JP2006164670A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system without fear of wasting cooling water, in preventing the cooling water from being frozen in a fuel cell stack. <P>SOLUTION: The fuel cell system 10 is provided with a fuel cell stack 20 cooled by cooling water, a water feeding and draining means 30 selectively executing drainage treatment collecting the cooling water from the fuel cell stack and a water feeding treatment returning the collected cooling water to the the fuel cell stack, and a controller 50 (a controlling means) for controlling execution of the drainage treatment or the water feeding treatment by the water feeding and draining means. The controller makes the water feeding and draining means perform drainage treatment at stoppage of a fuel cell, and perform the drainage treatment at start-up of the fuel cell. The fuel cell system is further provided with a flow channel drying means 40 for drying a flow channel where the cooling water in the fuel cell stack flows. The controller activates the flow channel drying means after having the water supply and drainage means perform the drainage treatment at stoppage of the fuel cell. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system having a fuel cell stack.

  The fuel cell stack is configured by fastening a stacked body in which a plurality of fuel cells are stacked. In the fuel cell, for example, a polymer electrolyte membrane is sandwiched between a pair of electrodes having a catalytic reaction layer, a conductive separator that supplies fuel gas is disposed on one electrode side, and an oxidation is disposed on the other electrode side. A conductive separator for supplying the agent gas is arranged. Since the fuel cell stack generates heat during power generation, cooling water is generally supplied to the fuel cell stack, and the fuel cell stack is cooled and maintained at an appropriate operating temperature.

  By the way, when the fuel cell is stopped, it is necessary to prevent freezing of the cooling water in the fuel cell stack and to prevent deterioration of the performance of the cell.

Patent Document 1 proposes a technique in which a flow path through which cooling water flows in a fuel cell stack is dried by reducing the pressure with a vacuum pump.
JP 2001-185179 A

  In the technique described in Patent Document 1, no consideration is given to the point of recovering the cooling water from the fuel cell stack, and there is a concern that, for example, pure water used for the cooling water is wasted.

  An object of the present invention is to provide a fuel cell system that does not waste the cooling water in preventing the cooling water from freezing in the fuel cell stack.

  The above object is achieved by the following means.

A fuel cell stack cooled by cooling water;
Water supply / drainage means for selectively performing drainage processing for recovering cooling water from the fuel cell stack, and water supply processing for returning the recovered cooling water to the fuel cell stack;
Control means for controlling execution of the wastewater treatment or the water supply treatment by the water supply / drainage means,
The control means is a fuel cell system in which the water supply / drainage means performs the wastewater treatment when the fuel cell is stopped, and the water supply / drainage means performs the water supply treatment when the fuel cell is started.

  According to the present invention, since the cooling water is collected from the fuel cell stack when the fuel cell is stopped, it is possible to prevent the cooling water from freezing in the fuel cell stack even when the outside air is at a low temperature. Furthermore, in order to prevent the cooling water from freezing in the fuel cell stack, the waste water treatment for collecting the cooling water from the fuel cell stack is performed, so that the cooling water is not wasted. In addition, when the fuel cell is started, a water supply process for returning the recovered cooling water to the fuel cell stack is performed, so that the cooling water can be quickly supplied to the necessary part and the start time of the fuel cell can be shortened.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing a fuel cell system 10 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a tank 31 shown in FIG.

  Referring to FIG. 1, a fuel cell system 10 generally includes a fuel cell stack 20 that is cooled by pure water as cooling water, a waste water treatment that recovers cooling water from the fuel cell stack 20, and recovered cooling water. A water supply / drainage means 30 for selectively performing a water supply process for returning the fuel cell stack 20 to the fuel cell stack 20, and a controller 50 (corresponding to a control means) for controlling the wastewater treatment or the water supply process performed by the water supply / drainage means 30. ing. The controller 50 causes the water supply / drainage means 30 to perform drainage processing when the fuel cell is stopped, and causes the water supply / drainage means 30 to perform water supply processing when the fuel cell is started. The fuel cell system 10 further includes flow path drying means 40 for drying the flow path through which the cooling water flows in the fuel cell stack 20, and the controller 50 causes the water supply / drainage means 30 to perform waste water treatment when the fuel cell is stopped. The channel drying means 40 is operated. The fuel cell system 10 of the present embodiment further includes a secondary battery 51 that is electrically connected to both the fuel cell stack 20 and the electric heater 42 provided in the flow path drying means 40. The charging / discharging of the secondary battery 51 is controlled. When the fuel cell is operating, the secondary battery 51 is charged with a part of the power generation amount, and when the electric heater 42 is operated, the secondary battery 51 is switched to the electric heater 42. It is discharging. Details will be described below.

  Referring to FIG. 1, a fuel cell system 10 includes, for example, a fuel cell stack 20 that serves as a power source for an electric vehicle, and a cooling water circulation system 11 that circulates cooling water through the fuel cell stack 20 and cools the fuel cell stack 20. And comprising. Although not shown, the fuel cell system 10 includes a fuel supply system for supplying hydrogen as fuel to the fuel cell stack 20, an air supply system for supplying air, and an electrolyte for the fuel cell stack 20. A known element such as a humidifying mechanism is provided.

  The fuel cell stack 20 is configured by fastening a stacked body in which a plurality of fuel cells are stacked. In the fuel cell, an electrolyte membrane is sandwiched between a pair of electrodes having a catalytic reaction layer, a conductive separator that supplies fuel gas (hydrogen) is disposed on one electrode side, and an oxidant is disposed on the other electrode side. A conductive separator for supplying gas (air) is arranged. At the fuel electrode, hydrogen dissociates into hydrogen ions and electrons. Hydrogen ions pass through the electrolyte, and electrons pass through an external circuit to generate power and move to the air electrode. At the air electrode, oxygen in the supplied air reacts with hydrogen ions and electrons to produce water, which is discharged to the outside. As the electrolyte of the fuel cell stack 20, for example, a solid polymer electrolyte is used in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  The cooling water circulation system 11 includes a pipe for circulating the cooling water through the fuel cell stack 20. A cooling water tank 12 for storing cooling water, a cooling water pump 13, and a heat exchanger are provided along the pipe. 14 is provided. By circulating the cooling water in the cooling water tank 12 by the cooling water pump 13 and supplying it to the fuel cell stack 20, the fuel cell stack 20 is cooled by the cooling water, and the fuel cell stack 20 is maintained at an optimum temperature. . The cooling water heated by cooling the fuel cell stack 20 is cooled by heat exchange with the outside air in the heat exchanger 14. Reference numerals 15 and 16 in the figure denote valves for partitioning the flow path through which the cooling water flows in the fuel cell stack 20.

  The water supply / drainage means 30 includes a tank 31 for storing cooling water and a liquid feeding means 32 for feeding cooling water. The liquid feeding means 32 is a forward direction from the fuel cell stack 20 toward the tank 31 (a direction indicated by a solid arrow in FIG. 1) and a reverse direction from the tank 31 toward the fuel cell stack 20 (a direction indicated by a dashed arrow in FIG. 1). ) In both directions. The controller 50 operates the liquid feeding means 32 so as to collect the cooling water from the fuel cell stack 20 to the tank 31 when the fuel cell is stopped, and returns the cooling water from the tank 31 to the fuel cell stack 20 when the fuel cell is started. The liquid feeding means 32 is operated.

  The tank 31 is formed in a vacuum double tank made of stainless steel, for example, and is insulated from the outside air (see FIG. 2). By insulating the tank 31 from the outside air, the temperature of the cooling water in the tank 31 can be kept almost constant regardless of the outside air temperature. The cooling water in the tank 31 does not freeze, and the water supply process for returning the recovered cooling water to the fuel cell stack 20 can be quickly performed when the fuel cell is restarted.

  Furthermore, the tank 31 includes an ion removal filter 33 (see FIG. 2). Various ions taken into the cooling water during operation can be removed at the time of water supply / drainage, and when the fuel cell is restarted, clean pure water can be returned to the fuel cell stack 20 as cooling water. Thereby, deterioration of a solid polymer electrolyte can be suppressed and the lifetime of the fuel cell stack 20 can be extended.

  The flow path drying means 40 includes an air supply means 41 for supplying air to the flow path of the fuel cell stack 20 and an electric heater 42 for heating the supplied air. The controller 50 operates the air supply means 41 and the electric heater 42 after causing the water supply / drainage means 30 to perform wastewater treatment when the fuel cell is stopped.

  In the illustrated embodiment, the liquid feeding means 32 is constituted by a pump 34 capable of sending liquid and gas, and the pump 34 is also used as the air supply means 41.

  The pump 34 that is rotationally driven in both forward and reverse directions by a motor is disposed in a pipe 60 that communicates with a flow path through which cooling water flows in the fuel cell stack 20. An electric heater 42 is disposed upstream of the pump 34 and a switching valve 61 is disposed downstream of the pump 34 with reference to the flow direction of the cooling water during wastewater treatment (indicated by a solid arrow in FIG. 1). Yes. The switching valve 61 includes a first position where the pipe 60 communicates with the tank 31 of the water supply / drainage means 30, a second position where the pipe 60 communicates with the air intake port 43, and the tank 31 and the air intake port 43. Both of these selectively operate to the third position (standby position) that does not communicate with the pipe 60. The operation of the switching valve 61 is also controlled by the controller 50. A filter 44 is attached to the air intake port 43 in order to prevent dust from entering the fuel cell stack 20.

  The type of the secondary battery 51 is not limited as long as it can be charged. For example, a lithium ion secondary battery used in an electric vehicle or the like can be used.

  The controller 50 is mainly composed of a CPU and a memory, and controls the operation of a charge / discharge circuit 52 connected to the secondary battery 51. When the fuel cell is operating, a part of the power generation amount is supplied to the secondary battery. Switch to the circuit to charge 51. On the other hand, when operating the electric heater 42, the controller 50 switches to a circuit for discharging the secondary battery 51 to the electric heater 42. The discharge from the secondary battery 51 to the electric heater 42 is performed for a preset time. Alternatively, a sensor for detecting the temperature of the fuel cell stack 20 and the supplied air may be provided, and the discharge to the electric heater 42 may be continued until the temperature rises to a set temperature.

  By providing the secondary battery 51 as described above, it is not necessary to supply power from a power source provided in a separate system from the fuel cell system 10, and the fuel cell system 10 itself can be easily controlled. There is an advantage that the battery stack 20 can be restarted quickly.

  Next, the operation of this embodiment will be described.

  When the fuel cell is operating, the controller 50 controls the operation of the charge / discharge circuit 52 and switches to a circuit that charges the secondary battery 51 with a part of the power generation amount. When charging of the secondary battery 51 is completed, the controller 50 stops charging the secondary battery 51. When the fuel cell is in operation, the switching valve 61 is operated to the third position, which is the standby position, and neither the tank 31 nor the air intake port 43 is in communication with the pipe 60.

  When the fuel cell is stopped, the controller 50 first stops the cooling water circulation by the cooling water circulation system 11, closes the valves 15 and 16, and partitions the flow path through which the cooling water flows in the fuel cell stack 20. The controller 50 controls the operation of the switching valve 61 and switches the switching valve 61 to the first position where the pipe 60 and the tank 31 of the water supply / drainage means 30 are communicated.

  Next, the controller 50 rotates the pump 34 in the forward direction to collect the cooling water from the drainage treatment, that is, the fuel cell stack 20 to the tank 31 (see the solid line arrow in FIG. 1). At this time, the recovered cooling water passes through the ion removal filter 33, so that various ions taken into the cooling water during operation are removed and stored in the tank 31 as clean pure water.

  When the drainage treatment is completed by operating the pump 34 for a predetermined time, the controller 50 temporarily stops the pump 34 and controls the operation of the switching valve 61, and connects the switching valve 61 to the pipe 60 and the air intake port 43. Switch to the second position. The controller 50 further controls the operation of the charging / discharging circuit 52 to switch to a circuit for discharging the secondary battery 51 to the electric heater 42. The electric heater 42 is energized to generate Joule heat. The controller 50 reversely rotates the pump 34 to supply air to the flow path of the fuel cell stack 20 while taking in air from the air intake port 43. At this time, the supplied air is heated by the Joule heat of the electric heater 42. By supplying heated air, moisture remaining in the flow path of the fuel cell stack 20 after the waste water treatment is evaporated, and the flow path is dried.

  The controller 50 operates the pump 34 for a predetermined time to switch the switching valve 61 to the third position when the drying of the flow path is completed.

  Thereafter, when restarting the fuel cell, the controller 50 first switches the switching valve 61 to the first position where the pipe 60 and the tank 31 of the water supply / drainage means 30 communicate with each other. Next, the controller 50 reversely rotates the pump 34 to return the water supply process, that is, the cooling water collected in the tank 31 to the fuel cell stack 20 (see the broken line arrows in FIG. 1). At this time, the returned cooling water passes through the ion removal filter 33, whereby clean pure water is returned to the fuel cell stack 20.

  When the water supply process is completed by operating the pump 34 for a predetermined time, the controller 50 stops the pump 34 and switches the switching valve 61 to the third position. Thereafter, the valves 15 and 16 are opened, the cooling water circulation by the cooling water circulation system 11 is resumed, and the normal operation is started.

  According to the fuel cell system 10 of the present embodiment, when the fuel cell is stopped, the cooling water is collected from the fuel cell stack 20 and the flow path of the fuel cell stack 20 is further dried, so the outside air becomes a low temperature. In addition, it is possible to reliably prevent the cooling water from freezing in the fuel cell stack 20. Furthermore, in order to prevent the cooling water from freezing in the fuel cell stack 20, the waste water treatment for collecting the cooling water from the fuel cell stack 20 to the tank 31 is performed, so that the cooling water is not wasted. At the time of starting the fuel cell, a water supply process for returning the recovered cooling water to the fuel cell stack 20 is performed, so that the cooling water can be quickly supplied to the necessary part, and the starting time of the fuel cell can be shortened.

(Modification)
Although the pump 34 has shown the form which uses both the liquid feeding means 32 and the air supply means 41, the liquid feeding means 32 which consists of liquid pumps, etc., and the air supply means 41 which consists of gas pumps, a blower, etc. separately. Needless to say, it may be provided.

  Although the embodiment in which the water supply / drainage means 30 is provided separately from the cooling water circulation system 11 is shown, the water supply / drainage means 30 in the present invention may be incorporated in the cooling water circulation system 11. In this case, the cooling water tank 12 in the cooling water circulation system 11 can function as the tank 31 in the water supply / drainage means 30.

  Although the form which heat-insulates with respect to external air by forming the tank 31 in a vacuum double tank was shown, the form which surrounds a tank with a heat insulating material may be sufficient.

1 is a configuration diagram showing a fuel cell system according to an embodiment of the present invention. It is sectional drawing which shows the tank shown by FIG.

Explanation of symbols

10 Fuel cell system,
11 Cooling water circulation system,
20 Fuel cell stack,
30 Water supply / drainage means,
31 tanks,
32 liquid feeding means,
33 ion removal filter,
34 Pump (liquid feeding means, air supply means),
40 Channel drying means,
41 air supply means,
42 electric heaters,
43 Air intake port,
50 controller (control means),
51 secondary battery,
60 piping,
61 Switching valve.

Claims (8)

A fuel cell stack cooled by cooling water;
Water supply / drainage means for selectively performing drainage processing for recovering cooling water from the fuel cell stack, and water supply processing for returning the recovered cooling water to the fuel cell stack;
Control means for controlling execution of the wastewater treatment or the water supply treatment by the water supply / drainage means,
The control means causes the water supply / drainage means to perform the wastewater treatment when the fuel cell is stopped, and causes the water supply / drainage means to perform the water supply treatment when the fuel cell is started. A flow path drying means for drying the flow path through which the cooling water flows in the fuel cell stack;
2. The fuel cell system according to claim 1, wherein the control unit operates the flow path drying unit after causing the water supply / drainage unit to perform the wastewater treatment when the fuel cell is stopped.
The water supply / drainage means includes a tank for storing cooling water, and a liquid feeding means for feeding cooling water,
The control means operates the liquid feeding means so as to collect cooling water from the fuel cell stack to the tank when the fuel cell is stopped, and returns cooling water from the tank to the fuel cell stack when the fuel cell is started. The fuel cell system according to claim 1 or 2, wherein the liquid feeding means is operated as described above.   The fuel cell system according to claim 3, wherein the tank is insulated from outside air.   The fuel cell system according to claim 3 or 4, wherein the tank includes an ion removal filter. The flow path drying means includes an air supply means for supplying air to the flow path of the fuel cell stack, and an electric heater for heating the supplied air.
3. The fuel cell system according to claim 2, wherein the control unit operates the air supply unit and the electric heater after causing the water supply / drainage unit to perform the wastewater treatment when the fuel cell is stopped. The water supply / drainage means includes liquid supply means for supplying cooling water,
7. The fuel cell system according to claim 6, wherein the liquid feeding means is constituted by a pump capable of sending liquid and gas, and the pump is also used as the air supply means. A secondary battery electrically connected to both the fuel cell stack and the electric heater;
The control means controls charging / discharging of the secondary battery, charges the secondary battery with a part of the power generation amount when the fuel cell is operating, and operates the electric heater when the electric heater is operated. The fuel cell system according to claim 6, wherein the electric heater is discharged from a battery.

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