Charge, mass and heat transfer interactions in solid oxide fuel cells operated with different fuel gases—A sensitivity analysis

Nagel, Florian P.; Schildhauer, Tilman J.; Biollaz, Serge M.A.; Stucki, Samuel

doi:10.1016/j.jpowsour.2008.05.044

Cited by 42 publications

(32 citation statements)

References 7 publications

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“…(WGSR, 4), reactions are used to calculate the reaction rates in this work. Other global kinetic models can be found in [31][32]. The catalytic methane steam reforming reaction occurs at the surfaces of the nickel catalysts and is specified as [29,33] (27) where p i is the partial pressure of gas species i, T the temperature, r the reaction rate and AV the active surface area to volume ratio.…”

Section: Internal Reforming Reactionsmentioning

confidence: 99%

Modeling Validation and Simulation of an Anode Supported SOFC Including Mass and Heat Transport, Fluid Flow and Chemical Reactions

Andersson

Yuan

Sundén

et al. 2011

ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology

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Fuel cells are electrochemical devices that directly transform chemical energy into electricity, which are promising for future energy systems, since they are energy efficient and, when hydrogen is used as fuel, there are no direct emissions of greenhouse gases. The cell performance depends strongly on the material characteristics, the operating conditions and the chemical reactions that occur inside the cell. The chemical-and electrochemical reaction rates depend on temperature, material structure, catalytic activity, degradation and the partial pressures for the different species components. There is a lack of information, within the open literature, concerning the fundamentals behind these reactions. Experimental as well as modeling studies are needed to reduce this gap.In this study experimental data collected from an intermediate temperature standard SOFC with H 2 /H 2 O in the fuel stream are used to validate a previously developed computational fluid dynamics model based on the finite element method. The developed model is based on the governing equations of heat and mass transport and fluid flow, which are solved together with kinetic expressions for internal reforming reactions of hydrocarbon fuels and electrochemistry. This model is further updated to describe the experimental environment concerning cell design. Discussion on available active area for electrochemical reactions and average ionic transport distance from the anodic-to the cathodic three-phase boundary (TPB) are presented. The fuel inlet mole fractions are changed for the validated model to simulate a H 2 /H 2 O mixture and 30 % pre-reformed natural gas. Keywords: SOFC, Modeling, Validation, Active Area, IonicTransport Distance, COMSOL Multiphysics INTRODUCTION AND PROBLEM STATEMENTFuel cells (FCs) are promising due to advantages of higher efficiency and lower emissions of SO X , NO X and CO 2 than conventional power generation [1]. The solid oxide fuel cell (SOFC) is a high temperature fuel cell, which operates at 600-1000 ºC [2]. This temperature allows SOFCs to operate with different types of fuels from both fossil and renewable sources. It opens a way for an easier transition from conventional power generation with hydrocarbon based fuels to fuel cells with possibility for different fuels, especially SOFCs. Due to the increasing global awareness of that energy usage affects the environments, the interest of renewable energy has increased. SOFCs are generally more tolerant to contaminants than other fuel cells and the possibility to internally (as well as externally) reform the fuel make them interesting for renewable energy resources [1].Numerical results of SOFC models are only approximations of real conditions and the validation is an important and necessary step in the development of reliable and accurate computational models. A range of validity can be established between the developed model and experimental

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Section: Internal Reforming Reactionsmentioning

confidence: 99%

Modeling Validation and Simulation of an Anode Supported SOFC Including Mass and Heat Transport, Fluid Flow and Chemical Reactions

Andersson

Yuan

Sundén

et al. 2011

ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology

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“…The fuel gas inlet conditions are specified as x H2 : x CH4 : x CO : x H2O : x CO2 = 0.2626 : 0.171 : 0.0294 : 0.4934 : 0.0436 (defined by IEA) (27), and the gas inlet temperature is specified as 1100 K. An average cell current density of 0.3 A/cm 2 , an oxygen surplus factor of 4, fuel consumption of 80 % (mole) and flow direction left -> right for both the anode and the fuel channel, are defined. Typical SOFC material characteristic data used in this work are found in (19)(20).…”

Section: Resultsmentioning

confidence: 99%

SOFC Modeling Considering Internal Reforming by a Global Kinetics Approach

2009

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Fuel cells (FCs) are promising for future energy systems, since they are energy efficient and fuel can be produced locally. When hydrogen is used as fuel, there are no emissions of greenhouse gases. In this study a two dimensional CFD (COMSOL Multiphysics) is employed to study the effect from porous material surface area ratio on reforming reaction rates and gas species distributions for an anode-supported solid oxide fuel cell (SOFC). FCs can be considered as multifunctional energy devises, combining (electro-) chemical reactions, heat exchange, gas- and ionic transport. All these functions are strongly integrated, making modeling an important tool to understand the couplings between mass-, heat-, momentum transport and chemical reactions. Steam reforming takes place at the nickel material surfaces in the anode and water-gas shift reaction occurs where fuel gas is present. Benefit from the internal reforming is that the energy conversion efficiency will be higher, compared to the case of pure hydrogen as fuel.

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“…x H2O : x CO2 = 0.2626 : 0.171 : 0.0294 : 0.4934 : 0.0436 [22]. The air inlet is defined as air, including oxygen and nitrogen.…”

Section: Mass Transportmentioning

confidence: 99%

SOFC modeling considering electrochemical reactions at the active three phase boundaries

Andersson

Yuan

Sundén

2012

International Journal of Heat and Mass Transfer

182

105

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It is expected that fuel cells will play a significant role in a future sustainable energy system, due to their high energy efficiency and the possibility to use renewable fuels. A fully coupled CFD model (COMSOL Multiphysics) is developed to describe an intermediate temperature SOFC single cell, including governing equations for heat, mass, momentum and charge transport as well as kinetics considering the internal reforming and the electrochemical reactions. The influences of the ion and electron transport resistance within the electrodes, as well as the impact of the operating temperature and the cooling effect by the surplus of air flow, are investigated. As revealed for the standard case in this study, 90 % of the electrochemical reactions occur within 2.4 m in the cathode and 6.2 m in the anode away from the electrode/electrolyte interface. In spite of the thin electrochemical active zone, the difference to earlier models with the reactions defined at the electrodeelectrolyte interfaces is significant. It is also found that 60 % of the polarizations occur in the anode, 10 % in the electrolyte and 30 % in the cathode. It is predicted that the cell current density increases if the ionic transfer tortuosity in the electrodes is decreased, the air flow rate is decreased or the cell operating temperature is increased.

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Charge, mass and heat transfer interactions in solid oxide fuel cells operated with different fuel gases—A sensitivity analysis

Cited by 42 publications

References 7 publications

Modeling Validation and Simulation of an Anode Supported SOFC Including Mass and Heat Transport, Fluid Flow and Chemical Reactions

Modeling Validation and Simulation of an Anode Supported SOFC Including Mass and Heat Transport, Fluid Flow and Chemical Reactions

SOFC Modeling Considering Internal Reforming by a Global Kinetics Approach

SOFC modeling considering electrochemical reactions at the active three phase boundaries

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