Desenvolvimento da Simulação Computacional de uma Célula a Combustível de Óxido Sólido com Geometria Cilíndrica Planar

Abstract

Solid oxide fuel cells (SOFCs) are devices that convert chemical energy from a fuel directly into electrical energy and they demonstrated to be a good alternative due to their high efficiency and for producing clean energy. However, there are difficulties, such as the high operating temperature (around 1000°C), which limit the choice of materials and reduce the useful life of the device due to thermal degradation and corrosion of the materials. This makes it difficult and expensive to build systems using SOFCs. In the face of these challenges, the interest in solving problems through computer simulation has become great, which allows the acceleration of the system's operation, makes it possible to predict possible accidents that would occur during the implementation of a real system, in addition to saving economic resources, as it does not require building prototypes for testing. The modeling of the SOFC cell can be studied as a function of the transport phenomena in fluids made by the finite element method. The general current-voltage curve of an electrochemical cell, known as the polarization curve, depends on the means by which the current or voltage is changed. Therefore, the aim of this work was to develop a simulation of the operation of a SOFC to obtain the performance data of the same, from experimental data. To obtain the experimental data, a SOFC was made with 8% mol YSZ electrolyte and Ni-YSZ (1:1) and LSM (x = 0.2) electrodes, being the anode and cathode, respectively. The chosen composition has consolidated data in the literature, since the objective is to propose the computational model with reliable data. The composition was characterized by tests of apparent density (AD), apparent porosity (AP), scanning electron microscopy (SEM) and impedance spectroscopy (IS), in order to provide values and experimental parameters for the construction and validation of the computational model. Then, two computer simulations were developed, using the COMSOL Multiphysics® programa, based on the same interface (secondary current distribution). The first simulation was electrochemical impedance (IS) spectroscopy of the YSZ electrolyte, which allowed the validation of the selected equations and comparison with the EI analysis performed experimentally. Then, the SOFC operation simulation was developed, which allowed to obtain the polarization curve, the distribution of the molar fraction of the gases in the electrodes and the power density curve. For this second simulation, experimental data and literature data were also used to compare and validate the simulation. From the results obtained, it is possible to state that the two computer simulations developed converged to reasonable solutions and can be used to predict the operation of SOFCs with planar cylindrical geometry in a wide range of operating conditions.