Fuel battery system

Abstract

To provide a fuel battery system capable of suppressing a decrease in user convenience.SOLUTION: A fuel battery system 100 includes: a combustion part 15 that fuels off-gas discharged from a fuel battery cell C; a condensation recovery part 51 that condenses and recovers water contained in combustion exhaust gas discharged from the combustion part 15; a water tank 21 that stores water recovered by the condensation recovery part 51; a water amount measuring part 23 that measures the amount of water stored in the water tank 21; and a control part 10. The control part 10 determines whether or not the water amount measured by the water amount measuring part 23 is equal to or less than a first water amount threshold value, and when determining that the water amount is equal to or less than the first water amount threshold value, acquires weather forecast data indicating future weather in an installation area where the water tank 21 is installed, and determines whether or not switching of an operation mode from a normal operation mode to a water recovery operation mode is necessary based on water balance forecast data generated based on the weather forecast data and data of a past operation result in the normal operation mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a solid oxide fuel cell system that includes a reforming section that steam reforms raw fuel and a water recovery tank that stores water to be supplied to the reforming section, and when the water level in the water recovery tank drops to a low water level, it switches from operating in a normal operation mode to operating in a water recovery operation mode that reduces power generation output and can recover more water than in the normal operation mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-277973 Summary of the Invention [Problem to be solved by the invention]

[0004] In the water recovery operation mode of the solid oxide fuel cell system disclosed in Patent Document 1, the number of times the water recovery operation mode is operated or the operating time of the water recovery operation mode may increase during periods of relatively high temperature, such as summer, which may reduce convenience for users.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fuel cell system that can suppress a decrease in convenience for users. [Means for solving the problem]

[0006] The fuel cell system according to the present invention, which achieves the above object, has the following characteristic configuration: a reforming unit that generates fuel gas by steam reforming a raw fuel; a fuel cell that generates electricity based on the fuel gas and an oxidant gas; a combustion section that uses the off-gas discharged from the fuel cell as fuel; a condensation recovery section that condenses and recovers water contained in the combustion exhaust gas discharged from the combustion section; a water tank that stores the water recovered in the condensation recovery unit; a water volume measuring unit that measures the volume of water stored in the water tank; a water supply unit that supplies water used in the steam reforming from the water tank to the reforming unit; a control unit configured to be able to switch between a normal operation mode in which the device is operated in a normal operation mode and a water recovery operation mode in which the device is operated in an operation mode in which a larger amount of water is recovered than in the normal operation mode; Equipped with The control unit determines whether the water volume measured by the water volume measuring unit is less than or equal to a first water volume threshold, and if it determines that the water volume is less than or equal to the first water volume threshold, determines whether or not the operation mode needs to be switched from the normal operation mode to the water recovery operation mode based on weather forecast data indicating future weather in the installation area where the water tank is installed and water balance prediction data generated based on data on past operating performance in the normal operation mode.

[0007] According to the above characteristic configuration, when it is determined that the amount of water stored in the water tank is below the first water volume threshold, it is determined whether or not to switch operating modes based on weather forecast data and water balance prediction data, thereby preventing an increase in the number of times the water recovery operating mode is operated and the operating time of the water recovery operating mode, and preventing a decrease in convenience for users.

[0008] Another characteristic configuration of the fuel cell system according to the present invention is: a raw fuel supply adjusting unit that adjusts the amount of the raw fuel supplied to the reforming unit; In the water recovery operation mode, the control unit controls the operation of the raw fuel supply adjustment unit to reduce the amount of the raw fuel supplied to the reforming unit compared to the normal operation mode.

[0009] According to the above-described characteristic configuration, in the water recovery operation mode, the amount of raw fuel supplied to the reforming section is reduced compared to the normal operation mode, thereby suppressing the amount of power generated by the fuel cell system, and thereby increasing the amount of water recovered.

[0010] Another characteristic configuration of the fuel cell system according to the present invention is as follows: the weather forecast data includes temperature data indicating the temperature of the installation area, The control unit determines whether the water balance is established based on the water balance prediction data corresponding to the temperature data for a specified period, by determining whether the amount of water condensed by the condensation recovery unit and supplied to the water tank during the specified period is greater than or equal to the amount of water supplied from the water tank to the reforming unit, and determines whether the operating mode needs to be switched based on whether the water balance is established.

[0011] According to the above-described characteristic configuration, the operating mode can be switched to the water recovery operating mode only when necessary, which can prevent an increase in the number of times the water recovery operating mode is operated and the operating time of the water recovery operating mode, thereby preventing a decrease in convenience for the user.

[0012] Another characteristic configuration of the fuel cell system according to the present invention is as follows: When the control unit determines that the water balance is not established during the normal operation mode, it switches the operation mode from the normal operation mode to the water recovery operation mode, and when it determines that the water balance is established, it maintains the operation mode in the normal operation mode.

[0013] According to the above characteristic configuration, the operation mode is switched to the water recovery operation mode only when it is determined that the water balance is not established, so that the number of times the water recovery operation mode is operated can be reduced.

[0014] Another characteristic configuration of the fuel cell system according to the present invention is as follows: When the control unit determines that the water balance is established during the water recovery operation mode, it switches the operation mode from the water recovery operation mode to the normal operation mode, and when it determines that the water balance is not established, it maintains the operation mode in the water recovery operation mode.

[0015] According to the above characteristic configuration, when it is determined that the water balance is established, the operation mode is switched to the normal operation mode, so that the operation time of the water recovery operation mode can be reduced.

[0016] Another characteristic configuration of the fuel cell system according to the present invention is as follows: the control unit determines whether the water volume is equal to or less than a second water volume threshold value that is set to a value smaller than the first water volume threshold value; When it is determined that the water volume is equal to or less than the second water volume threshold, the operation mode is switched from the normal operation mode to the water recovery operation mode regardless of the weather forecast data; While the water volume is equal to or less than the second water volume threshold, the operation mode is maintained in the water recovery operation mode.

[0017] According to the above characteristic configuration, it is possible to prevent the fuel cell system from shutting down due to a water shortage caused by a continuous decrease in the amount of water due to some environmental factor. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing the configuration of a fuel cell system according to a first embodiment. [Figure 2] 4 is a flowchart showing a driving mode switching determination process according to the first embodiment. [Figure 3] FIG. 4 is a diagram showing the relationship between the water level of reforming water, the temperature of the installation area, and the operation mode according to the first embodiment. [Figure 4] FIG. 10 is a schematic diagram showing the configuration of a fuel cell system according to a second embodiment. [Figure 5] 10 is a flowchart showing a driving mode switching determination process according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] A fuel cell system 100 (solid oxide fuel cell system) according to an embodiment of the present invention will be described below with reference to the drawings. FIG.

[0020] First Embodiment [Fuel cell system] 1, the fuel cell system 100 includes a hot module 1, a reforming water supply unit 2, a raw fuel supply unit 3, an oxidant gas supply unit 4, a heat exchange unit 5 (an example of a condensation recovery unit), a hot water circulation unit 6, a communication unit 9, a control unit 10, and an external container H1. The external container H1 houses the hot module 1, the reforming water supply unit 2, the raw fuel supply unit 3, the oxidant gas supply unit 4, the heat exchange unit 5, the hot water circulation unit 6, the communication unit 9, and the control unit 10.

[0021] [Hot Module] The hot module 1 is a fuel cell module that generates electricity by reacting hydrogen and oxygen. The hot module 1 has an inner vessel 11, a vaporization section 12, a reforming section 13, a fuel cell section 14, a combustion section 15, and a combustion catalyst section 16.

[0022] The inner container 11 has heat insulating properties and houses the vaporization section 12, the reforming section 13, the fuel cell section 14, the combustion section 15, and the combustion catalyst section 16. The inner container 11 has an exhaust port 111 formed therein.

[0023] A reforming water supply unit 2, a raw fuel supply unit 3, and an oxidizing gas supply unit 4 are connected to the hot module 1, and reforming water, raw fuel (raw fuel gas), and oxidizing gas (oxidizer) are supplied to the hot module 1. In this embodiment, the reforming water and raw fuel are supplied to the vaporization unit 12, and the oxidizing gas is supplied to the fuel cell unit 14.

[0024] [Vaporization section] In addition to the reforming water and raw fuel, combustion heat generated in the combustion section 15 is supplied to the vaporization section 12. The vaporization section 12 vaporizes the reforming water by utilizing the combustion heat to generate steam. In this embodiment, the vaporization section 12 supplies a mixed gas obtained by mixing the raw fuel with steam vaporized from the reforming water to the reforming section 13.

[0025] [Modification section] The reforming section 13 is supplied with the mixed gas from the vaporizing section 12. Note that the raw fuel may be supplied directly to the reforming section 13 from the raw fuel supply section 3 without passing through the vaporizing section 12.

[0026] In addition to the mixed gas, combustion heat generated in the combustion section 15 is supplied to the reforming section 13. The reforming section 13 generates fuel gas by steam reforming the mixed gas (raw fuel) by utilizing the combustion heat. The fuel gas generated in the reforming section 13 is supplied to the fuel cell section 14.

[0027] [Fuel cell department] The fuel cell section 14 is a cell stack made up of a plurality of cells C (an example of a fuel cell). In this embodiment, the cells C are solid oxide fuel cells, and are made up of an anode (combustion electrode), a cathode (air electrode), and an electrolyte.

[0028] Fuel gas and oxidant gas are supplied to cell C. Cell C generates electricity based on the fuel gas and oxidant gas. Specifically, cell C generates electricity by chemically reacting hydrogen contained in the fuel gas with oxygen contained in the oxidant gas. The fuel gas and oxidant gas not used for power generation are discharged as off-gas (excess gas).

[0029] [Combustion section] The combustion section 15 is supplied with off-gas discharged from the fuel cell section 14 and burns the off-gas to generate combustion heat. The combustion section 15 is disposed between the vaporization section 12 and the reforming section 13 and the fuel cell section 14, and the combustion heat generated in the combustion section 15 increases the temperature of the internal space of the internal vessel 11. The combustion section 15 discharges combustion exhaust gas along with the fuel from the off-gas. The combustion exhaust gas is discharged to the outside of the internal vessel 11 via the combustion catalyst section 16 disposed in the exhaust port 111.

[0030] [Combustion catalyst section] The combustion catalyst section 16 uses oxygen to catalytically combust hydrogen, carbon monoxide, and the like contained in the combustion exhaust gas. The catalytically combusted combustion exhaust gas is discharged to the outside of the inner vessel 11.

[0031] [Reformed Water Supply Department] The reforming water supply unit 2 supplies reforming water (an example of water) to the hot module 1. The reforming water is, for example, tap water from which impurities have been removed. The reforming water supply unit 2 includes a reforming water supply passage L1, an ion exchange resin 20, a water tank 21, a pump 22 (an example of a water supply unit), and a water volume measurement unit 23.

[0032] The ion exchange resin 20 removes impurities from the reforming water (purifying the reforming water) and supplies it to the water tank 21. The water tank 21 stores the reforming water. The pump 22 pumps the reforming water stored in the water tank 21. This causes the reforming water to be supplied to the hot module 1 via the reforming water supply path L1. In other words, the pump 22 supplies the reforming water from the water tank 21 to the hot module 1. The amount of reforming water supplied to the hot module 1 per unit time is adjusted by controlling the operation of the pump 22.

[0033] The water amount measuring unit 23 is disposed in the water tank 21 and measures the amount of reforming water stored in the water tank 21. The water amount measuring unit 23 includes a first water level sensor 231 and a second water level sensor 232 that measure the water level Lw of the reforming water in the water tank 21.

[0034] Each of the first water level sensor 231 and the second water level sensor 232 detects the liquid level of the reforming water to measure the water level Lw (water volume) of the reforming water in the water tank 21. The first water level sensor 231 measures the water level Lw of the reforming water in the water tank 21, which is set as a first water level threshold T1 (an example of a first water volume threshold). The second water level sensor 232 measures the water level Lw of the reforming water in the water tank 21, which is set as a second water level threshold T2.

[0035] The first water level threshold T1 is a value that is preset as the water level Lw at which the control unit 10 starts executing the operation mode switching determination process described below. The second water level threshold T2 is a value that is preset as the water level Lw at which the fuel cell system 100 will no longer be able to continue operation (power generation), and is a value that is smaller than the first water level threshold T1. Hereinafter, the water level Lw of the reforming water in the water tank 21 that exceeds the first water level threshold T1 will be referred to as the standard water level Lw0, the water level Lw of the reforming water in the water tank 21 that is equal to or less than the first water level threshold T1 and exceeds the second water level threshold T2 will be referred to as the low water level Lw1, and the water level Lw of the reforming water that is equal to or less than the second water level threshold T2 will be referred to as the lower limit water level Lw2. That is, in this embodiment, the first water level sensor 231 outputs information indicating that the reforming water in the water tank 21 is at a low water level Lw1, and the second water level sensor 232 outputs information indicating that the reforming water in the water tank 21 is at a lower limit water level Lw2. The output information is transmitted to the control unit 10.

[0036] [Raw and fuel supply department] The raw fuel supply unit 3 supplies raw fuel containing hydrocarbons to the hot module 1. The raw fuel is, for example, city gas, LP gas, or the like.

[0037] The raw fuel supply unit 3 includes a raw fuel supply passage L2, an electromagnetic valve 31 (an example of a raw fuel supply adjusting unit), a fuel flow meter 32, a gas blower 33 (an example of a raw fuel supply adjusting unit), and a desulfurization unit 34. The electromagnetic valve 31 can adjust the flow rate of the raw fuel flowing through the raw fuel supply passage L2. The fuel flow meter 32 measures the flow rate of the raw fuel flowing through the raw fuel supply passage L2. The gas blower 33 supplies the raw fuel to the hot module 1 via the raw fuel supply passage L2. In other words, the amount of raw fuel supplied per unit time to the hot module 1 (reforming unit 13) is adjusted by controlling the operation of the electromagnetic valve 31 and / or the gas blower 33. The desulfurization unit 34 is disposed upstream of the hot module 1 in the flow direction of the raw fuel and removes sulfur from the raw fuel. As a result, the raw fuel from which the sulfur has been removed is supplied to the hot module 1.

[0038] [Oxidant gas supply unit] The oxidant gas supply unit 4 supplies an oxidant gas (air) containing oxygen to the hot module 1. The oxidant gas supply unit 4 has an oxidant gas supply path L3, an oxidant gas blower 41, and an oxidant gas flow meter 42. The oxidant gas blower 41 supplies the oxidant gas to the hot module 1 via the oxidant gas supply path L3. The oxidant gas flow meter 42 measures the flow rate of the oxidant gas flowing through the oxidant gas supply path L3. The amount of oxidant gas supplied to the hot module 1 per unit time is adjusted by controlling the operation of the oxidant gas blower 41.

[0039] [Heat exchange section] The heat exchange section 5 condenses and recovers water contained in the combustion exhaust gas supplied from the combustion catalyst section 16. The heat exchange section 5 has a combustion exhaust gas passage L4, a heat exchanger 51, and a water recovery passage L5.

[0040] The combustion exhaust gas passage L4 is connected to the combustion catalyst section 16 and the heat exchanger 51. The combustion exhaust gas is supplied from the combustion catalyst section 16 to the heat exchanger 51 via the combustion exhaust gas passage L4.

[0041] In the heat exchanger 51, heat is exchanged between the combustion exhaust gas and the hot water circulating through the hot water circulation section 6. This cools the combustion exhaust gas and heats the hot water. When the combustion exhaust gas is cooled, the water contained in the combustion exhaust gas condenses and becomes a liquid (liquid phase). The gas phase components in the combustion exhaust gas are discharged to the outside of the outer container H1 via the combustion exhaust gas passage L4, and the liquid phase components (condensed water) in the combustion exhaust gas are led to the water recovery passage L5.

[0042] The water recovery line L5 branches off from the combustion exhaust gas line L4 downstream of the heat exchanger 51 in the flow direction of the combustion exhaust gas and is connected to the reforming water supply unit 2. The condensed water guided to the water recovery line L5 is supplied to the water tank 21 of the reforming water supply unit 2 via an ion exchange resin 20 arranged at the end of the water recovery line L5 and stored in the water tank 21 as reforming water. In this embodiment, the reforming water is supplied from the water tank 21 to the hot module 1, used for power generation, and then guided to the water tank 21. That is, the fuel cell system 100 achieves water independence, which eliminates the need for external replenishment of water as reforming water. Hereinafter, the balance per unit time (e.g., one hour) between a first water amount indicating the amount of water supplied from the water tank 21 to the reforming unit 13 and a second water amount indicating the amount of water condensed by the heat exchanger 51 and returned to the water tank 21 will be referred to as the water balance. The water balance is considered to be established when the second water amount in a predetermined period is equal to or greater than the first water amount. In addition, the water balance when the first water volume = the second water volume is referred to as zero, the water balance when the first water volume > the second water volume is referred to as negative, and the water balance when the first water volume < the second water volume is referred to as positive.

[0043] [Hot water circulation section] The hot and cold water circulation unit 6 has a hot and cold water circulation path L6, a hot and cold water tank 61, a hot and cold water circulation pump 62, and a hot and cold water cooling unit 63.

[0044] The hot water tank 61 stores hot water. The bottom and top of the hot water tank 61 are connected to the hot water circulation path L6. The hot water circulation pump 62 circulates hot water between the hot water tank 61 and the heat exchanger 5 via the hot water circulation path L6. More specifically, the hot water circulation pump 62 pumps hot water from the bottom of the hot water tank 61 through the heat exchanger 51 to the top of the hot water tank 61. In other words, hot water flows out from the bottom of the hot water tank 61 into the hot water circulation path L6, and hot water heated in the heat exchanger 5 returns from the top to the hot water tank 61. The hot water cooling section 63 is, for example, a radiator, and cools the hot water upstream of the heat exchanger 5 in the direction of hot water flow.

[0045] [Communications Department] The communication unit 9 is a communication device that supports wired or wireless communication methods, and the communication device includes, for example, a NIC (Network Interface Card). The communication unit 9 is configured to be able to communicate with a weather forecast data server Sc that is provided outside the fuel cell system 100. The weather forecast data server Sc is a server that can distribute weather forecast data that indicates future weather in the area where the water tank 21 (fuel cell system 100) is installed (hereinafter referred to as the installation area). The weather forecast data includes temperature data that indicates the temperature Tp in the installation area, and humidity data that indicates the humidity in the installation area. In this embodiment, the temperature data indicates the temperature Tp every hour, and the humidity data indicates the humidity every hour.

[0046] [Control Unit] The control unit 10 is composed of a microcontroller including a processor, semiconductor memory, etc. The control unit 10 controls the operation of each of the hot module 1, the reforming water supply unit 2, the raw fuel supply unit 3, the oxidant gas supply unit 4, the heat exchange unit 5, the hot water circulation unit 6, and the communication unit 9.

[0047] The control unit 10 is configured to be able to switch the operation mode M of the fuel cell system 100 (hot module 1) between a normal operation mode M1 and a water recovery operation mode M2.

[0048] The normal operation mode M1 is an operation mode M in which the fuel cell system 100 operates normally (not in the water recovery operation mode M2). In the normal operation mode M1, the amount of power generation (an example of power generation output) is maintained at a first power generation specified value (for example, 700 W) and the fuel cell system 100 (hot module 1) is operated.

[0049] The water recovery operation mode M2 ​​is an operation mode M in which a larger amount of reforming water is recovered than in the normal operation mode M1. In the water recovery operation mode M2, the fuel cell system 100 (hot module 1) is operated while maintaining the amount of power generation at a second power generation specified value (e.g., 500 W) that is smaller than the first power generation specified value. When switching from the normal operation mode M1 to the water recovery operation mode M2, the control unit 10 controls the operation of the solenoid valve 31 and / or the gas blower 33 of the raw fuel supply unit 3 to reduce the amount of raw fuel supplied to the hot module 1 and lower the amount of power generation. That is, in the water recovery operation mode M2, the control unit 10 controls the operation of the solenoid valve 31 and / or the gas blower 33 to reduce the amount of raw fuel supplied to the hot module 1 compared to the normal operation mode M1. The first power generation specified value and the second power generation specified value are arbitrarily set in advance by a designer of the fuel cell system 100, and data indicating the first power generation specified value and the second power generation specified value are stored in the memory unit 101 of the control unit 10. The storage unit 101 is configured by a semiconductor memory included in the control unit 10.

[0050] The control unit 10 executes an operation mode switching determination process to determine whether or not switching is necessary (whether or not switching is possible) of the operation mode M. When the operation of the fuel cell system 100 starts, the control unit 10 executes the operation mode switching determination process.

[0051] 2, in the operation mode switching determination process, the control unit 10 waits until the water level Lw of the reforming water (amount of reforming water) in the water tank 21 becomes a low water level Lw1 (less than or equal to the first water level threshold T1) (step S101; No). In detail, the control unit 10 waits until it receives information from the first water level sensor 231 indicating that the water level Lw of the reforming water is the low water level Lw1.

[0052] When the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 has reached the low water level Lw1 (the water level Lw is equal to or lower than the first water level threshold) (step S101; Yes), it acquires weather forecast data from the weather forecast data server Sc via the communication unit 9 (step S103). In this embodiment, the control unit 10 acquires temperature data for a predetermined time period (e.g., 24 hours) into the future from the time when the weather forecast data was acquired.

[0053] When the control unit 10 acquires the temperature data, the control unit 10 generates water balance prediction data based on the temperature data and data on past operating results of the fuel cell system 100. The water balance prediction data is data indicating a predicted value of the water balance in the normal operation mode M1 of the fuel cell system 100, and is generated based on past operating results data of the fuel cell system 100 in the normal operation mode M1. More specifically, the water balance prediction data is data corresponding to the temperature Tp indicated by the temperature data, and is generated based on past operating results data of the water balance in the normal operation mode M1 of the fuel cell system 100 that corresponds to the temperature Tp indicated by the temperature data. For example, if the temperature Tp indicated by the temperature data (the temperature Tp at the time the temperature data was acquired) is 30°C, the actual value of the water balance indicated by the operating results data when the past temperature Tp was 30°C (e.g., the water balance is zero, positive, or negative) is used as the predicted value (e.g., the water balance is zero, positive, or negative) to generate the water balance prediction data. When the control unit 10 acquires temperature data for 24 hours (a predetermined period) into the future as temperature data, it generates water balance prediction data corresponding to the acquired 24 hours (a predetermined period). Note that cases where the water balance is established include not only the water balance for a unit time (instantaneous time) but also the case where the accumulated value for a predetermined time is positive. The temperature data and water balance prediction data are stored in the memory unit 101.

[0054] Next, the control unit 10 determines whether or not it is necessary to switch the operation mode M from the normal operation mode M1 to the water recovery operation mode M2 ​​based on the water balance prediction data (step S105). More specifically, the control unit 10 determines whether or not it is necessary to switch the operation mode M by determining whether or not the water balance is established based on the water balance prediction data while the normal operation mode M1 is being executed. Hereinafter, the determination of whether or not it is necessary to switch to the water recovery operation mode M2 ​​while the normal operation mode M1 is being executed is referred to as the first water balance establishment determination.

[0055] In the first water balance establishment determination according to this embodiment, even if the water balance is negative at the time of executing the operation mode switching determination process, the control unit 10 determines that the water balance is established if it can determine from the water balance prediction data that the water balance will recover to zero within the first specified time Hk1 (e.g., six hours) has elapsed. On the other hand, the control unit 10 determines that the water balance is not established if it can determine from the water balance prediction data that the water balance will not recover to zero within the first specified time Hk1 has elapsed. The first specified time Hk1 is a value that is preset by the designer.

[0056] If the control unit 10 determines during execution of the normal operation mode M1 that it is not necessary to switch from the normal operation mode M1 to the water recovery operation mode M2, that is, that the water balance is established (step S105; No), the control unit 10 returns to step S101 without switching the operation mode M to the water recovery operation mode M2, and maintains the normal operation mode M1. For example, as shown in FIG. 3, even if information is received at a first point P1 indicating that the water level Lw of the reforming water in the water tank 21 has reached a low water level Lw1, if the control unit 10 determines that the water balance is established between the first specified time Hk1 and the second point P2 (third point P3 in the example shown in FIG. 3), the control unit 10 determines that it is not necessary to switch from the normal operation mode M1 to the water recovery operation mode M2. Note that the horizontal axis in FIG. 3 indicates time h.

[0057] On the other hand, if the control unit 10 determines that it is necessary to switch from the normal operation mode M1 to the water recovery operation mode M2 ​​while the normal operation mode M1 is being executed, that is, that the water balance is not established (step S105; Yes), the control unit 10 switches the operation mode M from the normal operation mode M1 to the water recovery operation mode M2 ​​(step S107). For example, as shown in Fig. 3, when information is received at the fourth point P4 indicating that the water level Lw of the reforming water in the water tank 21 has reached the low water level Lw1, and it is determined that the water balance is not established until the fifth point P5 at which the first specified time Hk1 has elapsed, the control unit 10 determines that it is necessary to switch from the normal operation mode M1 to the water recovery operation mode M2, and switches the operation mode M to the water recovery operation mode M2.

[0058] While the water recovery operation mode M2 ​​is being executed, the control unit 10 determines whether or not it is necessary to switch the operation mode M from the water recovery operation mode M2 ​​to the normal operation mode M1 (step S109). While the water recovery operation mode M2 ​​is being executed, the control unit 10 determines whether or not it is necessary to switch the operation mode M by determining whether or not the water balance is established. Hereinafter, the determination of whether or not it is necessary to switch to the normal operation mode M1 while the water recovery operation mode M2 ​​is being executed will be referred to as the second water balance establishment determination.

[0059] In the second water balance establishment determination according to this embodiment, a case where the water balance is established means that even if the water balance at the time of executing the operation mode switching determination process is negative, if it can be determined from the water balance prediction data that the water balance will recover to zero within the second specified time Hk2 (for example, 2 hours), the control unit 10 determines that the water balance is not established if it can be determined from the water balance prediction data that the water balance will not recover to zero within the second specified time Hk2.

[0060] The second specified time Hk2 is a value that is set in advance by a designer, and in this embodiment, is set to a value smaller than the first specified time Hk1, although the second specified time Hk2 may also be set to the same value as the first specified time Hk1.

[0061] Specifically, as shown in FIG. 3, if it is determined that the water balance will be established by the sixth point P6 at the fifth point P5 (when the water level Lw of the reforming water in the water tank 21 is at the low water level Lw1) when the second specified time Hk2 has elapsed, the control unit 10 determines that it is necessary (possible) to switch the operation mode M from the water recovery operation mode M2 ​​to the normal operation mode M1.

[0062] When the control unit 10 determines that it is necessary (possible) to switch to the normal operation mode M1 in the water recovery operation mode M2 ​​(step S109; Yes), it switches the operation mode M from the water recovery operation mode M2 ​​to the normal operation mode M1 (step S111) and returns to step S101.

[0063] On the other hand, the control unit 10 determines that it is not necessary (possible) to switch to the normal operation mode M1 in the water recovery operation mode M2 ​​(step S109; No). In other words, unlike the example shown in Figure 3, if it is determined at the fifth point P5 that the water balance will not be established until the sixth point P6 at which the second specified time Hk2 has elapsed, the control unit 10 determines that it is not necessary (possible) to switch the operation mode M to the normal operation mode M1, and maintains the water recovery operation mode M2.

[0064] When maintaining the water recovery operation mode M2, the control unit 10 determines whether the water level Lw of the reforming water in the water tank 21 is the lower limit water level Lw2 (step S113). When the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is not the lower limit water level Lw2 (step S113; No), the control unit 10 returns to step S109.

[0065] On the other hand, when the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is the lower limit water level Lw2 (step S113; Yes), it stops the operation of the fuel cell system 100 (hot module 1) (step S115) and terminates the operation mode switching determination process.

[0066] As described above, according to this embodiment, when the control unit 10 determines that the reforming water level Lw is at the low water level Lw1 (the water volume is equal to or less than the first water volume threshold), it determines whether or not to switch to the operation mode M1 based on the weather forecast data and the water balance prediction data, thereby making it possible to suppress an increase in the number of times the water recovery operation mode M2 ​​is activated and the operation time of the water recovery operation mode M2. As described above, the amount of power generated in the water recovery operation mode M2 ​​is smaller than that in the normal operation mode M1, and therefore, according to this embodiment, it is possible to suppress a decrease in convenience for users.

[0067] Second Embodiment Next, a fuel cell system 100 according to a second embodiment will be described with reference to Figures 4 and 5. The second embodiment differs from the first embodiment in that the water volume measurement unit 23 further includes a third water level sensor 233, and when the liquid level of the reforming water is detected by the third water level sensor 233, the operation mode M is switched to the water recovery operation mode M2 ​​without acquiring air temperature data. Note that detailed description of the same configuration as in the first embodiment will be omitted. Figure 4 is a schematic diagram showing a fuel cell system 100 according to the second embodiment.

[0068] 4, the third water level sensor 233, like the first water level sensor 231 and the second water level sensor 232, measures the water level Lw (water volume) of the reforming water in the water tank 21 by detecting the liquid level of the reforming water. The third water level sensor 233 also measures the water level Lw of the reforming water in the water tank 21, which is set as a third water level threshold T3 (an example of a second water volume threshold). The third water level threshold T3 is set to a value between the first water level threshold T1 and the second water level threshold T2. In other words, the third water level sensor 233 detects the water level Lw of the reforming water between the first water level sensor 231 and the second water level sensor 232.

[0069] In the second embodiment, the water level Lw of the reforming water in the water tank 21 when it is equal to or less than the first water level threshold T1 and exceeds the third water level threshold T3 is referred to as the low water level Lw1, and the water level Lw of the reforming water in the water tank 21 when it is equal to or less than the third water level threshold T3 and exceeds the second water level threshold T2 is referred to as the extremely low water level Lw3. In other words, the third water level sensor 233 outputs information indicating that the water level Lw of the reforming water in the water tank 21 is the extremely low water level Lw3. When the water level Lw of the reforming water in the water tank 21 is the extremely low water level Lw3, the fuel cell system 100 is capable of generating electricity.

[0070] In this embodiment, when the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 has reached the extremely low water level Lw3 (the water level Lw is equal to or lower than the third water level threshold), it switches the operation mode M from the normal operation mode M1 to the water recovery operation mode M2 ​​regardless of the temperature Tp of the installation area. The control unit 10 maintains the operation mode M in the water recovery operation mode M2 ​​while the water level Lw of the reforming water in the water tank 21 is at the extremely low water level Lw3.

[0071] The driving mode switching determination process according to the second embodiment will be described in detail below with reference to Fig. 5. Fig. 5 is a flowchart showing the driving mode switching determination process according to the second embodiment.

[0072] As shown in FIG. 5, in the second embodiment, when the control unit 10 determines that it is not necessary to switch from the normal operation mode M1 to the water recovery operation mode M2, that is, that the water balance is established (step S105; No), it determines whether the water level Lw of the reforming water in the water tank 21 is an extremely low water level Lw3 (less than or equal to the third water level threshold T3) (step S201).

[0073] When the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is not the extremely low water level Lw3 (step S201; No), the control unit 10 returns to step S101 and maintains the operation mode M in the normal operation mode M1.

[0074] On the other hand, when the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is the extremely low water level Lw3 (step S201; Yes), the control unit 10 proceeds to step S107 and switches the operation mode M to the water recovery operation mode M2 ​​(step S107).

[0075] When the control unit 10 switches the operation mode M to the water recovery operation mode M2 ​​(step S107), it determines whether the water level Lw of the reforming water in the water tank 21 is the extremely low water level Lw3 (step S203).

[0076] When the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is not the extremely low water level Lw3 (step S203; No), the control unit 10 proceeds to step S109. On the other hand, when the control unit 10 determines that the water level Lw of the reforming water in the water tank 21 is the extremely low water level Lw3 (step S203; Yes), the control unit 10 proceeds to step S107. Thereafter, the operation mode switching determination process is executed in the same manner as in the first embodiment.

[0077] As described above, according to this embodiment, it is possible to prevent the fuel cell system 100 from shutting down due to a water shortage caused by a continuous decrease in the reforming water level Lw (water amount) due to some environmental factor.

[0078] <Another embodiment> In the above embodiment, a specific example of the configuration of the fuel cell system has been described, but the configuration can be changed as appropriate.

[0079] In the above embodiment, the fuel cell system of the present invention has been described using specific numerical examples, but these numerical values ​​are given for illustrative purposes only and can be changed as appropriate.

[0080] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention.

[0081] (1) The first water balance establishment determination is not limited to the above embodiment, and the control unit 10 may determine that the water balance is established when it determines that the water level Lw will not reach the lower limit water level Lw2 within the first specified time Hk1, and may determine that the water balance is not established when it determines that the water level Lw will reach the lower limit water level Lw2 within the first specified time Hk1. Alternatively, the control unit 10 may determine that the water balance is not established when the temperature Tp does not temporarily fall below a first temperature threshold Tp1 (e.g., 30°C) from the time the temperature data is acquired until the first specified time Hk1 has elapsed, or when the average temperature during the first specified time Hk1 does not fall below the first temperature threshold Tp1. Alternatively, the control unit 10 may determine that the water balance is established when the temperature Tp temporarily falls below the first temperature threshold Tp1 or when the average temperature during the first specified time Hk1 falls below the first temperature threshold Tp1. Similarly, in the second water balance establishment determination, the control unit 10 may determine that the water balance is established if it determines that the water level Lw will recover to the standard water level Lw0 before the second specified time Hk2 has elapsed, and may determine that the water balance is not established if it determines that the water level Lw will not recover to the standard water level Lw0. Alternatively, the control unit 10 may determine that the water balance is not established if the temperature Tp does not temporarily fall below a second temperature threshold Tp2 (e.g., 30°C) from the time the temperature data is acquired until the second specified time Hk2 has elapsed, or if the temperature Tp temporarily falls below the second temperature threshold Tp2. Note that the values ​​of the first temperature threshold Tp1 and the second temperature threshold Tp2 may be the same or different. [Industrial Applicability]

[0082] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0083] 10: Control section 13: Modification section 15: Combustion section 21: Water tank 22: Pump (water supply section) 23:Water amount measurement part 31: Solenoid valve (raw fuel supply adjustment section) 33: Gas blower (raw fuel supply adjustment section) 51: Heat exchanger (condensation recovery section) 100: Fuel cell system C: Cell (fuel cell) M: Operation mode M1: Normal operation mode M2: Water recovery operation mode T1: First water level threshold (first water volume threshold) T3: Third water level threshold (second water volume threshold) Tp:Temperature Lw: Water level (water amount)

Claims

1. a reforming unit that generates fuel gas by steam reforming a raw fuel; a fuel cell that generates electricity based on the fuel gas and an oxidant gas; a combustion section that uses the off-gas discharged from the fuel cell as fuel; a condensation recovery section that condenses and recovers water contained in the combustion exhaust gas discharged from the combustion section; a water tank that stores the water recovered in the condensation recovery unit; a water volume measuring unit that measures the volume of water stored in the water tank; a water supply unit that supplies water used in the steam reforming from the water tank to the reforming unit; a control unit configured to be able to switch between a normal operation mode in which the device is operated in a normal operation mode and a water recovery operation mode in which the device is operated in an operation mode in which a larger amount of water is recovered than in the normal operation mode; Equipped with The control unit determines whether the water volume measured by the water volume measuring unit is less than or equal to a first water volume threshold, and if it determines that the water volume is less than or equal to the first water volume threshold, determines whether or not the operating mode needs to be switched from the normal operating mode to the water recovery operating mode based on weather forecast data indicating future weather in the installation area where the water tank is installed and water balance prediction data generated based on data on past operating performance in the normal operating mode.

2. a raw fuel supply adjusting unit that adjusts the amount of the raw fuel supplied to the reforming unit; 2. The fuel cell system according to claim 1, wherein the control unit controls the operation of the raw fuel supply adjustment unit in the water recovery operation mode to reduce the amount of the raw fuel supplied to the reforming unit compared to the normal operation mode.

3. the weather forecast data includes temperature data indicating the temperature of the installation area, 3. The fuel cell system of claim 1, wherein the control unit determines whether a water balance is established based on the water balance prediction data corresponding to the temperature data for a predetermined period of time, by determining whether the amount of water condensed by the condensation recovery unit and supplied to the water tank during the predetermined period of time is greater than or equal to the amount of water supplied from the water tank to the reforming unit, and determines whether the operating mode needs to be switched based on whether the water balance is established.

4. 4. The fuel cell system of claim 3, wherein the control unit switches the operation mode from the normal operation mode to the water recovery operation mode when it determines that the water balance is not established during execution of the normal operation mode, and maintains the operation mode in the normal operation mode when it determines that the water balance is established.

5. 5. The fuel cell system of claim 4, wherein the control unit switches the operating mode from the water recovery operating mode to the normal operating mode when it determines that the water balance is established during execution of the water recovery operating mode, and maintains the operating mode in the water recovery operating mode when it determines that the water balance is not established.

6. the control unit determines whether the water volume is equal to or less than a second water volume threshold value that is set to a value smaller than the first water volume threshold value; When it is determined that the water volume is equal to or less than the second water volume threshold, the operation mode is switched from the normal operation mode to the water recovery operation mode regardless of the weather forecast data; The fuel cell system according to claim 1 , wherein the operation mode is maintained in the water recovery operation mode while the water amount is equal to or less than the second water amount threshold.

Images