fuel cell system

Abstract

The present disclosure provides a fuel cell system that can cool a fuel cell while effectively utilizing the exhaust heat after cooling the fuel cell. [Solution] A fuel cell system comprising: a solid polymer fuel cell that generates electricity by chemically reacting hydrogen and oxygen and is cooled by a first cooling medium; a cooling device that supplies a second cooling medium that cools the first cooling medium; a first intermediate heat exchanger that performs heat exchange between the first cooling medium and the second cooling medium; and a control unit that controls the fuel cell and the cooling device, wherein the control unit controls the cooling capacity of the cooling device so that the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature when refreshing the fuel cell.

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Patent Document 1 discloses that the cooling capacity of the fuel cell is increased before the time period in which the fuel cell performs output fluctuation operation in order to reduce the possibility of insufficient cooling capacity at the start of the time period in which output fluctuation operation is performed. Patent Document 2 discloses that the flow rate of the cooling water that cools the fuel cell needs to be increased to an amount suitable for the high output state before the fuel cell reaches the high output state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7477037 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-053168 Summary of the Invention [Problem to be solved by the invention]

[0004] In some cases, the exhaust heat generated when cooling a fuel cell can be recovered and used as heat. However, when the fuel cell is cooled, the temperature of the exhaust heat drops, and in some cases, it is not possible to fully recover the heat as a heat source.

[0005] The present disclosure provides a fuel cell system that can cool a fuel cell while effectively utilizing the exhaust heat after cooling the fuel cell. [Means for solving the problem]

[0006] The present disclosure provides a fuel cell system comprising: a polymer electrolyte fuel cell that generates electricity by chemically reacting hydrogen and oxygen and is cooled by a first cooling medium; a cooling device that supplies a second cooling medium that cools the first cooling medium; a first intermediate heat exchanger that performs heat exchange between the first cooling medium and the second cooling medium; and a control unit that controls the fuel cell and the cooling device, wherein the control unit controls the cooling capacity of the cooling device so that the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature when refreshing the fuel cell. [Effects of the Invention]

[0007] According to the fuel cell system of the present disclosure, it is possible to cool the fuel cell while effectively utilizing the exhaust heat generated after cooling the fuel cell. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an outline of the configuration of a fuel cell system according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an outline of the configuration of a fuel cell system according to the second embodiment. [Figure 6] FIG. 6 is a diagram illustrating the operation of the fuel cell system according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing an outline of the configuration of a fuel cell system according to the third embodiment. [Figure 8] FIG. 8 is a diagram showing an outline of the configuration of a fuel cell system according to a fourth embodiment. [Figure 9]FIG. 9 is a diagram showing an outline of the configuration of a fuel cell system according to a fifth embodiment. [Figure 10] FIG. 10 is a diagram showing an outline of the configuration of a fuel cell system according to a sixth embodiment. [Figure 11] FIG. 11 is a diagram showing an outline of the configuration of a fuel cell system according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0010] In the description of the specification and drawings of each embodiment, components having substantially the same or corresponding functional configurations may be designated by the same reference numerals to avoid redundant explanation. In addition, the scale of each part in the drawings may differ from the actual scale to facilitate understanding.

[0011] First Embodiment A fuel cell system according to a first embodiment will be described. The fuel cell system according to the first embodiment includes a polymer electrolyte fuel cell that generates electricity by chemically reacting hydrogen and oxygen and is cooled by a first cooling medium, and a cooling device that supplies a second cooling medium that cools the first cooling medium. The fuel cell system according to the first embodiment also includes a first intermediate heat exchanger that exchanges heat between the first cooling medium and the second cooling medium, and a control unit that controls the fuel cell and the cooling device. The control unit in the fuel cell system according to the first embodiment controls the cooling capacity of the cooling device when performing refresh operation of the fuel cell so that the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature.

[0012] FIG. 1 is a diagram showing an outline of the configuration of a fuel cell system 1, which is an example of a fuel cell system according to a first embodiment.

[0013] The fuel cell system 1 is a fuel cell that uses fuel cells. The fuel cell system 1 is a chemical battery that converts chemical energy into electricity by reacting hydrogen with oxygen in the air as fuel. The fuel cell system 1 outputs an output Pdc, which is DC power, to an external load or the like.

[0014] The fuel cell system 1 includes a fuel cell 10, a cooling device 20, a pump 30, an intermediate heat exchanger 40, a control unit 50, and a waste heat utilization device 70.

[0015] [Fuel cell 10] The fuel cell 10 generates electricity by causing a chemical reaction between hydrogen and oxygen. That is, the fuel cell 10 generates electricity by causing a chemical reaction between supplied hydrogen and oxygen contained in the air.

[0016] The fuel cell 10 includes a fuel cell stack. The fuel cell stack generates electricity by chemically reacting supplied hydrogen with oxygen contained in the air. The fuel cell stack is, for example, a polymer electrolyte fuel cell (PEFC). The fuel cell stack, which is a polymer electrolyte fuel cell, has a stack structure in which a large number of unit cells (fuel cell units) are stacked.

[0017] A unit cell in a fuel cell stack, which is a polymer electrolyte fuel cell, includes a membrane electrode assembly (MEA) that includes a polymer electrolyte membrane and a pair of electrodes provided on both sides of the polymer electrolyte membrane. One of the pair of electrodes is an air electrode, and the other is a fuel electrode. The polymer electrolyte membrane selectively transports hydrogen ions. Each electrode is made of a porous material. Each of the pair of electrodes includes a catalyst layer primarily composed of carbon powder that supports a platinum-based metal catalyst (electrode catalyst), and a gas diffusion layer that is both breathable and electronically conductive. Furthermore, the unit cell includes a pair of separators that sandwich the membrane electrode assembly (MEA) from both sides.

[0018] The fuel cell 10 outputs an output Pdc that is DC power. The fuel cell 10 is connected in parallel to a power storage unit 80 and a power conditioner 90. The power storage unit 80 may store electricity supplied from an external power source, or may supply the stored electricity to an external device as needed. The power storage unit 80 charges when there is excess power from the fuel cell 10 to the power conditioner 90. The power storage unit 80 discharges when there is a shortage of power from the fuel cell 10 to the power conditioner 90.

[0019] The power storage unit 80 includes, for example, a lithium ion capacitor, a lithium ion battery, an electric double layer capacitor, or an all-solid-state battery.

[0020] For example, if the output Pdc of the fuel cell 10 is in excess of the requirements of the power conditioner 90, the excess power Pbt is stored. Also, if the output Pdc of the fuel cell 10 is insufficient to the requirements of the power conditioner 90, the shortage power Pbt is discharged.

[0021] The power conditioner 90 converts input DC power into output Pac, which is AC power, and outputs it to an external load or the like.

[0022] [Cooling device 20] The cooling device 20 cools the cooling medium RF1. The cooling device 20 is, for example, a cooling tower. The cooling device 20 includes a fan 21. The rotation speed of the fan 21 is controlled to control the temperature of the cooling medium RF1 supplied from the cooling device 20.

[0023] For example, the control unit 50 measures the temperature of the cooling medium RF1 using the thermometer 61. Then, the control unit 50 controls the rotation speed of the fan 21 so that the temperature of the cooling medium RF1 becomes a desired temperature.

[0024] The cooling medium RF1 is, for example, water. The cooling medium RF1 may be, for example, water containing antifreeze or the like. The cooling medium RF1 may be, for example, tap water, well water, river water, seawater, or the like. The cooling device 20 may also be a cooling device using a refrigeration cycle.

[0025] [Pump 30] The pump 30 causes the cooling medium RF1 supplied from the cooling device 20 to flow through the intermediate heat exchanger 40. The pump 30 is, for example, an axial flow pump. The rotation speed of the pump 30 is controlled by an inverter 31. The inverter 31 is, for example, a variable voltage variable frequency (VVVF (Variable Voltage Variable Frequency) type) inverter. The inverter 31 is not limited to a variable voltage variable frequency type inverter, and other types may also be used. The inverter 31 is controlled by a control unit 50. The control unit 50 controls the inverter 31 so that the flow rate of the cooling medium RF1 becomes a desired flow rate.

[0026] [Intermediate heat exchanger 40] The intermediate heat exchanger 40 exchanges heat between the cooling medium RF1 supplied from the cooling device 20 and the cooling medium RF2 that cools the fuel cell 10. The intermediate heat exchanger 40 is, for example, a plate-type heat exchanger. The cooling medium RF2 discharged from the fuel cell 10 is sent to the intermediate heat exchanger 40 by a pump 11.

[0027] The cooling medium RF2 that cools the fuel cell 10 is, for example, water or antifreeze. It is desirable that the cooling medium RF2 be water or antifreeze that contains as few impurities as possible, such as ions, so as not to affect the fuel cell 10. The fuel cell system 1 may be provided with an impurity removal device to remove impurities contained in the cooling medium RF2.

[0028] The temperatures of the cooling medium RF1 and the cooling medium RF2 in the fuel cell system 1 will be described. The temperature of the cooling medium RF1 supplied from the cooling device 20 to the intermediate heat exchanger 40 is, for example, 45°C. The temperature of the cooling medium RF2 supplied from the intermediate heat exchanger 40 to the fuel cell 10 is, for example, 50°C. The temperature of the cooling medium RF2 discharged from the fuel cell 10 to the intermediate heat exchanger 40 is, for example, 65°C. The temperature of the cooling medium RF2 discharged from the fuel cell 10 to the intermediate heat exchanger 40 varies depending on the operating load of the fuel cell 10. The temperature of the cooling medium RF2 discharged from the fuel cell 10 to the intermediate heat exchanger 40 is, for example, 65°C in the case of partial load and 80°C in the case of rated load. The temperature of the cooling medium RF1 returned from the intermediate heat exchanger 40 to the cooling device 20 is, for example, 60°C.

[0029] [Waste heat utilization equipment 70] The exhaust heat utilization device 70 recovers the exhaust heat of the fuel cell 10. Specifically, the exhaust heat utilization device 70 recovers the heat of the cooling medium RF1 to generate, for example, hot water. The exhaust heat utilization device 70 includes, for example, a heat exchanger that exchanges heat between the water to be heated and the cooling medium RF1.

[0030] In order for the exhaust heat utilization device 70 to utilize the exhaust heat of the fuel cell 10, the temperature of the cooling medium RF1 supplied from the intermediate heat exchanger 40 to the exhaust heat utilization device 70 is preferably a desired target temperature, for example, 60°C or higher.

[0031] [Control unit 50] The control unit 50 controls the fuel cell system 1. The control unit 50 controls the fuel cell 10, the cooling device 20, and the inverter 31. The control unit 50 also acquires temperatures from the thermometers 61 and 62.

[0032] The control unit 50 controls the cooling device 20 so that the temperature of the cooling medium RF1 discharged from the cooling device 20 becomes a desired temperature. Specifically, the control unit 50 acquires the temperature of the cooling medium RF1 using a thermometer 61. Then, the control unit 50 controls, for example, the rotation speed of the fan 21 provided in the cooling device 20 so that the temperature of the cooling medium RF1 measured by the thermometer 61 becomes the desired temperature. For example, the control unit 50 controls the rotation speed of the fan 21 by PID (Proportional-Integral-Differential) control so that the temperature measured by the thermometer 61 becomes a target temperature. For example, the control unit 50 controls the cooling device 20 so that the temperature of the cooling medium RF1 supplied from the cooling device 20 to the intermediate heat exchanger 40 becomes 45°C.

[0033] Furthermore, the control unit 50 controls the inverter 31 so that the flow rate of the cooling medium RF1 becomes a desired flow rate. By controlling the inverter 31, the rotation speed of the pump 30 is controlled. By controlling the rotation speed of the pump 30, the flow rate of the cooling medium RF1 discharged from the pump 30 is controlled.

[0034] The control unit 50 periodically or at any time performs a refresh operation on the fuel cell 10. The refresh operation on the fuel cell 10 is an operation that performs a process to moisten dry areas that occur on the cell surfaces in the fuel cell module as a result of continuous operation and that can cause a deterioration in the cell characteristics.

[0035] First, the control unit 50 controls the fuel cell 10 to operate temporarily under high load. By operating the fuel cell 10 under high load, the amount of moisture within the cell surface of the fuel cell module is increased by the generated water.

[0036] Next, the control unit 50 controls the fuel cell 10 to temporarily stop output. In other words, the control unit 50 controls the fuel cell 10 to temporarily set the output to 0 kilowatts (idling state). Here, the control unit 50 may set the output to a low load of 0 to 20% of the rated output. By stopping the output or setting the load to a low level, the fuel cell 10 homogenizes the generated water within the module surface.

[0037] Next, the control unit 50 controls the fuel cell 10 to operate temporarily under high load. By operating the fuel cell 10 temporarily under high load, the amount of water in the cell surface within the module increases.

[0038] During refresh operation, output fluctuations may be compensated for using, for example, an auxiliary power supply such as the power storage unit 80. By compensating for output fluctuations using an auxiliary power supply such as the power storage unit 80, the fuel cell system 1 can maintain a constant output.

[0039] As described above, the output of the fuel cell system 1 fluctuates greatly during refresh operation. When changing the output to perform refresh operation, the control unit 50 performs feedforward control of the cooling capacity of the cooling device 20. Figures 2 and 3 are diagrams illustrating the operation of the fuel cell system 1, which is an example of a fuel cell system according to the first embodiment. Figure 3 is an enlarged diagram to show details. In each of Figures 2 and 3, the horizontal axis represents time and the vertical axis represents output. Line Lout represents the output of the fuel cell 10, and line Lrf1 represents the cooling capacity of the cooling device 20.

[0040] The cooling capacity of the cooling device 20 is, for example, the temperature or flow rate of the cooling medium RF1 supplied from the cooling device 20. The lower the temperature of the cooling medium RF1 supplied from the cooling device 20, the higher the cooling capacity of the cooling device 20. Also, the higher the flow rate of the cooling medium RF1 supplied from the cooling device 20, the higher the cooling capacity of the cooling device 20.

[0041] When the control unit 50 increases the output of the fuel cell 10 as indicated by line Lout, it first changes the cooling capacity of the cooling device 20 as indicated by line Lrf1. As shown in Fig. 3, for example, when increasing the output of the fuel cell 10 at time t1, the control unit 50 increases the cooling capacity of the cooling device 20 at time t1p, which is a time T1 before time t1. Time T1 is, for example, between 5 and 60 seconds, preferably 20 seconds.

[0042] When the output of the fuel cell 10 is reduced as indicated by line Lout, the control unit 50 changes the cooling capacity of the cooling device 20 first, as indicated by line Lrf1. As shown in FIG. 3, for example, when the output of the fuel cell 10 is reduced at time t2, the cooling capacity of the cooling device 20 is reduced at time t2p, which is a time T2 before time t2. Time T2 is, for example, between 0 and 60 seconds. Alternatively, the control unit 50 may change the cooling capacity of the cooling device 20 later, when the output of the fuel cell 10 is reduced as indicated by line Lout. For example, the control unit 50 may reduce the cooling capacity of the cooling device 20 between 0 and 60 seconds. For example, as shown in FIG. 2, the cooling capacity of the cooling device 20 may be changed simultaneously with the output of the fuel cell 10 being reduced.

[0043] The control unit 50 controls the cooling capacity of the cooling device 20 so that the temperature measured by the thermometer 62, i.e., the temperature of the cooling medium RF1 discharged from the intermediate heat exchanger 40, is maintained at or above a target temperature. Fig. 4 is a diagram illustrating the operation of the fuel cell system 1, which is an example of the fuel cell system according to the first embodiment.

[0044] 4, the horizontal axis represents time, the vertical axis of the upper graph represents the cooling capacity of the cooling device 20, and the vertical axis of the lower graph represents the temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the exhaust heat utilization equipment 70. The cooling capacity in the upper graph of FIG. 4 represents, for example, the temperature of the cooling medium RF1 supplied from the cooling device 20.

[0045] 4, when the temperature of the cooling medium RF1 is lowered, the temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the exhaust heat utilization device 70 also decreases. When the cooling device 20 is controlled with an emphasis on the temperature of the cooling medium RF1 to be supplied, the temperature in the exhaust heat utilization device 70 decreases. When the temperature of the cooling medium RF1 in the exhaust heat utilization device 70 decreases, the exhaust heat of the fuel cell 10 cannot be effectively utilized in the exhaust heat utilization device 70.

[0046] Therefore, when the temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the exhaust heat utilization equipment 70 becomes equal to or lower than the threshold value Tth, the control unit 50 controls the cooling capacity so that the temperature of the cooling medium RF1 increases. In Fig. 4, the temperature of the cooling medium RF1 supplied from the cooling device 20 is increased. By increasing the temperature of the cooling medium RF1 supplied from the cooling device 20, it is possible to prevent the temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the exhaust heat utilization equipment 70 from becoming lower than a desired temperature.

[0047] Although the temperature of the cooling medium RF1 is used as the cooling capacity in FIG. 4, the flow rate of the cooling medium RF1 may be used as the cooling capacity.

[0048] According to the fuel cell system of the first embodiment, the fuel cell can be cooled while effectively utilizing the exhaust heat after cooling the fuel cell.

[0049] Japan has also announced a goal of becoming carbon neutral by 2050. Carbon pricing and carbon taxes are being considered in various countries, and the need for technologies to reduce carbon dioxide emissions is increasing. Hydrogen fuel cells (hydrogen FCs) are attracting attention as a power generation method that does not emit carbon dioxide.

[0050] Compared to fuel cells for automobiles, stationary fuel cells are required to have a long-term durability of around 10 years (approximately 90,000 hours). To make stationary fuel cells more durable, they undergo refresh operation to prevent the cells from drying out and impurities from adhering to the catalyst.

[0051] During refresh operation, load changes and start-stops are required, so cooling control tailored to the load is necessary. On the other hand, from the perspective of energy conservation and decarbonization, it is required to cool the heat generated by the fuel cell, recover the exhaust heat, and use the exhaust heat. In particular, there is a need for higher output in stationary fuel cells, and multiple fuel cells are sometimes used in parallel. When operating multiple fuel cells in parallel, cooling control and exhaust heat recovery during refresh operation become issues.

[0052] The fuel cell system according to the first embodiment controls the cooling medium while taking into consideration the utilization of exhaust heat in the exhaust heat utilization equipment, and therefore can cool the fuel cell while effectively utilizing the exhaust heat after cooling the fuel cell.

[0053] Second Embodiment A fuel cell system according to a second embodiment will now be described. The fuel cell system according to the second embodiment includes a plurality of fuel cells in the fuel cell system according to the first embodiment. In other words, the fuel cell system according to the second embodiment includes a plurality of fuel cells.

[0054] FIG. 5 is a diagram showing an outline of the configuration of a fuel cell system 2, which is an example of a fuel cell system according to the second embodiment.

[0055] The fuel cell system 2 includes a plurality of fuel cells, a cooling device 20, a pump 30, a plurality of intermediate heat exchangers, a control unit 150, and a waste heat utilization device 70. Specifically, the fuel cell system 2 includes a fuel cell 110A, a fuel cell 110B, a fuel cell 110C, and a fuel cell 110D. Note that in the fuel cell system according to the second embodiment, the number of fuel cells is not limited to that in the example of the fuel cell system 2, and may be two or more. The fuel cell system 2 also includes an intermediate heat exchanger 140A, an intermediate heat exchanger 140B, an intermediate heat exchanger 140C, and an intermediate heat exchanger 140D corresponding to the fuel cell 110A, the fuel cell 110B, the fuel cell 110C, and the fuel cell 110D, respectively.

[0056] In the fuel cell system 2, for the same configuration as that of the fuel cell system 1, the description of the fuel cell system 1 should be referred to, and detailed description thereof will be omitted here.

[0057] [Fuel Cell 110A, Fuel Cell 110B, Fuel Cell 110C, and Fuel Cell 110D] Fuel cells 110A, 110B, 110C, and 110D each have a configuration similar to that of fuel cell 10. Fuel cells 110A, 110B, 110C, and 110D output DC power as outputs PdcA, PdcB, PdcC, and PdcD, respectively. Furthermore, fuel cells 110A, 110B, 110C, and 110D are cooled by cooling media RF2A, RF2B, RF2C, and RF2D, respectively. Cooling media RF2A, RF2B, RF2C, and RF2D are circulated by pumps 111A, 111B, 111C, and 111D, respectively.

[0058] [Intermediate heat exchanger 140A, intermediate heat exchanger 140B, intermediate heat exchanger 140C, and intermediate heat exchanger 140D] The intermediate heat exchanger 140A, the intermediate heat exchanger 140B, the intermediate heat exchanger 140C, and the intermediate heat exchanger 140D are each supplied with a branched cooling medium RF1 supplied from the cooling device 20. The intermediate heat exchanger 140A, the intermediate heat exchanger 140B, the intermediate heat exchanger 140C, and the intermediate heat exchanger 140D exchange heat between the cooling medium RF2A, the cooling medium RF2B, the cooling medium RF2C, and the cooling medium RF2D, respectively.

[0059] [Control unit 150] In addition to the processing of the control unit 50, the control unit 150 also performs processing for controlling a plurality of fuel cells.

[0060] The control unit 150 controls each of the fuel cell 110A, the fuel cell 110B, the fuel cell 110C, and the fuel cell 110D. When the control unit 150 causes each of the fuel cell 110A, the fuel cell 110B, the fuel cell 110C, and the fuel cell 110D to undergo refresh operation, the control unit 150 controls the fuel cell 110A, the fuel cell 110B, the fuel cell 110C, and the fuel cell 110D to undergo refresh operation in sequence.

[0061] Fig. 6 is a diagram illustrating the operation of fuel cell system 2, which is an example of a fuel cell system according to the second embodiment. Fig. 6 shows, from top to bottom, the outputs of fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D. The horizontal axis of each graph in Fig. 6 represents time, and the vertical axis represents the output of each fuel cell.

[0062] 6, the control unit 150 performs refresh operation on the fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D in turn. The fuel cell 110A performs refresh operation at the time indicated by the arrow RFSA. Similarly, the fuel cell 110B, fuel cell 110C, and fuel cell 110D perform refresh operation at the times indicated by the arrows RFSB, RFSC, and RFSD, respectively.

[0063] The order of refresh operations in the fuel cell system 2 shown in FIG. 6 is an example, and the order of refresh operations may be determined as appropriate.

[0064] Fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D each complement output fluctuations when the other fuel cells are undergoing refresh operation. Fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D may complement each other's output fluctuations during refresh operation, thereby maintaining a constant output for fuel cell system 2. Note that fuel cell system 2 may be configured such that, even when fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D complement each other's output fluctuations during refresh operation, the fluctuations in the components that fluctuate may be absorbed by power storage unit 180.

[0065] According to the fuel cell system of the second embodiment, it is possible to cool each of the plurality of fuel cells and effectively utilize the exhaust heat after cooling the fuel cells.

[0066] Third Embodiment The following describes a fuel cell system according to the third embodiment. The fuel cell system according to the third embodiment is the fuel cell system according to the second embodiment, which includes pumps whose rotation speeds can be changed corresponding to each of the multiple fuel cells.

[0067] FIG. 7 is a diagram showing an outline of the configuration of a fuel cell system 3, which is an example of a fuel cell system according to the third embodiment.

[0068] The fuel cell system 3 includes a plurality of fuel cells, a cooling device 20, a plurality of pumps, a plurality of intermediate heat exchangers, a control unit 250, and a waste heat utilization device 70. Specifically, the fuel cell system 3 includes pumps 230A, 230B, 230C, and 230D instead of the pump 30 in the fuel cell system 1 or 2.

[0069] In the fuel cell system 3, for the configurations that are the same as those of either the fuel cell system 1 or the fuel cell system 2, the description of either the fuel cell system 1 or the fuel cell system 2 can be referred to, and detailed description thereof will be omitted here.

[0070] [Pump 230A, Pump 230B, Pump 230C, and Pump 230D] The pumps 230A, 230B, 230C, and 230D send the cooling medium RF1 supplied from the cooling device 20 to the intermediate heat exchanger 140A, 140B, 140C, and 140D, respectively. The rotation speeds of the pumps 230A, 230B, 230C, and 230D are controlled by the inverters 231A, 231B, 231C, and 231D, respectively.

[0071] [Control unit 250] The control unit 250 performs the processes of the control units 50 and 150, as well as the processes of controlling the pumps 230A, 230B, 230C, and 230D.

[0072] The fuel cell system according to the third embodiment can effectively utilize the exhaust heat generated after cooling the fuel cells while cooling each of the fuel cells. Furthermore, the fuel cell system according to the third embodiment can change the cooling capacity of each of the fuel cells.

[0073] Each of pump 230A, pump 230B, pump 230C, and pump 230D is an example of an adjusting unit.

[0074] Fourth Embodiment A fuel cell system according to the fourth embodiment will be described. The fuel cell system according to the fourth embodiment is the fuel cell system according to the second embodiment, which is provided with regulator valves that can change the flow rate corresponding to each of the multiple fuel cells.

[0075] FIG. 8 is a diagram showing an outline of the configuration of a fuel cell system 4, which is an example of a fuel cell system according to the fourth embodiment.

[0076] The fuel cell system 4 includes a plurality of fuel cells, a cooling device 20, a pump 30, a plurality of intermediate heat exchangers, a plurality of regulating valves, a control unit 350, and a waste heat utilization device 70. Specifically, the fuel cell system 4 includes a regulating valve 332A, a regulating valve 332B, a regulating valve 332C, and a regulating valve 332D.

[0077] In the fuel cell system 4, for the configurations that are the same as those of any of the fuel cell systems 1 to 3, the description of any of the fuel cell systems 1 to 3 can be referred to, and detailed description thereof will be omitted here.

[0078] [Control valve 332A, control valve 332B, control valve 332C, and control valve 332D] The adjustment valve 332A, the adjustment valve 332B, the adjustment valve 332C, and the adjustment valve 332D adjust the flow rate of the cooling medium RF1 supplied from the cooling device 20, respectively.

[0079] [Control unit 350] The control unit 350 performs the processes of the control units 50 and 150, as well as the processes of controlling the regulator valves 332A, 332B, 332C, and 332D.

[0080] The fuel cell system according to the fourth embodiment can effectively utilize the exhaust heat generated after cooling each of the fuel cells while cooling each of the fuel cells. Furthermore, the fuel cell system according to the fourth embodiment can change the cooling capacity of each of the fuel cells.

[0081] Each of the adjustment valve 332A, the adjustment valve 332B, the adjustment valve 332C, and the adjustment valve 332D is an example of an adjustment unit.

[0082] Fifth Embodiment A fuel cell system according to a fifth embodiment will be described. The fuel cell system according to the fifth embodiment includes a polymer electrolyte fuel cell that generates electricity by chemically reacting hydrogen and oxygen and is cooled by a first cooling medium, and a cooling device that supplies a second cooling medium that cools the first cooling medium. The fuel cell system according to the fifth embodiment also includes a fuel cell stack that is cooled by the first cooling medium, and an auxiliary device that is cooled by a third cooling medium and operates the fuel cell stack. The fuel cell system according to the fifth embodiment also includes a first intermediate heat exchanger that exchanges heat between the first cooling medium and the second cooling medium, a second intermediate heat exchanger that exchanges heat between the third cooling medium and the second cooling medium, and a controller that controls the fuel cell and the cooling device. The controller in the fuel cell system according to the fifth embodiment controls the cooling capacity of the cooling device when performing a refresh operation of the fuel cell so that the temperature of the second cooling medium discharged from the intermediate heat exchanger is maintained at or above a target temperature.

[0083] FIG. 9 is a diagram showing an outline of the configuration of a fuel cell system 5, which is an example of a fuel cell system according to a fifth embodiment.

[0084] The fuel cell system 5 is a fuel cell that uses fuel cells. The fuel cell system 5 is a chemical battery that converts chemical energy into electricity by reacting hydrogen with oxygen in the air as fuel. The fuel cell system 5 outputs an output Pdc, which is DC power, to an external load or the like.

[0085] The fuel cell system 5 includes a fuel cell 410, a cooling device 20, a pump 30, an intermediate heat exchanger 440 and an intermediate heat exchanger 441, a control unit 450, and a waste heat utilization device .

[0086] In the fuel cell system 5, for the same configuration as that of the fuel cell system 1, the description of the fuel cell system 1 should be referred to, and detailed description thereof will be omitted here.

[0087] [Fuel cell 410] The fuel cell 410 generates electricity by chemically reacting hydrogen and oxygen. That is, the fuel cell 410 generates electricity by chemically reacting supplied hydrogen with oxygen contained in the air.

[0088] The fuel cell 410 includes a fuel cell stack 413 , an air compressor 414 , and a boost converter 415 .

[0089] The fuel cell stack 413 generates electricity by chemically reacting the supplied hydrogen SH with oxygen contained in the air SA. The fuel cell stack 413 is, for example, a polymer electrolyte fuel cell (PEFC). The fuel cell stack 413, which is a polymer electrolyte fuel cell, has a stack structure in which a large number of unit cells (fuel cell cells) are stacked. For details of the unit cells, please refer to the description of the fuel cell system according to the first embodiment, and a detailed description thereof will be omitted here.

[0090] Exhaust gas from the fuel cell stack 413 is discharged from the fuel electrode side of the fuel cell stack 413, with hydrogen consumed in the fuel cell stack 413 removed from the supplied hydrogen SH. Exhaust gas from the air SA is discharged from the air electrode side of the fuel cell stack 413, with oxygen consumed in the fuel cell stack 413 removed from the supplied air SA. The fuel cell stack 413 mixes the exhaust gases discharged from the fuel electrode side and the air electrode side, and discharges the mixture to the outside as exhaust gas EX. When the exhaust gas EX is discharged to the outside, it may be diluted, for example, by ventilation using the fan 21 in the cooling device 20.

[0091] The air compressor 414 compresses the air SA and supplies it to the fuel cell stack 413. The boost converter 415 boosts the voltage of the electricity generated by the fuel cell stack 413. The boost converter 415 is, for example, a DC / DC converter.

[0092] The motor in the air compressor 414 and the circuit elements provided in the boost converter 415 generate heat during operation. Therefore, it is desirable to cool the air compressor 414 and the boost converter 415 during operation. In the fuel cell system 5, the air compressor 414 and the boost converter 415 are cooled by a cooling medium RF3. The cooling medium RF3 is, for example, water or antifreeze.

[0093] The air compressor 414 and the boost converter 415 are each used when generating electricity in the fuel cell stack 413. The air compressor 414 and the boost converter 415 are each an example of an auxiliary device. Note that the auxiliary device is not limited to the air compressor 414 and the boost converter 415, but includes devices used when generating electricity in the fuel cell stack 413.

[0094] [Intermediate heat exchanger 440 and intermediate heat exchanger 441] The intermediate heat exchanger 440 exchanges heat between the cooling medium RF1 supplied from the cooling device 20 and the cooling medium RF2 that cools the fuel cell stack 413 included in the fuel cell 410. The intermediate heat exchanger 440 is provided downstream of the cooling medium RF1 with respect to the intermediate heat exchanger 441. The cooling medium RF2 is circulated between the intermediate heat exchanger 440 and the fuel cell stack 413 by a pump 411.

[0095] The intermediate heat exchanger 441 exchanges heat between the cooling medium RF1 supplied from the cooling device 20 and the cooling medium RF3 that cools the air compressor 414 and the boost converter 415 included in the fuel cell 410. The intermediate heat exchanger 441 is provided upstream of the cooling medium RF1 with respect to the intermediate heat exchanger 440. The cooling medium RF3 is circulated between the intermediate heat exchanger 441 and the air compressor 414 and the boost converter 415 by the pump 412.

[0096] [Control unit 450] In addition to the processing of the control unit 50, the control unit 450 includes processing for controlling the air compressor 414 and the boost converter 415, respectively.

[0097] The fuel cell system according to the fifth embodiment controls the cooling medium while taking into consideration the utilization of exhaust heat in the exhaust heat utilization equipment, and therefore can effectively utilize the exhaust heat after cooling the fuel cell while cooling the fuel cell. Furthermore, the fuel cell system according to the fifth embodiment recovers the exhaust heat emitted from the auxiliary equipment while cooling the auxiliary equipment, thereby enabling more effective utilization of the exhaust heat.

[0098] In the fuel cell system according to the fifth embodiment, the first intermediate heat exchanger and the second intermediate heat exchanger may be connected in parallel to the cooling device.

[0099] Sixth Embodiment A fuel cell system according to a sixth embodiment will now be described. The fuel cell system according to the sixth embodiment is the fuel cell system according to the fifth embodiment, further comprising a first heat exchanger that exchanges heat between the exhaust gas discharged from the fuel cell and a second cooling medium and recovers exhaust heat from the exhaust gas.

[0100] 10 is a diagram showing an outline of the configuration of a fuel cell system 6, which is an example of a fuel cell system according to the sixth embodiment. In the fuel cell system 6, for the same configuration as that of the fuel cell system 5, the description of the fuel cell system 5 should be referred to, and detailed description thereof will be omitted here.

[0101] The fuel cell system 6 further includes a heat exchanger 542 in addition to the fuel cell system 5. The heat exchanger 542 exchanges heat between the exhaust gas EX discharged from the fuel cell 410 and the cooling medium RF1. The heat exchanger 542 is provided upstream of the cooling medium RF1 with respect to the intermediate heat exchanger 441. The heat exchanger 542 recovers heat from the exhaust gas EX.

[0102] The fuel cell system according to the sixth embodiment controls the cooling medium while taking into consideration the utilization of exhaust heat in the exhaust heat utilization equipment, and therefore can effectively utilize the exhaust heat after cooling the fuel cell while cooling the fuel cell. Furthermore, the fuel cell system according to the sixth embodiment recovers the exhaust heat emitted from the auxiliary equipment and exhaust while cooling the auxiliary equipment, thereby enabling more effective utilization of the exhaust heat.

[0103] In the fuel cell system according to the sixth embodiment, the first intermediate heat exchanger, the second intermediate heat exchanger, and the first heat exchanger may be connected in parallel to the cooling device.

[0104] Seventh Embodiment A fuel cell system according to a seventh embodiment will be described. The fuel cell system according to the seventh embodiment is the fuel cell system according to the sixth embodiment, further comprising a second heat exchanger that exchanges heat between the exhaust gas discharged from the fuel cell and a second cooling medium, thereby heating the exhaust gas.

[0105] 11 is a diagram showing an outline of the configuration of a fuel cell system 7, which is an example of a fuel cell system according to the seventh embodiment. For the same configuration of the fuel cell system 7 as that of the fuel cell system 6, the description of the fuel cell system 6 should be referred to, and detailed description thereof will be omitted here.

[0106] The fuel cell system 7 further includes a heat exchanger 643 in addition to the fuel cell system 6. The heat exchanger 643 exchanges heat between the exhaust gas EX discharged from the fuel cell 410 and the cooling medium RF1. The heat exchanger 643 is provided downstream of the cooling medium RF1 with respect to the intermediate heat exchanger 440. The heat exchanger 643 heats the exhaust gas EX. By the heat exchanger 643 heating the exhaust gas EX, it is possible to prevent white smoke from being generated when the exhaust gas EX is discharged to the outside.

[0107] The fuel cell system according to the seventh embodiment controls the cooling medium while taking into consideration the utilization of exhaust heat in the exhaust heat utilization equipment, and therefore can effectively utilize the exhaust heat after cooling the fuel cell while cooling the fuel cell. Furthermore, the fuel cell system according to the seventh embodiment recovers the exhaust heat emitted from the auxiliary equipment and exhaust while cooling the auxiliary equipment, thereby enabling more effective utilization of the exhaust heat. Furthermore, the fuel cell system according to the seventh embodiment can suppress the generation of white smoke when exhausting.

[0108] The fuel cell system according to the seventh embodiment does not necessarily have to include the first heat exchanger that recovers waste heat from the exhaust gas.

[0109] Each of the fuel cell systems according to the fifth to seventh embodiments may be provided with a plurality of fuel cells, as in any of the fuel cell systems according to the second to fourth embodiments.

[0110] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0111] 1, 2, 3, 4, 5, 6, 7 Fuel Cell System 10, 110A, 110B, 110C, 110D, 410 Fuel Cell 11, 111A, 111B, 111C, 111D pumps 20 Cooling device 21 Fan 30, 230A, 230B, 230C, 230D pumps 31, 231A, 231B, 231C, 231D inverter 40, 140A, 140B, 140C, 140D, 440, 441 Intermediate heat exchanger 542, 643 heat exchanger 50, 150, 250, 350, 450 Control unit 61, 62 thermometer 70 Waste heat utilization equipment 80, 180 storage unit 90 Power Conditioner 332A, 332B, 332C, 332D Control Valves RF1, RF2, RF2A, RF2B, RF2C, RF2D, RF3 Cooling medium

Claims

1. a polymer electrolyte fuel cell that generates electricity by chemically reacting hydrogen and oxygen and is cooled by a first cooling medium; a cooling device that supplies a second cooling medium that cools the first cooling medium; a first intermediate heat exchanger that performs heat exchange between the first cooling medium and the second cooling medium; a control unit that controls the fuel cell and the cooling device; Equipped with the control unit controls the cooling capacity of the cooling device so that the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature when performing a refresh operation of the fuel cell; the control unit changes the capacity of the cooling device in advance when increasing the output of the fuel cell, and changes the capacity of the cooling device simultaneously when decreasing the output of the fuel cell; Fuel cell system.

2. the fuel cell includes a fuel cell stack cooled by the first cooling medium, and an auxiliary device cooled by a third cooling medium and used when generating power in the fuel cell stack, a second intermediate heat exchanger that performs heat exchange between the third cooling medium and the second cooling medium, The fuel cell system according to claim 1 .

3. a first heat exchanger that exchanges heat between exhaust gas discharged from the fuel cell and the second cooling medium and recovers heat from the exhaust gas; The fuel cell system according to claim 2 .

4. The exhaust gas turbine engine further includes a second heat exchanger that exchanges heat between the exhaust gas and the second cooling medium and heats the exhaust gas. The fuel cell system according to claim 3 .

5. The cooling system further includes a waste heat utilization device that utilizes waste heat in the second cooling medium discharged from the first intermediate heat exchanger. The fuel cell system according to any one of claims 1 to 4.

6. A plurality of the fuel cells are provided. The fuel cell system according to any one of claims 1 to 4.

7. an adjusting unit provided corresponding to each of the plurality of fuel cells, the adjusting unit adjusting the flow rate of the second cooling medium; The fuel cell system according to claim 6 .

8. The adjusting unit is a pump. The fuel cell system according to claim 7 .

9. The adjusting unit is a adjusting valve. The fuel cell system according to claim 7 .

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