Fuel cell system

Abstract

This disclosure provides a fuel cell system that effectively utilizes the waste heat generated after cooling the fuel cell while simultaneously cooling the fuel cell itself. [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 to cool 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 when the fuel cell is refreshed, the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system.

Background Art

[0002] In Patent Document 1, in order to reduce the possibility that the cooling capacity is insufficient at the start of the time period during which output fluctuation operation is performed, the ability to cool the fuel cell is increased from before the time period during which the fuel cell performs output fluctuation operation. Patent Document 2 discloses that the flow rate of the cooling water for cooling the fuel cell needs to be increased to an amount adapted to the high output state before the fuel cell reaches the high output state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When cooling a fuel cell, waste heat generated upon cooling the fuel cell may be recovered and utilized as heat. However, when the fuel cell is cooled, the temperature of the waste heat may decrease, and it may not be possible to sufficiently recover the heat as a heat source.

[0005] The present disclosure provides a fuel cell system that can effectively utilize waste heat after cooling a fuel cell while cooling the fuel cell.

Means for Solving the Problems

[0006] This 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 to cool 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 when the fuel cell is refreshed, the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above a target temperature. [Effects of the Invention]

[0007] According to the fuel cell system of this disclosure, the fuel cell can be cooled while effectively utilizing the waste heat remaining after cooling the fuel cell. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing a schematic configuration of the fuel cell system according to the first embodiment. [Figure 2] Figure 2 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 3] Figure 3 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 4] Figure 4 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 5] Figure 5 is a diagram showing a schematic configuration of the fuel cell system according to the second embodiment. [Figure 6] Figure 6 is a diagram illustrating the operation of the fuel cell system according to the second embodiment. [Figure 7] Figure 7 is a diagram showing a schematic configuration of the fuel cell system according to the third embodiment. [Figure 8] Figure 8 is a diagram showing a schematic configuration of the fuel cell system according to the fourth embodiment. [Figure 9]Figure 9 is a diagram showing a schematic configuration of the fuel cell system according to the fifth embodiment. [Figure 10] Figure 10 is a diagram showing a schematic configuration of the fuel cell system according to the sixth embodiment. [Figure 11] Figure 11 is a diagram showing a schematic configuration of the fuel cell system according to the seventh embodiment. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the attached drawings. However, this disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims as indicated by the claims.

[0010] In addition, regarding the descriptions and drawings of each embodiment, components having substantially the same or corresponding functional configurations may be denoted by the same reference numerals, thereby omitting redundant explanations. Furthermore, for ease of understanding, the scale of each part in the drawings may differ from that of the actual parts.

[0011] ≪First Embodiment≫ A fuel cell system according to the first embodiment will now be described. The fuel cell system according to the first embodiment comprises 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 to cool the first cooling medium. The fuel cell system according to the first embodiment also comprises 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. When the fuel cell is refreshed, the control unit in the fuel cell system according to the first embodiment 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 above a target temperature.

[0012] Figure 1 is a schematic diagram showing the configuration of a fuel cell system 1, which is an example of a fuel cell system according to the 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 using hydrogen as fuel. The fuel cell system 1 outputs an output Pdc, which is direct current 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 waste heat utilization equipment 70.

[0015] [Fuel cell 10] The fuel cell 10 generates electricity by chemically reacting hydrogen and oxygen. That is, the fuel cell 10 generates electricity by chemically reacting the supplied hydrogen with oxygen contained in the air.

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

[0017] The unit cell in the fuel cell stack, which is a polymer electrolyte fuel cell, includes a membrane - electrode assembly (MEA: Membrane Electrode Assembly) including 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. Also, each of the electrodes is formed of a porous material. Each of the pair of electrodes has, for example, a catalyst layer mainly composed of carbon powder carrying a platinum - based metal catalyst (electrode catalyst) and a gas diffusion layer having both air permeability and electronic conductivity. Further, the single cell has a pair of separators that sandwich the membrane - electrode assembly (MEA) from both sides.

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

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

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

[0021] The power conditioner 90 converts the incoming DC power into AC power (output Pac) and outputs it to an external load, etc.

[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 temperature of the cooling medium RF1 supplied from the cooling device 20 is controlled by controlling the rotational speed of the fan 21.

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

[0024] The cooling medium RF1 is, for example, water. The cooling medium RF1 may also contain, for example, antifreeze in addition to water. The cooling medium RF1 may be, for example, tap water, well water, river water, seawater, etc. The cooling device 20 may also be a cooling device using a refrigeration cycle.

[0025] [Pump 30] Pump 30 flows the cooling medium RF1 supplied from the cooling device 20 to the intermediate heat exchanger 40. Pump 30 is, for example, an axial flow pump. The rotational speed of pump 30 is controlled by an inverter 31. Inverter 31 is, for example, a variable voltage variable frequency (VVVF) inverter. Inverter 31 is not limited to a variable voltage variable frequency inverter; other types may be used. Inverter 31 is controlled by a control unit 50. The control unit 50 controls 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 performs heat exchange 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 the pump 11.

[0027] The cooling medium RF2 used to cool the fuel cell 10 is, for example, water or antifreeze. It is desirable that the cooling medium RF2 is 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 also be equipped with an impurity removal device to remove impurities contained in the cooling medium RF2.

[0028] The temperatures of the cooling mediums RF1 and RF2 in the fuel cell system 1 are described below. 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 in the fuel cell 10. For example, the temperature of the cooling medium RF2 discharged from the fuel cell 10 to the intermediate heat exchanger 40 is 65°C at partial load and 80°C at rated load. The temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the cooling device 20 is, for example, 60°C.

[0029] [Heat Waste Utilization Equipment 70] The waste heat utilization device 70 recovers waste heat from the fuel cell 10. Specifically, the waste heat utilization device 70 recovers heat from the cooling medium RF1 to produce, for example, hot water. The waste heat utilization device 70 includes, for example, a heat exchanger that performs heat exchange between the water to be heated and the cooling medium RF1.

[0030] In the waste heat utilization equipment 70, in order to utilize the waste heat from the fuel cell 10, it is desirable that the temperature of the cooling medium RF1 supplied from the intermediate heat exchanger 40 to the waste heat utilization equipment 70 be 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 obtains temperature from 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 reaches a desired temperature. Specifically, the control unit 50 obtains the temperature of the cooling medium RF1 using a thermometer 61. Then, the control unit 50 controls the rotation speed of the fan 21 of the cooling device 20 so that the temperature of the cooling medium RF1 measured by the thermometer 61 reaches a desired temperature. For example, the control unit 50 controls the rotation speed of the fan 21 using PID (Proportional-Integral-Differential) control so that the temperature measured by the thermometer 61 reaches 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 reaches 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 performs a refresh operation on the fuel cell 10 at regular intervals or at arbitrary times. The refresh operation in the fuel cell 10 is an operation that performs a process to wet dry areas that have formed on the cell surface within the fuel cell module as a result of continuous operation and cause a decrease in battery performance.

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

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

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

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

[0039] As described above, the fuel cell system 1 experiences significant output fluctuations during refresh operation. When the control unit 50 changes the output to perform refresh operation, it performs feedforward control of the cooling capacity of the cooling device 20. Figures 2 and 3 are diagrams illustrating the operation of fuel cell system 1, which is an example of a fuel cell system according to the first embodiment. Figure 3 is an enlarged view for detail. In 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 determined, for example, by 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 shown by line Lout, it changes the cooling capacity of the cooling device 20 in advance as shown by line Lrf1. As shown in Figure 3, for example, when increasing the output of the fuel cell 10 at time t1, it increases the cooling capacity of the cooling device 20 at time t1p, which is time T1 before time t1. Time T1 is, for example, between 5 seconds and 60 seconds, preferably 20 seconds.

[0042] When the control unit 50 reduces the output of the fuel cell 10 as shown by line Lout, it changes the cooling capacity of the cooling device 20 in advance as shown by line Lrf1. As shown in Figure 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 time T2 before time t2. Time T2 is, for example, between 0 and 60 seconds. Alternatively, when the output of the fuel cell 10 is reduced as shown by line Lout, the control unit 50 may change the cooling capacity of the cooling device 20 afterward. For example, the control unit 50 may reduce the cooling capacity of the cooling device 20 between 0 and 60 seconds later. For example, as shown in Figure 2, the cooling capacity of the cooling device 20 may be changed simultaneously when the output of the fuel cell 10 is reduced.

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

[0044] For example, in Figure 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 that returns from the intermediate heat exchanger 40 to the waste heat utilization equipment 70. The cooling capacity in the upper graph of Figure 4 is, for example, the temperature of the cooling medium RF1 supplied from the cooling device 20.

[0045] As shown in Figure 4, lowering the temperature of the cooling medium RF1 lowers the temperature of the cooling medium RF1 that returns from the intermediate heat exchanger 40 to the waste heat utilization equipment 70. If the cooling device 20 focuses on controlling the temperature of the supplied cooling medium RF1, the temperature in the waste heat utilization equipment 70 decreases. When the temperature of the cooling medium RF1 decreases in the waste heat utilization equipment 70, the waste heat from the fuel cell 10 cannot be effectively utilized in the waste heat utilization equipment 70.

[0046] Therefore, when the temperature of the cooling medium RF1 returning from the intermediate heat exchanger 40 to the waste heat utilization equipment 70 falls below the threshold Tth, the control unit 50 controls the cooling capacity so that the temperature of the cooling medium RF1 increases. In Figure 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 waste heat utilization equipment 70 from falling below the desired temperature.

[0047] Note that in Figure 4, the temperature of the cooling medium RF1 was used as the cooling capacity, but the flow rate of the cooling medium RF1 may also 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 waste heat after cooling the fuel cell.

[0049] In Japan, a target of achieving carbon neutrality by 2050 has been announced. Carbon pricing and carbon taxes are being considered in various countries, and the need for carbon dioxide emission reduction technologies is increasing. Hydrogen fuel cells (Hydrogen FCs) are attracting attention as a power generation method that does not emit carbon dioxide.

[0050] Stationary fuel cells require a much longer lifespan, typically around 10 years (approximately 90,000 hours), compared to on-board fuel cells. To enhance the durability of stationary fuel cells, refresh operations are performed to prevent cell drying and the accumulation of impurities on the catalyst.

[0051] Refresh operation involves load changes and startup / shutdown cycles, requiring cooling control tailored to the load. Meanwhile, recovering and utilizing the heat generated by fuel cells through cooling is required from an energy-saving and decarbonization perspective. In particular, stationary fuel cells have a need for higher output, sometimes requiring the use of multiple fuel cells in parallel. When operating multiple fuel cells in parallel, cooling control and heat recovery during refresh operation become challenges.

[0052] The fuel cell system according to the first embodiment controls the cooling medium while considering the use of waste heat in waste heat utilization equipment, thereby enabling effective utilization of waste heat after cooling the fuel cell while simultaneously cooling the fuel cell.

[0053] ≪Second Embodiment≫ A fuel cell system according to the 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] Figure 5 is a schematic diagram showing 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 comprises 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 comprises fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D. In the fuel cell system according to the second embodiment, the number of fuel cells is not limited to the example of fuel cell system 2, and may be two or more. Furthermore, the fuel cell system 2 comprises intermediate heat exchangers 140A, 140B, 140C, and 140D corresponding to fuel cell 110A, 110B, 110C, and 110D, respectively.

[0056] For fuel cell system 2, the same configuration as fuel cell system 1 is as described in the description of fuel cell system 1, and a detailed explanation is omitted here.

[0057] [Fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D] Each of the fuel cells 110A, 110B, 110C, and 110D has the same configuration as fuel cell 10. Fuel cells 110A, 110B, 110C, and 110D output DC power outputs PdcA, PdcB, PdcC, and PdcD, respectively. 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] Each of the intermediate heat exchangers 140A, 140B, 140C, and 140D is supplied with a branch of the cooling medium RF1 supplied from the cooling device 20. Each of the intermediate heat exchangers 140A, 140B, 140C, and 140D exchanges heat between the cooling medium RF1 and the cooling medium RF2A, RF2B, RF2C, and RF2D, respectively.

[0059] [Control Unit 150] In addition to the processing performed by the control unit 50, the control unit 150 includes processing to control multiple fuel cells.

[0060] The control unit 150 controls each of the fuel cells 110A, 110B, 110C, and 110D. When refreshing each of the fuel cells 110A, 110B, 110C, and 110D, the control unit 150 controls them to perform the refresh operation sequentially.

[0061] Figure 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. Figure 6 shows the outputs of fuel cell 110A, fuel cell 110B, fuel cell 110C, and fuel cell 110D, from top to bottom. In the graphs of Figure 6, the horizontal axis represents time, and the vertical axis represents the output of each fuel cell.

[0062] As shown in Figure 6, the control unit 150 sequentially performs refresh operations on each of the fuel cells 110A, 110B, 110C, and 110D. Fuel cell 110A undergoes a refresh operation at the time indicated by arrow RFSA. Similarly, fuel cells 110B, 110C, and 110D undergo refresh operations at the times indicated by arrows RFSB, RFSC, and RFSD, respectively.

[0063] The refresh operation sequence in the fuel cell system 2 shown in Figure 6 is an example, and the refresh operation sequence may be determined as appropriate.

[0064] Each of the fuel cells 110A, 110B, 110C, and 110D complements the output fluctuations when the other fuel cells are performing refresh operation. The fuel cells 110A, 110B, 110C, and 110D may complement each other's output fluctuations during refresh operation to maintain a constant output for the fuel cell system 2. In addition, the fuel cell system 2 may absorb any remaining fluctuations even when the fuel cells 110A, 110B, 110C, and 110D complement each other's output fluctuations during refresh operation using the energy storage unit 180.

[0065] According to the fuel cell system of the second embodiment, it is possible to effectively utilize the waste heat after cooling the fuel cells while cooling each of the multiple fuel cells.

[0066] ≪Third Embodiment≫ A fuel cell system according to the third embodiment will now be described. The fuel cell system according to the third embodiment is a fuel cell system according to the second embodiment, further comprising a pump whose rotational speed can be changed in accordance with each of the multiple fuel cells.

[0067] Figure 7 is a schematic diagram showing 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 comprises multiple fuel cells, a cooling device 20, multiple pumps, multiple intermediate heat exchangers, a control unit 250, and a waste heat utilization device 70. Specifically, the fuel cell system 3 replaces the pump 30 in the fuel cell system 1 or fuel cell system 2 with pumps 230A, 230B, 230C, and 230D.

[0069] For configurations in fuel cell system 3 that are the same as those in fuel cell system 1 and fuel cell system 2, please refer to the description of either fuel cell system 1 or fuel cell system 2, and a detailed explanation will be omitted here.

[0070] [Pumps 230A, 230B, 230C, and 230D] Pumps 230A, 230B, 230C, and 230D send the cooling medium RF1 supplied from the cooling device 20 to intermediate heat exchangers 140A, 140B, 140C, and 140D, respectively. The rotational speed of pumps 230A, 230B, 230C, and 230D is controlled by inverters 231A, 231B, 231C, and 231D, respectively.

[0071] [Control Unit 250] In addition to the processing performed by the control units 50 and 150, the control unit 250 performs processing to control each of the pumps 230A, 230B, 230C, and 230D.

[0072] According to the fuel cell system of the third embodiment, it is possible to effectively utilize the waste heat after cooling the fuel cells while cooling each of the multiple fuel cells. Furthermore, according to the fuel cell system of the third embodiment, the cooling capacity of each of the multiple fuel cells can be changed.

[0073] Pumps 230A, 230B, 230C, and 230D are examples of adjustment units.

[0074] ≪Fourth Embodiment≫ A fuel cell system according to the fourth embodiment will now be described. The fuel cell system according to the fourth embodiment is a fuel cell system according to the second embodiment, further comprising a control valve capable of changing the flow rate corresponding to each of the multiple fuel cells.

[0075] Figure 8 is a schematic diagram showing 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 comprises multiple fuel cells, a cooling device 20, a pump 30, multiple intermediate heat exchangers, multiple control valves, a control unit 350, and a waste heat utilization device 70. Specifically, the fuel cell system 4 includes control valves 332A, 332B, 332C, and 332D.

[0077] For fuel cell system 4, if the configuration is the same as any of fuel cell systems 1 to 3, please refer to the description of any of fuel cell systems 1 to 3, and a detailed explanation will be omitted here.

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

[0079] [Control Unit 350] In addition to the processing performed by the control units 50 and 150, the control unit 350 performs processing to control each of the control valves 332A, 332B, 332C, and 332D.

[0080] According to the fuel cell system of the fourth embodiment, it is possible to effectively utilize the waste heat after cooling the fuel cells while cooling each of the multiple fuel cells. Furthermore, according to the fuel cell system of the fourth embodiment, the cooling capacity of each of the multiple fuel cells can be changed.

[0081] Control valves 332A, 332B, 332C, and 332D are examples of control units.

[0082] ≪Fifth Embodiment≫ A fuel cell system according to the fifth embodiment will now be described. The fuel cell system according to the fifth embodiment comprises 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 to cool the first cooling medium. The fuel cell system according to the fifth embodiment also comprises a fuel cell stack cooled by the first cooling medium and auxiliary equipment cooled by a third cooling medium for operating the fuel cell stack. Furthermore, the fuel cell system according to the fifth embodiment comprises a first intermediate heat exchanger that performs heat exchange between the first cooling medium and the second cooling medium, a second intermediate heat exchanger that performs heat exchange between the third cooling medium and the second cooling medium, and a control unit that controls the fuel cell and the cooling device. When the fuel cell is refreshed, the control unit controls the cooling capacity of the cooling device so that the temperature of the second cooling medium discharged from the intermediate heat exchanger is maintained above a target temperature.

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

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

[0085] The fuel cell system 5 comprises a fuel cell 410, a cooling device 20, a pump 30, intermediate heat exchangers 440 and 441, a control unit 450, and a waste heat utilization device 70.

[0086] For fuel cell system 5, the same configuration as fuel cell system 1 is as described in the description of fuel cell system 1, and a detailed explanation is omitted here.

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

[0088] The fuel cell 410 comprises 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 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, being a polymer electrolyte fuel cell, has a stack structure in which a large number of unit cells (fuel cell cells) are stacked. Details of the unit cells are omitted here, as they should be referred to in the description of the fuel cell system according to the first embodiment.

[0090] From the fuel electrode side of the fuel cell stack 413, exhaust gas is discharged from the supplied hydrogen SH, with the hydrogen consumed in the fuel cell stack 413 removed. Similarly, from the air electrode side of the fuel cell stack 413, exhaust gas is discharged from the supplied air SA, with the oxygen consumed in the fuel cell stack 413 removed. The fuel cell stack 413 mixes the exhaust gases discharged from both the fuel electrode side and the air electrode side and exhausts them to the outside as exhaust gas EX. When exhausting exhaust gas EX to the outside, it may be diluted, for example, by ventilation by 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 of the boost converter 415 generate heat during operation. Therefore, it is desirable that both the air compressor 414 and the boost converter 415 be cooled 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 used in the fuel cell stack 413 when generating electricity. The air compressor 414 and the boost converter 415 are examples of auxiliary equipment. Note that auxiliary equipment is not limited to the air compressor 414 and the boost converter 415, but includes any equipment used in the fuel cell stack 413 when generating electricity.

[0094] [Intermediate heat exchanger 440 and intermediate heat exchanger 441] The intermediate heat exchanger 440 performs heat exchange between the cooling medium RF1 supplied from the cooling device 20 and the cooling medium RF2 that cools the fuel cell stack 413 of the fuel cell 410. The intermediate heat exchanger 440 is located downstream of the cooling medium RF1 relative 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 the pump 411.

[0095] The intermediate heat exchanger 441 performs heat exchange 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 of the fuel cell 410, respectively. The intermediate heat exchanger 441 is located upstream of the cooling medium RF1 relative to the intermediate heat exchanger 440. The cooling medium RF3 is circulated between the intermediate heat exchanger 441 and the air compressor 414 and boost converter 415 by the pump 412.

[0096] [Control Unit 450] In addition to the processing performed by the control unit 50, the control unit 450 includes processing to control 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 considering the utilization of waste heat in waste heat utilization equipment, thereby effectively utilizing the waste heat after cooling the fuel cell while cooling the fuel cell. Furthermore, according to the fuel cell system according to the fifth embodiment, waste heat can be recovered from auxiliary equipment while cooling the auxiliary equipment, thereby utilizing the waste heat more effectively.

[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 the sixth embodiment will now be described. The fuel cell system according to the sixth embodiment further comprises a first heat exchanger that performs heat exchange between exhaust gas discharged from the fuel cell and a second cooling medium, and recovers waste heat from the exhaust gas, in addition to the fuel cell system according to the fifth embodiment.

[0100] Figure 10 is a schematic diagram of the configuration of a fuel cell system 6, which is an example of a fuel cell system according to the sixth embodiment. For configurations in fuel cell system 6 that are the same as those in fuel cell system 5, please refer to the description of fuel cell system 5, and a detailed explanation 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 performs heat exchange between the exhaust gas EX discharged from the fuel cell 410 and the cooling medium RF1. The heat exchanger 542 is located upstream of the cooling medium RF1 relative 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 considering the utilization of waste heat in waste heat utilization equipment, thereby effectively utilizing the waste heat after cooling the fuel cell while cooling the fuel cell. Furthermore, according to the fuel cell system according to the sixth embodiment, waste heat discharged from auxiliary equipment and exhaust can be recovered while cooling the auxiliary equipment, thereby enabling more effective utilization of waste 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 the seventh embodiment will now be described. The fuel cell system according to the seventh embodiment further comprises a second heat exchanger that performs heat exchange between the exhaust gas discharged from the fuel cell and a second cooling medium, thereby heating the exhaust gas, in addition to the fuel cell system according to the sixth embodiment.

[0105] Figure 11 is a schematic diagram of the configuration of a fuel cell system 7, which is an example of a fuel cell system according to the seventh embodiment. For configurations in fuel cell system 7 that are the same as those in fuel cell system 6, please refer to the description of fuel cell system 6, and a detailed explanation 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 performs heat exchange between the exhaust gas EX discharged from the fuel cell 410 and the cooling medium RF1. The heat exchanger 643 is located downstream of the cooling medium RF1 relative to the intermediate heat exchanger 440. The heat exchanger 643 heats the exhaust gas EX. By heating the exhaust gas EX with the heat exchanger 643, the generation of white smoke when the exhaust gas EX is discharged to the outside can be suppressed.

[0107] The fuel cell system according to the seventh embodiment controls the cooling medium while considering the utilization of waste heat in waste heat utilization equipment, thereby effectively utilizing the waste heat after cooling the fuel cell while cooling the fuel cell. Furthermore, according to the fuel cell system according to the seventh embodiment, waste heat discharged from auxiliary equipment and exhaust can be recovered while cooling the auxiliary equipment, thereby making more effective use of waste heat. Moreover, according to the fuel cell system according to the seventh embodiment, the generation of white smoke during exhaust can be suppressed.

[0108] In the fuel cell system according to the seventh embodiment, a first heat exchanger for recovering exhaust heat from the exhaust is not required.

[0109] Each of the fuel cell systems according to the fifth to seventh embodiments may be equipped with multiple 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 in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, 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 systems 10, 110A, 110B, 110C, 110D, 410 Fuel Cell 11, 111A, 111B, 111C, 111D pumps 20 Cooling device 21 Fans 30, 230A, 230B, 230C, 230D pumps 31, 231A, 231B, 231C, 231D Inverters 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. Heat Utilization Equipment 80, 180 energy storage units 90 Power Conditioner 332A, 332B, 332C, 332D Control valves RF1, RF2, RF2A, RF2B, RF2C, RF2D, RF3 Cooling medium

Claims

1. A solid polymer fuel cell 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 to cool the first cooling medium, A first intermediate heat exchanger that performs heat exchange between the first cooling medium and the second cooling medium, The fuel cell and the control unit that controls the cooling device, Equipped with, The control unit controls the cooling capacity of the cooling device so that when the fuel cell is refreshed, the temperature of the second cooling medium discharged from the first intermediate heat exchanger is maintained at or above the target temperature. Fuel cell system.

2. The fuel cell comprises a fuel cell stack cooled by the first cooling medium and an auxiliary unit cooled by the third cooling medium and used when generating electricity in the fuel cell stack. The system further comprises 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. The system further includes a first heat exchanger that performs heat exchange between the 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 system further includes a second heat exchanger that performs heat exchange between the exhaust gas and the second cooling medium, thereby heating the exhaust gas. The fuel cell system according to claim 3.

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

6. The control unit, when performing a refresh operation of the fuel cell, changes the cooling capacity of the cooling device in advance. A fuel cell system according to any one of claims 1 to 4.

7. A plurality of the aforementioned fuel cells are provided, A fuel cell system according to any one of claims 1 to 4.

8. Each of the multiple fuel cells is provided with an adjustment unit that adjusts the flow rate of the second cooling medium, The fuel cell system according to claim 7.

9. The adjustment unit is a pump. The fuel cell system according to claim 8.

10. The adjustment part is an adjustment valve. The fuel cell system according to claim 8.

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