| As the energy crisis and the environment problem become more serious, people started to pay higher attention to energy utilization patterns of high efficiency and low pollution. To use the energy more efficiently and have a better protection for the environment, all the nations in the world are focusing on seeking new energy resources or clean energy. However, the continuous improvement of the performance of the energy conversion device keeps being the main development tendency of energy technology. Fuel cell is a kind of efficient and clean energy conversion devise, which converts the chemical energy of input fuel into the electrical energy, and supplies it for the out consistently. This power technology not also eases the pollution problem of using the fossil fuel, also makes the power utility manners more flexible and reliable. The paper builds a classic SOFC model, and then it analyzes and verifies the effect of some operating parameters on the performance of the SOFC system, performs a multi-objective optimization for the size and efficiency of the SOFC system with the Genetic algorithm adopted. Finally the waste heat with high temperature dumpped by the SOFC system is used to drive a general heat engine cycle to constitute a hybrid system composited with the SOFC fuel cell and the heat engine, improving the thermodynamic efficiency of the system. The detail research content is elaborated as follows:In Charper1, the brief introduction of the research background and development of the fuel cells are given.In Charper2, the introduction the working principle of the SOFC fuel cell system is given. Considering the irreversibility in the process of the thermodynamics and electrochemistry, The irreversible model of electrochemic and thermodynamics is built. Then, a SOFC system for given operating condition is set, and theoretical anaysis and numerical simulation are performed to explore the effect of operating parameters, like operating pressure, operating temperature, air stoichiometric, fuel stoichiometric ratio etc, on the performance stoichiometrics of SOFC system, which offers a theoretical basis for the next optimization work.In Charper3, the mathematic model of SOFC system size is deduced for a given output power. Combined with the efficiency model deduced in Charper2, genetic algorithm in mathematical software MATLAB is used to perform the multi-objective optimization for the system efficiency and size. There are four decision variables:the operating pressure, the fuel stoichiometric ratio, the air stoichiometric ratio and the current density. A Pareto set giving a quantative description of the trade-off between the two objectives is used to analyze the results. Optimization results prove the existence of optimal designs region for a50kW system with efficiency from43%corresponding to a14.6m2electrolyte area to48%corresponding to a25.4m2electrolyte area. The SOFC model used is general and the optimization results could be applied to the practical SOFC design.In Charper4, the high temperture waste heat of SOFC system is used to drived a heat engine of Carnot cycle to improve the performance of the hybrid system. A mathematic model of SOFC-heat engine hybrid system is built, taking account of Thermodynamic and Electrochemical irreversibility, the thermal-conduction resistance between the SOFC system and heat engine, where the SOFC model and some operating parameters are taken from the Charper2. The total performance of the hydrid system is simulated and computed through numerical modeling, and the effect of different operating conditions on the system is debated, optimal fields of operating parameters are obtained.In Charper4, the main content and conclutions of the paper are summarized. The innovation point and shortcoming are presented. The research trend of this paper is looked far ahead at last. |
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