Integrated Modeling Approach For Solid Oxide Fuel Cell-based Power Generating System
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Solid oxide fuel cell (SOFC) systems have been recognized as the most advanced power generation system with the highest thermal efficiency with a compatibility with a wide variety of hydrocarbon fuels, synthetic gas from coal, hydrogen, etc. As a result of research focused on numerical studies for a tubular type- or a planar type-SOFC, fuel flexibility, design aspects of SOFC, materials, start-up process, and so on, SOFC technologies are remarkably being developed.Currently, most research activities are limited to a component level characterization of single fuel cell stack or material research for catalyst, electrolyte, sealing process, etc. In other words, approaches for developing an integrated SOFC system with combined heat and power (CHP)/power generation system for transient analysis have been limited. During normal operating modes of a SOFC system, optimal control of fuel and air supply and anode gas recirculation relies on accurate dynamic analysis of the entire SOFC system. With this research, integrated modeling approaches of SOFC stack with heat exchanger (HEX), compact heat exchange reformer (CHER), steam supply system, compressor or blower, ducts, etc. were introduced and developed for a power generation system. And, simulational results were validated with experimental results.The specific dynamic design tools for an integrated SOFC-based power generation system are as follows: 1) computational model for thermal dynamics of planar SOFC stack during stack heating process w/o production of electricity, 2) validation of simulational result of transient characteristics of the HEX with experimental result during the initial phase of start-up of small SOFC systems, 3) validation of simulational result of transient characteristics of the CHER with experimental result during the initial phase of start-up of small SOFC systems, and 4) development of model for dynamic communication between the developed stages out of fully integrated micro (~10kW) SOFC-based power generation systems.As a result of the researches, the computational software was developed to investigate the start-up process of SOFC without producing electricity. And, novel transient codes were developed that explain the dynamics of HEX and CHER. Test rigs for the experiment of HEX and CHER were developed. Performances of the HEX and CHER were well demonstrated experimentally and were validated with simulational results. Each developed sub-module was integrated to build up the integrated SOFC system step by step. In the final session, the integrated module was completed by including an electricity production module. The developed integrated SOFC system module provides guidance for establishing the fundamental design characteristics and a direction for choosing suitable HEX, reformer, compressor, etc.