Fuel cell system

Abstract

To provide a fuel cell system capable of effectively utilizing hot water with a compact configuration.SOLUTION: Each of a first fuel cell unit arranged at a first dwelling unit and a first arranged at a second dwelling unit comprises a hot water storage tank T for storing hot water heated using waste-heat of a fuel cell N, a temperature sensor S for detecting a temperature of hot water in the hot water storage tank T, a controlling unit H4 for controlling supply / discharge of hot water in the hot water storage tank T, and a determination unit H2. The controlling units H4 of the first fuel cell unit and the second fuel cell unit are configured to execute accommodation control for supplying hot water in the first hot water storage tank T to the second hot water storage tank T through a hot water pipe 31.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] For example, in the fuel cell system disclosed in Patent Document 1, the exhaust heat from the fuel cell is stored in hot water in a hot water storage tank, and the hot water is used for hot water supply and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6647030 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when demand for hot water decreases, for example, in the summer, the hot water storage tank may have excess hot water, filling up with high-temperature water and potentially causing problems such as being unable to cool the fuel cell. In this case, one possible solution is to drain the hot water stored in the hot water storage tank while refilling it with cold water in order to release the fuel cell's waste heat, but this configuration wastes hot water. Furthermore, installing a large radiator to release the fuel cell's waste heat would make it difficult for fuel cell systems to be widely used in residential buildings and other spaces where space saving is required.

[0005] An object of the present invention is to provide a fuel cell system that has a compact configuration and can effectively utilize hot and cold water. [Means for solving the problem]

[0006] The fuel cell system of the present invention comprises a first fuel cell unit disposed in a first dwelling unit and having a first fuel cell that generates electricity by supplying hydrogen, a first hot water storage tank that stores hot water heated by exhaust heat from the first fuel cell, a first temperature sensor that detects the temperature of the hot water in the first hot water storage tank, a first control unit that controls the supply and discharge of hot water in the first hot water storage tank, and a first determination unit that determines whether or not it is necessary to release the heat in the first hot water storage tank based on the temperature detected by the first temperature sensor; and a second fuel cell unit disposed in a second dwelling unit and having a second fuel cell that generates electricity by supplying hydrogen, a second hot water storage tank that stores hot water heated by exhaust heat from the second fuel cell, a second temperature sensor that detects the temperature of the hot water in the second hot water storage tank, a second control unit that controls the supply and discharge of hot water in the second hot water storage tank, and a first determination unit that determines whether or not it is necessary to release the heat in the second hot water storage tank based on the temperature detected by the second temperature sensor. The system is equipped with a second fuel cell unit having a second judgment unit that judges whether there is an excess in the first hot water storage tank to meet the demand in the second dwelling unit, and a hot water supply pipe that connects the first hot water storage tank and the second hot water storage tank, wherein the first control unit switches the control mode to a heat release mode when the first judgment unit determines that the heat in the first hot water storage tank needs to be released, and the second control unit switches the control mode to a heat reception mode when the second judgment unit determines that there is an excess in the heat in the second hot water storage tank to meet the demand in the second dwelling unit, and when the first control unit is in the heat release mode and the second control unit is in the heat reception mode, the first control unit and the second control unit are configured to perform interchange control to supply hot water in the first hot water storage tank to the second hot water storage tank through the hot water supply pipe.

[0007] According to the present invention, a first hot water storage tank provided in a first dwelling unit and a second hot water storage tank provided in a second dwelling unit are connected via a hot water pipe. The system is configured to allow hot water to be exchanged between the first and second hot water storage tanks. Therefore, even if the first hot water storage tank becomes full and it becomes necessary to release the hot water from the first hot water storage tank, the hot water can be shared with the second hot water storage tank. This enables a configuration that makes effective use of hot water without the need to install a large radiator or the like to release the exhaust heat from the first fuel cell. As a result, a fuel cell system that can make effective use of hot water with a compact configuration is realized.

[0008] In the present invention, it is preferable that the first fuel cell unit is provided with a first prediction unit that calculates an estimated consumption of heat in the first hot water storage tank within a predetermined time period, and the first judgment unit is configured to determine whether or not it is necessary to release the heat in the first hot water storage tank based on the detected temperature of the first temperature sensor, the amount of heat received by the exhaust heat of the first fuel cell, and the estimated consumption calculated by the first prediction unit.

[0009] With this configuration, the estimated consumption amount predicted to be consumed in the first dwelling unit is calculated, and therefore the first determination unit can accurately determine whether or not the heat amount in the first hot water storage tank needs to be released.

[0010] In the present invention, it is preferable that the second fuel cell unit is provided with a second prediction unit that calculates an estimated consumption of heat in the second hot water storage tank within a predetermined time period, and the second judgment unit is configured to determine whether the heat in the second hot water storage tank is sufficient to meet the demand in the second dwelling unit based on the temperature detected by the second temperature sensor, the amount of heat received by the exhaust heat of the second fuel cell, and the estimated consumption calculated by the second prediction unit.

[0011] With this configuration, the estimated consumption amount predicted to be consumed in the second dwelling unit is calculated, so the second determination unit can accurately determine whether there is a surplus of heat in the second hot water storage tank, and hot water can be flexibly supplied from the first hot water storage tank.

[0012] In the present invention, it is preferable that the first fuel cell unit is provided with a first drain valve for draining hot water from the first hot water storage tank, and when the first control unit is in the heat release mode and the second control unit is not in the heat receiving mode, the first control unit is configured to execute first drain control for opening the first drain valve.

[0013] This configuration ensures that the exhaust heat of the first fuel cell can be released even when the second control unit is not in the heat receiving mode.Furthermore, the exhaust heat of the first fuel cell can be released without the need to install a large radiator or the like for releasing the exhaust heat of the first fuel cell.

[0014] In the present invention, it is preferable that the second fuel cell unit is provided with a second drain valve for draining hot water from the second hot water storage tank, and when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode, the second control unit is configured to execute second drain control for opening the second drain valve in the interchange control.

[0015] With this configuration, even if the second hot water storage tank is full of water, it is possible to drain the water from the second hot water storage tank and receive hot water from the first hot water storage tank.

[0016] In the present invention, a first opening / closing valve for opening and closing the flow path between the first hot water storage tank and the hot water supply pipe, and a second opening / closing valve for opening and closing the flow path between the second hot water storage tank and the hot water supply pipe are provided, and it is preferable that the first control unit is configured to execute a first valve opening control for opening the first opening / closing valve in the interchange control when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode, and that the second control unit is configured to execute a second valve opening control for opening the second opening / closing valve in the interchange control when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode.

[0017] In this configuration, the first and second control units operate the on-off valves to connect the first and second hot water storage tanks via a hot water pipe. This allows the hot water stored in the hot water storage tank to be used more effectively in each dwelling unit, and makes it possible to exchange hot water between the first and second dwelling units in the amount needed when needed, compared to a configuration in which the first and second on-off valves are not provided.

[0018] In the present invention, a third discharge valve that discharges water in the hot water pipe and a third temperature sensor that detects the water temperature in the hot water pipe are provided, and at least one of the first control unit and the second control unit, when executing the interchange control, executes a first pre-interchange control that opens the third discharge valve in response to the water temperature in the hot water pipe detected by the third temperature sensor being lower than a predetermined first threshold, and closes the third discharge valve in response to the water temperature in the hot water pipe detected by the third temperature sensor being equal to or higher than a second threshold that is set higher than the first threshold after executing the first pre-interchange control. It is preferable that the first control unit is configured to execute a second pre-accommodation control, and that when the water temperature in the hot water pipe detected by the third temperature sensor is below the first threshold value when executing the accommodation control, the first control unit is configured to execute the first valve opening control in response to the execution of the first pre-accommodation control, and that when the water temperature in the hot water pipe detected by the third temperature sensor after the first control unit executes the first pre-accommodation control is above the second threshold value when executing the accommodation control, the second control unit is configured to execute the second valve opening control in response to the execution of the second pre-accommodation control.

[0019] With this configuration, even if the water in the hot water supply pipe cools over time, the cold water in the hot water supply pipe is discharged. This prevents the cold water in the hot water supply pipe from entering the second hot water storage tank, and ensures that hot water from the first hot water storage tank is supplied to the second hot water storage tank.

[0020] In the present invention, it is preferable that the hot water in the first hot water storage tank is sucked in from the bottom of the first hot water storage tank, heated by the exhaust heat of the first fuel cell, and then circulates through a hot water flow circuit that returns it to the top of the first hot water storage tank, and that the hot water in the second hot water storage tank is sucked in from the bottom of the second hot water storage tank, heated by the exhaust heat of the second fuel cell, and then circulates through a hot water flow circuit that returns it to the top of the second hot water storage tank, and that an interchange path is connected between the top of the first hot water storage tank and the hot water supply pipe, and that an interchange path is connected between the top of the second hot water storage tank and the hot water supply pipe.

[0021] With this configuration, hot water heated by the exhaust heat of the fuel cell accumulates in the upper part of the hot water storage tank, and high-temperature hot water is efficiently supplied from the first hot water storage tank to the second hot water storage tank. In addition, new low-temperature tap water or the like is more easily supplied to the bottom of the first hot water storage tank, and the fuel cell is efficiently cooled by the low-temperature tap water or the like. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a fuel cell system installed in each dwelling unit and a hot water pipe connected to the hot water storage tank. [Figure 2] FIG. 1 is a block diagram showing a fuel cell system. [Figure 3] FIG. 10 is a flowchart showing determination control and the like for performing interchange control. [Figure 4] FIG. 10 is a diagram showing the estimated amount of heat consumed per day in a dwelling unit. [Figure 5] FIG. 10 is a diagram illustrating a process of interchange control. [Figure 6] FIG. 10 is a diagram showing how cold water remaining in the hot water pipe is drained. [Figure 7] A diagram showing the transfer of hot water from the first hot water storage tank to the second hot water storage tank. [Figure 8] A diagram of another embodiment showing the transfer of hot water from the first hot water storage tank to the second hot water storage tank using a pump. DETAILED DESCRIPTION OF THE INVENTION

[0023] [Overall configuration of fuel cell unit] An embodiment of a fuel cell unit 1 of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a fuel cell unit 1 is installed in each dwelling unit of an apartment building. Each fuel cell unit 1 is equipped with a power generation module M (see FIG. 2) and a hot water storage tank T. Waste heat is generated as the fuel cell N in the power generation module M generates electricity, and the hot water storage tank T stores the waste heat from the fuel cell N in hot water. A hot water pipe 31 extends across each dwelling unit. The hot water pipe 31 is connected to the hot water storage tank T of each dwelling unit via an interchange passage 30. This allows hot water to be interchanged between each dwelling unit.

[0024] As shown in FIG. 2, the fuel cell unit 1 is equipped with a power generation module M and a hot water storage tank T. The power generation module M is a module centered around a fuel cell N, which generates electricity by supplying hydrogen. High-temperature heat is emitted from the fuel cell N. Therefore, hot water is heated by the heat exhausted from the fuel cell N in a waste heat recovery heat exchanger K, and the hot water is stored in the hot water storage tank T. The hot water stored in the hot water storage tank T is supplied as hot water to the kitchen, bath, sink, etc. in the dwelling. The hot water stored in the hot water storage tank T is also used as a heat source for, for example, a heating terminal D (for example, a floor heating panel, a bath reheating function, a bathroom dryer, etc.).

[0025] As shown in FIG. 2, a power supply line 2 to a power load 100, a power receiving line 4A from a power source 4 such as an electric power company, and a power transmission line 5 from a fuel cell N are connected to an indoor distribution panel 3.

[0026] The fuel cell N of this embodiment is a polymer electrolyte fuel cell, and is configured to generate electricity by using hydrogen as fuel and receiving a supply of oxygen. The hydrogen is supplied from a hydrogen supply source G. Note that the fuel cell N may also be configured to receive a raw material gas such as city gas from the hydrogen supply source G, and to generate hydrogen by reforming the raw material gas in a reformer.

[0027] A power conversion unit 6 is provided midway along the power transmission line 5 from the fuel cell N. The power conversion unit 6 includes a grid-connected inverter and the like, and adjusts the power generated by the fuel cell N to the same voltage and frequency as the power supplied from the power source 4. Therefore, the power from the power source 4 and the power generated by the fuel cell N are supplied to the power load 100.

[0028] The power generation module M is provided with a waste heat recovery heat exchanger K. The waste heat recovery heat exchanger K recovers waste heat from the fuel cell N. The hot water heated by the waste heat recovery heat exchanger K forms a temperature stratification of the hot water in the hot water storage tank T.

[0029] The fuel cell unit 1 of this embodiment is provided with a control unit H4. The control unit H4 controls the overall control system of the fuel cell unit 1, including the operation of the fuel cell N. A remote control R is connected to the control unit H4. The remote controls R include a power generation remote control R1 and a temperature control remote control R2. The power generation remote control R1 issues commands to start and stop the operation of the fuel cell N. The temperature control remote control R2 issues various commands, such as commands to start and stop floor heating operation, setting the hot water target temperature, and commands to supply hot water to the bath. For this reason, the control unit H4 is configured to control the operation of the fuel cell unit 1 based on commands from the remote control R.

[0030] [Fuel cell cooling configuration] A fuel cell N has a plurality of cells C stacked one on top of the other. A solid polymer electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode is formed in each cell C. As the fuel cell N generates electricity, the cells C generate heat. To cool the cells C, a cooling unit 7 is disposed between two adjacent cells C among the plurality of cells C. The cooling unit 7 has a cooling water flow path. A cooling water circulation path 8 is connected to each of the inlet and outlet of the cooling water flow path. The cooling water flow path is made of a conductive and porous material, such as a carbon plate.

[0031] The cooling water circulation path 8 is provided with a cooling water circulation pump 10 that circulates the cooling water, a water tank 11 that stores the cooling water, a water treatment device 12, and an exhaust heat recovery heat exchanger K. When the cooling water flows through the cooling water flow path of the cooling unit 7, the cooling water is supplied to the solid polymer electrolyte membrane through the anode. This promotes heat exchange between the cooling water and the solid polymer electrolyte membrane, and the temperature of the cell C is cooled to an appropriate temperature (e.g., 80°C).

[0032] In the cooling water circulation path 8, a waste heat recovery heat exchanger K is provided downstream of the cooling section 7. The cooling water whose temperature has increased by passing through the cooling section 7 flows into the waste heat recovery heat exchanger K. In other words, the heat of the cells C recovered by the cooling section 7 is recovered (supplied) by the waste heat recovery heat exchanger K as waste heat of the fuel cell N.

[0033] A water treatment device 12 is provided downstream of the water tank 11 in the cooling water circulation path 8. The cooling water supplied from the water tank 11 may contain electrolytes, impurities that are not dissolved in water, and the like. Therefore, the cooling water supplied from the water tank 11 is purified by the water treatment device 12. The water treatment device 12 is provided with, for example, an adsorbent capable of adsorbing organic matter and the like present in the cooling water, and an ion exchange resin capable of removing ions dissolved in the cooling water.

[0034] [Configuration of hot water storage in hot water storage tank] As described above, the exhaust heat of the fuel cell N is recovered (supplied) by the exhaust heat recovery heat exchanger K. The recovered exhaust heat of the fuel cell N is stored in the hot water in the hot water storage tank T. As shown in FIG. 2, a hot water flow circulation path 13 is connected to each of the bottom and top of the hot water storage tank T. A heat storage circulation pump 14 and an exhaust heat recovery heat exchanger K are provided midway along the hot water flow circulation path 13. The hot water flow circulation path 13 has an outgoing path 13a that connects the bottom of the hot water storage tank T and the exhaust heat recovery heat exchanger K, and a returning path 13b that connects the exhaust heat recovery heat exchanger K and the top of the hot water storage tank T. The heat storage circulation pump 14 is provided on the outgoing path 13a.

[0035] Hot water is drawn from the bottom of the hot water storage tank T into the outgoing path 13a by the heat storage circulation pump 14, and the hot water is returned to the top of the hot water storage tank T via the exhaust heat recovery heat exchanger K. In the exhaust heat recovery heat exchanger K, the cooling water in the cooling water circulation path 8 is cooled, and the hot water in the hot water flow circulation path 13 is heated. In other words, the hot water in the hot water storage tank T is drawn from the bottom of the hot water storage tank T, heated by the exhaust heat of the fuel cell N, and then circulates through the hot water flow circulation path 13, returning the hot water to the top of the hot water storage tank T. As a result, temperature stratification is formed inside the hot water storage tank T, with the temperature increasing towards the top.

[0036] A cold water side sensor 15 is provided on the outgoing line 13a upstream of the heat storage circulation pump 14. The cold water side sensor 15 detects the temperature of hot water sucked from the bottom of the hot water storage tank T. A hot water side sensor 16 is provided on the return line 13b. The hot water side sensor 16 detects the temperature of hot water heated in the exhaust heat recovery heat exchanger K.

[0037] The temperature detected by the hot water side sensor 16 is the temperature of the high temperature layer in the temperature stratification inside the hot water storage tank T. Using the temperature detected by the cold water side sensor 15 as feedforward information, the control unit H4 controls the rotation speed of the heat storage circulation pump 14 so that the temperature detected by the hot water side sensor 16 becomes the target temperature (e.g., 60°C). Note that different target temperatures may be set automatically depending on the season, such as summer, winter, or intermediate season. Alternatively, the user may manually set the target temperature by operating the remote control R.

[0038] A hot water outlet passage 17 is connected to the top of the hot water storage tank T. The hot water stored in the hot water storage tank T is supplied through the hot water outlet passage 17 to hot water consumption points (kitchen, sink, bath, etc.) such as a hot water tap 18.

[0039] A water supply passage 19 is connected to the bottom of the hot water storage tank T. The water supply passage 19 is a water supply source such as a water supply system. When hot water stored in the hot water storage tank T is discharged into the hot water outlet passage 17, water is supplied from the water supply passage 19 to the bottom of the hot water storage tank T. At this time, the flow of hot water through the hot water outlet passage 17 to the hot water tap 18, etc. is achieved using the water supply pressure in the water supply passage 19. In other words, when the hot water tap 18, etc. is opened, the hot water in the hot water storage tank T is pushed by the water supply pressure in the water supply passage 19 into the hot water outlet passage 17 connected to the top of the hot water storage tank T, and is discharged to the hot water tap 18, etc.

[0040] In this embodiment, an auxiliary heat source unit 20 is provided in the hot water outlet path 17. When the temperature of the hot water discharged from the hot water storage tank T is lower than the required temperature of the hot water consumption point, the hot water is heated by the auxiliary heat source unit 20.

[0041] The hot water storage tank T is equipped with temperature sensors S for detecting the temperature of the stored hot water, including an upper temperature sensor S1, an upper intermediate temperature sensor S2, an upper / lower center temperature sensor S3, a lower intermediate temperature sensor S4, and a lower temperature sensor S5. The upper temperature sensor S1 is provided at the top of the hot water storage tank T. The upper intermediate temperature sensor S2 is provided in an upper intermediate portion between the top of the hot water storage tank T and the upper / lower center of the hot water storage tank T. The upper / lower center temperature sensor S3 is provided in the upper / lower center of the hot water storage tank T. The lower intermediate temperature sensor S4 is provided in a lower intermediate portion between the upper / lower center of the hot water storage tank T and the bottom of the hot water storage tank T. The lower temperature sensor S5 is provided at the bottom of the hot water storage tank T. The lower temperature sensor S5 is located above the bottom of the hot water storage tank T. The control unit H4 can detect the temperature of the hot water in the hot water storage tank T across both the upper and lower portions based on the detection information of the temperature sensors S. The temperature sensor S corresponds to the "first temperature sensor" and the "second temperature sensor."

[0042] A hot water consumption circuit 24 is connected to both the top and bottom of the hot water storage tank T. A consumption circulation pump 25 and a heat dissipation heat exchanger 23 are provided midway along the hot water consumption circuit 24. The hot water consumption circuit 24 has a hot water supply path 24a that connects the top of the hot water storage tank T to the heat dissipation heat exchanger 23, and a return path 24b that connects the heat dissipation heat exchanger 23 to the bottom of the hot water storage tank T. A consumption circulation pump 25 is provided in the hot water supply path 24a. When the consumption circulation pump 25 is driven, hot water is sucked from the top of the hot water storage tank T into the hot water supply path 24a, and the hot water is returned to the bottom of the hot water storage tank T via the heat dissipation heat exchanger 23.

[0043] A heat medium circulation path 26 is connected to the heat dissipation heat exchanger 23. A heat medium circulation pump 27 is provided midway along the heat medium circulation path 26. The heat medium circulates between the heat dissipation heat exchanger 23 and the heating terminal D through the heat medium circulation path 26. In the heat dissipation heat exchanger 23, the hot water in the hot water storage tank T is cooled, and the heat medium in the heat medium circulation path 26 is heated.

[0044] A flow rate sensor 28 is provided in the hot water supply path 24a. A return temperature detection sensor 29 is provided in the return path 24b. The flow rate sensor 28 detects the flow rate (flow rate per unit time) of hot water flowing through the hot water consumption circuit 24. The return temperature detection sensor 29 detects the temperature of the hot water flowing through the return path 24b.

[0045] The control unit H4 is configured to execute a hot water consumption process that controls the operation of the consumption circulation pump 25 in a manner that circulates hot water at a set target flow rate through the hot water consumption circuit 24, and when executing the hot water consumption process, to execute a heating circulation process that circulates the heat medium through the heat medium circulation path 26.

[0046] When floor heating, bath reheating, bathroom heating, etc. are operated, the control unit H4 operates the consumption circulation pump 25 and heat medium circulation pump 27 of the heating terminal D. The control unit H4 also controls the operation (rotation speed) of the consumption circulation pump 25 based on the detection result of the flow rate sensor 28 in order to circulate hot water at a set target flow rate through the hot water consumption circuit 24. This consumes the heat of the hot water stored in the hot water storage tank T.

[0047] A drainage channel 21 is connected to the center of the top and bottom of the hot water storage tank T. A drainage valve 22 for opening and closing the drainage channel 21 is provided in the drainage channel 21. The drainage valve 22 drains hot water from the hot water storage tank T.

[0048] [Configuration for supplying hot water from a hot water storage tank to other dwelling units] As described above, the exhaust heat of the fuel cell N is stored in the hot water in the hot water storage tank T, and the hot water in the hot water storage tank T is used to supply hot water and as a heat source for the heating terminal D. However, if the fuel cell N continues to operate and the hot water supply and heating terminal D are not used much, not only the hot water at the top of the hot water storage tank T but also the hot water at the bottom of the hot water storage tank T will become hot. If the hot water at the bottom of the hot water storage tank T becomes hot, this hot water will flow into the exhaust heat recovery heat exchanger K, making it impossible to cool the cooling water in the cooling water circulation path 8. As a result, the cells C of the fuel cell N will not be able to be properly cooled, which could lead to problems such as breakdown of the fuel cell N. This problem becomes particularly apparent in the summer when demand for hot water is low.

[0049] One possible solution to this problem is to install a radiator on the outgoing path 13a of the hot and cold water circulation path 13. However, the radiator tends to occupy a large area, making it difficult to adopt in homes where space saving is required.

[0050] As another means for solving the above problem, this embodiment is configured to allow hot water in the hot water storage tank T to be shared with other dwelling units. As shown in Figures 1 and 2, an interchange passage 30 is connected to the top of the hot water storage tank T, and the interchange passage 30 is connected to a hot water supply pipe 31. In other words, each hot water storage tank T is connected to the hot water supply pipe 31 via the interchange passage 30. An open / close valve 32 is provided midway along the interchange passage 30.

[0051] A discharge path 34 for discharging cooled hot water is connected to the hot water pipe 31 near each of the accommodation passages 30. A hot water pipe drain valve 35 is provided in the discharge path 34. A hot water temperature sensor 33 is also provided at the branch point of the hot water pipe 31 with each of the discharge paths 34. Details will be described later, but when the hot water temperature detected by the hot water temperature sensor 33 falls below a predetermined first threshold value (see Figure 5), the hot water pipe drain valve 35 opens and the cooled hot water in the hot water pipe 31 is discharged from the discharge path 34.

[0052] Referring to FIG. 3, when the lower temperature sensor S5 detects a temperature equal to or higher than a predetermined temperature (e.g., 40°C or higher) (Step #01: Yes), the prediction unit H1 calculates an estimated amount of heat consumed in the hot water tank T within a first preset time period (e.g., within 12 hours). The memory unit H3 stores, for example, the amount of hot water supplied for the past three months, the time periods during which hot water was supplied, the amount of heat consumed by the heating terminal D, and the time periods during which the heating terminal D was used. The prediction unit H1 calculates an estimated amount of heat consumed in the dwelling unit within the first set time period based on the past records stored in the memory unit H3 (Step #02). FIG. 4 shows the amount of hot water supplied to the bath, the estimated amount of heat consumed by the heating terminal D per day, and other estimated consumption amounts for each time period. Note that FIG. 4 may also show the amount of hot water supplied to the bath, the usage history of the heating terminal D, and so on, stored in the memory unit H3. Furthermore, the prediction unit H1 calculates the total amount of heat that will be applied to the hot water in the hot water storage tank T by the exhaust heat from the fuel cell N within the first set time (step #03). The prediction unit H1 corresponds to the "first prediction unit" and the "second prediction unit."

[0053] The determination unit H2 (first determination unit) determines whether or not it is necessary to release the heat in the hot water storage tank T (first hot water storage tank T1) based on the temperature detected by the temperature sensor S (first temperature sensor), the total amount of heat (amount of heat received) due to the exhaust heat of the fuel cell N, and the estimated consumption calculated by the prediction unit H1 (step #04). If the heating terminal D is in use and it is close to time to supply hot water to the kitchen or bath, the determination in step #04 may be No. Even if the heating terminal D is scheduled to be used and hot water is scheduled to be supplied by the hot water supply, the determination in step #04 may be Yes if the temperature detected by the lower temperature sensor S5 is high or the total amount of heat is greater than the estimated consumption by more than a predetermined threshold.

[0054] If the determination in step #04 is No, the control mode of the control unit H4 becomes normal mode (step #05). Then, the determination unit H2 determines whether hot water has been used in the dwelling unit in accordance with the estimated consumption amount (step #06). Specifically, the determination unit H2 determines whether the actual heat consumption amount based on the use of the heating terminal D and the actual heat consumption amount based on the hot water output amount from the hot water storage tank T are within a preset error range for the estimated consumption amount. If the determination in step #06 is Yes, the control unit H4 continues control based on normal mode.

[0055] If the heat in the hot water storage tank T needs to be released (step #04: Yes), or if the hot water in the dwelling unit is not being used in accordance with the estimated consumption (step #06: No), the control mode of the control unit H4 becomes the heat release mode (step #07). At this time, the control unit H4 transmits information indicating that the control mode is the heat release mode to the control units H4 of the fuel cell units 1 of the other dwelling units.

[0056] If the control mode of the controller H4 is the heat release mode, the controller H4 determines whether the controller H4 of the fuel cell unit 1 in the other dwelling unit is in the heat receiving mode (step #08). In other words, in step #08, the controller H4 determines whether information indicating that the control mode is the heat receiving mode has been received from the controller H4 of the fuel cell unit 1 in the other dwelling unit.

[0057] If the determination in step #08 is Yes, the control unit H4 executes control to open the on-off valve 32 of the accommodation passage 30, and supplies hot water to the hot water storage tank T of the fuel cell unit 1 in the other dwelling unit (step #09). If the determination in step #08 is No, the control unit H4 executes control to open the drain valve 22 of the drain passage 21 (step #10). As a result, high-temperature hot water is drained from the hot water storage tank T to the outside. By the control of step #09 or step #10, low-temperature water is replenished from the water supply passage 19 to the bottom of the hot water storage tank T. This allows the low-temperature water to flow into the exhaust heat recovery heat exchanger K, allowing the cells C of the fuel cell N to be appropriately cooled. In other words, when the control unit H4 (first control unit) in at least one fuel cell unit 1 (first fuel cell unit arranged in the first dwelling) among the multiple fuel cell units 1 shown in Figure 1 is in heat dissipation mode and the control unit H4 (second control unit) in the other fuel cell unit 1 (second fuel cell unit arranged in the second dwelling) is not in heat reception mode, the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is configured to perform first drainage control to open the drainage valve 22 (first drainage valve).

[0058] If the temperature detected by the lower temperature sensor S5 is below a preset temperature (e.g., 40°C or higher) (Step #01: No), the prediction unit H1 calculates an estimated amount of heat consumption in the hot water storage tank T within a preset second time period (e.g., within two hours). In other words, the prediction unit H1 calculates an estimated amount of heat consumption in the dwelling unit within the second time period based on past performance data stored in the memory unit H3 (Step #11). The prediction unit H1 also calculates the total amount of heat that will be used to heat the hot water in the hot water storage tank T by the exhaust heat from the fuel cell N within the second time period (Step #12).

[0059] The determination unit H2 (second determination unit) determines whether the amount of heat in the hot water storage tank T (second hot water storage tank T2) is sufficient to meet the demand for heat in the dwelling unit (second dwelling unit) based on the temperature detected by the temperature sensor S (second temperature sensor), the total amount of heat (amount of heat received) generated by the exhaust heat of the fuel cell N, and the estimated consumption calculated by the prediction unit H1 (second prediction unit) (step #13). If the detected temperature of at least one of the upper temperature sensor S1, the upper middle temperature sensor S2, the upper / lower middle temperature sensor S3, and the lower middle temperature sensor S4 is lower than the average value of past detected temperatures stored in the memory unit H3 and falls outside a preset range, the determination in step #13 may be No. Furthermore, if the amount of hot water discharged from the hot water storage tank T or the actual heat consumption at the heating terminal D on that day is greater than the amount of heat available for heating using the exhaust heat of the fuel cell N, the determination in step #13 will be No.

[0060] If there is a surplus of heat in the hot water tank T (step #13: Yes), the control mode of the control unit H4 becomes the normal mode (step #14), and the control unit H4 continues the control based on the normal mode.

[0061] If there is no excess heat in the hot water tank T (step #13: No), the control mode of the control unit H4 becomes the heat receiving mode (step #15). At this time, the control unit H4 transmits information indicating that the control mode is the heat receiving mode to the control units H4 of the fuel cell units 1 of the other dwelling units.

[0062] If the control mode of the controller H4 is the heat receiving mode, the controller H4 determines whether the controller H4 of the fuel cell unit 1 in the other dwelling unit is in the heat releasing mode (step #16). In other words, in step #16, the controller H4 determines whether information indicating that the control mode is the heat releasing mode has been received from the controller H4 of the fuel cell unit 1 in the other dwelling unit.

[0063] If the judgment in step #16 is Yes, the control unit H4 executes control to open the opening / closing valve 32 of the interchange passage 30, and receives hot water from the hot water storage tank T of the fuel cell unit 1 in another dwelling unit to the hot water storage tank T in the dwelling unit itself (step #17).

[0064] In this way, when hot water is supplied from the hot water storage tank T (first hot water storage tank T1) in one fuel cell unit 1 to the hot water storage tank T (second hot water storage tank T2) in the other fuel cell unit 1, the control unit H4 (first control unit) in one fuel cell unit 1 and the control unit H4 (second control unit) in the other fuel cell unit 1 are each configured to perform interchange control to supply the hot water in the first hot water storage tank T1 to the second hot water storage tank T2 through the hot water supply pipe 31. One fuel cell unit 1 corresponds to the "first fuel cell unit." The other fuel cell unit 1 corresponds to the "second fuel cell unit."

[0065] [Control performed during interchange control] When hot water is supplied from the first hot water storage tank T1 to the second hot water storage tank T2, the hot water passes through the hot water supply pipe 31. Specifically, as shown in Fig. 5, first valve opening control and second valve opening control are executed in the interchange control.

[0066] Although the outer surface of the hot water supply pipe 31 is covered with a heat insulating material, the hot water in the hot water supply pipe 31 cools over time. If hot water is supplied from the first hot water storage tank T1 to the second hot water storage tank T2 in this state, cold water in the hot water supply pipe 31 will flow into the second hot water storage tank T2, and the second hot water storage tank T2, which is supposed to receive the hot water, may not receive enough heat. To avoid this inconvenience, in this embodiment, the cold water in the hot water supply pipe 31 is drained before hot water is supplied from the first hot water storage tank T1 to the second hot water storage tank T2. Specifically, as shown in FIG. 5, when the interchange control is executed, a first pre-interchange control and a second pre-interchange control are executed. Note that the first pre-interchange control and the second pre-interchange control may be controls that are included in the interchange control, or may not be controls that are included in the interchange control.

[0067] As shown in Figure 1, each hot water storage tank T is connected to a hot water pipe 31 via an interchange passage 30. A discharge passage 34 is connected to the hot water pipe 31 near each interchange passage 30. A hot water pipe drain valve 35 is provided in the discharge passage 34. In addition, a hot water temperature sensor 33 is provided at the branch point of the hot water pipe 31 with each discharge passage 34.

[0068] Explaining based on the flowchart of Figure 5, it is determined whether the hot water temperature sensor 33 adjacent to the second hot water storage tank T2 detects a temperature equal to or higher than a preset first threshold value (e.g., equal to or higher than 50°C) (step #21). The determination in step #21 may be made by the control unit H4 (first control unit) in the fuel cell unit 1 (first fuel cell unit) on the heat dissipation side, or by the control unit H4 (second control unit) in the fuel cell unit 1 (second fuel cell unit) on the heat reception side.

[0069] If the detected temperature of the hot water temperature sensor 33 adjacent to the second hot water storage tank T2 is equal to or higher than a preset temperature (step #21: Yes), it is assumed that the temperature of the hot water in the hot water supply pipe 31 is sufficiently warm and there is no risk of cold water flowing into the second hot water storage tank T2. Therefore, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side closes the water supply valve 9 of the second hot water storage tank T2 (step #22). Then, the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipating side opens the on-off valve 32 (first on-off valve 32A) adjacent to the first hot water storage tank T1 (step #23).

[0070] That is, when the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is in heat dissipation mode and the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is in heat receiving mode, the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is configured to execute first valve opening control to open the first opening / closing valve 32A adjacent to the first hot water storage tank T1 in interchange control.

[0071] The control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side opens the on-off valve 32 (second on-off valve 32B) adjacent to the second hot water storage tank T2 (step #24).

[0072] That is, when the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is in heat dissipation mode and the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is in heat receiving mode, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is configured to execute second valve opening control to open the second opening / closing valve 32B adjacent to the second hot water storage tank T2 in interchange control.

[0073] Then, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side opens the drain valve 22 of the second hot water storage tank T2 (step #25). As a result, hot water in the first hot water storage tank T1 is supplied to the second hot water storage tank T2 through the hot water pipe 31, as shown in Figure 7. Note that Figure 7 shows the water supply valve 9, drain valve 22, on-off valve 32, and hot water pipe drain valve 35, with closed valves shaded in black.

[0074] That is, when the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is in heat dissipation mode and the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is in heat receiving mode, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is configured to perform second drainage control to open the drainage valve 22 (second drainage valve) of the second hot water storage tank T2 in interchange control.

[0075] The order of the first valve opening control based on step #23 and the second valve opening control based on step #24 may be reversed from the order in the flowchart shown in FIG. 5, or may be simultaneous.

[0076] If the temperature detected by the hot water temperature sensor 33 adjacent to the second hot water storage tank T2 is below a preset temperature (step #21: No), the water in the hot water pipe 31 has become cold, and there is a risk that cold water will flow into the second hot water storage tank T2. Therefore, the control unit H4 (second control unit) in the heat-receiving side fuel cell unit 1 opens the hot water pipe drain valve 35 adjacent to the second hot water storage tank T2 (step #26).

[0077] That is, the control unit H4 (second control unit) in the heat receiving side fuel cell unit 1 is configured to perform a first pre-interchange control in which, when executing the interchange control, the hot water pipe drain valve 35 (third discharge valve) is opened in response to the water temperature in the hot water pipe 31 detected by the hot water temperature sensor 33 being below a predetermined first threshold value.

[0078] When the hot water pipe drain valve 35 is opened, the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side opens the first on-off valve 32A (step #27). In other words, the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is configured to execute first valve opening control to open the first on-off valve 32A in response to execution of the first pre-interchange control if the water temperature in the hot water pipe 31 detected by the hot water temperature sensor 33 when executing interchange control is below the first threshold value.

[0079] When both the first on-off valve 32A and the hot water pipe drain valve 35 are opened, as shown in Figure 6, hot water flows from the first hot water storage tank T1 into the hot water pipe 31, and cold water that has accumulated in the hot water pipe 31 is discharged to the outside through the discharge path 34. Note that Figure 6 shows the water supply valve 9, drain valve 22, on-off valve 32, and hot water pipe drain valve 35, with closed valves shaded in black.

[0080] Then, it is determined whether the hot water temperature sensor 33 adjacent to the second hot water storage tank T2 has detected a temperature equal to or higher than a predetermined second threshold (step #28). The determination in step #28 may be made by the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side, or by the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side. The second threshold is set higher than the first threshold. If the detected temperature of the hot water temperature sensor 33 adjacent to the second hot water storage tank T2 is lower than the second threshold (step #28: No), the process enters a waiting state in step #28.

[0081] When the detected temperature of the hot water temperature sensor 33 (third temperature sensor) adjacent to the second hot water storage tank T2 becomes equal to or higher than the second threshold value (step #28: Yes), the control unit H4 (second control unit) in the heat-receiving-side fuel cell unit 1 closes the hot water pipe drain valve 35 (third discharge valve) adjacent to the second hot water storage tank T2 (step #29). In other words, the control unit H4 (second control unit) in the heat-receiving-side fuel cell unit 1 is configured to execute the second pre-interchange control, which closes the hot water pipe drain valve 35 (third discharge valve) in response to the water temperature in the hot water pipe 31 detected by the hot water temperature sensor 33 (third temperature sensor) after execution of the first pre-interchange control becoming equal to or higher than the second threshold value set higher than the first threshold value.

[0082] Then, the control unit H4 (second control unit) in the heat-receiving side fuel cell unit 1 closes the water supply valve 9 of the second hot water storage tank T2 (step #30), opens the second on-off valve 32B (step #24), and opens the drain valve 22 of the second hot water storage tank T2 (step #25). As a result, the hot water in the first hot water storage tank T1 is supplied to the second hot water storage tank T2 through the hot water supply pipe 31, as shown in FIG.

[0083] That is, when executing the interchange control, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is configured to execute a second valve opening control to open the second opening / closing valve 32B in accordance with the execution of the second pre-interchange control if the water temperature in the hot water pipe 31 detected by the hot water temperature sensor 33 (third temperature sensor) after the execution of the first pre-interchange control by the first control unit becomes equal to or higher than the second threshold value.

[0084] [Another embodiment] The present invention is not limited to the configurations exemplified in the above-described embodiments, and other representative embodiments of the present invention will be exemplified below.

[0085] (1) The outgoing path 13a of the hot water circulation path 13 may be provided with parallel paths, one branching to the radiator and the other not branching to the radiator. In this case, when the temperature of the hot water flowing through the outgoing path 13a rises above a preset temperature, the hot water may flow into the radiator before flowing into the exhaust heat recovery heat exchanger K.

[0086] (2) In the above-described embodiment, when the control unit H4 (first control unit) in the fuel cell unit 1 on the heat dissipation side is in the heat dissipation mode and the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is in the heat receiving mode, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side is configured to execute second drainage control to open the drain valve 22 (second drainage valve) of the second hot water storage tank T2 during interchange control. This embodiment is not limited to this, and the second drainage control may not be executed. In this case, for example, the control unit H4 (second control unit) in the fuel cell unit 1 on the heat receiving side may be configured to execute interchange control from the first hot water storage tank T1 to the second hot water storage tank T2 at the timing when hot water is actually supplied to a bath or the like in a dwelling unit on the heat receiving side.

[0087] (3) Without being limited to the above-described embodiment, for example, when the determination in step #21 shown in Fig. 5 is No, the above interchange control may not be performed if the conditions are such that the heat radiation loss in the hot water supply pipe 31 is large based on the cold region, season, outside temperature, the distance from the first hot water storage tank T1 to the second hot water storage tank T2, etc. This configuration avoids the risk of low-temperature water being supplied to the second hot water storage tank T2 due to heat radiation loss.

[0088] (4) Figure 1 shows an example of an apartment building as a dwelling unit. The dwelling unit may also be a detached house or a two-family home.

[0089] (5) As shown in Fig. 8, a pump 30P may be provided in the water supply passage 30. With this configuration, even if the supply pressure (tap water pressure) from the water supply passage 19 is weak, the pump 30P quickly supplies hot water from the first hot water storage tank T1 to the second hot water storage tank T2.

[0090] (6) In the above embodiment, a polymer electrolyte fuel cell is used as the fuel cell N, but the present invention can also be implemented in the same manner when the fuel cell N includes a solid oxide fuel cell.

[0091] The configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments, unless a contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these, and can be modified as appropriate within the scope of the present invention. [Industrial Applicability]

[0092] The present invention is applicable to fuel cell systems. [Explanation of symbols]

[0093] 1: Fuel cell unit (first fuel cell unit, second fuel cell unit) 13: Circulation path for hot water flow 22: Drain valve (first drain valve, second drain valve) 30: Flexible path 31:Hot water pipe 32: On-off valve (first on-off valve, second on-off valve) 32A: First shut-off valve 32B: Second shut-off valve 33: Hot water temperature sensor (third temperature sensor) 35: Hot water pipe drain valve (third drain valve) H1: Control unit (first control unit, second control unit) H2: Prediction section (first prediction section, second prediction section) H3: Judgment part (first judgment part, second judgment part) N: Fuel cell (first fuel cell, second fuel cell) S: Temperature sensor (first temperature sensor, second temperature sensor) T: Hot water storage tank (first hot water storage tank, second hot water storage tank) T1: First hot water tank T2: Second hot water tank

Claims

1. a first fuel cell unit arranged in a first dwelling unit and having a first fuel cell that generates electricity by supplying hydrogen, a first hot water storage tank that stores hot water heated by exhaust heat from the first fuel cell, a first temperature sensor that detects the temperature of the hot water in the first hot water storage tank, a first control unit that controls the supply and discharge of hot water in the first hot water storage tank, and a first determination unit that determines whether or not it is necessary to release the heat in the first hot water storage tank based on the temperature detected by the first temperature sensor; a second fuel cell unit arranged in a second dwelling unit and having a second fuel cell that generates electricity by supplying hydrogen, a second hot water storage tank that stores hot water heated by exhaust heat from the second fuel cell, a second temperature sensor that detects the temperature of the hot water in the second hot water storage tank, a second control unit that controls the supply and discharge of hot water in the second hot water storage tank, and a second determination unit that determines whether the amount of heat in the second hot water storage tank is sufficient to meet demand in the second dwelling unit based on the temperature detected by the second temperature sensor; a hot water pipe communicating with the first hot water storage tank and the second hot water storage tank; the first control unit switches the control mode to a heat release mode when the first determination unit determines that the amount of heat in the first hot water storage tank needs to be released, the second control unit switches the control mode to a heat receiving mode when the second determination unit determines that the amount of heat in the second hot water storage tank is insufficient to meet the demand in the second dwelling unit; A fuel cell system configured such that when the first control unit is in the heat dissipation mode and the second control unit is in the heat reception mode, the first control unit and the second control unit perform interchange control to supply hot water in the first hot water storage tank to the second hot water storage tank through the hot water supply pipe.

2. the first fuel cell unit is provided with a first prediction unit that calculates an estimated consumption amount of heat in the first hot water storage tank within a preset time period; The fuel cell system of claim 1, wherein the first judgment unit is configured to determine whether or not it is necessary to release heat in the first hot water storage tank based on the detected temperature of the first temperature sensor, the amount of heat received by the exhaust heat of the first fuel cell, and the estimated consumption calculated by the first prediction unit.

3. the second fuel cell unit is provided with a second prediction unit that calculates an estimated consumption amount of heat in the second hot water storage tank within a preset time period; The fuel cell system of claim 1, wherein the second judgment unit is configured to determine whether the amount of heat in the second hot water storage tank is sufficient to cover the demand in the second dwelling unit based on the detected temperature of the second temperature sensor, the amount of heat received by the exhaust heat of the second fuel cell, and the estimated consumption calculated by the second prediction unit.

4. the first fuel cell unit is provided with a first drain valve for draining hot water from the first hot water storage tank; 2. The fuel cell system of claim 1, wherein when the first control unit is in the heat release mode and the second control unit is not in the heat receiving mode, the first control unit is configured to execute first drain control to open the first drain valve.

5. the second fuel cell unit is provided with a second drain valve that drains hot water from the second hot water storage tank; 2. The fuel cell system of claim 1, wherein when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode, the second control unit is configured to perform second drainage control to open the second drainage valve in the interchange control.

6. a first on-off valve that opens and closes a flow path between the first hot water storage tank and the hot water pipe; a second on-off valve for opening and closing a flow path between the second hot water storage tank and the hot water supply pipe; the first control unit is configured to execute first valve opening control to open the first on-off valve in the interchange control when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode, 6. A fuel cell system as described in any one of claims 1 to 5, wherein the second control unit is configured to execute a second valve opening control to open the second opening / closing valve in the interchange control when the first control unit is in the heat release mode and the second control unit is in the heat receiving mode.

7. a third discharge valve for discharging water from the hot water pipe; a third temperature sensor for detecting the water temperature in the hot water pipe; When executing the interchange control, at least one of the first control unit and the second control unit is configured to execute a first pre-interchange control in which the third discharge valve is opened in response to the water temperature in the hot water pipe detected by the third temperature sensor being lower than a predetermined first threshold, and to execute a second pre-interchange control in which the third discharge valve is closed in response to the water temperature in the hot water pipe detected by the third temperature sensor being equal to or higher than a second threshold set higher than the first threshold after the execution of the first pre-interchange control, The first control unit is configured to execute the first valve opening control in response to execution of the first pre-interchange control when the water temperature in the hot water pipe detected by the third temperature sensor is lower than the first threshold value when executing the interchange control, The fuel cell system of claim 6, wherein the second control unit is configured to execute the second valve opening control in response to the execution of the second pre-interchange control when the water temperature in the hot water pipe detected by the third temperature sensor after the first control unit executes the first pre-interchange control becomes equal to or higher than the second threshold value when executing the interchange control.

8. The hot water in the first hot water storage tank is drawn from the bottom of the first hot water storage tank, heated by the exhaust heat of the first fuel cell, and then circulated through a hot water flow circulation path that returns the hot water to the top of the first hot water storage tank; The hot water in the second hot water storage tank is drawn from the bottom of the second hot water storage tank, heated by the exhaust heat of the second fuel cell, and then circulated through a hot water flow circulation path that returns the hot water to the top of the second hot water storage tank; A hot water supply passage is connected between the upper portion of the first hot water storage tank and the hot water supply pipe, The fuel cell system according to any one of claims 1 to 5, wherein an interchange passage is connected between the upper portion of the second hot water storage tank and the hot water supply pipe.

Images