Download Current-voltage behaviour of SOFCs considering - eLib

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts
no text concepts found
Transcript 
10th Symposium on Fuel Cell and Battery Modelling and Experimental Validation – ModVal 10
Abstract for oral presentation
Current-voltage behaviour of SOFCs
considering anode degradation
Vitaliy Yurkiv*,1, Jonathan Neidhardt1, Wolfgang G. Bessler2
1
German Aerospace Center (DLR), 70569 Stuttgart, Germany; University of Stuttgart, 70550
Stuttgart, Germany
2
Offenburg University of Applied Sciences, 77652 Offenburg, Germany
*Presenting author, email: [email protected], Tel.: +49 711 6862 8044
Solid oxide fuel cells (SOFC) are promising alternative energy sources for a wide application
range from mobile technology to stationary power plants due to their high energy efficiency
and low pollutant emission. One of the biggest advantages of an SOFC is its ability of direct
utilization of various fuel types, i.e. H2/H2O, CO/CO2 and hydrocarbons. It is, however, well
known that operation of an SOFC based upon various fuels could cause various types of cell
degradation. Therefore, understanding the origin and evolution of degradation processes on
micro(nano)-scale is essential to develop long-term operating SOFC technology.
We present a modeling and simulation study of secondary-phase formation in porous
Ni/YSZ, which leads to anode degradations. Specifically, we investigate the formation of solid
nickel oxide formation (re-oxidation) in the case of high fuel utilization or low cell voltages, as
well as the formation of solid carbon (coking) in the case of internal reforming. The model is
based on a multi-phase framework [1], that allows the introduction of arbitrary solid and gas
phases, where reactions between the bulk phases occur via interface-adsorbed species and
they are described by an elementary kinetic approach. Published experimental data are used
for parameterization and validation.
Regarding nickel oxide formation, thermodynamic calculations are used to predict the local
conditions for the formation of nickel oxide. Simulation results reveal a big gap between local
condition inside the cell and global operating parameters. For example, cell operation far
below the limiting voltage of 0.704 V (at 1073 K) is possible without re-oxidation as long as
the fuel utilization is low.
In the case of solid carbon formation, the simulation results show that the cell performance
degradation are influenced significantly by the operation temperature and applied potential.
Specifically at OCV, high temperature (~1000 K), mainly, provokes the formation of surface
and/or subsurface carbon and at low temperature (~700 K) carbon mostly blocks pores,
which significantly influences fuels diffusion. However, under applied potential the amount
and type of carbon change drastically due to higher hydrogen content in carbon phase.
References
[1]
J.P. Neidhardt, D.N. Fronczek, T. Jahnke, D. Danner, B. Horstmann, W.G. Bessler, A
flexible framework for modeling multiple solid, liquid and gaseous phases in batteries
and fuel cells, J. Electrochem. Soc. 159 (2012) A1528–A1542.
Related documents