Power Supply System

Abstract

To provide a power supply system capable of increasing self-consumption of power generated by a power generation unit.SOLUTION: A power supply system comprises: a photovoltaic power generation unit 11 capable of generating power using natural energy; a fuel cell 30 that is capable of generating power using fuel and stores heat generated at the time of generating power; and an EMS 60 for controlling operation of the fuel cell 30. The EMS 60 predicts surplus power by which power generated by the photovoltaic power generation unit 11 exceeds a power demand and, when it is predicted that a time zone in which the surplus power is greater than a predetermined value (β) exists (Yes in a step S11), instructs the fuel cell 30 to generate power in a time zone other than the time zone in which surplus power is to be generated (step S12).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for a power supply system equipped with a power generation unit and a fuel cell. [Background technology]

[0002] Conventionally, the technology of a power supply system equipped with a power generating unit and a fuel cell has been publicly known, as described in Patent Document 1, for example.

[0003] Patent Document 1 describes a power supply system including a solar cell that generates electricity using sunlight, a fuel cell that can generate electricity using fuel such as hydrogen and can boil water using the waste heat generated during power generation, and a storage battery that can charge and discharge electricity. In this power supply system, the power generated by the solar cell and the power generated by the fuel cell can be supplied to household loads. Also, the power generated by the solar cell can be charged into the storage battery, and the power charged into the storage battery can be supplied to household loads. Also, when appropriate, surplus power (excess power) generated by the solar power generation unit can be sold (reverse power flow to a commercial power source).

[0004] However, in recent years, the selling price of electricity generated by the solar power generation unit has been on a downward trend, and in some cases is even lower than the midnight electricity price. For this reason, it is desirable to consume the electricity generated by the solar power generation unit within the home. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-48992 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and the problem it aims to solve is to provide a power supply system that can improve the self-consumption of electricity generated by the power generation unit. [Means for solving the problem]

[0007] The problem to be solved by the present invention has been described above, and the means for solving this problem will now be described.

[0008] That is, in claim 1, the present invention is provided with a power generation unit capable of generating electricity using natural energy, a fuel cell capable of generating electricity using fuel through load following operation and storing heat generated during power generation, a storage battery capable of charging and discharging electricity, and a control unit that controls the operation of the fuel cell and the storage battery, and the control unit controls the amount of electricity generated by the power generation unit that is surplus to the electricity demand. First Predict surplus power and First When it is predicted that there will be a time period in which the surplus power is greater than a predetermined value, First Instruct the power company to generate electricity during times other than when surplus electricity is generated, First When the time period other than the time period in which surplus power is generated is a night time period, a predetermined amount of power is charged to the storage battery, thereby charging the storage battery with night power and power generated by the fuel cell. and when a second surplus power predicted in consideration of the power generated by the fuel cell based on the charging instruction is predicted to be greater than the storable amount of the storage battery, charging the storage battery with midnight power and the power generated by the fuel cell for the amount of power demand until the time when power generation is started by the power generation unit is instructed to fully charge the storage battery with the midnight power and the power generated by the fuel cell when the second surplus power is predicted to be less than the storable amount of the storage battery. It is something.

[0009] In claim 2, the control unit First When it is predicted that there will be a time period in which surplus power will be greater than a predetermined value, an instruction is given to generate power during a time period other than the time period in which the amount of power purchased from the grid power source is less than the predetermined value.

[0010] In claim 3, the control unit First If it is predicted that there will be no time period during which the surplus power is greater than a predetermined value, the fuel cell is instructed to generate power during a time period other than the nighttime power period. Effect of the Invention

[0013] The present invention has the following advantages.

[0014] According to claim 1, it is possible to improve the self-consumption of the electricity generated by the power generation unit. In addition, the amount of surplus power that can be charged to the storage battery can be increased while the power required until the power generation unit starts generating electricity can be supplied by nighttime power, and utility costs can be reduced.

[0015] According to claim 2, the power generation efficiency of the fuel cell can be maintained.

[0016] In claim 3, when the cost of late-night electricity is lower than the power generation cost of the fuel cell, it is possible to reduce utility costs. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram showing a configuration of a power supply system according to an embodiment of the present invention; [Diagram 2] 1 is a flowchart showing a planned control. [Diagram 3] 11 is a flowchart showing execution control. [Figure 4] A diagram showing the power consumption and PV generated power before adjusting the power generation time of the fuel cell. [Diagram 5] A diagram showing the power consumption and PV generated power after adjusting the fuel cell power generation time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A power supply system 1 according to an embodiment of the present invention will be described below with reference to Fig. 1. In this specification, the terms "upstream side" and "downstream side" are based on the direction of power supply from a power system K.

[0021] 1 supplies power from a power grid K or generated power to a load H. The power supply system 1 is installed in a house and supplies power to the load H of the house (e.g., appliances in the house, etc.). The power supply system 1 mainly includes a power storage system 10, a distribution board 20, a fuel cell 30, a first sensor 40, a second sensor 50, and an EMS 60.

[0022] The power storage system 10 stores electric power and supplies it to a load H. The power storage system 10 is provided between a system power supply K and the load H. The power storage system 10 includes a solar power generation unit 11, a storage battery 12, and a hybrid power conditioner 13.

[0023] The solar power generation unit 11 is a device that generates power by utilizing sunlight. The solar power generation unit 11 is configured with a solar cell panel, etc. The solar power generation unit 11 is installed in a sunny location, such as on the roof of a house.

[0024] The storage battery 12 is configured to be able to charge electric power. The storage battery 12 is configured by, for example, a lithium ion battery. The storage battery 12 is connected to the solar power generation unit 11 via a hybrid power conditioner 13, which will be described later.

[0025] A discharge threshold is set for the storage battery 12. Here, the "discharge threshold" is set to ensure power in emergencies such as power outages, and indicates the minimum amount of stored electricity that is always ensured. In this specification, the "discharge threshold" is expressed as a percentage (e.g., 30%) of the storage capacity (maximum capacity) of the storage battery 12. In this embodiment, the discharge threshold of the storage battery 12 is set to 30%. In this embodiment, the discharge threshold can be set in 10% increments between 0% and 50% of the storage capacity (maximum capacity) of the storage battery 12. In addition, the storage capacity (maximum capacity) of the storage battery 12 is set to 5.4 [kWh].

[0026] The hybrid power conditioner 13 is a device that appropriately converts electric power (hybrid power conditioner). The hybrid power conditioner 13 is configured to be capable of outputting the electric power generated by the solar power generation unit 11 and the electric power discharged from the storage battery 12 to the distribution line L (load H), and to output the electric power (electric power from the system power source K and electric power generated by the fuel cell 30 described later) flowing through the distribution line L to the storage battery 12. The hybrid power conditioner 13 is also configured to be capable of acquiring information on the performance and operating state of the solar power generation unit 11 and the storage battery 12. The hybrid power conditioner 13 is connected to a midpoint (connection point P) of the distribution line L that connects the system power source K and the load H (distribution board 20) via an electric line A1. The hybrid power conditioner 13 of the storage system 10 can perform a load following operation that adjusts the electric power to be discharged (output) based on the detection result of the first sensor 40 described later, etc.

[0027] The distribution board 20 distributes power to the loads H. The distribution board 20 is provided downstream of the power storage system 10 (connection point P) and is connected to the loads H. Although only one load H is shown in FIG. 1, the distribution board 20 is connected to a plurality of loads and distributes power to each load. The distribution board 20 supplies power from the system power source K, power discharged from the storage battery 12, and power from a fuel cell 30 (described later) to the loads H.

[0028] The fuel cell 30 is a device that generates power using a gas fuel such as hydrogen. The fuel cell 30 includes a power generation unit 31 and a hot water storage tank 32.

[0029] The power generation unit 31 is a power generation section of the fuel cell 30. The power generation unit 31 is composed of a polymer electrolyte fuel cell (PEFC: Polymer Electrolyte Fuel Cell) or a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell), a control section, and the like. The power generation unit 31 performs load following operation according to the amount of power (the total power consumption of the load H of the house) detected by a second sensor 50 described later. The fuel cell 30 also has a learning function for learning information on the power consumption of the load H of the house and hot water demand. In this way, the fuel cell 30 can create a power generation plan based on the information learned by the learning function. The fuel cell 30 can also generate power according to the created power generation plan in response to an instruction from an EMS 60 described later.

[0030] The hot water storage tank 32 stores, as hot water, heat (exhaust heat) generated during power generation by the power generation unit 31. The hot water storage tank 32 stores clean water (hot water) heated by heat (exhaust heat) generated during power generation by the power generation unit 31.

[0031] The fuel cell 30 thus configured may stop power generation by the power generation unit 31 when the amount of hot water stored in the hot water storage tank 32 reaches its maximum capacity (when the hot water storage tank 32 becomes full and cannot store any more heat). The fuel cell 30 also starts power generation so that the amount of hot water stored in the hot water storage tank 32 reaches its maximum capacity by the time of the demand for hot water.

[0032] The first sensor 40 is provided in the middle of the power distribution line L. More specifically, the first sensor 40 is provided upstream of the power storage system 10 (connection point P) (immediately upstream of the connection point P). The first sensor 40 detects the voltage (supply voltage) and current (supply current) of the power flowing through the location where the first sensor 40 is provided (the power flowing upstream and the power flowing downstream).

[0033] The second sensor 50 is provided in the middle of the power distribution line L. More specifically, the second sensor 50 is provided between the power storage system 10 (connection point P) and the distribution board 20. The second sensor 50 detects the voltage (supply voltage) and current (supply current) of the power flowing through the location where the second sensor 50 is provided (the power flowing upstream and the power flowing downstream).

[0034] The EMS 60 is an energy management system that manages the operation of the power supply system 1. The EMS 60 includes an arithmetic processing unit such as a CPU, a storage unit such as a RAM or a ROM, and an input / output unit such as a touch panel. The storage unit of the EMS 60 stores in advance various information and programs used for controlling the operation of the power supply system 1. The arithmetic processing unit of the EMS 60 can operate the power supply system 1 by executing the programs and performing predetermined arithmetic processing using the various information.

[0035] The EMS 60 is electrically connected to the hybrid power conditioner 13. The EMS 60 can transmit a predetermined signal to the hybrid power conditioner 13 and control the operation of the storage battery 12 (e.g., charging and discharging the storage battery 12). The EMS 60 is also configured to be able to input a predetermined signal from the hybrid power conditioner 13 and can acquire various information (such as the remaining amount of stored power in the storage battery 12).

[0036] In addition, the EMS 60 is electrically connected to the fuel cell 30 and can control the operation of the fuel cell 30 .

[0037] In the power supply system 1 configured as described above, the storage battery 12 can be charged with power purchased from the system power source K and power generated by the solar power generation unit 11 and the fuel cell 30. In addition, in the power supply system 1, the power purchased from the system power source K, the power generated by the solar power generation unit 11 and the fuel cell 30, and the power charged in the storage battery 12 can be supplied to a load H of a house. In addition, in the power supply system 1, surplus power (excess power) generated by the solar power generation unit 11 can be sold by being reverse-flowed to the system power source K.

[0038] Next, the power supply mode in the power supply system 1 will be described.

[0039] The power supply system 1 has a first mode and a second mode as power supply modes. In the first mode described below, the storage battery 12 is charged / discharged based on the detection results of the first sensor 40 and the second sensor 50. In the second mode described below, the storage battery 12 is charged / discharged based on an instruction from the EMS 60.

[0040] When the hybrid power conditioner 13 is set to the first mode, the hybrid power conditioner 13 supplies power from the solar power generation unit 11 to the load H when power is being generated by the solar power generation unit 11. Furthermore, when the power from the solar power generation unit 11 is surplus to the power consumption of the load H, the hybrid power conditioner 13 charges the surplus power to the storage battery 12. When there is still surplus power from the solar power generation unit 11 even after charging the storage battery 12 with the maximum charging power (the maximum amount of power that the storage battery 12 can charge per unit time), the hybrid power conditioner 13 causes the surplus power to flow backward to the grid power source S.

[0041] In supplying electric power to the load H, the hybrid power conditioner 13 performs a load following operation in which the amount of discharge of the storage battery 12 is determined based on the detection result of the first sensor 40 .

[0042] On the other hand, the hybrid power conditioner 13 in which the second mode is set charges and discharges the storage battery 12 based on instructions from the EMS 60. The hybrid power conditioner 13 in which the second mode is set can charge the storage battery 12 with power (midnight power) from the power grid S, for example, based on instructions from the EMS 60.

[0043] Conventionally, the fuel cell 30 may generate power (load following operation) even during a time period when the power generated by the solar power generation unit 11 is in excess. However, in such a case, there is a problem that the power generated by the fuel cell 30 reduces the self-consumption of the power generated by the solar power generation unit 11. Therefore, the power supply system 1 performs control (planned control) to adjust the power generation time of the fuel cell 30.

[0044] Hereinafter, the planned control by the EMS 60 will be described with reference to Fig. 2. The planned control shown in Fig. 2 is for planning the operation of the storage battery 12 and the fuel cell 30. In this embodiment, the operation plan is set for the next day. The planned control is performed before the start (for example, at 11pm on the same day) of the late-night power period (the late-night period of the day when a relatively low power unit price is set).

[0045] 2, the EMS 60 predicts the power demand, PV-generated power, surplus power, and purchased power for the next day. In this process, the EMS 60 makes the prediction based on the data of the past power generation by the solar power generation unit 11, a weather forecast for the next day, etc. The EMS 60 makes the prediction under the assumption that the fuel cell 30 will not generate any power.

[0046] Here, "PV-generated power" refers to power generated by the solar power generation unit 11. Also, "surplus power" refers to the surplus of power generated by the solar power generation unit 11 and the fuel cell 30 relative to the power demand. Note that since it is assumed that the fuel cell 30 does not generate any power, the "surplus power" predicted in step S10 is the surplus of PV-generated power relative to the power demand. After performing the process of step S10, the EMS 60 proceeds to step S11.

[0047] In step S11 shown in FIG. 2, the EMS 60 determines whether or not surplus power > β (there is a time period when surplus power is greater than β). Here, β is an arbitrary threshold value equal to or greater than 0, and can be set to, for example, 2 kWh. By setting β to a value greater than 0, even if the prediction in step S10 deviates slightly, it is possible to improve (expand) the self-consumption of power generated by the solar power generation unit 11. If the EMS 60 determines that surplus power > β ("YES" in step S11), it proceeds to step S12. On the other hand, if the EMS 60 determines that surplus power > β is not true ("NO" in step S11), it proceeds to step S17.

[0048] In step S12 shown in Fig. 2, the EMS 60 issues a power generation request instruction to the fuel cell 30 in a time period other than the surplus occurrence time and in a time period other than the time period when purchased power is less than γ. Here, the "surplus occurrence time" refers to a time period when surplus power occurs (a time period when it is predicted in step S11 that surplus power > β). γ is an arbitrary threshold value equal to or greater than 0, and is set in consideration of the power generation efficiency of the fuel cell 30. γ can be set to 0.15 kW, for example. By setting γ to a value greater than 0, it is possible to maintain the power generation efficiency of the fuel cell even if the prediction in step S10 deviates slightly.

[0049] Furthermore, a "power generation request instruction" is an instruction from the EMS 60 to the fuel cell 30 regarding the power generation time. The fuel cell 30 that receives the power generation request instruction will generate power if certain conditions are met during the instructed power generation time. In other words, the fuel cell 30 does not necessarily generate power even when it receives a power generation request instruction; for example, if the amount of hot water stored in the hot water storage tank 32 has reached its maximum capacity (if the hot water storage tank 32 is full), it will not generate power.

[0050] In this way, in step S12, the EMS 60 issues a power generation request command to the fuel cell 30 during a time period other than the surplus occurrence time (a time period other than the time period predicted in step S11 that surplus power > β), thereby indirectly stopping power generation by the fuel cell 30 during the surplus occurrence time. Also, the EMS 60 issues a power generation request command to the fuel cell 30 during a time period other than the time period when the purchased power is less than γ, thereby indirectly stopping power generation by the fuel cell 30 during the time period when the purchased power is less than γ. After performing the process of step S12, the EMS 60 proceeds to step S13.

[0051] In step S13 shown in Fig. 2, the EMS 60 updates the prediction of surplus power. In this process, the EMS 60 updates the prediction of surplus power among the predictions of power demand, PV generated power, surplus power, and purchased power obtained in step S11, taking into account power generation by the fuel cell 30. Specifically, the EMS 60 performs this update on the assumption that the fuel cell 30 will generate power during the power generation time (time periods other than the time when surplus power occurs and time periods other than the time periods when purchased power is less than γ) requested in step S12. After performing the process of step S13, the EMS 60 proceeds to step S14.

[0052] In step S14 shown in FIG. 2, the EMS 60 judges whether the total surplus energy amount is greater than the storable amount (whether the total surplus energy amount is greater than the storable amount). Here, the "total surplus energy amount" indicates the total amount of surplus energy for the next day updated in step S13 (the total amount of surplus energy from 9:00 to 17:00). The "storable amount" indicates the maximum amount of energy that the storage battery 12 can store in consideration of the discharge threshold, and is calculated by "storage capacity x (1 - discharge threshold)". For example, when the discharge threshold is 30%, the storable amount is calculated by "storage capacity x (1 - 0.3)". When the EMS 60 judges that the total surplus energy amount is greater than the storable amount ("YES" in step S14), the EMS 60 proceeds to step S15. On the other hand, when the EMS 60 judges that the total surplus energy amount is not greater than the storable amount ("NO" in step S14), the EMS 60 proceeds to step S16.

[0053] Note that "YES" in step S14 indicates that even if the storage battery 12 is fully charged (charged to maximum capacity) with the total surplus power amount on the next day, there will still be surplus power generated by the solar power generation unit 11. On the other hand, "NO" in step S14 indicates that the total surplus power amount on the next day is not enough to fully charge the storage battery 12, or that if the storage battery 12 is fully charged with the total surplus power amount on the next day, there will be no surplus power generated by the solar power generation unit 11.

[0054] In step S15 shown in FIG. 2, EMS 60 sets the target remaining battery storage amount to the total power consumption during the early morning hours (from the charging end time to the surplus occurrence time (start time of the surplus occurrence time period)). Here, the "target remaining battery storage amount" indicates the target amount of dischargeable battery storage amount (to be secured) at the charging end time. Also, the "charging end time" indicates the time to end charging of late-night power, which has a low unit price for electricity, i.e., the end time of the late-night power period. After performing the processing of step S15, EMS 60 ends the planning control flow shown in FIG. 2.

[0055] On the other hand, in step S16 shown in FIG. 2, the EMS 60 sets the target remaining amount of electricity to the amount of electricity that can be stored (=electricity storage capacity×(1−discharge threshold)).

[0056] In this way, when it is predicted that even if the storage battery 12 is fully charged based on the total surplus power amount of the next day, there will still be surplus power generated by the photovoltaic power generation unit 11 ("YES" in step S14), only the amount of power required for the early morning hours is purchased (purchased) from the grid power source S (step S15). On the other hand, when it is predicted that the total surplus power amount of the next day is not enough to fully charge the storage battery 12, or that there will be no surplus power generated by the photovoltaic power generation unit 11 if the storage battery 12 is fully charged based on the total surplus power amount of the next day ("NO" in step S14), an amount of power sufficient to fully charge the storage battery 12 is purchased from the grid power source S (step S16). After performing the process of step S16, the EMS 60 ends the planning control flow shown in FIG. 2.

[0057] Meanwhile, in step S17 shown in FIG. 2, the EMS 60 issues a power generation request instruction to the fuel cell 30 during a time period other than the midnight power time period and during a time period other than the time period when the purchased power is less than γ.

[0058] In this way, in step S17, the EMS 60 issues a power generation request command to the fuel cell 30 during a time period other than the midnight power time period, thereby indirectly stopping power generation by the fuel cell 30 during the midnight power time period. Also, the EMS 60 issues a power generation request command to the fuel cell 30 during a time period other than the time period when purchased power is less than γ, thereby indirectly stopping power generation by the fuel cell 30 during the time period when purchased power is less than γ. After performing the process of step S17, the EMS 60 proceeds to step S18.

[0059] In step S18 shown in Fig. 2, the EMS 60 updates the surplus power prediction. In this process, the EMS 60 updates the surplus power prediction among the predictions of the power demand, PV generated power, surplus power, and purchased power obtained in step S11, taking into account the power generation of the fuel cell 30. Specifically, the EMS 60 performs this update on the assumption that the fuel cell 30 will generate power during the power generation time requested in step S17 (time periods other than the midnight charging time, and time periods other than the time periods when purchased power is less than γ). After performing the process of step S18, the EMS 60 ends the planning control flow shown in Fig. 2.

[0060] In this manner, the EMS 60 determines the power generation time of the fuel cell 30 and the target remaining charge amount of the storage battery 12.

[0061] Next, the execution control by the EMS 60 will be described with reference to Fig. 3. The flow shown in Fig. 3 is always executed after the flow shown in Fig. 2 has been executed.

[0062] In step S20 shown in Fig. 3, the EMS 60 determines whether the current time t is the charging time. Here, the "charging time" refers to the time during which the storage battery 12 can be charged (e.g., 11pm to 7am) and is set in advance by a resident of the house. If the EMS 60 determines that the current time t is the charging time ("YES" in step S20), it proceeds to step S21. On the other hand, if the EMS 60 determines that the current time t is not the charging time ("NO" in step S20), it proceeds to step S24.

[0063] In step S21 shown in Fig. 3, EMS 60 determines whether or not "current remaining amount of storage - (storage capacity x discharge threshold) ≧ target remaining amount of storage". Here, the "target remaining amount of storage" is determined in the planning control flow shown in Fig. 2. If EMS 60 determines that "current remaining amount of storage - (storage capacity x discharge threshold) ≧ target remaining amount of storage" ("YES" in step S21), it proceeds to step S22. On the other hand, if EMS 60 determines that "current remaining amount of storage - (storage capacity x discharge threshold) ≧ target remaining amount of storage" is not true ("NO" in step S21), it proceeds to step S23.

[0064] Note that "YES" in step S21 indicates that the amount of dischargeable power (hereinafter referred to as "dischargeable remaining amount") among the power stored in the storage battery 12 is equal to or less than the target remaining amount. On the other hand, "NO" in step S21 indicates that the amount of dischargeable power among the power stored in the storage battery 12 is greater than the target remaining amount.

[0065] In step S22 shown in Fig. 3, the EMS 60 sets the mode of the storage battery 12 to the second mode. As a result, the storage battery 12 charges with power (midnight power) from the system power source S so that the dischargeable remaining amount becomes the target remaining power storage amount. After performing the process of step S22, the EMS 60 ends the execution control flow shown in Fig. 3.

[0066] In this way, in step S22, if the "total surplus power amount>storable power amount" is not satisfied (if it is expected that the storage battery 12 will not be fully charged with the surplus power of the next day, "NO" in step S14), the target remaining storage amount is set to the storable power amount (step S16), so the storage battery 12 is charged with power (midnight power) from the grid power source S until it is fully charged. On the other hand, if the "total surplus power amount>storable power amount" is satisfied (if it is expected that the storage battery 12 will be fully charged with the surplus power of the next day, "YES" in step S14), the target remaining storage amount is set to the total power consumption amount in the early morning hours (step S15), so the storage battery 12 is not charged with power (midnight power) from the grid power source S until it is fully charged, but only the total power consumption amount in the early morning hours is charged.

[0067] 3, the EMS 60 sets the mode of the storage battery 12 to a standby mode. This prevents charging and discharging of the storage battery 12. After performing the process of step S22, the EMS 60 ends the execution control flow shown in FIG.

[0068] In this way, the dischargeable remaining amount of the storage battery 12 (the amount of power that can be discharged out of the power stored in the storage battery 12) is always ensured to be the target remaining amount during the night power hours.

[0069] 3, the EMS 60 sets the mode of the storage battery 12 to the first mode. This causes the storage battery 12 to charge the surplus power if there is any, and discharges the power if there is a shortage of power relative to the power demand. After performing the process of step S24, the EMS 60 proceeds to step S25.

[0070] In step S25 shown in FIG. 3, EMS 60 determines whether or not the current time t is in the early morning hours (from the charging end time to the surplus occurrence time (start time of the surplus occurrence time period)). If EMS 60 determines that the current time t is in the early morning hours ("YES" in step S25), it proceeds to step S26. On the other hand, if EMS 60 determines that the current time t is not in the early morning hours ("NO" in step S25), it proceeds to step S28.

[0071] In step S26 shown in Fig. 3, the EMS 60 determines whether or not "total surplus energy amount>storable energy amount+(energy storage capacity×10%)" holds. If the EMS 60 determines that "total surplus energy amount>storable energy amount+(energy storage capacity×10%)" holds ("YES" in step S26), the EMS 60 proceeds to step S27. On the other hand, if the EMS 60 determines that "total surplus energy amount>storable energy amount+(energy storage capacity×10%)" does not hold ("NO" in step S26), the EMS 60 ends the execution control flow shown in Fig. 3.

[0072] Note that "YES" in step S26 indicates that there is surplus power that is enough to fully charge the storage battery 12 even if the discharge threshold is lowered by one step. On the other hand, "NO" in step S26 indicates that there is not enough surplus power to fully charge the storage battery 12 if the discharge threshold is lowered by one step.

[0073] In step S27 shown in Fig. 3, the EMS 60 performs a process of lowering the discharge threshold by one step. In this process, if the current discharge threshold is 30%, for example, the EMS 60 changes (lowers) the discharge threshold to 20%. After performing the process of step S27, the EMS 60 ends the execution control flow shown in Fig. 3.

[0074] In this way, by lowering the discharge threshold when charging of surplus electricity is expected, the charging and discharging amount of the storage battery 12 can be increased, making it easier to cover the power consumption of the load H during the early morning hours with power from the storage battery 12, and ultimately reducing the amount of power purchased from the system power source S.

[0075] Meanwhile, in step S28 shown in FIG. 3, EMS 60 determines whether or not "discharge threshold<set value (30%)". The "set value" here is the discharge threshold set in advance by the resident of the house (before the execution control shown in FIG. 3), and is 30% in this embodiment. If EMS 60 determines that "discharge threshold<set value (30%)" is true ("YES" in step S28), it proceeds to step S29. On the other hand, if EMS 60 determines that "discharge threshold<set value (30%)" is not true ("NO" in step S28), it ends the execution control flow shown in FIG. 3.

[0076] In step S29 shown in Fig. 3, the EMS 60 performs a process of returning the discharge threshold to the set value (30%). This makes it possible to secure sufficient power in the storage battery 12 in preparation for an emergency. After performing the process of step S29, the EMS 60 ends the execution control flow shown in Fig. 3.

[0077] A specific example of setting the power generation time of the fuel cell 30 will be described below with reference to FIGS.

[0078] Fig. 4 is a diagram showing (predictions of) power consumption and PV power generation before adjusting the power generation time of the fuel cell 30. In the example shown in Fig. 4, the fuel cell 30 is constantly performing load-following operation, and is generating power (load-following operation) even during the time period when surplus power is generated (from about 7:00 to 18:00). Therefore, during the time period when surplus power is generated (from about 7:00 to 18:00), the power generated by the photovoltaic power generation unit 11 is not used to meet power demand, but is charged to the storage battery 12, and any remaining power is sold to the system power source K.

[0079] 5 is a diagram showing (prediction of) power demand (power consumption) and PV power generation, etc. after adjusting the power generation time of the fuel cell 30. In the example shown in FIG. 5, the fuel cell 30 stops power generation (no power generation request instruction is issued) during the time period when surplus power is generated (around 8:00 to 18:00 on the second day), so part of the power generated by the solar power generation unit 11 is used for power demand (self-consumed). Note that in the example shown in FIG. 5, midnight power is charged into the storage battery 12 during the midnight power period (around 1:00 to 3:00) on the second day, equivalent to the total power consumption during the early morning period.

[0080] In this way, the power supply system 1 according to this embodiment executes the planned control flow shown in FIG. 2 to set the power generation time of the fuel cell 30 to a time period when surplus power is not generated (step S12 shown in FIG. 2). In other words, power generation by the fuel cell 30 is stopped during a time period when surplus power is generated (surplus generation time period). In this way, the self-consumption rate of power generated by the solar power generation unit 11 can be improved by the amount of the reduction in power generated by the fuel cell 30. As a result, when the selling price of power generated by the solar power generation unit 11 is lower than the purchasing price of late-night power, utility costs can be reduced.

[0081] Moreover, the power supply system 1 according to this embodiment sets the power generation time of the fuel cell 30 to a time period when purchased power is relatively high (step S12 shown in FIG. 2). That is, power generation by the fuel cell 30 is stopped during a time period when purchased power is relatively low. Here, the fuel cell 30 generally has a lower power generation efficiency (and therefore overall efficiency) when operating at partial load (operation with reduced output) compared to when operating at rated power. In the power supply system 1 according to this embodiment, power generation by the fuel cell 30 is stopped during a time period when purchased power is relatively low, even during a time period when surplus power is not being generated, so that operation at a relatively low output can be prevented, and thus the power generation efficiency (and therefore overall efficiency) of the fuel cell 30 can be maintained (improved).

[0082] Furthermore, in the power supply system 1 according to this embodiment, when a relatively large amount of surplus power is expected the next day ("YES" in step S14), during the nighttime power period, power (nighttime power) from the grid power source S is not charged to the storage battery 12 until it is fully charged, but only the nighttime power corresponding to the power demand in the early morning hours is charged to the storage battery 12 (step S15). This makes it possible to reduce the amount of purchased nighttime power and increase the amount of surplus power charged to the storage battery 12. This makes it possible to improve the self-consumption rate of power generated by the solar power generation unit 11. Furthermore, when the selling price of power generated by the solar power generation unit 11 is lower than the purchasing price of nighttime power, it is possible to reduce utility costs.

[0083] On the other hand, if a relatively large amount of surplus power is not expected the next day ("NO" in step S14), power (midnight power) from the grid power source S is charged into the storage battery 12 so that the storage battery 12 is fully charged during the midnight power period (step S16). This allows the power charged into the storage battery 12 during the day to be utilized, and reduces utility costs compared to charging the storage battery 12 with power from the grid power source S during the day.

[0084] Furthermore, in the power supply system 1 according to this embodiment, if there is expected to be surplus power sufficient to fully charge the storage battery 12 even if the discharge threshold of the storage battery 12 is lowered by one step ("YES" in step S26), the discharge threshold of the storage battery 12 is lowered by one step. This allows the charge / discharge amount of the storage battery 12 to be expanded, making it easier to cover the power consumption of the load H in the early morning hours with the power from the storage battery 12, and ultimately reducing the amount of power purchased from the system power source S. Furthermore, even if the power consumption of the load H increases suddenly, it can be handled with the charging power of the storage battery 12.

[0085] As described above, the power supply system 1 of this embodiment comprises a solar power generation unit 11 (power generation unit) capable of generating electricity using natural energy, a fuel cell 30 capable of generating electricity using fuel and storing heat generated during power generation, and an EMS 60 (control unit) that controls the operation of the fuel cell 30. The EMS 60 predicts surplus power generated by the solar power generation unit 11 that is in excess of power demand, and if it is predicted that there will be a time period during which the surplus power is greater than a predetermined value (β) (YES in step S11 shown in Figure 2), it instructs the fuel cell 30 to generate power during a time period other than the time period during which the surplus power is generated (step S12 shown in Figure 2).

[0086] With this configuration, it is possible to improve the self-consumption of the electricity generated by the solar power generation unit 11. Specifically, by setting the power generation time of the fuel cell 30 to a time period when surplus power is not generated (i.e., by stopping power generation by the fuel cell 30 during a time period when surplus power is generated (surplus generation time period)), the self-consumption rate of the power generated by the solar power generation unit 11 can be improved by the amount of the reduction in the power generated by the fuel cell 30. Furthermore, the fuel cell 30 may not be able to generate power when the hot water tank 32 becomes full. For this reason, if the fuel cell 30 is allowed to generate power during a time period when surplus power is generated (surplus generation time period), the hot water tank 32 will become full early, and even if the fuel cell 30 is to be forced to generate power during a time period when surplus power is not generated, it may not be able to generate power. In the power supply system 1 according to this embodiment, by stopping the power generation of the fuel cell 30 during a time period when surplus power is generated (surplus generation time period), it is possible to prevent the hot water tank 32 from becoming full early, and in turn, it is possible to prevent the fuel cell 30 from being unable to generate power during a time period when surplus power is not generated.

[0087] In addition, when it is predicted that there will be a time period in which the surplus power is greater than a predetermined value (β) (YES in step S11 shown in FIG. 2), the EMS 60 instructs the EMS 60 to generate power during a time period other than the time period in which the amount of power purchased from the grid power source K is less than a predetermined value (γ) (step S12 shown in FIG. 2).

[0088] With this configuration, the power generation efficiency of the fuel cell 30 can be maintained. Specifically, since the fuel cell 30 is prevented from operating at a relatively low output, the power generation efficiency of the fuel cell 30 can be maintained (improved).

[0089] In addition, if it is predicted that there is no time period during which the surplus power is greater than a predetermined value (β) (NO in step S11 shown in Figure 2), the EMS 60 instructs the fuel cell 30 to generate power during a time period other than the late-night power time period (step S17 shown in Figure 2).

[0090] With this configuration, when the late-night electricity is lower than the power generation cost of the fuel cell 30, it is possible to reduce utility costs. Specifically, by stopping power generation by the fuel cell 30 during the night power hours, the night power can be used to meet power demand, and if the night power is lower than the power generation cost of the fuel cell 30, utility costs can be reduced.

[0091] Furthermore, the power supply system 1 according to this embodiment includes a storage battery 12 capable of charging and discharging power, and when it is predicted that the surplus power is greater than the amount of power that can be stored in the storage battery 12 (YES in step S14 shown in FIG. 2), the EMS 60 charges the storage battery with late-night power equivalent to the amount of power demand until the time when power generation is started by the power generation unit (step S15 shown in FIG. 2).

[0092] With this configuration, it is possible to increase the amount of surplus power charged to the storage battery 12 while using late-night power to cover the power consumed until the time when the solar power generation unit 11 starts generating power (total power consumption during the early morning hours). Specifically, since the late-night power is charged to the storage battery 12 only in the amount of total power consumption during the early morning hours, the amount of surplus power charged to the storage battery 12 can be increased.

[0093] Furthermore, the power supply system 1 according to this embodiment includes a storage battery 12 capable of charging and discharging power, and when it is predicted that the surplus power is less than the amount of power that can be stored in the storage battery 12 (NO in step S14 shown in FIG. 2), the EMS 60 fully charges the storage battery with nighttime power (step S16 shown in FIG. 2).

[0094] With this configuration, it is possible to reduce utility costs. Specifically, since the late-night power charged in the storage battery 12 can be used during the day, it is possible to reduce utility costs.

[0095] Although the embodiment of the present invention has been described above, the present invention is not limited to the above configuration, and various modifications are possible within the scope of the invention described in the claims.

[0096] For example, in the present embodiment, the power supply system 1 is provided in a house, but the present invention is not limited to this and may be provided in, for example, an office or the like.

[0097] Furthermore, in this embodiment, the power generation unit is the solar power generation unit 11 that generates power using sunlight, but it may be one that generates power using other natural energy (for example, hydropower or wind power).

[0098] In addition, in this embodiment, in step S12 shown in Figure 2, the EMS 60 issues a power generation request instruction to the fuel cell 30 during time periods other than the time when surplus power occurs and during time periods other than the time when purchased power is less than γ, but the power generation request instruction may be issued only during time periods other than the time when surplus power occurs.

[0099] In addition, in this embodiment, in step S14 shown in FIG. 2, it is determined whether the total surplus energy amount is greater than the storable amount (the total surplus energy amount is greater than the storable amount), but it may also be determined whether the total surplus energy amount is greater than or equal to the storable amount (the total surplus energy amount is equal to or greater than the storable amount). [Explanation of symbols]

[0100] 1. Power supply system 11. Solar Power Generation Department 12 Storage battery 30 Fuel Cell 60 EMS

Claims

1. A power generation unit capable of generating electricity using natural energy; A fuel cell capable of generating electricity using fuel through load following operation and storing heat generated during the power generation; A storage battery capable of charging and discharging electricity; A control unit that controls the operation of the fuel cell and the storage battery; Equipped with The control unit is predicting a first surplus power that is surplus to the power demand among the power generated by the power generation unit; when it is predicted that there will be a time period during which the first surplus power is greater than a predetermined value, instructing the fuel cell to generate power during a time period other than the time period during which the first surplus power is generated; when a time period other than the time period during which the first surplus power is generated is a night time period, instructing the storage battery to charge a predetermined amount of power, thereby charging the storage battery with night power and power generated by the fuel cell; When a second surplus power predicted in consideration of the power generated by the fuel cell based on the charging instruction is predicted to be greater than the amount of power that can be stored in the storage battery, the storage battery is charged with midnight power and the power generated by the fuel cell for an amount of power demand until the time when power generation is started by the power generation unit; When it is predicted that the second surplus power is less than the amount of power that can be stored in the storage battery, the storage battery is fully charged with midnight power and the power generated by the fuel cell. Power supply system.

2. The control unit is when it is predicted that there will be a time period in which the first surplus power is greater than a predetermined value, instructing the power generation system to generate power during a time period other than the time period in which the amount of power purchased from the grid power source is less than a predetermined value; The power supply system according to claim 1 .

3. The control unit is when it is predicted that there will be no time period during which the first surplus power is greater than a predetermined value, instructing the fuel cell to generate power during a time period other than a nighttime power period; The power supply system according to claim 1 or 2.

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