Based on mathematical modelling and numerical simulations, a control strategy for a Molten Carbonate Fuel Cell Hybrid System (MCFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. The independent parameters are as follows: stack current, fuel mass flow and compressor outlet pressure. Those parameters can be controlled by external load, fuel valve and turbine-compressor shaft speed, respectively. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation, etc. The aim is to achieve maximum efficiency of power generated within these constraints. Governing equations of MCFC-HS modelling are given. An operational line of the MCFC-GT system is presented which fulfils several constraints (temperature difference, cell temperature, etc.) The system is able to achieve efficiency of more than 62% even in part-load operation.
In this work, a mid infrared thermography was used to study thermal behavior of solid oxide fuel cell (SOFC) with a circular shape and a diameter of 90 mm. The emissivity of the anodic surface of the fuel cell was determined to be from 0.95 to 0.46 in the temperature range 550-1200 K and the profile and temperature distribution of the anodic surface of the unloaded cell was given. The surface temperature of the cell was determined during operation and the polarity changes from open circuit voltage (OCV) to 0.0 V. It was found that the cell self-heating effect decreases with increasing temperature of the cell.
The aim of this work was to achieve a deeper understanding of the heat transfer in a microtubular Solid Oxide Fuel Cell (mSOFC) stack based on the results obtained by means of a Computational Fluid Dynamics tool. Stack performance predictions were based on simulations for a 16 anodesupported mSOFCs sub-stack, which was a component of the overall stack containing 64 fuel cells. The emphasis of the paper was put on steady-state modelling, which enabled identification of heat transfer between the fuel cells and air flow cooling the stack and estimation of the influence of stack heat losses. Analysis of processes for different heat losses and the impact of the mSOFC reaction heat flux profile on the temperature distribution in the mSOFC stack were carried out. Both radiative and convective heat transfer were taken into account in the analysis. Two different levels of the inlet air velocity and three different values of the heat losses were considered. Good agreement of the CFD model results with experimental data allowed to predict the operation trends, which will be a reliable tool for optimisation of the working setup and ensure sufficient cooling of the mSOFC stack.
The paper addresses the issues of quantification and understanding of Solid Oxide Fuel Cells (SOFC) based on numerical modelling carried out under four European, EU, research projects from the 7FP within the Fuel Cell and Hydrogen Joint Undertaking, FCH JU, activities. It is a short review of the main projects’ achievements. The goal was to develop numerical analyses at a single cell and stack level. This information was integrated into a system model that was capable of predicting fuel cell phenomena and their effect on the system behaviour. Numerical results were analysed and favourably compared to experimental results obtained from the project partners. At the single SOFC level, a static model of the SOFC cell was developed to calculate output voltage and current density as functions of fuel utilisation, operational pressure and temperature. At the stack level, by improving fuel cell configuration inside the stack and optimising the operation conditions, thermal stresses were decreased and the lifetime of fuel cell systems increased. At the system level, different layouts have been evaluated at the steady-state and by dynamic simulations. Results showed that increasing the operation temperature and pressure improves the overall performance, while changes of the inlet gas compositions improve fuel cell performance.
In this work, we developed the lanthanum strontium cobalt ferrite and it’s composite with yttrium iron cobaltite (mass ratio of 1:1) cathodes as a thin layer on Ce0.8Sm0.2O1.9 electrolyte. Two kinds of electrode pastes were prepared, with and without 6 mm polystyrene beads as an additional pore former. The performance of cathode materials was investigated by electrochemical impedance spectroscopy as a function of electrode morphology, oxygen partial pressure, potential, and temperature. The polarization resistance of the more porous electrodes was lower than those electrodes prepared without additional pore former in the whole potential range at 800°C, slightly lower at 700°C and 600°C. The addition of yttrium iron cobaltite decreased the performance of both types of cathodes. The lower polarization resistance of porous cathodes is due to the facilitated gas diffusion through their structure.