JP2004234965A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a start-up time of a fuel cell system by speeding up supply of pure water when the pure water to be used for the system is frozen. <P>SOLUTION: A pure water pump 4 taking out the pure water from a pure water tank 3 and circulating it in the fuel cell system is installed at a lower part of the pure water tank 3 storing the pure water necessary for operation of the fuel cell system, and the pure water tank 3 is constructed so that the pure water stored therein is taken out from the bottom part of the pure water tank. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system that activates the system after defrosting frozen water when pure water used in the fuel cell system is frozen.
[0002]
[Prior art]
Conventionally, as this kind of technology, for example, a technology described in the following document is known (see Patent Document 1). According to the technique described in this document, when water used in a fuel cell system is frozen, a process of heating a water tank with an electric heater to defrost frozen water is performed. In the decompression process, first, the available power that can be used for the decompression process and the decompression required power are calculated, and if available power> decompression required power, the decompression mode is activated. In the thawing mode, the electric power supplied to the electric heater is calculated, and the thawing time is calculated based on the required electric power for thawing and the unit electric power supplied to the electric heater. Thereafter, the defrost timer is started, and when the defrost timer reaches the defrost time, the defrost mode is ended. When the thawing mode ends and the frozen water is thawed, the system is activated.
[0003]
[Patent Document 1]
JP-A-2002-110187
[Problems to be solved by the invention]
As described above, in the conventional fuel cell system, when the water used in the system freezes, the system cannot be started until all the frozen water has been thawed. For this reason, after starting the thawing process of the frozen water, it takes a lot of time until the system is started, which causes a problem that the start-up time becomes long.
[0005]
In view of the above, the present invention has been made in view of the above, and an object of the present invention is to provide a fuel in which, when freezing pure water used in a system, the supply of pure water is speeded up and the system startup time is reduced. It is to provide a battery system.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, means for solving the problems of the present invention include a fuel cell stack that generates power by supplying hydrogen and air, a pure water tank that stores pure water required for operation of the fuel cell system, A humidifier that humidifies the hydrogen and air supplied to the fuel cell stack, and a pure water pump that removes pure water stored in the pure water tank from the pure water tank and circulates through the fuel cell system; When the pure water stored in the pure water tank is frozen, the pure water pump is heated, and an electric heater for thawing the frozen water in the pure water tank is provided. It is installed at the lower part of the pure water tank, and the pure water stored in the pure water tank is taken out from the bottom of the pure water tank.
[0007]
【The invention's effect】
According to the present invention, the pure water pump is installed at the lower part of the pure water tank, and the pure water stored in the pure water tank is taken out from the bottom of the pure water tank. The priming required in such a case becomes unnecessary, and it becomes possible to supply the obtained pure water sequentially from the time when the thawing of the frozen water is started and a small amount of pure water is obtained. As a result, the system can be started without waiting for all the frozen water to be thawed, and the start-up time of the system can be reduced.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
FIG. 1 is a diagram showing a configuration of a fuel cell system according to one embodiment of the present invention. The fuel cell system according to the embodiment shown in FIG. 1 includes a fuel cell stack 1, a humidifier 2, a pure water tank 3, a pure water pump 4, a hydrogen circulation pump 5, a cooling water pump 6, an air compressor 7, an electric heater 8, a converter 9, a secondary battery 10, a hydrogen supply device 16, a pure water pump suction pipe shut-off valve 19, and a controller (not shown) configured by a microcomputer and the like to control operation processing of the fuel cell system based on a program. It is configured.
[0010]
The fuel cell stack 1 generates power using hydrogen supplied to the fuel electrode and oxygen in the air supplied to the air electrode. The generated power is supplied to and stored in the secondary battery 10 via the converter 9 that performs power generation control and power conversion.
[0011]
The humidifier 2 humidifies air supplied to the fuel cell stack 1 and hydrogen serving as fuel with pure water stored and supplied in a pure water tank 3. Air is supplied to the humidifier 2 via the air compressor 7, and hydrogen is supplied from the hydrogen supply device 16 via the hydrogen pressure regulating valve 11.
[0012]
The pure water tank 3 stores pure water supplied to the humidifier 2. A pure water pump 4 is provided below the pure water tank 3 via a pure water pump suction pipe shut valve 19. The pure water stored in the pure water tank 3 is supplied from the bottom of the pure water tank 3 to the humidifier 2 via the pure water pump suction pipe shut valve 19 and the pure water pump 4, and from the humidifier 2 via the valve 14. And return to the pure water tank 3. With such a configuration, after the pure water stored in the pure water tank 3 is frozen and the thawing process of the frozen water is started, when a small amount of pure water is obtained, the pure water obtained is replaced with the pure water tank. 3 is supplied to the humidifier 2 via a pure water pump 4.
[0013]
The hydrogen circulation pump 5 circulates hydrogen supplied from the hydrogen supply device 16 to the fuel cell stack 1 via the humidifier 2 between the fuel cell stack 1 and the humidifier 2. The cooling water pump 6 circulates cooling water for cooling the fuel cell stack 1 between the fuel cell stack 1, the pure water tank 3, and the radiator 24. The cooling water that cools the fuel cell stack 1 generates heat by passing through the fuel cell stack 1, and the generated cooling water passes through the pure water tank 3, thereby facilitating the thawing of the frozen water.
[0014]
The electric heater 8 is provided to heat the pure water tank 3 and a pure water pump suction pipe from the pure water tank 3 to the pure water pump 4. In the thawing process for thawing the frozen water in the pure water tank 3, the electric heater 8 controls the pure water tank 3 and the pure water pump suction pipe shut valve 19 based on the electric power supplied from the secondary battery 10 via the converter 9. Heat the pump suction piping including.
[0015]
Next, a stop sequence of the system configured as described above will be described with reference to a flowchart of FIG.
[0016]
First, the pure water pump suction pipe shut valve 19 is closed (step S30), the shut valve 13 is closed, the shut valve 12 is opened, and the purge valve 17 is opened (step S31). In such a state, dry air is supplied to the fuel cell stack 1 to purge condensed water in the fuel cell stack 1 (step S32).
[0017]
When the purging is completed, the shut valve 12 is closed and the shut valve 13 is opened (step S33), and the pure water of the pure water system is collected into the pure water tank 3 or discharged to the outside. At this time, the valves 14 and 20 are alternately opened and closed to purge the pure water uniformly (step S34).
[0018]
After the purge is completed, the remaining amount of the secondary battery 10 is checked (step S35), and the remaining amount of the secondary battery 10 is sufficient to defrost the frozen water in the pure water tank 3 when the system is started. In this case (step S36), the system is stopped (step S37). On the other hand, when the remaining amount of the secondary battery 10 is not enough to perform the thawing at the time of starting the system (step S38), the power generation of the fuel cell stack 1 is continued for a while. After charging the secondary battery 10 with the generated power (step S39), the system is stopped (step S37).
[0019]
Next, a system startup sequence will be described with reference to the flowchart of FIG. 3 and FIG. 4 showing the relationship between the amount of water in the pure water tank 3 and the load of a motor driving the pure water pump 4.
[0020]
First, the pure water pump suction pipe shut valve 19 is opened (step S40). At this time, the pure water level is confirmed by the pure water pump outlet pipe level sensor 23 (step S41), and it is determined whether the pure water level is equal to or more than a predetermined value (step S42). As a result of the determination, if the pure water level is equal to or more than the predetermined value, the pure water pump 4 is started (step S44). At this time, the load of the motor of the pure water pump is detected, and if the load of the motor does not decrease, the pure water pump 4 is continuously operated. On the other hand, if the load on the motor immediately decreases, the pure water pump 4 is stopped and the electric heater 8 is energized. As a result, the pure water tank 3 and the pure water pump suction pipe are heated, and a thawing process for thawing the frozen water in the pure water tank 3 is performed.
[0021]
After a certain period of time (set by the atmospheric temperature measured by the atmospheric thermometer 22) after energization, the pure water pump 4 is started, and it is determined whether or not the load on the motor of the pure water pump 4 has decreased. (Step S45). If the result of the determination indicates that the load on the motor has decreased, it is determined that the pure water stored in the pure water tank 3 has run out, and the pure water pump 4 is stopped (step S46).
[0022]
On the other hand, if the result of the determination in step S42 indicates that the pure water level is not equal to or higher than the predetermined value, the electric heater 8 is immediately energized (step S43). As a result, the pure water tank 3 and the pure water pump suction pipe are heated, and a thawing process for thawing the frozen water in the pure water tank 3 is performed. After a certain period of time (set by the atmospheric temperature measured by the atmospheric thermometer 22) after the power is supplied, the pure water pump 4 is started (step S44), and the load of the motor of the pure water pump 4 is reduced. Is determined (step S45). If the result of the determination indicates that the load on the motor has decreased, it is determined that the pure water stored in the pure water tank 3 has run out, and the pure water pump 4 is stopped (step S46).
[0023]
Such processing is repeated several times. As shown in FIG. 4, when the total time during which the motor load of the pure water pump 4 is constant exceeds a predetermined value (step S47), the fuel The normal operation of the battery stack 1 is started (Step S48). However, the power generation amount of the fuel cell stack 1 is limited until it is determined that all the frozen water in the pure water tank 3 has been thawed.
[0024]
After the power generation is started in a state where the power generation amount is limited, as shown in FIG. 4, the frozen water in the pure water tank 3 is discharged based on the total time during which the motor load of the pure water pump 4 is constant. Estimate that everything has been thawed. As a result of the estimation, when all the frozen water in the pure water tank 3 is thawed and the thawing process is completed, the restriction on the power generation amount is released, and the power generation is continuously performed.
[0025]
The freezing of the pure water stored in the pure water tank 3 is determined based on the temperature of the atmosphere measured by the atmospheric thermometer 22 and the load of the motor driving the pure water pump 4.
[0026]
As described above, in the above embodiment, the pure water pump 4 is installed at the lower part of the pure water tank 3, and the pure water stored in the pure water tank 3 is taken out from the bottom of the pure water tank 3. In addition, priming, which is required in the case of a system in which pure water is drawn from a tank, is not required. In addition, pure water obtained by thawing in the pure water tank 3 can be sequentially supplied to the humidifier 2. Thereby, if the supply amount of the pure water supplied to the humidifier 2 reaches a certain amount, that is, if there is a certain amount of pure water in the humidifier 2, the system can be operated under a low load. As a result, the system can be activated, and the activation time can be reduced.
[0027]
Further, when the system is activated and the fuel cell stack 1 generates power, the cooling water is heated by the heat generated by the fuel cell stack 1, and the heated cooling water passes through the pure water tank 3 to promote thawing. be able to.
[0028]
Further, by installing the electric heater 8 also in the pure water pump suction pipe, the pure water pump suction pipe can be heated mainly, and the supply of the pure water to the humidifier 2 can be performed quickly. .
[0029]
If the pump is provided at the top of the tank and the pure water stored in the tank is sucked up from the tank by the pump, the suction pipe for sucking the pure water will sink below the liquid level in the tank. The piping will also freeze with the pure water inside the tank. For this reason, thawing becomes very difficult, and it becomes extremely difficult to supply pure water sequentially thawed.
[0030]
On the other hand, in the above-described embodiment, the thawing process of the frozen water is performed by heating with the electric heater 8 provided in the pure water tank 3, so that the flow rates of the hydrogen and the air are reduced as compared with the case of using the combustor. Control becomes unnecessary, and discharge of unburned hydrogen from the combustor can be avoided.
[0031]
When the remaining amount of the secondary battery 10 is not sufficient to defrost the frozen water in the pure water tank 3 at the time of starting the system when the system is stopped, the electric power necessary for operating the electric heater 8 is provided. Is stored in the secondary battery 10, so that even if pure water is frozen, the thawing process can be started, and the system can be reliably started from a sub-zero temperature state. .
[0032]
Further, when the system is stopped, pure water piping of a pure water system serving as a distribution channel of pure water, hydrogen piping of a hydrogen system serving as a distribution channel of hydrogen, and air piping of an air system serving as a distribution channel of air are supplied from the air compressor 7. By purging with the discharged air, it becomes possible to collect the water remaining in the pure water pipe, the hydrogen pipe, and the air pipe in the pure water tank 3, and the water remaining in each pipe is frozen. Partial freezing can be prevented.
[0033]
On the other hand, the total amount of pure water sent to the humidifier 2 is estimated based on the total time during which the load of the motor driving the pure water pump is in a constant state, and the system is started according to the estimation result. Therefore, the operation of the system can be started more quickly than in a case where the thawing of frozen water is determined by a temperature sensor provided in the pure water tank.
[0034]
Further, when the total time during which the load of the motor driving the pure water pump is in a constant state is equal to or longer than a predetermined time, it is determined that all the frozen water in the pure water tank 3 has been thawed, so that freezing is prevented. The determination can be made accurately without relying on a temperature sensor or a level sensor that is difficult to perform.
[0035]
The decrease in the level of the pure water tank 3 during normal operation is also determined by the decrease in the load on the motor driving the pure water pump. If the level decreases, a warning is issued, and the operation to the water recovery mode is performed. May be performed. This makes it possible to determine whether the level of pure water in the pure water tank 3 has fallen without relying on a level sensor or the like that is difficult to prevent freezing. The present invention is also applicable to a system of a type in which a water channel is provided in the fuel cell stack 1 to circulate water and humidify without providing the single humidifier 2.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a fuel cell system according to one embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between the amount of water in a pure water tank 3 and a motor load of a pure water pump 4.
FIG. 3 is a flowchart showing a processing procedure of a stop sequence of the system shown in FIG. 1;
FIG. 4 is a flowchart showing a processing procedure of a startup sequence of the system shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 2 ... Humidifier 3 ... Pure water tank 4 ... Pure water pump 5 ... Hydrogen circulation pump 6 ... Cooling water pump 7 ... Air compressor 8 ... Electric heater 9 ... Converter 10 ... Secondary battery 11 ... Hydrogen pressure regulating valve 12, 13 shut valves 14, 20 valves 15 stack downstream air pressure regulating valve 16 hydrogen supply device 17 purge valve 18 cooling water radiator bypass three-way valve 19 pure water pump suction piping shut valve 21 cooling water stack outlet Thermometer 22 ... Atmospheric thermometer 23 ... Pure water pump outlet piping level sensor 24 ... Radiator

Claims (7)

A fuel cell stack that receives power from hydrogen and air to generate electricity,
A pure water tank for storing pure water necessary for operating the fuel cell system,
A humidifier that humidifies the hydrogen and air supplied to the fuel cell stack,
A pure water pump that takes out the pure water stored in the pure water tank from the pure water tank and circulates through the fuel cell system;
When the pure water stored in the pure water tank is frozen, the fuel cell system has an electric heater that heats the pure water tank and defrosts the frozen water in the pure water tank.
A fuel cell system, wherein the pure water pump is installed at a lower part of the pure water tank, and pure water stored in the pure water tank is taken out from a bottom of the pure water tank. Comprising a secondary battery that stores power generated by the fuel cell stack,
When the fuel cell system is stopped, the electric power supplied to the electric heater for performing the process of heating the electric heater at the next system start-up and defrosting the frozen water in the pure water tank is controlled by the secondary battery. The fuel cell system according to claim 1, wherein the fuel cell system stores the fuel cell. When the fuel cell system is started, without waiting for all the frozen water in the pure water tank to be thawed, the thawed pure water is sequentially supplied to the humidifier to drive the pure water pump. 2. The fuel cell system according to claim 1, wherein it is detected that the pure water tank runs out of pure water due to a decrease in motor load. After the start of the fuel cell system, the supply amount of the pure water taken out from the pure water tank and supplied based on the total of the motor operation times when the load of the motor driving the pure water pump is in a predetermined constant state. 2. The fuel cell system according to claim 1, wherein when the motor operation time reaches a predetermined time or more, the start of the fuel cell system is started. An air compressor that supplies air to the fuel cell stack,
When the fuel cell system is stopped, by the air discharged from the air compressor, a pure water pipe of a pure water system serving as a flow path of pure water, an air system air pipe serving as a flow path of air, and a flow path of hydrogen are provided. 2. The fuel cell system according to claim 1, wherein water remaining in the hydrogen-based hydrogen piping is purged. After the start of the fuel cell system, when the total of the motor operation time in which the load of the motor driving the pure water pump is in a predetermined constant state reaches a predetermined time or more, all the frozen water in the pure water tank is discharged. 2. The fuel cell system according to claim 1, wherein it is determined that the fuel cell stack has been thawed, and the restriction on the power generation output of the fuel cell stack is released. 2. The fuel cell system according to claim 1, wherein freezing of the pure water stored in the pure water tank is determined based on an atmospheric temperature and a load of a motor driving the pure water pump.

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