Fuel cell system

Abstract

To provide a fuel cell system for reducing deterioration in merit that a user can receive.SOLUTION: A fuel cell system comprises a fuel cell unit in system interconnection with a power system, a power conversion unit for converting generation power generated by the fuel cell unit to output output power, a power load unit to which power can be supplied from at least one of the power system and the power conversion unit, a power consumption unit capable of consuming the output power from the power conversion unit by heating hot water, and a controlling unit. The controlling unit determines existence of heat demand at a facility in which the fuel cell unit is installed when a need of suppressing inverse load flow power to be equal to or lower than a predetermined value; when the existence of the heat demand is determined, controls operation of the fuel cell unit while actuating the power consumption unit and making the power consumption unit consume power corresponding to the heat demand to make the inverse load flow power be equal to or lower than the predetermined value; and when no existence of the heat demand is determined, controls operation of the fuel cell unit without actuating the power consumption unit to make the inverse load flow power be equal to or lower than the predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a fuel cell system that outputs power in response to fluctuations in grid voltage. The fuel cell system disclosed in Patent Document 1 includes a fuel cell that can be connected to a grid power supply, a power conversion device that converts the output power from the fuel cell into AC power, a power consumption device (surplus power absorption heater) that consumes the output power of the fuel cell, and a control device that controls the fuel cell, the power conversion device, and the power consumption device. When the grid voltage is greater than a first determination value, the control device reduces the output power from the power conversion device by adjusting the amount of output power consumed by the power consumption device while maintaining the output power of the fuel cell at a constant output value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-207289 Summary of the Invention [Problem to be solved by the invention]

[0004] In the fuel cell system disclosed in Patent Document 1, when the grid voltage is greater than a first determination value (voltage rise suppression threshold), the power consumption of a power consumption device (surplus power absorption heater) is increased to reduce the output power from the power conversion device. However, in the above fuel cell system, power other than the power (heat) required by the user is consumed, which may result in energy loss. In recent years, technology has been proposed that suppresses the power generation output of a fuel cell without increasing power consumption. However, with this technology, the power generation efficiency decreases as the power generation output decreases, which may reduce the overall efficiency (power generation efficiency and heat exhaust efficiency), thereby potentially compromising the benefits that users can enjoy. For this reason, a fuel cell system that can reduce the loss of benefits that users can enjoy is desired.

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

[0006] The fuel cell system according to the present invention, which achieves the above object, has the following characteristic configuration: a fuel cell unit that is interconnected with an electric power grid; a power conversion unit that converts the power generated by the fuel cell unit and outputs output power; a power load unit capable of receiving power supply from at least one of the power grid and the power conversion unit; a hot water tank for storing hot water that stores exhaust heat from the fuel cell unit, and a heat storage unit having a hot water circulation circuit connected to the hot water tank and through which the hot water circulates; a power consumption unit disposed in the hot and cold water circulation circuit and capable of consuming the output power from the power conversion unit by heating the hot and cold water; a control unit that controls operations of the fuel cell unit, the power conversion unit, the heat storage unit, and the power consumption unit, a fuel cell system capable of reverse flowing the power not consumed by the power load out of the output power to the power grid as reverse flow power, When it becomes necessary to suppress the reverse flow power to below a predetermined value, the control unit determines whether there is a demand for heat in the facility in which the fuel cell unit is installed, and if it determines that there is a demand for heat, it operates the power consumption unit to consume power corresponding to the heat demand while controlling the operation of the fuel cell unit to suppress the reverse flow power to below the predetermined value, and if it determines that there is no demand for heat, it controls the operation of the fuel cell unit without operating the power consumption unit to suppress the reverse flow power to below the predetermined value.

[0007] According to the above characteristic configuration, even when it becomes necessary to suppress the reverse flow power, if there is a demand for heat, the power consumption unit can consume part or all of the reverse flow power to meet the heat demand, thereby reducing the decrease in the power generated by the fuel cell unit. Furthermore, when it becomes necessary to suppress the reverse flow power to a predetermined value or less, the control unit determines whether there is a demand for heat, and only when it determines that there is a demand for heat, it activates the power consumption unit to consume power corresponding to the heat demand and heat water (stores heat in the heat storage unit). In other words, it is possible to activate the power consumption unit depending on whether there is a demand for heat. This reduces the wasteful consumption of power that would be caused by activating the power consumption unit when there is no demand for heat. Therefore, it is possible to reduce the loss of benefits that users can enjoy.

[0008] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The need to suppress the reverse flow power to below the predetermined value occurs when the control unit receives an output suppression command including an instruction to suppress the reverse flow power so that the reverse flow power becomes zero because the receiving point voltage between the power system and the power conversion unit exceeds a predetermined set value, and when the control unit receives a reduction command including an instruction to suppress the reverse flow power by lowering the receiving point voltage so that the reverse flow power becomes the predetermined value.

[0009] According to the above characteristic configuration, it is possible to respond to both an output reduction command, which is an instruction to reduce power generation output (reverse flow power) from a general electricity transmission and distribution company, and a reduction command, which is an instruction to reduce power generation output (reverse flow power) from a management device (resource aggregator) in a VPP (Virtual Power Plant), which aggregates multiple facilities and multiple power supply devices using a management device to function like a single power plant.

[0010] Another characteristic configuration of the fuel cell system according to the present invention is as follows: When the control unit determines that there is a demand for heat, it sets the amount of power consumed by the power consumption unit when it operates, based on the power that the power consumption unit can consume and the power required to satisfy the heat demand.

[0011] According to the above characteristic configuration, the power consumption of the power consumption unit is set based on the power that the power consumption unit can consume and the power required to meet the heat demand, thereby reducing the loss of benefits that the user can enjoy.

[0012] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit determines that there is a heat demand when hot water is being dispensed from the hot water tank, and determines that there is no heat demand when hot water is not being dispensed.

[0013] According to the above characteristic configuration, the presence or absence of heat demand is determined depending on the hot water being dispensed, so the power consumption unit can consume power efficiently, thereby reducing the loss of benefits that can be enjoyed by the user.

[0014] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit determines that there is a heat demand when there is a plan to dispense hot water from the hot water tank, and determines that there is no heat demand when there is no plan to dispense hot water.

[0015] According to the above characteristic configuration, the presence or absence of heat demand is determined based on the schedule of whether or not hot water is scheduled to be dispensed, so the power consumption unit can consume power efficiently, thereby reducing the loss of benefits that users can enjoy.

[0016] Another characteristic configuration of the fuel cell system according to the present invention is as follows: Further provided is a hot water temperature detection unit that detects the temperature of the hot water stored in the hot water tank, The control unit determines that there is a heat demand when the temperature of the hot water detected by the hot water temperature detection unit is below the hot water temperature threshold, and determines that there is no heat demand when the temperature of the hot water is not below the hot water temperature threshold.

[0017] According to the above characteristic configuration, the presence or absence of heat demand is determined based on whether the temperature of the hot water is at the hot water temperature threshold, so that the power consumption unit can consume power efficiently and the loss of benefits that the user can enjoy can be reduced.

[0018] Another characteristic configuration of the fuel cell system according to the present invention is as follows: a low-temperature fluid flow path through which the low-temperature fluid flows into the hot water tank; a cryogenic fluid temperature detection unit that detects the temperature of the cryogenic fluid flowing through the cryogenic fluid flow path, The control unit determines that there is a heat demand when the temperature of the cryogenic fluid measured by the cryogenic fluid temperature detection unit is less than a cryogenic fluid threshold value, and determines that there is no heat demand when the temperature of the cryogenic fluid is equal to or greater than the cryogenic fluid threshold value.

[0019] According to the above characteristic configuration, the presence or absence of heat demand is determined based on the temperature of the low-temperature fluid measured by the low-temperature fluid temperature detection unit, so that the power consumption unit can consume power efficiently, thereby reducing the loss of benefits that users can enjoy. [Brief explanation of the drawings]

[0020] [Figure 1]1 is a schematic configuration diagram showing a fuel cell system according to an embodiment; [Figure 2] 4 is a flowchart illustrating an output suppression response process according to the embodiment. [Figure 3] 4 is a flowchart showing a heater activation process according to the embodiment. [Figure 4] 10 is a flowchart illustrating an output suppression response process according to another embodiment. [Figure 5] 10 is a flowchart showing a heater activation process according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] A fuel cell system 100 according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the fuel cell system 100. The fuel cell system 100 according to this embodiment is installed in a facility (hereinafter referred to as a power generation facility) that is configured to be able to be interconnected with an electric power company's power system (commercial power source). The fuel cell system 100 can reverse flow, to the power grid, the generated power that is not consumed at the power generation facility where the fuel cell system 100 is installed, as reverse flow power.

[0022] [Fuel cell system] As shown in FIG. 1, the fuel cell system 100 includes a hot module 1, a reforming water supply unit 2, a raw fuel supply unit 3, an oxidant gas supply unit 4, a heat exchange unit 5, a heat storage unit 6, an electrical unit 7, and a control device 10 (an example of a control unit).

[0023] [Hot Module] The hot module 1 is a fuel cell module that generates electricity by reacting hydrogen and oxygen. The hot module 1 has an inner container 11, a vaporization section 12, a reforming section 13, a cell stack 14 (an example of a fuel cell section), a combustion section 15, and a combustion catalyst section 16.

[0024] The inner container 11 has heat insulating properties and houses the vaporization section 12, the reforming section 13, the cell stack 14, the combustion section 15, and the combustion catalyst section 16. The inner container 11 has an exhaust port 111 formed therein.

[0025] A reforming water supply unit 2, a raw fuel supply unit 3, and an oxidizing gas supply unit 4 are connected to the hot module 1, and reforming water, raw fuel (raw fuel gas), and oxidizing gas (oxidizer) are supplied to the hot module 1. In this embodiment, the reforming water and raw fuel are supplied to the vaporization unit 12, and the oxidizing gas is supplied to the cell stack 14.

[0026] [Vaporization section] In addition to the reforming water and raw fuel, combustion heat generated in the combustion section 15 is supplied to the vaporization section 12. The vaporization section 12 vaporizes the reforming water by utilizing the combustion heat to generate steam. In this embodiment, the vaporization section 12 supplies a mixed gas obtained by mixing the raw fuel with steam vaporized from the reforming water to the reforming section 13.

[0027] [Modification section] In addition to the mixed gas supplied from the vaporization unit 12, combustion heat generated in the combustion unit 15 is also supplied to the reforming unit 13. The reforming unit 13 uses the combustion heat to generate fuel gas by steam reforming the mixed gas (raw fuel). The fuel gas generated in the reforming unit 13 is supplied to the cell stack 14.

[0028] [Cell stack] The cell stack 14 is made up of a plurality of cells C and is interconnected with the power grid. In this embodiment, the cells C are solid oxide fuel cells, and are made up of an anode (combustion electrode), a cathode (air electrode), and an electrolyte.

[0029] Fuel gas and oxidant gas are supplied to cell C, and cell C generates power based on the fuel gas and oxidant gas. Specifically, cell C generates power by chemically reacting hydrogen contained in the fuel gas with oxygen contained in the oxidant gas. The fuel gas and oxidant gas not used for power generation are discharged as off-gas (excess gas).

[0030] [Combustion section] The combustion section 15 is supplied with off-gas discharged from the cell stack 14 and generates combustion heat by combusting the off-gas. The combustion heat generated in the combustion section 15 increases the temperature of the internal space of the inner container 11. The combustion section 15 also discharges combustion exhaust gas along with the fuel of the off-gas. The combustion exhaust gas is led to the combustion catalyst section 16 arranged in the exhaust port 111.

[0031] [Combustion catalyst section] The combustion catalyst section 16 uses oxygen to catalytically combust hydrogen, carbon monoxide, and the like contained in the combustion exhaust gas. The catalytically combusted combustion exhaust gas is discharged to the outside of the inner vessel 11.

[0032] [Reformed Water Supply Department] The reforming water supply unit 2 supplies reforming water to the hot module 1. The reforming water is, for example, tap water from which impurities have been removed. The reforming water supply unit 2 includes a reforming water supply passage L1, a water tank 21, and a pump 22.

[0033] The water tank 21 stores the reforming water. The pump 22 pumps the reforming water stored in the water tank 21. As a result, the reforming water is supplied to the hot module 1 via the reforming water supply passage L1.

[0034] [Raw and fuel supply department] The raw fuel supply unit 3 supplies raw fuel containing hydrocarbons to the hot module 1. The raw fuel is, for example, city gas, LP gas, or the like.

[0035] The raw fuel supply unit 3 has a raw fuel supply path L2, a solenoid valve 31, a fuel flow meter 32, a gas blower 33, and a desulfurization unit 34. The solenoid valve 31 can adjust the flow rate of the raw fuel flowing through the raw fuel supply path L2. The fuel flow meter 32 measures the flow rate of the raw fuel flowing through the raw fuel supply path L2. The gas blower 33 supplies the raw fuel to the hot module 1 via the raw fuel supply path L2. The desulfurization unit 34 is disposed upstream of the hot module 1 in the flow direction of the raw fuel and removes sulfur contained in the raw fuel. As a result, the raw fuel from which sulfur has been removed is supplied to the hot module 1. The amount of raw fuel supplied to the hot module 1 per unit time is adjusted by controlling the operation of the solenoid valve 31 and / or the gas blower 33.

[0036] [Oxidant gas supply unit] The oxidant gas supply unit 4 supplies an oxidant gas containing oxygen to the hot module 1. The oxidant gas supply unit 4 has an oxidant gas supply path L3, an oxidant gas blower 41, and an oxidant gas flow meter 42. The oxidant gas blower 41 supplies the oxidant gas to the hot module 1 via the oxidant gas supply path L3. The oxidant gas flow meter 42 measures the flow rate of the oxidant gas flowing through the oxidant gas supply path L3. The amount of oxidant gas supplied to the hot module 1 per unit time is adjusted by controlling the operation of the oxidant gas blower 41.

[0037] [Heat exchange section] The heat exchange unit 5 has a combustion exhaust gas passage L4 and a heat exchanger 51. The combustion exhaust gas passage L4 is connected to the exhaust port 111 of the inner container 11 and the heat exchanger 51. The combustion exhaust gas is supplied from the exhaust port 111 to the heat exchanger 51 via the combustion exhaust gas passage L4.

[0038] In the heat exchanger 51, heat is exchanged between the combustion exhaust gas flowing through the combustion exhaust gas passage L4 and the hot water circulating through the hot water circulation circuit L6 (described later). This cools the combustion exhaust gas and heats the hot water. When the combustion exhaust gas is cooled, the water contained in the combustion exhaust gas condenses and becomes a liquid (liquid phase). The gas phase components in the combustion exhaust gas are discharged to the outside via the combustion exhaust gas passage L4, and the liquid phase components (condensed water) in the combustion exhaust gas are led to the water tank 21 of the reforming water supply unit 2.

[0039] [Heat storage section] The heat storage unit 6 has a hot water tank 61, a hot water circulation pump 62, a hot water cooling unit 63, a hot water flow meter 64, a hot water temperature sensor 65 (an example of a hot water temperature detection unit), a heater 66 (an example of a power consumption unit), and a water supply temperature sensor 67 (an example of a low-temperature fluid temperature detection unit). The heat storage unit 6 also has a hot water circulation circuit L6, a water supply flow path L7 (an example of a low-temperature fluid flow path), and a hot water outlet flow path L8.

[0040] The hot water tank 61 stores hot water. In this embodiment, the hot water can store exhaust heat from the cell stack 14. The lower part of the hot water tank 61 is connected to the water supply flow path L7 to receive the water supply (tap water flows in), and the upper part is connected to the hot water outlet flow path L8 to output the hot water (hot water flows out). The lower and upper parts of the hot water tank 61 are connected to the hot water circulation circuit L6. The hot water circulation pump 62 circulates the hot water between the hot water tank 61 and the heat exchange unit 5. More specifically, the hot water circulation pump 62 pumps the hot water from the lower part of the hot water tank 61 through the heat exchanger 51 to the upper part of the hot water tank 61 in the hot water circulation circuit L6. In other words, the hot water flows out from the lower part of the hot water tank 61 to the hot water circulation circuit L6, and the hot water heated by the heat exchange unit 5 is returned to the upper part of the hot water tank 61.

[0041] The hot water cooling unit 63 cools the hot water upstream of the heat exchange unit 5 in the direction of hot water flow. The hot water cooling unit 63 includes, for example, a radiator and a heat dissipation fan. The hot water flow meter 64 measures the flow rate of hot water flowing through the hot water circulation circuit L6.

[0042] The hot water temperature sensor 65 detects the temperature of hot water flowing through the hot water circulation circuit L6. In this embodiment, the hot water temperature sensor 65 includes a first hot water temperature sensor 651 and a second hot water temperature sensor 652. The first hot water temperature sensor 651 is arranged upstream of the heat exchanger 51 (downstream of the hot water tank 61) in the direction of hot water flow through the hot water circulation circuit L6, and detects the temperature of the hot water flowing into the heat exchanger 51. The second hot water temperature sensor 652 is arranged downstream of the heat exchanger 51 (upstream of the hot water tank 61) in the direction of hot water flow through the hot water circulation circuit L6, and detects the temperature of the hot water flowing out of the heat exchanger 51. The hot water circulation pump 62 controls the flow rate of hot water flowing through the hot water circulation circuit L6 so that the temperature of the hot water after exhaust heat recovery, detected by the second hot water temperature sensor 652, becomes a preset target temperature (e.g., 65°C). The target temperature is set arbitrarily by the designer of the fuel cell system 100 or the like.

[0043] The heater 66 heats the hot and cold water flowing through the hot and cold water circulation circuit L6. In this embodiment, the heater 66 is composed of multiple resistance heaters and is configured to be able to switch power consumption in stages between minimum power consumption (0 W) and maximum power consumption (e.g., 400 W). The operation (activation or deactivation) of the heater 66 is controlled by the control device 10.

[0044] The water supply temperature sensor 67 detects the temperature of tap water (an example of a low-temperature fluid) flowing into the hot water tank 61. Each of the first hot water temperature sensor 651, the second hot water temperature sensor 652, and the water supply temperature sensor 67 transmits information indicating the detected temperature to the control device 10.

[0045] [Electrical equipment, power conversion, power load measurement] The electrical equipment unit 7 has a power conversion unit 71 and a power load measurement unit 72. The power conversion unit 71 is electrically connected to the commercial power supply, the power load measurement unit 72, and the power load unit R via a second power line LE2. The power conversion unit 71 is electrically connected to the cell stack 14 via a first power line LE1, and is supplied with power generated by the cell stack 14 (hereinafter referred to as generated power). The power conversion unit 71 is composed of an inverter, and converts the generated power from a DC voltage to an AC voltage and outputs it as output power. The power conversion unit 71 also converts the generated power to a voltage and frequency equal to those of the received power received from the commercial power supply, and outputs the converted power as output power.

[0046] The power load measuring unit 72 measures the load power in the power load unit R. Information indicating the load power measured by the power load unit R is transmitted to the control device 10. In this embodiment, the power load measuring unit 72 is arranged on the second power line LE2 between the power load unit R and the power conversion unit 71 and commercial power supply.

[0047] [Power load section] The power load unit R can receive power from at least one of the output power (power generated by the hot module 1) output from the power conversion unit 71 and a commercial power source, and consumes at least one of the output power and the power supplied from the commercial power source as load power. The power load unit R is composed of, for example, home appliances used in the power generation facility. Note that the power load unit R may also include auxiliary equipment such as the pump 22 and gas blower 33 provided in the fuel cell system 100.

[0048] In this embodiment, a heater 66 is connected on the second power line LE2 between the power conversion unit 71 and the power load unit R and the commercial power supply, and the heater 66 can consume part or all of the surplus power remaining after subtracting the load power from the output power. If reverse flow of power to the commercial power supply is possible, the power remaining after subtracting the load power from the output power, or the power remaining after subtracting the load power and the power consumed by the heater 66 from the output power, is reverse flowed to the commercial power supply via the second power line LE2 as reverse flow power.

[0049] [Control device] The control device 10 is composed of a microcontroller including a processor, a semiconductor memory, etc. Program data for executing the processes described below is stored in the semiconductor memory of the control device 10. The control device 10 controls the operations of the hot module 1, the reforming water supply unit 2, the raw fuel supply unit 3, the oxidant gas supply unit 4, the heat exchange unit 5, the heat storage unit 6, and the electrical equipment unit 7.

[0050] In this embodiment, the control device 10 controls the operation of the cell stack 14 so that the power generation output becomes the rated output (for example, 700 W) during normal operation. In this embodiment, the control device 10 also functions as an automatic voltage regulator (AVR) that can suppress the power generation output of the cell stack 14.

[0051] During normal operation, the control device 10 causes a reverse flow of power obtained by subtracting load power from output power (power generation output). When it becomes necessary to suppress the reverse flow power to a predetermined value or less, the control device 10 executes output suppression response processing. More specifically, when an output suppression command is received because the voltage at the power receiving point between the commercial power source and the power conversion unit 71 exceeds a predetermined set value, the control device 10 executes output suppression response processing to suppress the reverse flow power. The output suppression command is a command that includes an instruction to suppress the reverse flow power so that the reverse flow power becomes zero.

[0052] [Output suppression response processing] The output suppression response process will be described below with reference to Figures 2 and 3. Figure 2 is a flowchart showing the output suppression response process that is executed when an output suppression command is received, and Figure 3 is a flowchart showing the heater operation process that is executed when an output suppression command is received.

[0053] In the output suppression response process, the control device 10 determines whether or not the output power (power generation output) is greater than the load power (step S101).

[0054] When the control device 10 determines that the output power is greater than the load power (step S101; Yes), it determines whether or not there is a heat demand in the power generation facility in which the fuel cell system 100 is installed (step S103). If the determination conditions are met, the control device 10 determines that there is a heat demand (step S103; Yes), and if the determination conditions are not met, it determines that there is no heat demand (step S103; No). The determination conditions are set in advance by a designer or the like.

[0055] In this embodiment, the judgment conditions include the following conditions (1) to (4). The control device 10 judges that there is a heat demand if any of the conditions (1) to (4) is met, and judges that there is no heat demand if none of the conditions is met. However, the control device 10 may also judge that there is a heat demand if all of two or more conditions arbitrarily combined from the conditions (1) to (4) are met, and judge that there is no heat demand if all of the two or more conditions arbitrarily combined are not met.

[0056] Condition (1) is a condition that hot water is being dispensed from the hot water tank 61. Whether hot water is being dispensed or not is determined based on the value measured and output by a flow meter (not shown) arranged in the hot water outlet flow path L8 (see Figure 1). Condition (2) is a condition that hot water is scheduled to be dispensed. Information indicating the scheduled hot water dispense is stored, for example, in a semiconductor memory of the control device 10, and whether hot water is scheduled to be dispensed or not is determined based on the information stored in the semiconductor memory. Condition (3) is a condition that the temperature of the hot water (hot water flowing through the hot water circulation circuit L6) detected by the hot water temperature sensor 65 is equal to or lower than the hot water temperature threshold. Condition (4) is a condition that the temperature of the tap water measured by the supply water temperature sensor 67 is lower than the low-temperature fluid threshold.

[0057] When the control device 10 determines that there is no heat demand (step S103; No), it executes an output suppression process (step S105) to control (suppress) the power generated by the hot module 1 (cell stack 14) without operating the heater 66, so that the reverse flow power is below a predetermined value (zero when an output suppression command is received), and then proceeds to step S109.

[0058] On the other hand, when the control device 10 determines that there is a heat demand (step S103; Yes), it executes a heater activation process (see FIG. 3) to activate the heater 66 (step S107). In detail, the control device 10 activates the heater 66 to cause the heater 66 to consume power corresponding to the heat demand, while controlling the operation of the cell stack 14 so that the reverse flow power becomes equal to or less than a predetermined value (zero when an output suppression command is received).

[0059] 3, in the heater operation process, the control device 10 determines whether the first power obtained by subtracting the load power from the output power is equal to or greater than the required power (required amount of heat) (step S201). The required power is calculated as the power required by the heater 66 to obtain the required amount of heat required by the heat demand. For example, if the output power is 700 W, the load power is 300 W, and the required power is 400 W, if the heater 66 can consume all of the required power, there is no need to suppress the power generated by the cell stack 14. However, even if the heater 66 cannot consume all of the required power, if the heater 66 can consume a portion of the required power, then suppression of the power generated by the cell stack 14 can be small.

[0060] When the control device 10 determines that the first power is equal to or greater than the required power (required heat amount) (step S201; Yes), it determines whether the maximum power consumption of the heater 66 (maximum output of the heater 66) is equal to or less than the required power (step S203).

[0061] When the control device 10 determines that the maximum power consumption of the heater 66 is equal to or less than the required power (step S203; Yes), it operates the heater 66 so as to achieve the maximum power consumption (maximum output) (step S205).

[0062] On the other hand, when the control device 10 determines that the maximum power consumption of the heater 66 is not equal to or less than the required power (step S203; No), it operates the heater 66 so that the power consumption (output) becomes equal to the required power (step S207).

[0063] Furthermore, when the control device 10 determines in step S201 that the first power obtained by subtracting the load power from the output power is not equal to or greater than the required power (required heat amount) (step S201; No), it determines whether the first power is equal to or less than the power consumption of the heater 66 (step S209).

[0064] If the control device 10 determines that the first power is not less than the power consumption of the heater 66 (step S209; No), it determines whether the power consumption of the heater 66 is at its maximum (step S211), and if the control device 10 determines that the power consumption of the heater 66 is not at its maximum (step S211; No), it increases the output of the heater 66 (step S213) and returns to step S209.

[0065] Furthermore, when it is determined that the power consumption of the heater 66 is at its maximum (step S211; Yes), when the heater 66 is operated at an output (maximum output) that results in the maximum power consumption (step S205), when the heater 66 is operated so that the power consumption (output) is equal to the required power (step S207), or when it is determined that the first power is equal to or less than the power consumption of the heater 66 (step S209; Yes), the control device 10 determines whether the output power is equal to or less than the total power of the load power and the heater power consumption (step S215).

[0066] When the control device 10 determines that the output power is not equal to or less than the total power (step S215; No), it executes an output suppression process to suppress the power generation output of the hot module 1 (step S217), and returns to step S215.

[0067] On the other hand, if it is determined that the output power is equal to or less than the total power (step S215; Yes), the process proceeds to step S109 shown in FIG.

[0068] In step S109, the control device 10 determines whether the output reduction command continues (whether the output reduction command is continuously received) (step S109).

[0069] The control device 10 determines whether the output suppression command is continuing (step S109), and if it determines that the output suppression command is continuing (step S109; Yes), it returns to step S101. On the other hand, if it determines that the output suppression command is not continuing (step S109; No), it returns to normal operation (step S111) and ends the process.

[0070] As described above, according to this embodiment, even when it becomes necessary to suppress reverse flow power, if there is a demand for heat, the heater 66 can consume part or all of the reverse flow power to meet the demand for heat, thereby reducing a decrease in the power generation of the cell stack 14. When an output suppression command is received and the output power (generated power) is equal to or greater than the load power, the control device 10 determines whether there is a demand for heat, and only when it determines that there is a demand for heat, the control device 10 activates the heater 66 to heat water (converts the electrical energy of the output power into thermal energy and stores the heat in the thermal storage unit 6). In other words, the heater 66 can be activated depending on whether there is a demand for heat. This reduces the wasteful consumption of power that would otherwise be caused by activating the heater 66 when there is no demand for heat. This reduces the loss of benefits that users can enjoy.

[0071] <Another embodiment> The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention.

[0072] (1) For example, when the fuel cell system 100 is participating in a VPP (Virtual Power Plant), if the voltage at the receiving point between the commercial power source and the power conversion unit 71 exceeds a predetermined set value and a reduction command is received from the management device, the control device 10 executes output reduction response processing to reduce the reverse flow power. The reduction command is a command that includes an instruction to reduce the receiving voltage to reduce the reverse flow power.

[0073] 4 and 5, in the output suppression response process, the control device 10 receives a command value for the output power from the management device, and determines whether or not a first power obtained by subtracting the load power from the output power is equal to the command value (step S301), and if it determines that the first power is equal to the command value (step S301; Yes), it determines whether or not there is a heat demand (step S303), similar to step S103 described with reference to Fig. 2. Note that Fig. 4 is a flowchart showing the output suppression response process executed when a reduction command is received, and Fig. 5 is a flowchart showing the heater operation process executed when a reduction command is received.

[0074] When the control device 10 determines that there is no heat demand (step S303; No), it executes an output suppression process to suppress the power generation output of the hot module 1 so that the first power (the value obtained by subtracting the load power from the output power) becomes equal to the command value (step S305), and proceeds to step S309.

[0075] On the other hand, if it is determined in step S303 that there is a heat demand (step S303; Yes), a heater activation process (see FIG. 5) is executed to activate the heater 66 (step S307).

[0076] As shown in FIG. 5, in the heater operation process, it is determined whether or not the second power obtained by subtracting the load power and the command value from the output power is equal to or greater than the required power (step S401).

[0077] When the control device 10 determines that the second power is equal to or greater than the required power (step S401; Yes), it determines whether the maximum power consumption of the heater 66 (maximum output of the heater 66) is equal to or less than the required power (step S403).

[0078] If the control device 10 determines that the maximum power consumption of the heater 66 is equal to or less than the required power (step S403; Yes), it operates the heater 66 at an output (maximum output) that results in the maximum power consumption (step S405). On the other hand, if the control device 10 determines that the maximum power consumption of the heater 66 is not equal to or less than the required power (step S403; No), it operates the heater 66 so that the power consumption (output) is equal to the required power (step S407).

[0079] Furthermore, when the control device 10 determines in step S401 that the second power (power obtained by subtracting the load power and the command value from the output power) is not equal to or greater than the required power (step S401; No), it determines whether the second power is equal to the power consumption of the heater 66 (step S409).

[0080] If the control device 10 determines that the second power is not equal to the power consumption of the heater 66 (step S409; No), it determines whether the power consumption of the heater 66 is at its maximum (step S411), and if it determines that the power consumption of the heater 66 is not at its maximum (step S411; No), it increases the output of the heater 66 (step S413) and returns to step S409.

[0081] Furthermore, if it is determined that the power consumption of the heater 66 is at its maximum (step S411; Yes), if the heater 66 is operated at an output (maximum output) that results in the maximum power consumption (step S405), if the heater 66 is operated so that the power consumption (output) is equal to the required power (step S407), or if it is determined that the second power is equal to the power consumption of the heater 66 (step S409; Yes), the control device 10 determines whether the third power, which is the output power minus the load power and the heater power consumption, is equal to the command value (step S415).

[0082] When the control device 10 determines that the third electric power is not equal to the command value (step S415; No), it executes the output suppression process (step S417) and returns to step S415.

[0083] On the other hand, when the control device 10 determines that the third power is equal to the command value (step S415; Yes), the process proceeds to step S309 described with reference to FIG.

[0084] In step S309 of FIG. 4, the control device 10 determines whether the lowering command is continuing (whether the lowering command is being continuously received) (step S309).

[0085] If the control device 10 determines that the lowering command is continuing (step S309; ​​Yes), the process returns to step S301. On the other hand, if the control device 10 determines that the lowering command is not continuing (step S309; ​​No), the process returns to normal operation (step S311) and ends the process.

[0086] (2) The configuration of the hot module 1 in the above embodiment is an example, and the configuration within the hot module 1 can be changed as appropriate. For example, the raw fuel may be directly supplied to the reforming unit 13 from the raw fuel supply unit 3 without passing through the vaporization unit 12.

[0087] (3) The present invention is also applicable to fuel cells other than solid oxide fuel cells. [Industrial Applicability]

[0088] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0089] 6: Heat storage part 10: Control device (control unit) 14: Cell stack (fuel cell section) 61: Hot and cold water tank 65: Hot water temperature sensor (hot water temperature detection part) 66: Heater (power consumption part) 67: Water supply temperature sensor (low temperature fluid temperature detection part) 71: Power conversion section 100: Fuel cell system 651: First hot and cold water temperature sensor 652: Second hot and cold water temperature sensor L6: Soup circulation loop L7: Water supply path (low-temperature fluid path) R: Power load unit

Claims

1. a fuel cell unit that is interconnected with an electric power grid; a power conversion unit that converts the power generated by the fuel cell unit and outputs output power; a power load unit capable of receiving power supply from at least one of the power grid and the power conversion unit; a hot water tank for storing hot water that stores exhaust heat from the fuel cell unit, and a heat storage unit having a hot water circulation circuit connected to the hot water tank and through which the hot water circulates; a power consumption unit disposed in the hot and cold water circulation circuit and capable of consuming the output power from the power conversion unit by heating the hot and cold water; a control unit that controls operations of the fuel cell unit, the power conversion unit, the heat storage unit, and the power consumption unit, a fuel cell system capable of reverse flowing the power not consumed by the power load out of the output power to the power grid as reverse flow power, When it becomes necessary to suppress the reverse flow power to a predetermined value or less, the control unit determines whether there is a demand for heat in the facility in which the fuel cell unit is installed, and if it determines that there is a demand for heat, it operates the power consumption unit to consume power corresponding to the heat demand while controlling the operation of the fuel cell unit so that the reverse flow power is to be equal to or less than the predetermined value, and if it determines that there is no demand for heat, it controls the operation of the fuel cell unit without operating the power consumption unit so that the reverse flow power is to be equal to or less than the predetermined value, in this fuel cell system.

2. 2. The fuel cell system according to claim 1, wherein a need arises for suppressing the reverse flow power to be equal to or less than the predetermined value when the control unit receives an output suppression command including an instruction to suppress the reverse flow power so that the reverse flow power becomes zero because a voltage at a receiving point between the power grid and the power conversion unit exceeds a predetermined set value, and when the control unit receives a reduction command including an instruction to suppress the reverse flow power so that the reverse flow power becomes equal to or less than the predetermined value by lowering the voltage at the receiving point.

3. 2. The fuel cell system according to claim 1, wherein, when the control unit determines that there is a heat demand, the control unit sets the amount of power consumed by the power consumption unit to be operated based on the power that can be consumed by the power consumption unit and the power required to satisfy the heat demand.

4. 2. The fuel cell system according to claim 1, wherein the control unit determines that there is a heat demand when hot water is being dispensed from the hot water tank, and determines that there is no heat demand when hot water is not being dispensed.

5. The fuel cell system of claim 1, wherein the control unit determines that there is a heat demand when there is a schedule for hot water to be dispensed from the hot water tank, and determines that there is no heat demand when there is no schedule for hot water to be dispensed.

6. Further provided is a hot water temperature detection unit that detects the temperature of the hot water stored in the hot water tank, The fuel cell system of claim 1, wherein the control unit determines that there is a heat demand when the hot water temperature detected by the hot water temperature detection unit is below the hot water temperature threshold, and determines that there is no heat demand when the hot water temperature is not below the hot water temperature threshold.

7. a low-temperature fluid flow path through which the low-temperature fluid flows into the hot water tank; a cryogenic fluid temperature detection unit that detects the temperature of the cryogenic fluid flowing through the cryogenic fluid flow path, 2. The fuel cell system of claim 1, wherein the control unit determines that there is a heat demand when the temperature of the cryogenic fluid measured by the cryogenic fluid temperature detection unit is less than a cryogenic fluid threshold value, and determines that there is no heat demand when the temperature of the cryogenic fluid is equal to or greater than the cryogenic fluid threshold value.

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