Fuel cell system

Abstract

To provide a fuel cell system that can effectively utilize anode off-gas to improve power generation efficiency.SOLUTION: A fuel cell system 1 according to an embodiment of the present disclosure includes a fuel cell 11, a hydrogen gas supply passage 12, a reformer 16, a fuel supply passage 14, a hydrogen off-gas circulation passage 13, a water supply passage 18, and a storage tank 19, and the hydrogen off-gas circulation passage 13 includes a heat exchanger 24 that passes through the storage tank 19, and performs heat exchange between an upstream hydrogen off-gas circulation passage 13A and the water supply passage 18, and between the upstream hydrogen off-gas circulation passage 13A and a downstream hydrogen off-gas circulation passage 13B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to a fuel cell system.

Background Art

[0002] Patent Document 1 discloses a fuel cell system that circulates anode off-gas to a reformer to generate anode gas in the reformer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the fuel cell system disclosed in Patent Document 1, since the anode off-gas is cooled by a heat recovery cooler, the heat of the anode off-gas is wasted and the anode off-gas cannot be effectively utilized.

[0005] Therefore, this disclosure has been made to solve the above problems, and an object thereof is to provide a fuel cell system capable of improving power generation efficiency while effectively utilizing anode off-gas.

Means for Solving the Problems

[0006] One aspect of this disclosure made to solve the above problems is a fuel cell system including a fuel cell, an anode gas supply passage that supplies anode gas to the fuel cell, a reformer that generates the anode gas from fuel, a fuel supply passage that supplies the fuel to the reformer, an anode off-gas circulation passage that circulates anode off-gas, which is the unused anode gas in the fuel cell, from the fuel cell to the reformer, a water supply passage that supplies water to the reformer, and a storage unit that stores water. A combustor is provided separately from the reformer and is used to obtain heat to raise the temperature of the reformer.The anode-off gas circulation passage passes through the storage section and has a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the water supply passage. The reformer generates the anode gas from the anode gas supplied from the anode gas circulation passage, the water supplied from the water supply passage, and the fuel supplied from the fuel supply passage. It is characterized by the following.

[0007] According to this embodiment, the heat exchanger can lower the temperature of the anode off gas flowing through the anode off gas circulation passage upstream of the storage section. Then, by passing the cooled anode off gas through the water stored in the storage section, the water vapor contained in the anode off gas can be removed. Therefore, by circulating the anode off gas from which the water vapor has been removed to a reformer and supplying it to the fuel cell as anode gas from the reformer, the fuel contained in the anode off gas can be reused without being discarded, thereby improving the power generation efficiency of the fuel cell.

[0008] Furthermore, the water vapor removed from the anode off gas can be reused as water stored in the storage section. In addition, the heat exchanger can be used to increase the temperature of the water flowing through the water supply section by utilizing the heat from the anode off gas flowing through the anode off gas circulation passage upstream of the storage section.

[0009] Therefore, it is possible to improve the power generation efficiency in fuel cells while effectively utilizing anode off-gas.

[0010] In the above embodiment, it is preferable that the heat exchanger performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the anode-off gas circulation passage located downstream of the storage section.

[0011] According to this embodiment, the heat exchanger can more effectively lower the temperature of the anode off gas flowing through the anode off gas circulation passage upstream of the storage section, thereby removing water vapor contained in the anode off gas. As a result, the power generation efficiency in the fuel cell can be more effectively improved.

[0012] Furthermore, the heat exchanger can utilize the heat from the anode off gas flowing through the anode off gas circulation passage upstream of the storage unit to raise the temperature of the anode off gas flowing through the anode off gas circulation passage downstream of the storage unit.

[0013] Another embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, a reformer for generating the anode gas from fuel, a fuel supply passage for supplying the fuel to the reformer, an anode off gas circulation passage for circulating anode off gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, a water supply passage for supplying water to the reformer, and a storage section for storing water, A combustor is provided separately from the reformer and is used to obtain heat to raise the temperature of the reformer. The anode-off gas circulation passage passes through the storage section and has a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the anode-off gas circulation passage located downstream of the storage section. The reformer generates the anode gas from the anode gas supplied from the anode gas circulation passage, the water supplied from the water supply passage, and the fuel supplied from the fuel supply passage. It is preferable.

[0014] According to this embodiment, the heat exchanger can lower the temperature of the anode off gas flowing through the anode off gas circulation passage upstream of the storage section. Then, by passing the cooled anode off gas through the water stored in the storage section, the water vapor contained in the anode off gas can be removed. Therefore, by circulating the anode off gas from which the water vapor has been removed to a reformer and supplying it to the fuel cell as anode gas from the reformer, the fuel contained in the anode off gas can be reused without being discarded, thereby improving the power generation efficiency of the fuel cell.

[0015] Furthermore, the water vapor removed from the anode off gas can be reused as water stored in the storage section. In addition, the heat exchanger can utilize the heat from the anode off gas flowing through the anode off gas circulation passage upstream of the storage section to raise the temperature of the anode off gas flowing through the anode off gas circulation passage downstream of the storage section.

[0016] Therefore, it is possible to improve the power generation efficiency in fuel cells while effectively utilizing anode off-gas.

[0017] In the above embodiment, the storage unit is provided with a water supply device that supplies water to the reformer via the water supply passage and a temperature sensor that measures the temperature of the water. It is preferable to estimate the amount of water contained in the anode off gas flowing through the anode off gas circulation passage downstream of the storage unit based on the measurement value of the temperature sensor, and to determine the amount of water supplied to the reformer by the water supply device by subtracting the estimated amount of water contained in the anode off gas from the amount of water required by the reformer.

[0018] According to this embodiment, only the actual amount of water required needs to be supplied to the reformer, thus reducing the power consumption and miniaturization of the water supply device.

[0019] In the above embodiment, it is preferable that at least a portion of the fuel supply passage is located inside the storage section or in contact with the storage section.

[0020] According to this embodiment, heat exchange can be performed between the fuel supply passage and the water stored in the storage section. As a result, the temperature of the water stored in the storage section can be lowered, and the temperature of the fuel flowing through the fuel supply passage can be raised. Therefore, even if the fuel temperature drops due to the influence of ambient temperature or other factors, the fuel temperature can be raised before being supplied to the reformer.

[0021] In the above embodiment, it is preferable that the fuel cell has a cathode gas supply passage for supplying cathode gas, and at least a portion of the cathode gas supply passage is located inside the storage section or in contact with the storage section.

[0022] According to this aspect, heat exchange can be performed between the cathode gas supply passage and the water stored in the storage unit. Therefore, the temperature of the water stored in the storage unit can be lowered, and the temperature of the cathode gas flowing through the cathode gas supply passage can be raised. Accordingly, even when the temperature of the cathode gas drops due to the influence of the outside air temperature or the like, the cathode gas can be supplied to the fuel cell after raising the temperature of the cathode gas.

[0023] In the above aspect, it preferably has a combustor for obtaining heat for raising the temperature of the reformer, and at least a part of the exhaust passage of the combustor is arranged inside the storage unit or so as to be in contact with the storage unit.

[0024] According to this aspect, when the outside air state is such that the storage unit may freeze, the heat of the exhaust from the combustor can prevent the storage unit from freezing.

[0025] In the above aspect, the exhaust passage of the combustor preferably includes a first exhaust passage arranged inside the storage unit or so as to be in contact with the storage unit, and a second exhaust passage arranged apart from the storage unit, and the first exhaust passage and the second exhaust passage are switchable.

[0026] According to this aspect, control according to the temperature rise requirement of the storage unit can be performed. Furthermore, another embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, a reformer for generating anode gas from fuel, a fuel supply passage for supplying fuel to the reformer, an anode off gas circulation passage for circulating anode off gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, a water supply passage for supplying water to the reformer, and a storage section for storing water, wherein the anode off gas circulation passage passes through the storage section, and from the storage section The device has a heat exchanger that performs heat exchange between the anode off gas circulation passage located upstream and the water supply passage, and the storage section is provided with a water supply device that supplies water to the reformer via the water supply passage and a temperature sensor that measures the temperature of the water, and is characterized in that, based on the measurement value of the temperature sensor, the amount of water contained in the anode off gas flowing through the anode off gas circulation passage located downstream of the storage section is estimated, and the amount of water supplied to the reformer by the water supply device is determined by subtracting the estimated amount of water contained in the anode off gas from the amount of water required by the reformer. Furthermore, another embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, a reformer for generating anode gas from fuel, a fuel supply passage for supplying fuel to the reformer, an anode off gas circulation passage for circulating anode off gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, a water supply passage for supplying water to the reformer, and a storage section for storing water, wherein the anode off gas circulation passage passes through the storage section, and the anode off gas is located upstream of the storage section. The reformer has a heat exchanger that performs heat exchange between an anode off gas circulation passage and the anode off gas circulation passage located downstream of the storage section, and the storage section is provided with a water supply device that supplies water to the reformer via the water supply passage and a temperature sensor that measures the temperature of the water, and the amount of water contained in the anode off gas flowing through the anode off gas circulation passage located downstream of the storage section is estimated based on the measurement value of the temperature sensor, and the amount of water supplied to the reformer by the water supply device is determined by subtracting the estimated amount of water contained in the anode off gas from the amount of water required by the reformer. Furthermore, another embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, a reformer for generating anode gas from fuel, a fuel supply passage for supplying fuel to the reformer, an anode off gas circulation passage for circulating anode off gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, a water supply passage for supplying water to the reformer, and a storage section for storing water, wherein the anode off gas circulation passage passes through the storage section The reformer is characterized by having a heat exchanger that performs heat exchange between the anode-off gas circulation passage and the water supply passage located upstream of the storage section, a combustor for obtaining heat to raise the temperature of the reformer, at least a portion of the exhaust passage of the combustor being located inside or in contact with the storage section, and the exhaust passage of the combustor comprising a first exhaust passage located inside or in contact with the storage section, and a second exhaust passage located away from the storage section, and the first exhaust passage and the second exhaust passage being switchable. Furthermore, another embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, a reformer for generating the anode gas from fuel, a fuel supply passage for supplying fuel to the reformer, an anode off gas circulation passage for circulating anode off gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, a water supply passage for supplying water to the reformer, and a storage section for storing water, wherein the anode off gas circulation passage passes through the storage section, and the storage section The reformer has a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream and the anode-off gas circulation passage located downstream of the storage section, and a combustor for obtaining heat to raise the temperature of the reformer, and at least a portion of the exhaust passage of the combustor is arranged inside or in contact with the storage section, and the exhaust passage of the combustor comprises a first exhaust passage arranged inside or in contact with the storage section and a second exhaust passage arranged away from the storage section, and the first exhaust passage and the second exhaust passage are switchable.

Advantages of the Invention

[0027] According to the fuel cell system of the present disclosure, the anode off-gas can be effectively utilized to improve the power generation efficiency.

Brief Description of the Drawings

[0028] [Figure 1] It is a configuration diagram of the fuel cell system of the first embodiment. [Figure 2] This figure shows an example where two valves are used instead of a three-way valve. [Figure 3] This is a flowchart illustrating the method for determining the pumping volume of a water pump. [Figure 4] This is a diagram showing the configuration of the storage tank and its surroundings in the fuel cell system of the second embodiment. [Figure 5] This is a diagram showing the configuration of the storage tank and its surroundings in a fuel cell system according to the third embodiment. [Figure 6] This is a diagram showing the configuration of the storage tank and its surroundings in the fuel cell system of the fourth embodiment. [Modes for carrying out the invention]

[0029] Embodiments of the fuel cell system described herein will be described below.

[0030] <First Embodiment> First, the first embodiment will be described.

[0031] (Overview of fuel cell systems) As shown in Figure 1, the fuel cell system 1 of this embodiment includes a fuel cell 11 (FC), a hydrogen gas supply passage 12, a hydrogen off-gas circulation passage 13, an air supply passage 14, an air off-gas discharge passage 15, a reformer 16, a fuel supply passage 17, a water supply passage 18, a storage tank 19, a combustor 20, and a control unit 21.

[0032] The fuel cell 11 generates electricity using hydrogen gas supplied from the hydrogen gas supply passage 12 and air supplied from the air supply passage 14. Hydrogen gas is an example of the "anode gas" in this disclosure, and air is an example of the "cathode gas" in this disclosure.

[0033] The hydrogen gas supply passage 12 is a passage that supplies hydrogen gas from the reformer 16 to the fuel cell 11. The hydrogen gas supply passage 12 is an example of the "anode gas supply passage" in this disclosure.

[0034] The hydrogen off-gas circulation passage 13 is a passage for circulating hydrogen off-gas, which is unused hydrogen gas from the fuel cell 11, from the fuel cell 11 to the reformer 16. Note that hydrogen off-gas is an example of "anode off-gas" as defined in this disclosure, and the hydrogen off-gas circulation passage 13 is an example of "anode off-gas circulation passage" as defined in this disclosure.

[0035] This hydrogen off-gas circulation passage 13 comprises an upstream hydrogen off-gas circulation passage 13A and a downstream hydrogen off-gas circulation passage 13B. The upstream hydrogen off-gas circulation passage 13A is a passage located upstream of the storage tank 19 (i.e., upstream of the hydrogen off-gas flow, on the fuel cell 11 side). The downstream hydrogen off-gas circulation passage 13B is a passage located downstream of the storage tank 19 (i.e., downstream of the hydrogen off-gas flow, on the reformer 16 side).

[0036] Furthermore, the hydrogen off-gas circulation passage 13 is equipped with a heat exchanger 22, a three-way valve 23, and a heat exchanger 24, in that order from the fuel cell 11 side.

[0037] The heat exchanger 22 is a device that performs heat exchange between the hydrogen off-gas circulation passage 13 located upstream of the three-way valve 23 and the hydrogen off-gas circulation passage 13B located downstream of the three-way valve 23. The three-way valve 23 is a valve that switches the connection destination of the hydrogen off-gas circulation passage 13 located upstream of the three-way valve 23 to either the upstream hydrogen off-gas circulation passage 13A connected to the storage tank 19, or the combustion gas supply passage 25 connected to the combustor 20. Alternatively, instead of the three-way valve 23, as shown in Figure 2, two valves may be used: valve 30A provided in the upstream hydrogen off-gas circulation passage 13A and valve 30B provided in the combustion gas supply passage 25.

[0038] The heat exchanger 24 is a device that performs heat exchange between the upstream hydrogen off-gas circulation passage 13A and the water supply passage 18, and between the upstream hydrogen off-gas circulation passage 13A and the downstream hydrogen off-gas circulation passage 13B.

[0039] The air supply passage 14 is a passage that supplies air to the fuel cell 11 by driving an air pump 26 provided at its inlet. The air supply passage 14 is equipped with a heat exchanger 28 that performs heat exchange between the air supply passage 14, the fuel supply passage 17, and the exhaust passage 27 of the combustor 20. Note that the air supply passage 14 is an example of the "cathode gas supply passage" in this disclosure. The air pump 26 may also be a blower or a compressor.

[0040] The air off-gas discharge passage 15 is a passage that discharges air off-gas, which is unused air from the fuel cell 11, from the fuel cell 11 to the combustor 20. Note that the air off-gas discharge passage 15 is an example of a "cathode off-gas discharge passage".

[0041] The reformer 16 is a device that generates hydrogen gas from hydrogen off-gas supplied from the hydrogen off-gas circulation passage 13 via the ejector 29, water supplied from the water supply passage 18 via the ejector 29, and fuel supplied from the fuel supply passage 17 via the ejector 29.

[0042] The fuel supply passage 17 is a passage that supplies fuel (for example, a hydrocarbon fuel gas such as city gas mainly composed of methane) to the reformer 16 via the ejector 29, driven by a fuel pump 31 located at its inlet. The fuel pump 31 may also be a blower or a compressor.

[0043] In this fuel supply passage 17, a desulfurizer 32, a three-way valve 33, and a heat exchanger 28 are provided in order from the fuel pump 31 side.

[0044] The desulfurizer 32 is a device that removes sulfur components from the fuel. The three-way valve 33 is a valve that switches the connection destination of the fuel supply passage 17, which is connected to the desulfurizer 32 and the fuel pump 31, between the fuel supply passage 17 that is connected to the reformer 16 via the ejector 29 and the combustion gas supply passage 34 that is connected to the combustor 20. Note that two valves may be used instead of the three-way valve 33.

[0045] The water supply passage 18 is a passage that supplies water from the storage tank 19 to the reformer 16 via the ejector 29. A heat exchanger 24 and a vaporizer 35 are provided in this water supply passage 18, starting from the storage tank 19 side.

[0046] The vaporizer 35 is a device that uses the heat from the exhaust passage 27 of the combustor 20 to vaporize the water flowing through the water supply passage 18.

[0047] The storage tank 19 is a tank that stores water supplied to the reformer 16 via the water supply passage 18 and the ejector 29. The storage tank 19 is equipped with a water pump 36, a temperature sensor 37, and a bubbler 38. Note that the storage tank 19 is an example of the "storage unit" in this disclosure.

[0048] The water pump 36 is a pump that supplies water from the storage tank 19 to the reformer 16 via the water supply passage 18 and the ejector 29. The temperature sensor 37 is a sensor that measures the temperature of the water stored in the storage tank 19. The bubbler 38 is a component that creates fine bubbles of hydrogen off-gas supplied from the upstream hydrogen off-gas circulation passage 13A in the water stored in the storage tank 19. Note that the water pump 36 is an example of the "water supply device" in this disclosure.

[0049] Furthermore, the storage tank 19 is equipped with a drain valve 39 that opens and closes the drainage channel from the storage tank 19.

[0050] The combustor 20 is a device that generates heat to raise the temperature of the reformer 16 by burning air off-gas supplied from the air off-gas discharge passage 15, hydrogen off-gas supplied as a combustion gas from the combustion gas supply passage 25, and fuel supplied as a combustion gas from the combustion gas supply passage 34. The exhaust from the combustor 20 is then discharged to the outside of the fuel cell system 1 via the exhaust passage 27.

[0051] The control unit 21 is a device that controls each component of the fuel cell system 1, such as the combustor 20, the three-way valve 23, the air pump 26, the fuel pump 31, the three-way valve 33, and the water pump 36, and is, for example, an ECU. In this embodiment, the control unit 21 receives measurement data from the temperature sensor 37.

[0052] (Regarding the use of hydrogen off-gas) In this embodiment, the hydrogen off-gas circulation passage 13 passes through the storage tank 19. Specifically, the upstream hydrogen off-gas circulation passage 13A is connected to a bubbler 38 located inside the storage tank 19. The upstream hydrogen off-gas circulation passage 13A is then connected to the downstream hydrogen off-gas circulation passage 13B via the bubbler 38, the water stored in the storage tank 19, and the space above the water stored in the storage tank 19.

[0053] Furthermore, the heat exchanger 24 performs heat exchange between the upstream hydrogen off-gas circulation passage 13A and the water supply passage 18, and between the upstream hydrogen off-gas circulation passage 13A and the downstream hydrogen off-gas circulation passage 13B.

[0054] In this way, the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A is cooled by water sent from the storage tank 19 toward the reformer 16 by the water pump 36, and by the hydrogen off-gas flowing through the downstream hydrogen off-gas circulation passage 13B.

[0055] This allows the temperature of the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A to be lowered. As a result, the cooled hydrogen off-gas can be introduced into the bubbler 38, and then passed through the water stored in the storage tank 19 from the bubbler 38 to remove the water vapor contained in the hydrogen off-gas.

[0056] Furthermore, the steam removed from the hydrogen off-gas can be reused as water stored in the storage tank 19. In addition, the heat exchanger 24 can utilize the heat of the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A to raise the temperature of the water flowing through the water supply passage 18 to a temperature suitable for power generation. Furthermore, the heat exchanger 24 can also utilize the heat of the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A to raise the temperature of the hydrogen off-gas flowing through the downstream hydrogen off-gas circulation passage 13B to a temperature suitable for power generation.

[0057] In this embodiment, the control unit 21 controls the amount of water supplied to the reformer 16 by the water pump 36.

[0058] Specifically, the control unit 21 estimates the amount of water contained in the hydrogen off-gas flowing through the downstream hydrogen off-gas circulation passage 13B, for example, using a saturated vapor pressure curve based on the measurement values ​​from the temperature sensor 37. Then, the control unit 21 subtracts the estimated amount of water contained in the hydrogen off-gas from the amount of water required by the reformer 16 to determine the amount of water to be supplied to the reformer 16 by the water pump 36. Finally, the control unit 21 supplies this determined amount of water from the storage tank 19 to the reformer 16 using the water pump 36.

[0059] Here, the control unit 21 determines the amount of water supplied to the reformer 16 by the water pump 36, as shown in the flowchart in Figure 3.

[0060] As shown in Figure 3, the control unit 21 measures the tank temperature Tw using the temperature sensor 37 (step S1). Here, the tank temperature Tw is the temperature of the water inside the storage tank 19 (more specifically, above the bubbler 38).

[0061] Next, the control unit 21 estimates the amount of moisture in the circulation system (step S2). That is, the control unit 21 estimates the amount of moisture contained in the anode off-gas flowing through the downstream hydrogen off-gas circulation passage 13B based on the measurement value from the temperature sensor 37, i.e., the tank temperature Tw.

[0062] Next, the control unit 21 subtracts the amount of water in the circulation system from the amount of water required for reforming to determine the pumping volume of the water pump 36 (WP) (step S3). That is, the control unit 21 subtracts the amount of water contained in the hydrogen off-gas estimated in step S2 from the amount of water required in the reformer 16 to determine the amount of water supplied to the reformer 16 by the water pump 36.

[0063] The control unit 21 then supplies the determined amount of water from the storage tank 19 to the reformer 16 using the water pump 36.

[0064] (Effects of this embodiment) As described above, according to this embodiment, the hydrogen off-gas circulation passage 13 passes through the storage tank 19. The heat exchanger 24 performs heat exchange between the upstream hydrogen off-gas circulation passage 13A and the water supply passage 18. The heat exchanger 24 also performs heat exchange between the upstream hydrogen off-gas circulation passage 13A and the downstream hydrogen off-gas circulation passage 13B.

[0065] In this way, the heat exchanger 24 can lower the temperature of the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A. Then, by introducing the cooled hydrogen off-gas into the bubbler 38 and passing it through the water stored in the storage tank 19, the water vapor contained in the hydrogen off-gas can be removed. As a result, by circulating the hydrogen off-gas, from which the water vapor has been removed, to the reformer 16 and supplying it as hydrogen gas from the reformer 16 to the fuel cell 11, the power generation efficiency of the fuel cell 11 can be improved.

[0066] Furthermore, the water vapor removed from the hydrogen off-gas can be reused as water stored in the storage tank 19. In addition, the heat exchanger 24 can utilize the heat of the hydrogen off-gas flowing through the upstream hydrogen off-gas circulation passage 13A to raise the temperature of the water flowing through the water supply passage 18 and the hydrogen off-gas flowing through the downstream hydrogen off-gas circulation passage 13B.

[0067] Therefore, it is possible to improve the power generation efficiency in the fuel cell 11 while effectively utilizing hydrogen off-gas.

[0068] Furthermore, the control unit 21 estimates the amount of water contained in the hydrogen off-gas flowing through the downstream hydrogen off-gas circulation passage 13B based on the measurement value from the temperature sensor 37, and subtracts the estimated amount of water contained in the hydrogen off-gas from the amount of water required by the reformer 16 to determine the amount of water supplied to the reformer 16 by the water pump 36.

[0069] This means the water pump 36 only needs to supply the amount of water actually required to the reformer 16. Therefore, the power consumption of the water pump 36 can be reduced and its size can be minimized.

[0070] <Second Embodiment> Next, we will describe the second embodiment, explaining the differences from the first embodiment, and omitting the explanation of the points that are common to the first embodiment.

[0071] In this embodiment, as shown in Figure 4, a portion of the fuel supply passage 17 is located inside the storage tank 19.

[0072] This allows heat exchange to occur between the fuel supply passage 17 and the water stored in the storage tank 19. As a result, the temperature of the water stored in the storage tank 19 can be lowered, and the temperature of the fuel flowing through the fuel supply passage 17 can be raised. Therefore, even if the fuel temperature drops due to the influence of ambient temperature or other factors, the fuel temperature can be raised to a temperature suitable for power generation before being supplied to the reformer 16.

[0073] Furthermore, a portion of the fuel supply passage 17 may be positioned in contact with the side or bottom of the storage tank 19. Alternatively, the entire fuel supply passage 17 may be positioned inside the storage tank 19 or in contact with the storage tank 19.

[0074] <Third Embodiment> Next, we will describe the third embodiment, explaining the differences from the first and second embodiments, and omitting the explanation of the points that are common to the first and second embodiments.

[0075] As shown in Figure 5, a portion of the air supply passage 14 is located inside the storage tank 19.

[0076] This allows heat exchange to occur between the air supply passage 14 and the water stored in the storage tank 19. As a result, the temperature of the water stored in the storage tank 19 can be lowered, and the temperature of the air flowing through the air supply passage 14 can be raised. Therefore, even if the air temperature drops due to the influence of ambient temperature or other factors, the air temperature can be raised to a temperature suitable for power generation before being supplied to the fuel cell 11.

[0077] Furthermore, a portion of the air supply passage 14 may be positioned in contact with the side or bottom of the storage tank 19. Alternatively, the entire air supply passage 14 may be positioned inside the storage tank 19 or in contact with the storage tank 19.

[0078] <Fourth Embodiment> Next, the fourth embodiment will be described, explaining the differences from the first to third embodiments, and omitting the explanation of the points that are common to the first to third embodiments.

[0079] In this embodiment, as shown in Figure 6, the exhaust passage 27 of the combustor 20 includes a first exhaust passage 27A and a second exhaust passage 27B. A portion of the first exhaust passage 27A is located inside the storage tank 19. On the other hand, the second exhaust passage 27B is located away from the storage tank 19.

[0080] This prevents the storage tank 19 from freezing when the ambient temperature is such that it may freeze, by using the heat from the exhaust gas from the combustor 20.

[0081] Furthermore, a three-way valve 41 is provided in the exhaust passage 27. This three-way valve 41 allows switching between the first exhaust passage 27A and the second exhaust passage 27B. In other words, the connection destination of the exhaust passage 27 located upstream of the three-way valve 41 (i.e., upstream of the exhaust flow, towards the combustor 20) can be switched to either the first exhaust passage 27A or the second exhaust passage 27B by the three-way valve 41. Note that two valves may be used instead of the three-way valve 41.

[0082] This allows the control unit 21 to perform control in response to requests for temperature increase in the storage tank 19.

[0083] Furthermore, a portion of the first exhaust passage 27A may be positioned in contact with the side or bottom surface of the storage tank 19. Alternatively, the entire first exhaust passage 27A may be positioned inside the storage tank 19 or in contact with the storage tank 19.

[0084] It should be noted that the embodiments described above are merely illustrative examples and do not limit this disclosure in any way. Various improvements and modifications are possible without departing from the gist of the disclosure.

[0085] For example, the fuel cell system 1 may have a configuration that combines at least two of the second, third, and fourth embodiments with respect to the first embodiment.

[0086] Furthermore, the heat exchanger 24 may be a device that performs only one of the following: heat exchange between the upstream hydrogen off-gas circulation passage 13A and the water supply passage 18, and heat exchange between the upstream hydrogen off-gas circulation passage 13A and the downstream hydrogen off-gas circulation passage 13B. [Explanation of symbols]

[0087] 1. Fuel cell system 11 Fuel Cell 12 Hydrogen gas supply channel 13. Hydrogen off-gas circulation path 13A Upstream hydrogen off-gas circulation passage 13B Downstream hydrogen off-gas circulation passage 14 Air supply passage 15 Air off-gas discharge passage 16. Modifier 17 Fuel supply passage 18 Water supply passage 19 Storage tanks 20 Combustors 21 Control Unit 24 Heat exchanger 27 Exhaust passage 27A First Exhaust Passage 27B Second Exhaust Passage 36 Water pump 37 Temperature Sensor 38 Bubbler 41 Three-way valve Tw Tank internal temperature

Claims

1. Fuel cells and an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, A combustor is provided separately from the reformer and is used to obtain heat to raise the temperature of the reformer. The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the water supply passage, The reformer generates the anode gas from the anode off gas supplied from the anode off gas circulation passage, the water supplied from the water supply passage, and the fuel supplied from the fuel supply passage. A fuel cell system characterized by the following.

2. In the fuel cell system of claim 1, The heat exchanger performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the anode-off gas circulation passage located downstream of the storage section. A fuel cell system characterized by the following.

3. Fuel cells and an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, A combustor is provided separately from the reformer and is used to obtain heat to raise the temperature of the reformer. The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode off-gas circulation passage located upstream of the storage section and the anode off-gas circulation passage located downstream of the storage section. The reformer generates the anode gas from the anode off gas supplied from the anode off gas circulation passage, the water supplied from the water supply passage, and the fuel supplied from the fuel supply passage. A fuel cell system characterized by the following.

4. In any one of claims 1 to 3, The storage section includes, A water supply device that supplies water to the reformer via the water supply passage, A temperature sensor that measures the temperature of water, A system was established, Based on the temperature sensor's measurement, the amount of water contained in the anode off gas flowing through the anode off gas circulation passage downstream of the storage unit is estimated. The amount of water supplied to the reformer by the water supply device is determined by subtracting the estimated amount of water contained in the anode off-gas from the amount of water required by the reformer. A fuel cell system characterized by the following.

5. In any one of claims 1 to 3, At least a portion of the fuel supply passage is located inside the storage section or in contact with the storage section. A fuel cell system characterized by the following.

6. In any one of claims 1 to 3, It has a cathode gas supply passage for supplying cathode gas to the fuel cell, At least a portion of the cathode gas supply passage is located inside the storage section or in contact with the storage section. A fuel cell system characterized by the following.

7. In any one of claims 1 to 3, At least a portion of the exhaust passage of the combustor is located inside the storage section or in contact with the storage section. A fuel cell system characterized by the following.

8. In the fuel cell system of claim 7, The exhaust passage of the aforementioned combustor is A first exhaust passage is disposed inside the storage section or in contact with the storage section, A second exhaust passage is located separately from the aforementioned storage section, Equipped with, The first exhaust passage and the second exhaust passage are switchable. A fuel cell system characterized by the following.

9. A fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the water supply passage, The storage section includes, A water supply device that supplies water to the reformer via the water supply passage, A temperature sensor that measures the temperature of water, A system was established, Based on the temperature sensor's measurement, the amount of water contained in the anode off gas flowing through the anode off gas circulation passage downstream of the storage unit is estimated. The amount of water supplied to the reformer by the water supply device is determined by subtracting the estimated amount of water contained in the anode off-gas from the amount of water required by the reformer. A fuel cell system characterized by the following.

10. A fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode off-gas circulation passage located upstream of the storage section and the anode off-gas circulation passage located downstream of the storage section. The storage section includes, A water supply device that supplies water to the reformer via the water supply passage, A temperature sensor that measures the temperature of water, A system was established, Based on the temperature sensor's measurement, the amount of water contained in the anode off gas flowing through the anode off gas circulation passage downstream of the storage unit is estimated. The amount of water supplied to the reformer by the water supply device is determined by subtracting the estimated amount of water contained in the anode off-gas from the amount of water required by the reformer. A fuel cell system characterized by the following.

11. A fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode-off gas circulation passage located upstream of the storage section and the water supply passage, The reformer has a combustor for obtaining heat to raise its temperature, At least a portion of the exhaust passage of the combustor is located inside the storage section or in contact with the storage section. The exhaust passage of the aforementioned combustor is A first exhaust passage is disposed inside the storage section or in contact with the storage section, A second exhaust passage is located separately from the aforementioned storage section, Equipped with, The first exhaust passage and the second exhaust passage are switchable. A fuel cell system characterized by the following.

12. A fuel cell, an anode gas supply passage for supplying anode gas to the fuel cell, A reformer that generates the anode gas from fuel, A fuel supply passage for supplying the fuel to the reformer, an anode off-gas circulation passage for circulating the anode off-gas, which is the anode gas unused in the fuel cell, from the fuel cell to the reformer, A water supply passage for supplying water to the reformer, Having a storage section for storing water, In fuel cell systems, The anode off gas circulation passage passes through the storage section. The system includes a heat exchanger that performs heat exchange between the anode off-gas circulation passage located upstream of the storage section and the anode off-gas circulation passage located downstream of the storage section. The reformer has a combustor for obtaining heat to raise its temperature, At least a portion of the exhaust passage of the combustor is located inside the storage section or in contact with the storage section. The exhaust passage of the aforementioned combustor is A first exhaust passage is disposed inside the storage section or in contact with the storage section, A second exhaust passage is located separately from the aforementioned storage section, Equipped with, The first exhaust passage and the second exhaust passage are switchable. A fuel cell system characterized by the following.

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