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  • 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
  • 5. INL Bench Scale Electrolysis Test Stands Stoots, HTE Limiting Factors, Karlsruhe, 2009
  • 6. INL Bench Scale Electrolysis Test Stands 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
  • 14. INL 15 kW Integrated Laboratory Scale Test 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
  • 23. Coelectrolysis Experimental Activities 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