報告書番号

W98027

タイトル（和文）

各種燃料電池の性能比較と新型燃料電池の可能性

タイトル（英文）

Performance analysis of several fuel cells and prospect of a new type fuel cell

概要 （図表や脚注は「報告書全文」に掲載しております）

PEFC,PAFC,MCFC,SOFCの４つの主要な燃料電池性能を、当所が開発したＭＣＦＣの性能評価手法を用いて同一視点から要因分析するため、電気化学理論に基づき各燃料電池の性能表示式を改良、あるいは導出した。加圧特性を、同一条件で初めて予測した結果、高温型(MCFC,SOFC)は低温型(PEFC,PAFC)に比較し電池効率が５％程度高いことがわかった。高温型ではカソード反応抵抗が小さいため電圧が高いが、開路電圧が熱力学的に高温なほど低下することと、オキサイドイオン移動型でネルンストロスが大きいことにより、性能向上が抑制されていることがわかった。さらに、各燃料電池の反応抵抗を用いて一般的な出力電圧の温度依存性を予測した結果、出力電圧は約500℃でなだらかなピークを示し、ネルンストロスが小さいプロトン移動型で中温域（300～500℃）で動作する燃料電池は高温型と同程度以上の性能が期待できることがわかった。

概要 （英文）

There are four types of fuel cells such as Polymer Electrolyte Fuel cells (PEFC), Phosphoric acid fuel cells (PAFC), Molten Carbonate Fuel Cells (MCFC), and Solid oxide Fuel Cells (SOFC). Efficiencies of power generation plants using these fuel cells are already reported by many organizations. However, performance comparison among these fuel cells has not performed. Therefore, equations which are able to express performances of the fuel cells with high accuracy are newly derived or modified with latest performance. Using these equations, cell voltages of the fuel cells were estimated. High temperature fuel cells such as MCFC and SOFC has high energy conversion efficiencies 5% higher than these of low temperature fuel cells such as PEFC and PAFC. This difference is originated from low cathode polarization. However, open circuit voltage decreases with temperature. In addition, Nernst loss of high temperature fuel cell is 80 mV higher than that of low temperature fuel cells since oxide ions move in the electrolyte with electrochemical reaction and generate steam in anode chamber. Moreover, general relationship between cell voltage and operating temperature is obtained. Estimated cell voltage is almost constant over 600 oC. A fuel cell which migration specie is proton in the electrolyte and works in temperature range from 250 oC to 500 oC, should have better performance than high temperature fuel cells since low Nernst loss.

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