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1 Solid Oxide Fuel Cells and Gas Separation Membranes A.Hagen, P.V. Hendriksen, M. Søgaard Fuel Cells and Solid State Chemistry Division Risø DTU

2 Outline Background Motivation Combination of Energy Conversion Technologies Solid Oxide Fuel Cells Gas Separation Membranes Summary and Outlook 2 Risø DTU

3 Water Sun Wind Biomass Energy supply How can we satisfy our needs for energy in the right forms and at the right times with what nature offers? Energy need Heat 3 Risø DTU Fuel Electricity

4 Background Biomass Gasification Fuel Cells Membranes Heat Electricity 4 Risø DTU

5 Biomass: Gasification Gasification of biomass to CO and H 2 High temperature process Use of waste (wood chips, organic waste) Efficiency i of wood for electricity exceeds 25% Potential for increase of electrical l efficiency i by use of fuel cells and oxygen enriched gasification! Carbon capture! SOFC OTM Viking gasifier at Risoe DTU 5 Risø DTU

6 Combination: Gasification SOFC- Membrane Increase of total efficiency: SOFC convert fuel to electricity with higher efficiency than conventional technologies Oxygen rich gasification gives a gas with lower nitrogen content (less diluted fuel) New option: Carbon capture Challenges: Changing composition according to used biomass Load fluctuations Impurities, minor components in gasification gas: Sulphur containing, ammonia, higher hydrocarbons, etc. 6 Risø DTU

7 Solid Oxide Fuel Cells: SOFCs Fuel derived from conventional and sustainable sources Electrical power and high value (e.g., methane, natural gas, heat hydrogen) Solid oxide fuel cells (SOFCs) Higher efficiency than conventional power generation systems Reduction of emissions and pollution (NO x, CO 2, noise) 7Modular Risø DTU concept (from kw to MW)

8 SOFC Working Principle and Main Components CATHODE Catalytic activity for oxygen reduction Gas transport (porosity) Electron- (ion-) conducting O 2 ELECTROLYTE Gas tight O 2 + 4e - 2O 2- (Oxygen) ion O 2- conducting 2H 2 + 2O 2-2H 2 O + 4e - Electronic isolator e - H 2 ANODE Catalytic activity for fuel oxidation Gas transport (porosity) Electron- (ion-) conducting GENERAL Chemical inertness Thermal compatibility Mechanical strength and flexibility Gasification gas 8 Risø DTU

9 SOFCs at Risoe DTU: Generation G2 Risoe DTU has developed several SOFC generations based on ceramic materials, which are tailored for different operating conditions A pre-pilot manufacture line was established using scale-able and economically competitive processes 9 Risø DTU

10 Durability of SOFCs Generation G2 Good initial performance Good durability over thousands of hours in different fuels: Hydrogen, synthesis gas (CO + H 2 ), methane + steam m 2 ity in W/cm Po ower densi Durability tests on 2G, synthesis gas, 75% fuel utilization 750 o C 850 o C Risø DTU Time under current in h

11 Durability of SOFCs Generation G2: H 2 S Impurities 800 cell B CH 4 /H 2 O/H 2 O 700 H 2 /H 2 O tage in mv 600 CH 4 /H 2 O/H 2 O H 2 S H 2 S 1 A/cm 2 Cell vol 500 cell A 2G cell 850 o C, 1A/cm H 2 S Time under current in h Tolerance of 2G SOFCs towards H 2 S impurities in a fuel mainly containing hydrogen and also hydrocarbons (methane) and steam not sufficient 11 Risø DTU

12 SOFC: Improvement of Anode of 2G Cell Impedance analysis, 750 o C, 20% H 2 O 2 ] -Z'' [Ω cm -Z'' [Ω cm 2 ] Cell A (2G) 10,000 Hz 56,000 Hz 790 Hz 110 Hz 19 Hz Fit Cat I Ano I Cat II Diffusion Conversion Cell #A Z' [Ω cm 2 ] Cell B ,500 Hz 43,000 Hz 680 Hz 56 Hz 18 Hz 0.05 Fit Cat I Ano I Cat II Diffusion Conversion Cell #B Z' [Ω cm 2 ] Smaller resistance from anode and smaller electrolyte resistance = Better performing cell 12 Risø DTU Convs. Diff. Electro- Anode lyte Cathode Convs. Electro- Diff. lyte Anode Cathode

13 Durability of SOFCs Generation G2.X with Improved Anode: H 2 S Impurities 800 cell B CH 4 /H 2 O/H 2 O 700 H 2 /H 2 O tage in mv 600 CH 4 /H 2 O/H 2 O H 2 S H 2 S 1 A/cm 2 Cell vol 500 cell A 2G cell 850 o C, 1A/cm H 2 S Time under current in h Tolerance Significantly of improved 2G SOFCs tolerance towards H of 2 S improved impurities 2G in SOFCs a fuel mainly towards containing H 2 S hydrogen impurities and in the also fuel hydrocarbons (methane) and steam not sufficient 13 Risø DTU

14 From Solid Oxide Fuel Cells Oxygen Transfer Membranes O 2 CATHODE Catalytic activity for oxygen reduction Gas transport (porosity) Electron- (ion-) conducting ELECTROLYTE Gas tight O 2 + 4e - 2O 2- (Oxygen) ion O 2- conducting 2H 2 + 2O 2-2H 2 O + 4e - Electronic isolator e - H 2 ANODE Catalytic activity for fuel oxidation Gas transport (porosity) Electron- (ion-) conducting GENERAL Chemical inertness Thermal compatibility Mechanical strength and flexibility 14 Risø DTU

15 Oxygen Transfer Membranes (OTMs) Oxygen is separated from air, transported through a membrane and supplied to partial oxidation of methane Cross section SEM picture of a ceria based membrane 15 Risø DTU

16 OTMs: Performance (Flux) Measurements Economical feasibility Calculations 10 2 Flux [ ml O cm -2 2 min -1 ] V f / [ Flux T = 600C T = 700C T = 800C T = 900C T = 1000C l Ely / [ μm ] Membrane thickness Hydrogen Air 30 µm thick CGO 0.02 atm O 2 CGO 10 atm air 16 Risø DTU

17 Summary Outlook Combination of biomass gasification and SOFC: Potential electric efficiency of +50% through use of a SOFC By using intelligent heat management, high total efficiencies ~ 90% possible Well performing and durable SOFCs developed and demonstrated for several fuels, even in presence of H 2 S impurities Challenge: Tolerance towards other impurities Combination of biomass gasification and OTM: Increase of overall efficiency due to gasification gas with higher energy density (less diluted) Know-how developed for SOFCs can be utilized Promising results regarding performance (flux) and economic feasibility Challenge: Increase of flux and durability 17 Risø DTU

18 Acknowledgements We gratefully acknowledge support from our sponsors: Topsoe Fuel Cell A/S Danish Energy Authority Energinet.dk EU Framework Programmes Danish National Advanced Technology Foundation Danish Research Councils DONG Energy Areva 18 Risø DTU

Electrodes and fuel cells cases and visions

Electrodes and fuel cells cases and visions Peter Holtappels Head of Programme Electrochemistry peho@risoe.dtu.dk Fuel Cells and Solid State Chemistry Division Risø National Laboratory for Sustainable