JPH08111230A - Operating method for solid high polymer type fuel cell - Google Patents

Abstract

PURPOSE: To establish a high power generating performance stably for a long period of time by accomplishing an operating method for fuel cell which generates such an under-the-cell-surface temp. distribution that the oxidator gas water vapor pressure distribution in an oxidizer gas supply path is in equilibrium with the saturated vapor pressure distribution on a catalyst layer reaction part. CONSTITUTION: A fuel cell of solid high polymer type requires preventing drying and product water condensation in electrochemical reactions on the surface of an electrolyte film, and therefore, humidity management is conducted by generating an apropriate temp. distribution on the cell surface. The under-the- cell-surface optimum temp. distribution to give max. output voltage under the operating conditions including the current density, reaction gas total pressure, inlet air dew point, rate of air utilization, the rate of exhaustion of product water, etc., is established by controlling the under-the-cell-surface upper part temp. and under-the-cell-surface temp. difference between above and below to their optimum values or the neighborhoods. The under-the-cell-surface temp. distribution is controlled by adjusting the temp. of the cooling medium and the rate of flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention appropriately controls the temperature distribution within the cell surface of a flat plate type solid polymer electrolyte fuel cell to prevent the solid polymer electrolyte membrane from being dried and excessively wetted, and to improve the solid high temperature. The present invention relates to a method for stable operation of a molecular fuel cell.

[0002]

2. Description of the Related Art Fuel cells are classified into solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid electrolyte fuel cells, etc., depending on the type of electrolyte used and the operating temperature. Be separated. Since fuel cells generate heat in the electrochemical reactions that produce direct current electricity, cooling means are provided to maintain the temperature at an acceptable operating temperature.

A polymer electrolyte fuel cell that has been conventionally used has a cooling unit inside and a cooling medium is circulated in this cooling unit as disclosed in, for example, Japanese Patent Laid-Open No. 144451/1993. Is kept at a predetermined temperature. 7 and 8 show an example of the configuration of a conventional polymer electrolyte fuel cell. Figure 7 (a) shows a side view of the stack.
In (a), 9 is a stack, in which a plurality of unit cells 8 each composed of a cell and a separator are stacked, and further, current collecting plates 91A and 91B for taking out DC power generated at both ends thereof from the stack 9, Battery 8, collector plates 91A, 91B
Insulating plate 92 for electrically insulating the structure from the structure
A and 92B and the tightening plates 93A and 93B arranged at both outer ends of the stack 9 in which the unit cells 8, the current collecting plates 91A and 91B, and the electric insulating plates 92A and 92B are stacked are sequentially stacked and tightened. The attachment plates 93A and 93B are configured so that a proper amount of pressure is applied from both outer side surfaces thereof by tightening bolts 94.

FIG. 7 (b) is a side sectional view of a unit cell. In FIG. 7 (b), each unit cell 8 is a cell 7
And the fuel gas flow path 6 is disposed on one side surface of the cell 7.
A separator 6A that has a large number of 1a and is made of a material that is impermeable to gas and is excellent in heat and electrical conductivity; and an oxidant gas flow channel 61b (hereinafter referred to as a fuel gas flow channel) that is disposed on the other side surface of the cell 7. The separator 6B is made up of a material similar to the separator 6A. The cell 7 has a thin rectangular shape and includes an electrolyte layer 71 made of a solid polymer electrolyte membrane, a fuel electrode film 72 disposed on one main surface side of the electrolyte layer 71 and supplied with fuel gas, It is composed of an oxidant electrode film 73 which is provided with an oxidant gas and is disposed on the other main surface side of the electrolyte layer 71. The fuel electrode film 72 and the oxidant electrode film 73 both support the catalyst layers 74a and 74b containing a catalyst active material and the catalyst layers 74a and 74b, and supply the reaction gas to the catalyst layer and discharge it from the catalyst layer, Moreover, it is composed of porous electrode film base materials 75a and 75b having a function as a current collector, and the respective catalyst layers 74a and 74b are brought into close contact with the electrolyte layer 71. As the electrolyte layer 71, a perfluorosulfonic acid resin film (for example, Nafion film manufactured by DuPont, USA)
Is used, and it functions as a good proton conductive electrolyte when it is saturated with water.

FIG. 8B shows the separator 6A in the in-plane cooling structure of the cell, and the cooling medium 5 is provided on the other surface of the separator 6A provided with the reaction gas passage 61a.
A coolant channel 65 is formed to allow the fluid to flow therethrough. The coolant channel 65 is a parallel portion 65a in which a plurality of coolant channels are arranged in parallel and provided in parallel with the directions of the reaction gas channels 61a and 61b.
And one refrigerant channel terminal portion 65b that bundles the parallel portion 65a at one end portion and a refrigerant channel terminal portion 65c that bundles the parallel portion 65a at the other end portion. Each of the terminal portions 65b and 65c of the coolant channel 65 has a through hole 66.
And 67, and the through holes 66 and 67 both function as a manifold.

In the unit cell 8 at one end of the stack 9, the through hole 66 is connected to the refrigerant flow port formed in communication with the inlet 93a for the cooling medium 5, while the through hole 6 is provided.
7 is sealed. Further, in the unit cell 8 at the other end, the through hole 67 is connected to the refrigerant flow port formed in communication with the outlet 93b of the cooling medium 5 provided in the tightening plate 93B, while the through hole 66 is provided. Is sealed. In stack 9,
The flow paths of the cooling medium 5 formed in the unit cells 8 are connected in parallel with each other, but this is due to the temperature difference of the cooling medium 5 between the unit cells 8 arranged in the stacking direction of the stack 9. This is to reduce

FIG. 8 (a) schematically shows an example of the cooling structure of the stack 9 together with its main peripheral devices. The refrigerant supply path includes a pressurizing pump 97 that supplies a pressure necessary to circulate the cooling medium 5, a control valve 98 that controls the flow rate of the cooling medium 5 (hereinafter, also referred to as a refrigerant flow rate), and heat dissipation. Device 96 and piping 9 that connects between them
9 and 9. The cooling medium 5 introduced from the inflow port 93a and having a high temperature by absorbing the heat generated in the stack 9 flows out from the outflow port 93b and is circulated to the heat dissipation device 96 in the refrigerant supply path to be removed of heat. The temperature (hereinafter sometimes referred to as the refrigerant temperature) is lowered to a desired temperature, and the gas is recirculated to the stack 9 from the inflow port 93a again.

By the way, the fuel gas and the oxidant gas supplied to the cell 7 undergo the following electrochemical reaction at the three-phase interface formed by the catalyst and the solid polymer electrolyte in the respective catalyst layers 74a and 74b. Consumed.

[0009]

[Chemical formula 1] H ₂ → 2H ⁺ + 2e ^- anode

[0010]

Embedded image (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O cathode As described above, water is produced as a whole reaction. In order to maintain high power generation efficiency, it is necessary to hydrate the solid polymer electrolyte membrane in a saturated state, so the reaction gas is humidified in advance and then supplied to the cell.

[0011]

In the polymer electrolyte fuel cell, the electrochemical reaction is a water production reaction, and the produced water is mainly discharged to the oxidant gas flow path on the cathode side. The flow rate of water vapor in the agent gas is the smallest on the inlet side of the cell and increases as it approaches the outlet side of the cell.

However, the oxidant gas that has permeated through the oxidant electrode substrate is diffused into the catalyst layer, and the oxidant gas, the catalyst, and
When forming a three-phase interface with the solid polymer electrolyte to cause an electrochemical reaction, the catalyst layer is excessively wetted by the condensation of water, blocking the capillary in which the reaction gas in the porous oxidizer electrode substrate diffuses. It is not preferable to store it. The driving force for the generated water discharge is the difference in water vapor pressure between the reaction gas and the solid polymer electrolyte membrane, whereas when the in-cell temperature is uniform, the water vapor pressure in the solid polymer electrolyte membrane is constant. The distribution of the water vapor pressure of the reaction gas becomes higher as it goes to the outlet side of the gas flow path, and the generated water is prevented from being discharged. However, if the humidification amount of the reaction gas is reduced in order to prevent this, the solid polymer electrolyte membrane will dry and the battery characteristics will deteriorate.

In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an appropriate operation control method of a solid polymer electrolyte fuel cell for preventing drying and condensation of produced water on the surface of the solid polymer electrolyte membrane. To do.

[0014]

In order to solve the above-mentioned problems, the present invention provides a stack in which a plurality of cells, which receive a supply of a fuel gas and an oxidant gas and generate a direct current power, are laminated with a separator interposed therebetween. The stack includes a cooling unit that is provided for each of the cells or for each of the plurality of cells and removes heat generated in the cells, and the cells sandwich an electrolyte layer formed of a solid polymer membrane and the electrolyte layer. And a oxidant electrode (cathode), respectively, and the cooling section has a coolant channel for allowing a cooling medium to flow therethrough. The operating method of a polymer electrolyte fuel cell, in which the oxidant gas outlet side temperature (lower temperature in the cell surface) is formed higher than the inlet side temperature (upper surface temperature in the cell surface), Pressure, inlet air dew point, air utilization rate, raw From the water discharge rate, the optimum value of the upper temperature in the cell surface where the cell output voltage becomes maximum and the optimum value of the difference between the upper temperature in the cell surface and the lower temperature in the cell surface (difference in vertical temperature in the cell surface). By adjusting the temperature and flow rate of the cooling medium, by controlling to be the optimum value of the optimum upper temperature in the cell plane or its vicinity and the optimum value of the vertical temperature difference in the cell surface or its vicinity. To be achieved.

Further, in the method of operating a polymer electrolyte fuel cell, the upper temperature in the cell plane is set to an optimum value ± 3 of the temperature.
℃, the upper and lower temperature difference in the cell plane is the optimum value of the temperature difference ± 1 ℃
It is preferable to control within the range. Further, in the operating method of the polymer electrolyte fuel cell, the upper temperature in the cell plane is within the optimum value of ± 1 ° C., and the temperature difference between the upper and lower sides in the cell plane is within the optimum value of the temperature difference of ± 1 ° C. Most preferably, it is controlled.

[0016]

In the polymer electrolyte fuel cell, the water produced by the reaction is released as water vapor into the reaction gas flowing through the reaction gas flow path, so that the water vapor concentration in the reaction gas gradually increases during the flow process. To rise. The gas flow direction is controlled so that the refrigerant temperature and the refrigerant flow rate are controlled so that the gas flows into the reaction gas flow path from the side where the temperature distribution in the cell surface is low and is discharged from the side where the temperature distribution in the cell surface is high. By forming the internal temperature distribution, the water vapor pressure of the reaction gas and the saturated water vapor pressure that is low on the low temperature side and high on the high temperature side of the reaction portion of the catalyst layer are appropriately balanced. In the optimum state, since the generation and discharge of water are balanced in any part of the cell surface, excessive drying of the solid polymer electrolyte membrane and excessive formation of the catalyst layer due to condensation of the generated water. It is possible to prevent the inhibition of the reaction gas diffusion due to the wetting, keep the reaction part of the catalyst layer in a saturated state, and suppress the decrease of the proton conductivity, and prevent the deterioration of the battery characteristics.

[0017]

Embodiments of the present invention will be described in detail below with reference to the drawings. Embodiment 1; FIGS. 1 (a) and 1 (b) show one embodiment of the method for operating the polymer electrolyte fuel cell of the present invention.
In forming an appropriate temperature distribution in the cell surface of the polymer electrolyte fuel cell, the state of the temperature distribution can be controlled by the refrigerant temperature and the refrigerant flow rate. That is, when the refrigerant flow rate is increased, the vertical temperature difference in the cell plane is reduced, and conversely, when the refrigerant flow rate is reduced, the vertical temperature difference in the cell plane is increased.

Table 1 shows the operating conditions in this embodiment.

[0019]

[Table 1]

FIG. 1 (a) shows that when operating under the conditions shown in Table 1 above, the refrigerant temperature and the refrigerant flow rate are controlled to change the upper temperature in the cell surface while keeping the temperature difference between the upper and lower surfaces in the cell surface constant (5 ° C.). , Is an experimental result in which the voltage change of the cell output is plotted. In addition, FIG. 1 (b) shows that the temperature and the flow rate of the refrigerant are controlled during the operation under the conditions shown in Table 1, and the temperature difference between the upper and lower sides of the cell surface is changed while keeping the upper temperature inside the cell surface constant (71 ° C.). It is the experimental result which plotted the voltage change of the cell output. From these experimental results, in the operating conditions, there is an optimum value of the cell surface upper temperature where the cell output voltage is maximum and an optimum value of the cell surface upper and lower temperature difference, and preferably, the cell surface upper temperature is 71 ° C. ± 3 ° C (most preferably ±
It was confirmed that the temperature difference between the upper and lower sides of the cell surface was 5 ° C ± 1 ° C.

A similar tendency is obtained even if the above-mentioned operating conditions are changed. Further, as the means for forming the in-cell temperature distribution, the cooling configuration thereof is not particularly selected, and for example, the configurations shown in Examples 2 to 5 described later can be adopted. Furthermore, in order to obtain the corroborativeness of this experimental result, the simulation of the temperature distribution with good discharge efficiency of generated water was performed. The results will be described below.

First, the following equation is established from the generated water discharge condition.

[0023]

[Formula 1] αj / 2F = (De / Le) (Pe-Ps) = (Dg / Lg) (Ps-Pg) where j: current density, α: generated water discharge rate, De: Diffusion coefficient Le: Diffusion layer thickness, in gas channel Dg: Diffusion coefficient Lg: Diffusion layer thickness, Water vapor partial pressure (Electrode: P
e, electrode / gas interface Ps, gas flow path: Pg), F: Faraday constant. Where Ke = De / Le, Kg = Dg / Lg, Pc = Pe-Pg
When [Pc = Pc ₀ (T ₀ / T) ^m (P / P ₀ ) (j / j ₀ )], the following equation is established from the above mathematical expression 1.

[0024]

[Formula 2] αj / 2F = Pc / (1 / Ke + 1 / Kg) Further, the following equation holds for the water vapor pressure.

[0025]

[Formula 3] R _n P _n / P _all = W _n / (V _n + W _n ), where n: gas flow passage division part, I _n : partial current, V _n : air flow rate, W _n : water vapor flow rate, P _n : Saturated water vapor pressure (derived from Antoine equation), T _n : Temperature, R _n : Relative humidity, P _all : Total pressure W _{n + 1} = W _n + I _n / 2F, V _{n + 1} = V _n- I _n / 4F, Pg = R _n P _n Furthermore, assuming that Pe = P _n , the optimum temperature distribution in the cell plane was calculated by solving the above equations 1 to 3.

FIG. 2 shows a comparison between this result and the experimental result.
Is. In FIG. 2, since the simulation result and the experimental result agree with each other with an error of about ± 1 ° C., the credibility of the experimental result described above was confirmed. Next, a means for obtaining a desired in-plane temperature distribution in the cell will be described. In the second and third embodiments described below, the concept disclosed in Japanese Patent Application No. 5-269344 is applied as the in-cell temperature distribution forming means of the first embodiment. Further, in the third and fourth embodiments, the concept disclosed in the above-mentioned Japanese Patent Laid-Open No. 5-144451 is applied as the in-cell temperature distribution forming means of the first embodiment.

Example 2; FIG. 3 (a) is a side view schematically showing the means for forming the in-plane temperature distribution of the cell of the polymer electrolyte fuel cell for carrying out the operating method of the present invention. FIG.
(b) is a plan view of the separator. In FIGS. 3 (a) and 3 (b), the same parts as those of the conventional polymer electrolyte fuel cell shown in FIGS. 7 to 8 are designated by the same reference numerals, and the description thereof will be omitted.

In FIGS. 3 (a) and 3 (b), reference numeral 8 is a unit cell using a separator 6C. The separator 6C is
Four grooves 11 are provided in parallel as refrigerant flow paths. In addition, 9A is the unit cell 8 and the fastening plates 93C, 93.
It is a stack consisting of D and. Tightening plate 93C, 93D
Is the groove 1 for each of the tightening plates 93A and 93B.
An inflow port 93a for the cooling medium 5 or an outflow port 93b for the cooling medium 5 is provided in the number corresponding to one.

The supply of the cooling medium 5 to the stack 9A is performed by a coolant passage having the same structure as the coolant passage shown in FIG. 8 (b). However, the connection between the inflow port 93a and the outflow port 93b included in the stack 9A is performed as follows. That is, the cooling medium 5 is first supplied to the inflow port 93a of the refrigerant passage located at the most upstream side where the reaction gas flows into the stack 9A. The cooling medium 5 flowing out from the outlet 93b of the refrigerant passage located on the most upstream side has the outlet 93 of the refrigerant passage located on the next upstream side.
b. Subsequently, the cooling medium 5 flowing out from the inflow port 93a of the refrigerant flow path located on the upstream side next is supplied to the inflow port 93a of the refrigerant flow path located on the further upstream side. After that, the connection between the inflow port 93a and the outflow port 93b is connected to each other so that the cooling medium 5 is sequentially supplied to the refrigerant channel located on the upstream side. Here, since the cooling medium 5 absorbs reaction heat when flowing through the refrigerant flow path, a temperature distribution within the cell plane that gradually increases in the flowing direction of the reaction gas is formed. As a result, the in-cell temperature distribution is set to a relatively low value that does not dry the reaction gas near the inlet of the reaction gas, and a relatively high value that does not liquefy the produced water near the outlet of the reaction gas. It is possible to do. Further, at this time, the cooling medium 5 to the refrigerant channel
Since the flow directions of the cells are reversed in the refrigerant channels adjacent to each other, the temperature distribution states of the cells 7 along the refrigerant channels are alternately reversed, which results in the temperature distribution in the plane vertical direction of the cells 7. Can be approximately uniform.

Embodiment 3; FIG. 4 (a) is a diagram showing the main means for forming the temperature distribution in the cell surface of a polymer electrolyte fuel cell for carrying out the operating method of the present invention, which is different from that of Embodiment 2. It is also shown schematically. Figure 4 (b) is
FIG. 3A is a plan view of a separator included in the stack shown in (a). In FIGS. 4 (a) and 4 (b), the same parts as those of the conventional polymer electrolyte fuel cell shown in FIGS. 7 to 8 are designated by the same reference numerals, and the description thereof will be omitted.

In FIGS. 4 (a) and 4 (b), 8 is a unit cell employing the separator 6D, and the separator 6D is 3
The groove 11 is provided, and each is formed in a direction substantially orthogonal to the reaction gas flow direction. Both ends of each groove 11 have through holes 12, 13 respectively.
Is communicated to. The tightening plates 93E and 93F are provided with the inflow ports 93a for the cooling medium 5 or the outflow ports 93b for the cooling medium 5 in a number corresponding to the number of the respective recessed grooves 11, and the respective refrigerant flow paths are isolated from each other. ing.

The refrigerant flow path 5 of the stack 9B is connected to the heat dissipation device 2
3 is used, and control valves 98 having the same number of flow rates as the number of the concave grooves 11 are provided. The heat radiating device 23 has the same number of unit heat radiators 23a, 23 as the number of the concave grooves 11 having different heat radiating capacities.
b and 23c. Each of the unit radiators has a heat dissipation capability that increases in the order of 23c, 23b, and 23a. Therefore, at the same temperature, the heat dissipation device 23
The temperature of the cooling medium 5a radiated to the unit radiator 23a is the lowest at the outlet of the radiator 23, and the temperature of the cooling medium 5b radiated to the unit radiator 23b is the temperature of the cooling medium 5a. Higher than the unit radiator 2
The temperature of the cooling medium 5c radiated to 3c is higher than the temperature of the cooling medium 5b. The cooling mediums 5a to 5c flowing out from the respective outlets 93b are merged and then the pressure pump 97.
Reflux to. As a result, the temperature distribution on the surfaces of the electrode films 72 and 73 of the cell 7 in FIG. 7 (b) should be relatively low near the reaction gas inlet and relatively high near the reaction gas outlet. Is possible.

Embodiment 4; FIG. 5 is a sectional view showing a means for forming a temperature distribution in a cell surface of a polymer electrolyte fuel cell according to a further embodiment of the present invention. The same reference numerals are given and the description thereof is omitted. In FIG. 5, a plurality of refrigerant flow paths 65 are provided in the separator 6 in parallel with the reaction gas flow paths 61, and the cooling medium 5 and the reaction gas flow in from one end of the separator 6 by making the flowing directions of the reaction gas the same. Since the cooling medium 5 absorbs the heat generated by the power generation of the cells and rises in temperature, a temperature distribution that is low on the inlet side of the cooling medium 5 and high on the outlet side is formed in the in-plane direction of the cell.

Embodiment 5; FIG. 6 shows the essential parts of the reaction gas and cooling medium flow structure showing the means for forming the in-plane temperature distribution of the solid polymer electrolyte fuel cell according to a further different embodiment of the present invention. It is a cross-sectional view, the same parts as those of the conventional art are denoted by the same reference numerals, and the duplicated description will be omitted. In FIG. 6, in the separator 6, a plurality of refrigerant channels 22A to 22Z formed in parallel are provided in a direction orthogonal to the reaction gas channel 61, and the refrigerant channels 22 are closely spaced at the upper part of the cell. It is assumed that the lower part of the cell is sparsely distributed, and a temperature distribution is formed in the in-plane direction of the cell.

In the above description of Examples 2 to 5, the cell stacking direction in the stack was such that the direction normal to the cell surface was horizontal, but the invention is not limited to this, and the cell stacking direction is not limited to this. May be changed in the vertical direction.

[0036]

As described above, according to the present invention, the temperature distribution on the surface of the oxidizer electrode film of the fuel cell is controlled so that the upper temperature in the cell plane and the vertical temperature difference in the cell plane are at or near the optimum values. By driving so that
The cell output voltage can be extremely increased to at least 8% or more as compared with the operating state that is not near the optimum value. As a result, high power generation performance can be obtained, and suitable humidification control of the solid polymer membrane can be performed, so that the cell characteristics can be stably obtained for a long time and the life of the fuel cell can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an operation example of the present invention, FIG. 1 (a) is a diagram showing a relationship between a cell output voltage of a polymer electrolyte fuel cell and an upper temperature in a cell surface, and FIG. 1 (b) is a diagram. The figure which shows the relationship between the cell output voltage and the temperature difference in the cell plane.

FIG. 2 is a diagram showing the relationship between the simulation result of the optimum temperature distribution in the cell plane and the experimental result according to FIG.

FIG. 3 shows an embodiment of a cooling structure for forming a temperature distribution in a cell surface according to the present invention, and FIG. 3 (a) is a side view schematically showing a means for forming a temperature distribution in the cell surface. 3 (b) is a plan view of the separator

FIG. 4 shows an embodiment in which a cooling structure for forming an in-cell temperature distribution according to the present invention is different, and FIG. 4 (a) is a side view schematically showing a means for forming an in-cell temperature distribution. Four
(b) is a plan view of the separator

FIG. 5 is a sectional view of a cell in a further different embodiment of the cooling structure for forming the in-plane temperature distribution of the cell according to the present invention.

FIG. 6 is a sectional view of a cell in a further different embodiment of the cooling structure for forming the in-plane temperature distribution of the cell according to the present invention.

FIG. 7 (a) is a side view of a conventional stack, FIG. 7 (b).
Is a side sectional view of a conventional cell

FIG. 8 (a) is a diagram showing an example of a conventional stack cooling configuration, and FIG. 8 (b) is a diagram showing an example of a conventional cell in-plane cooling configuration.

[Explanation of symbols]

 8 Single cell 7 cells 9, 9 A, 9 B Stack 93 A to 93 F Tightening plate 23 Radiator 23 a to 23 c Unit radiator 5, 5 a to 5 c Cooling medium 93 a Cooling medium inlet 93 b Cooling Medium outlet 61 a, 61 b Reaction gas flow path 65, 65 a to 65 c Refrigerant flow path 6 A to 6 D Separator 12 Through hole 13 Through hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Enoki No. 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (3)

[Claims] 1. A unit cell integrated body (stack) in which a plurality of cells, which receive a supply of a fuel gas and an oxidant gas and generate direct current power, are stacked via a separator, and each of the cells in the stack, or A cooling unit that is provided for each of a plurality of cells and removes heat generated in the cells is provided, and the cells include an electrolyte layer formed of a solid polymer membrane, and fuel electrodes (anodes) that are respectively disposed so as to sandwich the electrolyte layer. )
And a oxidant electrode (cathode), the cooling unit has a coolant channel for flowing a cooling medium, and the inside of the cell surface is higher than the oxidant gas inlet side temperature (the upper temperature inside the cell surface). , A method of operating a polymer electrolyte fuel cell in which the temperature on the outlet side of the oxidant gas (the temperature on the lower side of the cell surface) is higher than that of the current density, the total pressure of the reaction gas, the dew point of the inlet air, and the air utilization rate. ，
From the generated water discharge rate, the optimum value of the upper temperature in the cell surface where the cell output voltage becomes maximum and the optimum value of the difference between the upper temperature in the cell surface and the lower temperature in the cell surface (difference between the upper and lower temperatures in the cell surface). By controlling the temperature and flow rate of the cooling medium, control is performed so as to be the optimum value of the upper temperature in the optimum cell plane or in the vicinity thereof and the optimum value of the vertical temperature difference in the cell surface or in the vicinity thereof. And a method for operating a polymer electrolyte fuel cell. 2. The method for operating a polymer electrolyte fuel cell according to claim 1, wherein the upper temperature in the cell plane is the optimum value of the temperature ± 3 ° C., and the temperature difference between the upper and lower sides in the cell plane is the optimum temperature difference. A method for operating a polymer electrolyte fuel cell, which is controlled within a value range of ± 1 ° C. 3. The method for operating a polymer electrolyte fuel cell according to claim 1, wherein the upper temperature in the cell plane is an optimum value of the temperature ± 1 ° C., and the temperature difference between the upper and lower sides in the cell plane is the optimum temperature difference. A method for operating a polymer electrolyte fuel cell, which is controlled within a value range of ± 1 ° C.