JP4556375B2 - Fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell system, and more particularly to a fuel cell system that facilitates warm-up from a low temperature.
[0002]
[Prior art]
In the polymer electrolyte fuel cell, the temperature range where power can be generated most efficiently is about 50 ° C. to 80 ° C. Further, at a temperature lower than these temperature ranges, the power generation efficiency is extremely low. Therefore, in order to obtain sufficient power from the fuel cell after operating the fuel cell, it is necessary to warm up until the temperature reaches the high efficiency region, and until the entire load is started by obtaining power from the fuel cell. It takes a long time.
[0003]
On the other hand, when the temperature of the fuel cell is below freezing point, there is a problem that the generated water generated by the power generation reaction freezes on the electrode surface, the supply of oxygen is hindered, and the power generation reaction is suppressed.
Therefore, conventionally, for example, as described in Japanese Patent Application Laid-Open No. 7-94202, a device provided with a warming-up system for warming up the fuel cell itself before the start of power generation of the fuel cell has been proposed. .
[0004]
[Problems to be solved by the invention]
However, such a fuel cell warm-up system requires energy for warm-up, and has a problem of deteriorating the overall energy efficiency of the system.
Further, in order to incorporate the warm-up system into the fuel cell system, the size of the fuel cell system has been increased.
[0005]
In addition, a mobile fuel cell mounted on a moving body such as a vehicle is in an environment in which the mounting space is small and energy cannot be supplied from an external system, and the above disadvantage becomes a more disadvantageous element.
In addition, when fuel gas is supplied for power generation, the gas discharged from the fuel cell takes heat from the fuel cell, which hinders warm-up.
An object of the present invention is to provide a fuel cell system capable of self-warming.
[0006]
[Means for Solving the Problems]
The above object is achieved by the present invention described below.
(1) A fuel cell stack including a plurality of fuel cells in which a solid polymer electrolyte is sandwiched between an oxygen electrode and a fuel electrode, and a conductive separator interposed between adjacent fuel cells,
A fuel holding unit for holding the fuel gas in a state where the fuel gas can come into contact with the fuel electrode;
Fuel introduction means for introducing fuel gas to the fuel holding portion;
Fuel deriving means for discharging fuel gas from the fuel holding portion;
An exhaust solenoid valve provided in the fuel deriving means;
Communicating means for communicating the fuel introducing means and the fuel deriving means;
A circulation pump that is provided in the communication means and discharges gas toward the fuel introduction means;
Fuel supply means for supplying fuel gas to the fuel holding portion via the fuel introduction means;
Temperature detecting means for detecting the temperature of the fuel cell;
When the detected value of the temperature detecting means is less than a predetermined temperature at the start of fuel supply, the circulation pump is stopped, the exhaust electromagnetic valve is closed, and the fuel holding portion is maintained in the fuel holding portion. And a control means for driving the circulation pump when the temperature becomes higher than the temperature.
[0007]
(2) The fuel cell system according to (1), wherein the temperature detection unit detects a temperature of a fuel cell located at an end of the fuel cell stack.
[0008]
(3) The fuel cell system according to (1) or (2), wherein the separator is made of metal.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the fuel cell system 100 of the present invention will be described in detail with reference to the accompanying drawings. 1 is an overall perspective view of a fuel cell stack 1 included in a fuel cell system 100 of the present invention, FIG. 2 is a partial cross-sectional side view of the fuel cell stack 1, and FIG. The fuel cell stack 1 of the present invention includes a power generation unit 61 having a fuel cell unit cell 2 and a separator 3. The fuel cell unit cell 2 has a configuration in which a solid polymer electrolyte membrane 23 is sandwiched between an oxygen electrode 21 and a fuel electrode 22. The separator 3 has current collecting members 31 and 32 for contacting the oxygen electrode 21 and the fuel electrode 22 to extract current from the outside. As shown in FIGS. 2 and 3, the unit cells 2 and the separators 3 are alternately stacked to constitute the power generation unit 61.
[0010]
The current collecting members 31 and 32 are each made of a material having conductivity and corrosion resistance. For example, the current collecting members 31 and 32 are made of a metal material. In order to fulfill the function as a current collecting member, this constituent metal is conductive and has a corrosion resistance because it is in an energized state. For example, stainless steel, nickel alloy, titanium alloy or the like subjected to corrosion-resistant conductive treatment can be used. Here, the corrosion-resistant conductive treatment includes, for example, gold plating. Further, as the constituent material of the current collecting members 31 and 32, a material having conductivity and corrosion resistance such as carbon black may be used in addition to the metal. Moreover, since the separator 3 can be thinly formed by forming the metal plate thin by pressing, the size of the fuel cell stack 1 itself can be reduced, and the heat capacity can be reduced. This also allows the fuel cell stack 1 to be easily heated.
[0011]
The current collecting member 31 is in contact with the oxygen electrode 21, and the current collecting member 32 is in contact with the fuel electrode 22. As shown in FIG. 2 and FIG. 3, a plurality of convex portions 311 that are continuously raised in a straight line are formed at equal intervals on the surface of the current collecting member 31 that contacts the oxygen electrode 21. A groove 312 is formed between the portions 311. That is, the convex part 311 and the groove | channel 312 are the shapes arrange | positioned alternately. The convex portion 311 is a contact portion 313 in which the flat portion of the peak that protrudes most is in contact with the oxygen electrode 21, and the oxygen electrode 21 can be energized through the contact portion 313. An airflow passage 315 through which air flows is formed by the groove 312 and the surface of the oxygen electrode 21.
[0012]
Grooves 314 and 314 are formed at both ends of the convex portion 311 in a direction orthogonal to the convex portion 311, and an air flow path 316 is formed by the groove 314 and the surface of the oxygen electrode 21. The plurality of air flow passages 315 are configured to communicate with the air flow path 316 at both ends, respectively, and air that supplies oxygen to the oxygen electrode 21 through the plurality of air flow passages 315 and the pair of air flow paths 316. A holding unit is configured.
[0013]
An air supply hole 318 and an air discharge hole 317 are formed in the air holding part, and air flows into the air holding part from the air supply hole 318 and flows out from the air discharge hole 317. In this way, the air in the air holding unit is configured to constantly change. In this embodiment, the current collecting member 31 is rectangular, and the air supply hole 318 and the air discharge hole 317 are in a point-symmetrical position (diagonal direction) about the centroid in a plan view of the current collecting member 31. Each is arranged. FIG. 2 shows an air discharge hole 317. FIG. 3 also shows an air supply hole 318.
[0014]
On the surface of the current collecting member 32 that comes into contact with the fuel electrode 22, a plurality of convex portions 321 that are continuously raised linearly are formed at equal intervals, and a groove 322 is formed between the convex portions 321. The That is, the convex part 321 and the groove | channel 322 are the shapes arrange | positioned alternately. The convex portion 321 is a contact portion 323 in which the flat portion of the peak that protrudes most is in contact with the surface of the fuel electrode 22, and the fuel electrode 22 can be energized through the contact portion 323. A hydrogen flow passage 325 through which hydrogen flows is formed by the groove 322 and the surface of the fuel electrode 22.
[0015]
Grooves 324 and 324 are formed at both ends of the convex portion 321 in a direction orthogonal to the convex portion 321, and a hydrogen flow path 326 is formed by the groove 324 and the surface of the fuel electrode 22. The plurality of hydrogen flow passages 325 are configured to communicate with the hydrogen flow path 326 at both ends, respectively, and the fuel that supplies hydrogen to the fuel electrode 22 through the plurality of hydrogen flow passages 325 and the pair of hydrogen flow paths 326. A holding unit is configured.
[0016]
A hydrogen supply hole and a hydrogen discharge hole 327 are formed in the fuel holding part, and hydrogen flows into the fuel holding part from the hydrogen supply hole and flows out from the hydrogen discharge hole 327. In this way, the hydrogen in the fuel holding unit is constantly replaced. In this embodiment, the current collecting member 32 is rectangular, and the hydrogen supply hole and the hydrogen discharge hole 327 are respectively point-symmetrical (in the diagonal direction) about the centroid in plan view of the current collecting member 32. Has been placed. FIG. 2 shows a hydrogen discharge hole 327.
[0017]
On the surface of the current collecting member 32 opposite to the fuel electrode 22, a plurality of convex portions 421 bulging continuously in a straight line are formed at equal intervals, and a groove 422 is formed between the convex portions 421. Each is formed. That is, the convex part 421 and the groove | channel 422 become the shape arrange | positioned alternately. The convex part 421 is a contact part 423 in which the flat part of the peak that protrudes most is in contact with the surface of the current collecting member 31, and the fuel electrode 22 and the oxygen electrode 21 of the unit cell 2 adjacent to each other through the contact part 423. Are electrically connected. A water flow passage 425 through which water flows is formed by the groove 422 and the flat surface of the current collecting member 31.
[0018]
Grooves 424 and 424 are formed at both ends of the convex portion 421 in a direction orthogonal to the convex portion 421, and a water flow path 426 is formed by the groove 424 and the flat surface of the current collecting member 31. The plurality of water flow passages 425 are configured to communicate with the water flow path 426 at both ends, and the plurality of water flow passages 425 and the pair of water flow paths 426 form a cooling unit.
[0019]
A water supply hole and a water discharge hole 427 are formed in the cooling part, and water as a refrigerant flows into the cooling part from the water supply hole and flows out from the water discharge hole 427. As described above, the water in the cooling unit can be replaced. In this embodiment, the current collecting member 32 is rectangular, and the water supply hole and the water discharge hole 427 are respectively point-symmetrical (diagonal direction) about the centroid in plan view of the current collecting member 32. Has been placed. By providing the water supply hole and the water discharge hole 427 at such a position, the water in the cooling unit can be exchanged uniformly. A water discharge hole 427 is shown in FIGS. The cooling medium may be water or an antifreeze liquid.
[0020]
In the fuel cell stack 1, a conduction path is formed in the stacking direction of the separators 3 to conduct air, hydrogen, and water. Each of the conduction paths has a supply conduction path and a discharge conduction path. As shown in FIG. 1, the supply air conduction path 51, the hydrogen conduction path 53, and the water conduction path 55 are collectively arranged on one side of the fuel cell stack 1, and the discharge air conduction path 52, hydrogen The conduction path 54 and the water conduction path 56 are arranged on the opposite side to the side on which the supply conduction path is arranged, and are configured to sandwich the air holding unit, the fuel holding unit, and the cooling unit therebetween. Yes.
[0021]
Therefore, the discharge air conduction path 52 communicates with the air discharge hole 317 of each air holding part, and the supply air conduction path 51 communicates with the air supply hole of each air holding part. In this way, the supply air conduction path 51 functions as an air manifold that distributes air to each air holding portion.
Further, the discharge hydrogen conduction path 54 communicates with the hydrogen discharge hole 327 of each fuel holding part, and the supply hydrogen conduction path 53 communicates with the hydrogen supply hole of each fuel holding part. In this way, the hydrogen supply passage 53 for supply functions as a fuel manifold that distributes hydrogen to each fuel holding portion.
Further, the discharge water conduction path 56 communicates with the water discharge hole 427 of each cooling section, and the supply water conduction path 55 communicates with the water supply hole of each water holding section. In this way, the water supply passage 55 for supply functions as a water manifold that distributes water to each water holding portion.
[0022]
At both ends of the power generation unit 61 configured as described above, current collectors 63a and 63b, insulating members 64a and 64b, end portions are provided outward from the end separator 3 in the stacking direction of the separator 3 and the unit cell 2. Plates 65a and 65b are respectively connected to both sides. Each of these stacked members and the power generation unit 61 are integrally held by a holding member 66 attached to the opposing side surfaces. The current collectors 63 a and 63 b are provided with terminals 67 a and 67 b as terminals of the fuel cell stack 1.
[0023]
Each end plate 65a is connected to each path of an air supply system 11, a hydrogen supply system 12, and a cooling system 13, which will be described later. Specifically, the air supply path 110 of the air supply system 11 is connected to the supply air conduction path 51, the air discharge path 111 is connected to the discharge air conduction path 52, and the supply path 122 of the hydrogen supply system 12 is supplied. The hydrogen passage 53, the discharge passage 123 are connected to the discharge hydrogen passage 54, the coolant supply passage 133 of the cooling system 13 is connected to the water passage 55 for supply, and the coolant discharge passage 131 is for discharge. The water conduction paths 56 are respectively connected.
[0024]
Next, the configuration of the fuel cell system 100 using the fuel cell stack 1 will be described. FIG. 4 is a schematic diagram showing the configuration of the fuel cell system 100. The fuel cell system 100 is mounted on an electric vehicle, which is one of moving bodies, and constitutes a power source for a drive motor 143 together with a load system power storage means (capacitor or the like) 146 to be described later. The fuel cell system 100 includes an air supply system 11 that supplies air to the fuel cell stack 1, a hydrogen supply system 12 that supplies hydrogen as fuel gas, and a cooling system 13 that also supplies coolant. The load system 14 and a humidification system 15 for supplying moisture to the oxygen supply system 11 are provided.
[0025]
The air supply system 11 includes an air supply path 110 and an air discharge path 111. In the air supply path 110, in order from the upstream side, a filter 112 that removes impurities such as dust from the outside air, an outside air temperature sensor S1, an air supply fan 113 that adjusts the supply amount of air, and a humidifier 151 that humidifies the supplied air. Are connected, and finally the supply air conduction path 51 of the fuel cell stack 1 is connected.
[0026]
An upstream end of the air discharge path 111 is connected to the discharge air conduction path 52 of the fuel cell stack 1, and an air outlet temperature sensor S3 for measuring the representative temperature of the fuel cell stack in order toward the downstream, an air supply system Is connected to a condenser 152 that collects water removed from the oxygen electrode 21 and a filter 115 that prevents impurities from flowing back from outside air and enter the fuel cell stack. Is discharged. As described above, the air supply system 11 feeds air into the air holding unit provided in the fuel cell stack 1 and supplies oxygen in the air to the oxygen electrode 21. The oxygen supply means includes an air supply path 110 and an air supply fan 113. The oxygen supply amount is adjusted by adjusting the discharge amount from the air supply fan 113. The discharge amount is adjusted by adjusting the number of blade rotations.
[0027]
The humidification system 15 includes a humidifier 151 that adds humidity to the air supplied to the fuel cell stack 1, a condenser 152 that recovers moisture from the discharged air, a humidified water tank 150, and humidified water from the humidified water tank 150. Is supplied to the humidifier 151, a humidifying water pump 154 for sending the humidifying water to the humidifier 151, a downstream of the humidifying water pump 154, and recovered by the electromagnetic valve 155 and the condenser 152. A recovery path 156 for recovering water to the humidified water tank 150, a recovery pump 157 for sending the recovered water to the humidified water tank 150, an antifreezing heater 150 a provided in the humidified water tank 150, and the humidified water tank 150 A humidifying water temperature sensor S4 for detecting the temperature of the humidifying water, and a humidifying water level sensor S5 for detecting the water level.
[0028]
Further, the water supply path 153 and the recovery path 156 are provided with filters 158 and 159 for removing impurities, respectively. The electromagnetic valve 155 is closed when the pump 154 is not driven, and prevents the flow of water in the path. The humidification system 15 is provided to humidify the air sent to the fuel cell stack 1. The air humidified by the humidifier 151 of the humidification system 15 maintains the oxygen electrode 21 of the fuel cell stack 1 in a wet state (a state moistened with moisture).
[0029]
The hydrogen supply system 12 includes a high-pressure hydrogen container 121 as a hydrogen storage container, a hydrogen supply path 122 that supplies hydrogen from the high-pressure hydrogen container 121 to the supply hydrogen conduction path 53 of the fuel cell stack 1, and the fuel cell stack 1. A hydrogen discharge path 123 that discharges hydrogen from the discharge hydrogen conduction path 54 to the outside, and a communication path 161 that is a communication unit that connects the hydrogen supply path 122 and the hydrogen discharge path 123 are provided. The hydrogen supply path 122 is connected to a hydrogen filling port 124 for charging hydrogen into the high-pressure hydrogen container 121 from an external hydrogen source, and a hydrogen primary pressure sensor S6 for measuring the hydrogen pressure in the high-pressure hydrogen container 121. Are connected, and a hydrogen pressure regulating valve 125 for adjusting the pressure (amount) of hydrogen supplied to the fuel electrode, a hydrogen supply electromagnetic valve 126 for controlling the hydrogen supply amount, and hydrogen for measuring the hydrogen pressure applied to the fuel electrode The secondary pressure sensor S7 is connected in order toward the downstream. The hydrogen pressure regulating valve 125 and the hydrogen supply electromagnetic valve 126 are controlled based on the detection value of the hydrogen secondary pressure sensor S7. Further, a check valve 127 for preventing a back flow and a hydrogen exhaust electromagnetic valve 128 for controlling the discharge of hydrogen are connected to the hydrogen discharge path 123 in order toward the downstream. Hydrogen may be supplied continuously during operation or may be supplied intermittently.
[0030]
In the communication path 161, a check valve 162, a filter 163, and a circulation pump 164 are provided in order from the end connected to the hydrogen discharge path 123. Gas is discharged from the circulation pump 164 toward the connection end with the hydrogen supply path 122. The check valve 162 prevents inflow of hydrogen from the hydrogen supply path 122 directly into the hydrogen discharge path 123. The filter 163 removes impurities from the circulating hydrogen gas. The communication path 161, the supply hydrogen conduction path 54, the fuel holding portion in the fuel cell stack, and the hydrogen discharge path 123 constitute a circulation path. The circulation pump 164 has a function of circulating hydrogen gas in the circulation path. The hydrogen supply path 122 and the supply hydrogen conduction path 53 function as fuel introduction means, and the hydrogen discharge path 123 and the discharge hydrogen conduction path 54 function as fuel discharge means. The hydrogen supply electromagnetic valve 126 and the high-pressure hydrogen container 121 function as hydrogen supply means.
[0031]
The cooling system 13 is arranged to prevent the fuel cell stack 1 from heating up at a high temperature, and circulates and circulates a coolant as a cooling medium in the fuel cell stack 1. To cool. In this embodiment, an antifreeze liquid is used as the cooling liquid, for example, an ethylene glycol aqueous solution is used. In addition, water or other heat medium can be used as the coolant. The temperature of the fuel cell stack 1 can be detected by, for example, a temperature sensor S11 attached to the fuel cell stack 1. A sensor S11 that detects the temperature of the fuel cell stack 1 functions as a temperature detection unit that detects the temperature of the fuel cell.
[0032]
The cooling system 13 is configured based on a cooling liquid discharge path 131, a radiator 132, and a cooling liquid supply path 133 connected to the discharge-side water conduction path 56 of the fuel cell stack 1, and the cooling liquid is the cooling liquid supply path. The circulation pump 134 disposed at 133 is fed into the supply-side water conduction path 55 of the fuel cell stack 1. In addition, a radiator bypass path 135 that bypasses the radiator 132 is connected between the coolant discharge path 131 and the coolant supply path 133.
[0033]
Control of opening and closing of the solenoid valves SV1 and SV3 according to the temperature of the coolant detected by the coolant outlet temperature sensor S9 and the coolant inlet temperature sensor S10 disposed in the coolant discharge path 131 and the coolant supply path 133, respectively. Then, the flow of the coolant in the cooling system 13 is controlled. The radiator 132 is provided with a fan 132a, and the cooling capacity can be adjusted by adjusting the air volume of the fan.
[0034]
As described above, the cooling system 13 operates to prevent overheating due to reaction heat of the fuel cell during normal power generation of the fuel cell. In this case, the cooling system 13 uses a circulation system including a cooling liquid discharge path 131, a radiator 132, a cooling liquid supply path 133, and a circulation pump 134 disposed in the cooling liquid supply path 133. Therefore, in this case, the electromagnetic valve SV1 is open and the electromagnetic valve SV3 is closed. The coolant passes through the coolant supply path 133, the supply side water conduction path 55 of the fuel cell stack 1, the cooling part of each separator 3, and the discharge side water conduction path 56. From the path 131, it reaches the radiator 132, is cooled by the radiator 132, returns to the circulation pump 134 through the electromagnetic valve SV1. The cooling capacity of the radiator 132 is adjusted according to the difference between the temperature of the coolant detected by the coolant inlet temperature sensor S10 and the temperature of the discharged coolant detected by the coolant outlet temperature sensor S9. The discharge amount of the pump 134 is adjusted to maintain the fuel cell stack 1 at an appropriate temperature.
[0035]
The load system 14 is connected to the fuel cell stack 1. The output cord 147 of the load system 14 is connected to terminals 67a and 67b, respectively, and the output cord 147 supplies power to the motor 143 via an output relay 144 and an inverter 142 that supply and cut off power to the load. The output cord 147 is provided with a diode 148 and a current sensor S2 that prevent reverse current. An auxiliary power source 146 is connected between the output relay 144 and the inverter 142 via an output control circuit 145. Further, a voltage sensor S8 for detecting the output of the fuel cell stack 1 is connected to the output cord 147 in parallel.
[0036]
The auxiliary power source is, for example, a power storage device such as a battery or a capacitor, stores the regenerative power of the motor 143 at a low vehicle speed, and when the output from the fuel cell stack is insufficient at the time of acceleration or high load, To supply power. The output control circuit 145 controls the ratio of the output of the fuel cell stack 1 and the auxiliary power supply 146 with respect to the power supplied to the motor 143. The voltage sensor S8 functions as voltage detection means.
[0037]
FIG. 5 is a block diagram illustrating a control circuit that performs control at the start of power generation in the fuel cell system 100. The control unit 74 is supplied with the detection value of the current sensor S2, the detection value of the voltage sensor S8, and the detection value of the temperature sensor S11. The control unit 74 also starts and stops the air supply fan 113, opens and closes the hydrogen supply electromagnetic valve 126, opens and closes the hydrogen exhaust electromagnetic valve 128, turns on and off the relay 144, and starts and stops the circulation pump. To control each.
The control unit 74 controls the supply of hydrogen gas and the circulation of the hydrogen gas in accordance with the temperature and output voltage of the fuel cell stack 1 to adjust the warm-up efficiency of the fuel cell stack 1 to increase. .
[0038]
Hereinafter, the operation of the fuel cell system 100 will be described based on the flowcharts shown in FIGS. 6 and 7.
First, the main flow chart (FIG. 6) when the fuel cell system 100 is started, that is, when the power generation operation is started will be described. First, the state of the entire system is checked. If no abnormality is detected, air supply is started (step S101). Air supply is started by driving the air supply fan 113. Air is supplied from the air supply system 11 to the fuel cell stack 1 by the operation of the air supply fan 113.
[0039]
Next, a hydrogen replacement purge process is performed (step S103). The hydrogen replacement purge process is a process of discharging a gas other than hydrogen gas filled in the fuel holding unit in the fuel cell stack 1 and filling the fuel holding unit with hydrogen gas in a stopped state. FIG. 7 shows a flowchart of the hydrogen replacement purge process as a subroutine. In the hydrogen replacement purge process, the hydrogen supply solenoid valve is opened (step S201). Thereby, the hydrogen supply path 122 and the high-pressure hydrogen container 121 communicate with each other. Next, the hydrogen exhaust solenoid valve 128 is opened (step S203). As a result, the high-pressure hydrogen container 121, the hydrogen supply path 122, the fuel cell stack 1, and the hydrogen discharge path 123 communicate with each other, and the hydrogen gas is in this order in the fuel cell stack 1, that is, in the fuel holding portion. The gas is filled into the fuel holding portion while extruding the gas to the outside.
[0040]
The value of the voltage sensor S8 is monitored to determine whether it is greater than the set voltage A (step S205). When the hydrogen gas concentration in the fuel holding unit increases due to the start of the supply of hydrogen gas, the output voltage of the fuel cell stack 1 also increases. Therefore, when this output voltage reaches a set voltage or higher, the hydrogen gas concentration has a sufficient value. It can be judged that The set voltage A means that the hydrogen gas concentration has reached a concentration necessary for generating electric power to be supplied to the load.
Therefore, if the set voltage A is not reached, steps S201 and S203 are repeated until the set voltage A is reached. When the set voltage A is reached, the hydrogen gas concentration has sufficiently increased, so the hydrogen exhaust solenoid valve is closed (step S207) and the process returns.
[0041]
Next, the output relay is turned on (step S105). As a result, the output of the fuel cell stack 1 is supplied to the load system 14. The temperature of the fuel cell stack 1 is acquired from the temperature sensor S11, and it is determined whether the value is larger than the set temperature (step S107). The set temperature is set to a value close to that value centering on the highest value within the temperature range in which the reaction product water freezes at the start of power generation. For example, such a temperature is set to 5 degrees Celsius. be able to. This set temperature may be set to a value close to the other temperature, for example, the lowest value (for example, 50 degrees Celsius) in the temperature range where the power generation efficiency is highest. Or you may set to the value close | similar to the value centering on the lowest value in the optimal temperature range required in order to obtain the output for driving a load. The present invention has an effect that, at the time of starting, the time until the temperature of the fuel cell stack 1 reaches the set temperature is shortened.
[0042]
If the temperature of the fuel cell stack 1 is lower than the set temperature, the reaction product water may freeze during power generation. Therefore, the hydrogen exhaust solenoid valve 128 is kept closed. Thereby, hydrogen gas stays in the fuel holding part of the fuel cell stack 1 and stays there. Since the supply of unwarmed hydrogen gas to the fuel cell stack 1 is stopped, and the outflow of the hydrogen gas from the fuel cell stack 1 is eliminated, the hydrogen gas takes heat from the fuel cell stack 1, thereby Heat discharge to the is suppressed. During this time, the hydrogen gas staying in the fuel holding portion reacts with the oxygen in the air supplied by the air supply fan 113 to generate power. At the same time, heat is generated by the power generation reaction. The fuel cell stack 1 is warmed up by this heat.
This state is maintained until the temperature of the fuel cell stack 1 becomes higher than the set temperature. When the temperature becomes higher than the set temperature, the circulation pump 164 is turned on (step S109), and thereafter normal operation is started.
[0043]
Here, in the state where the fuel cell stack 1 is warmed up (the determination is No in step S107), the following operation can be added.
When the temperature of the fuel cell stack 1 is lower than the set temperature, the hydrogen concentration in the hydrogen gas in the fuel holding unit decreases due to the continuation of the power generation reaction. In this state, the supply of hydrogen gas is cut off, so the hydrogen concentration decreases and the output voltage from the fuel cell stack 1 decreases. Therefore, it is determined whether the output voltage of the fuel cell stack 1 is lower than the set voltage B. The set voltage B is set to a value smaller than the set voltage A. If it is higher than the set voltage B, step S107 is executed again, and the state where hydrogen gas stays in the fuel holding unit is maintained. When the voltage is lower than the set voltage B, the circulation pump 164 is driven to start hydrogen circulation in the circulation path.
[0044]
Immediately before the start of circulation, the hydrogen gas concentration in the fuel holding portion is reduced due to the power generation reaction, but stays in the hydrogen supply path 122, the hydrogen discharge path 123, the communication path 161, etc. that constitute the circulation path. The hydrogen concentration is not so low. Therefore, by circulating the hydrogen gas in the circulation path, a gas having a high hydrogen gas concentration is mixed to increase the hydrogen gas concentration in the fuel holding unit. In addition, since the gas once in contact with the fuel electrode is repeatedly contacted, hydrogen can be reacted in a state where the hydrogen gas concentration is reduced, and the fuel consumption efficiency can be improved without wasting hydrogen. Can be improved.
[0045]
Furthermore, as the power generation reaction proceeds, the hydrogen gas concentration further decreases, and the output voltage of the fuel cell stack 1 decreases. Therefore, it is further determined whether the output voltage of the fuel cell stack 1 is lower than the set voltage C. Here, the set voltage C is set to a value smaller than the set voltage B. The set voltage C is set to a value close to the lowest value that the fuel cell stack 1 can output.
That is, when the output voltage becomes the set voltage C, it means that the hydrogen gas concentration of the gas circulating in the circulation path has approached the minimum value of the hydrogen gas concentration necessary for power generation. Therefore, the circulation pump 164 is stopped to stop the hydrogen circulation, and the same hydrogen replacement purge process as that in step S103 is executed.
[0046]
These operations are repeated until the temperature of the fuel cell stack 1 exceeds the set temperature. In short, when the temperature of the fuel cell stack 1 is low, when the output voltage is larger than the set voltage B, hydrogen gas is retained in the fuel holding portion (the state where there is no gas flow), and from the set voltage C When the voltage is largely lower than the set voltage B, the hydrogen gas is circulated, and the gas once reacted is contacted with the fuel electrode repeatedly. When the voltage is lower than the set voltage C, new hydrogen gas is supplied.
[0047]
If the set temperature is the upper limit of the temperature range in which the generated water of the fuel cell freezes, the risk of freezing the generated water will be eliminated by reaching the set temperature. Hydrogen supply control is started.
Further, when the set temperature is the lower limit value of the temperature range in which power can be generated most efficiently, cooling is necessary to keep the temperature range thereafter, and thus control for warming up is unnecessary. . In this case, there is an advantage that the temperature of the fuel cell stack 1 can be reached in a short time to a region where power can be generated with high efficiency. Further, the same effect can be obtained when the set temperature is set to the lower limit value of the optimum temperature range necessary for obtaining the output for driving the load.
The above step S107 functions as a control means for maintaining the state in which the fuel gas is held in the fuel holding unit.
[0048]
In the configuration described above, the temperature sensor S11 of the fuel cell stack 1 may be configured to detect the temperature at or near the end of the fuel cell stack 1. Since this fuel cell system is configured to be warmed up by the reaction heat of each stacked fuel cell, the fuel cell located at the end includes current collectors 63a and 63b and insulating members 64a and 64b that do not generate heat. The end plates 65a, 65b, etc. are deprived of heat, and the temperature rise is slow compared to the central part. Therefore, if the temperature of this part is detected, it can be determined that the temperature of the other part is equal to or higher than the detected value, and the temperature of the entire fuel cell stack 1 is equal to or higher than the set temperature. Similarly, the output voltage of the fuel cell can be configured to detect the output voltage of one or two or more fuel cells connected in series located at or near the end of the fuel cell stack 1.
[0049]
Also in this case, since the temperature of the end portion of the fuel cell stack 1 is low as in the temperature sensor S11, the output voltage of the fuel cell in this portion is lower than in other portions. Therefore, if the voltage of this part is detected, the voltage of the other part is equal to or higher than the detected value, and it can be reliably determined that the voltage of the entire fuel cell stack 1 is equal to or higher than the set voltage.
[0050]
In addition, when the separator 3 is made of metal, the heat capacity of the fuel cell stack is reduced, and warming up of the fuel cell stack can be further promoted. In particular, since there is a limit in the amount of heat of reaction, it is particularly useful that the separator is made of a metal having a small heat capacity in the warm-up method using the reaction heat of each fuel cell.
[0051]
The fuel cell system 100 of the present invention as described above does not require an independent device for warm-up, for example, a vehicle or other movable body that has a small mounting space and cannot obtain another power source from outside the system. Especially useful as a power source for
The fuel cell system has been described on the assumption that the fuel cell is warmed up by the reaction heat of the fuel cell itself. However, for example, the fuel cell system may be used in a fuel cell in which warming heat generating means such as a heater is separately provided. In this case as well, by restricting the supply of hydrogen gas, heat discharge from the fuel cell can be suppressed and the warm-up time can be shortened.
[0052]
【The invention's effect】
According to the first aspect of the present invention, the state in which the hydrogen gas is held in the fuel holding unit is maintained, and the exhaust heat from the fuel cell stack due to the discharge of the hydrogen gas is suppressed, so the warm-up time is shortened. can do. In particular, when performing independent warm-up by reaction heat during power generation, inflow of new hydrogen gas that has not been warmed is eliminated, and the thermal efficiency for warm-up is improved, which is particularly useful.
In addition, when the temperature at the start of fuel supply is in a temperature range where freezing of the fuel cell generated water occurs, freezing can be suppressed by reducing exhaust heat from the fuel cell.
[0053]
According to the invention described in claim 2, the temperature of the end of the fuel cell stack 1 as a whole is equal to or higher than the detected temperature by detecting the temperature of the end portion where the temperature rise is slow compared to the central portion of the fuel cell stack. Can be determined reliably.
According to the invention described in claim 3, by configuring the separator with metal, the heat capacity can be reduced, and the warm-up time of the fuel cell can be further shortened.
[Brief description of the drawings]
FIG. 1 is an overall perspective view of a fuel cell stack.
FIG. 2 is a partial cross-sectional side view of the fuel cell stack of the present invention.
FIG. 3 is a plan sectional view of a fuel cell stack.
FIG. 4 is a schematic diagram showing a configuration of a fuel cell system.
FIG. 5 is a block diagram showing a control circuit that performs control at the start of power generation in the fuel cell system.
FIG. 6 is a flowchart.
FIG. 7 is a flowchart.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Fuel cell system 1 Fuel cell stack 164 Circulation pump 2 Unit cell 3 Separator 31 Current collection member 32 Current collection member 61 Power generation part 63 Current collector 64 Insulation member 65 End plate S8 Voltage sensor S11 Temperature sensor

Claims (3)

A fuel cell stack comprising a plurality of fuel cells in which a solid polymer electrolyte is sandwiched between an oxygen electrode and a fuel electrode, and a conductive separator interposed between adjacent fuel cells, and
A fuel holding unit for holding the fuel gas in a state where the fuel gas can come into contact with the fuel electrode;
Fuel introduction means for introducing fuel gas to the fuel holding portion;
Fuel deriving means for discharging fuel gas from the fuel holding portion;
An exhaust solenoid valve provided in the fuel deriving means;
Communicating means for communicating the fuel introducing means and the fuel deriving means;
A circulation pump that is provided in the communication means and discharges gas toward the fuel introduction means;
Fuel supply means for supplying fuel gas to the fuel holding portion via the fuel introduction means;
Temperature detecting means for detecting the temperature of the fuel cell;
When the detected value of the temperature detecting means is less than a predetermined temperature at the start of fuel supply, the circulation pump is stopped, the exhaust electromagnetic valve is closed, and the fuel holding portion is maintained in the fuel holding portion. And a control means for driving the circulation pump when the temperature becomes higher than the temperature. The fuel cell system according to claim 1, wherein the temperature detection unit detects a temperature of a fuel cell located at an end of the fuel cell stack. The fuel cell system according to claim 1, wherein the separator is made of metal.

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