1. Multiscale Multiphysics Transport and Reaction Phenomena within SOFCs
Martin Andersson, Department of Energy Sciences, Lund University

2. Agenda Introduction to Fuel Cells Background Multiscale Modeling
Mathematical Model (Continuum scale model)
Results (Continuum scale model)
Conclusions (Continuum scale model)

3. Introduction - To Fuel Cells
The principle dates back to 1838/39
Fuel is directly converted to electrical energy and heat
Environmental friendly (depending on fuel used)
Outstanding electrical efficiency (also for small systems)
Fuel cells are expected to be a key component in a future sustainable energy system
Strategic niche markets will be important for commercialization
Space applications
Leisure applications
APUs

4. Introduction - The SOFC

5. Chemistry and Transport Phenomena to be Understood across Disparate Length Scales
SOFC
LU/China, NIMTE, 2010 5 5

6. Multiphyisics modeling

7. Why we need multiscale modeling
Ref [K. Grew, W. Chiu, J. Power Sources 199 (2012) 1-13]

8. Multiscale modeling – Nobel Prize
Professor Arieh Warshels work with multiscale models describing complex chemical system (with focus on Proteins was awarded the Nobel Price in 2013.
The interest for multiscale modeling is expected to increase.

9. “NIMTE Standard” Ni-YSZ Supported Cell
28 % porosity
4x4 cm active area

10. Mathematical Model - Geometry

11. Mathematical Model Momentum transport
Continuous equation for the porous material and electrodes
Mass transport [O2/N2 + H2/H2O(CH4/CO/CO2)]
Maxwell-Stefan equation, incl. Knudsen diffusion
Heat transport
LTE approach
Conductivity in solid phase
Conductivity and convection in gas phase

12. Mathematical Model Assumptions: 3D Fuel utilization: 76 %
Oxygen utilization: 9 %
Cell voltage: 0.7 V
Co-flow
Fuel defined as 90 % (mole) hydrogen and 10 % water
Inlet temperature: 1000 K

13. Results – Hydrogen and Oxygen Distribution

14. Results – Oxygen Distribution

15. Results – Temperature

16. Results – Current density

17. Results – Activation polarization

18. Results – Concentration polarization

19. Results – Electric Potential

20. Results – Electron Current Density

21. Conclusion
The uniqueness of the FEM model presented in this paper is the high current density spots
The current density increases along the main flow direction. The increase limited due to consumption of electrochemical reactants
The significant oxygen mole fraction and electron current density gradient in the direction normal to the main flow direction, caused by the relatively thin cathode (in comparison to the anode), is revealed.

22. Future work Couple continuum scale and microscale models (SOFC)
Phase change and bubble behavior in PEMFC porous material

23. Acknowledgements Swedish Research Council (VR-621-2010-4581)
European Research Council (ERC MMFCs)