具新型類雙極板結構壓電式無閥質子交換膜燃料電池之研究

由過去的研究得知，將壓電材料應用於質子交換膜燃料電池，使燃料電池陰極端成為一空氣泵，稱為壓電式質子交換膜燃料電池。此外並加入漸縮及漸擴元件於空氣泵，稱壓電式無閥質子交換膜燃料電池，可增加空氣流量並解決水氾濫問題使壓電式質子交換膜燃料電池性能提升。本文研究壓電式無閥質子交換膜燃料電池在不同振動頻率、展弦比及操作溫度對壓電式無閥質子交換膜燃料電池性能之影響，並以此為基礎設計出具新型類雙極板結構之壓電式無閥質子交換膜燃料電池雙電池組，探討其性能。此雙電池組為電路並聯結構，反應面積為每個電池2x2 cm2，並聯後總反應面積為8 cm2。新型類雙極板結構為兩個電池陽極在外，陰極對陰極並共用一壓電泵以吸入並排出陰極腔體中之流體。實驗結果發現在漸縮及漸擴元件開口角度5度及展弦比11.25時有較好的性能，而由模擬結果得知較大的展弦比會造成流體阻塞現象使空氣流量減少，較小的展弦會造成腔體內外壓差較小而使空氣流量變小。研究並發現將開口角度增加為10度時發現較佳的展弦比為5.63，可使雙電池組尺寸更小。雙電池組的性能約為單電池的一點六倍，並非為單電池的兩倍，其原因來自壓電泵的振幅不對稱造成兩個電池的空氣流量不同，因此電流大小也不同。實驗結果並發現小型化後的雙電池應操作於氫氣當量比1.5、電池溫度50 °C及氫氣加濕溫度30 °C以避免濃度極化現象。壓電泵的消耗功率和操作頻率及溫度呈正相關，當考慮電池組淨輸出功時應將壓電泵消耗功率列入考量，在本研究中雙電池組的最高淨輸出性能為0.7W。此外，研究並發現當雙電池組中有一性能較差的電池組，在高電壓輸出時雙電池組會出現內電流，但在較低電壓輸出時仍然可輸出淨電功。

關鍵字

質子交換膜燃料電池；壓電材料；漸縮漸擴元件；類雙極板；自然進氣

並列摘要

An innovative design for a piezoelectric proton exchange membrane fuel cell with nozzle and diffuser (PZT-PEMFC-ND) using pseudo-bipolar design is developed to achieve a higher power in the stack design to solve water-flooding problems and improve cell performance. This new design, with a reaction area of 8 cm2, contains two cells with two outside anodes and two inside cathodes that share a common PZT vibrating device for pumping air flow. The influence of the varying aspect ratio (AR) of the diffuser elements on the unit cell-flow rate is investigated using a three-dimensional transitional model. The simulation results show that a proper AR value of 11.25 for the diffuser, with a smaller diffuser angle of 5°, could ensure a smoother intake of the air and, thus, better cell performance. The experimental results show that the performance of the PZT-PEMFC-ND bi-cell can be 1.6 times greater than that of the single cell. Furthermore, this novel design is shrunken by using a reduced nozzle and diffuser. This reduced bi-cell should be operated with a larger hydrogen stoichiometric ratio of 1.5, a cell temperature of 50 °C and a humidified hydrogen temperature 30 °C to prevent a serious concentration loss. Moreover, the performance of the bi-cell using one degraded membrane electrode assembly (MEA) and one normal MEA is investigated to understand the current flow characteristic of the bi-cell. Although an internal current is observed, the bi-cell can still deliver a non-negative power. The power consumption of the PZT device is temperature-dependant and this should be taken into consideration when determining the net power of the PZT-PEMFC-ND bi-cell. The maximum net power of the bi-cell is found to be 0.7W.

並列關鍵字

piezoelectric ； fuel cell ； nozzle ； diffuser ； air-breathing ； pseudo-bipolar

參考文獻

[3] G. J. Van Wylen, R. E. Sonntag, 1986, “Fundamentals of Classical Thermodynamics, 3rd ed.,” John Wiley & Sons, England.

[4] J. Larminie, A. Dicks, 2003, “Fuel Cell Systems Explained 2nd Edition” John Wiley & Sons Ltd., England.

[6] J. D. Morse, 2007, “Micro-fuel cell power sources,” Int. J. Energy Res., 31, 576–602.

[7] T. E. Springer, T.A. Zawodzinski, S. Gottesfeld, 1991, “Polymer Electrolyte Fuel Cell Model,” J. Electrochem. Soc., 138, 2334-2342.

[8] H.K. Ma, S.H. Huang, 2006, “Simulation of Water Vapor Transportation Phenomena in Proton Exchange Membrane Fuel Cells (PEMFCs),” The 4th International Conference on Fuel Cell Science, Eng. and Tech., Irvine, California, USA.

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具新型類雙極板結構壓電式無閥質子交換膜燃料電池之研究

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