JP2004063118A - Fuel cell system - Google Patents

Abstract

An object of the present invention is to provide a fuel cell system in which energy consumption during warm-up is suppressed.
The stack includes an antifreeze liquid passage through which an antifreeze passes through the inside of the stack, an antifreeze heating means for heating the antifreeze, and an antifreeze pump for supplying the antifreeze to the antifreeze passage. Further, there are provided switching valves 21 to 24 for switching a flow direction of the antifreeze, and the flow direction of the antifreeze is switched at least once during heating of the stack 1. For example, when the difference between the target warm-up temperature T ₁ and the stack internal inlet temperature T _{in and} the difference between the initial stack warm-up temperature T ₀ and the stack internal outlet temperature T _out become equal, the flow direction of the antifreeze in the stack 1 is changed. Switch.
[Selection] Fig. 2

Description

[0001]
[Industrial applications]
The present invention relates to a fuel cell system, and more particularly to a configuration for warming up a fuel cell stack.
[0002]
[Prior art]
Generally, when the fuel cell system is warmed up (eg, below freezing), a coolant (eg, antifreeze) is heated using a combustor or a heater, and supplied to the stack to warm the stack. Methods of performing the machine are known. In such a method, when the heated refrigerant is supplied from one direction of the stack, a temperature difference occurs between the inlet side and the outlet side of the refrigerant. Therefore, the temperature of the stack cannot be raised uniformly, and the temperature must be raised beyond the target temperature of the warm-up. Therefore, wasteful energy must be supplied to the warm-up of the stack.
[0003]
To cope with such a problem, Japanese Patent Application Laid-Open No. Hei 10-340734 discloses a method of increasing the driving force of the refrigerant pump when the temperature distribution inside the fuel cell stack increases. By increasing the driving force of the refrigerant pump, the flow rate of the cooling water per unit time can be increased, and the temperature difference between the inlet side and the outlet side can be reduced.
[0004]
[Problems to be solved by the invention]
In the conventional fuel cell system, the heated refrigerant is supplied to the fuel cell stack in one direction. Therefore, as shown in FIG.₀Warm-up target temperature T₁When warming up the stack, the temperature becomes high at the inlet side of the stack and becomes low at the outlet side, so that the temperature cannot be raised uniformly in the flow direction of the refrigerant. And the inlet side is the warm-up target temperature T₁The heating target temperature T₁Can not be reached. In such a case, the outlet side is also set to the warm-up target temperature T.₁Must be continued until the temperature exceeds T₁The above-mentioned extra temperature rise is performed, and wasteful energy is consumed.
[0005]
Therefore, in JP-A-10-340734, the driving force of the pump is increased to reduce the temperature distribution on the inlet side and the outlet side. However, in such a method, there is a problem that the power consumption of the pump becomes large and power cannot be generated, or power must be supplied from a large secondary battery at a temperature below freezing point where the amount of power generation is small.
[0006]
In view of the above problems, an object of the present invention is to provide a fuel cell system capable of performing startup with reduced energy consumption.
[0007]
[Means for solving the problem]
The present invention includes a fuel cell stack, a refrigerant path through which a refrigerant passes through the inside of the fuel cell stack, refrigerant heating means for heating the refrigerant, and refrigerant supply means for supplying a refrigerant to the refrigerant path. The fuel cell system further includes switching means for switching the flow direction of the refrigerant, and switching control means for switching the flow direction of the refrigerant at least once during heating of the fuel cell stack.
[0008]
[Action and effect]
By switching the flow direction of the refrigerant at least once during the heating of the fuel cell stack, the high-temperature refrigerant can flow to the low-temperature outlet side, thereby reducing the temperature gradient in the fuel cell stack. Can be. Thereby, the temperature distribution can be averaged without excessively increasing the energy consumption, so that the energy consumed at startup can be reduced.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a schematic view of a refrigerant path of the fuel cell system used in the first embodiment, here, an antifreeze liquid path.
[0010]
The stack 1 is a device that generates power by causing an electrochemical reaction between hydrogen and oxygen. The stack 1 needs to be warmed up at the time of startup when the environmental temperature is below freezing. In the present embodiment, the stack 1 is warmed up by circulating a heated refrigerant, here, an antifreeze.
[0011]
One end of the flow path of the antifreeze in the stack 1 is defined as a first end 33 and the other end is defined as a second end 34. Thermocouples 33 a and 34 a are arranged at the first end 33 and the second end 34, respectively, to detect the temperature of the end in the stack 1. The antifreeze is introduced into the stack 1 from one of the first end 33 and the second end 34 and discharged from the other.
[0012]
The path through which the antifreeze discharged from either the first end 33 or the second end 34 is circulated again to the other (introduction side) is referred to as an antifreeze path 2. The antifreeze passage 2 includes an antifreeze pump 11 for pumping the antifreeze and antifreeze heating means 3 for heating the antifreeze.
[0013]
At the time of startup when the fuel cell needs to be warmed up when the environmental temperature is below freezing, the antifreeze is heated by using the antifreeze heating means 3 to raise the temperature of the fuel cell stack 1, and the antifreeze path 2 is used by using the antifreeze pump 11. Distribute to As the antifreeze heating means 3, for example, a combustor that directly supplies and burns fuel and air used in the fuel cell system, an electric heater, or the like can be considered.
[0014]
Next, the shape of the antifreeze passage 2 will be described.
[0015]
The antifreeze liquid path 2 extends from the first end 33 to the first branch 31, and branches at the first branch 31 toward the first discharge switching valve 21 and the first supply switching valve 22. The second branch 34 extends from the second end 34 to the second branch 34, and branches to the second supply switching valve 23 and the second discharge switching valve 24.
[0016]
The first discharge switching valve 21 side branched from the first branch point 31 and the second discharge switching valve 24 side branched from the second branch point 32 are respectively connected via the first discharge switching valve 21 and the second discharge switching valve 24. To join.
[0017]
After that, it branches to the first supply switching valve 22 side and the second supply switching valve 23 side via the antifreeze liquid pump 11 and the antifreeze liquid heating means 3, and to the first branch point 31 via the first supply switching valve 22, It is connected to the second branch point 32 via the two-supply switching valve 24.
[0018]
The direction of the flow of the antifreeze in the stack 1 is reversed by forming the antifreeze liquid path 2 as described above, alternately using the first end 33 and the second end 34 as an inlet and the other as an outlet. I do. For example, as shown in FIG. 3, the first supply-side switching valve 22 and the second discharge-side switching valve 24 are opened, and the first discharge-side switching valve 21 and the second supply-side switching valve 23 are closed. Thereby, the antifreeze is introduced into the stack 1 from the first end 33 via the first supply-side switching valve 22 and the first branch point 31 after the temperature of the antifreeze is adjusted by the antifreeze heating means 3, and the stack 1 is warmed up. . Thereafter, the water is discharged from the second end 34, introduced into the antifreeze pump 11 via the second branch point 32 and the second discharge side switching valve 24, and circulated again.
[0019]
On the other hand, by making it as shown in FIG. 4, the flow direction of the antifreeze in the stack 1 can be made opposite to the direction of FIG. That is, the second supply-side switching valve 23 and the first discharge-side switching valve 21 are opened, and the second discharge-side switching valve 24 and the first supply-side switching valve 22 are closed. Thus, after the antifreeze liquid is adjusted in temperature by the antifreeze heating means 3, the antifreeze liquid is taken into the stack 1 from the second end portion 34 via the second supply-side switching valve 23 and the second branch point 32 to warm up. Thereafter, the liquid is discharged from the first end 33, introduced into the antifreeze pump 11 via the first branch point 31, and the first discharge side switching valve 21, and circulated again.
[0020]
In the state shown in FIG. 3, the temperature of the first end 33 of the stack 1 becomes high, and the temperature becomes low toward the second end 34. However, when the direction of the antifreeze flow is switched as shown in FIG. Into the second end 34 side. Accordingly, the temperature of the low-temperature portion of the stack 1 can be primarily increased, so that the temperature distribution of the stack 1 can be reduced.
[0021]
Further, the controller 100 controls such a fuel cell system, in particular, the warm-up operation of the stack 1. The output results of the thermocouples 33a and 34a are input to the controller 100 to control the opening and closing of each valve and the rotation speed of the antifreeze liquid pump 11.
[0022]
Next, a control method of the controller 100 when starting up the fuel cell system will be described with reference to a flowchart shown in FIG.
[0023]
When the warm-up operation starts, first, in step S10, the warm-up target temperature T₁Set. In addition, the temperature T inside the stack 1 before the warm-up is performed.₀Is measured using one of the thermocouples 33a and 34a. Here, immediately after the start of the activation, almost the same value is detected regardless of which of the thermocouples 33a and 34a is measured, and either thermocouple may be used.
[0024]
Next, in step S11, heating of the antifreeze by the antifreeze heating means 3 is started. In addition, as shown in FIG. 3, by opening only the first supply-side switching valve 22 and the second discharge-side switching valve 24, the antifreeze flows from the first end 33 to the second end 34. Subsequently, in step S12, using the thermocouple 33a, the stack internal inlet temperature T, which is the internal temperature of the antifreeze liquid inlet of the stack 1, is used._inThe stack internal outlet temperature T, which is the internal temperature of the antifreeze liquid outlet of the stack 1 using the thermocouple 34a._outIs detected.
[0025]
Next, in step S13, T_inAnd T₁− (T_out-T₀) To determine the magnitude. T_inIs T₁− (T_out-T₀If it is determined that the following, the flow returns to step S12, and the stack internal inlet / outlet temperature T is returned again._in, T_outMeasurement. T_inIs T₁− (T_out-T₀) Continue warming up in that state until it becomes_inIs T₁− (T_out-T₀If it is determined to be larger than the above, the process proceeds to step S14, and the flow direction of the antifreeze is switched. Here, in order to switch as shown in FIG. 3 to FIG. 4, the first supply side switching valve 22 and the second discharge side switching valve 24 are closed, and the second supply side switching valve 23 and the first discharge side switching valve 21 are opened.
[0026]
When the direction of flow of the antifreeze liquid is switched in this way, in step S15, the stack internal entrance temperature T_inIs detected. In step S16, the stack internal inlet temperature T_inIs the warm-up target temperature T₁Determine if it has been reached. Warm-up target temperature T₁If not, the process returns to step S15 to continue warming up. In step S16, the stack internal inlet temperature T_inIs the warm-up target temperature T₁Is reached, the process proceeds to step S17, the antifreeze heating means 3 is stopped, and the warm-up is ended.
[0027]
Thus, the stack internal inlet temperature T_inIs T₁− (T_out-T₀9), the flow direction of the antifreeze can be switched at a temperature at which the area of the trapezoid ABFE and the area of the trapezoid CDEF become the same as shown in FIG. Here, the area of the trapezoidal ABFE indicates the amount of heat already given to the stack 1, and the area of the trapezoidal CDEF indicates the remaining amount of heat to be given to the stack 1. Therefore, it is necessary to switch the flow direction of the antifreeze at a temperature at which these amounts become the same. become. Thus, useless warm-up can be avoided with the least number of switching valves and with the least number of switching times.
[0028]
Next, effects of the present embodiment will be described.
[0029]
This embodiment includes a stack 1, an antifreeze passage 2 for flowing antifreeze through the stack 1, an antifreeze heating means 3 for heating the antifreeze, and an antifreeze supply means for supplying antifreeze to the antifreeze passage 2, here, an antifreeze pump 11. , Is provided. Further, there are provided switching valves 21 to 24 as switching means for switching the flow direction of the antifreeze, and during the heating of the stack 1, the flow direction of the antifreeze is switched at least once in step S14. By switching the flow direction, a high-temperature antifreeze solution can be supplied to the outlet side at a low temperature, so that the temperature distribution in the flow direction of the antifreeze solution in the stack 1 can be reduced. Thus, it is possible to suppress unnecessary warm-up of the stack 1 at the time of startup, and it is possible to reduce energy consumption during warm-up.
[0030]
Here, the stack internal inlet temperature T_inIs provided with a stack entrance temperature detecting means for estimating or detecting the temperature of the fuel cell, here a thermocouple 33a. Here, the number of times of switching is one, and the thermocouple 33a is in the state immediately after the start-up as shown in FIG. 3, the thermocouple 34a is in FIG. 4, and the thermocouples 33a, 34a are in the stacked state if the number of times of switching is plural. It corresponds to an inlet temperature detecting means.
[0031]
The stack inlet temperature T is determined by the stack inlet temperature detecting means._inIs detected, and when the temperature exceeds a predetermined temperature, the flow direction of the antifreeze, particularly the flow direction of the antifreeze flowing in the stack 1 is switched. As a result, the internal temperature of the stack 1 becomes the warm-up target temperature T.₁It is possible to suppress the above, and to reduce unnecessary heating energy.
[0032]
Here, the warm-up target temperature T of the stack 1₁And set the warm-up target temperature T₁And stack internal inlet temperature T_in, And the temperature T of the stack 1 at the beginning of warm-up₀And stack internal outlet temperature T_outWhen the temperature difference becomes equal, the flow direction of the antifreeze is switched. Thereby, the flow direction of the antifreeze can be switched at the time when the amount of heat already supplied from the antifreeze to the stack 1 is equal to the amount of heat to be supplied, and wasteful energy consumption can be efficiently reduced by one switching.
[0033]
Further, since the refrigerant is used as the fluid for warming up the stack 1, it is possible to warm up with the existing configuration, and by using the antifreeze liquid as the refrigerant, it is not necessary to defrost the refrigerant, and the amount of energy consumed at the time of warming up can be reduced. At the same time, the startup time can be reduced.
[0034]
Further, the above effects can be realized with a simple configuration of only the shape of the antifreeze liquid path 2 and the switching valves 21 to 24, and can be realized at low cost.
[0035]
Note that it goes without saying that the state shown in FIG. 3 and the state shown in FIG. 4 may be in any order, and the state shown in FIG. Also, the end of the warm-up is determined based on the stack internal inlet temperature T._inThe stack internal outlet temperature T_outMay be determined by Furthermore, the internal temperature T of the antifreeze liquid inlet / outlet of the stack 1_in, T_outAre provided, but if the temperature distribution inside the stack 1 can be estimated, the temperature at any point of the temperature inside the stack 1 may be detected. In this case, the stack internal inlet / outlet temperature T is calculated from the detected internal temperature of the stack 1._in, T_outIs estimated, the same control as in the present embodiment can be performed. When the internal temperature of the stack 1 can be estimated from the temperature of the antifreeze discharged from the stack 1 or the like, the temperature of the antifreeze may be detected.
[0036]
Further, the configuration for obtaining the above-described effects is not limited to FIG. 2. For example, a method using the three-way valves 25 and 26 as shown in FIG. 5 or a reverse rotation as shown in FIG. 6. A method of using the operable antifreeze pump 12 is also conceivable.
[0037]
5, a three-way valve 25 is arranged at a first branch point 31 instead of the switching valves 21 and 22 in FIG. 2, and a three-way valve 26 is arranged at a second branch point 32 instead of the switching valves 23 and 24. The sides of the three-way valves 25 and 26 to which the antifreeze is supplied are referred to as suction portions 25a and 26a, the side facing the stack 1 is referred to as end portions 25c and 26c, and the other discharge side is referred to as discharge portions 25b and 26b. In the three-way valve 25, the suction part 25a and the end part 25c are circulated, and in the three-way valve 26, the end part 26c and the discharge part 26b communicate. With this setting, the antifreeze can flow from the first end 33 to the second end 34 in the stack 1 as in FIG.
[0038]
On the other hand, in the three-way valve 26, the suction portion 26a communicates with the end portion 26c, and in the three-way valve 25, the end portion 25c communicates with the discharge portion 25b. It can be set to flow from the end 34 to the first end 33.
[0039]
In FIG. 6, the first end 33 and the second end 34 of the stack 1 are connected to the antifreeze pump 12 capable of reverse rotation operation. Thus, the state of FIGS. 3 and 4 can be switched by reversing the rotation of the antifreeze pump 12.
[0040]
Next, a second embodiment will be described. The refrigerant path of the fuel cell system used here has the same configuration as in the first embodiment (FIGS. 2 to 4). FIG. 8 is a flowchart showing the control of this embodiment.
[0041]
When the warm-up operation is started, first, in steps S20 to S22, similarly to steps S10 to S12 in FIG.₁And the stack internal temperature T₀Is measured, and after the heating / supply of the antifreeze liquid is started, the inlet / outlet temperature T inside the stack is measured._in, T_outIs detected. In step S3, T_outAnd (T₁-T_in) + T₀Judge the magnitude relationship with T_outIs smaller, the process returns to step S22 and again T_in, T_outAnd repeat it. T_outIs (T₁-T_in) + T₀The warm-up is continued as it is until it becomes larger, and at step S23 T_outIs determined to be larger, the process proceeds to step S24.
[0042]
Next, in step S24, the flow direction of the antifreeze flowing through the stack 1 is switched by switching the switching valve as shown in FIGS.
[0043]
After switching the direction of the flow of the antifreeze, in steps S25 to S27, similarly to steps S15 to S17 in the first embodiment, the warm-up target temperature T is set.₁Until the warm-up target temperature T₁When it reaches, finish the warm-up.
[0044]
By operating in this manner, the antifreeze liquid becomes equal to the area of the trapezoidal ABFE in FIG. Switch the direction of distribution. Here, the stack internal outlet temperature T_outIs (T₁-T_in) + T₀At the point in time, since the heat quantity given as described above and the remaining heat quantity become equal, T_outIs (T₁-T_in) + T₀When it becomes larger, the flow direction of the antifreeze is switched. Thus, unnecessary warm-up can be avoided with the least number of switching of the switching valve.
[0045]
Next, effects of the present embodiment will be described.
[0046]
Stack internal outlet temperature T_outIs provided with a stack outlet temperature detecting means for estimating or detecting the temperature of the fuel cell, here a thermocouple 34a. Here, the number of times of switching is one, and the thermocouple 34a if the state immediately after startup is as shown in FIG. 3, the thermocouple 33a if it is as shown in FIG. 4, and the thermocouples 33a and 34a if the number of times of switching is plural. Corresponds to the stack outlet temperature detecting means.
[0047]
Stack outlet temperature T by stack outlet temperature detecting means_outAnd T_outSwitches the flow direction of the antifreeze when the temperature exceeds a predetermined temperature. As a result, the internal temperature of the stack 1 becomes the target temperature T for warm-up.₁It is possible to suppress the above, and to reduce wastefully consumed energy.
[0048]
Further, similarly to the first embodiment, the warm-up target temperature T₁And stack internal inlet temperature T_inAnd the stack internal outlet temperature T at the beginning of warm-up_outWhen the temperature difference becomes equal, the flow direction of the antifreeze is switched. Thereby, the flow direction of the antifreeze can be switched at the time when the amount of heat already supplied from the antifreeze to the stack 1 is equal to the amount of heat to be supplied, and wasteful energy consumption can be efficiently reduced by one switching.
[0049]
Note that this embodiment can also be applied to the fuel cell system as shown in FIGS. 5 and 6, similarly to the first embodiment.
[0050]
Next, a third embodiment will be described. The configuration of the fuel cell system is the same as that of the first embodiment. However, thermocouples 33b and 34b for detecting the temperature of the flowing antifreeze are further disposed at the ends 33 and 34. FIG. 10 shows a control flow used in the present embodiment.
[0051]
When the warm-up starts, the process proceeds to step S30. Similar to step S10, the warm-up target temperature T₁And the stack internal temperature T₀Is measured. In step S31, the stack 1 is set to the temperature T.₀To T₁Heat required to warm up to Q_stackIs the heat capacity C of the stack 1 measured in advance through experiments and the like._stackAnd temperature difference (T₁-T₀).
[0052]
In step S32, the heating of the antifreeze is started as in step S11, and the switching valve is set as shown in FIG. At step S33, the antifreeze inlet temperature T, which is the temperature of the antifreeze flowing into the stack 1 from the thermocouple 33b._in__LLCAnd the antifreeze outlet temperature T which is the temperature of the antifreeze flowing out of the stack 1 from the thermocouple 34b._out__LLCIs measured.
[0053]
Proceeding to step S34, the mass flow rate G of the antifreeze liquid_LLCIs measured. For example, a flow sensor or the like may be provided, but here, it can be obtained from the rotation speed of the antifreeze pump 11 or the like. Next, in step S35, the amount of heat transferred from the antifreeze to the stack 1 is determined by the specific heat C_P__LLCAnd antifreeze mass flow rate G_LLCAnd temperature difference (T_in__LLC-T_out__LLC) And time integration.
[0054]
Subsequently, in step S36, the amount of heat Q transferred from the antifreeze to the stack 1_{LL C}Heat required to warm up stack 1_stackTo determine if it exceeds half. Q_LLCIs Q_stackIf it does not exceed / 2, the process returns to step S33, and the amount of heat Q transferred from the antifreeze to the stack 1 again._LLCAsk for.
[0055]
In step S36, Q_LLCIs Q_stackIf / 2 is exceeded, the process proceeds to step S37, and the switching valve is switched as shown in FIG. 4 to switch the flow direction of the antifreeze flowing in the stack 1.
[0056]
After switching the direction of the flow of the antifreeze, in steps S38 to S40, similarly to steps S15 to S17 in the first embodiment, the warm-up target temperature T is set.₁Until the warm-up target temperature T₁When it reaches, finish the warm-up.
[0057]
With the above operation, the flow direction of the antifreeze can be switched when the stack 1 is half warmed up, and unnecessary warming up can be avoided with the least number of switching of the switching valve.
[0058]
Next, effects of the present embodiment will be described.
[0059]
Antifreeze inlet temperature detecting means for detecting the temperature of antifreeze at the antifreeze inlet of the stack 1, here a thermocouple 33b, and antifreeze outlet temperature detecting means for detecting the temperature of antifreeze at the antifreeze outlet of the stack 1, here thermocouple 34b Is provided. Further, there is provided a calorie calculating means (corresponding to step S35) for calculating heat transferred from the antifreeze to the stack 1 from the inlet temperature and the outlet temperature of the antifreeze. When the amount of heat transferred from the antifreeze to the stack 1 exceeds a predetermined value, the flow direction of the antifreeze is switched. As a result, the amount of heat transferred from the antifreeze to the stack 1 causes the stack 1 to warm₁Since it is possible to avoid the amount of heat required to warm up to the maximum, it is possible to reduce energy consumption at the time of warming up.
[0060]
Further, as in the operation in step S31, the total amount of heat Q transferred from the antifreeze until the stack 1 is warmed up._stackIs calculated, and the amount of heat transferred from the antifreeze to the stack 1 is determined by the total heat amount Q._stackIf it exceeds half of the value, switch the flow direction of the antifreeze. Thereby, the flow direction of the antifreeze liquid is switched when the stack 1 is half warmed up, so that unnecessary warming up can be avoided with the least number of switching times, and energy consumption can be reduced.
[0061]
Next, a fourth embodiment will be described. The configuration of the fuel cell system is the same as that of the first embodiment, and control for switching the flow direction of the antifreeze will be described with reference to the flowchart of FIG. Here, the stack internal inlet temperature T_inAnd stack internal outlet temperature T_outThe temperature distribution in the stack 1 is suppressed by suppressing the temperature difference from the temperature difference to a predetermined value.
[0062]
After the warm-up operation is started, in step S50, the warm-up target temperature T₁Set. In step S51, heating of the antifreeze is started, and the switching valve is set as shown in FIG. 3 to start supplying the antifreeze to the stack 1.
[0063]
In step S52, the stack internal inlet temperature T is obtained from the thermocouple 33a._inAnd a stack internal outlet temperature T using a thermocouple 34a._outIs detected. Next, in step S53, the temperature difference (T_in-T_out) Exceeds a predetermined temperature, for example, 2 ° C. Steps S52 and S53 are repeated until the temperature exceeds a predetermined temperature. If it is determined in step S53 that the temperature has exceeded, the process proceeds to step S54.
[0064]
In step S54, the flow direction of the antifreeze in the stack 1 is switched by switching the switching valve as shown in FIG. Next, in step S55, T_outAnd T₁Compare the size with_out> T₁If so, it is determined that further warm-up is necessary, and the process returns to step S52.
[0065]
While the steps S52 to S55 are repeated in this way, that is, during warm-up, the stack internal inlet / outlet temperature T_in, T_outWhen the temperature difference becomes larger than a predetermined temperature, here 2 ° C., the control for switching the flow direction of the antifreeze is repeated. However, when the flow of the antifreeze is in the state of FIG. 4, the output of the thermocouple 33a is set to T._out, The output of the thermocouple 34a is T_inAnd In step S55, T_outIs T₁If it is determined that the above has been reached, the process proceeds to step S56, in which the antifreeze liquid heating means 3 is stopped and the warm-up is ended. Here, the end of the warm-up operation is determined by the stack internal inlet temperature T_inIs the warm-up target temperature T₁May be determined based on whether or not the number has been reached.
[0066]
By operating as described above, the temperature distribution inside the stack 1 can be maintained at a predetermined temperature (for example, 2 ° C.) or lower, and a uniform temperature rise within the predetermined temperature becomes possible.
[0067]
Next, effects of the present embodiment will be described.
[0068]
Stack internal inlet temperature T at the antifreeze inlet of stack 1_inTemperature detection means for detecting the temperature of the stack, here the thermocouple 33a or 34a, and the stack internal temperature T_out, A thermocouple 34a or 33a in this case. Stack internal inlet temperature T_inAnd stack internal outlet temperature T_outWhen the temperature difference with the temperature exceeds the predetermined value, the flow direction of the antifreeze is switched.
[0069]
By performing such control, the internal temperature difference between the entrance and exit of the antifreeze of the stack 1 can be suppressed to about a predetermined value, and the temperature distribution in the stack 1 can be suppressed, so that the temperature can be uniformly increased. it can. This makes it possible to reduce wasteful energy consumption when raising the temperature of the entire stack 1 due to the temperature distribution generated in the stack 1 at the time of warming-up, so that efficient warming-up can be performed.
[0070]
Next, a fifth embodiment will be described. The configuration of the fuel cell system used in the present embodiment, particularly the cooling system of the stack 1, is the same as that of the first embodiment, and the control regarding the flow of the antifreeze during warm-up is shown in the flowchart of FIG.
[0071]
Here, when the flow direction of the antifreeze is switched by a valve as shown in FIGS. 2 and 5, it is impossible to switch the valve at the instant of time 0. Therefore, while the valve is being switched, the flow rate of the antifreeze flowing through the antifreeze heating means 3 becomes slow, causing a local temperature rise of the antifreeze and temporary heating of the heating means. Further, even when the flow direction is switched using the antifreeze pump 12 capable of reverse rotation as shown in FIG. 6, the flow rate of the antifreeze flowing through the antifreeze heating means 3 during the period from the normal rotation to the reversal of the antifreeze pump 12 becomes slow. As a result, local heating of the antifreeze and temporary rise in the temperature of the antifreeze heating means 3 occur.
[0072]
Therefore, in the present embodiment, in order to reduce such a temperature distribution of the antifreeze, the output of the antifreeze heating means 3 is reduced while the flow direction of the antifreeze is switched. Here, the time t from when the flow direction of the antifreeze liquid is switched to decrease the flow rate until the flow rate returns to the same flow rate as before the switching is returned._shtmrIs obtained in advance by an experiment or the like, and stored in the controller 100. When the output of the antifreeze heating means 3 is reduced, the timer value t_mrA timer is built in to reset and start counting.
[0073]
Next, a control flow during warm-up will be described with reference to the flowchart in FIG.
[0074]
Steps S10 to S14 are the same as in the first embodiment. If the flow direction of the antifreeze is switched in step S14, the output of the antifreeze heating means 3 is reduced in step S65. As the output reduction method, when the antifreeze heating means 3 is a combustor, the supplied fuel is reduced, and when the antifreeze heating means 3 is an electric heater, the supply power is reduced.
[0075]
In step S66, the timer value t of the timer built in the controller 100_mrIs a predetermined value t_sthmrIs determined. Timer value t_mrIs a predetermined value t_shtmrCounting, and if so, the process proceeds to step S67 to recover the output of the antifreeze heating means 3.
[0076]
Thereafter, in steps S15 to S17, as in the first embodiment, the stack internal inlet temperature T_inIs the warm-up target temperature T₁Until the warm-up target temperature T₁Is reached, the antifreeze heating means 3 is stopped and the warm-up is finished.
[0077]
Next, effects of the present embodiment will be described. Here, only the effects different from those of the first embodiment will be described.
[0078]
While switching the flow direction of the antifreeze, the amount of heat transferred to the antifreeze in the antifreeze heating means 3 is reduced. When the flow direction is switched, the flow rate of the antifreeze is reduced and the antifreeze flowing through the antifreeze heating means 3 is locally heated. Temperature rise can be avoided. Thereby, it is possible to prevent the temperature of the stack 1 from locally increasing, and to perform a stable warm-up.
[0079]
Here, the time t during which the output of the antifreeze heating means 3 is suppressed is t_sthmrIs determined in advance by experiments or the like, but the flow rate sensor or the like detects the flow rate of the antifreeze supplied to the stack 1 and controls the output of the antifreeze heating means 3 to return to normal when the flow rate of the antifreeze becomes equal to that before switching. You can also.
[0080]
Further, in the present embodiment, the determination of the switching of the antifreeze liquid flowing direction is the same as that of the first embodiment, but the determination can be applied to the switching flow of the second to fourth embodiments.
[0081]
As described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.
[Brief description of the drawings]
FIG. 1 is a distribution diagram of a stack internal temperature when a conventional fuel cell system is warmed up.
FIG. 2 is a configuration diagram of a part of the fuel cell system according to the first embodiment.
FIG. 3 is a first explanatory diagram of antifreeze flow control according to the first embodiment;
FIG. 4 is a second explanatory diagram of the flow control of the antifreeze according to the first embodiment.
FIG. 5 is a configuration example having effects similar to those of the fuel cell system according to the first embodiment.
FIG. 6 is a configuration example having the same replacement as the fuel cell system of the first embodiment.
FIG. 7 is a flowchart of antifreeze liquid flow control according to the first embodiment.
FIG. 8 is a flowchart of the flow control of the antifreeze in the second embodiment.
FIG. 9 is an explanatory diagram of the amount of heat transferred from the antifreeze to the stack in the second embodiment.
FIG. 10 is a flowchart of antifreeze flow control in the third embodiment.
FIG. 11 is a flowchart of antifreeze liquid flow control according to a fourth embodiment.
FIG. 12 is a flowchart of a flow control of antifreeze in a fifth embodiment.
[Explanation of symbols]
1 stack (fuel cell stack)
2) Antifreeze route
3) Antifreeze heating means
11 Antifreeze pump (refrigerant supply means)
12 Antifreeze liquid pump (refrigerant liquid supply means, switching means)
21 # First discharge side switching valve (switching means)
22 First supply side switching valve (switching means)
23 Second supply side switching valve (switching means)
24 ° second discharge side switching valve (switching means)
25 mm three-way valve (switching means)
26 three-way valve (switching means)
33a, 34a thermocouple (stack inlet temperature detecting means or stack outlet temperature detecting means)
33b, 34b thermocouple (antifreeze liquid inlet temperature detecting means or antifreeze liquid outlet temperature detecting means)
Switching control means S14, S24, S37, S54
Calorific value calculation means S35
Total calorie calculation means S31
Target warm-up setting means S10, S20, S30, S50

Claims (9)

A fuel cell stack,
A refrigerant path for passing a refrigerant inside the fuel cell stack,
Refrigerant heating means for heating the refrigerant,
Refrigerant supply means for supplying a refrigerant to the refrigerant path,
Switching means for switching the flow direction of the refrigerant in the fuel cell stack,
Switching control means for switching the flow direction of the refrigerant in the fuel cell stack at least once during the heating of the fuel cell stack. The fuel cell stack further includes a stack inlet temperature detecting unit that estimates or detects an internal temperature at an inlet portion of a refrigerant of the fuel cell stack,
The stack inlet temperature detecting means estimates or detects the internal temperature at the refrigerant inlet of the fuel cell stack. The fuel cell system according to claim 1, wherein the direction is switched. The fuel cell stack further includes a stack outlet temperature detecting unit that estimates or detects an internal temperature at an outlet of a refrigerant of the fuel cell stack,
The internal temperature at the refrigerant outlet of the fuel cell stack is estimated or detected by the stack outlet temperature detecting means, and when the internal temperature of the refrigerant outlet exceeds a predetermined temperature, circulation of the refrigerant in the fuel cell stack is performed. The fuel cell system according to claim 1, wherein the direction is switched. A warm-up target temperature setting means for setting a warm-up target temperature of the fuel cell stack;
Stack inlet temperature detecting means for estimating or detecting the internal temperature at the inlet of the refrigerant of the fuel cell stack,
Stack exit temperature detection means for estimating or detecting the internal temperature at the outlet of the refrigerant of the fuel cell stack,
The temperature difference between the warm-up target temperature and the internal temperature at the refrigerant inlet of the fuel cell stack is equal to the temperature difference between the internal temperature of the fuel cell stack and the internal temperature at the refrigerant outlet at the initial stage of warm-up. 2. The fuel cell system according to claim 1, wherein the flow direction of the refrigerant in the fuel cell stack is switched. Refrigerant inlet temperature detecting means for detecting the temperature of the refrigerant at the refrigerant inlet of the fuel cell stack,
Refrigerant outlet temperature detecting means for detecting the temperature of the refrigerant at the refrigerant outlet of the fuel cell stack,
Calorific value calculating means for calculating heat transferred from the refrigerant to the fuel cell stack from the refrigerant inlet temperature and the refrigerant outlet temperature,
2. The fuel cell system according to claim 1, wherein a flow direction of the refrigerant in the fuel cell stack is switched when an amount of heat transferred from the refrigerant to the fuel cell stack exceeds a predetermined value. A total calorie calculation means for calculating a total calorie moving from the refrigerant before warming up the fuel cell stack,
6. The fuel cell system according to claim 5, wherein a flow direction of the refrigerant in the fuel cell stack is switched when an amount of heat transferred from the refrigerant to the fuel cell stack exceeds half of the total amount of heat. Stack inlet temperature detecting means for estimating or detecting the internal temperature at the refrigerant inlet of the fuel cell stack,
Stack exit temperature detection means for estimating or detecting the internal temperature at the refrigerant outlet of the fuel cell stack,
2. The fuel cell system according to claim 1, wherein a flow direction of the refrigerant in the fuel cell stack is switched when a difference between an output value of the stack inlet temperature detecting unit and an output value of the stack outlet temperature detecting unit exceeds a predetermined value. The fuel cell system according to any one of claims 1 to 7, wherein the amount of heat transferred to the refrigerant in the refrigerant heating unit is reduced while switching a flow direction of the refrigerant. 9. The fuel cell system according to claim 1, wherein an antifreeze is used as the refrigerant.

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