無感測器之直接甲醇燃料電池燃料濃度偵測與控制演算法

Sensor-less of Fuel Concentration Detection and Control for Direct Methanol Fuel Cells

沈坤昇(Kun-Sheng Shen)

指導教授 ： 萬其超 ； 王詠雲

國立清華大學/工學院/化學工程學系/博士(2010年)

摘要

本篇論文主要是在直接甲醇燃料電池系統上提供一個無濃度感測器的燃料控制演算法，此演算法的數學模型是建立在先前邱昱仁教授等人所提出的等濃度曲線差補的基礎概念所延伸出來。本研究利用一組含有32顆單電池的電池堆並於數組燃料濃度、溫度與電壓進行電池組性能測試。每一個甲醇水溶液燃料濃度下的數組「溫度、電壓和電流」數據可構成一個“電流、電壓、溫度”曲面。針對每一個特定的膜電極組，我們可經由實驗測試建立數組等甲醇濃度燃料之＂電流、電壓、溫度＂曲面，並將曲面以多項數函數貯存於系統電腦。即時系統上燃料混合槽的甲醇濃度可由系統輸出的＂電流、電壓、溫度＂數據及已儲存的等甲醇濃度之＂電流、電壓、溫度＂曲面函數以插補運算方法估算出，上述運算方法是建立在＂膜電極組＂處於穩定狀態不會因電池長時間操作而衰減。真實的系統＂膜電電極組＂會因長時間的操作而性能衰減造成燃料甲醇濃度估算產生誤差。故本論文針對膜電極電壓衰減提出“暫態衰減＂與 “遠久衰減”的修正，利用電池組的長時間操作壽命測試得到二組電壓衰減修正係數e1與e2並利用此校正係數來修正系統所量測到的電壓值。本論文另外藉由等甲醇濃度曲面的模型在直接甲醇燃料電池系統中量測甲醇與水在混合槽的消耗率。在數組不同的等甲醇甲醇濃度、溫度和電流之間的遞增與遞減的關係構成另兩個等濃度曲面插補的演算法，分別來估算燃料混合槽中水與甲醇的消耗速率。並結合“電流、電壓、溫度”之間所構成的等甲醇濃度曲線差補演算法提供“甲醇消耗率、電流、溫度”與“水消耗率、電流、溫度”等濃度曲線差補演算法所需的未知甲醇濃度，來估算混合槽中甲醇與水的整體消耗量。根據估算的甲醇與水的消耗量，系統液體幫浦可適時補充甲醇與水至燃料混合槽，系統混合槽的燃料量與甲醇濃度維持在一個最佳狀態。本論文我們報告：(1) 估算直接甲醇燃料電池發展甲醇濃度估算的演算法；(2)估算直接甲醇燃料電池系統的甲醇與水消耗的演算法；並由實驗數據證實無濃度感測器的燃料控制演算法可以在”穩態的功率負載”和”動態的功率負載”下可成功維持混合槽中燃料最佳的濃度與水位。

關鍵字

直接甲醇燃料電池 ； 無感測器演算法 ； 濃度偵測 ； 燃料控制 ； 燃料消耗

並列摘要

We report an algorithm for real time controlling quantity and methanol concentration of the fuel of a DMFC. The MEA voltage decay coefficients [e1, e2], and I-V-T, M'-I-T , and W'-I-T curves (where I is the current, V the voltage, T the temperature, and M' and W' the methanol and water consumption rates, respectively) of n fuels with specified methanol concentrations CM,k (k= 1, 2,…, n) are preestablished and form (I,V,T), (M',I,T) , and (W',I,T) surfaces for each CM,k. The in situ measured (I,V,T)u after voltage decay correction is applied to the n preset (I,V,T) surfaces to estimate CM,u (the CM corresponding to (I,V,T)u ) using an interpolation procedure. The CM,u is then applied to the n preset (M',I,T) and (W',I,T) surfaces to estimate cumulated “methanol” and “water” consumed quantities. Thus in a real time system, the CM and total quantity of fuel can be controlled using the estimated CM,u and cumulated “methanol” and “water” consumed quantities. In this thesis, (1) by modifying Chiu and Lien constant concentration surfaces approach, we developed a sensor-less algorithm for estimating methanol concentration of fuel; (2) developed an approach for evaluating the consumption rate of water and methanol, thereby determining the in-situ consumed quantity of liquid fuel in an operating DMFC system. We also carried out experiments to validate the proposed approach on a stack of 32-cells for both the steady-state and dynamic operating conditions. Thus the algorithm is suitable for fuel control management of portable DMFC systems.

並列關鍵字

Direct methanol fuel celll ； sensor-less algorithm ； concentration detection ； fuel control ； fuel consumption ； DMFC

參考文獻

2.S Arico, S. Srinivasan, and V. Antonucci, “DMFCs: From fundamental aspects to technology development”, Fuel Cells 1 ( 2001) 133-161.

3.L. Carrette, K. A. Friedrich, and U. Stimming, “Fuel cells: Fundamentals andapplications”, Fuel Cells 2001, 1,5.

4.J.C. Amphlett, B.A. Peppley, E. Halliop, and A. Sadiq. “The effect of anode flow characteristics and temperature on the performance of a direct methanol fuel cell”, J. Power Sources 96 (2001) 204-213.

5.H. Dohle, H. Schmitz, T. Bewer, J. Mergel, and D. Stolten, “Development of a compact 500W class direct methanol fuel cell stack” J. Power Sources 106 (2002) 313-322.

6.X. Ren, P. Zelenay, S. Thomas, J. Davey, and S. Gottesfeld, “Recent advances in direct methanol fuel cells at Los Alamos National Laboratory” J. Power Sources, 86 (2000) 111-116.