固態氧化物燃料電池熱電系統之動態模型建構

Abstract

本論文建立一10KW固態氧化物燃料電池熱電合併系統( SOFC-CHP )模型，其中包含燃料電池堆、燃料重組器、後燃燒室與兩組熱交換器等子裝置。我們根據” 控制體積( Control Volume ) ”的概念並且使用莫爾質量守恆與能量守恆原理來推導系統中每一子裝置系統模型與熱力學性質。 首先我們基於電化學反應過程、莫爾質量守恆與能量守恆來建立一固態氧化物燃料電池，並且利用數學模擬軟體MATLAB/SIMULINK實現。接著我們依序討論燃料重組器、後燃燒室與熱交換器數學模型推導過程與輸出動態響應行為。最後我們以一10KW級電能輸出熱電合併系統當成是我們的系統設計規格，由模擬結果可得知，當燃料電池操作在900K時，每一單片電池會有0.3W/CM^2功率密度輸出，而其能量轉換效率為41%，當考慮熱電系統的整體效率時，系統整體效率可達79%。 本論文建立了固態氧化物燃料電池熱電合併系統的動態模型。此模型可應用於未來燃料電池熱電系統的設計與控制，包括：效率最佳化、系統反應強健性控制等，進而加速系統開發時程。

The aim of this study is the build a mathematic model for a solid oxide fuel cell combined heat and power ( SOFC-CHP ) system. This system consists of SOFC stacks, a Reformer, an after-burner, and two heat exchangers. The model of each subsystem was developed on the basis of “ control volume ” using molar and energy conservation. The mathematic models were developed for the planar type SOFC, counter-flow type heat exchangers, and a Reformer for natural gas (CH_4). The Matlab/Simulink software was used to construct the dynamics for each subsystem. And then, the dynamics models of these subsystems were linked together to complete the overall system simulations. The whole system consists of 20 states and nonlinear ordinary differential equations. Finally, we used a 10KW SOFC-CHP system as a design example. The simulation results indicate that the system operating temperature is about 900k, the SOFC stacks have 10kw power output, the energy conversion efficiency of SOFC is about 40%, and the energy efficiency of the overall SOFC-CHP system is 79%.