JP3596332B2 - Operating method of stacked fuel cell, stacked fuel cell, and stacked fuel cell system - Google Patents

Description

【００４８】
また、空気極５０、７０側へ持ち込まれる水の量（以下、これを「総水供給量」という）をＷ_{Ｃｉｎ−ｔｏｔａｌ}とおくと、Ｗ_{Ｃｉｎ−ｔｏｔａｌ}は、次の数２の式で表すことができる。
【００４９】
【数２】

【００５０】
ここで、空気極５０、７０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}が、総水供給量Ｗ_{Ｃｉｎ−ｔｏｔａｌ}より少ない場合には、雰囲気中の水分は余剰気味となる。そのため、余分の水が空気極５０、７０の細孔を閉塞してガスの供給を阻害する「フラッディング」が発生し、セル電圧が低下する。逆に、空気極５０、７０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}が総水供給量Ｗ_{Ｃｉｎ−ｔｏｔａｌ}より多い場合には、雰囲気は乾燥気味となる。そのため、電解質膜４６、６６の含水率が低下して膜抵抗が増大する「ドライアップ」が発生し、セル電圧が低下する。
【００５１】
従って、安定した発電性能を維持するためには、これらの収支をバランスさせ、空気極５０、７０側における電解質膜４６、６６の含水率を適正に維持することが重要である。
【００５２】
ところで、数１の式における飽和水蒸気圧ｐ_{Ｗｃ−ｓａｔ}は、空気極側の温度のみで決まるパラメータであり、温度が高いほど大きくなる傾向にある。従って、すべての単電池の構造を同一とし、全ての単電池に対して同一流量の反応ガスを供給する場合であっても、各単電池の温度が均一である時には、飽和水蒸気圧ｐ_{Ｗｃ−ｓａｔ}はすべての単電池で同一となるので、すべての単電池において水収支がバランスし、セル電圧にばらつきが生ずることはない。
【００５３】
しかしながら、例えば図８（ｂ）に示すように、電解質膜１２として固体高分子電解質膜を用い、同一のガス流路構造及び電極構造を有する２個の単電池２を積層する毎に冷媒流路２２ａを設けて積層型燃料電池３８とした場合には、各単電池２の冷却効率に差が生じる。
【００５４】
その結果、各燃料極１４ａ、１４ｂの温度（以下、これを「アノード温」という）及び空気極１６ａ、１６ｂの温度（以下、これを「カソード温」という）には、冷媒流路２２ａからの距離に応じた差が発生する。この温度差は、図８（ａ）に示すように、積層型燃料電池３８の電流密度が大きくなるほど拡大する傾向にある。
【００５５】
このような積層型燃料電池３８に流量及び加湿量が同一である空気を均一に供給した場合には、空気極１６ａ側と空気極１６ｂ側では飽和水蒸気圧ｐ_{Ｗｃ−ｓａｔ}が異なるために、空気極１６ａ、１６ｂ側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}にばらつきが生じ、一部の電解質膜１２において、水収支に過不足が生じる。
【００５６】
そのため、例えば、空気極１６ａ、１６ｂ側の加湿量をカソード温の低い空気極１６ａに合わせて設定した場合において、低電流密度の時には、図９（ａ）に示すように、セル電圧に大きなばらつきは生じないが、図９（ｂ）に示すように、高電流密度の時には、カソード温の高い空気極１６ｂのセル電圧がドライアップにより低下し、積層型燃料電池３８全体の出力が低下する。
【００５７】
また、図１０（ｂ）に示すように、電解質膜１２として固体高分子電解質膜を用い、同一のガス流路構造及び電極構造を有する３個の単電池２を積層する毎に冷媒流路２２ａを設けて積層型燃料電池３９とした場合も同様であり、カソード温及びアノード温には、図１０（ａ）に示すように、冷媒流路２２ａからの距離に応じた温度差が発生する。
【００５８】
そのため、例えば、空気極１６ａ、１６ｂ、１６ｃ側の加湿量をカソード温の最も低い空気極１６ａに合わせて設定した場合には、図１１に示すように、カソード温が高くなるほど、ドライアップによりセル電圧が低下し、積層型燃料電池３９全体の出力が低下する。
【００５９】
これに対し、図１に示す積層型燃料電池４０においては、カソード温の高い空気極（以下、これを「高温空気極」という）７０側の空気流路５６ｃの断面積が、カソード温の低い空気極（以下、これを「低温空気極」という）５０側の空気流路５４ｃの断面積より小さくなっている。
【００６０】
そのため、入り空気中に含まれる水の量（以下、これを「空気加湿量」という）Ｗ_Ｃｉｎを低温空気極５０に合わせて小さく設定した場合であっても、高温空気極７０側では、数１の式に示す空気極入り空気流量（以下、これを単に「空気流量」という）ｆ_{Ａｉｒｉｎ}が小さくなるので、高温空気極７０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}を小さくすることができる。その結果、高温空気極７０側のドライアップに起因するセル電圧の低下が抑制され、積層型燃料電池４０全体の出力を向上させることができる。
【００６１】
同様に、空気加湿量Ｗ_Ｃｉｎを高温空気極７０に合わせて大きく設定した場合であっても、低温空気極５０では、数１の式に示す空気流量ｆ_{Ａｉｒｉｎ}が大きくなるので、低温空気極５０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}を大きくすることができる。その結果、低温空気極５０側のフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池４０全体の出力を向上させることができる。
【００６２】
単位モジュール４２を構成する単電池の積層数を３個以上とする場合も同様であり、カソード温が高くなるほど空気流量が小さくなるように、各単電池の空気流路の構造、すなわち、溝の深さ、断面積等を変化させれば、空気極のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００６３】
次に、本発明の第２の実施の形態に係る積層型燃料電池について説明する。図２に、本発明の第２の実施の形態に係る積層型燃料電池７４の基本構造となる単位モジュール７６の断面図を示す。
【００６４】
図２において、単位モジュール７６は、高温空気極７０側の空気流路５６ｃの溝の深さＤ_Ｃ２を、低温空気極５０側の空気流路５４ｃの溝の深さＤ_Ｃ１と同一とし、空気流路５６ｃの入口側に、多孔体７８を設けた以外は、図１に示す単位モジュール４２と同様の構成を有している。
【００６５】
このような構成を有する単位モジュール７６が積層された積層型燃料電池７４によれば、高温空気極７０側の空気流路５６ｃの流路抵抗は、低温空気極５０側の空気流路５４ｃより大きいので、これに圧力及び加湿量の等しい空気を供給した場合には、高温空気極７０側の空気流量を小さくすることができる。
【００６６】
そのため、空気加湿量Ｗ_Ｃｉｎを低温空気極５０に合わせて小さく設定した場合であっても、高温空気極７０側のドライアップに起因するセル電圧の低下を抑制することができる。同様に、空気加湿量Ｗ_Ｃｉｎを高温空気極７０に合わせて大きく設定した場合であっても、低温空気極５０側のフラッディングに起因するセル電圧の低下を抑制することができる。
【００６７】
単位モジュール７６を構成する単電池の積層数を３個以上とする場合も同様であり、カソード温が高くなるほど空気流量が小さくなるように、各単電池の空気流路の構造、すなわち、多孔体の断面積、大きさ、気孔径、気孔率等を変化させれば、空気極のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００６８】
次に、本発明の第３の実施の形態に係る積層型燃料電池について説明する。図３に、本発明の第３の実施の形態に係る積層型燃料電池８０の基本構造となる単位モジュール８２の断面図を示す。
【００６９】
図３において、単位モジュール８２は、高温空気極７０側の空気流路５６ｃの溝の深さＤ_Ｃ２を、低温空気極５０側の空気流路５４ｃの溝の深さＤ_Ｃ１と同一とし、空気流路５６ｃの入口側に、障害板８４を設けた以外は、図１に示す単位モジュール４２と同様の構成を有している。
【００７０】
このような構成を有する単位モジュール８２が積層された積層型燃料電池８０によれば、図２に示す単位モジュール７６と同様、空気流路５６ｃの流路抵抗が大きくなるので、空気流路５６ｃの空気流量を小さくすることができる。これにより、積層方向の温度分布に起因するドライアップ及びフラッディングが抑制され、積層型燃料電池８０全体の出力を向上させることができる。
【００７１】
単位モジュール８２を構成する単電池の積層数を３個以上とする場合も同様であり、カソード温が高くなるほど空気流量が小さくなるように、各単電池の空気流路の構造、すなわち、障害板の面積、取付角度、形状等を変化させれば、空気極のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００７２】
次に、本発明の第４の実施の形態に係る積層型燃料電池について説明する。図４に、本発明の第４の実施の形態に係る積層型燃料電池８６の基本構造となる単位モジュール８８の断面図を示す。
【００７３】
図４において、単位モジュール８８は、高温空気極７０側の空気流路５６ｃの溝の深さＤ_Ｃ２と、低温空気極５０側の空気流路５４ｃの溝の深さＤ_Ｃ１を同一とし、空気流路５６ｃの出口側、及び空気流路５４ｃの入口側に、それぞれ、突起５６ｄ及び５４ｄを設けた以外は、図１に示す単位モジュール４２と同様の構成を有している。
【００７４】
このような構造を有する単位モジュール８８が積層された積層型燃料電池８６によれば、高温空気極７０側の空気流路５６ｃには、出口側に突起５６ｄが設けられているので、出口側の流路抵抗が増大する。一方、低温空気極５０側の空気流路５４ｃには、入口側に突起５４ｄが設けられているので、入口側の流路抵抗が増大する。その結果、空気流路５６ｃ内の内圧は、空気流路５４ｃ内の内圧より高くなる。
【００７５】
そのため、空気加湿量Ｗ_Ｃｉｎを低温空気極５０に合わせて小さく設定した場合であっても、高温空気極７０では、数１の式に示すカソード側のセル内圧Ｐ_Ｃが大きくなるので、高温空気極７０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}を小さくすることができる。その結果、高温空気極７０のドライアップに起因するセル電圧の低下が抑制され、積層型燃料電池８６全体の出力を向上させることができる。
【００７６】
同様に、空気加湿量Ｗ_Ｃｉｎを高温空気極７０に合わせて大きく設定した場合であっても、低温空気極５０では、数１の式に示すカソード側のセル内圧Ｐ_Ｃが小さくなるので、低温空気極５０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}を大きくすることができる。その結果、低温空気極５０のフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池８６全体の出力を向上させることができる。
【００７７】
単位モジュール８８を構成する単電池の積層数を３個以上とする場合も同様であり、カソード温が高くなるほど空気流路の内圧が高くなるように、各単電池の空気流路の構造、すなわち、突起の大きさ、取付位置等を変化させれば、空気極側のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００７８】
次に、本発明の第５の実施の形態に係る積層型燃料電池について説明する。本発明の第５の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールは、図示はしないが、高温空気極７０側の空気流路５６ｃの溝の深さＤ_Ｃ２と、低温空気極５０側の空気流路５４ｃの溝の深さＤ_Ｃ１を同一とし、高温空気極７０の通気性を、低温空気極５０の通気性より小さくした点以外は、図１に示す単位モジュール４２と同様の構成を有している。
【００７９】
このような電極構造の異なる単電池が積層された積層型燃料電池によれば、高温空気極７０の通気性が小さいために、数２の式に示す電極反応で生成した水Ｗ_ｇｅｎと、高温空気極７０側に移動する水Ｗ_ｄｒａｇが高温空気極７０を通って空気流路５６ｃ側に排出されにくくなる。
【００８０】
そのため、空気加湿量Ｗ_Ｃｉｎを低温空気極５０に合わせて小さく設定した場合には、高温空気極７０側の最大排水量Ｗ_{Ｃｏｕｔ−ＭＡＸ}は、計算上、総水供給量Ｗ_{Ｃｉｎ−ｔｏｔａｌ}より大きくなるが、実際に排出される水分量は、Ｗ_{Ｃｉｎ−ｔｏｔａｌ}より小さくなる。その結果、高温空気極７０側のドライアップに起因するセル電圧の低下が抑制され、積層型燃料電池全体の出力を向上させることができる。
【００８１】
同様に、空気加湿量Ｗ_Ｃｉｎを高温空気極７０に合わせて大きく設定した場合であっても、低温空気極５０の通気性が大きいために、低温空気極５０からの水の排出が促進される。その結果、低温空気極５０のフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池全体の出力を向上させることができる。
【００８２】
単位モジュールを構成する単電池の積層数を３個以上とする場合も同様であり、カソード温が高くなるほど空気極の通気性が小さくなるように、各単電池の空気極の電極構造、すなわち、拡散層の厚さ、気孔径、気孔率等を変化させれば、空気極側のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００８３】
以上のように、積層型燃料電池に備えられる各単電池の温度ばらつきに起因する空気極側のドライアップ及びフラッディングを抑制するためには、空気極側の水収支をバランスさせ、電解質膜の含水状態の不均一を解消することが有効である。この点は、燃料極側も同様である。以下に、燃料極側の水収支をバランスさせるための具体的方法について説明する。
【００８４】
図５に、本発明の第６の実施の形態に係る積層型燃料電池９０の基本構造となる単位モジュール９２の断面図を示す。図５において、単位モジュール９２は、アノード温の高い燃料極（以下、これを「高温燃料極」という）４８側の燃料流路５６ａの溝の深さＤ_Ａ１が、アノード温の低い燃料極（以下、これを「低温燃料極」という）６８側の燃料流路５８ａの溝の深さＤ_Ａ２より大きくなっている。
【００８５】
なお、本実施の形態の場合、高温空気極７０側の空気流路５６ｃの溝の深さＤ_Ｃ２は、低温空気極５０側の空気流路５４ｃの溝の深さＤ_Ｃ１と同一になっている。また、その他の点は、図１に示す単位モジュール４２と同様の構成を有している。
【００８６】
次に、本発明の第６の実施の形態に係る積層型燃料電池９０の作用について説明する。単電池４４、４５への水の供給、及び単電池４４、４５からの水の排出が、すべて水蒸気の形で行われるものと仮定すると、燃料極４８、６８側に供給される水の供給量は、燃料入りガス中に含まれる水分量（以下、これを「燃料加湿量」という）に等しい。そこで、燃料加湿量をＷ_Ａｉｎとおくと、Ｗ_Ａｉｎは、次の数３の式で表すことができる。
【００８７】
【数３】

【００８８】
また、燃料極出ガスと共に燃料電池外へ排出される水の量（以下、これを「総排水量」という）をＷ_Ａｏｕｔとおくと、総排水量Ｗ_Ａｏｕｔは、次の数４の式で表すことができる。
【００８９】
【数４】

【００９０】
さらに、燃料極４８、６８側から電解質膜４６、６６に補給される水の量（以下、これを「補給水量」という）をＷ_{Ａｇａｉｎ}とおくと、補給水量Ｗ_{Ａｇａｉｎ}は、数３の式及び数４の式より、次の数５の式で表すことができる。
【００９１】
【数５】

【００９２】
ここで、燃料極４８、６８側の総排水量Ｗ_Ａｏｕｔが、燃料加湿量Ｗ_Ａｉｎより少ない場合には、燃料極４８、６８側の水分は、余剰気味となる。逆に、Ｗ_ＡｏｕｔがＷ_Ａｉｎより多い場合には、雰囲気は乾燥気味となる。従って、安定した発電性能を維持するためには、これらの収支をバランスさせ、燃料極４８、６８側における電解質膜４６、６６の含水率を適正に維持することが重要である。
【００９３】
ところで、数４の式における飽和水蒸気圧ｐ_{ＷＡ−ｓａｔ}は、アノード温のみで決まるパラメータであり、温度が高いほど大きくなる。従って、すべての単電池の燃料流路の構造及び電極構造が同一である積層型燃料電池に対し、加湿量が同一である燃料ガスを均一に供給した場合において、アノード温に差が発生した時には、各燃料極側の飽和水蒸気圧ｐ_{ＷＡ−ｓａｔ}が異なるために、燃料極側の総排水量Ｗ_Ａｏｕｔにばらつきが生じ、一部の電解質膜において、水収支に過不足が生じる。その結果、ドライアップ又はフラッディングにより、セル電圧にばらつきが発生する。
【００９４】
これに対し、図５に示す積層型燃料電池９０によれば、高温燃料極４８側の燃料流路５６ａの断面積が、低温燃料極６８の燃料流路５８ａの断面積より大きくなっているので、高温燃料極４８側の燃料極入り燃料流量（以下、これを単に「燃料流量」という）ｆ_Ｈｉｎを大きくすることができる。
【００９５】
そのため、入り燃料ガス中の水のモル分率（以下、これを「入水モル分率」という）ｘを低温燃料極６８に合わせて小さく設定した場合であっても、高温燃料極４８では、数３の式に示す燃料流量ｆ_Ｈｉｎが大きくなるので、燃料加湿量Ｗ_Ａｉｎ、すなわち補給水量Ｗ_{Ａｇａｉｎ}を大きくすることができる。
【００９６】
これは、通常、積層型燃料電池においては、反応で消費された水素の量Ｃ_Ｈ２が一定で、かつ入水モル分率ｘが出ガス中の水のモル分率Ｘより大きくなるように制御されているためである。その結果、高温燃料極４８のドライアップに起因するセル電圧の低下が抑制され、積層型燃料電池９０全体の出力を向上させることができる。
【００９７】
同様に、入水モル分率ｘを高温燃料極４８に合わせて大きく設定した場合であっても、低温空気極５０では、数３の式に示す燃料流量ｆ_Ｈｉｎが小さくなるので、燃料加湿量Ｗ_Ａｉｎ、すなわち補給水量Ｗ_{Ａｇａｉｎ}を小さくすることができる。その結果、低温燃料極６８のフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池９０全体の出力を向上させることができる。
【００９８】
単位モジュール９２を構成する単電池の積層数を３個以上とする場合も同様であり、アノード温が高くなるほど燃料流量が大きくなるように、各単電池の燃料流路の構造、すなわち、溝の深さ、断面積等を変化させれば、燃料極側のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【００９９】
次に、本発明の第７の実施の形態に係る積層型燃料電池について説明する。図６に、本発明の第７の実施の形態に係る積層型燃料電池９４の基本構造となる単位モジュール９６の断面図を示す。
【０１００】
図６において、単位モジュール９６は、高温燃料極４８側の燃料流路５６ａの溝の深さＤ_Ａ１と、低温燃料極６８側の燃料流路５８ａの溝の深さＤ_ＣＡ２を同一とし、燃料流路５６ａの出口側、及び燃料流路５８ａの入口側に、それぞれ、突起５６ｆ及び５８ｆを設けた以外は、図５に示す単位モジュール９２と同様の構成を有している。
【０１０１】
このような構造を有する単位モジュール９６が積層された積層型燃料電池９４によれば、高温燃料極４８側の燃料流路５６ａには、出口側に突起５６ｆが設けられているので、出口側の流路抵抗が増大する。一方、低温燃料極６８側の燃料流路５８ａには、入口側に突起５８ｆが設けられているので、入口側の流路抵抗が増大する。その結果、燃料流路５６ａ内の内圧は、燃料流路５８ａ内の内圧より高くなる。
【０１０２】
そのため、燃料加湿量Ｗ_Ａｉｎを低温燃料極６８に合わせて小さく設定した場合であっても、高温燃料極４８側では、数４の式に示すアノード側のセル内圧Ｐ_Ａが大きくなるので、高温燃料極４８側の総排水量Ｗ_Ａｏｕｔを小さくすることができる。その結果、高温燃料極４８のドライアップに起因するセル電圧の低下が抑制され、積層型燃料電池９４全体の出力が向上する。
【００１０３】
同様に、燃料加湿量Ｗ_Ａｉｎを高温燃料極４８に合わせて大きく設定した場合であっても、低温燃料極６８側では、数４の式に示すアノード側のセル内圧Ｐ_Ａが小さくなるので、低温燃料極６８側の総排水量Ｗ_Ａｏｕｔを大きくすることができる。その結果、低温燃料極６８のフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池９４全体の出力が向上する。
【０１０４】
単位モジュール９６を構成する単電池の積層数を３個以上とする場合も同様であり、アノード温が高くなるほど燃料流路の内圧が大きくなるように、各単電池の燃料流路の構造、すなわち、突起の大きさ、取付位置等を変化させれば、燃料極側のドライアップ又はフラッディングに起因するセル電圧の低下を抑制することができる。
【０１０５】
以上のように、積層型燃料電池において発生する各単電池の温度ばらつきに起因するドライアップ及びフラッディングを抑制するためには、燃料極側の水収支をバランスさせ、各電解質膜の含水状態の不均一を解消する必要がある。そのためには、各単電池の燃料流路の構造又は燃料極の電極構造を、温度環境に応じて変化させることが有効である。
【０１０６】
次に、本発明に係る燃料電池システムについて説明する。図１２に、本発明に係る燃料電池システムのブロック構成図を示す。図１２において、燃料電池システム１００は、積層型燃料電池１０２と、反応ガス供給装置１０４と、加湿量制御装置１０６と、反応ガス供給制御装置１０８と、電池作動状況検出装置１１０とを備えている。
【０１０７】
積層型燃料電池１０２は、複数個の単電池を積層した単位モジュールと、この単位モジュールを積層する毎に設けられる冷却手段とを備えている。図１３に積層型燃料電池１０２の断面図を示す。図１３に例示する積層型燃料電池１０２において、単位モジュール１０２ｃは、２個の単電池１０２ａ及び１０２ｂが積層されたものからなり、単位モジュール１０２ｃ間には、冷却装置１０２ｄが配置されている。
【０１０８】
単位モジュール１０２ｃに備えられる単電池１０２ａ及び１０２ｂは、それぞれ温度環境が異なるので、これらを単電池１０２ａのグループ（以下、これを「グループ１」という）と単電池１０２ｂのグループ（以下、これを「グループ２」という）に分け、分岐された空気マニホールド及び燃料マニホールド（図１３中、実線及び点線で表示）を介して、空気及び燃料ガスを分配するようになっている。
【０１０９】
図１４に、積層型燃料電池１０２の斜視図を示す。図１４において、積層型燃料電池１０２には、２つの空気導入口１０２ｆ、１０２ｇと、２つの空気排出口１０２ｈ、１０２ｉが設けられている。この内、空気導入口１０２ｆと空気排出口１０２ｈは、ともにグループ１に属する各単電池１０２ａの空気流路につながっており、分岐された空気マニホールドの一方から供給される空気を、空気導入口１０２ｆから各単電池１０２ａに配流し、各単電池１０２ａから排出されるガスを集めて、空気排出口１０２ｈから排出するようになっている。
【０１１０】
同様に、空気導入口１０２ｇと空気排出口１０２ｉは、ともにグループ２に属する各単電池１０２ｂの空気流路につながっており、分岐された空気マニホールドの他方から供給される空気を、空気導入口１０２ｇから各単電池１０２ｂに配流し、各単電池１０２ｂから排出されるガスを集めて、空気排出口１０２ｉから排出するようになっている。
【０１１１】
また、積層型燃料電池１０２には、２つの燃料導入口１０２ｊ、１０２ｋと、２つの燃料排出口１０２ｌ、１０２ｍが設けられている。この内、燃料導入口１０２ｊと燃料排出口１０２ｌは、ともにグループ１に属する各単電池１０２ａの燃料流路につながっており、分岐された燃料マニホールドの一方から供給される改質ガスを、燃料導入口１０２ｊから各単電池１０２ａに配流し、各単電池１０２ａから排出されるガスを集めて、燃料排出口１０２ｌから排出するようになっている。
【０１１２】
同様に、燃料導入口１０２ｋと燃料排出口１０２ｍは、ともにグループ２に属する各単電池１０２ｂの燃料流路につながっており、分岐された燃料マニホールドの他方から供給される改質ガスを、燃料導入口１０２ｋから各単電池１０２ｂに配流し、各単電池１０２ｂから排出されるガスを集めて、燃料排出口１０２ｍから排出するようになっている。
【０１１３】
なお、本発明に係る燃料電池システム１００において、単位モジュール１０２ｃを構成する単電池１０２ａ、１０２ｂのガス流路構造及び電極構造は、同一であっても良く、あるいは、その温度に応じて、異なる構造を有していても良い。また、分岐されたマニホールドから供給される反応ガスを各単電池グループに分配するための具体的構造は、図１４に例示する構造に限定されるものではなく、また、冷却装置１０２ｄについても、図１３に例示する構造に限定されるものではない。
【０１１４】
さらに、本発明は、電解質膜の含水率の管理が必要な燃料電池、具体的には、固体高分子型燃料電池、リン酸型燃料電池又はアルカリ型燃料電池に対して適用するのが好ましい。特に、固体高分子型燃料電池に対して本発明を適用した場合には、単位体積当たりの出力を低下させることなく、電解質膜の水収支の不均一あるいは反応ガスの相対的な過不足に起因する出力低下が軽減されるので、車載動力源に適した燃料電池システムが得られるという利点がある。
【０１１５】
反応ガス供給装置１０４は、各単電池の燃料極に所定量の改質ガスを供給するための燃料改質器１０４ａ、燃料供給装置１０４ｂ及び水供給装置１０４ｃと、積層型燃料電池１０２の空気極に所定量の空気を供給するための空気供給装置１０４ｄと、電池作動状況検出装置１１０により検出された積層型燃料電池１０２の作動状況に基づき、改質ガス及び空気の総供給量を制御する発電量制御装置１０４ｅからなっている。
【０１１６】
燃料改質器１０４ａは、周知のように、メタノール等からなる燃料蒸気と水蒸気とを触媒存在下で改質反応させることにより、水素を主成分とする改質ガスを発生させる装置であり、改質反応に必要な燃料蒸気と水蒸気は、それぞれ、燃料供給装置１０４ｂ及び水供給装置１０４ｃから供給されるようになっている。
【０１１７】
加湿量制御装置１０６は、積層型燃料電池１０２に供給される改質ガス及び空気に所定量の水分を添加して加湿すると共に、温度環境の異なる単電池グループ毎に、その加湿量を個別に制御するための装置である。そのため、加湿量制御装置１０６は、２つの燃料加湿量制御装置１０６ａ及び１０６ｂと、２つの空気加湿量制御装置１０６ｃ及び１０６ｄからなっている。
【０１１８】
燃料改質器１０４ａと燃料加湿量制御装置１０６ａ及び１０６ｂとは、分岐された燃料マニホールドを介して接続されており、燃料改質器１０４ａで発生させた改質ガスを、燃料加湿量制御装置１０６ａ及び１０６ｂに分配するようになっている。また、燃料加湿量制御装置１０６ａ及び１０６ｂは、それぞれ、図１４に示すグループ１の燃料導入口１０２ｊ及びグループ２の燃料導入口１０２ｋに接続されいる。
【０１１９】
同様に、空気供給装置１０４ｄと空気加湿量制御装置１０６ｃ及び１０６ｄは、分岐された空気マニホールドを介して接続されており、空気供給装置１０４ｄにより供給される空気を、空気加湿量制御装置１０６ｃ及び１０６ｄに分配するようになっている。また、空気加湿量制御装置１０６ｃ及び１０６ｄは、それぞれ、図１４に示すグループ１の空気導入口１０２ｆ及びグループ２の空気導入口１０２ｇに接続されている。
【０１２０】
なお、燃料加湿量制御装置１０６ａ、１０６ｂ、及び空気加湿量制御装置１０６ｃ及び１０６ｄに備えられる加湿器の構造については特に限定されるものではない。すなわち、水蒸気を用いて加湿する加湿器でも良く、あるいは、ミストを用いて加湿する加湿器でも良い。
【０１２１】
反応ガス供給制御装置１０８は、温度環境の異なる単電池グループ毎に、反応ガスの流量及び／又は圧力を個別に制御するための装置である。そのため、反応ガス供給制御装置１０８は、２つの燃料ガス供給制御装置１０８ａ及び１０８ｂと、２つの空気供給制御装置１０８ｃ及び１０８ｄからなっている。
【０１２２】
燃料ガス供給制御装置１０８ａ及び１０８ｂは、それぞれ、図１４に示すグループ１の燃料排出口１０２ｌ及びグループ２の燃料排出口１０２ｍに接続されいる。また、空気供給制御装置１０８ｃ及び１０８ｄは、それぞれ、図１４に示すグループ１の空気排出口１０２ｈ及びグループ２の空気排出口１０２ｉに接続されている。
【０１２３】
なお、各単電池に供給される反応ガスの流量及び圧力を個別に制御する方法としては、種々の方法が考えられる。具体的には、反応ガス供給装置１０４に備えられるポンプ回転数等を調節することにより、燃料ガス及び空気の総供給量を制御すると共に、反応ガス供給制御装置１０８に備えられるバルブ開度等を調節することにより、各反応ガス流路の流路抵抗を個別に制御すれば良い。
【０１２４】
また、図１２において、反応ガス供給制御装置１０８（燃料ガス供給制御装置１０８ａ、１０８ｂ、及び空気供給制御装置１０８ｃ、１０８ｄ）は、いずれも、積層型燃料電池１０２の排出口側に設けられているが、反応ガス供給制御装置１０８を導入口側、すなわち、燃料加湿量制御装置１０６ａ、１０６ｂと積層型燃料電池１０２の間、及び空気加湿量制御装置１０６ｃ、１０６ｄと積層型燃料電池１０２の間にそれぞれ設け、これによって反応ガスの流量及び圧力を個別に制御するようにしてもよい。
【０１２５】
あるいは、反応ガス供給制御装置１０８を積層型燃料電池１０２の導入口側及び排出口側の双方に設け、これらを用いて反応ガスの流量及び圧力を個別に制御するようにしてもよい。
【０１２６】
電池作動状況検出装置１１０は、積層型燃料電池１０２の作動状況を検出する機能と、測定された作動状況に基づき、各単電池のセル電圧のばらつきを小さくするために必要なガス流量、圧力、及び加湿量を算出する機能とを備えている。
【０１２７】
ここで、「作動状況」とは、具体的には、セル電圧、電解質膜の抵抗値、セル温度、セル内圧、並びに排出ガス中に含まれる水素濃度及び酸素濃度をいう。また、これらの作動状況は、グループ１に属する単電池１０２ａ及びグループ２に属する単電池１０２ｂについて、それぞれ個別に検出されるようになっている。
【０１２８】
さらに、電池作動状況検出装置１１０で算出されたガス流量等の制御パラメータは、発電量制御装置１０４ｅ、燃料加湿量制御装置１０６ａ、１０６ｂ、空気加湿量制御装置１０６ｃ、１０６ｄ、燃料ガス供給制御装置１０８ａ、１０８ｂ、及び空気供給制御装置１０８ｃ、１０８ｄに出力されるようになっている。
【０１２９】
なお、電池作動状況検出装置１１０による作動状況の検出は、積層された全ての単電池について行っても良く、あるいは、図１３に示すように、各グループの中から選ばれる代表的な１又は２以上の単電池について行っても良い。
【０１３０】
次に、図１２に示す燃料電池システム１００の一般的動作について説明する。まず、電池作動状況検出装置１１０により積層型燃料電池１０２の作動状況を監視する。そして、グループ１に属する単電池１０２ａと、グループ２に属する単電池１０２ｂのセル電圧の間に差が生じた場合には、電池作動状況検出装置１１０において、セル電圧の差を小さくするために必要な改質ガス及び空気の流量及び圧力、並びに改質ガス及び空気への加湿量が算出される。
【０１３１】
次いで、算出された改質ガス及び空気の流量及び圧力が、発電量制御装置１０２ｅ並びに燃料ガス供給制御装置１０８ａ、１０８ｂ及び空気供給制御装置１０８ｃ、１０８ｄに、また、算出された加湿量が燃料加湿量制御装置１０６ａ、１０６ｂ、及び空気加湿量制御装置１０６ｃ、１０６ｄにそれぞれ出力される。
【０１３２】
発電量制御装置１０４ｅでは、算出された改質ガスの流量及び圧力に基づき、燃料供給装置１０４ｂ及び水供給装置１０４ｃに制御信号を出力し、それぞれ、所定量の改質ガスを発生させるに必要な燃料蒸気及び水蒸気を燃料改質器１０４ａに供給させる。
【０１３３】
燃料改質器１０４ａでは、供給された燃料蒸気及び水蒸気から、改質反応により、改質ガスが発生する。発生した改質ガスは、分岐された燃料マニホールドを介して、それぞれ燃料加湿量制御装置１０６ａ及び１０６ｂに分配される。この時、燃料加湿量制御装置１０６ａ及び１０６ｂに分配される改質ガスの比率及び圧力は、積層型燃料電池１０２の排気側に設けられる燃料ガス供給制御装置１０８ａ、１０８ｂにより、個別に制御される。
【０１３４】
燃料加湿量制御装置１０６ａ及び１０６ｂに改質ガスが分配されると、電池作動状況検出装置１１０で算出された加湿量に基づき、所定量の水分がそれぞれ添加される。そして、加湿量が個別に制御された改質ガスは、それぞれ、グループ１に属する各単電池１０２ａの燃料極及びグループ２に属する各単電池１０２ｂの燃料極に供給される。
【０１３５】
同様に、空気供給装置１０４ｄでは、電池作動状況検出装置１１０で算出された空気の流量及び圧力に基づき、所定量の空気を積層型燃料電池１０２に供給する。供給された空気は、分岐された空気マニホールドを介して、それぞれ空気加湿量制御装置１０６ｃ及び１０６ｄに分配される。この時、空気加湿量制御装置１０６ｃ及び１０６ｄに分配される空気の比率及び圧力は、積層型燃料電池１０２の排気側に設けられる空気供給制御装置１０８ｃ、１０８ｄにより、個別に制御される。
【０１３６】
空気加湿量制御装置１０６ｃ及び１０６ｄに空気が分配されると、電池作動状況検出装置１１０で算出された加湿量に基づき、所定量の水分がそれぞれ添加される。そして、加湿量が個別に制御された空気は、それぞれ、グループ１に属する各単電池１０２ａの空気極及びグループ２に属する各単電池１０２ｂの空気極に供給される。
【０１３７】
積層型燃料電池１０２のグループ１に属する各単電池１０２ａ、及びグループ２に属する各単電池１０２ｂに、それぞれ流量、圧力及び加湿量が個別に制御された改質ガス及び空気が供給されると、グループ１に属する単電池１０２ａのセル電圧及び／又はグループ２に属する単電池１０２ｂのセル電圧が変化する。そこで、電池作動状況検出装置１１０により、変化した各単電池のセル電圧を再度検出し、これらを対比する。そして、単電池１０２ａと単電池１０２ｂのセル電圧の差が所定の値以下となるまで、上述した制御が繰り返される。
【０１３８】
次に、温度環境の異なる各単電池のセル電圧の差を小さくするための具体的な運転方法について説明する。図１５に、その制御フローチャートの一例を示す。初めに、図１５に示すステップ１（以下、単に「Ｓ１」という）において、グループ１に属する単電池１０２ａのセル電圧Ｖ_１と、グループ２に属する単電池１０２ｂのセル電圧Ｖ_２が電池作動状況検出装置１１０により検出される。
【０１３９】
次いで、Ｓ２において、セル電圧Ｖ_１とセル電圧Ｖ_２が等しいか否かが判断される。セル電圧Ｖ_１とセル電圧Ｖ_２が等しい場合（Ｓ２：ＹＥＳ）には、Ｓ１に戻り、セル電圧Ｖ_１とセル電圧Ｖ_２の変動が生じるまで上述のＳ１〜Ｓ２の各ステップが繰り返される。一方、セル電圧Ｖ_１とセル電圧Ｖ_２が等しくない場合（Ｓ２：ＮＯ）には、各単電池の反応ガス供給量に相対的な過不足が生じていることを示しているので、次にＳ３に進む。
【０１４０】
Ｓ３では、セル電圧Ｖ_１がセル電圧Ｖ_２より大きいか否かが判断される。セル電圧Ｖ_１がセル電圧Ｖ_２より大きい場合（Ｓ３：ＹＥＳ）には、Ｓ４に進み、グループ１に属する単電池１０２ａの空気極から排出されるガス中の酸素濃度（以下、これを「酸素濃度Ｘ_０１」という）と、グループ２に属する単電池１０２ｂの空気極から排出されるガス中の酸素濃度（以下、これを「酸素濃度Ｘ_Ｏ２」という）が電池作動状況検出装置１１０により検出される。
【０１４１】
次いで、Ｓ５において、酸素濃度Ｘ_０２が酸素濃度Ｘ_Ｏ１以上であるか否かが判断される。酸素濃度Ｘ_０２が酸素濃度Ｘ_Ｏ１以上でない場合（Ｓ５：ＮＯ）には、単電池１０２ｂに供給される空気が相対的に不足したためにセル電圧Ｖ_２が低下したことを示している。そこで、この場合にはＳ６へ進み、空気供給制御装置１０８ｄを用いて、単電池１０２ｂに供給される空気流量（以下、これを「空気流量ｆ_{Ａｉｒｉｎ}（２）」という）を増加させる。
【０１４２】
一方、酸素濃度Ｘ_０２が酸素濃度Ｘ_Ｏ１以上である場合（Ｓ５：ＹＥＳ）には、電圧Ｖ_２の低下が単電池１０２ｂに供給される空気量の相対的な不足によるものではないことを示しているので、そのままＳ７に進む。
【０１４３】
Ｓ７では、グループ１に属する単電池１０２ａの燃料極から排出されるガス中の水素濃度（以下、これを「水素濃度Ｘ_Ｈ１」という）と、グループ２に属する単電池１０２ｂの燃料極から排出されるガス中の水素濃度（以下、これを「水素濃度Ｘ_Ｈ２」という）が電池作動状況検出装置１１０により検出される。
【０１４４】
次いで、Ｓ８では、水素濃度Ｘ_Ｈ２が水素濃度Ｘ_Ｈ１以上であるか否かが判断される。水素濃度Ｘ_Ｈ２が水素濃度Ｘ_Ｈ１以上でない場合（Ｓ８：ＮＯ）には、単電池１０２ｂに供給される燃料が相対的に不足したためにセル電圧Ｖ_２が低下したことを示している。そこで、この場合にはＳ９へ進み、燃料ガス供給制御装置１０８ｂを用いて、単電池１０２ｂに供給される燃料流量（以下、これを「燃料流量ｆ_Ｈｉｎ（２）」という）を増加させる。
【０１４５】
一方、電圧Ｖ_２の低下が空気流量の不均一にのみ起因する場合には、Ｓ８において、水素濃度Ｘ_Ｈ２が水素濃度Ｘ_Ｈ１以上であると判断される（Ｓ８：ＹＥＳ）ので、この場合には、Ｓ１に戻る。そして、セル電圧Ｖ_１とセル電圧Ｖ_２が一致するまで、上述したＳ１〜Ｓ９の各ステップが繰り返されることになる。
【０１４６】
また、Ｓ３において、セル電圧Ｖ_１がセル電圧Ｖ_２より大きくないと判断された場合（Ｓ３：ＮＯ）には、Ｓ１０へ進み、そこで、酸素濃度Ｘ_０１と酸素濃度Ｘ_Ｏ２が電池作動状況検出装置１１０により検出される。
【０１４７】
次いで、Ｓ１１において、酸素濃度Ｘ_０１が酸素濃度Ｘ_Ｏ２以上であるか否かが判断される。酸素濃度Ｘ_０１が酸素濃度Ｘ_Ｏ２以上でない場合（Ｓ１１：ＮＯ）には、単電池１０２ａに供給される空気が相対的に不足したためにセル電圧Ｖ_１が低下したことを示している。そこで、この場合にはＳ１２へ進み、空気供給制御装置１０８ｃを用いて、単電池１０２ａに供給される空気流量（以下、これを「空気流量ｆ_{Ａｉｒｉｎ}（１）」という）を増加させる。
【０１４８】
一方、酸素濃度Ｘ_０１が酸素濃度Ｘ_Ｏ２以上である場合（Ｓ１１：ＹＥＳ）には、セル電圧Ｖ_１の低下が単電池１０２ａに供給される空気量の相対的に不足によるものではないことを示しているので、そのままＳ１３に進む。Ｓ１３では、水素濃度Ｘ_Ｈ１と水素濃度Ｘ_Ｈ２が電池作動状況検出装置１１０により検出される。
【０１４９】
次いで、Ｓ１４では、水素濃度Ｘ_Ｈ１が水素濃度Ｘ_Ｈ２以上であるか否かが判断される。水素濃度Ｘ_Ｈ１が水素濃度Ｘ_Ｈ２以上でない場合（Ｓ１４：ＮＯ）には、単電池１０２ａに供給される燃料ガスが相対的に不足したためにセル電圧Ｖ_１が低下したことを示している。そこで、この場合にはＳ１５へ進み、燃料ガス供給制御装置１０８ａを用いて、単電池１０２ａに供給される燃料流量（以下、これを「燃料流量ｆ_Ｈｉｎ（１）」という）を増加させる。
【０１５０】
一方、セル電圧Ｖ_１の低下が空気流量の不均一にのみ起因する場合には、Ｓ１４において、水素濃度Ｘ_Ｈ１が水素濃度Ｘ_Ｈ２以上であると判断される（Ｓ１４：ＹＥＳ）ので、この場合には、Ｓ１に戻る。そして、セル電圧Ｖ_１とセル電圧Ｖ_２が一致するまで、上述したＳ１〜Ｓ３及びＳ１０〜Ｓ１５の各ステップが繰り返される。
【０１５１】
以上のように、図１５に示した積層型燃料電池の運転方法によれば、温度環境の異なる単電池グループ毎に検出された酸素濃度及び水素濃度に応じて、空気流量及び燃料流量を個別に制御しているので、積層型燃料電池に備えられる各単電池のガス流路構造及び電極構造を同一とした場合であっても、ガス流量の相対的な過不足に起因するセル電圧の低下を抑制することができる。また、これによって、積層型燃料電池１０２のエネルギー効率を向上させることができる。
【０１５２】
次に、温度環境の異なる各単電池のセル電圧の差が小さくなるように、ガス流量及び加湿量の双方を増減させる具体的な運転方法について説明する。図１６に、その制御フローチャートの一例を示す。初めに、図１６に示すＳ２１において、グループ１に属する単電池１０２ａのセル電圧Ｖ_１と、グループ２に属する単電池１０２ｂのセル電圧Ｖ_２が電池作動状況検出装置１１０により検出される。
【０１５３】
次いで、Ｓ２２において、セル電圧Ｖ_１とセル電圧Ｖ_２が等しいか否かが判断される。セル電圧Ｖ_１とセル電圧Ｖ_２が等しい場合（Ｓ２２：ＹＥＳ）には、Ｓ２１に戻り、セル電圧Ｖ_１とセル電圧Ｖ_２の変動が生じるまで上述のＳ２１〜Ｓ２２の各ステップが繰り返される。一方、セル電圧Ｖ_１とセル電圧Ｖ_２が等しくない場合（Ｓ２２：ＮＯ）には、各単電池の反応ガス供給量及び／又は加湿量に相対的な過不足が発生したことを示しているので、Ｓ２３に進む。
【０１５４】
Ｓ２３では、セル電圧Ｖ_１がセル電圧Ｖ_２より大きいか否かが判断される。セル電圧Ｖ_１がセル電圧Ｖ_２より大きい場合（Ｓ２３：ＹＥＳ）には、Ｓ２４に進み、そこで、単電池１０２ａの電解質膜の膜抵抗Ｒ_１と、単電池１０２ｂの電解質膜の膜抵抗Ｒ_２が電池作動状況検出装置１１０により検出される。さらに、Ｓ２５において、膜抵抗Ｒ_１が膜抵抗Ｒ_２以上であるか否かが判断される。
【０１５５】
膜抵抗Ｒ_１が膜抵抗Ｒ_２以上でない場合（Ｓ２５：ＮＯ）、すなわち膜抵抗Ｒ_２の方が大きい場合には、単電池１０２ｂに供給される水分量よりも単電池１０２ｂから排出される水分量の方が多くなったために、単電池１０２ｂにおいてドライアップが発生し、これによってセル電圧Ｖ_２が低下したことを示している。そこで、この場合には、Ｓ２６に進む。
【０１５６】
Ｓ２６では、単電池１０２ｂにおける水分量の不足を解消するための手段が実行される。例えば、セル電圧Ｖ_２の低下が、単電池１０２ｂの空気極側における水分量の不足に起因する場合には、空気供給制御装置１０８ｄを用いて、空気流量ｆ_{ａｉｒｉｎ}（２）を減少させればよい。これにより、単電池１０２ｂの空気極側から排出される水分量を少なくすることができる。あるいは、空気加湿量制御装置１０６ｄを用いて、単電池１０２ｂの空気加湿量Ｗ_Ｃｉｎ（２）を増加させてもよい。これにより、単電池１０２ｂの空気極側に供給される水分量を増加させることができる。
【０１５７】
また、セル電圧Ｖ_２の低下が、単電池１０２ｂの燃料極側における水分量の不足に起因する場合には、燃料加湿量制御装置１０６ｂを用いて、単電池１０２ｂの燃料加湿量Ｗ_Ａｉｎ（２）を増加させ、これによって燃料極側に供給される水分量を増加させてもよい。
【０１５８】
さらに、空気流量ｆ_{ａｉｒｉｎ}（２）、空気加湿量Ｗ_Ｃｉｎ（２）及び燃料加湿量Ｗ_Ａｉｎ（２）から選ばれる少なくとも１以上の制御パラメータを組み合わせ、単電池１０２ｂの水収支の均衡が保たれるように、これらを同時に制御してもよい。
【０１５９】
一方、膜抵抗Ｒ_１が膜抵抗Ｒ_２以上である場合（Ｓ２５：ＹＥＳ）、すなわち膜抵抗Ｒ_２の方が小さい場合には、単電池１０２ｂから排出される水分量よりも単電池１０２ｂに供給される水分量の方が多くなったために、単電池１０２ｂにおいてフラッディングが発生し、これによってセル電圧Ｖ_２が低下したことを示している。そこで、この場合には、Ｓ２７に進む。
【０１６０】
Ｓ２７では、単電池１０２ｂにおける過剰水分を排除するための手段が実行される。例えば、セル電圧Ｖ_２の低下が、単電池１０２ｂの空気極側における過剰水分に起因する場合には、空気流量ｆ_{ａｉｒｉｎ}（２）を増加させ、空気極側から排出される水分量を増加さればよい。あるいは、空気加湿量Ｗ_Ｃｉｎ（２）を減少させ、空気極側に供給される水分量を減少させてもよい。
【０１６１】
また、セル電圧Ｖ_２の低下が、単電池１０２ｂの燃料極側における過剰水分に起因する場合には、燃料加湿量Ｗ_Ａｉｎ（２）を減少させ、燃料極側に供給される水分量を減少させてもよい。さらに、空気流量ｆ_{ａｉｒｉｎ}（２）、空気加湿量Ｗ_Ｃｉｎ（２）及び燃料加湿量Ｗ_Ａｉｎ（２）から選ばれる少なくとも１以上の制御パラメータを組み合わせ、単電池１０２ｂの水収支の均衡が保たれるように、これらを同時に制御してもよい。
【０１６２】
Ｓ２６あるいはＳ２７において、空気流量ｆ_{ａｉｒｉｎ}（２）、空気加湿量Ｗ_Ｃｉｎ（２）及び燃料加湿量Ｗ_Ａｉｎ（２）から選ばれる少なくとも１以上が制御された後、Ｓ２１に戻る。そして、セル電圧Ｖ_１とセル電圧Ｖ_２が一致するまで、上述したＳ２１〜Ｓ２７の各ステップが繰り返される。
【０１６３】
これに対しＳ２３において、セル電圧Ｖ_１がセル電圧Ｖ_２より大きくないと判断された場合（Ｓ２３：ＮＯ）には、Ｓ２８に進み、そこで、膜抵抗Ｒ_１と膜抵抗Ｒ_２が検出される。さらに、Ｓ２９において、膜抵抗Ｒ_１が膜抵抗Ｒ_２以下であるか否かが判断される。
【０１６４】
膜抵抗Ｒ_１が膜抵抗Ｒ_２以下でない場合（Ｓ２９：ＮＯ）、すなわち膜抵抗Ｒ_１の方が大きい場合には、単電池１０２ａにおいて水分量が不足し、これによってセル電圧Ｖ_１が低下したことを示している。そこで、この場合には、Ｓ３０に進み、単電池１０２ａにおける水分量の不足を解消するための手段が実行される。
【０１６５】
例えば、セル電圧Ｖ_１の低下が、単電池１０２ａの空気極側における水分量の不足に起因する場合には、空気供給制御装置１０８ｃを用いて空気流量ｆ_{ａｉｒｉｎ}（１）を減少させるか、あるいは、空気加湿量制御装置１０６ｃを用いて空気加湿量Ｗ_Ｃｉｎ（１）を増加させればよい。
【０１６６】
また、セル電圧Ｖ_１の低下が、単電池１０２ａの燃料極側における水分量の不足に起因する場合には、燃料加湿量制御装置１０６ａを用いて燃料加湿量Ｗ_Ａｉｎ（１）を増加させればよい。さらに、これらの中から選ばれる１以上の制御パラメータを組み合わせ、単電池１０２ａの水収支の均衡が保たれるように、これらを同時に制御してもよい。
【０１６７】
一方、膜抵抗Ｒ_１が膜抵抗Ｒ_２以下である場合（Ｓ２９：ＹＥＳ）、すなわち膜抵抗Ｒ_１の方が小さい場合には、単電池１０２ａにおいて水分量が過剰となり、これによってセル電圧Ｖ_１が低下したことを示している。
【０１６８】
そこで、この場合にはＳ３１に進み、前述とは逆に、空気流量ｆ_{ａｉｒｉｎ}（１）の増加及び／又は空気加湿量Ｗ_Ｃｉｎ（１）の減少、あるいは、燃料加湿量Ｗ_Ａｉｎ（１）の減少により、空気極側あるいは燃料極側から過剰水分を排除すればよい。さらに、これらの中から選ばれる１以上の制御パラメータを組み合わせ、単電池１０２ａの水収支の均衡が保たれるように、これらを同時に制御してもよい。
【０１６９】
Ｓ３０あるいはＳ３１において、空気流量ｆ_{ａｉｒｉｎ}（１）、空気加湿量Ｗ_Ｃｉｎ（１）及び燃料加湿量Ｗ_Ａｉｎ（１）から選ばれる少なくとも１以上が制御された後、Ｓ２１に戻る。そして、セル電圧Ｖ_１とセル電圧Ｖ_２が一致するまで、上述したＳ２１〜Ｓ２３、及びＳ２８〜Ｓ３１の各ステップが繰り返される。
【０１７０】
以上のように、図１６に示す積層型燃料電池の運転方法によれば、温度環境の異なる単電池グループ毎に検出された膜抵抗を用いて、反応ガスの流量及び加湿量を個別に制御しているので、各単電池のガス流路構造及び電極構造を同一とした場合であっても、電解質膜の含水率の不均一や、反応ガス供給量の相対的な過不足を抑制することができる。また、これによってセル電圧のばらつきを解消することができ、積層型燃料電池全体の出力を向上させることができる。
【０１７１】
次に、温度環境の異なる各単電池のセル電圧の差を小さくするための他の運転方法について説明する。図１７〜図１９に、制御フローチャートの一例を示す。初めに、図１７に示すＳ４１において、グループ１に属する単電池１０２ａのセル電圧Ｖ_１と、グループ２に属する単電池１０２ｂのセル電圧Ｖ_２が電池作動状況検出装置１１０により検出される。
【０１７２】
次いで、Ｓ４２において、セル電圧Ｖ_１とセル電圧Ｖ_２が等しいか否かが判断される。セル電圧Ｖ_１とセル電圧Ｖ_２が等しい場合（Ｓ４２：ＹＥＳ）には、Ｓ４１に戻り、セル電圧Ｖ_１とセル電圧Ｖ_２の変動が生じるまで上述のＳ４１〜Ｓ４２の各ステップが繰り返される。一方、セル電圧Ｖ_１とセル電圧Ｖ_２が等しくない場合（Ｓ４２：ＮＯ）には、各単電池の反応ガス供給量に相対的な過不足が発生したことを示しているので、Ｓ４３に進む。
【０１７３】
Ｓ４３では、セル電圧Ｖ_１がセル電圧Ｖ_２より大きいか否かが判断される。セル電圧Ｖ_１がセル電圧Ｖ_２より大きい場合（Ｓ４３：ＹＥＳ）には、図１８に示すＳ５１に進む。Ｓ５１では、セル電圧Ｖ_２の現在値をＶ_Ｐとして記憶させ、次いで、空気流量ｆ_{ａｉｒｉｎ}（２）を増加させる。そして、所定時間経過後、Ｓ５２において、セル電圧Ｖ_２を再度検出し、さらに、Ｓ５３において、記憶された現在値Ｖ_Ｐと新たに検出されたセル電圧Ｖ_２との対比が行われる。
【０１７４】
現在値Ｖ_Ｐがセル電圧Ｖ_２より小さい場合（Ｓ５３：ＹＥＳ）には、空気流量ｆ_{ａｉｒｉｎ}（２）が相対的に不足し、これによってセル電圧Ｖ_２が低下したことを示している。そこで、この場合にはＳ５４へ進み、セル電圧Ｖ_２の現在値をＶ_Ｐとして記憶させ、次いで、空気流量ｆ_{ａｉｒｉｎ}（２）を増加させる操作が実行される。所定時間経過後、Ｓ５５において、セル電圧Ｖ_２を再度検出し、Ｓ５６において、記憶された現在値Ｖ_Ｐと新たに検出されたセル電圧Ｖ_２との対比が行われる。
【０１７５】
そして、Ｓ５６において、現在値Ｖ_Ｐがセル電圧Ｖ_２より小さいと判断された場合（Ｓ５６：ＹＥＳ）には、単電池１０２ｂの空気流量ｆ_{ａｉｒｉｎ}（２）の相対的な不足が未だ解消されていないことを示しているので、Ｓ５４に戻り、上述したＳ５４〜Ｓ５６の各ステップが繰り返される。一方、現在値Ｖ_Ｐがセル電圧Ｖ_２より小さくない（Ｓ５６：ＮＯ）場合、すなわち、空気流量ｆ_{ａｉｒｉｎ}（２）を増加させてもセル電圧Ｖ_２がもはや増加しなくなった場合は、Ｓ４１へ戻る。
【０１７６】
これに対し、Ｓ５３において、現在値Ｖ_Ｐがセル電圧Ｖ_２より小さくないと判断された場合（Ｓ５３：ＮＯ）には、セル電圧Ｖ_２の低下が空気流量ｆ_{ａｉｒｉｎ}（２）の相対的な不足に起因するものではないことを示している。そこで、この場合にはＳ５７に進み、上述と同様の手順に従い、空気流量ｆ_{ａｉｒｉｎ}（２）を減少させることにより、セル電圧Ｖ_２が増加するか否かが判断される（Ｓ５７〜Ｓ５９）。
【０１７７】
記憶された現在値Ｖ_Ｐが新たに検出されたセル電圧Ｖ_２より小さい場合（Ｓ５９：ＹＥＳ）には、空気流量ｆ_{ａｉｒｉｎ}（２）が相対的に過剰となり、これによってセル電圧Ｖ_２が低下したことを示している。そこで、この場合にはＳ６０に進み、セル電圧Ｖ_２が増加しなくなるまで、空気流量ｆ_{ａｉｒｉｎ}（２）を減少さる（Ｓ６０〜Ｓ６２）。そして、空気流量ｆ_{ａｉｒｉｎ}（２）を増加させてもセル電圧Ｖ_２がもはや増加しなくなったところで（Ｓ６２：ＮＯ）、Ｓ４１へ戻る。
【０１７８】
また、Ｓ５９において、現在値Ｖ_Ｐがセル電圧Ｖ_２より小さくないと判断された場合（Ｓ５９：ＮＯ）には、セル電圧Ｖ_２の低下が空気流量の相対的な過不足に起因するものではないことを示している。そこで、この場合にはＳ６３へ進み、燃料流量ｆ_Ｈｉｎ（２）の増加によってセル電圧Ｖ_２が増加するか否かが判断される（Ｓ６３〜Ｓ６５）。
【０１７９】
燃料流量ｆ_Ｈｉｎ（２）の増加によってセル電圧Ｖ_２が増加した場合（Ｓ６５：ＹＥＳ）には、Ｓ６６へ進み、セル電圧Ｖ_２が増加しなくなるまで、燃料流量ｆ_Ｈｉｎ（２）を増加さる（Ｓ６６〜Ｓ６８）。そして、燃料流量ｆ_Ｈｉｎ（２）を増加させてもセル電圧Ｖ_２がもはや増加しなくなったところで（Ｓ６８：ＮＯ）、Ｓ４１へ戻る。
【０１８０】
一方、Ｓ６５において、燃料流量ｆ_Ｈｉｎ（２）の増加によってセル電圧Ｖ_２が増加しなかった場合（Ｓ６５：ＮＯ）は、Ｓ６９に進み、燃料流量ｆ_Ｈｉｎ（２）を減少させることにより、セル電圧Ｖ_２が増加するか否かが判断される（Ｓ６９〜Ｓ７１）。
【０１８１】
燃料流量ｆ_Ｈｉｎ（２）の減少によってセル電圧Ｖ_２が増加した場合（Ｓ７１：ＹＥＳ）には、Ｓ７２へ進み、セル電圧Ｖ_２が増加しなくなるまで、燃料流量ｆ_Ｈｉｎ（２）を減少さる（Ｓ７２〜Ｓ７４）。そして、燃料流量ｆ_Ｈｉｎ（２）を増加させてもセル電圧Ｖ_２がもはや増加しなくなったところで（Ｓ７１：ＮＯ、又はＳ７４：ＮＯ）、Ｓ４１へ戻る。
【０１８２】
同様に、Ｓ４３において、セル電圧Ｖ_１がセル電圧Ｖ_２より大きくないと判断された場合（Ｓ４３：ＮＯ）には、図１９に示すＳ８１に進む。そして、上述と同様の手順に従い、空気流量ｆ_{ａｉｒｉｎ}（１）の増加（Ｓ８１〜Ｓ８６）及び減少（Ｓ８７〜Ｓ９２）、並びに燃料流量ｆ_Ｈｉｎ（１）の増加（Ｓ９３〜Ｓ９８）及び減少（Ｓ９９〜Ｓ１０４）が順次、試行錯誤的に実行され、セル電圧Ｖ_１を低下させた原因が解消されるまで、反応ガス流量の個別制御が行われる。
【０１８３】
以上のように、図１７〜図１９に示す積層型燃料電池の運転方法によれば、温度環境の異なる単電池グループ毎に、反応ガスの流量を個別に制御しているので、各単電池のガス流路構造及び電極構造を同一とした場合であっても、反応ガス供給量の相対的な過不足に起因するセル電圧のばらつきを解消することができ、これによって、積層型燃料電池全体の出力を向上させることができる。
【０１８４】
また、図１７〜図１９に示す運転方法によれば、図１５及び図１６に示す運転方法と異なり、酸素濃度や水素濃度を検出するための装置、あるいは、電解質膜の膜抵抗を検出するための装置を用いることなく、セル電圧のばらつきを解消できるので、積層型燃料電池システムの低コスト化が図れるという利点がある。
【０１８５】
【実施例】
（実施例１）
図１に示す構造を有する積層型燃料電池４０を作製し、放電特性を調べた。すなわち、空気流路の溝の深さが異なる単電池を２個積層して単位モジュール４２とし、これを２５個積層して積層型燃料電池４０（単電池の積層数＝５０セル）とした。
【０１８６】
ここで、冷媒流路６０により直接冷却される低温空気極５０側の空気流路（以下、これを「冷却空気流路」という）５４ｃの溝の深さＤ_Ｃ１は０．６ｍｍとし、冷媒流路６０により直接冷却されない高温空気極７０側の空気流路（以下、これを「非冷却空気流路」という）５６ｃの溝の深さＤ_Ｃ２は０．３ｍｍとした。
【０１８７】
また、冷媒流路６０により直接冷却されない高温燃料極４８側の燃料流路（以下、これを「非冷却燃料流路」という）５６ａの溝の深さＤ_Ａ１、及び冷媒流路６０により直接冷却される低温燃料極６８側の燃料流路（以下、これを「冷却燃料流路」という）５８ａの溝の深さＤ_Ａ２は、いずれも０．５ｍｍとした。さらに、電極面積を２００ｃｍ^２とし、電解質膜４６、６６には、パーフルオロ系の固体高分子電解質膜を用いた。
【０１８８】
得られた積層型燃料電池４０の燃料極側には、露点９０℃の水蒸気を含む水素ガスを、圧力０．２ＭＰａ、水素利用率８０％相当の流量で供給した。また、空気極側には、露点８０℃の水蒸気を含む空気を、圧力０．２ＭＰａ、酸素利用率２０％相当の流量で供給した。さらに、１セルおきに設けられる冷媒流路６０には、水温８０℃の冷却水を供給した。次いで、この積層型燃料電池４０を、１．０Ａ／ｃｍ^２の電流密度一定の条件下で放電させ、各単電池のカソード温とセル電圧を測定した。
【０１８９】
（比較例１）
冷却空気流路５４ｃの溝の深さＤ_Ｃ１、及び非冷却空気流路５６ｃの溝の深さＤ_Ｃ２を、いずれも０．４５ｍｍとした以外は、実施例１と同一の構造を有する積層型燃料電池を作製し、実施例１と同一条件下で放電特性を調べた。
【０１９０】
実施例１及び比較例２で得られた結果を、それぞれ、図２０及び図２１に示す。冷却空気流路５４ｃの溝の深さＤ_Ｃ１及び非冷却空気流路５６ｃの溝の深さＤ_Ｃ２をいずれも０．４５ｍｍとした比較例１では、図２１に示すように、カソード温は、冷却空気流路５４ｃに隣接する低温空気極５０で８２℃、非冷却空気流路５６ｃに隣接する高温空気極７０で９８℃となり、冷媒流路６０からの距離に応じて、カソード温に１６℃の温度差が発生した。
【０１９１】
また、カソード温の低い単電池４４のセル電圧は０．６０Ｖであるのに対し、カソード温の高い単電池４５のセル電圧は０．４０Ｖに低下した。これは、カソード温の異なるすべての単電池に対し、露点８０℃の水蒸気を含むドライ気味の空気を均等に送り込んでいるために、単電池４５においてドライアップが生じたためである。
【０１９２】
これに対し、非冷却空気流路５６ｃの溝の深さＤ_Ｃ２を冷却空気流路５４ｃの溝の深さＤ_Ｃ１の半分とした実施例１では、図２０に示すように、温度分布は比較例１とほとんど違いがないが、カソード温の高い単電池４５のセル電圧が０．５８Ｖに向上し、その結果、積層型燃料電池全体の総電圧が向上した。これは、非冷却空気流路５６ｃの断面積が小さいために、非冷却空気流路５６ｃの空気流量が少なくなり、単電池４５のドライアップが抑制されたためである。
【０１９３】
（実施例２）
図２に示す構造を有する積層型燃料電池７４を作製し、放電特性を調べた。すなわち、非冷却空気流路５６ｃの入り口にガス流通の障害となる多孔体７８を設けて単位モジュール７６とし、これを２５個積層して積層型燃料電池７４（単電池の積層数＝５０セル）とした。
【０１９４】
なお、冷却空気流路５４ｃの溝の深さＤ_Ｃ１及び非冷却空気流路５６ｃの溝の深さＤ_Ｃ２は、いずれも０．４５ｍｍとした。また、単位モジュール７４の構造に関するその他の点については、実施例１と同一とした。得られた積層型燃料電池７４について、実施例１と同一条件下で放電特性を調べた。結果を図２２に示す。
【０１９５】
非冷却空気流路５６ｃに多孔体７８を設けた実施例２では、カソード温の分布は比較例１とほとんど違いがないが、セル電圧は、カソード温の低い単電池４４で０．６０Ｖ、カソード温の高い単電池４５で０．５８Ｖとなり、比較例１に比して、単電池４５のセル電圧が向上した。これは、多孔体７８により非冷却空気流路５６ｃの流路抵抗が高くなったために、非冷却空気流路５６ｃの空気流量が少なくなり、単電池４５のドライアップが抑制されたためである。
【０１９６】
（実施例３）
図３に示す構造を有する積層型燃料電池８０を作製し、放電特性を調べた。すなわち、非冷却空気流路５６ｃの入口にガス流通の障害となるような障害板８４を設けて単位モジュール８２とし、これを２５個積層して積層型燃料電池８０（単電池の積層数＝５０セル）とした。なお、単位モジュール８２の構造に関するその他の点については、実施例２と同一とした。
【０１９７】
得られた積層型燃料電池８０の燃料極側には、露点９０℃の水蒸気を含む水素ガスを、圧力０．２ＭＰａ、水素利用率８０％相当の流量で供給した。また、空気極側には、露点９０℃の水蒸気を含む空気を、圧力０．２ＭＰａ、酸素利用率２０％相当の流量で供給した。さらに、１セルおきに設けられる冷媒流路６０には、水温８０℃の冷却水を供給した。次いで、積層型燃料電池８０を、１．０Ａ／ｃｍ^２の電流密度一定の条件下で放電させ、各単電池のカソード温とセル電圧を測定した。
【０１９８】
（比較例２）
比較例１と同一の構造を有する積層型燃料電池を用い、実施例３と同一条件下で放電特性を調べた。
【０１９９】
実施例３及び比較例２で得られた結果を、それぞれ、図２３及び図２４に示す。空気流路の溝の深さを同一とし、露点９０℃の水蒸気を含むウェット気味の空気を空気流路に供給した比較例２では、図２４に示すように、カソード温は、低温空気極５０で８２℃、高温空気極７０で９８℃となった。
【０２００】
また、カソード温の高い単電池４５のセル電圧は０．６０Ｖであるのに対し、カソード温の低い単電池４４のセル電圧は０．２０Ｖまで低下した。これは、カソード温の異なるすべての単電池に対し、露点９０℃の水蒸気を含むウェット気味の空気を均等に送り込んでいるために、単電池４４においてフラッディングが生じたためである。
【０２０１】
これに対し、非冷却空気流路５６ｃに障害板８４を設けた実施例３では、図２３に示すように、カソード温の分布は比較例２とほとんど違いがないが、カソード温の低い単電池４４のセル電圧が０．５８Ｖまで向上した。これは、入り口側に設けられた障害板８４により、非冷却空気流路５６ｃの流路抵抗が高くなったために、冷却空気流路５４ｃの空気流量が多くなり、単電池４４のフラッディングが抑制されたためである。
【０２０２】
（実施例４）
図４に示す構造を有する積層型燃料電池８６を作製し、放電特性を調べた。すなわち、非冷却空気流路５６ｃの出口に突起５６ｄを設けると共に、冷却空気流路５４ｃの入口に突起５４ｄを設けて単位モジュール８８とし、これを２５個積層して積層型燃料電池８６（単電池の積層数＝５０セル）とした。なお、単位モジュール８８の構造に関するその他の点については、実施例２と同一とした。
【０２０３】
得られた積層型燃料電池８６の燃料極側には、露点９０℃の水蒸気を含む水素ガスを、圧力０．２ＭＰａ、水素利用率８０％相当の流量で供給した。また、空気極側には、露点９０℃の水蒸気を含む空気を、酸素利用率２０％相当の流量で供給した。さらに、１セルおきに設けられる冷媒流路６０には、水温８０℃の冷却水を供給した。次いで、この積層型燃料電池８６を、１．０Ａ／ｃｍ^２の電流密度一定の条件下で放電させ、各単電池のカソード温とセル電圧を測定した。結果を図２５に示す。
【０２０４】
空気極の出ガス圧力を０．１３ＭＰａに調整したところ、セル内空気圧力は、高温空気極７０側で０．２ＭＰａ、低温空気極５０側で０．１３ＭＰａとなった。これは、空気流路の出口及び入口に設けた突起５４ｄ、５６ｄ部分で約０．０７ＭＰａの圧力損失が生じたためである。また、低温空気極５０側のカソード温は８２℃、高温空気極７０側のカソード温は９８℃であり、温度分布は、比較例２とほぼ同様であった。
【０２０５】
しかしながら、セル電圧は、カソード温の高い単電池４５で０．５４Ｖ、カソード温の低い単電池４４で０．５２Ｖとなり、比較例２に比して、セル電圧のばらつきが小さくなり、積層型燃料電池８６全体の出力が向上した。これは、冷却空気流路５４ｃの内圧が比較例２に比して低いために、単電池４４でのフラッディングが抑制されたためである。
【０２０６】
（実施例５）
電極構造の異なる単電池が積層された積層型燃料電池を作製し、放電特性を調べた。すなわち、２個の単電池を積層して単位モジュールとし、これを２５個積層して積層型燃料電池（単電池の積層数＝５０セル）とした。また、高温空気極の拡散層の平均孔径は約０．１μｍとし、低温空気極の拡散層の平均孔径は約１μｍとした。
【０２０７】
なお、単位モジュールの構造に関するその他の点については、実施例２と同一とした。また、得られた積層型燃料電池について、実施例１と同一条件下で放電特性を調べた。
【０２０８】
（比較例３）
すべての空気極の拡散層の平均孔径を約１μｍとした以外は、実施例５と同一の構造を有する積層型燃料電池を作製し、実施例５と同一条件下で放電特性を調べた。
【０２０９】
実施例５及び比較例３で得られた結果を図２６及び図２７に示す。すべての空気極の拡散層の平均孔径を１μｍとした比較例３では、図２７に示すように、カソード温は、冷却空気極５４ｃ側で８２℃、非冷却空気極５６ｃ側で９８℃であった。また、セル電圧は、カソード温の低い単電池で０．６０Ｖ、カソード温の高い単電池で０．４０Ｖとなった。これは、拡散層の平均孔径が等しい空気極に対し、露点８０℃の水蒸気を含む空気を均等に配流したために、カソード温の高い単電池においてドライアップが生じたためである。
【０２１０】
これに対し、高温空気極の拡散層の平均孔径を０．１μｍとした実施例５では、図２６に示すように、カソード温の分布は比較例３と同等であったが、カソード温の高い単電池のセル電圧が０．５２Ｖまで向上した。これは、高温空気極の拡散層の平均孔径を小さくしたために、電解質膜からの水の持ち出しが少なくなり、ドライアップが抑制されたためである。
【０２１１】
（実施例６）
図５に示す構造を有する積層型燃料電池９０を作製し、放電特性を調べた。すなわち、燃料流路の溝の深さが異なる単電池を２個積層して単位モジュール９２とし、これを２５個積層して積層型燃料電池９０（単電池の積層数＝５０セル）とした。
【０２１２】
ここで、冷却燃料流路５８ａの溝の深さＤ_Ａ２は０．５ｍｍとし、非冷却燃料流路５６ａの溝の深さＤ_Ａ１は０．４ｍｍとした。また、冷却空気流路５４ａの溝の深さＤ_Ｃ１及び非冷却空気流路５６ｃの溝の深さＤ_Ｃ２は、いずれも０．５ｍｍとした。さらに、電極面積を２００ｃｍ^２とし、電解質膜４６、６６には、パーフルオロ系の固体高分子電解質膜を用いた。
【０２１３】
得られた積層型燃料電池９０の燃料極側には、露点８５℃の水蒸気を含む水素ガスを、圧力０．２ＭＰａ、水素利用率８０％相当の流量で供給した。また、空気極側には、露点８５℃の水蒸気を含む空気を、圧力０．２ＭＰａ、酸素利用率２０％相当の流量で供給した。さらに、１セルおきに設けられる冷媒流路６０には、水温８０℃の冷却水を供給した。次いで、この積層型燃料電池９０を、１．０Ａ／ｃｍ^２の電流密度一定の条件下で放電させ、アノード温及びセル電圧を測定した。
【０２１４】
（比較例４）
非冷却燃料流路５６ａの溝の深さＤ_Ａ１、及び冷却燃料流路５８ａの溝の深さＤ_Ａ２を、いずれも０．４５ｍｍとした以外は、実施例６と同一の構造を有する積層型燃料電池を作製し、実施例６と同一の条件下で、放電特性を調べた。
【０２１５】
実施例６及び比較例４で得られた結果を、それぞれ図２８及び図２９に示す。燃料流路の溝の深さを同一とし、露点８５℃の水蒸気を含む水素ガスを各燃料流路に均等に配流した比較例４では、図２９に示すように、アノード温は、低温燃料極６８側で８１℃、高温燃料極４８側で９５℃となった。また、セル電圧は、アノード温の低い単電池４５で０．６２Ｖ、アノード温の高い単電池４４で０．４０Ｖとなった。これは、アノード温の異なるすべての燃料極に対し、露点８５℃の水蒸気を含む水素ガスを均等に配流しているために、単電池４４においてドライアップが生じたためである。
【０２１６】
これに対し、非冷却燃料流路５６ａの溝の深さＤ_Ａ１を大きくした実施例６では、図２８に示すように、温度分布は比較例４とほとんど違いがないが、アノード温の高い単電池４４のセル電圧が０．５５Ｖまで向上した。これは、非冷却燃料流路５６ａの断面積が大きいために、高温燃料極４８側の燃料流量が多くなり、単電池４４のドライアップが抑制されたためである。
【０２１７】
（実施例７）
図６に示す構造を有する積層型燃料電池９４を作製し、放電特性を調べた。すなわち、非冷却燃料流路５６ａの出口に突起５６ｆを設けると共に、冷却燃料流路５８ａの入口に突起５８ｆを設けて単位モジュール９６とし、これを２５個積層して積層型燃料電池９４（単電池の積層数＝５０セル）とした。
【０２１８】
なお、非冷却燃料流路５６ａの溝の深さＤ_Ａ１、及び、冷却燃料流路５８ａの溝の深さＤ_Ａ２は、いずれも０．４５ｍｍとし、単位モジュール９６の構造に関するその他の点については、実施例６と同一とした。
【０２１９】
得られた積層型燃料電池９４の燃料極側には、露点９０℃の水蒸気を含む水素ガスを、水素利用率８０％相当の流量で供給した。また、空気極側には、露点８０℃の水蒸気を含む空気を、圧力０．２ＭＰａ、酸素利用率２０％相当の流量で供給した。さらに、１セルおきに設けられる冷媒流路には、水温８０℃の冷却水を供給した。次いで、この積層型燃料電池９４を、１．０Ａ／ｃｍ^２の電流密度一定の条件下で放電させ、アノード温及びセル電圧を測定した。結果を図３０に示す。
【０２２０】
燃料極出ガス圧力を０．２０ＭＰａに調整したところ、セル内燃料ガス圧力が、高温燃料極４８側で０．２５ＭＰａ、低温燃料極６８側で０．２ＭＰａとなった。これは、燃料流路の出口及び入口に設けた突起５６ｆ及び５８ｆ部分で、約０．０５ＭＰａの圧力損失が生じたためである。また、低温燃料極６８側のカソード温は８１℃、高温燃料極４８側のカソード温は９５℃であり、温度分布は、比較例４とほぼ同様であった。
【０２２１】
しかしながら、セル電圧は、アノード温の低い単電池４５で０．６２Ｖ、アノード温の高い単電池４４で０．５８Ｖとなり、比較例４に比して、アノード温の高い単電池４４のセル電圧が向上した。これは、非冷却燃料流路５６ａの内圧が増加したために、電解質膜からの水の持ち出しが少なくなり、単電池４４におけるドライアップが抑制されたためである。
【０２２２】
以上の結果から、単電池を数セル積層する毎に冷媒流路を設けた積層型燃料電池において、各単電池の温度環境に応じて、ガス流路構造又は電極構造を変化させれば、１つの反応ガス供給系統を用いて、燃料ガス及び空気を分配する場合であっても、電解質膜のドライアップ又はフラッディングに起因するセル電圧の低下が抑制され、積層型燃料電池の総電圧が向上することがわかった。
【０２２３】
以上、本発明の実施の形態について詳細に説明したが、本発明は上記実施の形態に何ら限定されるものではなく、本発明の要旨を逸脱しないで種々の改変が可能である。
【０２２４】
例えば、上記実施例においては、空気極側又は燃料極側のいずれか一方のガス流路構造又は電極構造を、温度環境に合わせて変化させているが、上述した各種実施例を相互に組み合わせ、空気極側及び燃料極側の双方のガス流路構造及び電極構造を、温度環境に合わせて変化させても良い。
【０２２５】
また、本発明に係る燃料電池システムにおいては、温度環境の異なる単電池グループ毎に、反応ガスの流量、圧力、及び加湿量を個別に制御するので、各単電池のガス流路構造及び電極構造は同一であってもよいが、温度環境に合わせてガス流路構造及び／又は電極構造を変化させた積層型燃料電池を用いても良い。
【０２２６】
このような積層型燃料電池を本発明に係る燃料電池システムに組み込めば、加湿量制御装置１０６及び反応ガス供給制御装置１０８における負荷が軽減されるので、反応ガスの流量等の制御をさらに容易化することができる。
【０２２７】
さらに、上記実施の形態において説明した燃料電池システムでは、単電池を２個積層する毎に冷却手段を設けた積層型燃料電池が用いられているが、３個以上の単電池を積層する毎に冷却手段を設けた積層型燃料電池を用いても良い。
【０２２８】
この場合、燃料電池システムに、燃料加湿量制御装置、空気加湿量制御装置、燃料ガス供給制御装置及び空気供給制御装置を、それぞれ３個以上設けるようにすれば、温度環境の異なる単電池グループ毎に、反応ガスの流量、圧力及び加湿量を最適化することが可能となり、これにより上記実施の形態と同様の効果を得ることができる。
【０２２９】
【発明の効果】
本発明に係る積層型燃料電池の運転方法は、各単電池へ供給される及び／又は各単電池から排出される反応ガスの流量、圧力及び／又は加湿量を単電池毎に変化させているので、単電池の積層方向に向かって温度分布が生じた場合であっても、ドライアップ又はフラッディングに起因するセル電圧のばらつきを小さくすることができるという効果がある。また、これにより、積層型燃料電池全体の出力が向上するという効果がある。
【０２３０】
また、本発明に係る積層型燃料電池は、各単電池に供給される水分量と、各単電池から排出される水分量が単電池毎に均衡するように、各単電池のガス流路構造及び／又は電極構造を変化させているので、１つの燃料マニホールド及び空気マニホールドを介して、各単電池に燃料ガス及び空気を配流する場合であっても、各単電池毎にガス流量、圧力、あるいは、単電池から排出される水蒸気量を個別に制御することができるという効果がある。
【０２３１】
また、これによって、ドライアップ又はフラッディングに起因するセル電圧のばらつきを小さくすることができ、積層型燃料電池全体の出力が向上するという効果がある。しかも、冷却手段の数を増加させることなく積層型燃料電池のエネルギー効率を向上させることができるので、単位体積当たりの出力を低下させることもない。
【０２３２】
また、本発明に係る燃料電池システムは、積層型燃料電池に備えられる単電池又は単電池グループ毎に作動状況を個別に検出する検出手段と、検出手段により検出された作動状況に基づき、各単電池又は各単電池グループに供給される反応ガスの流量、圧力又は加湿量を個別に制御する制御手段とを備えているので、単電池の積層方向に向かって温度分布が発生した場合であっても、各単電池の電解質膜の水収支の不均一や、反応ガス流量の相対的な過不足を解消することができる。
【０２３３】
そのため、各単電池のセル電圧のばらつきを小さくすることができ、燃料電池システム全体の出力が向上するという効果がある。しかも、冷却手段の数を増加させることなく燃料電池システムのエネルギー効率を向上させることができるので、単位体積当たりの出力を低下させることもない。
【０２３４】
以上のように、本発明によれば、燃料電池の高出力化及び高エネルギー効率化を図ることができる同時に、燃料電池のコンパクト化を図ることができるので、これを例えば車載用の燃料電池システムに応用すれば、自動車の高出力化、軽量化等に寄与するものであり、産業上その効果の極めて大きい発明である。
【図面の簡単な説明】
【図１】図１（ａ）は、本発明の第１の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向から見た断面図であり、図１（ｂ）は、そのＡ−Ａ’線断面図である。
【図２】本発明の第２の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向と垂直な方向から見た断面図である。
【図３】本発明の第３の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向と垂直な方向から見た断面図である。
【図４】本発明の第４の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向と垂直な方向から見た断面図である。
【図５】本発明の第６の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向と垂直な方向から見た断面図である。
【図６】本発明の第７の実施の形態に係る積層型燃料電池の基本構造となる単位モジュールのガス流方向と垂直な方向から見た断面図である。
【図７】単電池内の水の流れを説明する図である。
【図８】図８（ａ）は、単電池を２セル積層する毎に冷媒流路を設けた従来一般に用いられる積層型燃料電池に発生する積層方向の温度分布を示す図であり、図８（ｂ）は、単電池を２セル積層する毎に冷媒流路を設けた積層型燃料電池のガス流方向から見た断面図である。
【図９】図９（ａ）は、図８（ｂ）に示す構造を有する積層型燃料電池を電流密度０．２Ａ／ｃｍ^２の条件下で放電させたときのアノード温、カソード温及びセル電圧を示す図であり、図９（ｂ）は、電流密度１．０Ａ／ｃｍ^２の条件下で放電させたときのアノード温、カソード温及びセル電圧を示す図である。
【図１０】図１０（ａ）は、単電池を３セル積層する毎に冷媒流路を設けた従来一般に用いられる積層型燃料電池に発生する積層方向の温度分布を示す図であり、図１０（ｂ）は、単電池を３セル積層する毎に冷媒流路を設けた積層型燃料電池のガス流方向から見た断面図である。
【図１１】図１０（ｂ）に示す構造を有する積層型燃料電池を電流密度１．０Ａ／ｃｍ^２の条件下で放電させたときのアノード温、カソード温及びセル電圧を示す図である。
【図１２】本発明に係る燃料電池システムを示すブロック構成図である。
【図１３】図１２に示す燃料電池システムに用いられる積層型燃料電池の一例を示す概略構成図である。
【図１４】図１２に示す燃料電池システムに用いられる積層型燃料電池の一例を示す斜視図である。
【図１５】図１２に示す燃料電池システムの運転方法の一例を示すフローチャートである。
【図１６】同じく、図１２に示す燃料電池システムの運転方法の他の一例を示すフローチャートである。
【図１７】同じく、図１２に示す燃料電池システムの運転方法の他の一例を示すフローチャートである。
【図１８】図１７に示すフローチャートの続きである。
【図１９】同じく、図１７に示すフローチャートの続きである。
【図２０】空気流路の断面積が異なる単電池が積層された積層型燃料電池（実施例１）のカソード温とセル電圧の関係を示す図である。
【図２１】空気流路の断面積が等しい単電池が積層された積層型燃料電池にドライ気味の空気を供給した場合（比較例１）のカソード温とセル電圧の関係を示す図である。
【図２２】非冷却空気流路の入口に多孔体を設けた積層型燃料電池（実施例２）のカソード温とセル電圧の関係を示す図である。
【図２３】非冷却空気流路の入口に障害板を設けた積層型燃料電池（実施例３）のカソード温とセル電圧の関係を示す図である。
【図２４】空気流路の断面積が等しい単電池が積層された積層型燃料電池にウェット気味の空気を供給した場合（比較例２）のカソード温とセル電圧の関係を示す図である。
【図２５】非冷却空気流路の出口及び冷却空気流路の入口に突起を設けた積層型燃料電池（実施例４）のカソード温とセル電圧の関係を示す図である。
【図２６】空気極の拡散層の平均孔径が異なる単電池が積層された積層型燃料電池（実施例５）のカソード温とセル電圧の関係を示す図である。
【図２７】空気極の拡散層の平均孔径が等しい単電池が積層された積層型燃料電池（比較例３）のカソード温とセル電圧の関係を示す図である。
【図２８】燃料流路の異なる単電池が積層された積層型燃料電池（実施例６）のカソード温とセル電圧の関係を示す図である。
【図２９】燃料流路の等しい単電池が積層された積層型燃料電池にドライ気味の燃料ガスを供給した場合（比較例４）のカソード温とセル電圧の関係を示す図である。
【図３０】非冷却燃料流路の入口及び冷却燃料流路の出口に突起を設けた積層型燃料電池（実施例７）のカソード温とセル電圧の関係を示す図である。
【図３１】燃料電池の基本構造となる単電池を示す分解斜視図である。
【図３２】従来一般に用いられる積層型燃料電池を示す斜視図である。
【符号の説明】
４０、７４、８０、８６、９０、９４ 積層型燃料電池
４２、７６、８２、８８、９２、９６ 単位モジュール
４４、４５ 単電池
５４ｃ 空気流路（冷却空気流路）
５４ｄ 突起
５６ｃ 空気流路（非冷却空気流路）
５６ｄ、５６ｆ 突起
５６ａ 燃料流路（非冷却燃料流路）
５８ａ 燃料流路（冷却燃料流路）
５８ｆ 突起
６０ 冷媒流路
７８ 多孔体
８４ 障害板
１００ 燃料電池システム
１０２ 積層型燃料電池
１０４ 反応ガス供給装置
１０６ 加湿量制御装置
１０８ 反応ガス供給制御装置
１１０ 電池作動状況検出装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of operating a stacked fuel cell, a stacked fuel cell, and a stacked fuel cell system, and more particularly, to a method of operating a stacked fuel cell suitable as a vehicle-mounted power source, a stationary small generator, and the like, And a stacked fuel cell system.
[0002]
[Prior art]
A fuel cell is a battery that continuously supplies fuel and discharges combustion products and directly converts the chemical energy of the fuel into electric energy.It has high power generation efficiency and low emission of air pollutants. It has features such as low noise, free choice of scale, and so on.
[0003]
Fuel cells are classified into polymer electrolyte type, phosphoric acid type, alkali type, molten carbonate type, solid oxide type, and the like, depending on the type of electrolyte membrane used. In particular, polymer electrolyte fuel cells using a solid polymer electrolyte as the electrolyte membrane have low operating temperatures and high power densities, and are expected to be applied to in-vehicle power sources and stationary small generators in recent years. Is what is being done.
[0004]
FIG. 31 shows an example of the basic structure of a polymer electrolyte fuel cell. In FIG. 31, a unit cell 2 serving as a power generation unit of a polymer electrolyte fuel cell has an electrode / electrolyte assembly 10 in which a pair of gas diffusion electrodes 14 and 16 are joined to both surfaces of an electrolyte membrane 12 by separators 18 and 18. It has a sandwiched structure.
[0005]
As the electrolyte membrane 12, a fluorine-based electrolyte membrane represented by a perfluorosulfonic acid membrane known under the trade name of Nafion (registered trademark, manufactured by DuPont) is generally used.
[0006]
The gas diffusion electrodes 14 and 16 are composed of a catalyst layer (not shown) containing an electrode catalyst such as platinum and a diffusion layer (not shown) made of a porous material through which gas can diffuse. .
[0007]
Further, the separators 18 are generally made of dense graphite which has high current collecting performance and is stable even in an oxidized steam atmosphere. Further, the separators 18 are provided with a gas passage 18 b for supplying a substance such as a reaction gas or water to the electrolyte membrane 12.
[0008]
A fuel gas containing hydrogen, such as a reformed gas, flows to one gas diffusion electrode 14 (fuel electrode) side of the unit cell 2 having such a structure, and air or the like flows to the other gas diffusion electrode 16 (air electrode) side. When an oxidizing gas containing oxygen flows, an electrode reaction proceeds, and a change in free energy at that time can be directly extracted as electric energy.
[0009]
However, the electromotive force of the cell 2 shown in FIG. 31 is around 1 V, and cannot be put to practical use as it is. Therefore, in order to obtain a high output, usually, several hundred cells are stacked in series, and a fuel cell is installed in a container with a device for collectively entering and exiting fuel, air, and cooling water attached thereto. (Hereinafter referred to as a “stacked fuel cell”).
[0010]
FIG. 32 shows an example of the structure of a stacked fuel cell. 32, in the stacked fuel cell 20, a cooling plate 22 for maintaining each unit cell 2 at an optimum temperature is disposed every time a plurality of unit cells 2 shown in FIG. 31 are stacked, and the stacked unit cells are further stacked. The upper and lower sides of the battery 2 are fastened by fastening plates 24, 24.
[0011]
In this case, the stacked unit cells 2 generally have the same gas flow path structure and electrode structure. A pair of fuel manifolds 34, 34 and a pair of air manifolds 36, 36 are provided on the side surface of the stacked fuel cell 20, and the fuel gas and the air having the same flow rate and the same pressure are distributed to each unit cell 2. It has become.
[0012]
Furthermore, in the polymer electrolyte fuel cell, in order for the electrolyte membrane 12 to function normally, it is necessary to appropriately manage the water content of the electrolyte membrane 12. For this reason, the reaction gas is humidified by using a humidifier (not shown), and the humidification amount is adjusted according to the battery temperature and the current density so that the amount of moisture in the unit cell 2 does not become excessive or insufficient. This is the same in phosphoric acid type fuel cells, alkaline type fuel cells, and the like. In order to allow the electrolyte membrane to function normally, the reaction gas is appropriately humidified.
[0013]
[Problems to be solved by the invention]
However, when the cooling plate 22 is disposed every time several cells are stacked, the cooling efficiency of the unit cell 2 decreases as the distance from the cooling plate 22 increases. As a result, a temperature difference occurs between a gas diffusion electrode (hereinafter simply referred to as an “electrode”) located far from the cooling plate 22 and an electrode located near the cooling plate 22. Moreover, the temperature difference tends to increase as the output of the stacked fuel cell 20 increases.
[0014]
On the other hand, with respect to the cells 2 having the same gas flow path structure and electrode structure, the flow rate, pressure, and humidification amount are equal via a pair of fuel electrode manifolds 34, 34 and a pair of air manifolds 36, 36. In the conventional stacked fuel cell 20 that supplies the reaction gas, the optimum humidification amount and gas flow rate cannot be set for all the cells 2 having different temperature environments.
[0015]
Therefore, in a fuel cell that requires water management of the electrolyte membrane, when the humidification conditions of the reaction gas are adjusted to the low-temperature cell 2, the dry-up in which the water content of the electrolyte membrane decreases in the high-temperature cell 2. Occurs and the cell voltage drops. Further, when the humidification condition of the reaction gas is adjusted to the high-temperature cell 2, the drainage capacity of the low-temperature cell 2 decreases, and the cell voltage decreases due to flooding. As a result, there is a problem that the energy efficiency of the entire stacked fuel cell is reduced.
[0016]
In order to solve this problem, it is considered effective to provide a cooling plate 22 between all the cells 2 and cool each cell 2 uniformly. However, providing the cooling plates 22 between all the cells 2 has a problem that the volume of the stacked fuel cell is increased and the output per unit volume is reduced.
[0017]
Furthermore, when the humidification condition is adjusted to the high-temperature cell 2, the drainage capacity of the low-temperature cell 2 is reduced, and liquid water may stay in the gas flow path. In the gas flow path in which the liquid water stays (in this case, the low-temperature unit cell 2), the gas flow resistance increases, and the gas inflow rate decreases relatively. In the fuel cells stacked in series, the reaction amount (= current value or consumed gas amount) in each unit cell 2 is constant. Therefore, in a cell in which the gas inflow amount is small, the voltage drop due to the shortage of gas amount is caused. As a result, there is a problem in that the energy efficiency of the entire stacked fuel cell is reduced.
[0018]
The problem to be solved by the present invention is to suppress the variation in cell voltage due to the temperature difference of each cell without lowering the output per unit volume in a fuel cell in which the water content of the electrolyte membrane needs to be controlled. It is an object of the present invention to provide a stacked fuel cell operating method, a stacked fuel cell, and a stacked fuel cell system which can achieve high energy efficiency.
[0019]
[Means for Solving the Problems]
To solve the above problems, the present inventionFor operating stacked fuel cell according to the inventionIs a unit cell in which an air electrode is joined to one side of the electrolyte, and a fuel electrode is joined to the other side, and this is sandwiched between separators with gas channels.SeveralStackedA stacked fuel cell including a unit module and cooling means disposed between the unit modules, wherein the amount of water supplied to each of the unit cells and the amount of water discharged from each of the unit cells are different. A reaction gas having the same flow rate, pressure and humidification amount is supplied to a unit having a different gas flow path structure and / or electrode structure for each unit cell so as to balance each unit cell. Distribute gas to each cellThe gist is that.
[0020]
According to the operation method of the stacked fuel cell according to the present invention having the above-described configuration, gases having different flow rates, pressures, and / or humidification amounts are supplied and / or exhausted for each of the stacked unit cells. The amount of supplied water can be increased or the amount of discharged water can be reduced only for the unit cells whose amount is insufficient. Similarly, it is also possible to reduce the amount of supplied water or increase the amount of discharged water only for a single cell having an excessive amount of water. Therefore, even when the temperature distribution is generated in the stacking direction of the unit cells, the variation in the cell voltage is reduced, and the energy efficiency of the entire stacked fuel cell is improved.
[0021]
In addition, the present inventionStacked fuel cell according to the present inventionIs a unit cell in which an air electrode is joined to one side of the electrolyte, and a fuel electrode is joined to the other side, and this is sandwiched between separators with gas channels.SeveralStackedA unit module, and cooling means arranged between the unit modules, wherein each of the cells isEach cellToThe amount of water supplied and the amount of water discharged from each cellAnd each of the aboveEach cell is balanced so that each cell is balanced.Different for eachGas flow path structure and / or electrode structureHaveThe gist is that.
[0022]
In this case, it is desirable that the gas flow channel structure and / or the electrode structure reduce the amount of air flowing into the high-temperature cell. Further, the gas flow path structure and / or the electrode structure may increase the amount of fuel gas flowing into the high-temperature unit cell. Alternatively, the gas flow path structure and / or the electrode structure may increase the internal pressure of the flow path of the high-temperature unit cell.
[0023]
Also,A cell in which the air electrode is joined to one side of the disintegration and the fuel electrode is joined to the other side, and this is sandwiched between separators equipped with gas channelsSeveralStackedA unit module, and cooling means disposed between the unit modules.In the stacked fuel cell, the gas flow channel structure and / or the electrode structure of each of the unit cells is changed so as to reduce the amount of water discharged from the high-temperature unit cells and / or to increase the amount of water discharged from the low-temperature unit cells. ChangeMay be.
[0024]
In this case, it is desirable that the air permeability of the air electrode diffusion layer included in the air electrode of the high-temperature cell be smaller than the air permeability of the air electrode diffusion layer included in the air electrode of another cell.
[0025]
According to the stacked fuel cell according to the present invention having the above-described configuration, the gas flow channel structure and / or the electrode structure of each unit cell is different depending on the temperature distribution in the stacking direction. Even when the reaction gas is distributed to each cell using the method, the flow rate and / or pressure of the reaction gas supplied to the electrode of each cell, or the amount of water supplied / discharged to each cell is It can be increased or decreased individually.
[0026]
Therefore, if the gas flow path structure and / or the electrode structure are appropriately designed for each cell or each cell group having a different temperature environment, even when a temperature distribution occurs in the cell stacking direction. In addition, the amount of water supplied to each unit cell and the amount of water discharged from each unit cell can be balanced for each unit cell. In other words, it is possible to reduce the amount of water discharged from the high-temperature cells and increase the amount of water discharged from the low-temperature cells.
[0027]
As a result, the variation in cell voltage of each unit cell is reduced, and the energy efficiency of the entire stacked fuel cell can be improved. Moreover, since the energy efficiency of the stacked fuel cell can be improved without increasing the number of cooling means, the output per unit volume does not decrease.
[0028]
Further, the fuel cell system according to the present invention is a unit cell in which electrodes are joined to both sides of an electrolyte membrane, and this is sandwiched between separators having gas channels.SeveralStackedA unit module, and cooling means disposed between the unit modules.A stacked fuel cell, and detection means for detecting an operation state of each of the unit cells or the groups of the unit cells,A reaction gas supply unit that supplies a reaction gas having a different flow rate, pressure, and / or humidification amount for each of the single cells or the group of single cells;Control means for individually controlling a flow rate, a pressure and / or a humidification amount of a reaction gas supplied to each of the cells or a group of the cells based on the operation state detected by the detection means. The gist is that.
[0029]
According to the fuel cell system of the present invention having the above-described configuration, the operating status of each of the stacked unit cells or each of the unit cell groups is individually detected by the detecting unit, and based on the detected operating status, the control unit The reaction gas whose flow rate, pressure or humidification amount is individually controlled is distributed to each unit cell or each unit cell group.
[0030]
Therefore, if the flow rate, pressure, or humidification amount of the reaction gas supplied to each cell or each cell group is appropriately controlled, even if a temperature distribution occurs in the stacking direction of the cells, It is possible to eliminate uneven water balance of the electrolyte membrane of the unit cell and relative excess and deficiency of the reaction gas. As a result, the variation in cell voltage of each unit cell is reduced, and the energy efficiency of the entire fuel cell system can be improved. Moreover, since the energy efficiency of the fuel cell system can be improved without increasing the number of cooling means, the output per unit volume does not decrease.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The stacked fuel cell according to the present invention includes a unit module in which a plurality of unit cells are stacked, and cooling means provided for each unit module. FIG. 1 shows a cross-sectional view of a unit module 42 which is a basic structure of a stacked fuel cell 40 according to a first embodiment of the present invention.
[0032]
In FIG. 1A, the unit module 42 has a structure in which two unit cells, that is, a unit cell 44 and a unit cell 45 are stacked. The cell 44 includes an electrode / electrolyte membrane assembly (hereinafter, simply referred to as a “assembly”) 52 in which a fuel electrode 48 and an air electrode 50 are joined on both sides of an electrolyte membrane 46, respectively, and the assembly 52 from both sides. It consists of a separator 54 and a separator 56 for sandwiching.
[0033]
Further, the unit cell 45 includes a joined body 72 in which a fuel electrode 68 and an air electrode 70 are joined to both surfaces of an electrolyte membrane 66, and a separator 56 and a separator 58 which sandwich the joined body 72 from both sides, respectively. Reference numeral 44 denotes a structure in which the separator 56 is shared.
[0034]
On one surface of the separator 54, a gas flow path (hereinafter referred to as “air flow path”) 54c for supplying air to the air electrode 50 of the joined body 52 is provided. In addition, a groove-shaped refrigerant flow path 60 is provided on the other surface of the separator 54 so that a refrigerant such as water or an inert gas can flow into a cavity formed when the unit modules 42 are stacked. ing.
[0035]
On one surface of the separator 56, a gas flow path (hereinafter, referred to as “fuel flow path”) 56a for supplying a fuel gas to the joined body 52 is provided. On the other surface of the separator 56, an air flow path 56c for supplying air to the joined body 72 is provided. Further, the separator 58 is provided with a fuel flow path 58a for supplying a fuel gas to the joined body 72.
[0036]
Here, as shown in FIG. 1B, the depth D of the groove of the air flow path 56c is set._C2Is the depth D of the groove of the air passage 54c._C1It is smaller, and the cross-sectional area of the air passage 56c is smaller. This is different from the conventional stacked fuel cell in which the structure of the air flow passage of each stacked unit cell is all the same.
[0037]
In the case of the present embodiment, the depth D of the groove of the fuel flow path 56a_A1Is the depth D of the groove of the fuel passage 58a._A2Is the same as The electrode structures of the fuel electrode 68 and the air electrode 70 of the assembly 72 are the same as the electrode structures of the fuel electrode 48 and the air electrode 50 of the assembly 52, respectively.
[0038]
Then, the unit modules 42 having such a structure are stacked, and a pair of air manifolds and a pair of fuel manifolds for supplying air and fuel gas to the cells 44 and 45, respectively (both are shown in the drawing). ) Is a stacked fuel cell 40.
[0039]
The present invention is applied to a fuel cell in which the water content of the electrolyte membranes 46 and 66 needs to be controlled. Specifically, a solid polymer electrolyte, a solid polymer fuel cell using a concentrated phosphoric acid or an alkaline solution, a phosphoric acid fuel cell, or an alkaline fuel cell is preferably used as the electrolyte membranes 46 and 66.
[0040]
In particular, when the present invention is applied to a polymer electrolyte fuel cell, a decrease in output due to dry-up or flooding of the electrolyte membranes 46 and 66 is reduced without reducing the output per unit volume. Therefore, there is an advantage that a stacked fuel cell suitable for a vehicle-mounted power source can be obtained.
[0041]
Further, the unit module 42 illustrated in FIG. 1 employs a so-called counter flow method in which the reaction gas flows in the opposite direction, but the flow of the reaction gas is not limited to this. For example, a co-flow method in which reaction gases flow in the same direction, or a cross-flow method in which reaction gases flow in a perpendicular direction may be used.
[0042]
Further, the cooling means is not limited to the structure illustrated in FIG. For example, a flat cooling plate having a coolant flow path therein may be provided adjacent to the unit module 42. Alternatively, separators 54 arranged at both ends of the unit module 42,58A coolant flow path may be provided in the inside to cool the separator directly.
[0043]
Next, the operation of the stacked fuel cell 40 according to the first embodiment of the present invention will be described. FIG. 7 schematically shows the flow of water in the cell 44 (45). The balance of water in the cell 44 (45) is performed in the following manner.
[0044]
That is, as shown in FIG. 7, when the humidified fuel gas is supplied to the fuel electrode 48 (68), water is supplied from the fuel gas to the fuel electrode 48 (68). The water supplied to the fuel electrode 48 (68) moves to the air electrode 50 (70) through the electrolyte membrane 46 (66) together with hydrogen ions by electroosmosis.
[0045]
On the other hand, on the air electrode 50 (70) side, water is generated by an electrode reaction. Part of the water generated by the electrode reaction and the water that has moved from the fuel electrode 48 (68) side to the air electrode 50 (70) side by electroosmosis moves to the fuel electrode 48 (68) side by diffusion, Another part is discharged out of the fuel cell from the cathode 50 (70) side. Therefore, it is important that these balances are balanced in order to maintain stable power generation characteristics.
[0046]
Here, it is assumed that the supply of water to the cells 44 and 45 and the discharge of water from the cells 44 and 45 are all performed in the form of steam, and together with the outgoing gas flows from the cathodes 50 and 70. The maximum amount of water that can be discharged as water vapor (hereinafter referred to as “maximum drainage”) is W_Cout-MAXIn other words, W_Cout-MAXCan be expressed by the following equation (1).
[0047]
(Equation 1)

[0048]
The amount of water brought into the cathodes 50 and 70 (hereinafter referred to as “total water supply amount”) is W_Cin-totalIn other words, W_Cin-totalCan be expressed by the following equation (2).
[0049]
(Equation 2)

[0050]
Here, the maximum drainage amount W on the air electrode 50, 70 side_Cout-MAXIs the total water supply W_Cin-totalIf the amount is less, the moisture in the atmosphere becomes excessive. As a result, “flooding” occurs in which excess water closes the pores of the air electrodes 50 and 70 and hinders gas supply, and the cell voltage decreases. Conversely, the maximum drainage amount W on the air electrode 50, 70 side_Cout-MAXIs the total water supply W_Cin-totalIf more, the atmosphere is dry. Therefore, “dry-up” occurs in which the water content of the electrolyte membranes 46 and 66 decreases and the membrane resistance increases, and the cell voltage decreases.
[0051]
Therefore, in order to maintain stable power generation performance, it is important to balance these balances and properly maintain the water content of the electrolyte membranes 46 and 66 on the cathodes 50 and 70 side.
[0052]
By the way, the saturated steam pressure p in the equation (1)_Wc-satIs a parameter determined only by the temperature on the air electrode side, and tends to increase as the temperature increases. Therefore, even when the structure of all the cells is the same and the same flow rate of the reaction gas is supplied to all the cells, when the temperature of each cell is uniform, the saturated steam pressure p_Wc-satIs the same for all the cells, so that the water balance is balanced for all the cells, and there is no variation in the cell voltage.
[0053]
However, for example, as shown in FIG. 8 (b), a solid polymer electrolyte membrane is used as the electrolyte membrane 12, and every time two unit cells 2 having the same gas flow path structure and electrode structure are stacked, the refrigerant flow path When the stacked fuel cell 38 is provided with the fuel cell 22a, there is a difference in cooling efficiency between the unit cells 2.
[0054]
As a result, the temperatures of the fuel electrodes 14a, 14b (hereinafter, referred to as "anode temperature") and the temperatures of the air electrodes 16a, 16b (hereinafter, referred to as "cathode temperature") are changed from the refrigerant flow path 22a. A difference occurs according to the distance. This temperature difference tends to increase as the current density of the stacked fuel cell 38 increases, as shown in FIG.
[0055]
When the air having the same flow rate and the same humidification amount is uniformly supplied to such a stacked fuel cell 38, the saturated water vapor pressure p is increased between the air electrode 16a and the air electrode 16b._Wc-satAre different from each other, the maximum drainage amount W on the air electrodes 16a and 16b side is_Cout-MAXAnd the water balance of some of the electrolyte membranes 12 is excessive or insufficient.
[0056]
Therefore, for example, when the humidification amount on the side of the air electrodes 16a and 16b is set in accordance with the air electrode 16a having a low cathode temperature, when the current density is low, as shown in FIG. However, as shown in FIG. 9B, when the current density is high, the cell voltage of the air electrode 16b having a high cathode temperature decreases due to dry-up, and the output of the entire stack fuel cell 38 decreases.
[0057]
As shown in FIG. 10 (b), a solid polymer electrolyte membrane is used as the electrolyte membrane 12, and each time three unit cells 2 having the same gas flow path structure and electrode structure are stacked, the refrigerant flow path 22a The same applies to the case where the stacked fuel cell 39 is provided, and a temperature difference occurs between the cathode temperature and the anode temperature according to the distance from the refrigerant flow path 22a as shown in FIG.
[0058]
Therefore, for example, when the humidification amount on the cathodes 16a, 16b, 16c side is set according to the cathode 16a having the lowest cathode temperature, as shown in FIG. The voltage decreases, and the output of the entire stacked fuel cell 39 decreases.
[0059]
On the other hand, in the stacked fuel cell 40 shown in FIG. 1, the cross-sectional area of the air flow path 56c on the side of the air electrode 70 having a high cathode temperature (hereinafter, referred to as “hot air electrode”) 70 has a low cathode temperature. It is smaller than the cross-sectional area of the air flow passage 54c on the side of the air electrode (hereinafter referred to as “low temperature air electrode”) 50.
[0060]
Therefore, the amount of water contained in the incoming air (hereinafter referred to as “air humidification amount”) W_CinIs set smaller in accordance with the low-temperature air electrode 50, the air flow with the air electrode (hereinafter simply referred to as “air flow”) f expressed by the equation (1) on the high-temperature air electrode 70 side._AirinBecomes smaller, the maximum drainage amount W on the high-temperature air electrode 70 side is reduced._Cout-MAXCan be reduced. As a result, a decrease in cell voltage due to dry-up on the high-temperature air electrode 70 side is suppressed, and the output of the entire stacked fuel cell 40 can be improved.
[0061]
Similarly, the air humidification amount W_CinIs set to be large in accordance with the high temperature air electrode 70, the low air temperature_AirinBecomes larger, the maximum drainage W on the low-temperature air electrode 50 side_Cout-MAXCan be increased. As a result, a decrease in cell voltage due to flooding on the low-temperature air electrode 50 side is suppressed, and the output of the entire stacked fuel cell 40 can be improved.
[0062]
The same applies to the case where the number of stacked cells constituting the unit module 42 is three or more. The structure of the air flow path of each cell, that is, the groove, is set so that the air flow rate decreases as the cathode temperature increases. By changing the depth, cross-sectional area, and the like, it is possible to suppress a decrease in cell voltage due to dry-up or flooding of the air electrode.
[0063]
Next, a stacked fuel cell according to a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view of a unit module 76 serving as a basic structure of a stacked fuel cell 74 according to a second embodiment of the present invention.
[0064]
In FIG. 2, the unit module 76 has a groove depth D of the air flow path 56c on the high-temperature air electrode 70 side._C2To the depth D of the groove of the air passage 54c on the low-temperature air electrode 50 side._C1It has the same configuration as the unit module 42 shown in FIG. 1 except that a porous body 78 is provided on the inlet side of the air flow path 56c.
[0065]
According to the stacked fuel cell 74 in which the unit modules 76 having such a configuration are stacked, the flow resistance of the air flow path 56c on the high-temperature air electrode 70 side is larger than the air flow path 54c on the low-temperature air electrode 50 side. Therefore, when air having the same pressure and humidification amount is supplied thereto, the air flow rate on the high-temperature air electrode 70 side can be reduced.
[0066]
Therefore, the air humidification amount W_CinIs set to be small according to the low-temperature air electrode 50, it is possible to suppress a decrease in cell voltage due to dry-up on the high-temperature air electrode 70 side. Similarly, the air humidification amount W_CinIs set to be large in accordance with the high temperature air electrode 70, it is possible to suppress a decrease in cell voltage due to flooding on the low temperature air electrode 50 side.
[0067]
The same applies to the case where the number of stacked cells constituting the unit module 76 is three or more, and the structure of the air flow path of each cell, that is, the porous body, is set such that the air flow rate decreases as the cathode temperature increases. By changing the cross-sectional area, size, pore diameter, porosity, and the like, it is possible to suppress a decrease in cell voltage due to dry-up or flooding of the air electrode.
[0068]
Next, a stacked fuel cell according to a third embodiment of the present invention will be described. FIG. 3 is a cross-sectional view of a unit module 82 which is a basic structure of a stacked fuel cell 80 according to a third embodiment of the present invention.
[0069]
In FIG. 3, the unit module 82 has a groove depth D of the air flow path 56c on the high-temperature air electrode 70 side._C2To the depth D of the groove of the air passage 54c on the low-temperature air electrode 50 side._C1The configuration is the same as that of the unit module 42 shown in FIG. 1 except that an obstacle plate 84 is provided on the inlet side of the air flow path 56c.
[0070]
According to the stacked fuel cell 80 in which the unit modules 82 having such a configuration are stacked, similarly to the unit module 76 shown in FIG. 2, the flow resistance of the air flow path 56c is increased. The air flow rate can be reduced. Thereby, dry-up and flooding due to the temperature distribution in the stacking direction are suppressed, and the output of the entire stacked fuel cell 80 can be improved.
[0071]
The same applies to the case where the number of stacked cells constituting the unit module 82 is three or more, and the structure of the air flow path of each cell, that is, the obstacle plate, is set so that the air flow rate decreases as the cathode temperature increases. By changing the area, mounting angle, shape, and the like, it is possible to suppress a decrease in cell voltage caused by dry-up or flooding of the air electrode.
[0072]
Next, a stacked fuel cell according to a fourth embodiment of the present invention will be described. FIG. 4 shows a cross-sectional view of a unit module 88 which is a basic structure of a stacked fuel cell 86 according to a fourth embodiment of the present invention.
[0073]
In FIG. 4, the unit module 88 has a groove depth D of the air flow path 56c on the high-temperature air electrode 70 side._C2And the depth D of the groove of the air flow passage 54c on the low-temperature air electrode 50 side._C1And has the same configuration as the unit module 42 shown in FIG. 1 except that protrusions 56d and 54d are provided on the outlet side of the air flow path 56c and the inlet side of the air flow path 54c, respectively. .
[0074]
According to the stacked fuel cell 86 in which the unit modules 88 having such a structure are stacked, the protrusion 56d is provided on the outlet side in the air flow path 56c on the high-temperature air electrode 70 side. The flow path resistance increases. On the other hand, since the projection 54d is provided on the inlet side of the air flow path 54c on the low-temperature air electrode 50 side, the flow path resistance on the inlet side increases. As a result, the internal pressure in the air passage 56c becomes higher than the internal pressure in the air passage 54c.
[0075]
Therefore, the air humidification amount W_CinIs set small in accordance with the low-temperature air electrode 50, the high-temperature air electrode 70 has the cathode-side cell internal pressure P_CBecomes larger, the maximum drainage amount W on the high-temperature air electrode 70 side_Cout-MAXCan be reduced. As a result, a decrease in the cell voltage due to the dry-up of the high-temperature air electrode 70 is suppressed, and the output of the entire stacked fuel cell 86 can be improved.
[0076]
Similarly, the air humidification amount W_CinIs set large in accordance with the high-temperature air electrode 70, the low-temperature air electrode 50 has the cathode-side internal pressure P_CBecomes smaller, so that the maximum drainage amount W on the low-temperature air electrode 50 side is reduced._Cout-MAXCan be increased. As a result, a decrease in cell voltage due to flooding of the low-temperature air electrode 50 is suppressed, and the output of the entire stacked fuel cell 86 can be improved.
[0077]
The same applies to the case where the number of stacked cells constituting the unit module 88 is three or more. The structure of the air flow path of each cell, that is, the internal pressure of the air flow path increases as the cathode temperature increases, that is, By changing the size of the projection, the mounting position, and the like, it is possible to suppress a decrease in cell voltage due to dry-up or flooding on the air electrode side.
[0078]
Next, a stacked fuel cell according to a fifth embodiment of the present invention will be described. Although not shown, a unit module serving as a basic structure of the stacked fuel cell according to the fifth embodiment of the present invention has a groove depth D of the air flow channel 56c on the high-temperature air electrode 70 side._C2And the depth D of the groove of the air flow passage 54c on the low-temperature air electrode 50 side._C1And has the same configuration as the unit module 42 shown in FIG. 1 except that the air permeability of the high-temperature air electrode 70 is smaller than the air permeability of the low-temperature air electrode 50.
[0079]
According to the stacked fuel cell in which the unit cells having different electrode structures are stacked, the water W generated by the electrode reaction shown in the equation (2) is low because the air permeability of the high-temperature air electrode 70 is small._genAnd water W moving to the hot air electrode 70 side_dragIs hardly discharged through the high-temperature air electrode 70 toward the air flow path 56c.
[0080]
Therefore, the air humidification amount W_CinIs set small in accordance with the low temperature air electrode 50, the maximum drainage W on the high temperature air electrode 70 side_Cout-MAXIs calculated as the total water supply W_Cin-totalAlthough it is larger, the amount of water actually discharged is W_Cin-totalSmaller. As a result, a decrease in the cell voltage due to the dry-up on the high-temperature air electrode 70 side is suppressed, and the output of the entire stacked fuel cell can be improved.
[0081]
Similarly, the air humidification amount W_CinIs set to be large according to the high-temperature air electrode 70, the discharge of water from the low-temperature air electrode 50 is promoted because the low-temperature air electrode 50 has high permeability. As a result, a decrease in cell voltage due to flooding of the low-temperature air electrode 50 is suppressed, and the output of the entire stacked fuel cell can be improved.
[0082]
The same applies to the case where the number of stacked unit cells constituting the unit module is three or more. The electrode structure of the air electrode of each unit cell, that is, the air permeability of the air electrode decreases as the cathode temperature increases, that is, By changing the thickness, pore diameter, porosity, etc. of the diffusion layer, it is possible to suppress a decrease in cell voltage due to dry-up or flooding on the air electrode side.
[0083]
As described above, in order to suppress dry-up and flooding on the air electrode side due to temperature variation of each unit cell included in the stacked fuel cell, the water balance on the air electrode side is balanced, and the water content of the electrolyte membrane is adjusted. It is effective to eliminate the unevenness of the state. This is the same on the fuel electrode side. Hereinafter, a specific method for balancing the water balance on the fuel electrode side will be described.
[0084]
FIG. 5 is a cross-sectional view of a unit module 92 which is a basic structure of a stacked fuel cell 90 according to a sixth embodiment of the present invention. In FIG. 5, the unit module 92 includes a fuel electrode 56 having a high anode temperature (hereinafter, referred to as a “high-temperature fuel electrode”)._A1Is the depth D of the fuel passage 58a on the fuel electrode 68 having a lower anode temperature (hereinafter referred to as a "low temperature fuel electrode")._A2It is getting bigger.
[0085]
In the case of the present embodiment, the depth D of the groove of the air flow path 56c on the high-temperature air electrode 70 side is set._C2Is the depth D of the groove of the air passage 54c on the low-temperature air electrode 50 side._C1Is the same as In other respects, it has the same configuration as the unit module 42 shown in FIG.
[0086]
Next, the operation of the stacked fuel cell 90 according to the sixth embodiment of the present invention will be described. Assuming that the supply of water to the cells 44 and 45 and the discharge of water from the cells 44 and 45 are all performed in the form of water vapor, the amount of water supplied to the fuel electrodes 48 and 68 Is equal to the amount of moisture contained in the fuel-containing gas (hereinafter referred to as “fuel humidification amount”). Therefore, the fuel humidification amount is W_AinIn other words, W_AinCan be expressed by the following equation (3).
[0087]
(Equation 3)

[0088]
In addition, the amount of water discharged outside the fuel cell together with the fuel electrode gas (hereinafter referred to as “total drainage amount”) is W_AoutIn other words, the total drainage W_AoutCan be expressed by the following equation (4).
[0089]
(Equation 4)

[0090]
Further, the amount of water supplied from the fuel electrodes 48 and 68 to the electrolyte membranes 46 and 66 (hereinafter referred to as “replenishment water amount”) is W_AgainIn other words, make-up water amount W_AgainCan be expressed by the following equation 5 from the equations 3 and 4.
[0091]
(Equation 5)

[0092]
Here, the total drainage W on the fuel electrode 48, 68 side_AoutIs the fuel humidification amount W_AinIf the amount is smaller, the moisture on the fuel electrode 48, 68 side will be slightly excessive. Conversely, W_AoutIs W_AinIf more, the atmosphere is dry. Therefore, in order to maintain stable power generation performance, it is important to balance these balances and properly maintain the water content of the electrolyte membranes 46, 66 on the fuel electrode 48, 68 side.
[0093]
By the way, the saturated steam pressure p in the equation (4)_WA-satIs a parameter determined only by the anode temperature, and increases as the temperature increases. Therefore, when a fuel gas having the same humidification amount is uniformly supplied to a stacked fuel cell having the same fuel channel structure and electrode structure of all the cells, when a difference occurs in the anode temperature, , The saturated water vapor pressure p on each fuel electrode side_WA-satIs different, the total drainage W on the fuel electrode side is_AoutAnd the water balance of some of the electrolyte membranes is excessive or insufficient. As a result, the cell voltage varies due to dry-up or flooding.
[0094]
On the other hand, according to the stacked fuel cell 90 shown in FIG. 5, the cross-sectional area of the fuel passage 56a on the high-temperature fuel electrode 48 side is larger than the cross-sectional area of the fuel flow passage 58a of the low-temperature fuel electrode 68. The fuel flow rate into the fuel electrode on the high-temperature fuel electrode 48 side (hereinafter simply referred to as “fuel flow rate”) f_HinCan be increased.
[0095]
Therefore, even if the mole fraction of water in the incoming fuel gas (hereinafter referred to as “water inlet mole fraction”) x is set to be small in accordance with the low temperature fuel electrode 68, Fuel flow rate f shown in equation (3)_Hin, The fuel humidification amount W_Ain, That is, the amount of makeup water W_AgainCan be increased.
[0096]
This is usually due to the amount of hydrogen consumed in the reaction C_H2Is constant and the mole fraction x of the incoming water is controlled to be larger than the mole fraction X of the water in the outgas. As a result, a decrease in the cell voltage due to the dry-up of the high-temperature fuel electrode 48 is suppressed, and the output of the entire stacked fuel cell 90 can be improved.
[0097]
Similarly, even when the incoming water mole fraction x is set to be large in accordance with the high-temperature fuel electrode 48, the fuel flow rate f_Hin, The fuel humidification amount W_Ain, That is, the amount of makeup water W_AgainCan be reduced. As a result, a decrease in cell voltage due to flooding of the low-temperature fuel electrode 68 is suppressed, and the output of the entire stacked fuel cell 90 can be improved.
[0098]
The same applies to the case where the number of stacked unit cells constituting the unit module 92 is three or more. The structure of the fuel flow path of each unit cell, that is, the groove, is set so that the fuel flow rate increases as the anode temperature increases. By changing the depth, the cross-sectional area, and the like, it is possible to suppress a decrease in cell voltage due to dry-up or flooding on the fuel electrode side.
[0099]
Next, a stacked fuel cell according to a seventh embodiment of the present invention will be described. FIG. 6 is a sectional view of a unit module 96 serving as a basic structure of a stacked fuel cell 94 according to a seventh embodiment of the present invention.
[0100]
In FIG. 6, the unit module 96 has a groove depth D of the fuel flow path 56a on the high-temperature fuel electrode 48 side._A1And the depth D of the groove of the fuel passage 58a on the low-temperature fuel electrode 68 side._CA2And has the same configuration as the unit module 92 shown in FIG. 5 except that protrusions 56f and 58f are provided on the outlet side of the fuel passage 56a and the inlet side of the fuel passage 58a, respectively. .
[0101]
According to the stacked fuel cell 94 in which the unit modules 96 having such a structure are stacked, the fuel flow path 56a on the high-temperature fuel electrode 48 side is provided with the projection 56f on the outlet side. The flow path resistance increases. On the other hand, the fuel flow path 58a on the low temperature fuel electrode 68 side is provided with the projection 58f on the inlet side, so that the flow path resistance on the inlet side increases. As a result, the internal pressure in the fuel flow path 56a becomes higher than the internal pressure in the fuel flow path 58a.
[0102]
Therefore, the fuel humidification amount W_AinIs set small in accordance with the low-temperature fuel electrode 68, the anode-side cell internal pressure P_ABecomes larger, the total drainage W on the high-temperature fuel electrode 48 side_AoutCan be reduced. As a result, a decrease in the cell voltage due to the dry-up of the high-temperature fuel electrode 48 is suppressed, and the output of the entire stacked fuel cell 94 is improved.
[00103]
Similarly, the fuel humidification amount W_AinIs set to be large in accordance with the high-temperature fuel electrode 48, on the low-temperature fuel electrode 68 side, the anode-side cell internal pressure P_ABecomes smaller, the total drainage W on the low temperature fuel electrode 68 side_AoutCan be increased. As a result, a decrease in cell voltage due to flooding of the low-temperature fuel electrode 68 is suppressed, and the output of the entire stacked fuel cell 94 is improved.
[0104]
The same applies to the case where the number of stacked unit cells constituting the unit module 96 is three or more. The structure of the fuel passage of each unit cell, that is, the internal pressure of the fuel passage increases as the anode temperature increases, that is, By changing the size of the protrusion, the mounting position, and the like, it is possible to suppress a decrease in cell voltage due to dry-up or flooding on the fuel electrode side.
[0105]
As described above, in order to suppress the dry-up and flooding caused by the temperature variation of each unit cell which occurs in the stacked fuel cell, the water balance on the fuel electrode side is balanced and the water content of each electrolyte membrane is not properly adjusted. It is necessary to eliminate uniformity. To this end, it is effective to change the structure of the fuel flow path or the electrode structure of the fuel electrode of each cell according to the temperature environment.
[0106]
Next, the fuel cell system according to the present invention will be described. FIG. 12 shows a block diagram of a fuel cell system according to the present invention. In FIG. 12, the fuel cell system 100 includes a stacked fuel cell 102, a reaction gas supply device 104, a humidification amount control device 106, a reaction gas supply control device 108, and a cell operation status detection device 110. .
[0107]
The stacked fuel cell 102 includes a unit module in which a plurality of unit cells are stacked, and cooling means provided every time the unit modules are stacked. FIG. 13 shows a cross-sectional view of the stacked fuel cell 102. In the stacked fuel cell 102 illustrated in FIG. 13, the unit module 102c is formed by stacking two unit cells 102a and 102b, and a cooling device 102d is arranged between the unit modules 102c.
[0108]
Since the cells 102a and 102b provided in the unit module 102c have different temperature environments, they are referred to as a group of the cells 102a (hereinafter, referred to as “group 1”) and a group of the cells 102b (hereinafter, referred to as “group 1”). The air and the fuel gas are distributed through a branched air manifold and a fuel manifold (indicated by solid lines and dotted lines in FIG. 13).
[0109]
FIG. 14 shows a perspective view of the stacked fuel cell 102. In FIG. 14, the stacked fuel cell 102 is provided with two air inlets 102f and 102g and two air outlets 102h and 102i. Among them, the air inlet 102f and the air outlet 102h are both connected to the air flow path of each of the unit cells 102a belonging to the group 1, and the air supplied from one of the branched air manifolds is supplied to the air inlet 102f. From the cells 102a, and collects the gas discharged from the cells 102a and discharges the gas from the air outlet 102h.
[0110]
Similarly, the air inlet 102g and the air outlet 102i are both connected to the air flow path of each of the cells 102b belonging to Group 2, and the air supplied from the other of the branched air manifolds is supplied to the air inlet 102g. From the cells 102b, the gas discharged from the cells 102b is collected and discharged from the air outlet 102i.
[0111]
Further, the stacked fuel cell 102 is provided with two fuel inlets 102j and 102k and two fuel outlets 102l and 102m. Among them, the fuel inlet 102j and the fuel outlet 102l are both connected to the fuel flow path of each of the unit cells 102a belonging to the group 1, and the reformed gas supplied from one of the branched fuel manifolds is supplied to the fuel inlet. The gas is distributed from the port 102j to each cell 102a, and the gas discharged from each cell 102a is collected and discharged from the fuel discharge port 102l.
[0112]
Similarly, the fuel inlet 102k and the fuel outlet 102m are both connected to the fuel flow path of each of the unit cells 102b belonging to Group 2, and the reformed gas supplied from the other of the branched fuel manifolds is supplied to the fuel inlet. The gas is distributed to each unit cell 102b from the port 102k, and the gas discharged from each unit cell 102b is collected and discharged from the fuel outlet 102m.
[0113]
In the fuel cell system 100 according to the present invention, the gas flow channel structure and the electrode structure of the unit cells 102a and 102b constituting the unit module 102c may be the same, or may be different depending on the temperature. May be provided. Further, the specific structure for distributing the reaction gas supplied from the branched manifold to each unit cell group is not limited to the structure illustrated in FIG. 14, and the cooling device 102 d is also illustrated in FIG. However, the present invention is not limited to the structure illustrated in FIG.
[0114]
Furthermore, the present invention is preferably applied to a fuel cell requiring control of the water content of the electrolyte membrane, specifically, a polymer electrolyte fuel cell, a phosphoric acid fuel cell, or an alkaline fuel cell. In particular, when the present invention is applied to a polymer electrolyte fuel cell, due to uneven water balance of the electrolyte membrane or relative excess or deficiency of the reaction gas without lowering the output per unit volume. Therefore, there is an advantage that a fuel cell system suitable for a vehicle-mounted power source can be obtained.
[0115]
The reaction gas supply device 104 includes a fuel reformer 104a, a fuel supply device 104b, and a water supply device 104c for supplying a predetermined amount of reformed gas to the fuel electrode of each unit cell, and an air electrode of the stacked fuel cell 102. And a power supply for controlling the total supply of reformed gas and air based on the operation status of the stacked fuel cell 102 detected by the battery operation status detection device 110. It comprises a quantity control device 104e.
[0116]
As is well known, the fuel reformer 104a is a device that generates a reformed gas containing hydrogen as a main component by causing a reforming reaction between fuel vapor made of methanol or the like and steam in the presence of a catalyst. Fuel vapor and water vapor necessary for the quality reaction are supplied from a fuel supply device 104b and a water supply device 104c, respectively.
[0117]
The humidification amount control device 106 humidifies by adding a predetermined amount of moisture to the reformed gas and air supplied to the stacked fuel cell 102, and individually adjusts the humidification amount for each cell group having a different temperature environment. It is a device for controlling. Therefore, the humidification amount controller 106 includes two fuel humidification amount controllers 106a and 106b and two air humidification amount controllers 106c and 106d.
[0118]
The fuel reformer 104a and the fuel humidification control devices 106a and 106b are connected via a branched fuel manifold, and the reformed gas generated in the fuel reformer 104a is supplied to the fuel humidification control device 106a. And 106b. Further, the fuel humidification amount control devices 106a and 106b are connected to the fuel inlet 102j of the group 1 and the fuel inlet 102k of the group 2 shown in FIG. 14, respectively.
[0119]
Similarly, the air supply device 104d and the air humidification amount control devices 106c and 106d are connected via a branched air manifold, and the air supplied by the air supply device 104d is supplied to the air humidification amount control devices 106c and 106d. To be distributed. Further, the air humidification amount control devices 106c and 106d are connected to the group 1 air inlet 102f and the group 2 air inlet 102g shown in FIG. 14, respectively.
[0120]
The structures of the humidifiers provided in the fuel humidification amount control devices 106a and 106b and the air humidification amount control devices 106c and 106d are not particularly limited. That is, it may be a humidifier that humidifies using steam or a humidifier that humidifies using mist.
[0121]
The reaction gas supply control device 108 is a device for individually controlling the flow rate and / or pressure of the reaction gas for each unit cell group having a different temperature environment. Therefore, the reaction gas supply control device 108 includes two fuel gas supply control devices 108a and 108b and two air supply control devices 108c and 108d.
[0122]
The fuel gas supply control devices 108a and 108b are respectively connected to the fuel outlet 102l of group 1 and the fuel outlet 102m of group 2 shown in FIG. Further, the air supply control devices 108c and 108d are connected to the air outlet 102h of the group 1 and the air outlet 102i of the group 2 shown in FIG. 14, respectively.
[0123]
In addition, various methods can be considered as a method of individually controlling the flow rate and the pressure of the reaction gas supplied to each unit cell. Specifically, by adjusting the pump rotation speed and the like provided in the reaction gas supply device 104, the total supply amount of fuel gas and air is controlled, and the valve opening and the like provided in the reaction gas supply control device 108 are adjusted. By adjusting, the flow path resistance of each reaction gas flow path may be individually controlled.
[0124]
In FIG. 12, the reaction gas supply control devices 108 (the fuel gas supply control devices 108a and 108b and the air supply control devices 108c and 108d) are all provided on the outlet side of the stacked fuel cell 102. However, the reaction gas supply control device 108 is on the inlet side, that is, between the fuel humidification control devices 106a and 106b and the stacked fuel cell 102, and between the air humidification control devices 106c and 106d and the stacked fuel cell 102. Each of them may be provided to individually control the flow rate and pressure of the reaction gas.
[0125]
Alternatively, the reaction gas supply control device 108 may be provided on both the inlet side and the outlet side of the stacked fuel cell 102, and these may be used to individually control the flow rate and pressure of the reaction gas.
[0126]
The battery operation state detection device 110 has a function of detecting the operation state of the stacked fuel cell 102 and, based on the measured operation state, a gas flow rate, a pressure, And a function for calculating the humidification amount.
[0127]
Here, the “operation state” specifically refers to a cell voltage, a resistance value of an electrolyte membrane, a cell temperature, a cell internal pressure, and a hydrogen concentration and an oxygen concentration contained in exhaust gas. Further, these operating states are individually detected for the unit cells 102a belonging to the group 1 and the unit cells 102b belonging to the group 2.
[0128]
Further, the control parameters such as the gas flow rate calculated by the battery operation state detection device 110 are the power generation amount control device 104e, the fuel humidification amount control devices 106a and 106b, the air humidification amount control devices 106c and 106d, and the fuel gas supply control device 108a. , 108b and the air supply control devices 108c, 108d.
[0129]
The operation status detection by the battery operation status detection device 110 may be performed for all the stacked cells, or, as shown in FIG. 13, a representative 1 or 2 selected from each group. The above procedure may be applied to the unit cells.
[0130]
Next, a general operation of the fuel cell system 100 shown in FIG. 12 will be described. First, the operation state of the stacked fuel cell 102 is monitored by the cell operation state detection device 110. If a difference occurs between the cell voltages of the unit cells 102a belonging to the group 1 and the unit cells 102b belonging to the group 2, it is necessary for the battery operation state detecting device 110 to reduce the cell voltage difference. The flow rate and pressure of the reformed gas and air, and the amount of humidification of the reformed gas and air are calculated.
[0131]
Next, the calculated flow rates and pressures of the reformed gas and air are supplied to the power generation amount control device 102e and the fuel gas supply control devices 108a and 108b and the air supply control devices 108c and 108d, and the calculated humidification amount is supplied to the fuel humidification. It is output to the amount control devices 106a and 106b and the air humidification amount control devices 106c and 106d, respectively.
[0132]
The power generation amount control device 104e outputs a control signal to the fuel supply device 104b and the water supply device 104c based on the calculated flow rate and pressure of the reformed gas, each of which is required to generate a predetermined amount of reformed gas. The fuel vapor and the steam are supplied to the fuel reformer 104a.
[0133]
In the fuel reformer 104a, a reformed gas is generated from the supplied fuel vapor and steam by a reforming reaction. The generated reformed gas is distributed to the fuel humidification amount control devices 106a and 106b via the branched fuel manifold. At this time, the ratio and pressure of the reformed gas distributed to the fuel humidification controllers 106a and 106b are individually controlled by the fuel gas supply controllers 108a and 108b provided on the exhaust side of the stacked fuel cell 102. .
[0134]
When the reformed gas is distributed to the fuel humidification amount control devices 106a and 106b, a predetermined amount of water is added based on the humidification amount calculated by the battery operation state detection device 110. Then, the reformed gas whose humidification amount is individually controlled is supplied to the fuel electrode of each unit cell 102a belonging to group 1 and the fuel electrode of each unit cell 102b belonging to group 2.
[0135]
Similarly, the air supply device 104d supplies a predetermined amount of air to the stacked fuel cell 102 based on the flow rate and pressure of the air calculated by the battery operation state detection device 110. The supplied air is distributed to the air humidification amount control devices 106c and 106d via the branched air manifolds. At this time, the ratio and pressure of the air distributed to the air humidification amount control devices 106c and 106d are individually controlled by the air supply control devices 108c and 108d provided on the exhaust side of the stacked fuel cell 102.
[0136]
When the air is distributed to the air humidification amount control devices 106c and 106d, a predetermined amount of water is added based on the humidification amount calculated by the battery operation state detection device 110. Then, the air whose humidification amount is individually controlled is supplied to the air electrode of each cell 102a belonging to group 1 and the air electrode of each cell 102b belonging to group 2.
[0137]
When the reformed gas and the air whose flow rates, pressures, and humidification amounts are individually controlled are supplied to the unit cells 102a belonging to the group 1 and the unit cells 102b belonging to the group 2 of the stacked fuel cell 102, The cell voltage of the cell 102a belonging to the group 1 and / or the cell voltage of the cell 102b belonging to the group 2 change. Therefore, the changed cell voltage of each unit cell is detected again by the battery operation state detection device 110, and these are compared. Then, the above-described control is repeated until the difference between the cell voltages of the unit cells 102a and 102b becomes equal to or smaller than a predetermined value.
[0138]
Next, a specific operation method for reducing the difference between the cell voltages of the cells having different temperature environments will be described. FIG. 15 shows an example of the control flowchart. First, in step 1 (hereinafter simply referred to as “S1”) shown in FIG. 15, the cell voltage V₁And the cell voltage V of the cell 102b belonging to the group 2₂Is detected by the battery operation status detection device 110.
[0139]
Next, in S2, the cell voltage V₁And cell voltage V₂Are determined to be equal. Cell voltage V₁And cell voltage V₂Are equal (S2: YES), the flow returns to S1, and the cell voltage V₁And cell voltage V₂Each of the above-described steps S1 and S2 is repeated until the variation of the above occurs. On the other hand, the cell voltage V₁And cell voltage V₂Are not equal to each other (S2: NO), it indicates that there is a relative excess or deficiency in the supply amount of the reaction gas of each cell, and the process then proceeds to S3.
[0140]
In S3, the cell voltage V₁Is the cell voltage V₂It is determined whether it is greater than. Cell voltage V₁Is the cell voltage V₂If it is larger (S3: YES), the process proceeds to S4, and the oxygen concentration in the gas discharged from the air electrode of the cell 102a belonging to the group 1 (hereinafter referred to as "oxygen concentration X₀₁") And the oxygen concentration in the gas discharged from the air electrode of the cell 102b belonging to the group 2 (hereinafter referred to as" oxygen concentration X_O2) Is detected by the battery operation status detection device 110.
[0141]
Next, in S5, the oxygen concentration X₀₂Is the oxygen concentration X_O1It is determined whether or not this is the case. Oxygen concentration X₀₂Is the oxygen concentration X_O1If not (S5: NO), the cell voltage V is low because the air supplied to the cell 102b is relatively short.₂Has decreased. Therefore, in this case, the process proceeds to S6, and the flow rate of the air supplied to the single cell 102b (hereinafter referred to as “air flow rate f_Airin(2) ").
[0142]
On the other hand, the oxygen concentration X₀₂Is the oxygen concentration X_O1If it is equal to or greater than (S5: YES), the voltage V₂Indicates that the decrease is not due to the relative shortage of the amount of air supplied to the cell 102b, and the process proceeds to S7 as it is.
[0143]
In S7, the hydrogen concentration in the gas discharged from the fuel electrode of the cell 102a belonging to the group 1 (hereinafter referred to as “hydrogen concentration X_H1") And the hydrogen concentration in the gas discharged from the fuel electrode of the cell 102b belonging to the group 2 (hereinafter referred to as" hydrogen concentration X_H2) Is detected by the battery operation status detection device 110.
[0144]
Next, in S8, the hydrogen concentration X_H2Is the hydrogen concentration X_H1It is determined whether or not this is the case. Hydrogen concentration X_H2Is the hydrogen concentration X_H1If not (S8: NO), the cell voltage V becomes low because the fuel supplied to the cell 102b is relatively short.₂Has decreased. Therefore, in this case, the process proceeds to S9, and the flow rate of the fuel supplied to the single cell 102b (hereinafter referred to as “fuel flow rate f_Hin(2) ").
[0145]
On the other hand, the voltage V₂If the decrease is caused only by the non-uniformity of the air flow rate, in S8, the hydrogen concentration X_H2Is the hydrogen concentration X_H1Since it is determined that this is the case (S8: YES), the process returns to S1 in this case. And the cell voltage V₁And cell voltage V₂Are repeated until the values match.
[0146]
In S3, the cell voltage V₁Is the cell voltage V₂If it is determined that it is not larger (S3: NO), the process proceeds to S10, where the oxygen concentration X₀₁And oxygen concentration X_O2Is detected by the battery operation status detection device 110.
[0147]
Next, in S11, the oxygen concentration X₀₁Is the oxygen concentration X_O2It is determined whether or not this is the case. Oxygen concentration X₀₁Is the oxygen concentration X_O2If not (S11: NO), the cell voltage V is low because the air supplied to the cell 102a is relatively short.₁Has decreased. Therefore, in this case, the process proceeds to S12, and the air flow rate supplied to the single cell 102a (hereinafter referred to as “air flow rate f_Airin(1) ”).
[0148]
On the other hand, the oxygen concentration X₀₁Is the oxygen concentration X_O2If the above is true (S11: YES), the cell voltage V₁Indicates that the decrease is not due to the relative shortage of the amount of air supplied to the cell 102a, and the process proceeds to S13 as it is. In S13, the hydrogen concentration X_H1And hydrogen concentration X_H2Is detected by the battery operation status detection device 110.
[0149]
Next, at S14, the hydrogen concentration X_H1Is the hydrogen concentration X_H2It is determined whether or not this is the case. Hydrogen concentration X_H1Is the hydrogen concentration X_H2If not (S14: NO), the cell voltage V is low because the fuel gas supplied to the cell 102a is relatively short.₁Has decreased. Therefore, in this case, the process proceeds to S15, where the fuel gas supply control device 108a uses the fuel flow rate (hereinafter referred to as “fuel flow rate f”) to be supplied to the unit cell 102a._Hin(1) ”).
[0150]
On the other hand, the cell voltage V₁If the decrease is caused only by the non-uniformity of the air flow rate, in S14, the hydrogen concentration X_H1Is the hydrogen concentration X_H2It is determined that this is the case (S14: YES), and in this case, the process returns to S1. And the cell voltage V₁And cell voltage V₂Are repeated, the steps S1 to S3 and S10 to S15 described above are repeated.
[0151]
As described above, according to the operation method of the stacked fuel cell shown in FIG. 15, the air flow rate and the fuel flow rate are individually adjusted according to the oxygen concentration and the hydrogen concentration detected for each cell group having a different temperature environment. Therefore, even if the gas flow path structure and the electrode structure of each unit cell provided in the stacked fuel cell are the same, the cell voltage is reduced due to the relative excess or deficiency of the gas flow rate. Can be suppressed. In addition, thereby, the energy efficiency of the stacked fuel cell 102 can be improved.
[0152]
Next, a specific operation method for increasing and decreasing both the gas flow rate and the humidification amount so as to reduce the difference between the cell voltages of the cells having different temperature environments will be described. FIG. 16 shows an example of the control flowchart. First, in S21 shown in FIG. 16, the cell voltage V of the cell 102a belonging to the group 1₁And the cell voltage V of the cell 102b belonging to the group 2₂Is detected by the battery operation status detection device 110.
[0153]
Next, at S22, the cell voltage V₁And cell voltage V₂Are determined to be equal. Cell voltage V₁And cell voltage V₂Are equal to each other (S22: YES), the flow returns to S21, and the cell voltage V₁And cell voltage V₂Are repeated until the above-mentioned fluctuation occurs. On the other hand, the cell voltage V₁And cell voltage V₂Is not equal (S22: NO), it indicates that relative excess or deficiency has occurred in the supply amount and / or humidification amount of the reaction gas of each cell, and the process proceeds to S23.
[0154]
In S23, the cell voltage V₁Is the cell voltage V₂It is determined whether it is greater than. Cell voltage V₁Is the cell voltage V₂If larger (S23: YES), the process proceeds to S24, where the membrane resistance R of the electrolyte membrane of the unit cell 102a is set.₁And the membrane resistance R of the electrolyte membrane of the cell 102b₂Is detected by the battery operation status detection device 110. Further, in S25, the film resistance R₁Is the film resistance R₂It is determined whether or not this is the case.
[0155]
Film resistance R₁Is the film resistance R₂If not (S25: NO), that is, the film resistance R₂Is larger than the amount of water supplied to the single cell 102b, the amount of water discharged from the single cell 102b is larger than that of the single cell 102b. V₂Has decreased. Therefore, in this case, the process proceeds to S26.
[0156]
In S26, a means for resolving a shortage of water in the single cell 102b is executed. For example, the cell voltage V₂If the decrease in the flow rate is caused by a shortage of water on the air electrode side of the cell 102b, the air flow rate f is determined using the air supply control device 108d._airin(2) may be reduced. Thereby, the amount of moisture discharged from the air electrode side of the cell 102b can be reduced. Alternatively, the air humidification amount W of the cell 102b is determined using the air humidification amount control device 106d._Cin(2) may be increased. Thereby, the amount of water supplied to the air electrode side of the cell 102b can be increased.
[0157]
Also, the cell voltage V₂If the decrease of the fuel cell is caused by the shortage of the water amount on the fuel electrode side of the cell 102b, the fuel humidification amount W of the cell 102b is_Ain(2) may be increased, thereby increasing the amount of water supplied to the fuel electrode side.
[0158]
Further, the air flow rate f_airin(2), air humidification amount W_Cin(2) and fuel humidification amount W_AinAt least one or more control parameters selected from (2) may be combined and controlled simultaneously so that the water balance of the single cell 102b is maintained.
[0159]
On the other hand, the film resistance R₁Is the film resistance R₂If the above is the case (S25: YES), that is, the film resistance R₂Is smaller, the amount of water supplied to the cell 102b is larger than the amount of water discharged from the cell 102b, and flooding occurs in the cell 102b, thereby causing the cell voltage V₂Has decreased. Therefore, in this case, the process proceeds to S27.
[0160]
In S27, a means for eliminating excess moisture in the single cell 102b is executed. For example, the cell voltage V₂Is decreased due to excess moisture on the air electrode side of the cell 102b, the air flow rate f_airin(2) may be increased to increase the amount of water discharged from the air electrode side. Alternatively, the air humidification amount W_Cin(2) may be reduced to reduce the amount of water supplied to the air electrode side.
[0161]
Also, the cell voltage V₂Is decreased due to excess moisture on the fuel electrode side of the cell 102b, the fuel humidification amount W_Ain(2) may be reduced to reduce the amount of water supplied to the fuel electrode side. Further, the air flow rate f_airin(2), air humidification amount W_Cin(2) and fuel humidification amount W_AinAt least one or more control parameters selected from (2) may be combined and controlled simultaneously so that the water balance of the single cell 102b is maintained.
[0162]
In S26 or S27, the air flow rate f_airin(2), air humidification amount W_Cin(2) and fuel humidification amount W_AinAfter at least one or more selected from (2) is controlled, the process returns to S21. And the cell voltage V₁And cell voltage V₂Are repeated, until steps S21 to S27 match.
[0163]
On the other hand, in S23, the cell voltage V₁Is the cell voltage V₂If it is determined that it is not larger (S23: NO), the process proceeds to S28, where the film resistance R₁And film resistance R₂Is detected. Further, in S29, the film resistance R₁Is the film resistance R₂It is determined whether or not:
[0164]
Film resistance R₁Is the film resistance R₂Otherwise (S29: NO), that is, the film resistance R₁Is larger, the amount of water in the single cell 102a is insufficient, and the cell voltage V₁Has decreased. Therefore, in this case, the process proceeds to S30, and means for solving the shortage of the water content in the unit cell 102a is executed.
[0165]
For example, the cell voltage V₁If the decrease in the flow rate is caused by a shortage of the water content on the air electrode side of the cell 102a, the air flow rate f is determined using the air supply control device 108c._airin(1) is reduced, or the air humidification amount W is controlled by using the air humidification amount control device 106c._Cin(1) may be increased.
[0166]
Also, the cell voltage V₁If the decrease in the fuel humidification amount is caused by a shortage of water content on the fuel electrode side of the unit cell 102a, the fuel humidification amount W is determined using the fuel humidification amount control device 106a._Ain(1) may be increased. Furthermore, one or more control parameters selected from these may be combined and controlled simultaneously so that the water balance of the single cell 102a is maintained.
[0167]
On the other hand, the film resistance R₁Is the film resistance R₂If it is below (S29: YES), that is, the film resistance R₁Is smaller, the amount of water in the single cell 102a becomes excessive, and as a result, the cell voltage V₁Has decreased.
[0168]
Therefore, in this case, the process proceeds to S31 and, contrary to the above, the air flow rate f_airin(1) increase and / or air humidification amount W_Cin(1) reduction or fuel humidification amount W_AinDue to the decrease in (1), excess moisture may be removed from the air electrode side or the fuel electrode side. Furthermore, one or more control parameters selected from these may be combined and controlled simultaneously so that the water balance of the single cell 102a is maintained.
[0169]
In S30 or S31, the air flow rate f_airin(1), air humidification amount W_Cin(1) and fuel humidification amount W_AinAfter at least one or more selected from (1) is controlled, the process returns to S21. And the cell voltage V₁And cell voltage V₂Are repeated, the steps S21 to S23 and S28 to S31 are repeated.
[0170]
As described above, according to the operation method of the stacked fuel cell illustrated in FIG. 16, the flow rate and the humidification amount of the reaction gas are individually controlled using the membrane resistance detected for each cell group having a different temperature environment. Therefore, even when the gas passage structure and the electrode structure of each unit cell are the same, it is possible to suppress the unevenness of the water content of the electrolyte membrane and the relative excess and deficiency of the supply amount of the reaction gas. it can. In addition, this makes it possible to eliminate the variation in cell voltage and improve the output of the entire stacked fuel cell.
[0171]
Next, another operation method for reducing the difference between the cell voltages of the cells having different temperature environments will be described. 17 to 19 show examples of the control flowchart. First, in S41 shown in FIG. 17, the cell voltage V of the cell 102a belonging to the group 1₁And the cell voltage V of the cell 102b belonging to the group 2₂Is detected by the battery operation status detection device 110.
[0172]
Next, in S42, the cell voltage V₁And cell voltage V₂Are determined to be equal. Cell voltage V₁And cell voltage V₂Are equal (S42: YES), the flow returns to S41, and the cell voltage V₁And cell voltage V₂Are repeated until the above-mentioned fluctuation occurs. On the other hand, the cell voltage V₁And cell voltage V₂Are not equal to each other (S42: NO), it indicates that there is a relative excess or deficiency in the reaction gas supply amount of each cell, and the process proceeds to S43.
[0173]
In S43, the cell voltage V₁Is the cell voltage V₂It is determined whether it is greater than. Cell voltage V₁Is the cell voltage V₂If it is larger (S43: YES), the process proceeds to S51 shown in FIG. In S51, the cell voltage V₂The current value of V_PAnd then the air flow rate f_airin(2) is increased. After a lapse of a predetermined time, in S52, the cell voltage V₂Is detected again, and in S53, the stored current value V_PAnd the newly detected cell voltage V₂Is compared.
[0174]
Current value V_PIs the cell voltage V₂If it is smaller (S53: YES), the air flow rate f_airin(2) is relatively short, which results in the cell voltage V₂Has decreased. Therefore, in this case, the process proceeds to S54, and the cell voltage V₂The current value of V_PAnd then the air flow rate f_airinAn operation to increase (2) is performed. After a lapse of a predetermined time, in S55, the cell voltage V₂Is detected again, and in S56, the stored current value V_PAnd the newly detected cell voltage V₂Is compared.
[0175]
Then, in S56, the current value V_PIs the cell voltage V₂If it is determined that it is smaller (S56: YES), the air flow rate f of the cell 102b is determined._airinSince it indicates that the relative shortage of (2) has not been solved yet, the process returns to S54, and the above-described steps S54 to S56 are repeated. On the other hand, the current value V_PIs the cell voltage V₂If not smaller (S56: NO), that is, the air flow rate f_airinEven if (2) is increased, the cell voltage V₂If does not increase anymore, the process returns to S41.
[0176]
On the other hand, in S53, the current value V_PIs the cell voltage V₂If it is determined that it is not smaller (S53: NO), the cell voltage V₂Of air flow f_airinThis indicates that it is not due to the relative shortage of (2). Therefore, in this case, the process proceeds to S57, and in accordance with the same procedure as described above, the air flow rate f_airinBy reducing (2), the cell voltage V₂Is determined (S57 to S59).
[0177]
Stored current value V_PIs the newly detected cell voltage V₂If smaller (S59: YES), the air flow rate f_airin(2) becomes relatively excessive, so that the cell voltage V₂Has decreased. Therefore, in this case, the process proceeds to S60, where the cell voltage V₂Until the air flow no longer increases_airin(2) is reduced (S60 to S62). And the air flow rate f_airinEven if (2) is increased, the cell voltage V₂When does not increase any more (S62: NO), the process returns to S41.
[0178]
In S59, the current value V_PIs the cell voltage V₂If it is determined that it is not smaller (S59: NO), the cell voltage V₂Is not due to the relative excess or deficiency of the air flow. Therefore, in this case, the process proceeds to S63, and the fuel flow rate f_Hin(2) increases the cell voltage V₂Is determined (S63 to S65).
[0179]
Fuel flow rate f_Hin(2) increases the cell voltage V₂If the cell voltage V has increased (S65: YES), the process proceeds to S66, where the cell voltage V₂Until the fuel flow no longer increases_Hin(2) is increased (S66 to S68). And the fuel flow rate f_HinEven if (2) is increased, the cell voltage V₂When does not increase any more (S68: NO), the process returns to S41.
[0180]
On the other hand, in S65, the fuel flow rate f_Hin(2) increases the cell voltage V₂If has not increased (S65: NO), the process proceeds to S69, and the fuel flow rate f_HinBy reducing (2), the cell voltage V₂Is determined (S69 to S71).
[0181]
Fuel flow rate f_Hin(2) reduces the cell voltage V₂If the voltage has increased (S71: YES), the process proceeds to S72, and the cell voltage V₂Until the fuel flow no longer increases_Hin(2) is reduced (S72 to S74). And the fuel flow rate f_HinEven if (2) is increased, the cell voltage V₂When does not increase any more (S71: NO or S74: NO), the process returns to S41.
[0182]
Similarly, in S43, the cell voltage V₁Is the cell voltage V₂If it is determined that it is not larger (S43: NO), the process proceeds to S81 shown in FIG. Then, according to the same procedure as described above, the air flow rate f_airin(1) increase (S81-S86) and decrease (S87-S92), and fuel flow rate f_HinThe increase (S93-S98) and decrease (S99-S104) of (1) are sequentially performed by trial and error, and the cell voltage V₁Until the cause of the decrease in the pressure is eliminated, the individual control of the reaction gas flow rate is performed.
[0183]
As described above, according to the operation method of the stacked fuel cell shown in FIGS. 17 to 19, the flow rate of the reaction gas is individually controlled for each cell group having a different temperature environment. Even when the gas flow path structure and the electrode structure are the same, it is possible to eliminate the variation in the cell voltage due to the relative excess or deficiency in the supply amount of the reactant gas. Output can be improved.
[0184]
Further, according to the operation method shown in FIGS. 17 to 19, unlike the operation method shown in FIGS. 15 and 16, an apparatus for detecting the oxygen concentration or the hydrogen concentration or a method for detecting the membrane resistance of the electrolyte membrane. Since the variation in cell voltage can be eliminated without using the above device, there is an advantage that the cost of the stacked fuel cell system can be reduced.
[0185]
【Example】
(Example 1)
A stacked fuel cell 40 having the structure shown in FIG. 1 was manufactured, and its discharge characteristics were examined. That is, two unit cells having different groove depths in the air flow path were stacked to form a unit module 42, and 25 of these were stacked to form a stacked fuel cell 40 (the number of stacked unit cells = 50 cells).
[0186]
Here, the depth D of the groove of the air flow path (hereinafter, referred to as “cooling air flow path”) 54 c on the low-temperature air electrode 50 side directly cooled by the refrigerant flow path 60._C1Is 0.6 mm, and the depth D of the groove of the air flow path 56c on the high-temperature air electrode 70 side which is not directly cooled by the refrigerant flow path 60 (hereinafter referred to as “uncooled air flow path”) 56c_C2Was 0.3 mm.
[0187]
The depth D of the groove of the fuel flow path 56a on the high-temperature fuel electrode 48 side that is not directly cooled by the refrigerant flow path 60 (hereinafter referred to as “uncooled fuel flow path”) 56a_A1And a depth D of a groove of a fuel passage (hereinafter referred to as a “cooled fuel passage”) 58 a on the low-temperature fuel electrode 68 side directly cooled by the refrigerant passage 60._A2Was 0.5 mm. Furthermore, the electrode area is 200 cm²The electrolyte membranes 46 and 66 were perfluoro-based solid polymer electrolyte membranes.
[0188]
A hydrogen gas containing steam having a dew point of 90 ° C. was supplied to the fuel electrode side of the obtained stacked fuel cell 40 at a pressure of 0.2 MPa and a flow rate corresponding to a hydrogen utilization of 80%. Air containing water vapor having a dew point of 80 ° C. was supplied to the air electrode side at a pressure of 0.2 MPa and a flow rate corresponding to an oxygen utilization rate of 20%. Further, cooling water having a water temperature of 80 ° C. was supplied to the refrigerant channels 60 provided in every other cell. Next, the stacked fuel cell 40 was set at 1.0 A / cm.²Was discharged under a constant current density condition, and the cathode temperature and cell voltage of each cell were measured.
[0189]
(Comparative Example 1)
Groove depth D of cooling air passage 54c_C1And the depth D of the groove of the uncooled air passage 56c_C2Was changed to 0.45 mm, and a stacked fuel cell having the same structure as in Example 1 was manufactured, and the discharge characteristics were examined under the same conditions as in Example 1.
[0190]
The results obtained in Example 1 and Comparative Example 2 are shown in FIGS. 20 and 21, respectively. Groove depth D of cooling air passage 54c_C1And the depth D of the groove of the uncooled air passage 56c_C2In the comparative example 1 in which both were set to 0.45 mm, as shown in FIG. 21, the cathode temperature was 82 ° C. at the low-temperature air electrode 50 adjacent to the cooling air passage 54 c and the The temperature reached 98 ° C. at the air electrode 70, and a temperature difference of 16 ° C. occurred in the cathode temperature according to the distance from the coolant channel 60.
[0191]
The cell voltage of the unit cell 44 having a low cathode temperature was 0.60 V, whereas the cell voltage of the unit cell 45 having a high cathode temperature was reduced to 0.40 V. This is because the dry-up occurred in the unit cells 45 because the slightly dry air containing water vapor having a dew point of 80 ° C. was uniformly sent to all the units having different cathode temperatures.
[0192]
On the other hand, the depth D of the groove of the uncooled air passage 56c_C2Is the depth D of the groove of the cooling air passage 54c._C1As shown in FIG. 20, the temperature distribution in Example 1 was almost the same as that in Comparative Example 1, but the cell voltage of the single cell 45 having a high cathode temperature was improved to 0.58 V. As a result, The total voltage of the entire stacked fuel cell has been improved. This is because the cross-sectional area of the uncooled air passage 56c is small, so that the air flow rate of the uncooled air passage 56c is reduced, and the dry-up of the cell 45 is suppressed.
[0193]
(Example 2)
A stacked fuel cell 74 having the structure shown in FIG. 2 was manufactured, and its discharge characteristics were examined. That is, a porous body 78 that obstructs gas flow is provided at the entrance of the uncooled air passage 56c to form a unit module 76, and 25 of these are stacked to form a stacked fuel cell 74 (the number of stacked unit cells = 50 cells). And
[0194]
The depth D of the groove of the cooling air passage 54c_C1And the depth D of the groove of the uncooled air passage 56c_C2Was set to 0.45 mm. In other respects, the structure of the unit module 74 is the same as that of the first embodiment. The discharge characteristics of the obtained stacked fuel cell 74 were examined under the same conditions as in Example 1. The results are shown in FIG.
[0195]
In Example 2 in which the porous body 78 was provided in the non-cooled air passage 56c, the distribution of the cathode temperature was almost the same as that in Comparative Example 1, but the cell voltage was 0.60 V for the unit cell 44 having a low cathode temperature, The voltage was 0.58 V for the unit cell 45 having a higher temperature, and the cell voltage of the unit cell 45 was improved as compared with Comparative Example 1. This is because the flow resistance of the non-cooled air flow path 56c was increased by the porous body 78, so that the air flow rate of the non-cooled air flow path 56c was reduced, and the dry-up of the cell 45 was suppressed.
[0196]
(Example 3)
A stacked fuel cell 80 having the structure shown in FIG. 3 was manufactured, and its discharge characteristics were examined. That is, a unit plate 82 is provided by providing an obstacle plate 84 at the entrance of the non-cooled air flow path 56c, which is an obstacle to gas flow. Cell). In other respects, the structure of the unit module 82 was the same as that of the second embodiment.
[0197]
A hydrogen gas containing steam having a dew point of 90 ° C. was supplied to the fuel electrode side of the obtained stacked fuel cell 80 at a pressure of 0.2 MPa and a flow rate corresponding to a hydrogen utilization of 80%. Air containing water vapor having a dew point of 90 ° C. was supplied to the air electrode side at a pressure of 0.2 MPa and a flow rate corresponding to an oxygen utilization of 20%. Further, cooling water having a water temperature of 80 ° C. was supplied to the refrigerant channels 60 provided in every other cell. Next, the stacked fuel cell 80 was set at 1.0 A / cm.²Was discharged under a constant current density condition, and the cathode temperature and cell voltage of each cell were measured.
[0198]
(Comparative Example 2)
Using a stacked fuel cell having the same structure as in Comparative Example 1, discharge characteristics were examined under the same conditions as in Example 3.
[0199]
The results obtained in Example 3 and Comparative Example 2 are shown in FIGS. 23 and 24, respectively. As shown in FIG. 24, in Comparative Example 2 in which the depth of the groove of the air flow path was the same and wet air containing water vapor having a dew point of 90 ° C. was supplied to the air flow path, the cathode temperature was lower than the low-temperature air electrode 50. And the hot air electrode 70 at 98 ° C.
[0200]
The cell voltage of the unit cell 45 having a high cathode temperature was 0.60 V, whereas the cell voltage of the unit cell 44 having a low cathode temperature was reduced to 0.20 V. This is because flooding occurred in the unit cells 44 because wet air containing water vapor having a dew point of 90 ° C. was uniformly sent to all the units having different cathode temperatures.
[0201]
On the other hand, in the third embodiment in which the obstacle plate 84 is provided in the non-cooled air passage 56c, as shown in FIG. The cell voltage of No. 44 improved to 0.58V. This is because the flow resistance of the non-cooling air flow path 56c is increased by the obstacle plate 84 provided on the entrance side, so that the air flow rate of the cooling air flow path 54c increases, and flooding of the cell 44 is suppressed. It is because.
[0202]
(Example 4)
A stacked fuel cell 86 having the structure shown in FIG. 4 was manufactured, and its discharge characteristics were examined. That is, a protrusion 56d is provided at the outlet of the non-cooling air flow channel 56c, and a protrusion 54d is provided at the inlet of the cooling air flow channel 54c to form a unit module 88. (The number of stacked layers = 50 cells). In other respects, the structure of the unit module 88 is the same as that of the second embodiment.
[0203]
A hydrogen gas containing steam having a dew point of 90 ° C. was supplied to the fuel electrode side of the obtained stacked fuel cell 86 at a pressure of 0.2 MPa and a flow rate corresponding to a hydrogen utilization of 80%. Air containing water vapor having a dew point of 90 ° C. was supplied to the air electrode side at a flow rate corresponding to an oxygen utilization rate of 20%. Further, cooling water having a water temperature of 80 ° C. was supplied to the refrigerant channels 60 provided in every other cell. Next, the stacked fuel cell 86 was set at 1.0 A / cm²Was discharged under a constant current density condition, and the cathode temperature and cell voltage of each cell were measured. The results are shown in FIG.
[0204]
When the gas output pressure of the air electrode was adjusted to 0.13 MPa, the air pressure in the cell was 0.2 MPa on the high temperature air electrode 70 side and 0.13 MPa on the low temperature air electrode 50 side. This is because a pressure loss of about 0.07 MPa occurred at the protrusions 54d and 56d provided at the outlet and the inlet of the air flow path. The cathode temperature on the low-temperature air electrode 50 side was 82 ° C., and the cathode temperature on the high-temperature air electrode 70 side was 98 ° C., and the temperature distribution was almost the same as in Comparative Example 2.
[0205]
However, the cell voltage was 0.54 V for the unit cell 45 having a high cathode temperature, and 0.52 V for the unit cell 44 having a low cathode temperature. The output of the whole battery 86 was improved. This is because flooding in the unit cell 44 was suppressed because the internal pressure of the cooling air passage 54c was lower than that in Comparative Example 2.
[0206]
(Example 5)
A stacked fuel cell in which unit cells having different electrode structures were stacked was fabricated, and discharge characteristics were examined. That is, two unit cells were stacked to form a unit module, and 25 unit cells were stacked to form a stacked fuel cell (the number of stacked unit cells = 50 cells). The average pore diameter of the diffusion layer of the high-temperature air electrode was about 0.1 μm, and the average pore diameter of the diffusion layer of the low-temperature air electrode was about 1 μm.
[0207]
In other respects, the structure of the unit module was the same as that of the second embodiment. The discharge characteristics of the obtained stacked fuel cell were examined under the same conditions as in Example 1.
[0208]
(Comparative Example 3)
A stacked fuel cell having the same structure as in Example 5 was prepared except that the average pore diameter of the diffusion layers of all the air electrodes was about 1 μm, and the discharge characteristics were examined under the same conditions as in Example 5.
[0209]
The results obtained in Example 5 and Comparative Example 3 are shown in FIGS. 26 and 27. In Comparative Example 3 in which the average pore diameter of the diffusion layers of all the air electrodes was 1 μm, as shown in FIG. 27, the cathode temperature was 82 ° C. on the cooling air electrode 54c side and 98 ° C. on the non-cooling air electrode 56c side. Was. The cell voltage was 0.60 V for a single cell having a low cathode temperature, and 0.40 V for a single cell having a high cathode temperature. This is because air containing steam having a dew point of 80 ° C. was evenly distributed to the air electrode having the same average pore diameter of the diffusion layer, and thus dry-up occurred in a single cell having a high cathode temperature.
[0210]
On the other hand, in Example 5 in which the average pore diameter of the diffusion layer of the high-temperature air electrode was 0.1 μm, as shown in FIG. 26, the distribution of the cathode temperature was equivalent to that of Comparative Example 3, but the cathode temperature was higher. The cell voltage of the unit cell was improved to 0.52V. This is because the average pore diameter of the diffusion layer of the high-temperature air electrode was reduced, so that the amount of water taken out of the electrolyte membrane was reduced, and dry-up was suppressed.
[0211]
(Example 6)
A stacked fuel cell 90 having the structure shown in FIG. 5 was manufactured, and its discharge characteristics were examined. That is, two unit cells having different groove depths of the fuel flow path were stacked to form a unit module 92, and 25 of these were stacked to form a stacked fuel cell 90 (the number of stacked unit cells = 50 cells).
[0212]
Here, the depth D of the groove of the cooling fuel passage 58a_A2Is 0.5 mm, and the depth D of the groove of the uncooled fuel passage 56a is_A1Was 0.4 mm. Further, the depth D of the groove of the cooling air passage 54a_C1And the depth D of the groove of the uncooled air passage 56c_C2Was 0.5 mm. Furthermore, the electrode area is 200 cm²The electrolyte membranes 46 and 66 were perfluoro-based solid polymer electrolyte membranes.
[0213]
A hydrogen gas containing water vapor having a dew point of 85 ° C. was supplied to the fuel electrode side of the obtained stacked fuel cell 90 at a pressure of 0.2 MPa and a flow rate corresponding to a hydrogen utilization of 80%. Air containing water vapor having a dew point of 85 ° C. was supplied to the air electrode side at a pressure of 0.2 MPa and a flow rate corresponding to an oxygen utilization of 20%. Further, cooling water having a water temperature of 80 ° C. was supplied to the refrigerant channels 60 provided in every other cell. Next, the stacked fuel cell 90 was set at 1.0 A / cm.²Under a constant current density condition, and the anode temperature and the cell voltage were measured.
[0214]
(Comparative Example 4)
Depth D of groove in uncooled fuel passage 56a_A1And the depth D of the groove of the cooling fuel passage 58a_A2Was made 0.45 mm, and a stacked fuel cell having the same structure as in Example 6 was produced, and the discharge characteristics were examined under the same conditions as in Example 6.
[0215]
The results obtained in Example 6 and Comparative Example 4 are shown in FIGS. 28 and 29, respectively. In Comparative Example 4 in which the depth of the groove of the fuel flow path was the same and hydrogen gas containing water vapor having a dew point of 85 ° C. was uniformly distributed to each fuel flow path, as shown in FIG. The temperature was 81 ° C on the 68 side and 95 ° C on the high temperature fuel electrode 48 side. The cell voltage was 0.62 V for the unit cell 45 having a low anode temperature and 0.40 V for the unit cell 44 having a high anode temperature. This is because dry-up occurred in the cell 44 because hydrogen gas containing water vapor having a dew point of 85 ° C. was uniformly distributed to all fuel electrodes having different anode temperatures.
[0216]
On the other hand, the depth D of the groove of the uncooled fuel passage 56a_A128, the temperature distribution is almost the same as that of Comparative Example 4 as shown in FIG. 28, but the cell voltage of the unit cell 44 having a high anode temperature was improved to 0.55V. This is because the cross-sectional area of the uncooled fuel flow channel 56a is large, so that the fuel flow rate on the high-temperature fuel electrode 48 side is increased, and the dry-up of the cell 44 is suppressed.
[0217]
(Example 7)
A stacked fuel cell 94 having the structure shown in FIG. 6 was manufactured, and its discharge characteristics were examined. That is, a protrusion 56f is provided at the outlet of the non-cooled fuel passage 56a, and a protrusion 58f is provided at the inlet of the cooled fuel passage 58a to form a unit module 96. (The number of stacked layers = 50 cells).
[0218]
In addition, the depth D of the groove of the uncooled fuel passage 56a_A1And the depth D of the groove of the cooling fuel passage 58a_A2Were 0.45 mm in all cases, and the other points related to the structure of the unit module 96 were the same as those in Example 6.
[0219]
A hydrogen gas containing water vapor having a dew point of 90 ° C. was supplied to the fuel electrode side of the obtained stacked fuel cell 94 at a flow rate corresponding to a hydrogen utilization rate of 80%. Air containing water vapor having a dew point of 80 ° C. was supplied to the air electrode side at a pressure of 0.2 MPa and a flow rate corresponding to an oxygen utilization rate of 20%. Further, cooling water having a water temperature of 80 ° C. was supplied to the refrigerant channels provided in every other cell. Next, the stacked fuel cell 94 was set at 1.0 A / cm²Under a constant current density condition, and the anode temperature and the cell voltage were measured. The results are shown in FIG.
[0220]
When the fuel electrode output gas pressure was adjusted to 0.20 MPa, the fuel gas pressure in the cell became 0.25 MPa on the high temperature fuel electrode 48 side and 0.2 MPa on the low temperature fuel electrode 68 side. This is because a pressure loss of about 0.05 MPa occurred at the protrusions 56f and 58f provided at the outlet and the inlet of the fuel flow path. The cathode temperature on the low-temperature fuel electrode 68 side was 81 ° C., and the cathode temperature on the high-temperature fuel electrode 48 side was 95 ° C., and the temperature distribution was almost the same as in Comparative Example 4.
[0221]
However, the cell voltage was 0.62 V for the unit cell 45 having a low anode temperature and 0.58 V for the unit cell 44 having a high anode temperature, and the cell voltage of the unit cell 44 having a high anode temperature was lower than that of Comparative Example 4. Improved. This is because the internal pressure of the non-cooled fuel passage 56a increased, so that the amount of water taken out of the electrolyte membrane was reduced, and the dry-up in the cell 44 was suppressed.
[0222]
From the above results, in a stacked fuel cell in which a coolant channel is provided every time several cells are stacked, if the gas channel structure or the electrode structure is changed according to the temperature environment of each cell, 1 Even when the fuel gas and the air are distributed by using one reaction gas supply system, a decrease in the cell voltage due to dry-up or flooding of the electrolyte membrane is suppressed, and the total voltage of the stacked fuel cell is improved. I understand.
[0223]
As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.
[0224]
For example, in the above embodiment, the gas flow path structure or the electrode structure on either the air electrode side or the fuel electrode side is changed according to the temperature environment, but the various embodiments described above are combined with each other, The gas flow path structure and the electrode structure on both the air electrode side and the fuel electrode side may be changed according to the temperature environment.
[0225]
Further, in the fuel cell system according to the present invention, since the flow rate, pressure, and humidification amount of the reaction gas are individually controlled for each cell group having a different temperature environment, the gas passage structure and the electrode structure of each cell are controlled. May be the same, but a stacked fuel cell in which the gas flow path structure and / or the electrode structure are changed according to the temperature environment may be used.
[0226]
When such a stacked fuel cell is incorporated in the fuel cell system according to the present invention, the load on the humidification amount control device 106 and the reaction gas supply control device 108 is reduced, so that control of the flow rate of the reaction gas and the like is further facilitated. can do.
[0227]
Further, in the fuel cell system described in the above embodiment, a stacked fuel cell provided with a cooling means is used every time two unit cells are stacked, but every time three or more unit cells are stacked. A stacked fuel cell provided with cooling means may be used.
[0228]
In this case, if the fuel cell system is provided with three or more fuel humidification control devices, air humidification control devices, fuel gas supply control devices, and air supply control devices, each cell group having a different temperature environment can be provided. In addition, it is possible to optimize the flow rate, the pressure, and the humidification amount of the reaction gas, whereby the same effects as in the above embodiment can be obtained.
[0229]
【The invention's effect】
In the operation method of the stacked fuel cell according to the present invention, the flow rate, the pressure, and / or the humidification amount of the reaction gas supplied to and / or discharged from each cell are changed for each cell. Therefore, even when a temperature distribution occurs in the stacking direction of the unit cells, there is an effect that variation in cell voltage due to dry-up or flooding can be reduced. This also has the effect of increasing the output of the entire stacked fuel cell.
[0230]
In addition, the stacked fuel cell according to the present invention has a gas flow path structure for each unit cell such that the amount of water supplied to each unit cell and the amount of moisture discharged from each unit cell are balanced for each unit cell. And / or the electrode structure is changed, so that even when fuel gas and air are distributed to each cell via one fuel manifold and air manifold, the gas flow rate, pressure, Alternatively, there is an effect that the amount of water vapor discharged from the unit cells can be individually controlled.
[0231]
In addition, this makes it possible to reduce variations in cell voltage due to dry-up or flooding, thereby improving the output of the entire stacked fuel cell. Moreover, since the energy efficiency of the stacked fuel cell can be improved without increasing the number of cooling means, the output per unit volume does not decrease.
[0232]
In addition, the fuel cell system according to the present invention includes a detecting unit that individually detects an operating state for each unit cell or unit cell included in the stacked fuel cell, and each unit based on the operating state detected by the detecting unit. Control means for individually controlling the flow rate, pressure, or humidification amount of the reaction gas supplied to the battery or each cell group, so that temperature distribution occurs in the stacking direction of the cells. In addition, it is possible to eliminate unevenness of the water balance of the electrolyte membrane of each cell and the relative excess and deficiency of the flow rate of the reaction gas.
[0233]
Therefore, it is possible to reduce the variation in the cell voltage of each unit cell, and to improve the output of the entire fuel cell system. Moreover, since the energy efficiency of the fuel cell system can be improved without increasing the number of cooling means, the output per unit volume does not decrease.
[0234]
As described above, according to the present invention, high output and high energy efficiency of the fuel cell can be achieved, and at the same time, the fuel cell can be downsized. If the invention is applied to the present invention, it contributes to increasing the output and weight of the automobile, etc., and is an invention having a great effect in industry.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view of a unit module serving as a basic structure of a stacked fuel cell according to a first embodiment of the present invention as viewed from a gas flow direction, and FIG. Is a sectional view taken along line AA ′ of FIG.
FIG. 2 is a cross-sectional view of a unit module serving as a basic structure of a stacked fuel cell according to a second embodiment of the present invention as seen from a direction perpendicular to a gas flow direction.
FIG. 3 is a cross-sectional view of a unit module serving as a basic structure of a stacked fuel cell according to a third embodiment of the present invention as viewed from a direction perpendicular to a gas flow direction.
FIG. 4 is a cross-sectional view as seen from a direction perpendicular to a gas flow direction of a unit module that is a basic structure of a stacked fuel cell according to a fourth embodiment of the present invention.
FIG. 5 is a cross-sectional view of a unit module serving as a basic structure of a stacked fuel cell according to a sixth embodiment of the present invention as seen from a direction perpendicular to a gas flow direction.
FIG. 6 is a cross-sectional view of a unit module serving as a basic structure of a stacked fuel cell according to a seventh embodiment of the present invention as viewed from a direction perpendicular to a gas flow direction.
FIG. 7 is a diagram illustrating a flow of water in a unit cell.
FIG. 8 (a) is a diagram showing a temperature distribution in a stacking direction generated in a conventional generally used stack type fuel cell provided with a refrigerant flow path every time two unit cells are stacked, and FIG. (B) is a cross-sectional view of a stacked fuel cell in which a coolant flow path is provided every time two unit cells are stacked, as viewed from the gas flow direction.
FIG. 9 (a) shows a stacked fuel cell having the structure shown in FIG. 8 (b) with a current density of 0.2 A / cm.²FIG. 9B is a diagram showing an anode temperature, a cathode temperature, and a cell voltage when the battery is discharged under the following conditions. FIG. 9B shows a current density of 1.0 A / cm.²FIG. 5 is a diagram showing an anode temperature, a cathode temperature, and a cell voltage when discharging is performed under the conditions described in FIG.
FIG. 10 (a) is a diagram showing a temperature distribution in a stacking direction generated in a conventional generally used stack type fuel cell having a coolant channel provided every time three unit cells are stacked, and FIG. (B) is a cross-sectional view of a stacked fuel cell in which a refrigerant flow path is provided every time three cells are stacked, as viewed from the gas flow direction.
11 shows a stacked fuel cell having the structure shown in FIG. 10 (b) having a current density of 1.0 A / cm.²FIG. 5 is a diagram showing an anode temperature, a cathode temperature, and a cell voltage when discharging is performed under the conditions described in FIG.
FIG. 12 is a block diagram showing a fuel cell system according to the present invention.
13 is a schematic configuration diagram showing an example of a stacked fuel cell used in the fuel cell system shown in FIG.
FIG. 14 is a perspective view showing an example of a stacked fuel cell used in the fuel cell system shown in FIG.
15 is a flowchart illustrating an example of an operation method of the fuel cell system illustrated in FIG.
16 is a flowchart showing another example of the method of operating the fuel cell system shown in FIG.
FIG. 17 is a flowchart showing another example of the method of operating the fuel cell system shown in FIG. 12;
FIG. 18 is a continuation of the flowchart shown in FIG. 17;
FIG. 19 is a continuation of the flowchart shown in FIG. 17;
FIG. 20 is a diagram showing a relationship between a cathode temperature and a cell voltage of a stacked fuel cell (Example 1) in which cells having different air flow paths having different cross-sectional areas are stacked.
FIG. 21 is a diagram showing a relationship between a cathode temperature and a cell voltage when dry air is supplied to a stacked fuel cell in which cells having the same cross-sectional area of an air flow path are stacked (Comparative Example 1).
FIG. 22 is a diagram showing a relationship between a cathode temperature and a cell voltage of a stacked fuel cell (Example 2) in which a porous body is provided at an inlet of an uncooled air flow path.
FIG. 23 is a diagram showing a relationship between a cathode temperature and a cell voltage in a stacked fuel cell (Example 3) in which an obstacle plate is provided at an inlet of an uncooled air flow path.
FIG. 24 is a diagram illustrating a relationship between a cathode temperature and a cell voltage when wet air is supplied to a stacked fuel cell in which unit cells having the same cross-sectional area of an air flow path are stacked (Comparative Example 2).
FIG. 25 is a diagram showing a relationship between a cathode temperature and a cell voltage of a stacked fuel cell (Example 4) in which projections are provided at an outlet of an uncooled air passage and an inlet of a cooled air passage.
FIG. 26 is a diagram showing a relationship between a cathode temperature and a cell voltage in a stacked fuel cell (Example 5) in which cells having different average pore diameters of a diffusion layer of an air electrode are stacked.
FIG. 27 is a diagram showing a relationship between a cathode temperature and a cell voltage of a stacked fuel cell (Comparative Example 3) in which cells having the same average pore diameter of the diffusion layer of the air electrode are stacked.
FIG. 28 is a diagram showing a relationship between a cathode temperature and a cell voltage in a stacked fuel cell (Example 6) in which unit cells having different fuel flow paths are stacked.
FIG. 29 is a diagram showing a relationship between a cathode temperature and a cell voltage when a fuel cell of a slightly dry state is supplied to a stacked fuel cell in which unit cells having the same fuel flow path are stacked (Comparative Example 4).
FIG. 30 is a diagram showing a relationship between a cathode temperature and a cell voltage of a stacked fuel cell (Example 7) in which projections are provided at an inlet of a non-cooled fuel passage and an outlet of a cooled fuel passage.
FIG. 31 is an exploded perspective view showing a unit cell as a basic structure of a fuel cell.
FIG. 32 is a perspective view showing a conventional stacked fuel cell generally used.
[Explanation of symbols]
40, 74, 80, 86, 90, 94 Stacked Fuel Cell
42, 76, 82, 88, 92, 96 unit module
44, 45 cells
54c Air flow path (cooling air flow path)
54d protrusion
56c air flow path (uncooled air flow path)
56d, 56f protrusion
56a Fuel flow path (uncooled fuel flow path)
58a Fuel flow path (cooling fuel flow path)
58f protrusion
60 refrigerant channel
78 porous body
84 Obstacle board
100 Fuel cell system
102 Stacked fuel cell
104 Reaction gas supply device
106 Humidification control device
108 Reaction gas supply control device
110 Battery operation status detection device

Claims (10)

Air electrode on one surface of the electrolyte, by joining a fuel electrode on the other surface, which a unit module unit cells are a plurality laminated was sandwiched with a separator having a gas channel, a cooling means disposed between the unit modules Wherein the amount of water supplied to each of the unit cells and the amount of water discharged from each of the unit cells are balanced for each of the unit cells. Each battery has a different gas channel structure and / or electrode structure,
Supply reaction gas of equal flow rate, pressure and humidification amount,
A method of operating a stacked fuel cell that distributes the reaction gas to each of the unit cells . An air electrode on one side of the electrolyte, a fuel electrode on the other side, and a unit module in which a plurality of cells are stacked, which are sandwiched between separators having a gas flow path ;
Cooling means disposed between the unit modules,
Wherein each cell, as the amount of water discharged from the water content and the respective unit cells to be supplied to the respective cells is balanced for each of the respective cells, different gas flow passage wherein each unit cell A stacked fuel cell having a structure and / or an electrode structure. The gas flow path structure is such that the air flow rate on the high-temperature air electrode side is smaller than the air flow rate on the low-temperature air electrode side,
The cross-sectional area of the air flow path on the high-temperature air electrode side is smaller than the cross-sectional area of the air flow path on the low-temperature air electrode side,
A porous body is provided at the inlet of the air flow path on the high-temperature air electrode side, and / or
The stacked fuel cell according to claim 2, wherein an obstacle plate is provided at an inlet of the air flow path on the high-temperature air electrode side . The gas flow path structure , the cross-sectional area of the fuel gas flow path on the high-temperature fuel electrode side, so that the fuel gas flow rate on the high-temperature fuel electrode side is greater than the fuel gas flow rate on the low-temperature fuel electrode side 3. The stacked fuel cell according to claim 2, wherein a cross-sectional area of the fuel passage is larger than a cross-sectional area of the fuel passage . The gas flow path structure, so that the pressure of the hot air electrode side is higher than the pressure of the low-temperature air electrode side, the hot air electrode side of the small comb cross-sectional area of the outlet side of the air passage, and said cold cathode 3. The stacked fuel cell according to claim 2, wherein the cross-sectional area of the inlet side of the side air flow path is reduced . The gas flow path structure is configured to reduce the cross-sectional area of the fuel gas flow path on the high-temperature fuel electrode side on the exit side so that the pressure on the high-temperature fuel electrode side is higher than the pressure on the low-temperature fuel electrode side, and 3. The stacked fuel cell according to claim 2, wherein the cross-sectional area on the inlet side of the fuel gas flow path on the side is reduced. The electrode structure is such that the air permeability of the hot air electrode is smaller than the air permeability of the cold air electrode,
The average pore size of the diffusion layer on the high temperature air electrode side is smaller than the average pore size of the diffusion layer on the low temperature air electrode side,
The thickness of the diffusion layer on the high-temperature air electrode side is larger than the thickness of the diffusion layer on the low-temperature air electrode side, and / or
3. The stacked fuel cell according to claim 2 , wherein the porosity of the diffusion layer on the high-temperature air electrode side is smaller than the porosity of the diffusion layer on the low-temperature air electrode side . A stacked type including a unit module in which a plurality of unit cells in which electrodes are joined to both surfaces of an electrolyte membrane and sandwiched by a separator having a gas flow path are stacked, and cooling means arranged between the unit modules A fuel cell,
A detection unit for detecting the voltage, the oxygen concentration in the gas discharged from the air flow path, and the hydrogen concentration in the gas discharged from the fuel flow path for each of the single cells or the group of the single cells,
A reaction gas supply unit for supplying a reaction gas having a different flow rate, pressure, and / or humidification amount for each unit cell or each unit cell group;
When the oxygen concentration of the low voltage cell or group of cells is lower than the oxygen concentration of the high voltage cell or group of cells, increasing the air flow rate of the low voltage cell or group of cells,
When the hydrogen concentration of the cell or group of cells having a low voltage is lower than the hydrogen concentration of the cell or group of cells having a high voltage, the fuel flow rate of the cell or group of cells having a low voltage is increased. And a control means for causing the fuel cell system to be stacked. A stacked type including a unit module in which a plurality of unit cells in which electrodes are joined to both surfaces of an electrolyte membrane and sandwiched by a separator having a gas flow path are stacked, and cooling means arranged between the unit modules A fuel cell,
  For each of the single cells or for each group of the single cells, voltage, and detection means for detecting film resistance,
  A reaction gas supply unit for supplying a reaction gas having a different flow rate, pressure, and / or humidification amount for each unit cell or each unit cell group;
  When the membrane resistance of the low voltage cell or group of cells is smaller than the membrane resistance of the high voltage cell or group of cells, increasing the air flow rate of the low voltage cell or group of cells, Reducing air humidification and / or reducing fuel humidification,
  When the membrane resistance of the low voltage cell or group of cells is greater than the membrane resistance of the high voltage cell or group of cells, the air flow rate of the low voltage cell or group of cells is reduced. Control means for increasing the amount of air humidification and / or increasing the amount of fuel humidification. A stacked type including a unit module in which a plurality of unit cells in which electrodes are joined to both surfaces of an electrolyte membrane and sandwiched by a separator having a gas flow path are stacked, and cooling means arranged between the unit modules A fuel cell,
  Detecting means for detecting a voltage for each of the unit cells or the group of unit cells; and supplying a reactant gas having a different flow rate, pressure and / or humidification amount to each unit cell or group of unit cells. Reacting gas supply means,
  The air flow rate or the fuel flow rate of the low-voltage cells or groups of cells is temporarily increased or decreased, and when the voltage of the low-voltage cells or the group of single cells increases due to the temporary increase or decrease, A stack-type fuel cell system comprising: control means for increasing or decreasing the air flow rate or fuel flow rate of a cell or a group of cells having a low voltage until the voltage of the group of cells or a group of cells no longer increases.

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