Modelling a H2S fuelled solid oxide fuel cell

Fuel cells are promising sources of electrical energy because of their exceptionally high efficiencies and low environmental emissions. Solid oxide fuel cells (SOFC) are high temperature, ceramic electrolyte cells, which unlike most other fuel cells, can work with a variety of fuels besides pure hydrogen, including hydrocarbons and hydrogen sulfide. In this presentation I present the models we have built for a single H2S fuelled SOFC. The goal is to model the electrochemical reaction coupled with mass transfer, fluid flow and current/voltage distribution in an yttria stabilized zirconia electrolyte fuel cell assembly operated between 750 and 850 °C. Two models of the above SOFC are discussed in this work, 1) an algebraic model derived by integrating a one-dimensional model along the thickness of the cell, and 2) a two-dimensional finite element axi-symmetric model. Important physical and kinetic parameters in the 1-D model are fitted using experimental data sets at three different temperatures and reasonable fits are obtained for the data sets at 800 °C and 850 °C. However, the third data set at 750 °C does not give a good fit using this model. We need to apply the curve-fitting to more data sets to investigate it further. The main conclusion that can be drawn from the present study is that the ohmic resistance of the cell is very high. Contact resistances are believed to be the reason behind this although there could be contributions from resistive interphases. The 2-D model also gives reasonable fits to data sets. One of the publications by the laboratory group doing the experimental work in our department presented very interesting data that shows the cell performance being a strong function of fuel flow-rate. We want to model this behaviour and will have to depend on the 2-D model as the 1-D model does not have flow-rates as parameters.