| The solid oxide fuel cell (SOFC) is recognized to be one of the most advanced and efficient power generation plants with low environmental emissions. It plays an important role in relieving the global energy supply insecurity and reducing the emissions of greenhouse. It has been considered to be a potential candidate to replace the traditional thermal cycle power generation. Model development and simulation is one of the most important methods in the research of solid oxide fuel cells.The fundamentals of SOFC including the cell components, the stack flow configuration and fuel processing are first introduced in the work. The performance of SOFC power generation is studied with experimental tool. A typical curve is acquired for the polarization losses of SOFC with current density ranging from zero to upper limit. The effect of active polarization, concentration polarization and ohmic loss on the SOFC performance is specially studied under various loads and temperature in the experiment.A three-dimensional numerical model with a complete polarization electrochemical mathematic model for the solid oxide fuel cell is developed in this study. Numerical simulations are performed with the Navier-Stokes equations and potential equation solved with the electrochemical model for both of the International Energy Agency (IEA) planar SOFC and Siemens-Westinghouse tubular SOFC. The validation of the numerical model is implemented through the IEA benchmark results and experimental data in the literatures. Both the electric performance and thermal characteristic are studied by numerical tool on the planar and tubular solid oxide fuel cells, respectively. The distributions of the states including the temperature, current density, voltage and species concentration are obtained and analyzed based on the simulation results. Numerical simulation shows that the voltage loss mostly come from the electrolyte ohmic loss and the active polarization in the planar SOFC. For the tubular SOFC, the cathode ohmic loss is the maximum in the total voltage loss, while the active polarization is the second high loss. The ohmic heat mainly depends on the current density in the planar SOFC. In the tubular SOFC, mostly of the ohmic heat are produced in the cathode. The percentage of the ohmic heat in total generated heat for tubular SOFC is higher than that of planar SOFC.A lumped, nonlinear control-oriented dynamic model for the solid oxide fuel cell is developed in this study. In the dynamic model, the spatial effect is accounted with a Exponential Decay Function and a Exponential Associate Function fitting the states distribution in the fuel cell along the gases flow direction. The spatial effect is lumped into the dynamic model by three parameters of the fitting function, which are determined via numerical simulation. A planar solid oxide fuel cell with co-flow is used to evaluate the accuracy and applicability of the developed dynamic model. The dynamic model is programmed and implemented using the SIMULINK software. The simulation results indicate the model has good service quality to predict the state variables and the performance of the solid oxide fuel cell.A dynamic model of SOFC/GT hybrid system is put forward based on the conservation equations of mass, energy and force through the whole plant, with specific source terms in different types of components. Dynamic simulation for a proposed air reheatting hybrid system is implemented to validate the model, which is programmed via the simulation tool Aspen Custom Modeler. The obtained results show that the presented dynamic model can be able to simulate the system dynamic track reasonably. Cycle analysis is conducted on two hybrid schemes so-called recuperative heat exchanger (RHE) and exhaust gas recirculated (EGR) with the developed model. The system performance with operating pressure, turbine inlet temperature, and fuel cell load are studied based on the simulation results. The effects of oxygen utilization, fuel utilization, operating temperature and efficiencies of gas turbine components on the system performance of the RHE cycle and the EGR cycle are discussed in detail. Simulation results indicate that the system optimum efficiency of EGR air reheating cycle scheme is higher than that of the RHE cycle system. A higher pressure ratio would be available for the EGR cycle system in comparison with the RHE cycle. It is found that increasing fuel utilization or oxygen utilization would decrease fuel cell efficiency but improve the system efficiency for both of RHE and EGR cycles. The efficiency of RHE cycle hybrid system decreases as the fuel cell air inlet temperature increases. However, the system efficiency of EGR cycle increases with fuel cell air inlet temperature. The effect of turbine efficiency on the system efficiency is more obvious than the effect of compressor and recuperator efficiencies among the gas turbine components. It is also indicated that improving the gas turbine components efficiencies for RHE cycle increases system efficiency relatively higher than that for the EGR cycle.The nonlinear model predictive control (NMPC) is based on the optimization of the measurements and states estimation to determine the open-loop control profiles. It is well suited in the nonlinear control environment with specified constraints. This study presents the application of the nonlinear model predictive control on a planar SOFC. The states are estimated based on the output of the plant using the moving horizon state estimation (MHE) method. The NMPC control system of a planar SOFC is developed and simulated under the platform MATLAB. The current density, the fuel flow and the air flow are chosen to control the output power, the fuel utilization and the operating temperature. A set of stochastic noise are artificially added to the output model of the SOFC to validate the robustness of MHE. Simulation results showed that the MHE has functioned perfectly in noise removal to estimate the states in the NMPC control system. The designed NMPC controller also work properly which follows the controlled variables trajectory by adjusting the manipulated input variables and the target states. The controller demonstrates its advantage to deal with the operation of SOFC with constraints. The closest solution to the target is given by the NMPC controller when the violation occurs between the objective trajectory and the constraint condition.This work provides the model tool for the design and optimization of SOFC stack and hybrid cycle. It also is a basic work to develop the control and diagnosis system for SOFC.
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