POWER GENERATION CELL

In a power generation cell, cathode flow field grooves forming a gas flow field of a cathode separator arranged to face an MEA are formed of first cathode flow field grooves blocked on an outlet side and second cathode flow field grooves blocked on an inlet side. The first cathode flow field grooves and the second cathode flow field grooves are arranged adjacent to each other in the flow field width direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-003183 filed on Jan. 12, 2022, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a power generation cell of a fuel cell system.

Description of the Related Art

A fuel cell system is a power generation system that generates power by electrochemical reactions between a fuel gas such as hydrogen and an oxygen-containing gas such as air and does not discharge CO2. The fuel cell system may be mounted on a fuel cell vehicle or the like excellent in environmental performance. In addition, a regenerative fuel cell system using hydrogen and oxygen generated through energy storage by electrolysis of water can be used for output leveling of a solar power generation system or a wind power generation system having great fluctuations in output, and also contributes to expansion of use of sustainable renewable energy.

For example, JP 2019-117721 A discloses a structure of a power generation cell of a fuel cell system.

SUMMARY OF THE INVENTION

A conventional power generation cell has a problem in that water generated by electrochemical reactions is likely to be retained inside a membrane electrode assembly (MEA). Therefore, a power generation cell having excellent drainage performance is desired.

An object of the present invention is to solve the aforementioned problem.

An aspect of the disclosure is a power generation cell comprising a membrane electrode assembly, a cathode separator and an anode separator, the membrane electrode assembly including a electrolyte membrane and electrodes arranged on both sides of the electrolyte membrane, the membrane electrode assembly being sandwiched by the cathode separator and the anode separator, wherein the cathode separator comprises cathode line ridges that protrude from the cathode separator, contact the membrane electrode assembly and extend in a flow direction of the oxygen-containing gas, and a plurality of cathode flow field grooves that are formed between the cathode line ridges and form an oxygen-containing gas flow field, the plurality of cathode flow field grooves comprise a first cathode flow field groove that is blocked on a downstream side in the flow direction of the oxygen-containing gas, and a second cathode flow field groove that is blocked on an upstream side in the flow direction of the oxygen-containing gas, and the second flow field groove is arranged adjacent to the first flow field groove in the flow field width direction.

In the power generation cell of the above aspect, the first cathode flow field groove blocked on the downstream side in the flow direction of the oxygen-containing gas and the second cathode flow field groove blocked on the upstream side in the flow direction of the oxygen-containing gas are adjacent to each other in the flow field width direction. Thus, the oxygen-containing gas is caused to flow from the first cathode flow field groove toward the second cathode flow field groove in the membrane electrode assembly. The water generated in the membrane electrode assembly is efficiently removed not only by a passive process based on a water vapor diffusion process but also by an active process using a water transport phenomenon based on active fluid movement caused by the flow of the oxygen-containing gas. Therefore, the power generation cell is excellent in drainage performance, can prevent reaction inhibition due to flooding, and improves power generation efficiency.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A power generation cell10shown inFIG.1forms a unit fuel cell and includes a MEA12, a cathode separator14, and an anode separator16. The cathode separator14is a metallic or carbon separator disposed on the cathode side (the side in the arrow A2direction) of the MEA12. The anode separator16is a metallic or carbon separator disposed on the anode side (the side in the arrow A1direction) of the MEA12. Usually, a fuel cell system18includes a plurality of power generation cells10. The plurality of power generation cells10are stacked in the thickness direction in the fuel cell system18. The fuel cell system18may be mounted on a fuel cell vehicle. The fuel cell system18may alternatively be mounted as a regenerative fuel cell system in, for example, space equipment, underwater equipment, an output leveling device of a renewable power generation system, or the like.

The cathode separator14and the anode separator16, for example, are made of thin metal plates such as steel plates, stainless steel plates, aluminum plates, plated steel sheets, or metal plates having anti-corrosive surfaces produced by performing a surface treatment. The cathode separator14and the anode separator16are formed in wavy shapes by press molding. The cathode separator14and the anode separator16used in the fuel cell system18are integrally joined to form a joint separator20. The cathode separator14and the anode separator16forming the joint separator20belong to different power generation cells10adjacent to each other.

The power generation cell10has a rectangular planar shape. The power generation cell10has an oxygen-containing gas supply passage22a, a coolant supply passage24a, and a fuel gas discharge passage26bat one end of a long side (the end in the arrow B1direction). These passages pass through the cathode separator14and the anode separator16in the thickness direction. These passages communicate with the passages of other joint separator20and a resin frame member28disposed in the stacking direction (the arrow A direction), respectively, and form flow paths in the stacking direction (the arrow A direction).

The oxygen-containing gas supply passage22a, the coolant supply passage24a, and the fuel gas discharge passage26bare aligned along a short side (in the arrow C direction). An oxygen-containing gas is supplied through the oxygen-containing gas supply passage22a. In this specification, the oxygen-containing gas is air or pure oxygen gas. The oxygen-containing gas may include water vapor supplied through a humidifier and water vapor generated by electrode reactions.

In a preferred embodiment, pure oxygen at a relatively low pressure (for example, 0.1 to 1 MPa) is supplied as the oxygen-containing gas. In the conventional high current density type fuel cell, the pressure loss of the gas flow field is increased to blow off the generated water and prevent the generated water from being retained inside, whereas in the case of the low pressure pure oxygen, the pressure of the supplied gas is low, so that the lowering of the power generation efficiency due to the high pressure loss is not likely to occur. Further, because there is no partial pressure of nitrogen in the oxygen-containing gas, it is possible to increase the partial pressure of water vapor in the oxygen-containing gas, thereby improving the properties for discharging the generated water. A coolant, for example, water, is supplied through the coolant supply passage24a. A fuel gas is discharged through the fuel gas discharge passage26b. The fuel gas is a gas containing hydrogen as a main component. In a preferred embodiment, pure hydrogen gas is supplied as the fuel gas. The fuel gas may include water vapor generated by electrode reactions or the humidifier.

The power generation cell10has a fuel gas supply passage26a, a coolant discharge passage24b, and an oxygen-containing gas discharge passage22bat the other end of the long side (the end in the arrow B2direction). These passages pass through the cathode separator14and the anode separator16in the thickness direction. These passages communicate with the passages of other joint separator20and the resin frame member28disposed in the stacking direction (the arrow A direction), respectively, and form flow paths in the stacking direction (the arrow A direction).

The fuel gas supply passage26a, the coolant discharge passage24b, and the oxygen-containing gas discharge passage22bare aligned along the short side. The fuel gas is supplied through the fuel gas supply passage26a. The coolant is discharged through the coolant discharge passage24b. The oxygen-containing gas is discharged through the oxygen-containing gas discharge passage22b. The flow direction of the fuel gas is opposite to the flow direction of the oxygen-containing gas. The arrangement of the oxygen-containing gas supply passage22aand the oxygen-containing gas discharge passage22b, as well as the fuel gas supply passage26aand the fuel gas discharge passage26bis not limited to that shown for the present embodiment, and may be set appropriately depending on required specifications.

The MEA12includes a membrane electrode assembly (hereinafter referred to as a “MEA12a”) and the resin frame member28. The resin frame member28is a frame-shaped resin sheet joined to the outer peripheral portion of the MEA12a.

As shown inFIG.4, the MEA12aincludes an electrolyte membrane30, and a cathode32and an anode34sandwiching the electrolyte membrane30. The electrolyte membrane30, for example, is a solid polymer electrolyte membrane (cation exchange membrane). The solid polymer electrolyte membrane is formed by impregnating a thin membrane of perfluorosulfonic acid with water, for example. A fluorine based electrolyte may be used as the electrolyte membrane30. Alternatively, an HC (hydrocarbon) based electrolyte may be used as the electrolyte membrane30.

The cathode32includes a cathode catalyst layer32ajoined to one surface of the electrolyte membrane30, a first microporous layer32bstacked on the cathode catalyst layer32a, and a cathode diffusion layer32cstacked on the first microporous layer32b. The anode34includes an anode catalyst layer34ajoined to the other surface of the electrolyte membrane30, a second microporous layer34bstacked on the anode catalyst layer34a, and an anode diffusion layer34cstacked on the second microporous layer34b.

Each of the cathode catalyst layer32aand the anode catalyst layer34ais, for example, a layer mainly composed of porous carbon particles with platinum alloy supported on surfaces thereof. The first microporous layer32band the second microporous layer34bare layers mainly composed of water-repellent resins such as PTFE and conductive materials such as carbon black. The first microporous layer32band the second microporous layer34bmay be omitted from the power generation cell10. The cathode diffusion layer32cand the anode diffusion layer34care formed of carbon paper, carbon cloth, or the like.

As shown inFIG.1, at a marginal portion of the resin frame member28on the arrow B1side, the oxygen-containing gas supply passage22a, the coolant supply passage24a, and the fuel gas discharge passage26bare provided. At a marginal portion of the resin frame member28in the arrow B2direction, the fuel gas supply passage26a, the coolant discharge passage24b, and the oxygen-containing gas discharge passage22bare provided. The inner peripheral portion of the resin frame member28is joined to the outer peripheral portion of the MEA12awith an adhesive. The resin frame member28is made of a resin material having electrical insulation properties.

As shown inFIG.2, the cathode separator14has an oxygen-containing gas flow field36on a first surface14afacing the MEA12a. The oxygen-containing gas flow field36extends in the arrow B2direction which is the flowing direction of the oxygen-containing gas. The oxygen-containing gas flow field36includes a plurality of cathode line ridges38and a plurality of cathode flow field grooves40. The plurality of cathode line ridges38are arranged at regular intervals in the flow field width direction (the arrow C direction). The cathode flow field grooves40are formed between the plurality of cathode line ridges38. The plurality of cathode flow field grooves40and the plurality of cathode line ridges38are alternately arranged in the flow field width direction (the arrow C direction). The cathode line ridges38and the cathode flow field grooves40have a wavy shape extending along the long side (the arrow B direction) while meandering in the flow field width direction (the arrow C direction). The cathode line ridges38and the cathode flow field grooves40may have a linear shape.

The cathode flow field grooves40of the present embodiment include a plurality of first cathode flow field grooves42and a plurality of second cathode flow field grooves44. The first cathode flow field grooves42are in fluid communication with the oxygen-containing gas supply passage22a, and are separated from the oxygen-containing gas discharge passage22bby a protruding portion between the cathode line ridges38. As shown in the3A, the first cathode flow field groove42has a cathode inflow open end42a. The cathode inflow open end42ais located on the upstream side in the flowing direction of the oxygen-containing gas and is formed at an end close to the one end of the long side. The cathode inflow open end42ais open toward the oxygen-containing gas supply passage22a.

The cathode inflow open end42aallows the oxygen-containing gas to flow into the first cathode flow field groove42. As shown inFIG.3B, the first cathode flow field groove42has a cathode outflow blocked end42bthat blocks the first cathode flow field groove42at an end close to the other end of the long side. The cathode outflow blocked end42bis formed by the protruding portion of the cathode separator14. The protruding portion forming the cathode outflow blocked end42bis integrally connected to a pair of cathode line ridges38adjacent to each other in the flow field width direction. The cathode outflow blocked end42bprevents the oxygen-containing gas from flowing out from the downstream side of the first cathode flow field groove42toward the oxygen-containing gas discharge passage22b.

As shown inFIG.2, the second cathode flow field grooves44are in fluid communication with the oxygen-containing gas discharge passage22b, but are not in fluid communication with the oxygen-containing gas supply passage22a. As shown inFIG.3A, the second cathode flow field groove44has a cathode inflow blocked end44bthat blocks the upstream side of the oxygen-containing gas in the flowing direction. The cathode inflow blocked end44bis formed at the end close to the one end of the long side. The cathode inflow blocked end44bis formed by a protruding portion of the cathode separator14. The protruding portion forming the cathode inflow blocked end44bis integrally connected to a pair of cathode line ridges38adjacent to each other in the flow field width direction of the second cathode flow field groove44. The cathode inflow blocked end44bprevents the oxygen-containing gas from flowing from the oxygen-containing gas supply passage22ainto the second cathode flow field groove44on the upstream side.

The first cathode flow field grooves42and the second cathode flow field grooves44are connected to each other through the porous layers such as the gas diffusion layer, the microporous layer, and a dedicated porous layer provided beneath the cathode line ridges38. In the present embodiment, the porous layers are the first microporous layer32band the cathode diffusion layer32cstacked on the first microporous layer32b.

As shown inFIG.3B, the second cathode flow field groove44has a cathode outflow open end44a, which is open toward the oxygen-containing gas discharge passage22b, at an end close to the other end of the long side. The cathode outflow open end44aallows the oxygen-containing gas to flow out from the second cathode flow field groove44.

As shown inFIG.2, on the first surface14aof the cathode separator14, an inlet buffer portion46A is arranged between the oxygen-containing gas supply passage22aand the oxygen-containing gas flow field36. The inlet buffer portion46A has a plurality of bosses46a. The cathode separator14each have an outlet buffer portion46B between the oxygen-containing gas discharge passage22band the oxygen-containing gas flow field36. The outlet buffer portion46B has a plurality of bosses46b. The bosses46a,46bare dot-like protruding portions of the cathode separator14.

The first surface14aof the cathode separator14has a first seal line48. The first seal line48is a bead seal, bulges toward the resin frame member28, and abuts against the resin frame member28. The first seal line48is formed by press molding. The first seal line48includes passage bead portions50and an outer peripheral bead portion52. The passage bead portions50are bead seals each of which surrounds each of the plurality of passages (e.g., the oxygen-containing gas supply passage22aand so on). The outer peripheral bead portion52surrounds the outer periphery of the oxygen-containing gas flow field36and prevents the oxygen-containing gas from flowing out of the oxygen-containing gas flow field36.

Each passage bead portion50has a plurality of bridge portions54extending along the long side. The bridge portions54of the oxygen-containing gas supply passage22aand the bridge portions54of the oxygen-containing gas discharge passage22bextend toward the oxygen-containing gas flow field36. The passage bead portions50on the first surface14aof the cathode separator14prevent fluids other than the oxygen-containing gas from flowing into the oxygen-containing gas flow field36.

As shown inFIG.1, the anode separator16has a fuel gas flow field56extending in the arrow B direction on a first surface16afacing the MEA12. The fuel gas flow field56is in fluid communication with the fuel gas supply passage26aand the fuel gas discharge passage26b. The fuel gas flow field56has a plurality of wavy anode flow field grooves56bformed between a plurality of wavy anode line ridges56aextending in the arrow B direction, which is the flowing direction of the fuel gas. The anode flow field groove56bof the present embodiment does not have a blocked end. All the anode flow field grooves56bare in fluid communication with the fuel gas supply passage26aand the fuel gas discharge passage26b.

The anode separator16further includes an inlet buffer portion58A, an outlet buffer portion58B, and a second seal line60on the first surface16a. The inlet buffer portion58A is configured similarly to the inlet buffer portion46A of the cathode separator14. The outlet buffer portion58B is configured similarly to the outlet buffer portion46B of the cathode separator14. The second seal line60is configured similarly to the first seal line48of the cathode separator14.

A coolant flow field62is formed between the cathode separator14and the anode separator16forming the joint separator20. The coolant flow field62is connected to the coolant supply passage24aand the coolant discharge passage24b. The coolant flows through the coolant flow field62.

The power generation cell10of the present embodiment has the configuration described above. The power generation cell10of the present embodiment operates as explained blow.

As shown inFIG.4, the oxygen-containing gas is supplied to the cathode32of the MEA12athrough the first cathode flow field grooves42. The fuel gas is supplied to the anode34of the MEA12athrough the anode flow field grooves56b. The coolant flows through the coolant flow field62.

The fuel gas passes through the anode diffusion layer34cand the second microporous layer34band is converted into protons by electrochemical reactions in the anode catalyst layer34a. The protons move through the electrolyte membrane30and reach the cathode catalyst layer32a. The oxygen-containing gas passes through the cathode diffusion layer32cand the first microporous layer32band is supplied to the cathode catalyst layer32a. The protons and oxygen react in the cathode catalyst layer32aand generate water. Through the reactions in the cathode catalyst layer32aand the anode catalyst layer34a, charges are transferred between the cathode32and the anode34to generate electric power.

The water generated at the cathode32flows into the oxygen-containing gas flow field36through the first microporous layer32band the cathode diffusion layer32cas the porous layers, and is discharged from the power generation cell10together with the oxygen-containing gas.

In the present embodiment, the first cathode flow field grooves42whose downstream side in the flow direction of the oxygen-containing gas is blocked and the second cathode flow field grooves44whose upstream side in the flow direction of the oxygen-containing gas is blocked are adjacent to each other in the flow field width direction. Therefore, a pressure difference is created between the pressure of the oxygen-containing gas in the first cathode flow field groove42and the pressure of the oxygen-containing gas in the second cathode flow field groove44, so that a flow of the oxygen-containing gas is generated. That is, a flow of the oxygen-containing gas from the first cathode flow field groove42toward the second cathode flow field groove44as indicated by the arrows in the drawing is generated in the cathode diffusion layer32c. The water generated at the cathode32is likely to be retained at portions in contact with the cathode line ridges38(a portion of the cathode diffusion layer32csandwiched between the cathode line ridges38and the electrolyte membrane30). In the power generation cell10, the flow of the oxygen-containing gas is generated inside the cathode diffusion layer32c, and the generated water is discharged from the second cathode flow field grooves44without being retained.

As shown inFIG.4, the oxygen-containing gas flowing through the first cathode flow field grooves42is partly used in the power generation reactions, and the remaining portion of the oxygen-containing gas flows to the second cathode flow field grooves44through the cathode diffusion layer32cbeneath the cathode line ridges38. The water generated by the power generation reactions flows as water vapor through the second cathode flow field grooves44together with the oxygen-containing gas and is discharged from the power generation cell10.

As described above, because the power generation cell10can discharge the water generated inside the cathode32by using the active flow of the oxygen-containing gas, the power generation cell10has excellent drainage performance. Therefore, the power generation cell10can prevent power generation performance from being lowered due to flooding.

Second Embodiment

The power generation cell according to the second embodiment includes anode separator16A shown inFIG.6in place of the anode separator16in the power generation cell10according to the first embodiment. The fuel gas flow field56A of the anode separator16A has a drainage structure similar to that of the oxygen-containing gas flow field36of the cathode separator14(FIG.2). The anode separator16A of the present embodiment has the same structure as the anode separator16of the first embodiment except for the fuel gas flow field56A.

The fuel gas flow field56A of the anode separator16A has anode flow field grooves56bbetween the plurality of anode line ridges56a. The anode flow field grooves56binclude first anode flow field grooves64connected to the fuel gas supply passage26aand second anode flow field grooves66connected to the fuel gas discharge passage26b.

As shown in the drawing, the first anode flow field groove64has an anode inflow open end64a, which is open toward the fuel gas supply passage26a, at an end close to the other end of the long side. Although not particularly illustrated, the first anode flow field groove64has a first anode blocked end at an end close to the one end of the long side. The first anode blocked end blocks communication between the first anode flow field groove64and the fuel gas discharge passage26bby blocking the first anode flow field groove64.

As shown in the drawing, the second anode flow field groove66has an anode inflow blocked end66bat an end close to the other end of the long side. The anode inflow blocked end66bblocks communication between the second anode flow field groove66and the fuel gas supply passage26aby blocking the second anode flow field groove66. Although not particularly shown, the second anode flow field groove66has a second anode open end, which is open toward the fuel gas discharge passage26b, at an end close to the one end of the long side. The second anode open end allows the fuel gas to flow out from the second anode flow field groove66toward the fuel gas discharge passage26b.

The first anode flow field groove64whose downstream side in the flow direction of fuel gas is blocked and the second anode flow field groove66whose upstream side in the flow direction of fuel gas is blocked are adjacent to each other in the flow field width direction. Therefore, a flow of the fuel gas from the first anode flow field grooves64toward the second anode flow field grooves66is generated inside the anode diffusion layer34c(seeFIG.4) (a portion of the anode diffusion layer34csandwiched between the electrolyte membrane30and the anode line ridges56a). Therefore, the anode separator16A of the second embodiment promotes the discharge of the generated water from the anode34.

Third Embodiment

In the third embodiment, in the power generation cell10ofFIG.1, there is a difference between the flow field cross-sectional area of the first cathode flow field groove42and the flow field cross-sectional area of the second cathode flow field groove44. The first cathode flow field groove42and the second cathode flow field groove44can be schematically represented as shown inFIG.7.

Due to the properties of fluid, the internal pressure in a flow field generally becomes higher in a flow field having a smaller flow field cross-sectional area, and the internal pressure of the flow field decreases as the flow field cross-sectional area increases. Therefore, in the present embodiment, the flow field cross-sectional area of the first cathode flow field groove42is made smaller than the flow field cross-sectional area of the second cathode flow field groove44. Specifically, inFIG.7, the width of the first cathode flow field groove42is smaller than the width of the second cathode flow field groove44. Instead of the configuration in which the widths of these grooves have a magnitude relationship, the height (groove depth) of the first cathode flow field groove42may be smaller than the height (groove depth) of the second cathode flow field groove44. As described above, because the flow field cross-sectional area of the first cathode flow field groove42is smaller than the flow field cross-sectional area of the second cathode flow field groove44, the internal pressure in the first cathode flow field groove42further increases, and the internal pressure in the second cathode flow field groove44further decreases. In this way, the power generation cell10of the present embodiment can further increase the pressure difference between the first cathode flow field grooves42and the second cathode flow field grooves44. Therefore, the power generation cell10of the present embodiment can discharge the generated water more effectively. The magnitude relationship of the flow field cross-sectional areas described above may also be applied to the anode separator16A shown inFIG.6. That is, in the anode separator16A, the flow field cross-sectional area of the first anode flow field grooves64may be smaller than the flow field cross-sectional area of the second anode flow field grooves66.

Fourth Embodiment

In the fourth embodiment, the distribution of the flow field cross-sectional areas of the first cathode flow field groove42and the second cathode flow field groove44is modified in the power generation cell10ofFIG.1.

As shown inFIG.8A, because the first cathode flow field grooves42and the second cathode flow field grooves44respectively have an elongated shape with one end blocked, they are susceptible to flow resistance. Focusing on the first cathode flow field groove42, the oxygen-containing gas flows out to the cathode32while moving from the vicinity of the cathode inflow open end42ato the cathode outflow blocked end42b. Therefore, when the flow field cross-sectional area of the first cathode flow field groove42is constant in the gas flow direction, the pressure inside the first cathode flow field groove42tends to decrease toward the cathode outflow blocked end42b. On the other hand, focusing on the second cathode flow field groove44, when the flow field cross-sectional area of the second cathode flow field groove44is constant in the gas flow direction, the pressure in the vicinity of the cathode inflow blocked end44btends to be higher than the pressure in the vicinity of the cathode outflow open end44a.

The pressure distribution inside each of the first cathode flow field groove42and the second cathode flow field groove44as described above causes a variation in the pressure difference between the first cathode flow field groove42and the second cathode flow field groove44adjacent to each other, and there is a concern that water is likely to be locally retained at a certain area.

Therefore, as shown inFIGS.8B and8C, the heights (groove depths in the arrow A direction) of the first cathode flow field grooves42and the second cathode flow field grooves44are changed along the gas flow direction. As shown inFIG.8B, the depth of the first cathode flow field groove42gradually decreases from the cathode inflow open end42atoward the cathode outflow blocked end42b. Therefore, as shown inFIG.9A, the flow field cross-sectional area of the first cathode flow field groove42gradually decreases from the cathode inflow open end42atoward the cathode outflow blocked end42b. Such a distribution of the flow field cross-sectional area of the first cathode flow field groove42may be realized by gradually narrowing the width of the first cathode flow field groove42toward the cathode outflow blocked end42b.

As shown inFIG.8C, the depth of the second cathode flow field groove44gradually increases from the cathode inflow blocked end44btoward the cathode outflow open end44a. Therefore, as shown inFIG.9B, the flow field cross-sectional area of the second cathode flow field groove44gradually increases from the cathode inflow blocked end44btoward the cathode outflow open end44a. Such a distribution of the flow field cross-sectional area of the second cathode flow field groove44may be realized by gradually increasing the width of the second cathode flow field groove44toward the cathode outflow open end44a.

In the first cathode flow field groove42of the fourth embodiment, because the first cathode flow field groove is designed to compensate the influence with the flow resistance by the distribution of the flow field cross-sectional area, the pressure along the extending direction is constant. Similarly, in the second cathode flow field groove44, the pressure along the extending direction is made constant. As a result, the distribution of the pressure difference between the first cathode flow field groove42and the second cathode flow field groove44adjacent to each other becomes uniform over the entire oxygen-containing gas flow field36. Therefore, the power generation cell10of the present embodiment is further improved in performance of discharging generated water.

The first anode flow field groove64and the second anode flow field groove66(seeFIG.6) can also have the same flow field cross-sectional area distribution.

The above embodiments are summarized as mentioned below.

There is provided the power generation cell10of the fuel cell comprising the membrane electrode assembly12a, the cathode separator14and the anode separator16, the membrane electrode assembly including the electrolyte membrane30and the electrodes arranged on both sides of the electrolyte membrane, the membrane electrode assembly being sandwiched by the cathode separator and the anode separator, wherein the cathode separator comprises the cathode line ridges38that protrude from the cathode separator, contact the membrane electrode assembly and extend in the flow direction of the oxygen-containing gas, and the plurality of cathode flow field grooves40that are formed between the cathode line ridges and form the oxygen-containing gas flow field, the plurality of cathode flow field grooves comprise the first cathode flow field groove42that is blocked on the downstream side in the flow direction of the oxygen-containing gas, and the second cathode flow field groove44that is blocked on the upstream side in the flow direction of the oxygen-containing gas, and the second flow field groove is arranged adjacent to the first flow field groove in the flow field width direction. In this case, the anode flow field groove (on the fuel gas side) may have a flow field configuration similar to that conventionally known.

In the power generation cell, a pressure difference is generated between the first cathode flow field groove and the second cathode flow field groove. This pressure difference causes the oxygen-containing gas to flow from the first cathode flow field groove toward the second cathode flow field groove in the membrane electrode assembly. Water generated in the membrane electrode assembly is efficiently removed by an active process caused by the flow of the oxygen-containing gas in addition to a passive process caused by diffusion. Therefore, the power generation cell is excellent in drainage performance, can prevent reaction inhibition due to flooding, and improves power generation efficiency.

The anode separator may include the anode line ridges56aprotruding from the anode separate to contact the membrane electrode assembly and extending in the flowing direction of the fuel gas, and the plurality of anode flow field grooves56bformed between the anode line ridges and forming the fuel gas flow field, and the plurality of anode flow field grooves56binclude the first anode flow field groove64blocked on the downstream side in the flowing direction of the fuel gas and the second anode flow field groove66blocked on the upstream side in the flowing direction of the fuel gas, and the second anode flow field groove may be arranged adjacent to the first anode flow field groove in the flow field width direction. The power generation cell including such an anode separator is also excellent in performance of removing water that permeates through the electrolyte membrane to the anode side.

The plurality of cathode flow field grooves may include the plurality of first cathode flow field grooves blocked on the downstream side in the flow direction of the oxygen-containing gas and the plurality of second cathode flow field grooves blocked on the upstream side in the flow direction of the oxygen-containing gas, and the first cathode flow field grooves and the second cathode flow field grooves may be alternately arranged in the flow passage width direction. In this power generation cell, the generated water retained in portions of the membrane electrode assembly in contact with the cathode line ridges can be efficiently discharged through the adjacent second cathode flow field grooves. As a result, the power generation cell improves power generation performance by preventing reaction inhibition due to flooding on the cathode side.

The plurality of anode flow field grooves may include the plurality of first anode flow field grooves blocked on a downstream side in the flow direction of the fuel gas and the plurality of second anode flow field grooves blocked on the upstream side in the flow direction of the fuel gas, and the first anode flow field grooves and the second anode flow field grooves may be alternately arranged in the flow field width direction. The power generation cell improves power generation performance by preventing reaction inhibition due to flooding on the anode side.

The flow field cross-sectional area of the first cathode flow field groove may be smaller than the flow field cross-sectional area of the second cathode flow field groove. This power generation cell achieves the increased internal pressure at the first cathode flow field grooves having the smaller flow field cross-sectional areas, and the decreased internal pressure at the second cathode flow field grooves having the larger flow field cross-sectional areas. As a result, the power generation cell further increases the pressure difference between the first cathode flow field groove and the second cathode flow field groove to further improve the drainage performance.

The flow field cross-sectional area of the first anode flow field groove may be smaller than the flow field cross-sectional area of the second anode flow field groove. The power generation cell further increases the pressure difference between the first anode flow field groove and the second anode flow field groove to further improve the drainage performance.

The first cathode flow field groove may have the flow field cross-sectional area decreasing from upstream to downstream in the flow direction of the oxygen-containing gas, and the second cathode flow field groove may have the flow field cross-sectional area increasing from upstream to downstream in the flow direction of the oxygen-containing gas. In this power generation cell, by making the distribution of the pressure difference between the first cathode flow field groove and the second cathode flow field groove constant, local variation in drainage performance can be suppressed.

The first anode flow field groove may have the flow field cross-sectional area that decreases from upstream to downstream in the flow direction of the fuel gas, and the second anode flow field groove may have the flow field cross-sectional area that increases from upstream to downstream in the flow direction of the fuel gas. In this power generation cell, by making the distribution of the pressure difference between the first anode flow field groove and the second anode flow field groove constant, local variation in drainage performance can be suppressed.

The present invention is not limited to the above-described embodiments, and various configurations can be adopted therein without departing from the essence and gist of the present invention.