Multiscale Multiphysics Transport and Reaction Phenomena within SOFCs
Martin Andersson, Department of Energy Sciences,Lund University Agenda Introduction to Fuel Cells Background Multiscale Modeling
Mathematical Model (Continuum scale model) Results (Continuum scale model) Conclusions (Continuum scale model) 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 Introduction - The SOFC Chemistry and Transport Phenomena to be Understood across Disparate Length Scales
SOFC LU/China, NIMTE, 2010 5 5 Multiphyisics modeling Why we need multiscale modeling
Ref [K. Grew, W. Chiu, J. Power Sources 199 (2012) 1-13] Multiscale modeling Nobel Prize
Professor Arieh Warshels work with multiscale modelsdescribing complex chemical system (with focus onProteins was awarded the Nobel Price in 2013. The interest for multiscale modeling is expected toincrease. NIMTE Standard Ni-YSZ Supported Cell
28 % porosity 4x4 cm active area Mathematical Model - Geometry 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 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 Results Hydrogen and Oxygen Distribution Results Oxygen Distribution Results Temperature Results Current density Results Activation polarization Results Concentration polarization Results Electric Potential Results Electron Current Density Conclusion The uniqueness of the FEM model presented in thispaper is the high current density spots The current density increases along the main flowdirection. The increase limited due to consumption ofelectrochemical reactants The significant oxygen mole fraction and electroncurrent density gradient in the direction normal to themain flow direction, caused by the relatively thin cathode(in comparison to the anode), is revealed. Future work Couple continuum scale and microscale models (SOFC)
Phase change and bubble behavior in PEMFC porousmaterial Acknowledgements Swedish Research Council (VR-621-2010-4581)
European Research Council (ERC MMFCs)