JP2006351252A - Deterioration diagnosis method of polymer electrolyte fuel cell - Google Patents
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本発明は、燃料電池、特に電解質として高分子を用いる固体高分子形燃料電池の劣化診断方法に関するものである。 The present invention relates to a method for diagnosing deterioration of a fuel cell, particularly a polymer electrolyte fuel cell using a polymer as an electrolyte.
近年の環境問題、特に自動車の排気ガスによる大気汚染や二酸化炭素による地球の温暖化問題に対して、クリーンな排気および高いエネルギー効率を有する電力源、あるいは動力源として燃料電池技術が注目されている。その中でも特に、作動温度が80℃程度で小型軽量化が可能である固体高分子形燃料電池(以下、PEFCと称する)に注目が集まっている。 Fuel cell technology is attracting attention as a power source or power source with clean exhaust and high energy efficiency against recent environmental problems, especially air pollution due to automobile exhaust gas and global warming due to carbon dioxide . In particular, attention has been focused on a polymer electrolyte fuel cell (hereinafter referred to as PEFC) that can be reduced in size and weight at an operating temperature of about 80 ° C.
PEFCは、通常単一セルを複数個積層して使用される。単一セルは高分子からなるイオン交換膜とその両側にそれぞれ燃料極と空気極を配置し、これを膜・電極接合体(以下、MEAと称する)として一体化している。この燃料極と空気極の外側に水素ガスや酸素ガス(空気)といった反応ガスの供給通路を兼ねているセパレータがあり、PEFCはMEAがセパレータによって狭持された構造となっている。また、セパレータは水素ガスや酸素ガスがイオン交換膜の全面に渡って一様に接触して流れるようにするため、複数の溝が彫ってある。 PEFC is usually used by laminating a plurality of single cells. In a single cell, a polymer ion exchange membrane and a fuel electrode and an air electrode are arranged on both sides thereof, and these are integrated as a membrane / electrode assembly (hereinafter referred to as MEA). A separator also serves as a reaction gas supply passage such as hydrogen gas or oxygen gas (air) outside the fuel electrode and the air electrode. The PEFC has a structure in which the MEA is held between the separators. In addition, the separator is engraved with a plurality of grooves so that hydrogen gas or oxygen gas flows uniformly in contact with the entire surface of the ion exchange membrane.
PEFCの発電の仕組みは次のとおりである。図1に示す通り、PEFCの単一セル11はイオン交換膜131と、その両側に相対向して設置された多孔性の燃料極134、空気極135と、該イオン交換膜131と各極134、135間にそれぞれ設置された触媒層132および拡散層133と、各極134、135の背面に設置されたセパレータ12から構成されている。セパレータ12は溝121を多数有し、その溝121を介してそれぞれ燃料ガス111および酸化剤ガス112を供給することにより、燃料極134の触媒層132上で燃料ガス(水素)が水素イオンと電子に分かれる。そして、水素イオンはイオン交換膜中131のクラスターを水と一体となって移動し、電子はセパレータ12を介して空気極135へ移動し、空気極135では酸素、電子および水素イオンが反応して水113が生成される。そしてそれぞれ燃料極134と空気極135で発生する起電力差により電力を得るものである。 The PEFC power generation mechanism is as follows. As shown in FIG. 1, a single cell 11 of PEFC includes an ion exchange membrane 131, a porous fuel electrode 134 and an air electrode 135 that are disposed opposite to each other, and the ion exchange membrane 131 and each electrode 134. , 135, respectively, and a separator layer 12 installed on the back surface of each electrode 134, 135. The separator 12 has a large number of grooves 121, and the fuel gas 111 and the oxidant gas 112 are supplied through the grooves 121, so that the fuel gas (hydrogen) is hydrogen ions and electrons on the catalyst layer 132 of the fuel electrode 134. Divided into Then, hydrogen ions move together with water in a cluster of 131 in the ion exchange membrane, and electrons move to the air electrode 135 through the separator 12, and oxygen, electrons, and hydrogen ions react in the air electrode 135. Water 113 is produced. Electric power is obtained by the difference in electromotive force generated between the fuel electrode 134 and the air electrode 135, respectively.
ところで、PEFCスタックまたはセルの性能低下の要因としては、水の供給不足による高分子電解質膜のイオン伝導性の低下による特性の低下が挙げられる。また、逆に、水の供給過多によって空気極側でガス拡散に必要な細孔の閉塞(フラッディングと呼ばれる)を生じやすく、酸素の拡散阻害による特性の劣化が挙げられる。PEFCの性能低下や特性の劣化を評価する方法として、電圧の測定や内部抵抗の測定などが行われている。 By the way, as a factor of the performance deterioration of the PEFC stack or the cell, there is a characteristic deterioration due to a decrease in ion conductivity of the polymer electrolyte membrane due to insufficient supply of water. Conversely, excessive supply of water is likely to cause clogging of pores (called flooding) necessary for gas diffusion on the air electrode side, resulting in deterioration of characteristics due to oxygen diffusion inhibition. As a method for evaluating performance degradation and characteristic degradation of PEFC, voltage measurement, internal resistance measurement, and the like are performed.
例えば、任意の個数直列に積層されたセルから構成されるブロックを複数個直列に積層して構成される燃料電池において、ブロック両端に接続され所定の電圧がかかると発光する発光素子と、発光素子と共にフォトカプラを構成する受光素子とを設けることによりブロックの電圧が閾値以下となったとき電圧が異状に低下したセルを判断するもの(特許文献1)や、正常発電時のPEFCのセルまたはスタックの交流インピーダンスを特定周波数について予め測定し、これをインピーダンス基準値およびインピーダンスの増加分を許容できる許容値を定め、これらの値を実際の値と比較して許容値を越えた場合、異状と判断する(特許文献2)などが行われている。 For example, in a fuel cell configured by stacking a plurality of blocks composed of an arbitrary number of cells stacked in series, a light emitting device that emits light when a predetermined voltage is applied to both ends of the block, and a light emitting device And a light receiving element that constitutes a photocoupler to determine a cell in which the voltage drops abnormally when the block voltage falls below a threshold (Patent Document 1), or a PEFC cell or stack during normal power generation AC impedance is measured in advance for a specific frequency, and the impedance reference value and an allowable value that can allow an increase in impedance are determined. When these values are compared with the actual value and exceeded the allowable value, it is judged abnormal. (Patent Document 2) and the like are performed.
しかしながら、特許文献1、2に示される診断方法では燃料電池全体の電池電圧や内部抵抗を測定し異常を検知するので、検知後は燃料電池全体を交換せざるを得ず、健全な単一セルも交換することとなり無駄を生じる。このことを防止する為に単一セルの全ての電池電圧や内部抵抗を測定する事は可能であるが、その場合は測定対象が膨大となり煩わしい問題がある。また、異常が劣化によるものであるかを診断することは出来なかった。PEFCは電解質膜(イオン交換膜)中に水がないと水素イオンの輸送ができず、発電できない。そのため、燃料や酸化剤を加湿して運転しており、空気極の還元反応により水が生成される。しかし、PEFC中の水分が過剰となると、水がガスの流路に溜まり、ガスの流れをせき止め、電圧が低下する(フラッディングと呼ぶ)。また、内圧の上昇により水が燃料電池内から押し出されると、セル電圧が回復する。この時、電圧が低下しても必ずしも内部抵抗が上がるとは限らない。 However, in the diagnostic methods disclosed in Patent Documents 1 and 2, since the battery voltage and internal resistance of the entire fuel cell are measured to detect an abnormality, the entire fuel cell must be replaced after detection. Will also be replaced, resulting in waste. In order to prevent this, it is possible to measure all the battery voltages and internal resistances of a single cell. Moreover, it was not possible to diagnose whether the abnormality was due to deterioration. PEFC cannot transport hydrogen ions without power in the electrolyte membrane (ion exchange membrane) and cannot generate electricity. Therefore, the fuel and the oxidant are operated with humidification, and water is generated by the reduction reaction of the air electrode. However, when the moisture in the PEFC becomes excessive, water accumulates in the gas flow path, stops the gas flow, and the voltage decreases (referred to as flooding). Further, when water is pushed out of the fuel cell due to an increase in internal pressure, the cell voltage is recovered. At this time, even if the voltage decreases, the internal resistance does not necessarily increase.
このような背景の下、PEFCの内部抵抗とI-V特性を測定することにより正確な劣化診断を行い、測定対象数の抑えられたPEFCの劣化診断装置の改良が望まれている。 Under such a background, it is desired to improve the PEFC deterioration diagnosis apparatus in which the accurate deterioration diagnosis is performed by measuring the internal resistance and IV characteristics of the PEFC, and the number of objects to be measured is suppressed.
本発明は、燃料極と空気極と前記燃料極と前記空気極との間に配設されたイオン交換膜からなる高分子電解質膜とを有する固体高分子形燃料電池において、燃料ガス供給路の末端部分の単一セルを集中して劣化診断することを特徴とするものである。 The present invention relates to a solid polymer fuel cell having a fuel electrode, an air electrode, and a polymer electrolyte membrane comprising an ion exchange membrane disposed between the fuel electrode and the air electrode. It is characterized by diagnosing deterioration by concentrating a single cell at the end portion.
また、燃料電池セルの性能低下を内部抵抗およびI−V特性により検知することを特徴とするものである。 Moreover, the performance fall of a fuel cell is detected by internal resistance and IV characteristic.
また、燃料電池セルの性能低下を検知後、燃料、酸化剤の供給圧力を上げることで性能低下を回復させ、回復しない場合は劣化と診断し新規セルと交換することを特徴とするものである。 In addition, after detecting the degradation of the performance of the fuel cell, the degradation of the performance is recovered by increasing the supply pressure of the fuel and the oxidant, and when it does not recover, the degradation is diagnosed and replaced with a new cell. .
本発明では燃料ガスの供給路の入口から最も遠い単一セル(末端部付近)が顕著に劣化することに着目し、燃料電池の末端部付近の単一セルの劣化を集中的に劣化診断することにより、測定対象の数を抑えながら、正確な劣化診断が可能な固体高分子形燃料電池の劣化診断装置を提供することができる。 In the present invention, focusing on the deterioration of a single cell (near the end) farthest from the inlet of the fuel gas supply path, the deterioration of the single cell near the end of the fuel cell is intensively diagnosed. Thus, it is possible to provide a degradation diagnosis apparatus for a polymer electrolyte fuel cell capable of performing accurate degradation diagnosis while suppressing the number of measurement objects.
本発明の実施の形態を、図2〜4により説明する。なお、同一構成部品は同じ番号を付記する。 An embodiment of the present invention will be described with reference to FIGS. In addition, the same number is attached to the same component.
図2は、本発明一実施形態を示すPEFCの劣化診断装置の概略図である。1は図1に示す単一セルを幾つも積層して成る燃料電池スタック、2は圧力を調整するための圧力調整器、3は流量を測定するための流量測定機器である。4は燃料電池スタック1で発電した電力を交流に変換するためのインバータ、5は負荷である。6は単一セルごとの測定が可能な内部抵抗と電圧を測定するための測定装置、7は燃料ガスの供給路の末端部付近の圧力を測定するための圧力測定装置、8は内部抵抗および電圧測定・圧力測定により総合的に診断を行う劣化判定装置である。 FIG. 2 is a schematic diagram of a PEFC deterioration diagnosis apparatus showing an embodiment of the present invention. 1 is a fuel cell stack formed by stacking a number of single cells shown in FIG. 1, 2 is a pressure regulator for adjusting pressure, and 3 is a flow rate measuring device for measuring flow rate. 4 is an inverter for converting the electric power generated by the fuel cell stack 1 into an alternating current, and 5 is a load. 6 is a measuring device for measuring internal resistance and voltage that can be measured for each single cell, 7 is a pressure measuring device for measuring the pressure near the end of the fuel gas supply path, 8 is an internal resistance and It is a deterioration determination device that performs comprehensive diagnosis by measuring voltage and pressure.
この様に構成されたPEFCスタック1は、矢示136の供給路に従い燃料ガスである水素ガスが圧力調整器2、流量測定機器3を介してPEFCスタック1に供給される。一方酸化剤ガスとしての空気が矢示137の供給路で供給されることにより発電が行われる。本発明で酸化剤ガス135は空気を用い自然吸気とした。燃料ガスは圧力調整器2および流量測定器3により一定に供されている。そして、PEFCスタック1で発電された電力は直流であるので、負荷5が交流負荷の場合はインバータ4により電力を変換して使用する。 In the PEFC stack 1 configured as described above, hydrogen gas as a fuel gas is supplied to the PEFC stack 1 via the pressure regulator 2 and the flow rate measuring device 3 according to the supply path indicated by the arrow 136. On the other hand, power is generated by supplying air as an oxidant gas through the supply path indicated by an arrow 137. In the present invention, the oxidant gas 135 is air and is naturally aspirated. The fuel gas is constantly supplied by the pressure regulator 2 and the flow rate measuring device 3. And since the electric power generated by the PEFC stack 1 is a direct current, when the load 5 is an alternating current load, the inverter 4 converts the electric power and uses it.
PEFCスタック1の劣化診断は、内部抵抗測定装置および電圧測定装置6、圧力測定装置7および劣化判定装置8の3つより行う。内部抵抗測定および電圧測定は、燃料ガス111の供給口から最も遠い場所(末端部付近)を集中して診断し、その他の場所に於いては飛び飛びに診断を行う。これは、供給路の末端部付近で燃料ガスが欠乏し、濃度分極により内部抵抗が増加するためPEFCスタックの末端部付近ほど劣化し易いからである。 The deterioration diagnosis of the PEFC stack 1 is performed by three of the internal resistance measurement device and voltage measurement device 6, the pressure measurement device 7, and the deterioration determination device 8. In the internal resistance measurement and the voltage measurement, a diagnosis is performed by concentrating the farthest location (near the end portion) from the supply port of the fuel gas 111, and in other locations, the diagnosis is performed. This is because the fuel gas is depleted in the vicinity of the end portion of the supply path, and the internal resistance increases due to concentration polarization, so that it is more likely to deteriorate near the end portion of the PEFC stack.
次に図3を参照して、劣化判定装置8が行うPEFCの劣化診断をフローチャートで説明する。本発明では、予め基準となる内部抵抗の正常値の範囲、劣化の基準となるI−V特性(図4参照)、スタックの燃料ガス供給路の末端付近の圧力、スタックの最大供給圧力を決めておく。内部抵抗の正常値の範囲は使用初期の単一セルの内部抵抗値の2〜3倍の値以下を正常値の範囲とした。I−V特性は使用初期におけるI−V特性を測定し、これより30%低下した値、即ち、ある特定の電流においてその電圧が使用初期の値の70%に低下した値を基準値とした。更に、燃料ガス供給路の末端付近の圧力は使用初期のPEFC定格運転時の圧力を基準値とし、末端付近のガス圧力がこれを下回らないように運転を行った。また、最大供給圧力は単一セルのイオン交換膜が耐えられ、且つPEFCを安全に運転できる圧力を基準値とした。そして測定装置6で被計測単一セルの内部抵抗と電圧を計測し、圧力測定装置7で末端付近のガス圧力を測定し、該ガス圧力が所定の圧力より高いか否かを判断し、高い場合は次ぎ単一セルの電圧が基準値を上回るか否かを判断し、上回る場合は次に内部抵抗値が正常値の範囲内か否かを判断して範囲内の場合PEFCは正常と判断する。 Next, the PEFC deterioration diagnosis performed by the deterioration determination device 8 will be described with reference to FIG. In the present invention, the range of the normal value of the internal resistance serving as a reference, the IV characteristic (see FIG. 4) serving as a reference for deterioration, the pressure near the end of the fuel gas supply path of the stack, and the maximum supply pressure of the stack are determined in advance. Keep it. The normal value range of the internal resistance was set to a value not more than 2 to 3 times the internal resistance value of the single cell in the initial stage of use. The IV characteristic was measured at the initial stage of use, and the reference value was a value that was 30% lower than this, that is, a value at which the voltage dropped to 70% of the initial value at a specific current. . Further, the pressure near the end of the fuel gas supply passage was set so that the pressure at the PEFC rated operation in the initial stage of use was a reference value, and the operation was performed so that the gas pressure near the end did not fall below this. Further, the maximum supply pressure was set to a pressure that can withstand the ion exchange membrane of a single cell and can safely operate the PEFC. The measuring device 6 measures the internal resistance and voltage of the single cell to be measured, the pressure measuring device 7 measures the gas pressure near the end, determines whether the gas pressure is higher than a predetermined pressure, and is high. Next, it is determined whether or not the voltage of a single cell exceeds the reference value. If it is higher, then it is determined whether or not the internal resistance value is within the normal value range. If it is within the range, the PEFC is determined to be normal. To do.
一方、圧力が低い場合、電圧が低い場合および内部抵抗が範囲外である場合のいずれかである場合は、燃料ガスの供給圧力が限界圧力である最大供給圧力であるか否かを判断し、最大供給圧力でない場合は最大供給圧力に上げて、再び圧力と電圧と内部抵抗を計測判断し、いずれも正常の場合は燃料ガスの供給圧力を元に戻して計測判断を繰り返す。
最大供給圧力に上げても電圧が低いか内部抵抗が範囲外である場合は劣化と判断する。
On the other hand, when the pressure is low, the voltage is low, or the internal resistance is out of range, it is determined whether the supply pressure of the fuel gas is the maximum supply pressure, which is the limit pressure, If it is not the maximum supply pressure, the pressure is increased to the maximum supply pressure, and the pressure, voltage, and internal resistance are measured and judged again. If all are normal, the fuel gas supply pressure is restored to the original and the measurement judgment is repeated.
If the voltage is low or the internal resistance is outside the range even when the maximum supply pressure is raised, it is judged that the battery has deteriorated.
以下、本発明の実施例を図1〜7を用いて説明する。 Embodiments of the present invention will be described below with reference to FIGS.
本発明で用いたPEFCスタックは、定格運転12V/12W(連続運転時8W)のものを使用した。単一セル数は20枚であり、これらを積層することでPEFCスタックとした。単一セルの構造は、外形が円形で図1に示すようにイオン交換膜の両側に、触媒層と拡散層からなる燃料極と空気極を一体形成しMEAとし、溝付きのセバレータでMEAを狭持している。このPEFCスタックに供給する燃料ガスには水素ガスを使用し、円形の中央に先端が閉塞されたパイプにより水素ガスを供給し、図2に示す様に圧力調整器および流量測定器によりその圧力は0.07MPaとし、流量は約80ml/minとした。該パイプのセパレータが位置する部分にはその周囲に多数の孔を形成し、孔を介してセパレータに放射状に多数形成された溝内に水素ガスが供給される様にした。発電電力は連続運転時において約8Wであり、本実施例に於いてインバータは使用せず、負荷には直流負荷である電球を使用した。なお、セルの性能低下を認知した場合、ガスの圧力は圧力調整器によって制御される。この圧力調整器は、アナログ入力信号により圧力制御が可能となっており、セル性能が低下すると劣化判定装置からの入力信号が変化することで自動的に供給圧力が上がるようになっている。また、空気は水素ガス供給の溝とは反対側に多数水平に形成され自然供給されるようにした。 The PEFC stack used in the present invention was a rated operation of 12V / 12W (8W during continuous operation). The number of single cells is 20, and a PEFC stack is formed by stacking these cells. The structure of a single cell is circular, and as shown in FIG. 1, a fuel electrode and an air electrode composed of a catalyst layer and a diffusion layer are integrally formed on both sides of an ion exchange membrane to form an MEA. Hold it. Hydrogen gas is used as the fuel gas to be supplied to the PEFC stack, and hydrogen gas is supplied through a pipe whose tip is closed at the center of the circle. The pressure is adjusted by a pressure regulator and a flow meter as shown in FIG. The flow rate was 0.07 MPa, and the flow rate was about 80 ml / min. A large number of holes are formed around the portion of the pipe where the separator is located, and hydrogen gas is supplied into the grooves formed radially in the separator through the holes. The generated power is about 8 W during continuous operation. In this example, an inverter was not used, and a light bulb that was a DC load was used as the load. In addition, when recognizing that the performance of the cell is deteriorated, the pressure of the gas is controlled by the pressure regulator. This pressure regulator is capable of pressure control with an analog input signal, and when the cell performance deteriorates, the supply pressure automatically increases as the input signal from the deterioration determining device changes. In addition, a large number of air is horizontally formed on the side opposite to the groove for supplying hydrogen gas so as to be naturally supplied.
PEFCスタックの劣化診断は、PEFCスタックが定格動作をしている発電中に行った。劣化診断は、単一セルの内部抵抗、電圧、電流および燃料ガスの供給路であるパイプの末端部の圧力の測定により行った。なお、内部抵抗、電流および電圧の測定は燃料ガス供給の入口側の単一セルから4つおきに測定し、燃料ガス供給路の末端部付近の単一セルは末端の単一セルを含め連続する3つの単一セルを集中して測定し、合計7つの単一セルを測定した。なお、本発明において全単一セルの測定を行わなかったのは、燃料ガスの供給路の末端部付近が顕著に劣化することが確認されており、末端部付近の単一セルの測定を多数測定し集中して行った。 The deterioration diagnosis of the PEFC stack was performed during the power generation in which the PEFC stack is operating at rated power. The deterioration diagnosis was performed by measuring the internal resistance of a single cell, the voltage, the current, and the pressure at the end of the pipe that is the supply path of the fuel gas. The internal resistance, current and voltage are measured every four cells from the single cell on the inlet side of the fuel gas supply, and the single cell near the end of the fuel gas supply path is continuous including the single cell at the end. Three single cells were measured in a concentrated manner, and a total of seven single cells were measured. In the present invention, the measurement of all single cells was not performed because it was confirmed that the vicinity of the end of the fuel gas supply path was significantly deteriorated, and many measurements of a single cell near the end were performed. Measured and concentrated.
内部抵抗測定装置は、交流四端子法を用いて測定を行った。内部抵抗測定装置内には電流源および電圧計が内蔵されており、前者によりPEFCの被測定単一セルに一定の電流を流し、後者により各々の単一セル電圧を測定している。内部抵抗は、流した交流電流の値と電圧計で各々測定した単一セル電圧より算出した。また、圧力測定装置は、圧力センサーを用いることで圧力測定を行った。 The internal resistance measuring apparatus measured using the AC four-terminal method. A current source and a voltmeter are built in the internal resistance measuring device. A constant current is passed through a single measured cell of the PEFC by the former, and each single cell voltage is measured by the latter. The internal resistance was calculated from the value of the flowing alternating current and the single cell voltage measured with a voltmeter. Moreover, the pressure measuring device measured pressure by using a pressure sensor.
図4はPEFCのI−V特性曲線である。縦軸は単一セルの電圧、横軸は電流を示す。図示される様に流れる電流が大きくなるに従い電圧は低下することが分かる。図中実線は使用初期即ち新しいPEFCの特性曲線、点線は長期使用により劣化した時の特性曲線である。図からも明らかな如く、劣化により同一の電流でも電圧が大きく低下する。この特性を利用し劣化判断することが出来る。本実施例では使用初期、即ち実線の値より30%低下した値を劣化の基準値とした。 FIG. 4 is an IV characteristic curve of PEFC. The vertical axis represents the voltage of a single cell, and the horizontal axis represents the current. It can be seen that the voltage decreases as the flowing current increases as shown. In the figure, the solid line is the characteristic curve of the initial PEFC, that is, the new PEFC, and the dotted line is the characteristic curve when deteriorated by long-term use. As is apparent from the figure, the voltage drops greatly even with the same current due to deterioration. Degradation can be determined using this characteristic. In this embodiment, the initial value of use, that is, a value that is 30% lower than the solid line value is used as the reference value for deterioration.
図5はPEFCの燃料ガスの供給路の入口側の単一セルと末端部の単一セルの電圧の経時変化を示したものである。燃料ガスの入口側単一セルに比べて末端部の単一セルは入口側の単一セルより早く電圧が低下することが分かる。これは、ガスの出口付近で燃料ガスが欠乏し、濃度分極により内部抵抗が増加することが原因と考えられる。また、長期間高温で運転することにより活性化分極が増大し、内部抵抗が増加することで出力電圧が低下していと考えられる。従って末端部の単一セルを測定することが有効であることが分かる。 FIG. 5 shows changes over time in the voltage of a single cell at the inlet side and a single cell at the end of the fuel gas supply path of PEFC. It can be seen that the voltage at the end single cell drops faster than the single cell at the inlet side compared to the single cell at the inlet side of the fuel gas. This is thought to be due to the lack of fuel gas near the gas outlet and an increase in internal resistance due to concentration polarization. Further, it is considered that the activation polarization increases by operating at a high temperature for a long period of time, and the output voltage decreases by increasing the internal resistance. Therefore, it can be seen that it is effective to measure a single cell at the end.
図6はPEFCスタックの単一セルごとの電圧を示す図で、縦軸に単一セル電圧、横軸に単一セル番号を示した。燃料ガス供給路の入口にある単一セルを番号1とし、末端にある単一セルをn(この場合は20)としたものである。実線で示す正常時においては、入口から最も遠い単一セル(末端の単一セル)の出力電圧は他と比べて若干低い程度であるが、劣化時においては出力電圧が他と比べて顕著に低下し、劣化していることが分かる。これは、上記したように内部抵抗の増加による出力電圧の低下が考えられる。 FIG. 6 is a diagram showing the voltage for each single cell of the PEFC stack, where the vertical axis indicates the single cell voltage and the horizontal axis indicates the single cell number. The single cell at the inlet of the fuel gas supply path is numbered 1 and the single cell at the end is designated n (20 in this case). In the normal state indicated by the solid line, the output voltage of the single cell farthest from the entrance (the single cell at the end) is slightly lower than the others, but the output voltage is significantly higher than the others when it is degraded. It turns out that it has fallen and it has deteriorated. As described above, it is conceivable that the output voltage decreases due to the increase in internal resistance.
図7は、燃料ガスの供給圧力を上げることで性能低下が回復することを示したI−V特性図である。点線で示す低圧時の供給ガスの圧力は0.06MPa、実線で示す高圧時の供給ガスの圧力は0.08MPaである。図7から分かるように、供給ガスの圧力を上げることで性能が回復した場合は、セルの劣化ではなくフラッディング等による一時的な内部抵抗の上昇または電圧の低下であると考えられる。しかし、PEFCスタックの最大供給圧力を加えても性能が回復しない場合は、PEFCセルの劣化と判断する。そして、劣化と判断されたPEFCの単一セルが末端部のみである場合は、末端部の単一セルのみを正常な単一セルと交換する。また、劣化と判断された単一セルが末端部以外の場合或いは末端部以外でも発生した場合はPEFC全体を交換する。 FIG. 7 is an IV characteristic diagram showing that the performance deterioration is recovered by increasing the supply pressure of the fuel gas. The pressure of the supply gas at low pressure indicated by a dotted line is 0.06 MPa, and the pressure of the supply gas at high pressure indicated by a solid line is 0.08 MPa. As can be seen from FIG. 7, when the performance is recovered by increasing the pressure of the supply gas, it is considered that the internal resistance is temporarily increased or the voltage is decreased due to flooding or the like, not cell deterioration. However, if the performance does not recover even when the maximum supply pressure of the PEFC stack is applied, it is determined that the PEFC cell is deteriorated. When the single cell of the PEFC determined to be degraded is only the terminal portion, only the single cell at the terminal portion is replaced with a normal single cell. In addition, when the single cell determined to be deteriorated is other than the end portion or is generated at the end portion, the entire PEFC is replaced.
なお、本発明で酸化剤ガスは空気を自然吸気にしたが、酸化剤に酸素ガスを用いた場合においても同様の結果が得られた。 In the present invention, the oxidant gas is naturally aspirated, but similar results were obtained when oxygen gas was used as the oxidant.
以上の結果より、燃料電池の供給路の末端部付近のセルの劣化を集中的に劣化診断することにより、測定対象の数を抑えることが可能である。また、ガス圧・セル電圧・内部抵抗の測定により正確な劣化診断が可能な固体高分子形燃料電池の劣化診断装置を提供することができる。 From the above results, it is possible to suppress the number of measurement objects by intensively diagnosing deterioration of cells near the end of the fuel cell supply path. In addition, it is possible to provide a degradation diagnosis apparatus for a polymer electrolyte fuel cell capable of performing accurate degradation diagnosis by measuring gas pressure, cell voltage, and internal resistance.
1 燃料電池
11 単セル
111 燃料ガス(水素ガス)
112 酸化剤ガス(空気または酸素ガス)
113 水
12 セパレータ
121 溝
13 MEA
131 イオン交換膜
132 触媒層
133 拡散層
134 燃料極
135 空気極
2 圧力調整器
3 流量測定装置
4 インバータ
5 負荷
6 内部抵抗測定装置および電圧測定装置(単セル)
7 圧力測定装置(燃料ガス出口付近)
8 劣化判定装置
1 Fuel cell 11 Single cell 111 Fuel gas (hydrogen gas)
112 Oxidant gas (air or oxygen gas)
113 Water 12 Separator 121 Groove 13 MEA
131 Ion Exchange Membrane 132 Catalyst Layer 133 Diffusion Layer 134 Fuel Electrode 135 Air Electrode 2 Pressure Regulator 3 Flow Rate Measuring Device 4 Inverter 5 Load 6 Internal Resistance Measuring Device and Voltage Measuring Device (Single Cell)
7 Pressure measuring device (near fuel gas outlet)
8 Degradation judgment device
Claims (3)
After detecting a decrease in performance based on the internal resistance or IV characteristics of the fuel cell, if the fuel gas supply pressure to the fuel electrode and the oxidant gas supply pressure to the oxygen electrode do not recover, the deterioration is diagnosed. 3. A method for diagnosing deterioration of a polymer electrolyte fuel cell according to claim 1 or 2.
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