Power supply system

Abstract

A control unit (50a) shifts an operation state of a power supply system (1a) from a first state to a second state according to increase of surplus power (PS). The surplus power (PS) is surplus power with respect to consumed power (PL) of an electrical load 5, in generated power (PG) of at least one power generation facility (60). In the first state, power is supplied from an electric path (70) to a storage battery facility (30). In the first state, a water electrolysis facility (40) does not perform water electrolysis. In the second state, power is supplied from the electric path (70) to the storage battery facility (30). In the second state, power supplied from the electric path (70) to the water electrolysis facility (40) is larger than power supplied from the electric path (70) to the water electrolysis facility (40) in the first state.

Description

POWER SUPPLY SYSTEM

[0001] The present disclosure relates to a power supply system.

[0002] Patent Literature 1 discloses a power system that allows interchange of power generated by a photovoltaic system between a storage battery and an electrical load.

[0003] JP2009-284586A

[0004] The present disclosure provides a technique suitable for increasing surplus power that can be absorbed, according to increase of the surplus power.

[0005] The present disclosure provides a power supply system including: at least one power generation facility; a storage battery facility; a water electrolysis facility; an electric path connected to the at least one power generation facility, the storage battery facility, and the water electrolysis facility; and a control unit that controls the at least one power generation facility, the storage battery facility, and the water electrolysis facility, in which power is supplied through the electric path to an electrical load, the control unit shifts an operation state of the power supply system, according to increase of surplus power with respect to consumed power of the electrical load in generated power of the at least one power generation facility, from a first state in which power is supplied from the electric path to the storage battery facility, and the water electrolysis facility does not perform water electrolysis, to a second state in which power is supplied from the electric path to the storage battery facility, and power supplied from the electric path to the water electrolysis facility is larger than that in the first state.

[0006] The technique according to the present disclosure is suitable for increasing surplus power that can be absorbed, according to increase of the surplus power.

[0007] Fig. 1 is a configuration diagram illustrating a power supply system according to Embodiment 1.Fig. 2 illustrates a table representing a relationship among surplus power and a storage amount, an operation of a storage battery facility, and execution or non-execution of water electrolysis of a water electrolysis facility, during increase of surplus power, according to Embodiment 1.Fig. 3 illustrates a table representing a relationship among surplus power and a storage amount, an operation of the storage battery facility, and execution or non-execution of water electrolysis of the water electrolysis facility, during decrease of surplus power, according to Embodiment 1.Fig. 4 is a zone diagram illustrating a relationship between surplus power and execution or non-execution of water electrolysis of the water electrolysis facility, according to Embodiment 1.Fig. 5 is a time-series graph illustrating a relationship among surplus power, power supplied from an electric path to the storage battery facility, and power supplied from the electric path to the water electrolysis facility, according to a first specific example.Fig. 6 is a time-series graph illustrating a relationship among surplus power, power supplied from the electric path to the storage battery facility, and power supplied from the electric path to the water electrolysis facility, according to a second specific example.Fig. 7 illustrates a table representing a relationship among surplus power and a storage amount, an operation of the storage battery facility, and execution or non-execution of water electrolysis of the water electrolysis facility, during increase of surplus power, according to Embodiment 2.Fig. 8 illustrates a table representing a relationship among surplus power and a storage amount, an operation of the storage battery facility, and execution or non-execution of water electrolysis of the water electrolysis facility, during decrease of surplus power, according to Embodiment 2.Fig. 9 is a zone diagram illustrating a relationship among surplus power and a storage amount, an operation of the storage battery facility, and execution or non-execution of water electrolysis of the water electrolysis facility, according to Embodiment 2.

[0008] Embodiments will be described below in detail with reference to the drawings. However, unnecessarily detailed description may be omitted. For example, detailed description of already well-known matters or repeated description of the substantially same configurations may be omitted.

[0009] The accompanying drawings and the following description are provided for allowing a person skilled in the art to sufficiently understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0010] (Embodiments) Embodiment 1 will be described below with reference to Fig. 1 to Fig. 6.

[0011] [1-1. Configuration] Fig. 1 is a configuration diagram illustrating a power supply system 1a according to Embodiment 1. The power supply system 1a and a commercial power supply 2 are interconnected. The power supply system 1a supplies power to an electrical load 5.

[0012] The power supply system 1a is a distributed power supply system. The power supply system 1a includes a photovoltaic facility 10, a fuel cell facility 20, a storage battery facility 30, a water electrolysis facility 40, a hydrogen storing section 47, a control unit 50a, an electric path 70, a hydrogen path 75, a distribution board 4, a current sensor 3a, a current sensor 3b, a current sensor 7b, a current sensor 7c, a current sensor 7d, and a current sensor 7e. The current sensor 3a, the current sensor 3b, the current sensor 7b, the current sensor 7c, the current sensor 7d, and the current sensor 7e are, for example, current transformers.

[0013] The electric path 70 includes, for example, one wiring line or a plurality of wiring lines. The hydrogen path 75 includes, for example, one pipe or a plurality of pipes.

[0014] The photovoltaic facility 10 includes a photovoltaic module 11, a DCDC converter 12, and a DCAC inverter 13. DC power generated by the photovoltaic module 11 is converted to DC power having a different voltage by the DCDC converter 12. The converted DC power is converted to AC power by the DCAC inverter 13. The AC power is supplied to the electric path 70.

[0015] The fuel cell facility 20 includes a fuel cell stack 21, a DCDC converter 22, a DCAC inverter 23, and an auxiliary unit 24. The fuel cell facility 20 is, for example, a polymer electrolyte fuel cell (PEFC) facility or a solid oxide fuel cell (SOFC) facility. The fuel cell stack 21 generates power by using oxygen and hydrogen. The auxiliary unit 24 assists the fuel cell stack 21 in power generation.

[0016] The auxiliary unit 24 includes, for example, at least one selected from the group consisting of a first blower and a second blower. The first blower can assist the fuel cell stack 21 in power generation by supplying oxygen to the fuel cell stack 21. The second blower can assist the fuel cell stack 21 in power generation by supplying hydrogen to the fuel cell stack 21.

[0017] The DC power generated by the fuel cell stack 21 is converted to DC power having a different voltage by the DCDC converter 22. The converted DC power is converted to AC power by the DCAC inverter 23. The AC power is supplied to the electric path 70.

[0018] The storage battery facility 30 includes a storage battery module 31, a bidirectional DCDC converter 32, and a DCAC inverter 33. Examples of the storage battery module 31 include a lithium-ion storage battery module, a nickel-hydrogen storage battery module, and a lead storage battery module.

[0019] Power discharged from the storage battery module 31 is converted to DC power having a different voltage by the bidirectional DCDC converter 32. The converted DC power is converted to AC power by the DCAC inverter 33. The AC power is supplied to the electric path 70.

[0020] The AC power supplied from the electric path 70 to the DCAC inverter 33 is converted to DC power. The DC power is converted to DC power having a different voltage by the bidirectional DCDC converter 32. The storage battery module 31 is charged with the converted DC power.

[0021] The water electrolysis facility 40 includes an electrolyzer 41, a transformer rectifier 42, and a heating device 43. The water electrolysis facility 40 is, for example, an alkaline water electrolysis facility or a proton exchange membrane type water electrolysis facility. In the electrolyzer 41, a water electrolysis reaction occurs. Specifically, the electrolyzer 41 contains a catalyst for causing a water electrolysis reaction. Power is supplied from the electric path 70 to the heating device 43. The heating device 43 consumes the power to perform a heating operation. Through the heating operation, water supplied for the water electrolysis reaction in the electrolyzer 41 is heated. Thus, the heating device 43 assists in the water electrolysis reaction by the electrolyzer 41. Power supplied from the electric path 70 to the heating device 43 is, specifically, surplus power. The surplus power will be described below in detail.

[0022] In a first example, the heating device 43 includes an electric heater. Power is supplied to the electric heater from the electric path 70. The electric heater consumes the power to perform a heating operation. Through the heating operation, water supplied for the water electrolysis reaction in the electrolyzer 41 is heated. Thus, the heating device 43 of the first example assists in the water electrolysis reaction.

[0023] In a second example, the heating device 43 includes a heat exchanger and a pump. Power is supplied to the pump from the electric path 70. The pump consumes the power to generate flow of a fluid to the heat exchanger. In the heat exchanger, heat exchange is performed between the fluid and water supplied for the water electrolysis reaction in the electrolyzer 41. Through the heat exchange, water supplied for the water electrolysis reaction is heated. The fluid is, for example, water. Thus, the heating device 43 of the second example assists in the water electrolysis reaction.

[0024] The electrolyzer 41, the hydrogen storing section 47, and the fuel cell stack 21 are connected in this order by the hydrogen path 75. The hydrogen storing section 47 is, for example, a tank.

[0025] AC power supplied from the electric path 70 to the transformer rectifier 42 is converted to DC power. The DC power and water are supplied to the electrolyzer 41. In the electrolyzer 41, electrolysis of the supplied water is performed by using the supplied power. Thus, hydrogen and oxygen are generated.

[0026] Hydrogen generated in the water electrolysis facility 40 is transferred to the hydrogen storing section 47 through the hydrogen path 75, and stored in the hydrogen storing section 47. The stored hydrogen is transferred to the fuel cell stack 21 through the hydrogen path 75, and used for power generation in the fuel cell stack 21.

[0027] In the power supply system 1a, surplus power may be generated. In the power supply system 1a, an energy medium can take the form of power and hydrogen. Specifically, the energy medium is converted from surplus power to hydrogen through the water electrolysis, is temporarily stored in the form of hydrogen, and is thereafter converted again from hydrogen to power by power generation. In the power supply system 1a, surplus power can be absorbed through the conversion of the energy medium.

[0028] The storage battery facility 30 includes a control unit 50b. The photovoltaic facility 10 includes a control unit 50c. The fuel cell facility 20 includes a control unit 50d. The water electrolysis facility 40 includes a control unit 50e.

[0029] The control unit 50a communicates with the current sensor 3a, the current sensor 3b, the control unit 50b, the control unit 50c, the control unit 50d, and the control unit 50e. The control unit 50a generates control signals for controlling the control unit 50b, the control unit 50c, the control unit 50d, and the control unit 50e.

[0030] The control unit 50b receives the control signal from the control unit 50a. The control unit 50b controls the bidirectional DCDC converter 32 and the DCAC inverter 33 according to the control signal. By controlling the bidirectional DCDC converter 32, the storage battery module 31 is controlled so as to be charged, be in a stand-by state, or be discharged. By controlling the DCAC inverter 33, power conversion between DC and AC is performed. Through the controls, power flowing between the storage battery facility 30 and the electric path 70 is controlled.

[0031] Specifically, by controlling the bidirectional DCDC converter 32, charge / discharge power of the storage battery module 31 is controlled In the illustrated example, an inter-terminal voltage V1 of the bidirectional DCDC converter 32 is controlled relative to an inter-terminal voltage V2 of the DCAC inverter 33, whereby charge and discharge of the storage battery module 31 is controlled.

[0032] The control unit 50c receives the control signal from the control unit 50a. The control unit 50c controls the DCDC converter 12 and the DCAC inverter 13 according to the control signal. By controlling the DCDC converter 12, the output voltage of the photovoltaic module 11 is adjusted. Through the adjustment of the output voltage, an operation point of the photovoltaic module 11 is changed, whereby the power generated by the photovoltaic module 11 is adjusted. The operation point of the photovoltaic module 11 refers to a combination of current, voltage, and power generated through power generation by the photovoltaic module 11. Hereinafter, the operation point at which the generated power becomes maximum is referred to as maximum power point. The control unit 50c can also perform maximum power point tracking (MPPT) control of the photovoltaic module 11 by using the DCDC converter 12 such that the operation point of the photovoltaic module 11 becomes the maximum power point. By controlling the DCAC inverter 13, power conversion between DC and AC is performed. Through the controls, power is extracted from the photovoltaic facility 10 to the electric path 70.

[0033] The control unit 50d receives the control signal from the control unit 50a. The control unit 50d controls the DCDC converter 22, the DCAC inverter 23, and the auxiliary unit 24 according to the control signal. By controlling the DCDC converter 22, the output voltage of the fuel cell stack 21 is adjusted. By controlling the DCAC inverter 23, power conversion between DC and AC is performed. The control unit 50d adjusts an amount of hydrogen and / or oxygen to be supplied to the fuel cell stack 21, according to the control signal. Specifically, the supply amount can be adjusted by, for example, adjusting the number of revolutions of the first blower and / or the second blower. By adjusting the supply amount, power generated by the fuel cell stack 21 is adjusted. Through the controls, power is extracted from the fuel cell facility 20 to the electric path 70.

[0034] The control unit 50e receives the control signal from the control unit 50a. The control unit 50e controls the electrolyzer 41, the transformer rectifier 42, and the heating device 43 according to the control signal. Through the controls, power extracted from the electric path 70 to the water electrolysis facility 40, and an amount of hydrogen generated through the water electrolysis by the electrolyzer 41 are controlled. Specifically, the larger the power supplied from the electric path 70 to the water electrolysis facility 40 is, the larger the amount of generated hydrogen can be.

[0035] As is understood from the above description about the storage battery facility 30, the control unit 50a can control charge / discharge power PSBof the storage battery facility 30. The charge / discharge power is charged power or discharged power. A positive value of the charge / discharge power represents discharged power, and the absolute value of a negative value of the charge / discharge power represents charged power.

[0036] Power that can be generated by the photovoltaic facility 10 varies according to an amount of solar radiation. As is understood from the above description about the photovoltaic facility 10, the control unit 50a can control the operation point of the photovoltaic module 11. Through the control of the operation point, the photovoltaic module 11 can be caused to generate the maximum power based on an amount of solar radiation (that is, MPPT control can be performed). Through the control of the operation point, the photovoltaic module 11 can be caused to generate power that is reduced to be less than the maximum power. Thus, the control unit 50a can control generated power PPVof the photovoltaic facility 10.

[0037] The fuel cell stack 21 has rated generation power. As is understood from the above description about the fuel cell facility 20, the control unit 50a can control an amount of hydrogen and / or oxygen to be supplied to the fuel cell stack 21. Thus, the fuel cell stack 21 can be caused to generate rated generation power, and generate power that is reduced to be less than the rated generation power. Thus, the control unit 50a can control generated power PFCof the fuel cell facility 20.

[0038] As is understood from the above description about the water electrolysis facility 40, the control unit 50a can control power flowing from the electric path 70 to the water electrolysis facility 40, that is, consumed power PWEof the water electrolysis facility 40. Specifically, the larger an amount of hydrogen to be generated by the water electrolysis facility 40 is, the larger the power required for the water electrolysis reaction by the water electrolysis facility 40 is. In one example, the larger an amount of hydrogen to be generated by the water electrolysis facility 40 is, the larger an amount of heat to be generated by the heating device 43 is, so that power to be supplied to the heating device 43 is increased. In Embodiment 1, the water electrolysis facility 40 has specifications in which water electrolysis is not performed until power supplied to the water electrolysis facility 40 becomes a first threshold power or more. Specifically, in Embodiment 1, for the water electrolysis in the water electrolysis facility 40, the minimum power to be supplied for the water electrolysis reaction in the electrolyzer 41 and the minimum power to be supplied for the heating operation in the heating device 43 are set. The first threshold power represents power that is larger than or equal to the total of these minimum powers. The first threshold power can also include power for the control unit 50e and power for a not-illustrated temperature sensor. The temperature sensor measures a temperature of water supplied for the water electrolysis reaction.

[0039] The current sensor 7b detects current flowing between the storage battery facility 30 and the electric path 70. Specifically, the current sensor 7b detects charge / discharge current of the storage battery facility 30. The value detected by the current sensor 7b is transmitted from the current sensor 7b to the control unit 50a. The charge / discharge current is a charge current or a discharge current. A positive value of the charge / discharge current represents a discharge current, and the absolute value of a negative value of the charge / discharge current represents a charge current. Voltage in the current path between the storage battery facility 30 and the electric path 70 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate the charge / discharge power PSBof the storage battery facility 30 from the known value and the value detected by the current sensor 7b.

[0040] The current sensor 7c detects current flowing between the photovoltaic facility 10 and the electric path 70. Specifically, the current sensor 7c detects current generated by the photovoltaic facility 10. The value detected by the current sensor 7c is transmitted from the current sensor 7c to the control unit 50a. Voltage in the current path between the photovoltaic facility 10 and the electric path 70 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate the generated power PPVof the photovoltaic facility 10 from the known value and the value detected by the current sensor 7c.

[0041] The current sensor 7d detects current flowing between the fuel cell facility 20 and the electric path 70. Specifically, the current sensor 7d detects current generated by the fuel cell facility 20. The value detected by the current sensor 7d is transmitted from the current sensor 7d to the control unit 50a. Voltage in the current path between the fuel cell facility 20 and the electric path 70 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate the generated power PFCof the fuel cell facility 20 from the known value and the value detected by the current sensor 7d.

[0042] The current sensor 7e detects current flowing between the water electrolysis facility 40 and the electric path 70. Specifically, the current sensor 7e detects current flowing from the electric path 70 to the water electrolysis facility 40. The value detected by the current sensor 7e is transmitted from the current sensor 7e to the control unit 50a. Voltage in the current path between the water electrolysis facility 40 and the electric path 70 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate power flowing from the electric path 70 to the water electrolysis facility 40, that is, the consumed power PWEof the water electrolysis facility 40, from the known value and the value detected by the current sensor 7e.

[0043] Power can flow from the electric path 70 through the distribution board 4 to the electrical load 5. The current sensor 3b detects current flowing into the electrical load 5. Voltage of the electrical load 5 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate power flowing from the electric path 70 to the electrical load 5, that is, consumed power PLof the electrical load 5, from the known value and the value detected by the current sensor 3b.

[0044] In the power supply system 1a, forward power flow and reverse power flow may occur. The forward power flow represents flow of power or current from the commercial power supply 2 to the power supply system 1a, and specifically represents flow of power or current from the commercial power supply 2 to the electric path 70. The reverse power flow represents flow of power or current from the power supply system 1a to the commercial power supply 2, and specifically represents flow of power or current from the electric path 70 to the commercial power supply 2.

[0045] The current sensor 3a detects current flowing between the electric path 70 and the commercial power supply 2. Specifically, the current sensor 3a detects current in forward power flow or reverse power flow. Voltage in the current path between the commercial power supply 2 and the electric path 70 can be considered to take a known value. The known value is, for example, 100 V or 200 V as an effective value. The control unit 50a can calculate power in forward power flow or reverse power flow from the known value and the value detected by the current sensor 3a.

[0046] The control unit 50a can control power in forward power flow or power in reverse power flow by monitoring the current value detected by the current sensor 3a.

[0047] In one example, the control unit 50a controls the power supply system 1a so as not to cause forward power flow and reverse power flow. Specifically, the control unit 50a controls the power supply system 1a such that current flowing between the electric path 70 and the commercial power supply 2 tracks zero.

[0048] In another example, the control unit 50a controls the power supply system 1a such that power in forward power flow tracks a target value. In this example, even if transient fluctuation of the generated power PPVof the photovoltaic facility 10 and / or the consumed power PLof the electrical load 5 occurs, reverse power flow is easily avoided.

[0049] In still another example, the control unit 50a controls the power supply system 1a such that power in reverse power flow tracks a target value.

[0050] By controlling at least one selected from the group consisting of the charge / discharge power PSBof the storage battery facility 30, the generated power PPVof the photovoltaic facility 10, the generated power PFCof the fuel cell facility 20, and the consumed power PWEof the water electrolysis facility 40, in consideration of the consumed power PLof the electrical load 5, the control unit 50a can control power in forward power flow or reverse power flow. In the example illustrated in Fig. 1, in a case where the following mathematical expression 1 is satisfied, neither forward power flow nor reverse power flow occurs. In a case where the following mathematical expression 2 is satisfied, forward power flow occurs. In a case where the following mathematical expression 3 is satisfied, reverse power flow occurs. Mathematical expression 1: PL+PWE=PPV+PFC+PSB Mathematical expression 2: PL+PWE＞PPV+PFC+PSB Mathematical expression 3: PL+PWE＜PPV+PFC+PSB

[0051] [1-2. Operation] In Embodiment 1, the control unit 50a controls the operation of the water electrolysis facility 40 according to surplus power PS.

[0052] The surplus power PSrepresents surplus power with respect to the consumed power PLof the electrical load 5, in generated power PGof at least one power generation facility 60 in the power supply system 1a. That is, the surplus power PSrepresents a difference obtained by subtracting the consumed power PLfrom the generated power PG, that is, represents a value calculated by the following mathematical expression 4. Mathematical expression 4: PS=PG-PL

[0053] The “generated power PGof at least one power generation facility 60 in the power supply system 1a” will be described. In a case where the at least one power generation facility 60 is one power generation facility 60, the generated power PGrepresents the generated power of the power generation facility 60. In a case where the at least one power generation facility 60 is a plurality of power generation facilities 60, the generated power PGrepresents the total of the generated powers of the plurality of the power generation facilities 60.

[0054] In Embodiment 1, the at least one power generation facility 60 incudes the photovoltaic facility 10 and the fuel cell facility 20, and the generated power PGincludes the generated power PPVof the photovoltaic facility 10 and the generated power PFCof the fuel cell facility 20. In the example illustrated in Fig. 1, the at least one power generation facility 60 is a combination of the photovoltaic facility 10 and the fuel cell facility 20, and the generated power PGis the total of the generated power PPVand the generated power PFC.

[0055] Hereinafter, the storage amount of the storage battery facility 30 is referred to as storage amount CA. The storage amount CA may be represented as a physical quantity having a dimension at an ampere, watt, or the like, or may be quantitatively represented as a charge state such as SOC (state of charge) relative to the fully charged state and the fully discharged state.

[0056] In Embodiment 1, an operation state of the storage battery facility 30 includes a fluctuation absorbing state. In the fluctuation absorbing state, power flowing between the electric path 70 and the storage battery facility 30 is changed such that the charge / discharge power PC / Dof the storage battery facility 30 is decreased according to increase of the surplus power PS. In the fluctuation absorbing state, power flowing between the electric path 70 and the storage battery facility 30 is changed such that the charge / discharge power PC / Dof the storage battery facility 30 is increased according decrease of the surplus power PS. The fluctuation absorbing state is achieved by the control unit 50a. Specifically, the control unit 50a decreases the charge / discharge power PC / Dwhen the surplus power PSis increased. That is, the discharge power of the storage battery facility 30 is decreased or the charge power thereof is increased. The control unit 50a increases the charge / discharge power PC / Dwhen the surplus power PSis decreased. That is, discharge power of the storage battery facility 30 is increased or charge power thereof is decreased. In the fluctuation absorbing state, fluctuation of the surplus power PScan be absorbed by the storage battery facility 30. This can stabilize power to be supplied to the water electrolysis facility 40.

[0057] In Embodiment 1, the cycle at which the storage battery facility 30 is controlled is shorter than the cycle at which the photovoltaic facility 10 is controlled, the cycle at which the fuel cell facility 20 is controlled, and the cycle at which the water electrolysis facility 40 is controlled. This is advantageous from the viewpoint of adjusting the charge / discharge power PC / Dat a short cycle, and stabilizing power to be supplied to the water electrolysis facility 40. Specifically, this is advantageous from the viewpoint of absorbing a high frequency component (for example, a component in which the cycle is a millisecond order) in fluctuation of the consumed power PLof the electrical load 5, and, furthermore, absorbing fluctuation of the generated power PPVof the photovoltaic facility 10, which is derived from a solar radiation amount changing with elapse of time. In one example, the period in which the storage battery facility 30 is in the fluctuation absorbing state includes a period in which the charge / discharge power PSBof the storage battery facility 30 is decreased complementarily according to increase of the generated power PPVof the photovoltaic facility 10, and the charge / discharge power PSBof the storage battery facility 30 is increased complementarily according to decrease of the generated power PPVof the photovoltaic facility 10.

[0058] In Embodiment 1, the control unit 50a causes power flowing from the power supply system 1a to the commercial power supply 2 to track 0 W. That is, the control unit 50a controls the power supply system 1a such that neither forward power flow nor reverse power flow occurs.

[0059] Fig. 2 illustrates a table representing a relationship among the surplus power PSand the storage amount CA, an operation of the storage battery facility 30, and execution or non-execution of water electrolysis of the water electrolysis facility 40, during increase of the surplus power PS, according to Embodiment 1. Fig. 3 illustrates a table representing a relationship among the surplus power PSand the storage amount CA, an operation of the storage battery facility 30, and execution or non-execution of water electrolysis of the water electrolysis facility 40, during decrease of the surplus power PS, according to Embodiment 1. Fig. 4 is a zone diagram illustrating a relationship between the surplus power PSand execution or non-execution of water electrolysis of the water electrolysis facility 40, according to Embodiment 1. The operation of the storage battery facility 30 and the operation of the water electrolysis facility 40 as illustrated in Fig. 2 to Fig. 4 are achieved when the control unit 50a controls the storage battery facility 30 and the water electrolysis facility 40.

[0060] Hereinafter, the terms of state j1, state j2, state j3, state j4, state k1, state k2, state k3, and state k4, will be used. The terms represent the following states. ・State j1 represents a state in which the surplus power PSis increasing, the surplus power PSis less than a first threshold value Th1, and the storage amount CA is less than a predetermined value ThP. ・State j2 represents a state in which the surplus power PSis increasing, the surplus power PSis less than the first threshold value Th1, and the storage amount CA is the predetermined value ThPor more. ・State j3 represents a state in which the surplus power PSis increasing, the surplus power PSis the first threshold value Th1or more, and the storage amount CA is less than the predetermined value ThP. ・State j4 represents a state in which the surplus power PSis increasing, the surplus power PSis the first threshold value Th1or more, and the storage amount CA is the predetermined value ThPor more. ・State k1 represents a state in which the surplus power PSis decreasing, the surplus power PSis a second threshold value Th2or more, and the storage amount CA is less than the predetermined value ThP. ・State k2 represents a state in which the surplus power PSis decreasing, the surplus power PSis the second threshold value Th2or more, and the storage amount CA is the predetermined value ThPor more. ・State k3 represents a state in which the surplus power PSis decreasing, the surplus power PSis less than the second threshold value Th2, and the storage amount CA is less than the predetermined value ThP. ・State k4 represents a state in which the surplus power PSis decreasing, the surplus power PSis less than the second threshold value Th2, and the storage amount CA is the predetermined value ThPor more.

[0061] The first threshold value Th1is larger than the second threshold value Th2. In Embodiment 1, typically, the first threshold value Th1and the second threshold value Th2each take a value larger than or equal to the above-described first threshold power.

[0062] As is understood from Fig. 2 and Fig. 4, in the state j1, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0063] In the state j2, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0064] In the state j3, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 1, through the heating operation, water supplied for the water electrolysis reaction is heated. In the electrolyzer 41, power from the electric path 70 causes the water electrolysis reaction.

[0065] In the state j4, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 1, through the heating operation, water supplied for the water electrolysis reaction is heated. In the electrolyzer 41, power from the electric path 70 causes the water electrolysis reaction.

[0066] As is understood from Fig. 3 and Fig. 4, in the state k1, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 1, through the heating operation, water supplied for the water electrolysis reaction is heated. In the electrolyzer 41, power from the electric path 70 causes the water electrolysis reaction.

[0067] In the state k2, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 1, through the heating operation, water supplied for the water electrolysis reaction is heated. In the electrolyzer 41, power from the electric path 70 causes the water electrolysis reaction.

[0068] In the state k3, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0069] In the state k4, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0070] In the water electrolysis facility 40, a control section is configured. The control section includes the control unit 50e. The control section controls the water electrolysis reaction in the water electrolysis facility 40 in cooperation with the control unit 50a. The control section may further include a temperature sensor for measuring a temperature of water supplied for the water electrolysis reaction.

[0071] In Embodiment 1, when the surplus power PSis relatively small, power supplied from the electric path 70 to the water electrolysis facility 40 is less than or equal to power for operating the control section. Meanwhile, when the surplus power PSis relatively large, power supplied from the electric path 70 to the water electrolysis facility 40 is larger than power for operating the control section.

[0072] Specifically, in Embodiment 1, when the surplus power PSis relatively small, no water electrolysis reaction is caused in the electrolyzer 41. Power supplied from the electric path 70 to the water electrolysis facility 40 is for operating the control section. Specifically, by the power, the control unit 50e of the control section can operate, and / or the temperature sensor thereof can operate. It is advantageous that the control section is operated also in a case where no water electrolysis reaction is caused, from the viewpoint of assuring security for the water electrolysis facility 40. When the surplus power PSis relatively small, power supplied from the electric path 70 to the water electrolysis facility 40 may be zero.

[0073] The water electrolysis facility 40 includes a target to be controlled by the control section. Power for operating the target to be controlled is larger than power for operating the control section. Examples of the target to be controlled include the electrolyzer 41 and the heating device 43.

[0074] Fig. 5 is a time-series graph illustrating a relationship among the surplus power PS, power supplied from the electric path 70 to the storage battery facility 30, and power supplied from the electric path 70 to the water electrolysis facility 40, according to a first specific example. In the first specific example, the surplus power PSis increasing, and neither forward power flow from the commercial power supply 2 to the power supply system 1a nor reverse power flow from the power supply system 1a to the commercial power supply 2 is performed. In Fig. 5, the horizontal axis represents time, and the vertical axis represents the surplus power PS. In the first specific example and Fig. 5, description about the fluctuation absorbing state of the storage battery facility 30 is omitted.

[0075] As illustrated in Fig. 5, in the first specific example, power charged in the storage battery facility 30 from the electric path 70 continuously increases from a time t11 until a time t12. Power supplied from the electric path 70 to the water electrolysis facility 40 is maintained to be almost zero.

[0076] At the time t12, the surplus power PSindicates the first threshold value Th1. In the example illustrated in Fig. 5, the first threshold value Th1represents 30 kW. Power charged in the storage battery facility 30 from the electric path 70 discontinuously decreases. In the example illustrated in Fig. 5, at the time t12, the power is decreased from 30 kW to 10 kW. Meanwhile, power supplied from the electric path 70 to the water electrolysis facility 40 discontinuously increases. In the example illustrated in Fig. 5, at the time t12, the power is increased from almost zero to 20 kW. It is understood from Fig. 5 that the power after the increase is calculated as 30 kW-10 kW=20 kW. At the time t12, driving of the heating device 43 and the water electrolysis reaction in the electrolyzer 41 are started by power supplied from the electric path 70 to the water electrolysis facility 40.

[0077] From the time t12 until a time t13, power charged in the storage battery facility 30 from the electric path 70 continuously increases. Power supplied from the electric path 70 to the water electrolysis facility 40 continuously increases. In the electrolyzer 41, power used for the water electrolysis reaction and an amount of generated hydrogen increase.

[0078] At the time t13, increase of power charged in the storage battery facility 30 from the electric path 70 halts. In the example illustrated in Fig. 5, at the time t13, the power is 50 kW.

[0079] From the time t13 until a time t14, power charged in the storage battery facility 30 from the electric path 70 is maintained to be constant. In the example illustrated in Fig. 5, the power is 50 kW. Power supplied from the electric path 70 to the water electrolysis facility 40 continuously increases. According to the increase, in the electrolyzer 41, power used for the water electrolysis reaction and an amount of generated hydrogen increase.

[0080] At the time t14, increase of power supplied from the electric path 70 to the water electrolysis facility 40 halts. In the example illustrated in Fig. 5, at the time t14, the power is 70 kW. It is understood from Fig. 5 that the power is calculated as 120 kW-50 kW=70 kW. The surplus power PSis 120 kW.

[0081] At the time t14 and the subsequent times, power charged in the storage battery facility 30 from the electric path 70 is maintained to be constant. In the example illustrated in Fig. 5, the power is 50 kW. Power supplied from the electric path 70 to the water electrolysis facility 40 is maintained to be constant. In the example illustrated in Fig. 5, the power is 70 kW. An amount of generated hydrogen in the water electrolysis facility 40 is maintained to be constant.

[0082] From the time t11 until the time t14, MPPT control of the photovoltaic module 11 is performed in the photovoltaic facility 10, and the fuel cell stack 21 generates rated generation power in the fuel cell facility 20. From the time t11 until the time t12, the surplus power PSis absorbed by the storage battery facility 30, so that reverse power flow is prevented. From the time t12 until the time t14, the surplus power PSis absorbed by the storage battery facility 30 and the water electrolysis facility 40, so that reverse power flow is prevented. At the time t14 and the subsequent times, the surplus power PSis absorbed by the storage battery facility 30 and the water electrolysis facility 40. Furthermore, the operation point of the photovoltaic module 11 is displaced from the maximum power point, and / or the generated power of the fuel cell stack 21 is reduced to be less than the rated generation power, thereby reducing the generated power PG. Thus, reverse power flow is prevented.

[0083] Fig. 6 is a time-series graph illustrating a relationship among the surplus power PS, power supplied from the electric path 70 to the storage battery facility 30, and power supplied from the electric path 70 to the water electrolysis facility 40, according to a second specific example. In the second specific example, the surplus power PSis decreasing, and neither forward power flow from the commercial power supply 2 to the power supply system 1a nor reverse power flow from the power supply system 1a to the commercial power supply 2 is performed. In Fig. 6, the horizontal axis represents time, and the vertical axis represents the surplus power PS. In the second specific example and Fig. 6, description about the fluctuation absorbing state of the storage battery facility 30 is omitted.

[0084] As illustrated in Fig. 6, in the second specific example, from a time t21 until a time t22, power charged in the storage battery facility 30 from the electric path 70 is maintained to be constant. In the example illustrated in Fig. 6, the power is 50 kW. Power supplied from the electric path 70 to the water electrolysis facility 40 is maintained to be constant. In the example illustrated in Fig. 6, the power is 70 kW. It is understood from Fig. 6 that the power is calculated as 120 kW-50 kW=70 kW. Power used for the water electrolysis reaction in the electrolyzer 41 and an amount of generated hydrogen are maintained to be constant.

[0085] At the time t22, decrease of power charged in the storage battery facility 30 from the electric path 70 is started. Decrease of power supplied from the electric path 70 to the water electrolysis facility 40 is started. In the example illustrated in Fig. 6, at the time t22, the surplus power PSis 120 kW.

[0086] From the time t22 until a time t23, power charged in the storage battery facility 30 from the electric path 70 continuously decreases. Power supplied from the electric path 70 to the water electrolysis facility 40 continuously decreases. According to the decrease, power used for the water electrolysis reaction in the electrolyzer 41 and an amount of generated hydrogen decrease.

[0087] At the time t23, the surplus power PSindicates the second threshold value Th2. In the example illustrated in Fig. 6, the second threshold value Th2represents 25 kW. Power charged in the storage battery facility 30 from the electric path 70 discontinuously increases. In the example illustrated in Fig. 6, at the time t23, the power increases from 5 kW to 25 kW. Meanwhile, power supplied from the electric path 70 to the water electrolysis facility 40 discontinuously decreases. In the example illustrated in Fig. 6, at the time t23, the power is decreased from 20 kW to almost zero. It is understood from Fig. 6 that the power before the decrease is calculated as 25 kW-5 kW=20 kW. At the time t23, in the water electrolysis facility 40, driving of the heating device 43 and water electrolysis are halted.

[0088] At the time t23 and the subsequent times, power charged in the storage battery facility 30 from the electric path 70 continuously decreases. Power supplied from the electric path 70 to the water electrolysis facility 40 is maintained to be almost zero.

[0089] From the time t21 until the time t22, the surplus power PSis absorbed by the storage battery facility 30 and the water electrolysis facility 40. Furthermore, the operation point of the photovoltaic module 11 is displaced from the maximum power point, and / or the generated power of the fuel cell stack 21 is reduced to be less than the rated generation power, thereby reducing the generated power PG. Thus, reverse power flow is prevented. At the time t22 and the subsequent times, MPPT control of the photovoltaic module 11 is performed in the photovoltaic facility 10, and the fuel cell stack 21 generates rated generation power in the fuel cell facility 20. From the time t22 until time t23, the surplus power PSis absorbed by the storage battery facility 30 and the water electrolysis facility 40, so that reverse power flow is prevented. At the time t23 and the subsequent times, the surplus power PSis absorbed by the storage battery facility 30, so that reverse power flow is prevented.

[0090] As is understood from the above description, in Embodiment 1, the control unit 50a has a configuration suitable for utilizing power generation capability of the photovoltaic facility 10 while avoiding reverse power flow from the power supply system 1a to the commercial power supply 2. Specifically, in the power supply system 1a, the generated power PPVof the photovoltaic facility 10 is increased according to an amount of solar radiation, whereby the surplus power PScan be generated. Meanwhile, the power supply system 1a of Embodiment 1 includes the water electrolysis facility 40 and the hydrogen storing section 47 in addition to the storage battery facility 30. The surplus power PScan be absorbed by the storage battery facility 30, and by the water electrolysis facility 40 and the hydrogen storing section 47. Specifically, the surplus power PSis charged in the storage battery facility 30. Thus, power as the energy medium is stored so as to be utilized later. The water electrolysis facility 40 converts the surplus power PSto hydrogen through water electrolysis, the hydrogen storing section 47 temporarily stores the hydrogen, and the fuel cell facility 20 generates power by using the hydrogen. Thus, through the exchange of the energy medium, hydrogen as the energy medium is stored so as to be utilized later. Thus, in Embodiment 1, the energy medium is stored so as to be utilized later, whereby the surplus power PScan be absorbed.

[0091] Furthermore, in Embodiment 1, a configuration suitable for inhibiting degradation of the water electrolysis facility 40 is adopted. Specifically, in Embodiment 1, the second threshold value Th2is less than the first threshold value Th1. The hysteresis of the threshold value allows reduction of the frequency of activation and halt of the water electrolysis facility 40. This is advantageous from the viewpoint of inhibiting degradation of the water electrolysis facility 40, in particular, inhibiting degradation of a catalyst in the water electrolysis facility 40. Furthermore, in Embodiment 1, the storage battery facility 30 can be in the fluctuation absorbing state. Thus, fluctuation of the surplus power PSis absorbed, and power supplied from the electric path 70 to the water electrolysis facility 40 can be stabilized. This can inhibit degradation of the water electrolysis facility 40. In one specific example, power supplied from the electric path 70 to the water electrolysis facility 40 becomes substantially constant.

[0092] Some other embodiments will be described below. In the following description, elements common to the already described embodiment and embodiments described below are denoted by the same reference characters, and the description thereof may be omitted. The descriptions for the respective embodiments may be applied to each other as long as there is no technical contradiction. The embodiments may be combined with each other as long as there is no technical contradiction.

[0093] (Embodiment 2) Embodiment 2 will be described below with reference to Fig. 7 to Fig. 9.

[0094] In Embodiment 2, the control unit 50a controls the operation of the storage battery facility 30 according to the storage amount CA. Furthermore, the control unit 50a controls the operation of the water electrolysis facility 40 according to the surplus power PSand the storage amount CA.

[0095] Fig. 7 illustrates a table representing a relationship among the surplus power PSand the storage amount CA, an operation of the storage battery facility 30, and execution or non-execution of water electrolysis of the water electrolysis facility 40, during increase of the surplus power PS, according to Embodiment 2. Fig. 8 illustrates a table representing a relationship among the surplus power PSand the storage amount CA, an operation of the storage battery facility 30, and execution or non-execution of water electrolysis of the water electrolysis facility 40, during decrease of the surplus power PS, according to Embodiment 2. Fig. 9 is a zone diagram illustrating a relationship among the surplus power PSand the storage amount CA, an operation of the storage battery facility 30, and execution or non-execution of water electrolysis of the water electrolysis facility 40, according to Embodiment 2. The operation of the storage battery facility 30 and the operation of the water electrolysis facility 40 as illustrated in Fig. 7 to Fig. 9 are achieved when the control unit 50a controls the storage battery facility 30 and the water electrolysis facility 40.

[0096] Hereinafter, the terms of state x1, state x2, state x3, state x4, state x5, state x6, state y1, state y2, state y3, state y4, state y5, and state y6, will be used. The terms represent the following states. ・State x1 represents a state in which the surplus power PSis increasing, the surplus power PSis less than a third threshold value Th3,and the storage amount CA is less than the predetermined value ThP. ・State x2 represents a state in which the surplus power PSis increasing, the surplus power PSis less than the third threshold value Th3, and the storage amount CA is the predetermined value ThPor more. ・State x3 represents a state in which the surplus power PSis increasing, the surplus power PSis the third threshold value Th3or more and less than the first threshold value Th1, and the storage amount CA is less than the predetermined value ThP. ・State x4 represents a state in which the surplus power PSis increasing, the surplus power PSis the third threshold value Th3or more and less than the first threshold value Th1, and the storage amount CA is the predetermined value ThPor more. ・State x5 represents a state in which the surplus power PSis increasing, the surplus power PSis the first threshold value Th1or more, and the storage amount CA is less than the predetermined value ThP. ・State x6 represents a state in which the surplus power PSis increasing, the surplus power PSis the first threshold value Th1or more, and the storage amount CA is the predetermined value ThPor more. ・State y1 represents a state in which the surplus power PSis decreasing, the surplus power PSis the second threshold value Th2or more, and the storage amount CA is less than the predetermined value ThP. ・State y2 represents a state in which the surplus power PSis decreasing, the surplus power PSis the second threshold value Th2or more, and the storage amount CA is the predetermined value ThPor more. ・State y3 represents a state in which the surplus power PSis decreasing, the surplus power PSis a fourth threshold value Th4or more and less than the second threshold value Th2, and the storage amount CA is less than the predetermined value ThP. ・State y4 represents a state in which the surplus power PSis decreasing, the surplus power PSis the fourth threshold value Th4or more and less than the second threshold value Th2, and the storage amount CA is the predetermined value ThPor more. ・State y5 represents a state in which the surplus power PSis decreasing, the surplus power PSis less than the fourth threshold value Th4, and the storage amount CA is less than the predetermined value ThP. ・State y6 represents a state in which the surplus power PSis decreasing, the surplus power PSis less than the fourth threshold value Th4, and the storage amount CA is the predetermined value ThPor more.

[0097] The first threshold value Th1is larger than the second threshold value Th2. The third threshold value Th3is larger than the fourth threshold value Th4. The second threshold value Th2is larger than the third threshold value Th3. In Embodiment 2, typically, the first threshold value Th1and the second threshold value Th2each take a value larger than or equal to the above-described first threshold power. The third threshold value Th3and the fourth threshold value Th4each take a value less than the above-described first threshold power.

[0098] As is understood from Fig. 7 and Fig. 9, in the state x1, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0099] In the state x2, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0100] In the state x3, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0101] In the state x4, the storage battery facility 30 is charged from the electric path 70 or performs discharging to the electric path 70. Specifically, in a case where the surplus power PSis less than power required by the water electrolysis facility 40, the storage battery facility 30 performs discharging to the electric path 70. Thus, power is supplied from the storage battery facility 30 to the water electrolysis facility 40. More specifically, in this case, power corresponding to a difference obtained by subtracting the surplus power PSfrom the required power is discharged from the storage battery facility 30 to the electric path 70, and supplied to the water electrolysis facility 40. Meanwhile, in a case where the surplus power PSis larger than the power required by the water electrolysis facility 40, the storage battery facility 30 is charged from the electric path 70. In Embodiment 2, the required power includes power consumed by the heating device 43 and power supplied for the water electrolysis reaction in the electrolyzer 41. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0102] In the state x5, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0103] In the state x6, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0104] As is understood from Fig. 8 and Fig. 9, in the state y1, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0105] In the state y2, the storage battery facility 30 is charged from the electric path 70. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0106] In the state y3, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0107] In the state y4, the storage battery facility 30 is charged from the electric path 70 or performs discharging to the electric path 70. Specifically, in a case where the surplus power PSis less than the power required by the water electrolysis facility 40, the storage battery facility 30 performs discharging to the electric path 70. Thus, power is supplied from the storage battery facility 30 to the water electrolysis facility 40. More specifically, in this case, power corresponding to a difference obtained by subtracting the surplus power PSfrom the required power is discharged from the storage battery facility 30 to the electric path 70, and supplied to the water electrolysis facility 40. Meanwhile, in a case where the surplus power PSis larger than the power required by the water electrolysis facility 40, the storage battery facility 30 is charged from the electric path 70. In Embodiment 2, the required power includes power consumed by the heating device 43 and power supplied for the water electrolysis reaction in the electrolyzer 41. Power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. In Embodiment 2, through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41.

[0108] In the state y5, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0109] In the state y6, the storage battery facility 30 is charged from the electric path 70. Power is not supplied to the heating device 43 from the electric path 70, and the heating device 43 does not perform a heating operation. No water electrolysis reaction is caused in the electrolyzer 41.

[0110] In Embodiment 2, a configuration suitable for inhibiting degradation of the water electrolysis facility 40 is adopted. Specifically, in Embodiment 2, the fourth threshold value Th4is less than the third threshold value Th3. The hysteresis of the threshold value allows reduction of the frequency of activation and halt of the water electrolysis facility 40. This is advantageous from the viewpoint of inhibiting degradation of the water electrolysis facility 40, in particular, inhibiting degradation of a catalyst in the water electrolysis facility 40.

[0111] Various modifications can be applied to the above-described embodiments.

[0112] In the above-described embodiments, the charge / discharge power PSBof the storage battery facility 30 is calculated from the value detected by the current sensor 7b. In another example, a power controller including the DCAC inverter 33 is provided in the storage battery facility 30. A power sensor is provided in the power controller. The power sensor detects the charge / discharge power PSB, and transmits the detected value to the control unit 50a.

[0113] In the above-described embodiments, the generated power PPVof the photovoltaic facility 10 is calculated from the value detected by the current sensor 7c. In another example, a power controller including the DCAC inverter 13 is provided in the photovoltaic facility 10. A power sensor is provided in the power controller. The power sensor detects the generated power PPV, and transmits the detected value to the control unit 50a.

[0114] In the above-described embodiments, the generated power PFCof the fuel cell facility 20 is calculated form the value detected by the current sensor 7d. In another example, a power controller including the DCAC inverter 23 is provided in the fuel cell facility 20. A power sensor is provided in the power controller. The power sensor detects the generated power PFCof the fuel cell facility 20, and transmits the detected value to the control unit 50a.

[0115] In the above-described embodiments, the consumed power PWEof the water electrolysis facility 40 is calculated from the value detected by the current sensor 7e. In another example, a power controller including the transformer rectifier 42 is provided in the water electrolysis facility 40. A power sensor is provided in the power controller. The power sensor detects the consumed power PWEof the water electrolysis facility 40, and transmits the detected value to the control unit 50a.

[0116] In the examples illustrated in Figs. 2 to 4 and 7 to 9, in the states j3, j4, k1, k2, x4, x5, x6, y1, y2, and y4, power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. Through the heating operation, water supplied for the water electrolysis reaction is heated. Power from the electric path 70 causes the water electrolysis reaction in the electrolyzer 41. Hereinafter, an operation involving such a heating operation of the heating device 43 and the water electrolysis reaction in the electrolyzer 41 is referred to as water electrolysis operation of the water electrolysis facility 40.

[0117] In another example, in the states j3, j4, k1, k2, x4, x5, x6, y1, y2, and y4, idling instead of the water electrolysis operation is performed in the water electrolysis facility 40. In the idling, power is supplied to the heating device 43 from the electric path 70, and the heating device 43 performs a heating operation. However, in the idling, no water electrolysis reaction is caused in the electrolyzer 41. Therefore, power supplied for the water electrolysis reaction does not exist in the electrolyzer 41. This other example can be described by replacing the terms in the examples illustrated in Figs. 2 to 4 and 7 to 9 as appropriate. The replacement includes replacement from “first threshold power” to “second threshold power”. The second threshold power represents power larger than or equal to power required for the idling. As is understood from the description after the replacement, switching between on and off of the idling can be performed based on the first threshold value Th1and the second threshold value Th2or based on the first threshold value Th1, the second threshold value Th2, the third threshold value Th3, and the fourth threshold value Th4.

[0118] In the idling of one specific example, the control unit 50e and / or a temperature sensor for measuring a temperature of water supplied for the water electrolysis reaction, in addition to the heating device 43, can be operated by power supplied from the electric path 70. The first threshold value Th1and the second threshold value Th2each represent power larger than or equal to power supplied for these operations. Each of the third threshold value Th3and the fourth threshold value Th4can be power less than power supplied for these operations.

[0119] In at least one state selected from the group consisting of the states j3, j4, k1, k2, x4, x5, x6, y1, y2, and y4, the water electrolysis operation and the idling can be combined with each other. Specifically, a period for the at least one state can include a water electrolysis operation period and an idling period. In one specific example, in the period for the at least one state, the water electrolysis operation period follows the idling period.

[0120] In the above-described embodiments, the number of the photovoltaic modules in one photovoltaic facility is one. However, the number of the photovoltaic modules in one photovoltaic facility may be two or more.

[0121] In the above-described embodiments, the number of the fuel cell stacks in one fuel cell facility is one. However, the number of the fuel cell stacks in one fuel cell facility may be two or more. In this case, the generated power PFCof the fuel cell facility 20 can also be controlled by controlling the number of the operating fuel cell stacks. This is advantageous from the viewpoint of enhancing responsiveness in control of the generated power PFC.

[0122] In the above-described embodiments, the number of the storage battery modules in one storage battery facility is one. However, the number of the storage battery modules in one storage battery facility may be two or more.

[0123] In the above-described embodiments, the number of the electrolyzers in one water electrolysis facility is one. However, the number of the electrolyzers in one water electrolysis facility may be two or more.

[0124] In the example illustrated in Fig. 1. the number of the power generation facilities 60 is two. However, the number of the power generation facilities 60 may be one, or three or more.

[0125] In the above-described embodiments, the at least one power generation facility 60 includes the photovoltaic facility 10 and the fuel cell facility 20. However, it is not essential that the at least one power generation facility 60 includes both the photovoltaic facility 10 and the fuel cell facility 20. The at least one power generation facility 60 may merely include one of the photovoltaic facility 10 or the fuel cell facility 20. The type of the power generation facility 60 is not limited to the photovoltaic facility 10 and the fuel cell facility 20. The at least one power generation facility 60 may include a wind power generation facility, a geothermal power generation facility, etc., instead of or in addition to the photovoltaic facility 10 and / or the fuel cell facility 20.

[0126] In the above-described embodiments, hydrogen generated by the water electrolysis facility 40 is supplied to the fuel cell facility 20. However, a destination to which hydrogen generated by the water electrolysis facility 40 is supplied is not limited to the fuel cell facility 20. Examples of another destination to which the hydrogen is supplied include a hydrogen engine.

[0127] [1-3. Effects and the like] The power supply system 1a according to one example of the present disclosure includes the at least one power generation facility 60, the storage battery facility 30, the water electrolysis facility 40, the electric path 70, the control unit 50a, the hydrogen path 75, and the hydrogen storing section 47. The at least one power generation facility 60 includes the photovoltaic facility 10 and / or the fuel cell facility 20. The electric path 70 is connected to the at least one power generation facility 60, the storage battery facility 30, and the water electrolysis facility 40. The control unit 50a controls the at least one power generation facility 60, the storage battery facility 30, and the water electrolysis facility 40. The hydrogen path 75 guides hydrogen from the water electrolysis facility 40 to the fuel cell facility 20. The hydrogen storing section 47 is provided in the hydrogen path 75. The power supply system 1a supplies power through the electric path 70 to the electrical load 5.

[0128] In one example of the present disclosure, the control unit 50a shifts the operation state of the power supply system 1a from a first state to a second state according to increase of the surplus power PS. The surplus power PSis surplus power with respect to the consumed power PLof the electrical load 5, in the generated power PGof the at least one power generation facility 60. In the first state, power is supplied from the electric path 70 to the storage battery facility 30. In the first state, the water electrolysis facility 40 does not perform water electrolysis. In the second state, power is supplied from the electric path 70 to the storage battery facility 30. Power supplied from the electric path 70 to the water electrolysis facility 40 in the second state, is larger than power supplied from the electric path 70 to the water electrolysis facility 40 in the first state. This configuration is suitable for increasing the surplus power PSthat can be absorbed by the power supply system 1a, according to increase of the surplus power PS.

[0129] The expression “power supplied from the electric path 70 to the water electrolysis facility 40 in the second state, is larger than power supplied from the electric path 70 to the water electrolysis facility 40 in the first state” will be described. This expression implies both a case where power supplied from the electric path 70 to the water electrolysis facility 40 in the first state is zero and a case where the power is not zero. In a case where power supplied from the electric path 70 to the water electrolysis facility 40 in the first state is not zero, the power can be, for example, consumed by the control unit 50e, the temperature sensor for measuring a temperature of water supplied for the water electrolysis reaction, and the like.

[0130] Specifically, by using the storage battery facility 30 and the water electrolysis facility 40 in combination, a large magnitude of the surplus power PScan be absorbed. For example, it is considered that the photovoltaic facility 10 is configured in such a scale that photovoltaic power generation is sufficiently performed in winter. In this case, power generated by photovoltaic power generation becomes large in summer, and the surplus power PSmay be increased. By using the storage battery facility 30 and the water electrolysis facility 40 in combination, such a large magnitude of the surplus power PScan be absorbed.

[0131] By using the storage battery facility 30 and the water electrolysis facility 40 in combination, a period in which the surplus power PScan be absorbed can be extended. This is useful in a case where, for example, reverse power flow is to be avoided.

[0132] The above-described configuration is suitable for restricting a period in which a large magnitude of power is consumed by the water electrolysis facility 40, inhibiting degradation of the water electrolysis facility 40, and increasing the lifespan of the water electrolysis facility 40.

[0133] In one example of the present disclosure, the water electrolysis facility 40 includes the control section that controls the water electrolysis reaction in the water electrolysis facility 40 in cooperation with the control unit 50a. In the first state, power supplied from the electric path 70 to the water electrolysis facility 40 is less than or equal to power for operating the control section. In this configuration, when the surplus power PSis small, power supplied from the electric path 70 to the water electrolysis facility 40 can be decreased. For example, the control section may include the control unit 50e and / or the temperature sensor for measuring a temperature of water supplied for the water electrolysis reaction. The power “less than or equal to power for operating the control section” may be zero or may not be zero.

[0134] In one example of the present disclosure, the water electrolysis facility 40 includes the electrolyzer 41 and the heating device 43. In the electrolyzer 41, the water electrolysis reaction occurs. The heating device 43 is used for the water electrolysis reaction. In the first state, power is not supplied from the electric path 70 to the heating device 43. In the second state, power is supplied from the electric path 70 to the heating device 43. In this configuration, a certain large magnitude of power can be supplied to the water electrolysis facility 40 in the second state. Therefore, in the second state, the water electrolysis facility 40 is likely to contribute to absorption of the surplus power PS.

[0135] In one example of the present disclosure, the period in which the power supply system 1a is in the second state includes a period in which power supplied from the electric path 70 to the water electrolysis facility 40 drives the heating device 43 and causes the water electrolysis reaction in the electrolyzer 41. This configuration can be achieved by the control unit 50a. In this example, in the period in which the power supply system 1a is in the second state, power supplied from the electric path 70 to the water electrolysis facility 40 can be larger than or equal to the first threshold power.

[0136] In one example of the present disclosure, the period in which the power supply system 1a is in the second state includes a period in which idling is performed in the water electrolysis facility 40 by power supplied from the electric path 70 to the water electrolysis facility 40. The idling is an operation for driving the heating device 43 without causing the water electrolysis reaction in the electrolyzer 41. This configuration can be achieved by the control unit 50a. In this example, in the period in which the power supply system 1a is in the second state, power supplied from the electric path 70 to the water electrolysis facility 40 can be larger than or equal to the second threshold power.

[0137] In one example of the present disclosure, the control unit 50a decreases power supplied from the electric path 70 to the storage battery facility 30 when shifting the operation state of the power supply system 1a from the first state to the second state. In this configuration, a period in which the storage battery facility 30 can be charged can be extended.

[0138] In one example of the present disclosure, the control unit 50a shifts the operation state of the power supply system 1a from the second state to the first state according to decrease of the surplus power PS.

[0139] In one example of the present disclosure, the control unit 50a increases power supplied from the electric path 70 to the storage battery facility 30 when shifting the operation state of the power supply system 1a from the second state to the first state.

[0140] In one example of the present disclosure, the operation state of the water electrolysis facility 40 includes an off state and an on state. In the off state, power is not supplied from the electric path 70 to the heating device 43, and the heating device 43 is not driven. In the on state, the heating device 43 is driven by power supplied from the electric path 70 to the heating device 43. Specifically, in the on state of one example, the water electrolysis operation is performed in the water electrolysis facility 40. In the on state of another example, idling is performed in the water electrolysis facility 40. In the first state, the water electrolysis facility 40 is in the off state. In the second state, the water electrolysis facility 40 is in the on state.

[0141] In one example of the present disclosure, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the off state to the on state when the surplus power PSis increased so as to cross the first threshold value Th1. The control unit 50a shifts the operation state of the water electrolysis facility 40 from the on state to the off state when the surplus power PSis decreased so as to cross the second threshold value Th2. The second threshold value Th2is less than the first threshold value Th1. In this configuration, hysteresis of the threshold value allows reduction of the frequency of shifting between the off state and the on state. This can inhibit the water electrolysis facility 40 from being degraded due to this shift. For example, degradation of a catalyst in the water electrolysis facility 40 can be inhibited. This configuration is implemented in both Embodiment 1 and Embodiment 2.

[0142] In one example of the present disclosure, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the off state to the on state when the surplus power PSis increased so as to cross the first threshold value Th1, regardless of the storage amount CA of the storage battery facility 30. The control unit 50a shifts the operation state of the water electrolysis facility 40 from the on state to the off state when the surplus power PSis decreased so as to cross the second threshold value Th2, regardless of the storage amount CA of the storage battery facility 30. This configuration is implemented in Embodiment 1.

[0143] In one example of the present disclosure, in a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP, when the surplus power PSis increased so as to cross the first threshold value Th1, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the off state to the on state. In a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP, when the surplus power PSis decreased so as to cross the second threshold value Th2, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the on state to the off state. In a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, when the surplus power PSis increased so as to cross the first threshold value Th1, the control unit 50a maintains the operation state of the water electrolysis facility 40 as the on state. In a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, when the surplus power PSis decreased so as to cross the second threshold value Th2, the control unit 50a maintains the operation state of the water electrolysis facility 40 as the on state. In this configuration, in a case where progress of charging of the storage battery facility 30 is advanced, the water electrolysis facility 40 is allowed to easily take the on state, and, in a case where progress of charging of the storage battery facility 30 is not advanced, the water electrolysis facility 40 is allowed to easily take the off state. This can achieve both absorption of the surplus power PSand inhibition of degradation of the water electrolysis facility 40. This configuration is implemented in Embodiment 2.

[0144] In one example of the present disclosure, when the surplus power PSis increased so as to cross the third threshold value Th3, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the off state to the on state. When the surplus power PSis decreased so as to cross the fourth threshold value Th4, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the on state to the off state. The third threshold value Th3is less than the second threshold value Th2. The fourth threshold value Th4is less than the third threshold value Th3. In this configuration, the hysteresis of the threshold value allows reduction of the frequency of shifting between the off state and the on state. This can inhibit the water electrolysis facility 40 from being degraded due to the shift. For example, degradation of a catalyst in the water electrolysis facility 40 can be inhibited.

[0145] In one example of the present disclosure, in a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP,when the surplus power PSis increased so as to cross the third threshold value Th3, the control unit 50a maintains the operation state of the water electrolysis facility 40 as the off state. In a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP, when the surplus power PSis decreased so as to cross the fourth threshold value Th4, the control unit 50a maintains the operation state of the water electrolysis facility 40 as the off state. In a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, when the surplus power PSis increased so as to cross the third threshold value Th3,the control unit 50a shifts the operation state of the water electrolysis facility 40 from the off state to the on state. In a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, when the surplus power PSis decreased so as to cross the fourth threshold value Th4, the control unit 50a shifts the operation state of the water electrolysis facility 40 from the on state to the off state. The third threshold value Th3is less than the second threshold value Th2. The fourth threshold value Th4is less than the third threshold value Th3. In this configuration, in a case where progress of charging of the storage battery facility 30 is advanced, the water electrolysis facility 40 is allowed to easily take the on state, and, in a case where progress of charging of the storage battery facility 30 is not advanced, the water electrolysis facility 40 is allowed to easily take the off state. This can achieve both absorption of the surplus power PSand inhibition of degradation of the water electrolysis facility 40.

[0146] In one example of the present disclosure, in a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, the surplus power PSin the case of the operation state of the water electrolysis facility 40 being shifted from the off state to the on state, is low as compared with a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP. In this configuration, in a case where progress of charging of the storage battery facility 30 is advanced, the water electrolysis facility 40 is allowed to easily take the on state, and, in a case where progress of charging of the storage battery facility 30 is not advanced, the water electrolysis facility 40 is allowed to easily take the off state. This can achieve both absorption of the surplus power PSand inhibition of degradation of the water electrolysis facility 40. This configuration can be achieved by the control unit 50a.

[0147] In one example of the present disclosure, the control unit 50a performs specific control. In the specific control, in a case where the storage amount CA of the storage battery facility 30 is less than the predetermined value ThP, the operation state of the water electrolysis facility 40 is set as the off state. In the specific control, in a case where the storage amount CA of the storage battery facility 30 is the predetermined value ThPor more, and the surplus power PSis less than the power required by the water electrolysis facility 40, the operation state of the water electrolysis facility 40 is set as the on state, and, simultaneously, power is supplied from the storage battery facility 30 to the water electrolysis facility 40. In this configuration, the storage battery facility 30 can compensate for insufficient power in the water electrolysis facility 40. In this configuration, for example, the above-described required power includes power to be consumed by the heating device 43 and power to be supplied for the water electrolysis reaction in the electrolyzer 41. Specifically, the above-described required power can be power required for the water electrolysis operation in the water electrolysis facility 40. Furthermore, in this configuration, for example, the above-described required power includes power to be consumed by the heating device 43, and does not include power to be supplied for the water electrolysis reaction in the electrolyzer 41. Specifically, the above-described required power can be power required for the idling in the water electrolysis facility 40. In the specific control of one specific example, in a case where the storage amount CAof the storage battery facility 30 is the predetermined value ThPor more, and the surplus power PSis less than the power required by the water electrolysis facility 40, the operation state of the water electrolysis facility 40 is set as the on state, and, simultaneously, power corresponding to the difference is supplied from the storage battery facility 30 to the water electrolysis facility 40. The power corresponding to the difference is power obtained by subtracting the surplus power PSfrom the required power.

[0148] In one example of the present disclosure, the control unit 50a starts the specific control when the surplus power PSis increased so as to cross the third threshold value Th3. The control unit 50a starts the specific control when the surplus power PSis decreased so as to cross the second threshold value Th2. The control unit 50a ends the specific control when the surplus power PSis increased so as to cross the first threshold value Th1. The control unit 50a ends the specific control when the surplus power PSis decreased so as to cross the fourth threshold value Th4. The second threshold value Th2is less than the first threshold value Th1. The third threshold value Th3is less than the second threshold value Th2. The fourth threshold value Th4is less than the third threshold value Th3.

[0149] In one example of the present disclosure, the power supply system 1a and the commercial power supply 2 are interconnected through the electric path 70. The control unit 50a controls the at least one power generation facility 60, the storage battery facility 30, and the water electrolysis facility 40 so as to avoid reverse power flow from the power supply system 1a to the commercial power supply 2. Specifically, the control unit 50a controls the photovoltaic facility 10 and / or the fuel cell facility 20, the storage battery facility 30, and the water electrolysis facility 40 so as to avoid reverse power flow from the power supply system 1a to the commercial power supply 2.

[0150] It is possible to adopt the configuration in which power is not supplied from the electric path 70 to the electrolyzer 41 in the first state, and power is supplied from the electric path 70 to the electrolyzer 41 in the second state. This configuration can also realize the magnitude relationship that “power supplied from the electric path 70 to the water electrolysis facility 40 in the second state, is larger than power supplied from the electric path 70 to the water electrolysis facility 40 in the first state”. Specifically, it is possible to adopt the configuration in which the water electrolysis reaction in the electrolyzer 41 is not caused in the first state, and power supplied from the electric path 70 to the water electrolysis facility 40 causes the water electrolysis reaction in the electrolyzer 41 in the second state.

[0151] In one specific example, in the first state, the heating device 43 is driven by power supplied from the electric path 70 to the heating device 43 while the water electrolysis reaction in the electrolyzer 41 is not caused. In the second state, power supplied from the electric path 70 to the water electrolysis facility 40 drives the heating device 43 and causes the water electrolysis reaction in the electrolyzer 41. This specific example can also realize the magnitude relationship that “power supplied from the electric path 70 to the water electrolysis facility 40 in the second state, is larger than power supplied from the electric path 70 to the water electrolysis facility 40 in the first state”. In this specific example, specifically, the operation in the first state is the idling. The operation in the second state is the water electrolysis operation.

[0152] A control method according to one example of the present disclosure includes shifting an operation state of the power supply system 1a from the first state to the second state according to increase of the surplus power PS. A program according to one example of the present disclosure, when being executed by a processor, includes an instruction that causes the processor to execute the above control method. A storage medium according to one example of the present disclosure is a computer-readable storage medium in which the above program is stored. The control method is performed by the power supply system 1a in one example, and is performed by the control unit 50a in one specific example. The program is installed in the power supply system 1a in one example, and is installed in the control unit 50a in one specific example. The processor is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The storage medium is, for example, a semiconductor storage medium, a magnetic storage medium, a magneto-optical storage medium, an optical storage medium, or the like. The semiconductor storage medium is, for example, a secure digital (SD) card, a universal serial bus (USB) memory, a solid state drive (SSD), or the like. The magnetic storage medium is, for example, a hard disk drive (HDD), a flexible disk, or the like. The magneto-optical storage medium is, for example, a magneto-optical (MO) disk or the like. The optical storage medium is, for example, a compact disc (CD), a digital versatile disc (DVD), or the like.

[0153] The power supply system according to the present disclosure can be applied to facilities such as factories.

Claims

1. A power supply system comprising: at least one power generation facility; a storage battery facility; a water electrolysis facility; an electric path connected to the at least one power generation facility, the storage battery facility, and the water electrolysis facility; and a control unit that controls the at least one power generation facility, the storage battery facility, and the water electrolysis facility, wherein power is supplied through the electric path to an electrical load, and the control unit shifts an operation state of the power supply system, according to increase of surplus power with respect to consumed power of the electrical load in generated power of the at least one power generation facility, from a first state in which power is supplied from the electric path to the storage battery facility, and the water electrolysis facility does not perform water electrolysis, to a second state in which power is supplied from the electric path to the storage battery facility, and power supplied from the electric path to the water electrolysis facility is larger than that in the first state.

2. The power supply system according to claim 1, wherein the water electrolysis facility includes a control section that controls water electrolysis reaction in the water electrolysis facility in cooperation with the control unit, and power supplied from the electric path to the water electrolysis facility is less than or equal to power for operating the control section, in the first state.

3. The power supply system according to claim 1 or 2, wherein the water electrolysis facility includes an electrolyzer in which water electrolysis reaction occurs, and a heating device used for the water electrolysis reaction, the first state is a state in which power is not supplied from the electric path to the heating device, and the second state is a state in which power is supplied from the electric path to the heating device.

4. The power supply system according to claim 3, wherein a period in which the power supply system is in the second state includes a period in which power supplied from the electric path to the water electrolysis facility drives the heating device and causes the water electrolysis reaction in the electrolyzer.

5. The power supply system according to claim 3 or 4, wherein a period in which the power supply system is in the second state incudes a period in which idling is performed in the water electrolysis facility by power supplied from the electric path to the water electrolysis facility, and the idling is an operation for driving the heating device without causing the water electrolysis reaction in the electrolyzer.

6. The power supply system according to any one of claims 3 to 5, wherein an operation state of the water electrolysis facility includes an off state in which power is not supplied from the electric path to the heating device, and the heating device is not driven, and an on state in which the heating device is driven by power supplied from the electric path to the heating device, the control unit shifts the operation state of the water electrolysis facility from the off state to the on state when the surplus power is increased so as to cross a first threshold value, and shifts the operation state of the water electrolysis facility from the on state to the off state when the surplus power is decreased so as to cross a second threshold value, the second threshold value is less than the first threshold value, the water electrolysis facility is in the off state, in the first state, and the water electrolysis facility is in the on state, in the second state.

7. The power supply system according to claim 6, wherein regardless of a storage amount of the storage battery facility, the control unit shifts the operation state of the water electrolysis facility from the off state to the on state when the surplus power is increased so as to cross the first threshold value, and shifts the operation state of the water electrolysis facility from the on state to the off state when the surplus power is decreased so as to cross the second threshold value.

8. The power supply system according to claim 6, wherein in a case where a storage amount of the storage battery facility is less than a predetermined value, the control unit shifts the operation state of the water electrolysis facility from the off state to the on state when the surplus power is increased so as to cross the first threshold value, and shifts the operation state of the water electrolysis facility from the on state to the off state when the surplus power is decreased so as to cross the second threshold value, and in a case where a storage amount of the storage battery facility is the predetermined value or more, the control unit maintains the operation state of the water electrolysis facility as the on state when the surplus power is increased so as to cross the first threshold value, and maintains the operation state of the water electrolysis facility as the on state when the surplus power is decreased so as to cross the second threshold value.

9. The power supply system according to claim 6 or 8, wherein the control unit shifts the operation state of the water electrolysis facility from the off state to the on state when the surplus power is increased so as to cross a third threshold value, and shifts the operation state of the water electrolysis facility from the on state to the off state when the surplus power is decreased so as to cross a fourth threshold value, the third threshold value is less than the second threshold value, and the fourth threshold value is less than the third threshold value.

10. The power supply system according to claim 8 or 9, wherein in a case where a storage amount of the storage battery facility is less than the predetermined value, the control unit maintains the operation state of the water electrolysis facility as the off state when the surplus power is increased so as to cross a third threshold value, and maintains the operation state of the water electrolysis facility as the off state when the surplus power is decreased so as to cross a fourth threshold value, in a case where a storage amount of the storage battery facility is the predetermined value or more, the control unit shifts the operation state of the water electrolysis facility from the off state to the on state when the surplus power is increased so as to cross the third threshold value, and shifts the operation state of the water electrolysis facility from the on state to the off state when the surplus power is decreased so as to cross the fourth threshold value, the third threshold value is less than the second threshold value, and the fourth threshold value is less than the third threshold value.

11. The power supply system according to any one of claims 3 to 6 and 8 to 10, wherein an operation state of the water electrolysis facility includes an off state in which power is not supplied from the electric path to the heating device, and the heating device is not driven, and an on state in which the heating device is driven by power supplied from the electric path to the heating device, the surplus power in the case of the operation state of the water electrolysis facility being shifted from the off state to the on state is low in a case where a storage amount of the storage battery facility is a predetermined value or more, as compared with a case where a storage amount of the storage battery facility is less than the predetermined value, the water electrolysis facility is in the off state, in the first state, and the water electrolysis facility is in the on state, in the second state.

12. The power supply system according to any one of claims 3 to 6 and 8 to 11, wherein an operation state of the water electrolysis facility includes an off state in which power is not supplied from the electric path to the heating device, and the heating device is not driven, and an on state in which the heating device is driven by power supplied from the electric path to the heating device,, the control unit performs specific control, in the specific control, the operation state of the water electrolysis facility is set as the off state in a case where a storage amount of the storage battery facility is less than a predetermined value, and the operation state of the water electrolysis facility is set as the on state and power is supplied from the storage battery facility to the water electrolysis facility in a case where a storage amount of the storage battery facility is the predetermined value or more, and the surplus power is less than power required by the water electrolysis facility, the water electrolysis facility is in the off state, in the first state, and the water electrolysis facility is in the on state, in the second state.

13. The power supply system according to claim 12, wherein the control unit starts the specific control when the surplus power is increased so as to cross a third threshold value, starts the specific control when the surplus power is decreased so as to cross a second threshold value, ends the specific control when the surplus power is increased so as to cross a first threshold value, and ends the specific control when the surplus power is decreased so as to cross a fourth threshold value, the second threshold value is less than the first threshold value, the third threshold value is less than the second threshold value, and the fourth threshold value is less than the third threshold value.

14. The power supply system according to claim 1 or 2, wherein the water electrolysis facility includes an electrolyzer in which water electrolysis reaction occurs, the first state is a state in which power is not supplied from the electric path to the electrolyzer, and the second state is a state in which power is supplied from the electric path to the electrolyzer.

15. The power supply system according to any one of claims 1 to 14, wherein the control unit decreases power supplied from the electric path to the storage battery facility when the operation state of the power supply system is shifted from the first state to the second state.

16. The power supply system according to any one of claims 1 to 15, wherein the power supply system and a commercial power supply are interconnected through the electric path, and the control unit controls the at least one power generation facility, the storage battery facility, and the water electrolysis facility so as to avoid reverse power flow from the power supply system to the commercial power supply.

17. The power supply system according to any one of claims 1 to 16, wherein the at least one power generation facility includes at least one selected from the group consisting of a photovoltaic facility and a fuel cell facility.

18. The power supply system according to any one of claims 1 to 17, wherein the at least one power generation facility includes a fuel cell facility, and the power supply system comprises a hydrogen path for guiding hydrogen from the water electrolysis facility to the fuel cell facility, and a hydrogen storing section provided in the hydrogen path.

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