Fuel cell system

Abstract

To provide a fuel cell system capable of adjusting the temperature of a fuel cell while miniaturizing the entire system.SOLUTION: A fuel cell system 1 according to an aspect of the present disclosure includes: a supply side air valve 63 provided in an air supply passage 51 to adjust an air flow rate; an exhaust side blower 72 provided in an air off-gas exhaust passage 52 to suck air off-gas from an FC stack 11; and a control section 14 to control the supply side air valve 63 and the exhaust side blower 72. When the temperature of the FC stack 11 is higher than a target temperature range TT, the control section 14 performs cooling control to cool the FC stack 11 by adjusting the opening of the supply side air valve 63 to be smaller than the opening when the temperature of the FC stack 11 is within the target temperature range TT at the power generation of the FC stack 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity when supplied with a fuel gas and an oxidant gas. [Background technology]

[0002] Patent document 1 discloses an air-cooled fuel cell in which cooling passages (cooling gas slots) are provided between each cell (each fuel cell unit) of the fuel cell, and the fuel cell is cooled by flowing cooling gas through these cooling passages using a cooling fan. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-32707 A Summary of the Invention [Problem to be solved by the invention]

[0004] The fuel cell disclosed in Patent Document 1 has cooling passages between each cell of the fuel cell, and also has a cooling fan for circulating cooling gas through the cooling passage, so the size of the fuel cell may become large, and the fuel cell system including the fuel cell may become large. In particular, when the output of the fuel cell increases, the amount of heat generated by the fuel cell increases, so it becomes necessary to expand the size of the cooling passages and increase the number of cooling fans, and the size of the fuel cell may become even larger, and the fuel cell system may become even larger. In this way, by providing a structure for adjusting the temperature of the fuel cell, the size of the fuel cell may become large, and the fuel cell system may become large.

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and has an object to provide a fuel cell system that can adjust the temperature of the fuel cell while miniaturizing the entire system. [Means for solving the problem]

[0006] One aspect of the present disclosure made to solve the above-mentioned problems is a fuel cell system comprising: a fuel cell that generates power by receiving a supply of fuel gas and an oxidant gas; a gas supply passage that supplies the oxidant gas to the fuel cell; an off-gas discharge passage through which oxidant off-gas, which is the oxidant gas that has not been used for power generation, is discharged from the fuel cell; a supply-side valve provided in the gas supply passage that adjusts a flow rate of the oxidant gas; a suction unit provided in the off-gas discharge passage that suctions the oxidant off-gas from the fuel cell; and a control unit that controls the supply-side valve and the suction unit, wherein when the temperature of the fuel cell is higher than a predetermined temperature range, the control unit performs cooling control to cool the fuel cell by reducing an opening degree of the supply-side valve compared to an opening degree when the temperature of the fuel cell is within the predetermined temperature range during power generation of the fuel cell.

[0007] According to this aspect, when the temperature of the fuel cell is high, the upstream side of the fuel cell is throttled and the oxidant off-gas is sucked from the fuel cell to the downstream side, so that the pressure in the fuel cell drops. This lowers the boiling point of water in the fuel cell, so that the water in the fuel cell (i.e., the water generated during power generation) vaporizes and generates latent heat of vaporization. In addition, the suction part sucks water, so that a gas flow occurs in the fuel cell. Thus, by effectively utilizing the latent heat of vaporization and the gas flow in this way, the temperature of the fuel cell can be lowered and the fuel cell can be cooled. Furthermore, structures for cooling the fuel cell (for example, a cooling system including a passage through which cooling water flows and a cooling fan) can be eliminated or reduced in size, so that the size of the fuel cell can be reduced and the fuel cell system can be made smaller. Thus, the fuel cell can be cooled and the temperature of the fuel cell can be adjusted while the overall fuel cell system is made smaller.

[0008] Another aspect of the present disclosure made to solve the above problems is a fuel cell system comprising: a fuel cell that generates power by receiving a supply of fuel gas and an oxidant gas; a gas supply passage that supplies the oxidant gas to the fuel cell; an off-gas discharge passage through which oxidant off-gas, which is the oxidant gas that has not been used for power generation, is discharged from the fuel cell; a discharge side valve provided in the off-gas discharge passage that adjusts the flow rate of the oxidant off-gas; a discharge unit provided in the gas supply passage that discharges the oxidant gas to the fuel cell; and a control unit that controls the discharge side valve and the discharge unit, wherein when the temperature of the fuel cell is lower than a predetermined temperature range, the control unit performs warm-up control to warm up the fuel cell by reducing an opening degree of the discharge side valve compared to an opening degree when the temperature of the fuel cell is within the predetermined temperature range during power generation of the fuel cell.

[0009] According to this aspect, when the temperature of the fuel cell is low, the oxidant gas is discharged from the upstream side of the fuel cell to the fuel cell while the downstream side of the fuel cell is throttled, and the pressure inside the fuel cell increases. As a result, the oxidant gas inside the fuel cell is compressed, and the temperature of the fuel cell increases, allowing the fuel cell to be warmed up. In addition, a dedicated structure for warming up the fuel cell (e.g., a heater) is unnecessary or can be made smaller, making it possible to reduce the size of the fuel cell and thus the fuel cell system. Therefore, the fuel cell can be warmed up and the temperature of the fuel cell can be adjusted while the overall fuel cell system is made smaller.

[0010] In the above aspect, when performing the cooling control or the warm-up control, it is preferable that the control unit increases the rotation speed of the suction unit or the discharge unit above the rotation speed when the temperature of the fuel cell is within the specified temperature range during power generation of the fuel cell.

[0011] According to this embodiment, even if the upstream side of the fuel cell is throttled by the supply side valve, the rotation speed of the suction part is increased, so the necessary amount of oxidant gas can be supplied to the fuel cell by negative pressure. Therefore, the fuel cell can be cooled while maintaining the power generation efficiency of the fuel cell. In addition, since the rotation speed of the discharge part is increased while the downstream side of the fuel cell is throttled by the discharge side valve, the pressure inside the fuel cell can be further increased, and the warm-up efficiency can be further improved. Effect of the Invention

[0012] According to the fuel cell system of the present disclosure, it is possible to adjust the temperature of the fuel cell while reducing the size of the entire system. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration of a fuel cell system according to an embodiment of the present invention; [Diagram 2] FIG. 1 is an image diagram showing the effect of cooling an FC stack. [Diagram 3] FIG. 1 is an image diagram showing the operation of an FC stack during warm-up.

[0014] An embodiment of a fuel cell system according to the present disclosure will now be described.

[0015] <Outline of the fuel cell system> First, an overview of a fuel cell system 1 according to the present embodiment will be described. The fuel cell system 1 is a system that is mounted on a fuel cell vehicle and supplies electric power to its drive motor (not shown).

[0016] (General configuration of fuel cell system) 1, the fuel cell system 1 has an FC stack 11, a hydrogen system 12, an air system 13, and a control unit 14. The FC stack 11 is an example of the "fuel cell" of the present disclosure.

[0017] The FC stack 11 generates power by receiving a supply of fuel gas and an oxidant gas. In this embodiment, the fuel gas is hydrogen gas, and the oxidant gas is air. That is, the FC stack 11 generates power by receiving a supply of hydrogen gas from a hydrogen system 12 and a supply of air from an air system 13. The power generated by the FC stack 11 is then supplied to a drive motor (not shown) via an inverter (not shown).

[0018] The hydrogen system 12 is provided on the anode side of the FC stack 11. The hydrogen system 12 includes a hydrogen filling passage 20, a hydrogen gas supply passage 21, a hydrogen off-gas discharge passage 22, and a hydrogen circulation passage .

[0019] The hydrogen filling passage 20 is a passage for filling hydrogen gas into the hydrogen tank 31 from the filling port 30. The hydrogen gas supply passage 21 is a passage for supplying hydrogen gas from the hydrogen tank 31 to the FC stack 11.

[0020] The hydrogen off-gas discharge passage 22 is a passage through which hydrogen off-gas, which is hydrogen gas not used for power generation, is discharged from the FC stack 11. The hydrogen circulation passage 23 is a passage for circulating at least a portion of the hydrogen off-gas from the hydrogen off-gas discharge passage 22 to the hydrogen gas supply passage 21.

[0021] The hydrogen system 12 includes, in the hydrogen gas supply passage 21, a valve 32, a pressure reducing valve 33, an injector 34, and an ejector 35, in that order from the hydrogen tank 31 side.

[0022] The valve 32 switches between supplying and cutting off hydrogen gas from the hydrogen tank 31 to the hydrogen gas supply passage 21, and between supplying and cutting off hydrogen gas from the filling port 30 to the hydrogen tank 31. The pressure reducing valve 33 is a pressure regulating valve for reducing the pressure of hydrogen gas. The injector 34 is a valve for injecting hydrogen gas toward the ejector 35.

[0023] The ejector 35 sucks in the hydrogen off-gas discharged from the FC stack 11 to the hydrogen off-gas discharge passage 22 through the hydrogen circulation passage 23 by using negative pressure generated by the introduction of hydrogen gas injected from the injector 34. The ejector 35 then merges the hydrogen off-gas sucked from the hydrogen off-gas discharge passage 22 with the hydrogen gas introduced from the injector 34, and circulates the combined gas to the FC stack 11.

[0024] Furthermore, the hydrogen system 12 includes a gas-liquid separator 41 and an exhaust drain valve 42 in the hydrogen off-gas discharge passage 22 .

[0025] The gas-liquid separator 41 is a device that separates moisture in the hydrogen off-gas. The gas-liquid separator 41 is connected to the ejector 35 via the hydrogen circulation passage 23. The exhaust drain valve 42 is a valve that controls the discharge of the hydrogen off-gas discharged from the FC stack 11 to the outside, and controls the discharge of moisture separated from the hydrogen off-gas by the gas-liquid separator 41 to a water tank 81. The hydrogen off-gas discharge passage 22 is connected to the water tank 81.

[0026] The air system 13 is provided on the cathode side of the FC stack 11. The air system 13 includes an air supply passage 51 and an air off-gas exhaust passage 52. The air supply passage 51 is an example of the "gas supply passage" in the present disclosure. The air off-gas exhaust passage 52 is an example of the "off-gas exhaust passage" in the present disclosure.

[0027] The air supply passage 51 is a passage for supplying air to the FC stack 11 from outside the fuel cell system 1. The air off-gas discharge passage 52 is a passage for discharging air off-gas, which is air not used for power generation, from the FC stack 11.

[0028] The air system 13 includes, in order from the upstream side, an air cleaner 61, a supply-side blower 62, and a supply-side air valve 63 in the air supply passage 51. The supply-side blower 62 is an example of a "discharge portion" in the present disclosure. The supply-side air valve 63 is an example of a "supply-side valve" in the present disclosure.

[0029] The air cleaner 61 is a device that purifies the air taken in from outside the fuel cell system 1. The supply side blower 62 is a device that discharges and supplies air to the FC stack 11. The supply side air valve 63 is a valve that adjusts the flow rate of air supplied from the air supply passage 51 to the FC stack 11.

[0030] The air system 13 also includes a discharge-side air valve 71 and a discharge-side blower 72 in the air off-gas discharge passage 52. The discharge-side air valve 71 is an example of the "discharge-side valve" in the present disclosure. The discharge-side blower 72 is an example of the "suction unit" in the present disclosure.

[0031] The discharge-side air valve 71 is a valve that adjusts the flow rate of air off-gas discharged from the FC stack 11 to the air off-gas discharge passage 52. The discharge-side blower 72 is a device that sucks the air off-gas from the FC stack 11. The air off-gas discharge passage 52 is connected to a water tank 81.

[0032] The control unit 14 is a device having, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM for storing control programs and control data processed by the CPU and a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 14 performs various controls of the fuel cell system 1 according to the control programs stored in the storage unit.

[0033] Specifically, the control unit 14 controls, for example, the rotation speed of the supply-side blower 62, the opening degree of the supply-side air valve 63, the opening degree of the discharge-side air valve 71, and the rotation speed of the discharge-side blower 72. The control unit 14 also controls the valve 32, the pressure reducing valve 33, the injector 34, the exhaust drain valve 42, and the like.

[0034] Further, since the fuel cell system 1 of the present embodiment does not have a cooling system for cooling the FC stack 11 (that is, a system including a passage through which cooling water flows, a cooling fan, etc.), the system is downsized.

[0035] (Regarding the operation of the fuel cell system) In the fuel cell system 1 configured as described above, in the hydrogen system 12, the hydrogen gas supplied from the hydrogen gas supply passage 21 to the FC stack 11 is used for power generation in the FC stack 11 and then discharged to the outside as hydrogen off-gas from the FC stack 11 through the hydrogen off-gas discharge passage 22, or is sucked into the ejector 35 through the hydrogen off-gas discharge passage 22 and the hydrogen circulation passage 23. Further, in the air system 13, the air supplied from the air supply passage 51 to the FC stack 11 is used for power generation in the FC stack 11 and then discharged to the outside as air off-gas from the FC stack 11 through the air off-gas discharge passage 52.

[0036] (Regarding the temperature adjustment of the FC stack) In the present embodiment, the temperature of the FC stack 11 is adjusted by controlling the supply-side blower 62, the supply-side air valve 63, the discharge-side air valve 71, and the discharge-side blower 72 of the air system 13 to control the pressure inside the FC stack 11.

[0037] Specifically, when the temperature of the FC stack 11 rises, the pressure inside the FC stack 11 is lowered to promote the vaporization of the water generated inside the FC stack 11, and the latent heat of vaporization generated at this time is utilized to lower the temperature of the FC stack 11. On the other hand, when the temperature of the FC stack 11 drops, the pressure inside the FC stack 11 is increased to compress the air inside the FC stack 11 and raise the temperature of the FC stack 11 while suppressing the vaporization of the water generated inside the FC stack 11.

[0038] (Regarding the cooling of the FC stack) Therefore, first, a description will be given of a method for cooling the FC stack 11. When the temperature of the FC stack 11 is higher than the target temperature range TT during power generation of the FC stack 11, the control unit 14 reduces the opening of the supply-side air valve 63 to a normal opening during power generation of the FC stack 11, that is, smaller than the opening when the temperature of the FC stack 11 is within the target temperature range TT during power generation of the FC stack 11.

[0039] In this way, the control unit 14 narrows the opening of the supply-side air valve 63 to a small degree as cooling control, as shown in Fig. 2. As a result, the discharge-side blower 72 sucks air off-gas from the FC stack 11, cooling the FC stack 11. At this time, the control unit 14 keeps the discharge-side air valve 71 open to a predetermined opening degree.

[0040] Here, the target temperature range TT is a temperature range recommended for efficient power generation in the FC stack 11, and is, for example, a temperature range of 60° C. or more and 80° C. or less. The target temperature range TT is an example of the “predetermined temperature range” in this disclosure.

[0041] In this manner, in this embodiment, when the temperature of the FC stack 11 is high, the upstream side of the FC stack 11 is throttled while air off-gas is sucked from the FC stack 11 to its downstream side, thereby reducing the pressure inside the FC stack 11. This lowers the boiling point of water inside the FC stack 11, causing the water inside the FC stack 11 (i.e., the water produced during power generation) to vaporize. Then, the latent heat of vaporization generated when the water inside the FC stack 11 vaporizes reduces the temperature of the FC stack 11.

[0042] When the pressure inside the FC stack 11 decreases, the pressure inside the FC stack 11 can be reduced to below the normal pressure when the FC stack 11 is generating electricity (i.e., the pressure set when the temperature of the FC stack 11 is within the target temperature range TT), and in some cases, it may be set to negative pressure (pressure lower than atmospheric pressure).

[0043] Furthermore, in this embodiment, the exhaust blower 72 sucks in the air off-gas, which creates an air flow within the FC stack 11, and the temperature of the FC stack 11 decreases.

[0044] As described above, when the temperature of the FC stack 11 is higher than the target temperature range TT, the latent heat of vaporization and gas flow can be effectively utilized to cool the FC stack 11 and adjust the temperature of the FC stack 11 to within the target temperature range TT.

[0045] Furthermore, according to this embodiment, it is possible to eliminate or reduce the size of structures for cooling the FC stack 11 (for example, a cooling system equipped with passages through which cooling water flows, cooling fans, etc.). This allows the size of the FC stack 11 to be reduced, and therefore the fuel cell system 1 to be made smaller.

[0046] As described above, according to this embodiment, the temperature of the FC stack 11 can be adjusted to within the target temperature range TT by cooling the FC stack 11 while reducing the overall size of the fuel cell system 1.

[0047] It should be noted that when the control unit 14 cools the FC stack 11 and adjusts the temperature of the FC stack 11 to within the target temperature range TT, it ends the cooling control and ends the cooling of the FC stack 11.

[0048] Furthermore, the greater the output (i.e., the amount of power generated) of the FC stack 11, the greater the amount of heat generated within the FC stack 11. Therefore, as the output of the FC stack 11 increases, the control unit 14 may reduce the opening of the supply-side air valve 63 or increase the rotation speed of the discharge-side blower 72, thereby further reducing the pressure within the FC stack 11 and lowering the temperature of the FC stack 11.

[0049] In addition, when the control unit 14 performs cooling control in this manner to cool the FC stack 11, it may increase the rotation speed of the discharge side blower 72 above the normal rotation speed when the FC stack 11 is generating electricity, i.e., the rotation speed when the temperature of the FC stack 11 is within the target temperature range TT when the FC stack 11 is generating electricity.

[0050] As a result, even if the supply-side air valve 63 throttles the upstream side of the FC stack 11 when the FC stack 11 is generating electricity, the rotation speed of the discharge-side blower 72 is increased, so that the amount of air required for power generation can be supplied from the air supply passage 51 to the FC stack 11 by negative pressure. In this way, in this embodiment, the FC stack 11 can be cooled while maintaining power generation by the FC stack 11.

[0051] (About warming up the FC stack) Next, we will explain a method of warming up the FC stack 11. When the temperature of the FC stack 11 is lower than the target temperature range TT during power generation of the FC stack 11, the control unit 14 reduces the opening of the discharge side air valve 71 to a smaller value than the normal opening when the FC stack 11 is generating electricity, that is, the opening when the temperature of the FC stack 11 is within the target temperature range TT during power generation of the FC stack 11.

[0052] In this way, the control unit 14 narrows the opening of the discharge-side air valve 71 to a small degree as warm-up control, as shown in Fig. 3. As a result, air is discharged by the supply-side blower 62 to the FC stack 11, warming up the FC stack 11. At this time, the control unit 14 keeps the supply-side air valve 63 open to a predetermined opening degree.

[0053] In this manner, in this embodiment, when the temperature of the FC stack 11 is low, the downstream side of the FC stack 11 is throttled while air is discharged from the upstream side of the FC stack 11 to the FC stack 11, and the pressure inside the FC stack 11 increases. As a result, the air inside the FC stack 11 is compressed, and the temperature of the FC stack 11 increases.

[0054] As described above, when the temperature of the FC stack 11 is lower than the target temperature range TT, the air inside the FC stack 11 is compressed to warm up the FC stack 11 and adjust the temperature of the FC stack 11 to within the target temperature range TT.

[0055] Furthermore, according to this embodiment, it is possible to eliminate or reduce the size of structures (such as a heater) for warming up the FC stack 11. As a result, the size of the FC stack 11 can be reduced, and the fuel cell system 1 can be made smaller.

[0056] As described above, according to this embodiment, the entire fuel cell system 1 can be made compact while warming up the FC stack 11 and adjusting the temperature of the FC stack 11 to within the target temperature range TT.

[0057] It should be noted that when the control unit 14 warms up the FC stack 11 and adjusts the temperature of the FC stack 11 to fall within the target temperature range, the control unit 14 ends the warm-up control and ends the warm-up of the FC stack 11.

[0058] In addition, when the control unit 14 performs warm-up control in this manner to warm up the FC stack 11, it may increase the rotation speed of the supply side blower 62 above the normal rotation speed when the FC stack 11 is generating electricity, i.e., the rotation speed when the temperature of the FC stack 11 is within the target temperature range TT when the FC stack 11 is generating electricity.

[0059] As a result, even if the downstream side of the FC stack 11 is throttled by the exhaust air valve 71 when the FC stack 11 is generating electricity, the rotation speed of the supply blower 62 is increased, so the pressure inside the FC stack 11 can be further increased and the warm-up efficiency is improved.

[0060] Furthermore, the control unit 14 may perform the above-mentioned warm-up control to warm up the FC stack 11 when the temperature of the FC stack 11 is lower than the target temperature range TT not only when the FC stack 11 is generating electricity but also when the fuel cell system 1 is starting up before the FC stack 11 is generating electricity. Note that when the fuel cell system 1 is starting up, the supply side blower 62 is started with the opening degree of the discharge side air valve 71 set to a smaller opening degree than the normal opening degree when the FC stack 11 is generating electricity.

[0061] This allows the FC stack 11 to be warmed up and the temperature of the FC stack 11 to be adjusted to within the target temperature range TT when the fuel cell system 1 is started, so that the FC stack 11 can efficiently generate power immediately after the fuel cell system 1 is started.

[0062] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. Needless to say, various improvements and modifications are possible without departing from the spirit and scope of the present disclosure.

[0063] For example, in the cooling control or warming control, the control unit 14 may fully close (that is, set the opening degree of the supply side air valve 63 or the discharge side air valve 71 to 0). [Explanation of symbols]

[0064] 1. Fuel cell system 11 FC Stack 12 Hydrogen Systems 13 Air Systems 14 Control section 51 Air supply passage 52 Air off-gas exhaust passage 62 Supply side blower 63 Supply side air valve 71 Exhaust air valve 72 Exhaust Blower 81 Water Tank TT Target temperature range

Claims

1. A fuel cell that generates electricity by receiving a fuel gas and an oxidant gas; a gas supply passage for supplying the oxidant gas to the fuel cell; an off-gas exhaust passage through which an oxidant off-gas, which is the oxidant gas not used for power generation, is exhausted from the fuel cell; a supply-side valve provided in the gas supply passage for adjusting a flow rate of the oxidant gas; a suction section provided in the off-gas discharge passage for suctioning the oxidant off-gas from the fuel cell; A control unit that controls the supply side valve and the suction unit, when the temperature of the fuel cell is higher than a predetermined temperature range, the control unit performs cooling control to cool the fuel cell by reducing an opening degree of the supply side valve to a smaller opening degree than when the temperature of the fuel cell is within the predetermined temperature range during power generation of the fuel cell; A fuel cell system comprising:

2. A fuel cell that generates electricity by receiving a fuel gas and an oxidant gas; a gas supply passage for supplying the oxidant gas to the fuel cell; an off-gas exhaust passage through which an oxidant off-gas, which is the oxidant gas not used for power generation, is exhausted from the fuel cell; a discharge side valve provided in the off-gas discharge passage for adjusting a flow rate of the oxidant off-gas; a discharge portion provided in the gas supply passage and configured to discharge the oxidant gas to the fuel cell; A control unit that controls the discharge side valve and the discharge unit, when the temperature of the fuel cell is lower than a predetermined temperature range, the control unit performs warm-up control to warm up the fuel cell by reducing the opening degree of the exhaust side valve compared to the opening degree when the temperature of the fuel cell is within the predetermined temperature range during power generation of the fuel cell; A fuel cell system comprising:

3. 3. The fuel cell system according to claim 1, the control unit, when performing the cooling control or the warming control, increases the rotation speed of the suction unit or the discharge unit to a value higher than the rotation speed when the temperature of the fuel cell is within the predetermined temperature range during power generation of the fuel cell; A fuel cell system comprising:

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