全釩液流電池之電極改質與充電狀態感測及系統模擬研究

全釩液流電池(vanadium redox flow battery, VRFB)為一種具發展潛力之電能存儲裝置，特別適用於搭配間歇式再生能源，強化綠能應用性。本論文之研究內容分成三部分，施以創新改質技術，納菲離子聚合物溶液(Nafion® ionomer solution)含浸改質石墨氈(graphite felt, GF)，有效改善石墨氈電極的親水性，Nafion®離子聚合物與GF重量比為0.9之NGF N90電極，置於VRFB電解液可達完全潤濕，並具良好電化學反應性能，能量效率高達73.08 ％，放電容量為2.015 Ah。經30次充放電循環後，衰退率僅約3 ％。針對監測VRFB充電狀態(state of charge, SOC)，提出新穎的超音波速度傳感測定模式，使用2 M硫酸配置釩離子電解液，於不同電解質濃度，測量感測超音波速度值與操作溫度和濃度之關係。於10~90 ％ SOC範圍，超音波速度之實驗量測值與經驗方程式預估值十分吻合，誤差僅±2 ％。開發數學模型描述VRFB三維多孔電極之電池反應與釩離子交叉混和效應，對比電池充電曲線之模擬數值與實驗數據，充電階段於10~80 ％ SOC，實驗電壓值相對於模擬值僅0.324 ％誤差，驗證模擬結果之優異擬真性。模擬結果推定於80 ％ SOC，V(III)與V(IV)離子濃度量值上升為無擴散混和效應之1.08與1.29倍。

關鍵字

全釩液流電池；石墨氈電極；電極改質；超音波速度；充電狀態；交互混合；電位分布

並列摘要

Vanadium redox flow battery (VRFB) is a promising electrical energy storage device, particularly for use with intermittent-type renewable energies. The content of this thesis is divided into three parts. A new modification approach by impregnation with a Nafion® ionomer solution significantly improves the wettability and substantially enhances the activity of the graphite felt (GF) electrode. The NGF N90 electrode with a weight ratio of Nafion® ionomer/GF = 0.9 is fully wetted in the electrolyte solution and exhibits good performance. The energy efficiency is as high as 73.08% and the discharge capacity is about 2.015 Ah. It decays only about 3% after 30 charge-discharge cycles in operation. A novel ultrasonic velocity sensing approach is proposed and investigated to monitor the state of charge (SOC) of VRFB. The vanadium ion solutions are prepared in 2 M H2SO4 aqueous solution. Their ultrasound velocities measured in the electrolyte solutions are found to be both temperature- and concentration-dependent. A master model equation fits the experimental results of both charging and discharging stages quite well within the SOC range of 10~90 % with ±2 % errors with respect to the predicted values. A 3D isothermal model for VRFB is developed. The redox reactions in a porous electrode are formulated. The simulated battery charging curve is compared with the experimental results within the SOC range of 10~80% with 0.324 % errors with respect to the predicted values. The numerical result is validated against the experiment data. The simulation results indicate that the vanadium ion cross-mixing effect is significant at higher SOC. With vanadium crossover effects, the concentration of V(III) and V(IV) ions are increased to 1.08 and 1.29 times at 80 % SOC.

並列關鍵字

Vanadium redox flow battery ； Graphite felt electrode ； Electrode modification ； Ultrasonic velocity sensing ； State of charge ； Crossover ； Potential distribution

參考文獻

EPRI, 2010, Electric Energy Storage Technology Options: A White Paper Primer on Applications, Costs, and Benefits.

Google Scholar

Carnegie, R., Gotham, D., Nderitu, D., Preckel, P. V., 2013, Utility Scale Energy Storage Systems, Benefits, Applications, and Technologies, State Utility Forecasting Group.