JP2011054284A - Fuel cell power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure stable power generation by rapidly raising the temperature of a fuel cell even if the fuel cell reaches a freezing point of water in temperature. <P>SOLUTION: A solid polymer fuel cell includes a separator having an anode flow passage for distributing fuel; a separator having a cathode flow passage for supplying an oxidizer; and a membrane/electrode assembly composed of two electrodes and an electrolyte film, the membrane/electrode assembly having a power generation cell held between the separators. The fuel cell further includes a resistor provided between the two adjacent separators so that resistance between the separators is reduced in a low-temperature state of at least the freezing temperature of water or lower to attain a current-carriable state. The resistor does not make electricity flow substantially at a temperature not lower than at least room temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for starting a fuel cell power generation system.

  A polymer electrolyte fuel cell using a reformed fuel of hydrogen or an organic compound has characteristics such as low noise and low operating temperature (about 70 to 80 ° C.). Therefore, a wide range of uses are expected as a portable power source, a power source for an electric vehicle, or a power source for an electric motorcycle, an assist type bicycle, a light vehicle such as a medical care wheelchair or a senior car.

  In the future, it is expected that sunlight or wind power will be converted into electrical energy, and that energy will be used for water electrolysis to produce transportable hydrogen. If hydrogen production becomes widespread, it is likely that energy systems using hydrogen will be highlighted as the ultimate clean energy system. Solar energy, etc. is renewable and clean and inexhaustible, making it the most powerful energy source to break out of the current fossil energy society. If hydrogen is stored at a high density using a hydrogen storage alloy or the like, energy can be transported more efficiently than the energy stored in the secondary battery. If renewable energy such as sunlight can be used, it is expected that a sustainable energy society that can significantly reduce carbon dioxide will be built. In such a future society, there is high expectation for a polymer electrolyte fuel cell that can reconvert hydrogen into electricity with high efficiency.

  A polymer electrolyte fuel cell is an electrochemical element that uses an electrolyte membrane that moves protons and directly converts the recombination reaction of hydrogen and oxygen into electrical energy. The electrolyte membrane that moves protons has electrodes formed on both sides thereof. This is called a membrane-electrode assembly (hereinafter abbreviated as MEA). A unit cell made of a separator is provided so as to face each of the electrodes. The separator is formed with a flow path (channel) for circulating fuel or oxidant.

  It is well known that when the electrolyte membrane does not contain water, the proton (hydrogen ion) transfer rate in the electrolyte membrane is extremely slow. Therefore, water is added to the fuel or oxidant in advance and supplied to the fuel cell. This operation of adding water is called humidification. As a result, drying of the electrolyte membrane can be suppressed, and water generated by oxidation of hydrogen is further added to keep the electrolyte membrane wet. Therefore, the prior art has a problem that the polymer electrolyte fuel cell cannot be operated without humidification.

  Patent Documents 1 to 8 disclose means for facilitating starting at a low temperature in a polymer electrolyte fuel cell system using pure hydrogen.

  Patent Documents 1 and 2 disclose a method for preventing freezing by discharging water in the fuel cell device to the outside in accordance with changes in weather conditions and outside air temperature after the operation is completed.

  The invention of Patent Document 3 has an automatic heat retaining function of the fuel cell device when the system is stopped and stored, thereby preventing deterioration and damage of the system due to freezing, shortening the startup time, and enabling reliable startup. It is about the method.

  Patent Document 4 discloses an invention in which a planar heating element is formed on a separator or the like of a fuel cell stack and has a temperature raising function or a heat retaining function.

  Patent Document 5 discloses a configuration in which a heater is provided on the surface or inside of a separator and has a self-heating or heat-retaining function.

  Patent Document 6 relates to an invention in which a heating element is installed outside the cell stack to heat the cell stack.

  Patent Document 7 discloses an invention in which a heater is provided in the vicinity of a gas diffusion layer, and a cell is directly heated by energization.

  The invention described in Patent Document 8 is an invention in which a battery is heated while being energized by heating a heater installed in a cooling water flow path.

JP-A-11-273704 JP 2004-103395 A JP 2001-143736 A JP 2004-220947 A JP 2004-220946 A JP 2007-35410 A Japanese Patent Laid-Open No. 2003-163020 JP 2002-313391 A

  In view of the prior art, the present inventors have studied a configuration for starting a polymer electrolyte fuel cell system in a short time from a state in which the outside air temperature has become low, and have reached the present invention. In particular, it was an important issue to propose a battery structure and system configuration that can start up the system in a short time from a frozen state of the polymer electrolyte fuel cell. In the following, technical items that are problematic in realizing a highly efficient power generation system will be described in detail.

A typical example of the polymer electrolyte fuel cell targeted by the present invention is a fuel cell using hydrogen or a fossil fuel reformed gas (hydrogen-containing gas) as a fuel and air as an oxidant. The reaction of Formula 1 proceeds at the anode (fuel electrode) of these fuel cells, and the reaction of Formula 2 proceeds at the cathode (oxidant electrode), and the oxidation reaction of hydrogen occurs as a whole. The chemical reaction energy of Formula 3 is converted into electric energy, and electric power can be taken out from the fuel cell.
H ₂ → 2H ⁺ + 2e ⁻ (Formula 1)
2H ⁺ +1/2 O ₂ + 2e ⁻ → H ₂ O (Formula 2)
H ₂ +1/2 O ₂ → H ₂ O (Formula 3)

  In the polymer electrolyte fuel cell that causes this reaction, an anode is formed on one surface of a solid polymer electrolyte membrane that transmits hydrogen ions, and a cathode is formed on the other surface. In general, the anode and the cathode have a laminated structure of a catalyst layer and a gas diffusion layer that promote the reactions of Formulas 1 and 2. Thus, an integral structure composed of a solid polymer electrolyte membrane, an anode, and a cathode is called a so-called membrane-electrode assembly. Here, it is known that hydrogen ions that permeate the electrolyte membrane are difficult to move unless the electrolyte membrane absorbs moisture and the electrolyte membrane is wet. Water is replenished with product water. For this reason, water is present in the vicinity of the MEA during operation of the fuel cell.

  However, when the fuel cell is stopped, the fuel cell is usually stored in the presence of water, and if this water is frozen at the next start-up, the flow of gas is hindered. In addition, the water in the electrolyte membrane is difficult to move, and the movement of hydrogen ions is also inhibited.

  Therefore, there is a problem with a method of starting the polymer electrolyte fuel cell at a low temperature, particularly in an extremely cold temperature where water is frozen.

  In the present invention, as a result of examining the low temperature startup method, it has been found that it is necessary to solve the following two technical problems in order to shorten the startup time and stabilize the output after startup.

  The first problem is to provide a cell structure and system configuration in which sufficient water can exist from the start-up, and operating conditions. In order to raise the temperature of the battery in a short time, it is advantageous that water does not exist on the surface or inside of the MEA or the flow path of the separator. However, it is necessary to avoid a decrease in cell power generation performance due to the discharge of water. is there. It is desirable that the temperature can be easily raised even if water is left inside the cell to some extent and it is frozen.

  In addition, the system may need to be stopped urgently due to an external force such as a natural disaster, system power interruption, or a collision. In such a case, water remains inside the cell stack, and the system stops without being able to drain as planned. In such a case, it is necessary to melt the ice inside the cell stack and to quickly restart the fuel cell system.

  According to the prior art, a method of supplying cooling water or gas heated outside the battery to the cell stack has been devised, but because of the temperature rise of the cooling water or gas itself and the heat radiation from the piping through which they pass There is a problem that the startup time cannot be shortened. Furthermore, there is a problem that high-temperature cooling water cannot be circulated when the flow path and manifold inside the cell stack are blocked with ice. Therefore, a method of raising the temperature of the cell stack itself at the time of startup is desirable.

  A second problem is to provide a heating structure and a heating method that prevent contaminants such as impurities from entering the cell. This is advantageous in that heating in the vicinity of the cell shortens the startup time due to temperature rise. However, by providing a heating element inside the cell, an elution component such as a metal substance may be replaced with hydrogen ions in the electrolyte membrane, thereby impeding permeation of hydrogen ions. An object of the present invention is to prevent a decrease in cell performance due to contaminants from a heating element.

  In order to solve the two technical problems described above at the same time, the inventors have intensively studied to arrive at the present invention.

  A fuel cell to which the present invention is directed comprises a separator having an anode flow path for circulating fuel, a separator having a cathode flow path for supplying an oxidant, and a membrane-electrode assembly comprising two electrodes and an electrolyte membrane. The membrane-electrode assembly is a fuel cell having a power generation cell sandwiched between the separators. In such a battery, low temperature startup can be realized by the following means.

  The first solving means is provided with a resistor between two adjacent separators that can be energized by reducing the resistance between the separators in a low temperature state at least below the solidification temperature of water, and at least at room temperature. It is to prevent the resistor from substantially flowing electricity at the above temperature.

  The second solving means comprises a direct current power source or a secondary battery connected to each of the positive current collecting terminal and the negative current collecting terminal of the battery, and is capable of energizing the separator at a low temperature state at least below freezing point. An object of the present invention is to provide a fuel cell power generation system including the polymer electrolyte fuel cell according to item 1.

  A third solution is to use a resistance material in which the resistor has a positive temperature characteristic coefficient in the fuel cell described in the first solution.

  A fourth solution is to dispose the resistor on the outside of the gasket inserted between the two separators.

  A fifth solution is to provide a resistor having a characteristic of generating heat by energization in a low temperature state at least below the solidification temperature of water inside the cooling cell.

  The sixth solving means comprises a DC power source or a secondary battery connected to each of the positive current collecting terminal and the negative current collecting terminal of the battery, and enables the separator to be energized at least in a low temperature state below the freezing point. An object of the present invention is to provide a fuel cell power generation system including the polymer electrolyte fuel cell according to Item 5.

  A seventh solving means is that in the fuel cell described in the fifth solving means, the resistor is a resistance material having a negative temperature characteristic coefficient.

  According to the present invention, even if freezing occurs in the cells of the polymer electrolyte fuel cell, a quick start-up operation can be realized.

The cross-sectional structure of the power generation cell of this invention is shown. A cross-sectional structure when connecting two power generation cells of the present invention is shown. The structure of the cell stack and peripheral circuit of this invention is shown. The structure of the cooling cell of this invention is shown.

  In the following, typical embodiments of the present invention will be described. It is possible to replace a part of the invention with a known technique without changing the gist of the present invention.

  First, the configuration of the power generation cell (power generation cell) of the present invention will be described. FIG. 1 shows a cross-sectional structure of a power generation cell of a polymer electrolyte fuel cell. There is MEA in the center of the cross section of the power generation cell. This MEA has a three-layer structure in which the anode 101 is laminated on the upper surface of the electrolyte membrane 103 and the cathode 102 is laminated on the lower surface. The fuel-side separator 104 has a fuel channel 105 and is disposed so that the channel surface is in contact with the anode 101. The oxidant side separator 106 has an oxidant channel 107, and the channel surface is in contact with the cathode 102. A gasket 108 is provided on the outer periphery of the separator so that fuel and oxidant do not leak to the outside and one reactant does not enter the flow path of the other reactant.

  As the catalyst for the anode 101 and the cathode 102 in FIG. 1, a powder in which platinum fine particles are supported on a carbonaceous powder conductive material was used. As an example, TEC10E50E manufactured by Tanaka Kikinzoku Co., Ltd. was selected. However, it is not limited to this as long as the reaction of the fuel cell can proceed. The composition of platinum contained in the catalyst powder is 46.5% (weight percentage).

  As the electrolyte binder, a Napon solution manufactured by DuPont was used. The addition amount of the electrolyte binder was 40% with respect to the above catalyst weight.

  A paste using water as a solvent was prepared from these mixtures. This paste was mixed with a kneader so as to be sufficiently uniform. There is no particular limitation on the method, and any means can be selected as long as it is a method capable of preparing a homogeneous paste without destroying the material.

These pastes were applied to the surface of the PTFE sheet using a blade coater to prepare an electrode layer (wet state) having a predetermined thickness. The electrode was a 10 cm square (area 100 cm ² ). This was air dried and the solvent was evaporated.

  Next, an electrolyte membrane (manufactured by DuPont, Nafion 112, thickness 50 μm) was placed on the electrode layer, and the laminate was inserted between two metal plates and subjected to hot pressing. As a result, the electrode layer on the PTFE sheet is transferred to the electrolyte membrane.

The weight increase of the electrolyte membrane was measured after the transfer. From the value, the amount of Pt used per electrode unit area was calculated. Pt usage of this embodiment, 0.5~0.9mg / cm ² at the anode, the cathode in was 0.1~0.8mg / cm ^2.

  A carbonaceous porous sheet was used as a gas diffusion layer on the anode and cathode catalyst layers. A PTFE dispersion was added to the carbonaceous porous sheet to impart water repellency. The thickness of the carbonaceous porous sheet was set to 0.2 mm.

  A resistor 109 having a positive temperature characteristic according to the present invention is provided on the outer side (outer side) of the gasket 108 in FIG. The resistor 109 may be formed to a thickness that can be inserted between the separators 104 and 106. The part used as the heating element was a separator, and necessary resistance heat generation was ensured by energizing in the plane direction. Since the separator itself has excellent corrosion resistance, at least the product life is not affected.

  A plurality of separators are stacked in the cell stack, and each separator is electrically insulated by a gasket and MEA. MEA is an ionic conductor, but not an electronic conductor. Therefore, as the simplest method, it is conceivable that terminals are installed in all the separators, and each separator is individually energized to obtain the above-described resistance heat generation amount.

  However, such a method is very complicated, and the terminal connection state deteriorates and the probability of energization failure increases, which is not a preferable method.

  The present invention provides a method for allowing electricity to flow through a separator with a small number of terminals by electrically connecting at least a plurality of separators. This requires a mechanism for switching the insulation state between the separators to the energized state.

  In order to achieve this, a part that is a good electronic conductor at low temperatures and a high resistance at high temperatures (that is, at the operating temperature of the cell stack) should be mounted on the parts where gaskets are installed. I made it. The resistor having such temperature characteristics is referred to as a PTC (Positive temperature coefficient) material. By inserting a part made of PTC material between a plurality of separators, it can be operated as a switch that is turned on at low temperatures and turned off during normal power generation.

  The resistor 109 may be a very thin coating layer on the surface of the good electronic conductor, and the coating layer may be used as a switch. In the electronic good conductor, the outer periphery of the separators 104 and 106 can be formed in a convex shape, and a thin resistor 109 can be installed on the convex portion. By using such a thin resistor 109, necessary electron conductivity can be ensured at a low temperature.

  It is preferable that the resistance value in the penetration direction of the resistor 109 at the time of low temperature start is 1/10 or less, more desirably 1/100 or less of the resistance value in the in-plane direction of the separator. This is because heat generation at the separator 109 should be prioritized and heat generation at the resistor 109 needs to be minimized. This is because when the amount of heat generated by the resistor 109 increases, the temperature of the resistor 109 increases, and the resistance value of the resistor 109 increases with temperature. As a result, the resistor 109 is turned off, and substantially no electricity can flow. The resistance value of the resistor 109 can be controlled by the material and thickness of the resistor.

Specific examples of resistors include composite oxides of titanium and barium (BaTiO ₃ , (Sr _x Pb _{1 -x-0.002} Y _0.003 ) TiO _3, etc.), WO ₃ + Yb ₂ O ₃ , PbTiO ₃ series, or polyethylene resin layers There are materials mixed with carbon. In addition to these materials, any material that has a resistance that is at least below the freezing point of water is applicable.

  FIG. 2 is a diagram illustrating the function of the resistor 109 having two power generation cells stacked and having a positive temperature characteristic. The two upper and lower power generation cells are those described in FIG. The current begins to flow from the separator 106 of the lower power generation cell, and is conducted through the left resistor 109. Thereafter, the current is distributed to the two separators 104 and 106 between the two power generation cells, respectively, and reaches the resistor 109 on the right side. Here, the current is once collected, passes through the right resistor, and electricity flows in the in-plane direction of the uppermost separator 104.

  In FIG. 2, only two power generation cells are shown, but these cells are repeated up and down to form a cell stack. A positive current collecting terminal is installed at the lower end of the power generation cell, and a negative current collecting terminal is installed at the upper end, and energization is started from the positive current collecting terminal. The current begins to flow from the adjacent separator from the positive current collecting terminal, travels in the in-plane direction of the separator, and reaches the resistor 109 connected to the separator. After the current passes through the resistor, as described in FIG. 2, the current flows in the reverse direction in the separator surface and reaches the resistor 109 on the opposite side. In this way, current flows from the bottom to the top through the alternately arranged resistors 109, and finally current is collected at the negative current collecting terminal.

  The voltage applied to the positive current collecting terminal and the negative current collecting terminal is set as follows. First, resistors are connected to both current collecting terminals, and the inter-terminal resistance of the cell stack at low temperature is measured. The specific heat of the fuel cell is calculated and the required start-up time is arbitrarily determined. In addition, the temperature required for normal power generation of the fuel cell is measured, and the temperature difference from the starting start temperature is obtained.

  The electric power supplied to the battery (in watts) is a value obtained by adding the amount of heat released from the battery (in watts) to the specific heat of the battery × temperature difference / starting time and the amount of heat rising (in watts). The terminal voltage (in volts) that achieves the power is the square root of the value obtained by dividing the power supplied to the battery by the battery resistance. The voltage thus calculated is applied to the positive current collecting terminal and the negative current collecting terminal.

  When the resistance value of the resistor 109 fluctuates to a degree that cannot be ignored depending on the temperature, a voltage is calculated for each temperature and the voltage is applied to both terminals.

  When the temperature rise starts and the battery temperature reaches the temperature required for normal power generation, the fuel and the oxidant at the required flow rates are supplied to the fuel cell, and the current starts to flow. If the above-described voltage application is terminated immediately before the power generation, the heat generated by the power generation can be used for the subsequent temperature increase.

  The fuel used in the present invention is a gas containing hydrogen. The fuel is preferably 100% hydrogen in order to obtain high output or high power generation efficiency. However, as long as the catalyst of the anode 101 is not deteriorated, the fuel may be a mixed gas containing an inert gas such as nitrogen.

  Air is generally used as the oxidizing agent. A gas with increased oxygen concentration or pure oxygen may be supplied.

  The fuel or the oxidizer may start to be supplied simultaneously with the temperature raising operation in which a voltage is applied to the positive current collecting terminal and the negative current collecting terminal. In particular, since power generation partially starts with voltage application, it is desirable to supply fuel at a flow rate that is greater than or equal to the amount consumed by power generation. In this way, it is possible to prevent the anode from being deteriorated due to fuel shortage.

  Note that the supply of the oxidizing agent may be omitted. Even if the oxidant is not supplied, a small amount of oxygen contained in the cathode channel is consumed by power generation, and water is formed at the cathode, and the power generation current is attenuated. As a result, the cathode is stored in a reducing atmosphere and is not damaged at all.

  Also, since the temperature is low at the beginning of startup, the current flowing through the MEA is extremely small, but it is also possible to set the power generation start temperature, automatically set the voltage applied to both terminals to zero, and shift to the normal power generation mode It is. As a criterion for this, a correlation diagram of temperature and generated current, temperature and current flowing through the resistor 109 is created, and when the former current exceeds the latter current or exceeds a certain ratio value, What is necessary is just to control so that it may transfer to normal electric power generation mode.

  The above-described startup operation sequence is controlled by the control circuit. For example, an activation sequence including the following steps can be employed.

  First, the battery environmental temperature is measured. At this time, it is determined whether or not the battery temperature is below freezing point.

  When it is determined that the temperature is below the freezing point, the cold start mode is executed. In the cold start mode, power is supplied from a DC power source or a secondary battery (storage battery) to the positive current collecting terminal and the negative current collecting terminal, and a voltage is applied between the terminals. A power system may be used as a power supply source, and any power device such as a solar power generation or a capacitor can be used.

  Apply voltage and monitor temperature. At this time, power may be supplied continuously or intermittently (intermittent energization).

  After confirming that the set temperature has been reached, the cold start mode is terminated. That is, the supply of power between both terminals is stopped. Usually, power generation is possible when the temperature exceeds 0 ° C., so it is desirable to set the set temperature in the range of 0 ° C. to 20 ° C.

  Next, it shifts to the normal power generation mode. At that time, fuel and oxidant are supplied to the fuel cell, and normal power generation is started. The current value for power generation is set to a value corresponding to the temperature. In general, the current is reduced at low temperatures and close to the rated current value at high temperatures.

  FIG. 3 shows a system configuration for realizing such start-up operation and a cross-sectional structure of the fuel cell. This is an example of a 1 kW class PEFC cell stack.

  The MEA manufactured by the method described above was sandwiched between two graphite separators 304 per MEA, and the power generation cell 301 was assembled.

  When sandwiching the MEA 302 between the two separators 304, the gasket 305, the electrolyte membrane portion of the MEA, and the gasket 305 were laminated in this order and pressed to prevent leakage of fuel and oxidant.

  Both the anode and the cathode are composed of a catalyst layer and a gas diffusion layer as shown in FIGS. The catalyst layer of the present invention may be applied to the electrolyte membrane, or may be substituted by applying thermocompression to the electrolyte membrane after being applied to the gas diffusion layer.

  A plurality of power generation cells 301 are connected in series, current collecting terminals 313 and 314 are installed at both ends, and further tightened with an end plate 309 from the outside via an insulating plate 307. If the end plate is an insulating material, the insulating plate 307 can be omitted. Bolts 316, springs 317, and nuts 318 are used as fastening parts. The current collecting terminals 313 and 314 can be made of a conductive material such as a metal plate or a graphite plate.

  In the separator having the cooling water flow path, the cooling water flows with the flow path surfaces facing each other. This is referred to as a cooling cell 308. One cooling cell 308 is provided for every two power generation cells 301. In FIG. 3, a cooling water flow path is formed in the terminal separator in contact with the current collecting terminals 313 and 314. Therefore, a flat plate member 303 made of a graphite plate was inserted so that the cooling water flow path and the current collector plate were in direct contact and the current collector plate was not corroded.

  Fuel is supplied from a fuel supply connector 310 provided on the left end plate 309, passes through each power generation cell 301, and is oxidized on the anode of the MEA. The fuel exhaust gas that has passed through the power generation cell 301 is discharged from a fuel discharge connector 322 provided on the opposite end plate 309. In this example, pure hydrogen was used as the fuel. However, if the concentration of hydrogen is higher than 20% and the diluent gas is an inert gas such as nitrogen, a low concentration of hydrogen gas can be used.

  Similarly, the oxidant is supplied from the oxidant supply connector 311 provided on the left end plate 309 shown in FIG. 3 and discharged from the oxidant discharge connector 323 of the opposite end plate 309. As the oxidant, a gas having a higher oxygen concentration (21%) in the air is used. If the oxygen in the oxidizer is set to a high concentration of 30% or more, the hydrogen concentration of the fuel does not become 30% or less, and therefore a decrease in cell voltage can be suppressed.

  The cooling water is supplied from a cooling water supply connector 312 provided on the end plate 309 and flows to the cooling cell 308 or a cooling cell adjacent to the current collector plate. After passing through the cooling cell and taking heat away, the cooling water is discharged from the cooling water discharge connector 324 of the opposite end plate 309. The cooling water discharged from this is removed by the cold water in a heat exchanger (not shown) and supplied again to the cooling water supply connector 312. A pump was used to circulate the cooling water.

  A cell stack composed of 50 power generation cells 301 was manufactured with such a component structure. In FIG. 3, when components for 50 cells are described, the components are too fine, so that the number of cells is reduced to avoid it. The cell stack (solid polymer fuel cell) of this example is designated as S1.

  The cell stack S1 can draw power lines 319 from current collecting terminals 313 and 314 and supply power to an external load 321 via a converter 320 formed of a DC-DC converter or a DC-AC converter. This is a circuit configuration used during normal power generation.

  The resistor 330 having the positive temperature characteristic of the present invention is arranged so that the power generation cells 301 are alternately connected and all the separators are connected in series.

  In the low temperature start mode, the switch 325 is switched to operate the DC power source 326. The DC power source 326 can apply a voltage between the positive current collecting terminal 314 and the negative current collecting terminal 313 to flow electricity inside the cell stack. In this way, the inside of the cell stack can be directly heated at a low temperature.

  The cell stack temperature can be measured by inserting a thermocouple into the separator with the groove processed or by attaching it to the side surface of the separator. Instead of a thermocouple, other temperature sensors such as a thermistor can be used.

  FIG. 4 shows a method for attaching a resistor 414 having negative temperature characteristics to the cooling cell 308 of FIG. 3 so that the cooling cell can also generate heat. The cooling cell is configured with separators 410 and 420 facing each other.

  The cooling water is supplied from the cooling water supply manifold 417 and flows through the cooling water flow surface 421. The flow path surface 421 is provided with three convex portions (also referred to as ribs) 422. The cooling water flows from the cooling water supply manifold 417 to the cooling water discharge manifold 418 while avoiding the convex portion 422. In FIG. 4, a fine channel is not formed, but the channel surface 423 may form any channel such as a straight channel, a meandering channel, or a looped channel. The negative temperature characteristic resistor 414 of the present invention is accommodated in the concave portion 413 on the left surface. When the separators 410 and 420 of the cooling cell are brought into close contact with each other, they are pressure-bonded at the convex portion 422 and are electrically connected from the separator 410 to the resistor 414, the convex portion 422, and the separator 420.

  Examples of the material of the negative temperature characteristic resistor 414 of the present invention include spinel Mn—Co—Ni—Cu and Mn—Ni—Cr oxides. Any material can be selected as long as it has a high temperature resistance in the low temperature startup mode and has a temperature characteristic that does not substantially cause a voltage loss in the normal power generation mode.

  The area and thickness of the resistor 414 are selected according to the material used. The most important requirement is to avoid voltage loss during normal power generation. That is, since the voltage per power generation cell is about 0.5 to 0.8 V, if this voltage is suppressed to a voltage loss of 1/10 or less, more preferably 1/100 or less, The voltage loss due to the resistor 414 can be reduced to the output loss of the fuel cell in the range of 1/10 to 1/100, or 1/100 or less. In order not to increase the length of the cell stack, it is desirable that the thickness of the resistor is as small as possible.

  The cooling cell of FIG. 4 is formed with a manifold through which fuel and oxidant pass. There are a supply manifold 411 and a discharge manifold 419 for fuel, and a supply manifold 415 and a discharge manifold 416 for oxidant. Even if either the fuel or the oxidizer is used upside down on the supply side and the discharge side, the effect of the present invention is not affected.

  If the cooling cell having the configuration shown in FIG. 4 is replaced with the cooling cell 308 shown in FIG. 3, in addition to the heat generated by energizing the separator at the time of low temperature startup, the heat generated in the cooling cell can be used for increasing the temperature. Temperature increase is possible.

DESCRIPTION OF SYMBOLS 101 Anode 102 Cathode 103 Electrolyte membrane 104 Separator having fuel flow path 105 Fuel flow path 106 Separator having oxidant flow path 107 Oxidant flow path 108 Gasket 109, 330 Resistor 301 having positive temperature characteristics Power generation cell 302 Membrane-electrode Assembly (MEA)
303 Flat plate member 304 facing cooling water flow path 304 Separator of the present invention (for power generation cell)
305 Gasket (seal)
307 Insulating plate 308 Cooling cell 309 End plate 310 Fuel supply connector 311 Oxidant supply connector 312 Cooling water supply connector 313, 314 Current collecting terminal 316 Bolt 317 Spring 318 Nut 319 External power line 320 DC-DC converter or inverter 321 External Load 322 installed in the connector 323 for discharging the fuel oxidizer connector 324 for discharging the coolant 410 Separator 411 for storing the resistor Fuel supply manifold 413 Recessed portion 414 for storing the resistor 415 having a negative temperature characteristic Oxidant Supply Manifold 416 Oxidant Discharge Manifold 417 Cooling Water Supply Manifold 418 Cooling Water Discharge Manifold 419 Fuel Discharge Manifold 420 Separator 421 Forming Cooling Water Flow Channel Cooling Water Channel Surface 422 Convex (rib)

Claims (7)

A separator having an anode channel for circulating fuel, a separator having a cathode channel for supplying an oxidant, and a membrane-electrode assembly comprising two electrodes and an electrolyte membrane, the membrane-electrode assembly being In a fuel cell having a power generation cell sandwiched between the separators,
A resistor is provided between two adjacent separators that can be energized by reducing the resistance between the separators in a low temperature state at least below the solidification temperature of water,
The polymer electrolyte fuel cell, wherein the resistor does not substantially conduct electricity at least at a temperature of room temperature or higher.   2. The solid polymer according to claim 1, further comprising a DC power source or a secondary battery connected to each of a positive current collecting terminal and a negative current collecting terminal of the battery, wherein the separator can be energized at least at a low temperature below a freezing point. Fuel cell power generation system equipped with a fuel cell.   2. The polymer electrolyte fuel cell according to claim 1, wherein the resistor is a resistance material having a positive temperature characteristic coefficient.   2. The polymer electrolyte fuel cell according to claim 1, wherein the resistor is disposed on the outside of a gasket inserted between two separators. A separator having an anode channel for circulating fuel, a separator having a cathode channel for supplying an oxidant, and a membrane-electrode assembly comprising two electrodes and an electrolyte membrane, the membrane-electrode assembly being In a fuel cell having a power generation cell sandwiched between separators and a cooling cell comprising a separator having a water flow path for circulating cooling water, the cooling cell being arranged adjacent to the power generation cell,
A solid polymer fuel cell characterized in that a resistor having a characteristic of generating heat when energized at least in a low temperature state below the solidification temperature of water is provided inside the cooling cell.   6. The solid polymer according to claim 5, further comprising a DC power source or a secondary battery connected to each of the positive current collecting terminal and the negative current collecting terminal of the battery, wherein the separator can be energized at least at a low temperature below the freezing point. Fuel cell power generation system equipped with a fuel cell.   6. The polymer electrolyte fuel cell according to claim 5, wherein the resistor is a resistance material having a negative temperature characteristic coefficient.

Images