
• H2 recycle
• heat recuperation
Stoots, HTE Limiting Factors, Karlsruhe, 2009
15. INL 15 kW Integrated Laboratory Scale Test
Safety: One electrical disconnect point for entire experiment
Stoots, HTE Limiting Factors, Karlsruhe, 2009
16. INL ILS Data Acquisition and Control
• Software written in-house using LabView
• Lesson learned – high bias voltage problems
• 2 National Instruments SCXI signal measurement / conditioning systems
• Isolate high bias voltage measurements from others
• 233 I/O channels
Stoots, HTE Limiting Factors, Karlsruhe, 2009
17. INL H2 Recycle Components
• Double-diaphragm H2 recycle pump
• Feed-back controlled via computer
• User-selectable product recycle split
• H2 recycle storage tank
• Condensation in pressurized H2 product is important
Stoots, HTE Limiting Factors, Karlsruhe, 2009
18. INL ILS Modules
• Modules provided by Ceramatec Inc.
• Each cell is 10cm x 10cm (8cm x 8cm active area)
• Module comprised of 4 60 cell stacks
• 3 modules (total of 720 cells)
• Stacks are electrically interconnected every 5th cell
Stoots, HTE Limiting Factors, Karlsruhe, 2009
19. Final Installation Of Cells
240 cells plus manifolds are heavy!
Module measurements include voltages, currents, temperatures
Stoots, HTE Limiting Factors, Karlsruhe, 2009
20. INL ILS Heat Recuperation Design
• Internally manifolded, plate-fin design
• 2 heat exchangers per module
• One for steam hydrogen
• One for air sweep
• Heat recuperation reduced total electric
heater power requirements by half
Example CFD calculation for INL
heat recuperation concept
Stoots, HTE Limiting Factors, Karlsruhe, 2009
21. Three Module ILS Results
4 20 6 20
Electrolysis Power (Peak = 18kW) 3
Peak 5.7 Nm /hr
Mod 1 ASR
3.5
5 Mod 2 ASR
H Production Rate (Nm /hr)
H Production Rate (Nm /hr)
3 15 Mod 3 ASR 15
2
3
Electrolysis Power (kW)
Per-Cell ASR (Ωcm )
4
2.5
ASR (Ωcm )
2
Module 3 Per-Cell ASR
2 10 3 10
Module 2 Per-Cell ASR
1.5 Module 1 Per-Cell ASR
3
2
2
1 3 5 5
2
H Production Rate (Peak = 5.7 Nm /hr) 3
2
H Production (Nm /hr)
2
1
0.5
0 0 0 0
16 17 18 200 400 600 800 1000
Elapsed Time (hrs) Elapsed Time (hrs)
• 18 kW peak electrolysis power
• 5.7 Nm3/hr peak H2 production rate
• Ran for 1080 hours
• Condensation in H2 MFCs caused problems for first ~500 hours -> degradation
• Proper design and operation of BOP important for cell performance.
• Electrolyser cell performance degradation remains problem.
Stoots, HTE Limiting Factors, Karlsruhe, 2009
22. Steam Electrolysis Experimental Status
• Studying electrolysis degradation mechanisms
through bench scale testing
– Dr. O’Brien will speak more about this
• Continuing to characterize performance of cells
from various vendors
Stoots, HTE Limiting Factors, Karlsruhe, 2009
24. Coelectrolysis H 2O + CO2 ⎯electricity⎯ → H 2 + CO + O2
⎯ ⎯ ,heat ⎯
2H 2O ⎯electricit⎯⎯→ 2H 2 + O2
⎯⎯ y, heat Steam electrolysis
2CO2 ⎯electricit⎯ → 2CO + O2
⎯⎯ y, heat⎯ CO2 electrolysis????
CO2 + H2 ⎯ CO+ H2O
⎯→ Reverse shift reaction
• Smaller/lighter (more mobile) molecules of H2-H2O pair could favor steam electrolysis
– Our Area Specific Resistance (ASR) measurements support this:
• ASRcoelectrolysis ~ ASRH2O
• ASRdry CO2 > ASRH2O
• Seems that:
– H2O consumed in electrochemical reaction
– CO2 consumed in RSR
• Dry CO2 electrolysis is not desirable
– High ASR
– Possibility of further reduction of CO to C
Stoots, HTE Limiting Factors, Karlsruhe, 2009
25. Steam vs. Coelectrolysis ASRs
14
CO Electrolysis
2
~ 3.84 Ωcm
2
13 ASR
CO2
Stack Operating Voltage (V)
12
Same stack
11
800 C operating temperature
H O Electrolysis
10 2
~ 1.36 Ωcm
2
ASR
H2O
9 H O/CO Coelectrolysis
2 2
~ 1.38 Ωcm
2
ASR
H2O/CO2
8
7
6
0 5 10 15 20 25
Stack Current (A)
• Dry CO2 ASR significantly higher than steam ASR
• Stack performance same for steam electrolysis or coelectrolysis
• Explanation (as stated earlier):
• H2O consumed in electrochemical reaction
• CO2 consumed in RSR
Stoots, HTE Limiting Factors, Karlsruhe, 2009
26. Typical Coelectrolysis Stack Results
20
Inlet CO2
H
2
15
Mole % (Dry Basis)
10 Experimental Results
CO
2
Inlet H2
5
CO
Inlet CO
0
0 2 4 6 8 10 12
Model Results
Electrolysis Current (A)
• At zero current (no electrolysis)
• CO2, H2 consumed
Reverse shift reaction
• CO produced
• Yield of syngas increased linearly with current
• oxygen is removed from gas mixture
• Good agreement with INL-developed coelectrolysis model
Stoots, HTE Limiting Factors, Karlsruhe, 2009
27. Coelectrolysis With Subsequent Methanation
100
80 Ceramatec extended coelectrolysis with
downstream methanation reactor
CH • 18mm x 1.5m tube
60 4
CO
• Commercial steam reforming
catalyst (R-67R, Haldor Topsoe)
CO
40 2 • Outer sleeve to reduce axial
N
2 temperature gradient
H
20
2 • Reactor T = 300 C
• 40% - 50% CH4 (by volume)
produced
0
Test 3, Methanation Outlet
Test 1, Methanation Outlet
Test 4, Methanation Outlet
Test 2, Methanation Outlet
Test 5, Methanation Outlet
Test 1, Stack Outlet
Test 2, Stack Outlet
Test 4, Stack Outlet
Test 1, Stack Inlet
Test 4, Stack Inlet
Test 5, Stack Outlet
Test 5, Stack Inlet
Test 2, Stack Inlet
Test 3, Stack Inlet
Test 3, Stack Outlet
Stoots, HTE Limiting Factors, Karlsruhe, 2009
28. Coelectrolysis Experimental Status
• Designing and constructing an integrated demonstration
– Syngas via electrolysis
– Methane via methanation of syngas
– Liquid synfuel
• Methanol
• Fischer-Tropsch liquids
Stoots, HTE Limiting Factors, Karlsruhe, 2009
