The Performance Research Of Solid Oxide Fuel Cell Building Combined Heat And Power System

Fuel cell technology based on natural gas is a kind of promising and cleaning energy conversion technology under development for application. The generation mechanism of fuel cell is different from the traditional device,and the efficiency is not restricted to Carnot cycle, therefore, it is almost the highest efficiency generation device. Fuel cell as the motor of building cogeneration system is the integration of high efficiency energy conversion type with high efficiency energy utilization method.The research work has the significance of energy utilization ratio and environment quality improvements.In this paper, the thermodynamics comparison of fuel cell technology and the convetional generation technology has been done,and two kind of advantaged fuel cells in building application has been analyzed, and then, solid oxide fuel cell distributed energy systems application has been determined as the research object. The main research work are as followed:Firstly,the direct internal reform solid oxide fuel cell(DIR-SOFC) model has been established and validated based on mass and energy balances coupled with appropriate expressions for the reaction kinetics, thermodynamic constants and material properties,and it is a flexible simulation tool, which could easily be adapted to different cell geometries and operation conditions,and then,the fuel cells performance characters have been simulated and analyzed,and the operation region has been determined.Secondly,the stack and other components models have been integrated succesfully.The system design has been finished such as stack areas and components capacities determination, and the run condition has been simulated. The design method which is applicable in SOFC systems process design has been formed.Thirdly,the operation parameters has been investigated.The performance effects were analyzed under different prereform temperature, prereform ratio,the steam to carbon ratio (STCR), and control parameters variety. Four kinds of feasible modulation methods have been put forwarded,and the comprehensive efficiency, operation region characters,and modulation range of heat and electric have been compared under four methods, and the modulation methods of operation temprature and fuel utilization as control parameters and operation temprature and operation voltage as control parameters have been approved to appropriate for building cogeneration system.Fourthly,the process design route of SOFC combined heat and power system has been proposed according to different energy consumption characters. A predigested economic model has been established in which the relation of scale and cost was disposed by index scaling method,and then the system was optimized from the aspects of flow Configuration and parameters.In the first aspects,five flowsheet Configurations were simulated and heat efficiency, electric efficiency, capital cost and life cycle cost was analyzed.In the second aspects,the factorial experiment and multiway analysis of variance were used to distinguish the significant and subordinate variable,and to analyze the variable effects on systems'technic and economic performance,and then the regression model, conour plot, and response surface method were used to indicate the relationship between dependent and independent variable.The optimist operation point was found by constraind optimization model which let the life cycle cost as the optimization object,furthermore,the constrained conditions were relaxed and the constrained condition effects trends on optimist point has been analyzed under two current density levels.The design strategy and operation strategy of SOFC building cogeneration system were investigated. The design strategy was proposed under high heat to electric ratio and high electric demand as followed,heat transformation,surplus power utilization,heat utilization deeply,fuel cell modulation, grid suppletion, power transformation, difference point design, and then, indicated that the electric load followed and grid suppletion added is applicable.The integrated dispatch problem was optimized on equipment capacity, quantity, and run strategy, the production cost was as optimization object and the Sequential Quadratic Programming was as the method and the high frequency load condition concept was proposed to determine equipment quantity.At last,an office case was simulated all year, and the comprehensive efficiency, cost save,CO2 emmisions reduction was computed, the detailed results could be the guidline for system design and optimization. Lastly,The paper indicated the conventional technical evaluation index's insufficiency, and proposed the concept of dynamic evaluation method which could describe the fuel cell partload advantage.The conventional index was ameliorated to dynamic first law efficiency and dynamic second law efficiency , and annual primary energy gene and annual second energy gene were defined, and then, the applicability was analyzed in different region and different building type,it is indicated that when the load is durative and heat to electric ratio equal to 1.6 and the cold to electric ratio equal to 1, the SOFC building cogeneration system would be more applicable.The system could be the turning point for improvement of energy utilization and reduction of contamination along with the fuel cell technology's maturity, and have the potential to be used in enduser abroadly.The research conclusions could be the reference for SOFC–BCHP system's application.