JP2009224179A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve reduction of a thawing time of water in a water tank, and saving of thawing energy by controlling so that a water amount in the water tank becomes less. <P>SOLUTION: In the case the outside temperature is low, water recovery capacity by a condenser 51 becomes higher. In this case, since water is optionally replenishable, the water amount in the water tank 53 can be set low. In order to adjust the water amount of this water tank 53, the number of rotation of an air cooling fan 511 is controlled, and the water recovery capacity of the condenser 51 is adjusted. Like this, by reducing the water amount in the water tank 53, energy and time consumed for thawing at the time of freezing can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system capable of adjusting the amount of water stored in the fuel cell system.

Some fuel cell systems supply water to the oxygen electrode in order to discharge reaction heat generated during power generation and to wet the ion exchange membrane. In such a system, water is stored in a tank, the water in the tank is sprayed into the fuel cell stack in a mist, and the sprayed water is collected and circulated in the tank to cool the fuel cell stack. The structure to do is taken.
The water used in the above configuration may freeze in cold regions. The following patents are used to prevent damage to the fuel cell device due to water freezing and to save energy for thawing the frozen water at start-up. As shown in Document 1, a fuel cell device has been proposed in which all water in a tank or piping is discharged at the end of power generation operation.
JP-A-11-273704

However, in the conventional fuel cell device, a large amount of water is discharged to the outside, and thus the discharged water may be frozen. Moreover, since the conventional fuel cell apparatus is installed and used in a fixed position, it is possible to prepare facilities for treating wastewater in advance. However, in a fuel cell device mounted on a moving body such as a vehicle, the place where the vehicle is parked is not limited to a specific place, and there are many places where drainage facilities are not provided. In such a place, the vehicle is parked. The problem is that the place where the water is discharged is polluted by drainage.
Further, when water is not discharged at the end of power generation, energy is required to thaw frozen water at the time of starting, and the energy efficiency of the entire system is deteriorated. In addition, during the thawing time, water cannot be circulated, and the preparation time until the fuel cell is driven to generate electricity becomes longer, resulting in a lack of convenience.

  An object of the present invention is to provide a fuel cell system capable of shortening the thawing time of water in the water tank and saving thawing energy by controlling the amount of water in the water tank to be small. .

The present invention for solving the above problems has the following configuration.
(1) A fuel cell stack in which a plurality of fuel cells are stacked via a conductive separator, an air flow passage through which air flows in contact with the oxygen electrode of the fuel cell, and supply to the fuel cell stack A storage means for storing the cooling water to be cooled, an outside air temperature detection means for detecting an outside air temperature, a water amount detection means for detecting the amount of water in the water storage means, and provided on the downstream side of the fuel cell in the air flow passage, Water recovery means for recovering water from the air discharged from the battery and supplying the recovered water to the water storage means; recovered water amount adjusting means for adjusting the amount of recovered water by the water recovery means; and detected by the outside air temperature detection means And a water storage amount adjusting means for adjusting the water amount of the water storage means by adjusting the recovered water amount of the recovered water amount adjusting means based on the outside air temperature and the water amount detected by the water amount detecting means. A fuel cell system.

  (2) The fuel cell system according to (1), wherein the water storage amount adjustment unit sets the water amount of the water storage unit to be larger as the outside air temperature is higher, and the water amount of the water storage unit to be smaller as the outside air temperature is lower.

According to the first aspect of the present invention, the water recovered by the water recovery means from the air flow passage is supplied to the water storage means and supplied again to the fuel cell stack as cooling water. Since the water recovery capability of the water recovery means increases as the outside air temperature decreases, the amount of water that can be supplied to the water storage means changes according to the outside air temperature. By adjusting the amount of water in the water storage means to an appropriate amount according to the change in the water supply capacity of the water recovery means, it is possible to suppress the accumulation of excess water in the water storage means, and to store the minimum amount of water. It can be left in the means. In this way, since the amount of water remaining in the water storage means is reduced, it is possible to save thawing energy when frozen and to shorten the time until thawing.
According to the second aspect of the invention, the lower the outside air temperature, the higher the water recovery efficiency. Therefore, only a small amount of water needs to be stored in the water storage means, and when thawing frozen water. Energy can be saved.

  Next, a preferred embodiment of the present invention will be described. This embodiment is a fuel cell system mounted on an electric vehicle. FIG. 1 is a block diagram showing a configuration example of a fuel cell system 1 of the present invention. As shown in FIG. 1, the fuel cell system 1 is roughly configured by a fuel cell stack 100, a fuel supply system 10 including a hydrogen storage tank 11, an air supply system 12, a water supply system 50, and a load system 7. The

  The fuel cell stack 100 is configured by laminating a membrane-electrode assembly (unit cell) and a separator (current collector) constituting a fuel cell, and hydrogen as a fuel gas is applied to the fuel electrode of the laminated fuel cell. Then, air as an oxidizing gas is supplied to the oxidation electrode to generate a power generation reaction through the solid polymer electrolyte layer to generate power. Hereinafter, the configuration of the fuel cell stack 100 will be described. FIG. 2 shows a laminated structure of the separator and membrane-electrode assembly constituting the fuel cell stack 100. FIG. 3 is a top view of the stacked configuration shown in FIG. The solid polymer electrolyte layer 15a is sandwiched between the oxygen electrode 15b and the fuel electrode 15c, and the membrane-electrode assembly 15 is formed. The ribs 32 and 42 of the carbon bipolar plate 3a having the ribs 32 and 42 on the front and back surfaces are thermocompression bonded to the metal porous bodies 3b and 3c, and the carbon bipolar plate 3a and the metal porous bodies 3b and 3c are integrated to form a separator. A current collector 13 is formed. The metal porous body side of the current collector 13 is in contact with the oxygen electrode side and the fuel electrode side of the membrane-electrode assembly 15. Further, the hydrogen flow path 302 is formed by the space between the ribs 32 and 32, and the air flow path 40 is formed by the space between the ribs 42 and 42. In FIG. 2, the air in the air channel 40 flows in the vertical direction, and the hydrogen in the hydrogen channel 302 flows in the direction perpendicular to the drawing. In FIG. 3, the air in the air flow path 40 partitioned by the ribs flows in the direction perpendicular to the figure, and the hydrogen in the hydrogen flow path 302 flows in the left-right direction in the figure. The air in the air channel 40 and the hydrogen in the hydrogen channel 302 pass through the metal porous bodies 3b and 3c and reach the oxygen electrode 15b and the fuel electrode 15c. The oxygen supplied to the oxygen electrode 15 b is oxygen contained in the air passing through the air flow path 40.

  Along with air, mist-like water ejected from a later-described ejection nozzle 55 flows into the air flow path 40 to maintain the oxygen electrode 15b in a wet state and suppress the temperature rise of the fuel cell stack 100 by latent heat cooling. Is done. Hydrogen as fuel gas supplied from the gas inlet 201BIN flows through the hydrogen flow path 302, and the hydrogen that has passed through the hydrogen flow path 302 is discharged from the gas discharge port 202OUT.

  The configuration of the fuel supply system 10 will be described. A hydrogen storage tank 11 that is a fuel gas cylinder is connected to a gas inlet 201BIN of the fuel cell stack 100 via fuel gas supply channels 201A and 201B. The fuel gas supply channel 201A is provided with a hydrogen filling on-off valve 18, a primary sensor S0, a regulator 21, a hydrogen supply electromagnetic valve 22, and a secondary pressure sensor S2 in this order. It is connected to the supply flow path 201B. The fuel gas supply channel 201B is connected to the gas inlet 201BIN of the fuel cell stack 100. One end of the gas discharge channel 202 is connected to the gas discharge port 202 OUT of the fuel cell stack 100, and the other end is connected to the trap 24. One end of the circulation flow path 204 and one end of the gas outlet path 203 are connected to the trap 24. The other end of the gas outlet path 203 is connected to an air discharge path 124 described later. An exhaust solenoid valve 27 is provided in the gas outlet passage 203.

  The other end of the circulation channel 204 is connected to the outside air inflow channel 206. The circulation flow path 204 is provided with a circulation pump 25 and a circulation electromagnetic valve 26, and one end of a decompression discharge path 205 is connected between the circulation pump 25 and the circulation electromagnetic valve 26. The other end of the reduced pressure discharge path 205 is a reduced pressure discharge port 205OUT opened in the air discharge path 124, and the reduced pressure discharge path 205 is provided with a reduced pressure electromagnetic valve 23. The other end of the outside air inflow path 206 opens to the outside, and the filter 29 and the outside air introduction electromagnetic valve 28 are provided in this order from the opening side. The fuel gas supply channel 201B, the gas discharge channel 202, the circulation channel 204, and the outside air inflow channel 206 form a gas circulation channel.

  When driving of the fuel cell system 1 is stopped, the hydrogen supply solenoid valve 22, the circulation solenoid valve 26, the exhaust solenoid valve 27, and the outside air introduction solenoid valve 28 are closed, and the pressure reducing solenoid valve 23 is opened. Then, by driving the circulation pump 25, the gas in the hydrogen flow path 302 (fuel chamber) in the fuel cell stack 100 is sucked and discharged from the reduced pressure discharge port 205OUT. When the internal air pressure is detected by the sensor S2 and becomes equal to or lower than a predetermined value (negative pressure), the pressure reducing solenoid valve 23 is closed and the outside air introduction solenoid valve 28 is opened, so that the outside air flows into the hydrogen flow path 302. Replace hydrogen with air.

  Next, the air supply system 12 will be described. The air supply system 12 includes an air introduction path 123, an air manifold 54, and an air discharge path 124. In the air introduction path 123, a filter 121, an outside air humidity sensor S10 as outside air humidity detecting means, an outside air temperature sensor S6 as outside air temperature detecting means, an air fan 122, a heater H, an air inlet temperature sensor S5, and an air manifold 54 are arranged in this order. It is provided along the inflow direction. The air manifold 54 is provided vertically above the fuel cell stack 100, and a nozzle 55 for injecting cooling water is provided therein. The air manifold 54 divides and flows air into each air flow path 40 of the fuel cell stack 100.

  The air discharge path 124 is connected to the discharge side (lower side) of the air flow path 40 of the fuel cell stack 100, joins the air that has flowed out of the air flow path 40, and guides it to the outside. The air discharge path 124 is provided with a condenser 51 to which an air cooling fan 511 that promotes heat exchange is attached, and then a filter 125 is connected. The condenser 51, which is a water recovery means, separates air and moisture. The water supplied from the nozzle 55 is also collected here. An exhaust temperature sensor S9 is provided in the air discharge path 124, and the temperature of the fuel cell stack 100 is indirectly detected. The condenser 51 is provided with an air-cooling fan 511 as a recovery water amount adjusting means, and the outside air is taken into the condenser 51 to exchange heat between the air discharged from the fuel cell stack 100 and the outside air. It has become. The outside air taken in by the air cooling fan 511 is further discharged to the outside of the condenser 51. By adjusting the rotational speed of the air cooling fan 511, the water recovery capability of the condenser 51 is adjusted. That is, increasing the number of rotations of the air cooling fan 511 increases the water recovery capability, and decreasing the number of rotations decreases the water recovery capability. The air introduction passage 123, the air passage 40, and the air discharge passage 124 constitute an air flow passage.

  Next, the water supply system will be described. The water supply system 50 includes a water tank 53 that is a water storage means, a water conduit 52 that guides the water collected by the condenser 51 to the water tank 53, and a water supply passage that guides the water in the water tank 53 to the suction port of the water supply pump 61. 56 and a discharge path 561 that connects the discharge port of the water supply pump 61 and the spray nozzle 55. A collection pump 62 is provided in the water conduit 52. The water supply passage 56 is provided with a filter 64 and a water supply pump 61 as water supply means in this order, and the discharge passage 561 is provided with a water supply electromagnetic valve 631 and an injection nozzle 55 in order.

  An outside air intake passage 54 is connected to the water supply passage 56, and an outside air intake electromagnetic valve 65 is provided in the introduction passage 54. The water tank 53 is provided with a water temperature sensor S7 and a tank water amount sensor S8 which is a water amount detecting means. The water tank 53 is provided with a water tank heater 53H, and when the water in the water tank 53 is frozen, the water tank heater 53H is used for thawing. The condenser 51, the water conduit 52, and the recovery pump 62 constitute water recovery means. The condenser 51 is provided with a cooling air temperature sensor S11 that detects the temperature of outside air as cooling air and a cooling air humidity sensor S12 that detects the humidity of outside air as cooling air.

  A load system 7 is connected to the fuel cell stack 100, and electric power output from the fuel cell stack 100 is supplied to the load system 7. The electrodes of the fuel cell stack 100 are connected to relays 72 and 72 via a wiring 71, and the relays 72 and 72 are further connected to a motor 74 via an inverter 73. In addition, an auxiliary power source 76 is connected to the inverter 73 via an output control device 75.

  The load system 7 is provided with a voltage sensor S4 for detecting the output voltage of the fuel cell stack 100 and a current sensor S3 for detecting the output current. As shown in FIG. 1, the control system of the fuel cell system 1 receives the detection values of the sensors S0, S2 to S12, the regulator 21, the solenoid valves 22, 23, 26 to 28, 631, 632, 65. , Each pump 25, 62, 61, fan 122, rotation number of fan 511, heater H, water tank heater 53 H, inverter 73, and control device (FC ECU) 200 for controlling output control device 75 are provided. An ignition switch (not shown) is connected to the control device 200, and an instruction signal for driving or stopping the motor 74 is input.

Hereinafter, the operation of the fuel cell system 1 of the present invention will be described. FIG. 4 is a flowchart showing the operation at the end of driving of the fuel cell system 1. When the ignition switch ON operation of the vehicle, which means power generation start (drive start) of the fuel cell system 1, is detected (step S101), start processing (step S103) of the fuel cell system 1 is started.
In this activation process, for example, as described above, a replacement gas (air) is discharged from the hydrogen flow path 302 of the fuel cell stack 100 and replaced with hydrogen.

In parallel with the start-up process (step S103) and during normal power generation driving, the water amount control process shown in steps S105 to S119 below is executed.
A water temperature T3 in the water tank 53 is detected by the water temperature sensor S7, and it is determined whether or not the water temperature is higher than a set temperature (step S105). This step determines whether or not the water is frozen. Therefore, when it is lower than the set temperature, it is necessary to defrost, so the heater 53H is turned on and the water is warmed until it becomes higher than the set temperature.
When the water temperature T3 is equal to or higher than the set temperature, the outside air temperature sensor S6 or S11 detects the outside air temperature T1, the outside air humidity sensor S10 or S12 detects the outside air humidity H1, and the water amount sensor S8 detects the amount of water in the water tank 53. (Step S109).

  Next, the amount of water stored in the water tank 53 is determined based on the map shown in FIG. 5 (step S111). FIG. 5 is a map for determining the amount of water from the detected outside air temperature T1. When the outside air temperature is not more than A degrees Celsius, the amount of water is maintained at L0. This is an amount that does not run out of water in the water tank 53 with respect to a time delay from when the water is injected from the injection nozzle 55 to when the water is collected in the water tank 53. The maximum value L1 is an amount set when the amount of water collected by the condenser 51 is the lowest.

  Furthermore, the graph line N0 in the map of FIG. 5 shows the relationship between the outside air temperature and the amount of water in the case of the annual average value of the outside air humidity. As the outside air temperature decreases, the amount of water collected by the condenser 51 increases, so that the amount of water in the water tank 53 can be set small. This is because the water tank 53 can be replenished with water as necessary. For this reason, the graph line N0 in the map of FIG. 5 is set so that the amount of water decreases as the outside air temperature decreases.

  When the outside air humidity is higher than the average value, the recovered amount is expected to be higher than the average humidity, so the lower graph line N2 is adopted so that the amount of water in the water tank 53 is set to be small. Is done. Similarly, when the outside air humidity is lower than the average value, the recovered amount is expected to be smaller than the average humidity, so the upper graph line N1 is adopted so that the amount of water in the water tank 53 is set to a large number. Is done. A plurality of graph lines corresponding to the humidity may be set according to the detected humidity value. The graph line N0 is not necessarily a straight line, and may be a curve or a configuration in which the amount of water is changed stepwise. In this way, the higher the outside air humidity, the higher the water recovery efficiency, so that a smaller amount of water needs to be stored in the water storage means, which saves energy when thawing frozen water. It becomes possible to do.

  It is determined whether or not the amount of water detected in step S109 is less than the set amount of water determined in step S111 (step S113). When the amount is small, it is necessary to increase the amount of water in the water tank 53, so that the water recovery capability is increased in order to increase the amount of water recovery (step S115). Specifically, the air cooling fan 511 of the condenser 51 is turned on. If it is already on, increase the number of revolutions and increase the cooling capacity by increasing the cooling air volume. As a result, the amount of water collected by the condenser 55 increases, and the amount of water in the water tank 53 increases.

  When the amount of water in the water tank 53 is larger than the set amount of water, the amount of water in the water tank 53 can be reduced, so that the water collection capacity is lowered in order to reduce the amount of collected water (step S117). Specifically, the air cooling fan 511 of the condenser 51 is turned off. Alternatively, the cooling capacity is lowered by lowering the number of revolutions and lowering the amount of cooling air. As a result, the amount of water collected by the condenser 55 is reduced, and a part of the water discharged from the injection nozzle 55 is discharged together with the outside air to reduce the amount of water in the water tank 53. Note that the rotation speed control of the air cooling fan 511 in steps S115 and S117 may be changed according to the magnitude of the difference between the detected water amount and the set value. Thus, since the water recovery means is an air-cooled condenser, the amount of water recovered can be easily controlled by controlling the rotational speed of the air-cooling fan.

Next, it is determined whether or not an ignition switch OFF operation as a power generation stop operation has been performed (step S119). When the power generation stop operation is not performed, the operations in steps S109 to S117 are repeated, and the amount of water in the water tank 53 is adjusted according to the outside air temperature and the outside air humidity. A stored water amount adjusting means is configured by steps S109 to S117.
When the power generation stop operation is performed, the water amount adjustment control in the water tank 53 is finished, and the process of stopping the fuel cell is started (step S121). At this time, the amount of water corresponding to the outside air temperature at the time of the stop operation is stored in the water tank 53, and a smaller amount of water than the conventional water amount L1 is stored in the water tank 53. When frozen, it can be thawed with less energy.

It is a block diagram which shows the structure of the fuel cell system of this invention. It is an internal perspective view which shows the laminated structure of the separator and membrane-electrode assembly which comprise a fuel cell stack. FIG. 3 is a top view of the stacked configuration shown in FIG. 2. It is a flowchart which shows the operation | movement at the time of completion | finish of a drive of a fuel cell system. It is a map which shows the relationship between external temperature and the setting value of the amount of water of a water tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 100 Fuel cell stack 12 Air supply system 122 Air fan 123 Air introduction path 124 Air discharge path 53 Water tank 55 Injection nozzle 552 Second discharge port 51 Condenser 511 Air cooling fan 61 Water supply pump S6 Outside air temperature sensor S8 Water quantity Sensor S10 Outside air humidity sensor

Claims (2)

A fuel cell stack in which a plurality of fuel cells are stacked via a conductive separator;
An air flow passage through which air flows in contact with the oxygen electrode of the fuel cell;
Water storage means for storing cooling water supplied to the fuel cell stack;
An outside air temperature detecting means for detecting the outside air temperature;
Water amount detection means for detecting the amount of water in the water storage means;
Water recovery means provided on the downstream side of the fuel cell in the air flow passage, for recovering water from the air discharged from the fuel cell and supplying the recovered water to the water storage means;
Recovered water amount adjusting means for adjusting the amount of recovered water by the water recovery means;
Reservoir amount adjustment for adjusting the water amount of the water storage means by adjusting the recovered water amount of the recovered water amount adjusting means based on the outside air temperature detected by the outside air temperature detecting means and the water amount detected by the water amount detecting means. And a fuel cell system.   2. The fuel cell system according to claim 1, wherein the water storage amount adjusting unit sets a larger amount of water in the water storage unit as the outside air temperature is higher, and sets a smaller amount of water in the water storage unit as the outside air temperature is lower.

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