Combined heat and power system

Abstract

To provide a combined heat and power supply system capable of preventing temperature stratification in a hot water storage tank from being disturbed.SOLUTION: A combined heat and power supply device comprises a hot water consumption circuit 24 which has a hot water supply passage 24a supplying hot water taken out from an upper section of a hot water storage tank T to a heat radiation heat exchanger 23 and a return passage 24b returning the hot water undergoing heat exchange in the radiation heat exchanger 23 to the hot water storage tank T. The return passage 24b is connected to an intermediary position in a vertical direction on the hot water storage tank T. An operation control section H: executes a hot water consumption process to circulate the hot water through the hot water consumption circuit 24 at a target flow rate; and sets the target flow rate to a reduced target flow rate corrected to be smaller than the target flow rates when a temperature difference between a temperature detected with a return point temperature detection sensor S4 detecting a temperature of the hot water at a point where the return passage 24b is connected to the hot water storage tank T and a temperature detected with a return temperature detection sensor 29 detecting a temperature of the hot water flowing in the return passage 24b is equal to or higher than a set value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention provides a fuel cell that generates electricity by supplying hydrogen, a sealed hot water storage tank that stores hot water and is supplied with water from the bottom, and a heat dissipation recovery heat exchanger that recovers the waste heat of the fuel cell. In this form, a hot water flow circulation path that connects the bottom and the top of the hot water storage tank, a heat storage circulation pump that circulates hot water through the hot water flow circulation path in such a way that the hot water taken out from the bottom of the hot water storage tank is returned to the top of the hot water storage tank, and an operation control unit are provided. The operation control unit is configured to execute waste heat recovery type hot water storage treatment for controlling the operation of the heat storage circulation pump in such a way that the temperature of the hot water supplied to the upper part of the hot water storage tank through the hot water flow circulation path becomes the target temperature so as to store hot water in a state where a temperature stratification is formed in the hot water storage tank in the operating state of the fuel cell. A hot water consumption circuit is provided, which consists of a hot water supply path that supplies the hot water taken out from the upper part of the hot water storage tank to a heat dissipation heat exchanger and a return path that returns the hot water heat-exchanged in the heat dissipation heat exchanger to the hot water storage tank. A consumption circulation pump that circulates hot water through the hot water consumption circuit is provided. The present invention relates to a cogeneration system configured such that the operation control unit executes hot water consumption treatment for controlling the operation of the consumption circulation pump in such a way that hot water is circulated at a set target flow rate through the hot water consumption circuit.

Background Art

[0002] In a cogeneration system, in addition to supplying the electric power generated by a fuel cell to an electric power load, the waste heat of the fuel cell is used to store hot water in a state where a temperature stratification is formed in a hot water storage tank, and the stored hot water is used for hot water supply, or the stored hot water is supplied to a heat dissipation heat exchanger to heat, for example, a heating medium for heating by heat dissipation, so as to effectively utilize the waste heat of the fuel cell.

[0003] A conventional example of such a combined heat and power system is one in which the return path of the hot water consumption circuit is connected to a point midway between the top and bottom of the hot water storage tank (see, for example, Patent Document 1).

[0004] In Patent Document 1, when the temperature of the hot water flowing through the return path of the hot water consumption circuit is low (less than 40°C), the hot water flowing through the return path is returned to the bottom of the hot water storage tank, and when the temperature of the hot water flowing through the return path of the hot water consumption circuit is high (40°C or higher), the hot water flowing through the return path is returned to an intermediate position between the top and bottom of the hot water storage tank. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-35521 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Even when the hot water flowing in the return path is returned to an intermediate point between the top and bottom of the hot water storage tank, if the temperature of the hot water stored in the intermediate point of the hot water storage tank is considerably higher than the temperature of the hot water flowing in the return path of the hot water consumption circuit, it is difficult to prevent the collapse of the temperature stratification in the hot water storage tank.

[0007] In other words, when the temperature of the hot water stored in the upper and lower intermediate sections of the hot water storage tank is considerably higher than the temperature of the hot water flowing through the return path of the hot water consumption circuit, returning the hot water flowing through the return path to the inside of the hot water storage tank at a set target flow rate results in the high-temperature hot water stored in the upper and lower intermediate sections of the hot water storage tank being agitated by the low-temperature hot water flowing vigorously into the inside of the hot water storage tank through the return path. This causes a significant drop in the temperature of the hot water stored in the upper and lower intermediate sections of the hot water storage tank, thus disrupting the temperature stratification of the hot water storage tank.

[0008] This invention has been made in view of the above-mentioned problems, and its purpose is to provide a combined heat and power system that can suppress the collapse of the temperature stratification in a hot water storage tank. [Means for solving the problem]

[0009] The combined heat and power system of the present invention comprises a fuel cell that generates electricity by supplying hydrogen, a sealed hot water storage tank that stores hot water and is supplied with hot water from the bottom, a hot water circulation path connecting the bottom and top of the hot water storage tank via a heat recovery heat exchange unit that recovers waste heat from the fuel cell, and a heat storage circulation pump that circulates hot water through the hot water circulation path in a manner that returns the hot water taken from the bottom of the hot water storage tank to the top of the hot water storage tank. A heating terminal that uses the hot water stored in the aforementioned hot water storage tank for heating, An operation control unit is provided, The operation control unit is configured to perform a waste heat recovery type hot water storage treatment by controlling the operation of the heat storage circulation pump in such a manner that, in order to store hot water in the hot water storage tank in a state in which a temperature stratification is formed in the operating state of the fuel cell, the amount of hot water circulated through the hot water flow circulation path so that the temperature of the hot water supplied to the upper part of the hot water storage tank through the hot water flow circulation path reaches a target temperature. A hot water consumption circuit is provided, comprising a hot water supply path that supplies hot water taken from the top of the hot water storage tank to a heat exchanger for heat dissipation, and a return path that returns the hot water that has undergone heat exchange in the heat exchanger back to the hot water storage tank. A consumption circulation pump is provided to circulate hot water through the aforementioned hot water consumption circuit. A heat transfer medium circulation path is provided between the heat dissipation heat exchanger and the heating terminal for circulating the heat transfer medium. The aforementioned operation control unit performs a hot water consumption process that controls the operation of the consumption circulation pump in a manner that circulates hot water through the hot water consumption circuit at a set target flow rate. Furthermore, a heating circulation process is performed in which the heat transfer medium is circulated through the heat transfer medium circulation path. A combined heat and power system configured to include, The return path is the hot water storage tank A location below the midpoint between the bottom and the top, and above the bottom. Connected to A drainage section is provided to drain water from the top of the hot water storage tank. The operation control unit, No hot water consumption command has been issued by the manual control unit. The hot water temperature at the point where the return path in the hot water storage tank is connected is detected. If the temperature detected by the return point temperature detection sensor is equal to or greater than the set start temperature, and the heating terminal is operational, the hot water consumption processing and the heating circulation processing are executed, and theWhen the temperature difference between the detected temperature of the return point temperature detection sensor and the detected temperature of the return temperature detection sensor that detects the temperature of the hot and cold water flowing through the return path is equal to or greater than the set value, the set target flow rate is set to the reduced target amount corrected to the decreasing side. death, If no hot water consumption command has been issued by the manual operation control unit, and the temperature detected by the lower temperature sensor, located above the bottom of the hot water storage tank and below the connection point of the return path, detects the set high temperature, and the operation of the heating terminal is not possible, then the drainage process will be executed by draining water from the drainage unit. This is the point.

[0010] That is, the temperature of the hot and cold water at the location where the return path in the hot water storage tank is connected is detected by the return point temperature detection sensor, and the temperature of the hot and cold water flowing through the return path is detected by the return temperature detection sensor. No hot water consumption command has been issued by the manual control unit. No hot water consumption command has been issued by the manual control unit. When the temperature difference between the detected temperature of the return point temperature detection sensor and the detected temperature of the return temperature detection sensor is equal to or greater than the set value And the operation of the heating terminal is possible. In this case, Perform the hot water consumption processing, Since the set target flow rate is set to the reduced target amount corrected to the decreasing side, when the temperature difference is equal to or greater than the set value, the low-temperature hot and cold water flowing through the return path flows into the inside of the hot water storage tank with its momentum suppressed. Furthermore, by setting the starting temperature to a high temperature (for example, 60°C) that allows for the formation of a temperature stratification in the hot water storage tank, it is possible to suppress the temperature of the hot water stored below the point where the return path is connected in the hot water storage tank from becoming too high. Furthermore, if the operation control unit has not received a hot water consumption command from the manual operation command unit, and the temperature detected by the lower temperature sensor located above the bottom of the hot water storage tank and below the connection point of the return path detects the set high temperature, and the operation of the heating terminal is not possible, then the operation control unit will perform drainage processing to drain water from the drain section. Therefore, when the lower temperature sensor located above the bottom of the hot water storage tank and below the connection point of the return path detects the set high temperature (for example, 40°C), the operation control unit will perform drainage processing to drain water from the drain section that drains water from the top of the hot water storage tank, so that cold water is supplied to the bottom of the hot water storage tank.

[0011] A point below the midpoint between the bottom and the top, and above the bottom. Therefore, when the temperature difference is equal to or greater than the set value, the low-temperature hot and cold water flowing through the return path flows into the high-temperature hot and cold water stored in the hot water storage tank with its momentum suppressed. As a result, the high-temperature hot and cold water stored in the hot water storage tank is suppressed from being stirred by the low-temperature hot and cold water flowing in, and the temperature stratification of the hot water storage tank is suppressed from collapsing. A point below the midpoint between the bottom and the top, and above the bottom. In other words, when the temperature difference is less than the set value, hot and cold water can be made to flow through the hot and cold water consumption circuit at the set target flow rate, and sufficient heat can be supplied to the heat exchanger for heat dissipation. Furthermore, if the temperature of the hot water stored below the point where the return path is connected in the hot water storage tank becomes high, it would be necessary to drain the high-temperature hot water taken from the top of the storage tank in order to prevent the temperature of the hot water supplied to the heat recovery heat exchange unit through the hot water circulation path from becoming too high. However, this system helps to avoid such waste as much as possible. Furthermore, by ensuring that cold water is present at the bottom of the hot water storage tank, the temperature of the hot water supplied to the heat recovery heat exchange unit through the hot water circulation path is kept low. This effectively avoids problems such as fuel cell failure caused by high-temperature hot water flowing through the hot water circulation path to the heat recovery heat exchange unit.

[0012] In short, according to the characteristic configuration of the cogeneration system of the present invention, it is possible to suppress the collapse of the temperature stratification of the hot water storage tank.

[0013] ​A further characteristic configuration of the cogeneration system of the present invention is that when a hot and cold water consumption command is issued by the manual operation command unit, the operation control unit executes the hot and cold water consumption process. Furthermore, if the temperature difference between the temperature detected by the return temperature detection sensor and the temperature detected by the return temperature detection sensor is greater than or equal to the set value, the set target flow rate is set to the reduction target amount. This is the point.

[0014] That is, for example, when heating a heating medium for heating in a heat exchange for heat dissipation, when a hot and cold water consumption command is issued by the manual operation command unit, the hot and cold water consumption process is executed. Therefore, it is possible to perform hot and cold water consumption well according to the command of the manual operation command unit, such as performing heating operation while heating the heating medium for heating in the heat exchange for heat dissipation. When a hot water consumption command is issued by the manual operation control unit and the temperature difference exceeds a set value, the low-temperature hot water flowing through the return path flows into the high-temperature hot water stored in the area below the midpoint between the bottom and top of the hot water storage tank, but above the bottom, with reduced force. This prevents the high-temperature hot water stored in the area below the midpoint between the bottom and top of the hot water storage tank from being agitated by the incoming low-temperature hot water, thereby preventing the collapse of the temperature stratification in the hot water storage tank.

[0015] In short, according to the further characteristic configuration of the cogeneration system of the present invention, hot and cold water consumption can be performed well according to the command of the manual operation command unit.

[0020] A further characteristic configuration of the cogeneration system of the present invention is ,before that when the lower temperature sensor detects the set high temperature, the operation control unit executes a drainage process of draining water at the drainage unit. The aforementioned This is the point.

[0021] That is, when a lower temperature sensor provided below the connection point of the return path above the bottom of the hot water storage tank detects the set high temperature (for example, 40 ° C), the operation control unit executes a drainage process of draining water at the drainage unit that drains water from the upper part of the hot water storage tank. Therefore, cold water will be supplied to the bottom of the hot water storage tank.

[0022] <00,00111>Therefore, since the state where cold water exists at the bottom of the hot water storage tank can be accurately maintained, the temperature of the hot and cold water supplied to the exhaust heat recovery heat exchange unit through the hot and cold water flow circulation path is maintained at a low temperature. For example, troubles such as the fuel cell malfunctioning due to high-temperature hot and cold water flowing through the hot and cold water flow circulation path to the exhaust heat recovery heat exchange unit can be appropriately avoided.

[0023] In short, the further characteristic configuration of the cogeneration system of the present invention can appropriately avoid the occurrence of troubles.

[0024] A further characteristic feature of the combined heat and power system of the present invention is that a hot water flow section is provided inside the hot water storage tank, which causes the hot water from the return path to flow from multiple locations in the width direction of the hot water storage tank toward the bottom of the tank.

[0025] In other words, since the hot water from the return path flows into the hot water storage tank from multiple points along the width of the tank towards the bottom of the tank through hot water flow sections, the agitation of the hot water in the storage tank can be avoided as much as possible because the hot water from the return path flows into the storage tank from multiple points. Moreover, because the hot water from the return path flows towards the bottom of the tank, it is possible to suppress disturbance of the temperature stratification formed by the high-temperature hot water on the upper side of the storage tank.

[0026] In short, according to the further characteristic configuration of the combined heat and power system of the present invention, it is possible to minimize the agitation of the hot water in the hot water storage tank by the hot water from the return path, and also to suppress disturbances in the temperature stratification of the hot water storage tank.

[0027] A further characteristic feature of the combined heat and power system of the present invention is that it is provided with a hydrogen supply source that supplies pure hydrogen to the fuel cell.

[0028] In other words, since the fuel cell operates using pure hydrogen supplied from a hydrogen source, the configuration for operating the fuel cell can be simplified. In other words, if a reforming device is installed to convert fuels such as city gas into hydrogen gas, and the fuel cell is operated using the hydrogen gas reformed by that device, the configuration for operating the fuel cell becomes complex, and the overall system configuration becomes complicated. However, by operating the fuel cell with pure hydrogen supplied from a hydrogen source, the overall system can be simplified.

[0029] In short, the characteristic configuration of the combined heat and power system of the present invention allows for the simplification of the entire system. [Brief explanation of the drawing]

[0030] [Figure 1] This is a schematic diagram of a combined heat and power system. [Figure 2] This is a flowchart showing the control operation. [Figure 3] This is a flowchart showing the control operation. [Modes for carrying out the invention]

[0031] [Embodiment] Hereinafter, embodiments of the combined heat and power system of the present invention will be described based on the drawings. (Overall configuration of the combined heat and power system) As shown in Figure 1, a commercial power transmission line 4A from a commercial power source 4 that supplies commercial power is connected to an indoor distribution board 3 to which a power supply line 2 for a power load 1 is connected, and a power transmission line 5 from a fuel cell N provided by a power generation module M is connected to the indoor distribution board 3.

[0032] The fuel cell N in this embodiment is a polymer electrolyte fuel cell and is configured to generate electricity using hydrogen (pure hydrogen) supplied from a hydrogen supply source G as fuel. In other words, the fuel cell N in this embodiment is configured without a reformer that processes a raw material gas such as city gas to produce hydrogen.

[0033] The power transmission line 5 from the fuel cell N is equipped with a power conversion unit 6 that includes a grid-connection inverter and the like to adjust the power generated by the fuel cell N to the same voltage and frequency as the power supplied from the commercial power source 4. Therefore, the system is configured to supply commercial power from commercial power source 4 and power generated by fuel cell N to power load 1.

[0034] The power generation module M is equipped with a heat recovery heat exchanger K (an example of a heat recovery heat exchange unit) that recovers waste heat from the fuel cell N. Furthermore, the storage tank T, which stores hot water, is configured to store the hot water heated by the heat recovery heat exchanger K in a manner that forms a temperature stratification, and the stored hot water is used for hot water supply and heating of the heating terminal D. In this embodiment, the heating terminal D is a floor heating panel.

[0035] Furthermore, an operation control unit H is provided to control the operation of the combined heat and power system, including the operation of the fuel cell N, and a remote control R (an example of a manual operation control unit) is connected to the operation control unit H. The remote control R includes a power generation remote control R1 that issues commands to start and stop the operation of the fuel cell N, and an operation remote control R2 that issues various commands such as commands to start floor heating operation (floor heating start command), commands to stop floor heating operation (floor heating stop command), and target temperature for hot water supply. Therefore, the operation control unit H is configured to control the operation of the combined heat and power system based on commands from the remote control R.

[0036] (Details of the power generation module) The fuel cell N consists of multiple stacked cells C, each composed of a solid polymer electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode. A cooling section 7, having a cooling water channel through which cooling water flows, is provided between adjacent cells C, and is configured to cool the cells C to an appropriate temperature (for example, 80°C). The cooling section 7 is formed using a conductive and porous material, such as a carbon plate. Therefore, the cooling water flowing through the cooling water channel of the cooling section 7 is supplied to the solid polymer electrolyte membrane through the fuel electrode.

[0037] A cooling water circulation path 8 is connected to the cooling unit 7, and the cooling water, whose temperature has risen as it passes through the cooling unit 7, is configured to flow into a heat recovery heat exchanger K located in the middle of the cooling water circulation path 8. In other words, the heat from cell C recovered in the cooling unit 7 is recovered (supplied) to the waste heat recovery heat exchanger K as waste heat from the fuel cell N.

[0038] The cooling water circulation path 8 is equipped with a cooling water circulation pump 10 for circulating the cooling water, a water tank 11 for storing the cooling water, and a water treatment device 12. The cooling water supplied from the water tank 11 is expected to contain electrolytes and impurities that do not dissolve in water. Therefore, the system is configured to purify the cooling water supplied from the water tank 11 using the water treatment device 12. For example, the water treatment device 12 is configured to include an adsorbent capable of adsorbing organic matter and other substances present in the cooling water, and an ion exchange resin capable of removing ions dissolved in the cooling water.

[0039] (Hot water storage configuration) As shown in Figure 1, a hot water circulation path 13 is provided that connects the bottom and top of the hot water storage tank T via a heat recovery heat exchanger K, and a heat storage circulation pump 14 is provided that circulates the hot water through the hot water circulation path 13, returning the hot water taken from the bottom of the hot water storage tank T to the top of the hot water storage tank T. The hot water circulation path 13 consists of a forward path 13a connecting the bottom of the hot water storage tank T to the heat recovery heat exchanger K, and a return path 13b connecting the heat recovery heat exchanger K to the top of the hot water storage tank T. The forward path 13a is equipped with the aforementioned heat storage circulation pump 14.

[0040] Upstream of the heat storage circulation pump 14 in the outbound path 13a, a cold water side sensor 15 is provided as a temperature sensor to detect the temperature of the hot water taken from the bottom of the hot water storage tank T. Furthermore, the return path 13b is equipped with a hot water side sensor 16, which acts as a temperature sensor to detect the temperature of the hot water heated in the heat recovery heat exchanger K.

[0041] The operation control unit H is configured to perform a waste heat recovery type hot water storage treatment by controlling the operation of the heat storage circulation pump 14 in such a way that, in order to store hot water in the hot water storage tank T in a state in which a temperature stratification is formed in the operating state of the fuel cell N, the amount of hot water circulated through the hot water flow circulation path 13 so that the temperature of the hot water supplied to the upper part of the hot water storage tank T through the hot water flow circulation path 13 reaches a target temperature (for example, 60°C). Incidentally, the above target temperature may be automatically set to different temperatures depending on the season, such as summer, winter, or transitional season, or it may be configured so that the user can set their preferred temperature using the remote control R.

[0042] In other words, the operation control unit H is configured to perform a process to control the rotation speed of the heat storage circulation pump 14 so that the temperature detected by the hot water side sensor 16 reaches the target temperature, using the temperature detected by the cold water side sensor 15 as feedforward information, as part of the waste heat recovery type hot water storage process. As a result, the hot water is stored in the hot water storage tank T in a state where a temperature stratification is formed, with the temperature increasing towards the top.

[0043] Furthermore, the hot water stored in the hot water storage tank T is configured to be supplied to hot water consumption points such as hot water taps 18 through a hot water outlet passage 17 connected to the top of the hot water storage tank T. When the hot water stored in the hot water storage tank T is released, water is supplied to the bottom of the hot water storage tank T from a water source such as the public water supply through the water supply channel 19 connected to the bottom of the hot water storage tank T. In other words, the flow of hot water through the hot water outlet channel 17 is carried out using the water supply pressure in the water supply channel 19. Incidentally, in this embodiment, the hot water outlet 17 is provided with an auxiliary heat source unit 20 that heats the hot water from the hot water storage tank T when the temperature of the hot water from the storage tank T is lower than the required temperature of the hot water consumption point.

[0044] The hot water storage tank T is equipped with several temperature sensors S for detecting the temperature of the stored hot water. These include an upper temperature sensor S1 located at the top of the tank, an upper intermediate temperature sensor S2 located in the upper middle section between the top and the center of the tank, an upper and lower central temperature sensor S3 located in the center of the tank, a lower intermediate temperature sensor S4 located in the lower middle section between the center and the bottom of the tank, and a lower temperature sensor S5 located at the bottom of the tank. Incidentally, the lower temperature sensor S5 is located above the bottom of the tank. Furthermore, the operation control unit H is configured to check the hot water storage status in the hot water storage tank T based on the detection information from the temperature sensor S.

[0045] (Water discharge control) As shown in Figure 1, a drainage channel 21 for draining hot water to the outside is provided upstream of the auxiliary heat source unit 20 in the hot water outlet channel 17, and an electromagnetically operated drain valve 22 for opening and closing the drainage channel 21 is provided in the drainage channel 21. The drainage channel 21 may be configured to guide the hot water into the bathtub. Incidentally, in this embodiment, the drain valve 22 functions as a drainage unit that drains water from the top of the hot water storage tank T.

[0046] Furthermore, the operation control unit H is configured to open the drain valve 22 and perform drainage when the lower temperature sensor S5, which is located above the bottom of the hot water storage tank T, detects a set high temperature (for example, 40°C). In other words, by maintaining a state where chilled water supplied from the water supply channel 19 is present at the bottom of the hot water storage tank T, problems such as fuel cell N failure are avoided. In other words, if the hot water at the bottom of the hot water storage tank T becomes hot, this hot water flows into the heat recovery heat exchanger K, causing the cooling water flowing through the cooling water circulation path 8 to become hot. This can prevent the cells C of the fuel cell N from being properly cooled, potentially leading to problems such as fuel cell N failure. However, this problem can be avoided.

[0047] (Hot water consumption composition) As shown in Figure 1, a hot water consumption circuit 24 is provided, consisting of a hot water supply passage 24a that supplies hot water taken from the top of the hot water storage tank T to a heat exchanger 23 for heat dissipation, and a return passage 24b that returns the hot water that has undergone heat exchange in the heat exchanger 23 back to the hot water storage tank T. A consumption circulation pump 25 is provided in this hot water consumption circuit 24 to circulate the hot water through the hot water consumption circuit 24. Furthermore, a heat medium circulation path 26 is provided to circulate the heat medium between the heat dissipation heat exchanger 23 and the heating terminal D, and a heat medium circulation pump 27 is provided in this heat medium circulation path 26 to circulate the heat medium.

[0048] The return path 24b is connected to the upper and lower midpoint of the hot water storage tank T. More specifically, the return path 24b is connected to a location below the upper and lower midpoint of the hot water storage tank T and above the bottom of the tank. In this embodiment, the return path 24b is connected to a location corresponding to the installation location of the lower midpoint temperature sensor S4. Therefore, the lower midpoint temperature sensor S4 functions as a return point temperature detection sensor that detects the temperature of the hot water at the location in the hot water storage tank T to which the return path 24b is connected. In this embodiment, a hot water flow section U is provided inside the hot water storage tank T, which causes hot water from the return path 24b to flow from multiple locations in the width direction of the hot water storage tank T toward the bottom of the tank. Furthermore, the lower temperature sensor S5 will be located above the bottom of the hot water storage tank T and below the connection point of the return path 24b.

[0049] The hot and cold water supply path 24a is equipped with a flow sensor 28 that detects the flow rate (flow rate per unit time) of the hot and cold water flowing through the hot and cold water consumption circuit 24, and the return path 24b is equipped with a return temperature detection sensor 29 that detects the temperature of the hot and cold water flowing through this return path 24b.

[0050] Furthermore, the operation control unit H is configured to perform 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 performing the hot water consumption process, it is also configured to perform a heating circulation process that circulates the heat medium through the heat medium circulation path 26. In other words, the operation control unit H operates the consumption circulation pump 25 and the heat transfer fluid circulation pump 27 as part of the hot water consumption process, and is configured to execute a process to control the operation (rotational speed) of the consumption circulation pump 25 in order to circulate the hot water through the hot water consumption circuit 24 at a set target flow rate, based on the detection information from the flow sensor 28.

[0051] Specifically, the operation control unit H is configured to execute the hot water consumption process when a floor heating start command (an example of a hot water consumption command) is issued via the operation remote control R2, and to forcibly execute the hot water consumption process when the temperature detected by the lower intermediate temperature sensor S4 is above the set start temperature (for example, 60°C) while the hot water consumption process is not being executed. Incidentally, when forcibly executing the hot water consumption process, the system is configured to stop the forced execution of the hot water consumption process during periods when underfloor heating is not needed (such as in summer), as it is considered that underfloor heating cannot be operated.

[0052] Furthermore, the operation control unit H is configured to set the target flow rate to a reduced target amount by correcting it to a reduced amount if the temperature difference between the temperature detected by the lower intermediate temperature sensor S4, which detects the temperature of the hot water at the point where the return path 24b in the hot water storage tank T is connected, and the temperature detected by the return temperature detection sensor 29, which detects the temperature of the hot water flowing through the return path 24b, is greater than or equal to a set value (for example, 5°C). Incidentally, the target reduction amount is preferably set to a flow rate that is 30% to 50% lower than the set target flow rate.

[0053] In this embodiment, the operation control unit H is configured to perform an initial operation in which, during the initial operation period immediately after the start of the hot water consumption process (for example, a few minutes such as 3 to 5 minutes), the hot water is circulated at an initial target amount that is less than the set target flow rate. In other words, immediately after the start of the hot water consumption process, it is expected that the temperature detected by the return temperature detection sensor 29 will be unstable. Therefore, until the temperature detected by the return temperature detection sensor 29 stabilizes, the hot water is circulated at the initial target amount to suppress disturbances in the temperature stratification of the hot water stored inside the hot water storage tank T. Incidentally, as for the initial target amount, similar to the reduction target amount, it is preferable to set the flow rate to a flow rate that is 30% to 50% lower than the set target flow rate.

[0054] (Details of control operation) Next, the control operations of the operation control unit H during and after the execution of the waste heat recovery type hot water storage treatment will be explained based on Figure 2. This hot water management treatment is used to perform hot water consumption treatment and wastewater treatment. First, it is determined whether or not the hot water consumption process is currently running (#1). If the hot water consumption process is not currently running, it is then determined whether or not a floor heating start command has been issued via the operating remote control R2 (#2). If a floor heating start command has been issued, the hot water consumption process is executed (#5). Incidentally, when this hot water consumption process is executed, the heating circulation process is performed as described above.

[0055] If process #1 determines that the hot water consumption process is currently running, the process will proceed to process #5, the hot water consumption process. Details of the hot water consumption process will be described later. In process #2, if it is determined that no floor heating start command has been issued, it is determined whether the return point temperature detected by the lower intermediate temperature sensor S4 is equal to or greater than the set start temperature (for example, 60°C) (#3). If the return point temperature is equal to or greater than the set start temperature, it is then determined whether or not floor heating can be performed (#4). If floor heating can be performed, the hot water consumption process is executed (#5).

[0056] If, in process #3, it is determined that the return temperature is not equal to or greater than the set start temperature (for example, 60°C), or if, in process #4, it is determined that floor heating cannot be performed, the process proceeds to process #9 described below.

[0057] After the hot water consumption process in #5 is executed, the operating remote control R2 determines whether or not a floor heating stop command has been issued (#6). If a floor heating stop command has been issued, the consumption circulation pump 25 is stopped and the hot water consumption process is stopped (#8). Incidentally, when this hot water consumption process is stopped, the heat transfer fluid circulation pump 27 is also stopped and the heating circulation process is also stopped.

[0058] In the process of #6, if no floor heating stop command has been issued, it is determined whether the return point temperature detected by the lower intermediate temperature sensor S4 is below the set stop temperature (e.g., 3°C) which is lower than the set start temperature (e.g., 60°C) (#7). Then, if the return point temperature is below the set stop temperature, the hot water consumption process is stopped (#8), and if the return point temperature is not below the set stop temperature, the process proceeds to #9.

[0059] In process #9, it is determined whether or not wastewater treatment is in progress. If wastewater treatment is not in progress, it is determined whether or not the lower temperature detected by the lower temperature sensor S5 is equal to or above the wastewater start temperature (e.g., 40°C) (#10). If the lower temperature is equal to or above the wastewater start temperature, the wastewater treatment is performed by opening the wastewater valve 22.

[0060] In process #9, if it is determined that wastewater treatment is in progress, it is determined whether the lower temperature detected by the lower temperature sensor S5 is below the set temperature (e.g., 3°C) which is lower than the wastewater start temperature (e.g., 40°C) (#12). If the lower temperature is below the wastewater stop temperature, the drain valve 22 is closed to stop wastewater treatment, and then the process proceeds to process #1.

[0061] Furthermore, if the process in #10 determines that the lower temperature is not above the drainage start temperature, or if the process in #12 determines that the lower temperature is not below the drainage stop temperature, the process will proceed to #1.

[0062] (Details of hot and cold water consumption processing) Next, the control operation of the hot water consumption process will be explained based on Figure 3. Note that while the heating circulation process is performed simultaneously with the hot water consumption process, the explanation of the heating circulation process will be omitted below.

[0063] First, it is determined whether or not it is the initial operating period (for example, a few minutes such as 3 to 5 minutes) (#21). If it is the initial operating period, an initial operation is performed to circulate hot water at the initial target amount (#22), and then the process proceeds to the hot water management treatment described above.

[0064] If the process in #21 determines that it is not the initial operating period, the next step is to determine whether the temperature difference between the temperature detected by the lower intermediate temperature sensor S4 and the temperature detected by the return temperature detection sensor 29 is equal to or greater than a set value (for example, 5°C) (#23). If the temperature difference is not equal to or greater than the set value, the process of controlling the operation (rotation speed) of the consumption circulation pump 25 in order to circulate hot water through the hot water consumption circuit 24 at the set target flow rate is executed (#24), and then the process proceeds to the hot water management process described above.

[0065] Furthermore, in step #23, if it is determined that the temperature difference between the temperature detected by the lower intermediate temperature sensor S4 and the temperature detected by the return temperature detection sensor 29 is greater than or equal to a set value (for example, 5°C), the system executes a process to control the operation (rotation speed) of the consumption circulation pump 25 in order to circulate the hot water through the hot water consumption circuit 24 at the target flow rate (#24), and then proceeds to the hot water management process described above.

[0066] [Another embodiment] Next, we will list other embodiments. (1) In the above embodiment, a polymer electrolyte fuel cell was given as an example of fuel cell N, but the same can be carried out when a solid oxide fuel cell is provided as fuel cell N.

[0067] (2) In the above embodiment, an example was given in which heat from the heat exchanger 23 is consumed at the heating terminal D, but various heat consumption terminals such as a bathroom heating terminal or a bath reheating terminal can be used instead of the heating terminal D.

[0068] (3) In the above embodiment, an example was given in which the forced execution of the hot water consumption process is stopped when the floor heating is not needed (such as in summer) because the floor heating cannot be performed. However, the specific configuration for determining whether the floor heating cannot be performed can be changed in various ways. For example, a spatial temperature sensor is provided to detect the temperature of the space in which the heating terminal D is installed, and if the temperature detected by the spatial temperature sensor is high enough to be above the set temperature, the floor heating cannot be performed. Alternatively, the determination that the floor heating cannot be performed may be omitted, and the hot water consumption process may be performed if the return point temperature detected by the lower intermediate temperature sensor S4 is above the set start temperature (for example, 60°C).

[0069] (4) In carrying out the present invention, a small radiator for cooling the hot water may be provided in the forward passage 13a of the hot water circulation path 13, and the radiator may be activated when the temperature detected by the cold water side sensor 15 is above the set upper limit temperature (for example, 40°C). In other words, although the temperature of the hot water flowing in the forward passage 13a of the hot water circulation path 13 will not rise due to the drainage treatment described above, if the temperature detected by the cold water side sensor 15 is above the set upper limit temperature, the radiator may be activated to avoid problems such as the fuel cell N stopping.

[0070] (5) In the above embodiment, when the temperature difference between the temperature detected by the lower intermediate temperature sensor S4, which detects the temperature of the hot water at the point where the return passage 24b in the hot water storage tank T is connected, and the temperature detected by the return temperature detection sensor 29, which detects the temperature of the hot water flowing through the return passage 24b, is greater than or equal to a set value (for example, 5°C), that is, when the temperature detected by the lower intermediate temperature sensor S4 is greater than or equal to the temperature detected by the return temperature detection sensor 29, the set target flow rate is corrected to a reduced target amount.

[0071] In addition, the system may be configured to set the target flow rate to a reduced amount if the temperature detected by the lower intermediate temperature sensor S4 is lower than the temperature detected by the return temperature detection sensor 29 by a set value (e.g., 5°C) or more.

[0072] Furthermore, the configurations disclosed in the above embodiments (including other embodiments) can be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto and can be modified as appropriate without departing from the object of the present invention. [Explanation of symbols]

[0073] 13 Circulation path for hot water flow 14. Circulation pump for thermal energy storage 22 Drainage section 24 Hot water consumption circuit 24a Hot water supply path 24b Return route 25. Consumption circulation pump 29. Return temperature detection sensor G Hydrogen supply source H Operation Control Unit K Heat Recovery Heat Exchange Unit N fuel cell R2 Human operation command unit S4 Return Point Temperature Detection Sensor S5 Bottom Temperature Sensor T Hot water storage tank U Water Flow Section

Claims

1. The system includes a fuel cell that generates electricity using hydrogen, a sealed hot water storage tank that stores hot water and is supplied with water from the bottom, a hot water circulation path connecting the bottom and top of the hot water storage tank via a heat recovery heat exchange unit that recovers waste heat from the fuel cell, a heat storage circulation pump that circulates hot water through the hot water circulation path in a manner that returns the hot water taken from the bottom of the hot water storage tank to the top of the hot water storage tank, a heating terminal that uses the hot water stored in the hot water storage tank for heating, and an operation control unit. The operation control unit is configured to perform a waste heat recovery type hot water storage treatment by controlling the operation of the heat storage circulation pump in such a manner that, in order to store hot water in the hot water storage tank in a state in which a temperature stratification is formed in the operating state of the fuel cell, the amount of hot water circulated through the hot water flow circulation path so that the temperature of the hot water supplied to the upper part of the hot water storage tank through the hot water flow circulation path reaches a target temperature. A hot water consumption circuit is provided, comprising a hot water supply path that supplies hot water taken from the top of the hot water storage tank to a heat exchanger for heat dissipation, and a return path that returns the hot water that has undergone heat exchange in the heat exchanger back to the hot water storage tank. A consumption circulation pump is provided to circulate hot water through the aforementioned hot water consumption circuit. A heat transfer medium circulation path is provided between the heat dissipation heat exchanger and the heating terminal for circulating the heat transfer medium. A combined heat and power system configured such that the operation control unit performs a hot water consumption process that controls the operation of the consumption circulation pump in a manner that circulates hot water at a set target flow rate through the hot water consumption circuit, and also performs a heating circulation process that circulates a heat medium through the heat medium circulation path, The return path is connected to a location below the intermediate position between the bottom and top of the hot water storage tank, and above the bottom. A drainage section is provided to drain water from the top of the hot water storage tank. The operation control unit, If no hot water consumption command has been issued by the manual operation control unit, and the temperature detected by the return point temperature detection sensor, which detects the hot water temperature at the point where the return path is connected in the hot water storage tank, is equal to or greater than the set start temperature, and the heating terminal is operational, the hot water consumption process and the heating circulation process are executed. If the temperature difference between the temperature detected by the return point temperature detection sensor and the temperature detected by the return temperature detection sensor, which detects the temperature of the hot water flowing through the return path, is equal to or greater than the set value, the set target flow rate is corrected to a reduced target amount. A combined heat and power system that, when no hot water consumption command has been issued by the manual operation control unit, the temperature detected by the lower temperature sensor located above the bottom of the hot water storage tank and below the connection point of the return path detects a set high temperature, and the operation of the heating terminal is not possible, performs drainage processing by draining water from the drainage unit.

2. The combined heat and power system according to claim 1, wherein the operation control unit executes the hot water consumption process when a hot water consumption command is issued by the manual operation command unit, and sets the set target flow rate to the reduction target amount when the temperature difference between the temperature detected by the return point temperature detection sensor and the temperature detected by the return temperature detection sensor is greater than or equal to the set value.

3. The combined heat and power system according to claim 2, wherein when the operation control unit detects a set high temperature in the lower temperature sensor, it performs a drainage process to drain water in the drainage unit.

4. The combined heat and power system according to any one of claims 1 to 3, wherein a hot water flow section is provided inside the hot water storage tank to cause hot water from the return path to flow from multiple locations in the width direction of the hot water storage tank toward the bottom of the tank.

5. The combined heat and power system according to any one of claims 1 to 4, wherein a hydrogen supply source is provided to supply pure hydrogen to the fuel cell.

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