JP7788902B2 - fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system that supplies energy generated by a solid oxide fuel cell, which can be selectively controlled to operate or stop, to an energy load section.

Fuel cells, particularly solid oxide fuel cells, are highly efficient but have low tolerance for start-stops, making them suitable for continuous operation. Of course, fuel cells are capable of load-following operation, which changes the power they generate depending on the magnitude of the power load on the power load section. However, when the power load or heat load is very small, even when the fuel cell is operated at minimum output, excess power and heat will be generated by the fuel cell, reducing the operational benefits that would be obtained by operating the fuel cell (for example, reduced primary energy consumption, reduced energy costs, reduced carbon dioxide emissions, etc.). Therefore, when the power load or heat load is very small, it is necessary to stop fuel cell operation.

Patent Document 1 (JP 2011-198768 A) discloses a control system that automatically shuts down a solid oxide fuel cell if the power supply from the solid oxide fuel cell to a load remains below a certain level for a certain period of time, and automatically starts up the solid oxide fuel cell if the power supply from the grid to the load remains above a certain level for a certain period of time. It also discloses DSS (daily start-stop) operation, which shuts down power generation at night when power consumption is low and starts up in the morning.

Patent Document 2 (JP 2017-174750 A) describes a system that, unlike DSS operation, which involves repeatedly stopping and starting a fuel cell in short intervals, determines the magnitude of the operating benefits of a fuel cell over a relatively long period of time, and operates the fuel cell if the operating benefits are large, and stops the operation if the operating benefits are small.

JP 2011-198768 A JP 2017-174750 A

Furthermore, if a power outage occurs and the fuel cell system is stopped, it will not be able to receive power. Therefore, it may not be advisable to stop the fuel cell system even if there is little benefit to operating it.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a fuel cell system that can start and stop operation of a solid oxide fuel cell at appropriate times while taking into account future power outages.

A characteristic configuration of a fuel cell system according to the present invention for achieving the above object is a fuel cell system that supplies energy generated from a solid oxide fuel cell that can be selectively controlled to operate or stop its operation to an energy load unit, and
a load measuring unit that measures load energy required by the energy load unit;
a load calculation unit that calculates an average calculation value of the load measurement values of the load measurement unit measured over a predetermined determination period;
an operation determination unit that outputs a determination result that the solid oxide fuel cell should be operated or stopped based on the result of an operation feasibility determination process that makes a provisional determination that the solid oxide fuel cell should be operated or stopped based on the average calculation value or a substitute value derived from the average calculation value and a determination threshold value, the result of a power outage possibility determination process that determines the degree of possibility of a power outage occurring in a future power outage determination period, and the result of a cost verification process that verifies a first operating cost that will be required to continue operating the solid oxide fuel cell until a predicted power outage date and time within the power outage determination period if a power outage is likely to occur in the power outage determination period, and a second operating cost that will be required to complete start-up of the solid oxide fuel cell at the predicted power outage date and time after the operation of the solid oxide fuel cell is stopped;
a threshold value setting unit that sets the determination threshold value;
an operation control unit that issues an operation execution command or an operation stop command to the solid oxide fuel cell based on the determination result output by the operation determination unit ,
The operation determination unit outputs the determination result that the operation of the solid oxide fuel cell should be stopped if the operation feasibility determination process provisionally determines that operation should be stopped, the power outage possibility determination process determines that there is a high possibility of a power outage, and the cost verification process determines that the first operating cost is greater than the second operating cost .

Here, the alternative value is a function value of an operating merit function that derives the operating merit of the solid oxide fuel cell from the average calculated value, and the threshold setting unit may set a judgment threshold converted into the operating merit as the merit judgment threshold.
The operational merit may be a reduction in primary energy consumption, a reduction in energy costs, or a reduction in carbon dioxide emissions obtained by operating the solid oxide fuel cell, or a combination thereof.

According to the above characteristic configuration, the operation determination unit outputs a determination result that the solid oxide fuel cell should be operated or stopped based on the result of an operation feasibility determination process that makes a provisional determination as to whether the solid oxide fuel cell should be operated or stopped based on a determination threshold and either an average calculated value of load measurement values measured over a predetermined determination period by a load measurement unit that measures the load energy required by the energy load unit or an alternative value derived from the average calculated value ; the result of a power outage possibility determination process that determines the degree of likelihood of a power outage occurring in a future power outage determination period; and the result of a cost verification process that verifies a first operating cost that will be required if the operation of the solid oxide fuel cell is continued until the predicted power outage date and time within the power outage determination period if there is a high possibility of a power outage occurring during the power outage determination period, and a second operating cost that will be required if the start-up of the solid oxide fuel cell is completed at the predicted power outage date and time after the operation of the solid oxide fuel cell is stopped. The operation control unit issues an operation execution command or an operation stop command to the solid oxide fuel cell based on the determination result output by the operation determination unit. In other words, the operation determination unit determines whether to operate or stop the solid oxide fuel cell not only by considering past load energy values, but also by considering the likelihood of a power outage during a future power outage determination period. Additionally, even if the power outage possibility determination process determines that a power outage is likely, i.e., it would be preferable to operate the solid oxide fuel cell, if the cost verification process determines that the first operating cost is greater than the second operating cost, i.e., if it would be less costly to temporarily stop operation of the solid oxide fuel cell and then complete startup at the predicted power outage date and time, the operation determination unit outputs a determination result that the solid oxide fuel cell should be stopped. In other words, the solid oxide fuel cell can be operated at lower costs while ensuring that it is in operation at the predicted power outage date and time.
Therefore, it is possible to provide a fuel cell system that can start and stop operation of the solid oxide fuel cell at appropriate times while taking into consideration how to deal with future power outages.

Another characteristic configuration of the fuel cell system of the present invention is that the operation determination unit outputs the determination result that the solid oxide fuel cell should be operated if the operation feasibility determination process provisionally determines that operation should be stopped, the power outage possibility determination process determines that there is a high possibility of a power outage, and the cost verification process determines that the first operating cost is not greater than the second operating cost .

According to the above-described characteristic configuration, if the operation feasibility determination process provisionally determines that operation should be stopped, the power outage possibility determination process determines that a power outage is likely, and the cost verification process determines that the first operating cost is not greater than the second operating cost , the solid oxide fuel cell can be kept operating. As a result, even if a power outage occurs, power can be supplied from the fuel cell system.

Another characteristic feature of the fuel cell system according to the present invention is that, if the operation feasibility determination process provisionally determines that operation should be performed, the operation control unit outputs the determination result that the solid oxide fuel cell should be operated.

With the above characteristic configuration, if the operation feasibility determination process provisionally determines that operation should be performed, the solid oxide fuel cell can be left in operation. As a result, power can be supplied from the fuel cell system.

Another characteristic feature of the fuel cell system of the present invention is that the operation control unit outputs a determination result that the operation of the solid oxide fuel cell should be stopped if the operation feasibility determination process provisionally determines that operation should be stopped and the power outage possibility determination process determines that the possibility of a power outage is low.

With the above-described configuration, if the operation feasibility determination process provisionally determines that operation should be stopped, and the power outage possibility determination process determines that the possibility of a power outage is low, the operation of the solid oxide fuel cell can be stopped. As a result, it is possible to avoid continuing to operate the solid oxide fuel cell in a state where there is little benefit to operating it.

FIG. 1 is a diagram showing a basic configuration of equipment including a fuel cell system. FIG. 2 is a diagram showing the flow of information in control of selecting whether to operate or stop the operation of a solid oxide fuel cell in a fuel cell system. 5A and 5B are diagrams illustrating various calculation values calculated based on load measurement values. 10 is a graph showing the relationship between the standard deviation of the load measurement value and the merit determination threshold value. 4 is a flowchart illustrating a determination as to whether to operate or stop the solid oxide fuel cell of the first embodiment. 10 is a flowchart illustrating a driving possibility determination process. 10 is a flowchart illustrating another driving possibility determination process. 1 is a functional block diagram illustrating an example of an embodiment of a fuel cell system. 10 is a flowchart illustrating a determination as to whether to operate or stop the solid oxide fuel cell of the second embodiment. 10 is a flowchart illustrating a determination as to whether to operate or stop the solid oxide fuel cell according to the third embodiment.

First Embodiment
A fuel cell system according to a first embodiment of the present invention will be described below with reference to the drawings. First, the basic configuration of equipment including a fuel cell system according to the present invention will be described with reference to the functional block diagram of FIG. 1 . As shown in FIG. 1 , the fuel cell system includes a solid oxide fuel cell 1 that supplies energy generated by operation to an energy load unit L, and an operation control device 100 that controls the operation of the solid oxide fuel cell 1. The energy load unit L is composed of a power load unit 3 and a heat load unit 4. Electrical energy generated by operation of the solid oxide fuel cell 1 is supplied to the power load unit 3, and thermal energy generated by operation of the solid oxide fuel cell 1 is supplied to the heat load unit 4. The power load unit 3 can consume power supplied from a commercial power source 15, and the heat load unit 4 can consume heat supplied from, for example, an auxiliary heat source device 11 that generates heat by burning fuel. The operation control device 100 can be implemented using a computer system having information processing, information storage, information communication, and other functions.

[Power supply to power load unit 3]
The power generated by the solid oxide fuel cell 1 is supplied to an inverter 12. The inverter 12 adjusts the power generated by the solid oxide fuel cell 1 to the same voltage and frequency as the power received from a commercial power source 15. The operation of the inverter 12 is controlled by an operation control device 100. The inverter 12 is electrically connected to a received power supply line 14 via a generated power supply line 13. The power generated from the solid oxide fuel cell 1 is supplied to a power load unit 3 via the inverter 12, the generated power supply line 13, and the received power supply line 14. Since the received power supply line 14 is connected to the commercial power source 15, the power load unit 3 is supplied with power from at least one of the solid oxide fuel cell 1 and the commercial power source 15.

The incoming power supply line 14 is provided with a power load measuring means 16 as a load measuring unit S that measures the power load of the power load unit 3. The operation control device 100 controls the generated power supplied from the solid oxide fuel cell 1 to the incoming power supply line 14 by the inverter 12 so that it is equal to the power load detected by the power load measuring means 16. However, if the power load detected by the power load measuring means 16 is less than the minimum generated power of the solid oxide fuel cell 1 (i.e., the minimum generated power supplied to the incoming power supply line 14 by the inverter 12), surplus power is generated. In such cases, the surplus power is consumed by the surplus power consuming electric heater 9, which converts power into heat and recovers it.

The electric heater 9 is composed of multiple resistance heaters and heats the cooling water for the solid oxide fuel cell 1 flowing through the exhaust heat recovery path 6 when the exhaust heat recovery pump 7 is activated. The electric heater 9 is turned on and off by an activation switch 10 connected to the output side of the inverter 12. The activation switch 10 is also switched so that the power consumption of the electric heater 9 increases as the amount of surplus power in the solid oxide fuel cell 1 increases. The operation of the activation switch 10 is controlled by the operation control device 100.

The types of devices included in the power load unit 3 can be set as appropriate. For example, it is possible to exclude from the power load unit 3 of this embodiment auxiliary equipment used to operate the solid oxide fuel cell 1, anti-freeze heaters that prevent the hot water supplied to the heat load unit 4 from freezing, and the like. Furthermore, the standby power of the power load unit 3 may be subtracted from the power load measured in this embodiment.

[Supply of heat to heat load section 4]
The hot water storage tank 2 stores heat generated by the solid oxide fuel cell 1 in the form of hot water. In this embodiment, the hot water is stored in the hot water storage tank 2 in a state that forms temperature stratification. That is, the hot water storage tank 2 is configured so that relatively low-temperature hot water is stored in the lower part and relatively high-temperature hot water is stored in the upper part. The hot water stored in the hot water storage tank 2 circulates between the solid oxide fuel cell 1 and the hot water storage tank 2 through the exhaust heat recovery path 6. The flow of hot water in the exhaust heat recovery path 6 is controlled by an exhaust heat recovery pump 7. The operation of the exhaust heat recovery pump 7 is controlled by the operation control device 100. For example, when the operation of the solid oxide fuel cell 1 is started and it becomes necessary to cool the solid oxide fuel cell 1, the operation control device 100 operates the exhaust heat recovery pump 7 to flow the relatively low-temperature hot water stored in the lower part of the hot water storage tank 2 into the exhaust heat recovery path 6. That is, the hot water circulating through the exhaust heat recovery path 6 is used as cooling water for the solid oxide fuel cell 1. The relatively low-temperature hot water flowing through the exhaust heat recovery path 6 recovers the heat emitted from the solid oxide fuel cell 1 (i.e., the hot water is heated by the exhaust heat from the solid oxide fuel cell 1), and becomes relatively high-temperature hot water, which flows into the top of the hot water storage tank 2.

In addition, a radiator 8 is installed along the exhaust heat recovery path 6 to radiate heat from the hot water flowing from the hot water storage tank 2 to the solid oxide fuel cell 1 through the exhaust heat recovery path 6. The operation control device 100 stops the operation of this radiator 8 when the temperature of the hot water flowing from the hot water storage tank 2 to the solid oxide fuel cell 1 is below a set upper limit temperature. However, when the temperature of the hot water flowing from the hot water storage tank 2 to the solid oxide fuel cell 1 is above the set upper limit temperature (i.e., when the hot water cannot adequately cool the solid oxide fuel cell 1), the operation control device 100 activates the radiator 8 to radiate heat and lower the temperature of the hot water. Furthermore, Joule heat generated by energizing the electric heater 9 described above is recovered by the hot water flowing along the exhaust heat recovery path 6 from the solid oxide fuel cell 1 to the hot water storage tank 2.

Relatively high-temperature hot water stored in the upper part of the hot water storage tank 2 is supplied to the heat load section 4 through the hot water supply path 5 connected to the upper part of the hot water storage tank 2. The heat load section 4 is used for hot water supply or heating, etc. When the heat load section 4 is used for hot water supply, the hot water does not return to the hot water storage tank 2. When the heat load section 4 is used for heating, only the heat contained in the hot water is consumed and the hot water may return to the hot water storage tank 2. The hot water supply path 5 is provided with an auxiliary heat source device 11 for heating the hot water flowing through the hot water supply path 5. When the temperature of the hot water flowing out from the upper part of the hot water storage tank 2 is lower than the hot water temperature required by the heat load section 4, the operation control device 100 operates the auxiliary heat source device 11 to control the temperature of the hot water supplied to the heat load section 4 to the desired temperature. A heat load measurement means 17 is provided midway along the hot water supply path 5 as a load measurement section S, which measures the amount of heat consumed by the heat load section 4.

The operator of the fuel cell system can use an information input/output device IOD to exchange information with the operation control device 100. The information input/output device IOD includes a communication terminal that is generally installed under the name of a bathroom remote control or kitchen remote control, and such remote controls are equipped with operation buttons, an information display unit, an audio output unit, etc.

Next, using Figure 2, we will explain the flow of information in the control that selects whether to operate the solid oxide fuel cell 1 in the fuel cell system (including continuing operation and starting a new operation) or stop operation (including continuing stoppage and stopping a new operation).
2, the operation control device 100 receives the load measurement value (indicated by Lo in FIG. 2) from the load measurement unit S and power outage related information from the information providing server 300, and outputs an operation execution command or an operation stop command to the solid oxide fuel cell 1. The load measurement unit S measures the load energy required by the energy load unit L at predetermined sampling intervals (for example, one hour to several hours) over a predetermined determination period (for example, one month), and repeats the measurement process of sending the load measurement value to the operation control device 100.

In the example shown in FIG. 2 , the functional units that perform the basic functions of the operation control device 100 are the load calculation unit 51, the threshold setting unit 52, the operation determination unit 53, and the operation control unit 54. The load calculation unit 51 calculates an average calculated value of the load measurement values. The average calculated value can be a value that represents a group of load measurement values over a predetermined period, such as an arithmetic mean value, a weighted mean value, a median value, or a mode value. However, the arithmetic mean value is generally used. When the operation control device 100 handles not only the average calculated value but also a substitute value derived from this average calculated value, the load calculation unit 51 calculates this substitute value. The substitute value is a function value derived using the average calculated value as a variable, a so-called conversion value. Here, the substitute value is the function value of an operating merit function that derives the operating merit of the solid oxide fuel cell 1 from the average calculated value. In other words, if the average calculated value is E and the substitute value (operating merit value) is M, the function formula can be expressed as M = h(E). The operating merit is the reduction in primary energy consumption, energy costs, or carbon dioxide emissions obtained by operating the solid oxide fuel cell 1, or a combination of these, and the operating merit increases as the load increases. However, because there is a limit to the amount of load that the solid oxide fuel cell 1 can handle, the increase in operating merit gradually levels off in areas with heavy loads. For example, if the horizontal axis represents the load and the vertical axis represents the operating merit, the graph shape of the operating merit function will resemble a logarithmic function. In practice, the operating merit function can be determined by statistical processing using experimental values, empirical values, etc.

The operation determination unit 53 can perform an operation feasibility determination process that makes a provisional determination as to whether the solid oxide fuel cell 1 should be operated or stopped based on the average calculated value or a substitute value derived from the average calculated value and a determination threshold value, and a power outage possibility determination process that determines the likelihood of a power outage occurring during a future power outage determination period.

[Drivability determination process]
The driving judgment unit 53 compares the average calculated value or the alternative value (driving merit value) with the corresponding judgment threshold value, and if it exceeds the judgment threshold value, it provisionally judges that driving should be carried out, and if it is below the judgment threshold value, it provisionally judges that driving should be stopped.

In the basic configuration of the threshold setting unit 52, when an average calculated value is used for the operation judgment, the threshold setting unit 52 pre-calculates, as a judgment threshold Th, the boundary value between the range of average calculated values where it is considered better to operate the solid oxide fuel cell 1 and the range of average calculated values where it is considered better to suspend operation of the solid oxide fuel cell 1. When an alternative value (operating merit value), which is a function value of the operating merit function, is used for the operation judgment, the boundary value between the range of alternative values where it is considered better to operate the solid oxide fuel cell 1 and the range of alternative values where it is considered better to suspend operation of the solid oxide fuel cell 1 is pre-calculated as a merit judgment threshold mTh (a judgment threshold converted into an operating merit value).

If the average calculated value or alternative value is simply used to make an operation judgment, the variability in the load measurement values used as the original data when calculating the average calculated value will not be taken into consideration. This means that the same operation judgment may be made when the load measurement values are distributed over a wide range and when they are densely distributed around a specific value. According to the inventor's knowledge, a state in which the load measurement values are distributed variably offers greater operational benefits than a state in which the load measurement values are densely distributed.

A method for incorporating the degree of variation in load measurement values into driving judgment will be explained using Figure 3. The load calculation unit 51 calculates the standard deviation (denoted by σ in Figure 3) for the target period based on the load measurement values included in each section into which the target period is divided. The average calculated value of the load measurement values sampled during the target period is denoted by E, and the average calculated value of the load measurement values for each section is denoted by ei (i is a subscript that identifies the section). The standard deviation: σ is calculated using a well-known formula from k average calculated values: ei. Furthermore, the load calculation unit 51 calculates an evaluation merit value that takes into account the degree of variation in the load measurement values. The first value is a function value derived from the driving merit function using a lower value obtained by subtracting the standard deviation from the average calculated value, and the second value is a function value derived from the driving merit function using an upper value obtained by adding the standard deviation to an alternative value. For example, the average value between the first value and the second value. The calculation of this evaluation merit value can be expressed as the formula MV = (1/2) x (h(E - σ) + h(E + σ)). Here, MV is the evaluation merit value, σ is the standard deviation, E is the average calculated value, and h() is the operation merit function. The evaluation merit value calculated in this way is compared with the merit determination threshold mTh by the operation determination unit 53, and a provisional determination is made as to whether the solid oxide fuel cell 1 should be operated or stopped.

A method for incorporating the degree of variation in load measurement values into operation judgment, other than the method of using an evaluation merit value calculated using the standard deviation of load measurement values as a variable, is described below. In this method, the threshold setting unit 52 sets the merit judgment threshold as a function value derived using the standard deviation calculated by the load calculation unit 51 as described above. In other words, the merit judgment threshold is changed depending on the degree of variation in the load measurement values. Specifically, the merit judgment threshold is set as a function value of the standard deviation of the load measurement values (daily load), and this function increases the merit judgment threshold as the standard deviation increases. Figure 4 shows an example of such a function in graph form. In this way, by using a merit judgment threshold that dynamically changes depending on the standard deviation of the load measurement values, the degree of variation in the load measurement values can be incorporated into operation judgment. When the energy load measured by the load measurement unit S and used for operation judgment includes both thermal load energy and power load energy, a function can be used to derive an integrated load measurement value using the load measurement values of thermal load energy and power load energy as variables. By using this integrated load measurement value as the load measurement value, the above-mentioned driving judgment can be made.

[Power outage possibility determination process]
For example, information regarding the planned power outage date and time for a planned power outage is transmitted as power outage-related information to the operation determination unit 53 from the information providing server 300. Then, if the planned power outage date and time exists within a future power outage determination period, the operation determination unit 53 determines that there is a high possibility that a power outage will occur during that power outage determination period, and if there is no planned power outage date and time within the future power outage determination period, the operation determination unit 53 determines that there is a low possibility that a power outage will occur during that power outage determination period.

Alternatively, the operation determination unit 53 receives meteorological information such as the predicted typhoon path, predicted central pressure, and predicted maximum wind speed from the information providing server 300 as power outage-related information. The information providing server 300 also transmits actual power outage occurrence status and other information as power outage-related information to the operation determination unit 53. If the weather information predicts that a typhoon will pass within a set distance during a future power outage determination period, the operation determination unit 53 determines that there is a high possibility of a power outage occurring during that power outage determination period. If the weather information predicts that a typhoon will not pass within a set distance during a future power outage determination period, the operation determination unit 53 determines that there is a low possibility of a power outage occurring during that power outage determination period. When the operation determination unit 53 determines that there is a high possibility of a power outage occurring, it may set the predicted power outage date and time as the date and time when the installation location of the fuel cell system, which can be identified by the customer's address, is predicted to be within a set distance from the typhoon's center or when it is predicted to be in the typhoon's storm zone.

The conditions under which the operation determination unit 53 determines that a power outage is likely to occur can be set as appropriate. For example, the operation determination unit 53 may determine that a power outage is likely to occur if a typhoon will pass within a set distance within a future power outage determination period and the predicted central pressure of the typhoon at the date and time when the typhoon is predicted to enter within the set distance is below 960 hPa. Alternatively, the operation determination unit 53 may determine that a power outage is likely to occur if a typhoon will pass within a set distance within a future power outage determination period and the predicted maximum wind speed of the typhoon at the date and time when the typhoon is predicted to enter within the set distance is 33 m/s or higher. Alternatively, the operation determination unit 53 may determine that a power outage is likely to occur if a typhoon will pass within a set distance within a future power outage determination period and a power outage has already occurred in the area where the typhoon passed.

FIG. 5 is a flowchart illustrating the determination made by the operation determination unit 53 as to whether to operate or stop the solid oxide fuel cell 1 .
In step #10, the operation determination unit 53 determines whether it is the timing for operation determination, that is, whether it is the day to determine whether operation/stop is to be performed. For example, if the timing for this operation determination is set to once a month at the end of the month, and the operation determination unit 53 determines using the calendar function that the current time is the end of the month (determining "Yes" in step #10), it proceeds to step #11. On the other hand, if the operation determination unit 53 determines using the calendar function that the current time is not the end of the month (determining "No" in step #10), it repeats the determination in step #10.

In step #11, the operation determination unit 53 performs an operation feasibility determination process. Figure 6 is a flowchart illustrating the operation feasibility determination process. In this case, the operation determination unit 53 reads the power load measurement values accumulated by the load calculation unit 51 over the determination period (one month) and calculates an average calculated value, which is, for example, the power load measurement value per day, for example, using the arithmetic mean (step #30). The operation determination unit 53 compares the calculated average calculated value with a determination threshold value set by the threshold setting unit 52, for example, 4.1 kWh/day (step #31). If the average calculated value is equal to or greater than the determination threshold value ("Yes" in step #31), the operation determination unit 53 provisionally determines that operation should be performed (step #32). If the average calculated value is below the determination threshold value ("No" in step #31), the operation determination unit 53 provisionally determines that operation should be stopped (step #33).

Figure 7 is a flowchart illustrating another operation feasibility determination process. In this case, the operation determination unit 53 reads the power load measurement values accumulated over the determination period (one month) by the load calculation unit 51, calculates their average calculation value (e.g., arithmetic mean value), and derives an evaluation merit value from the average calculation value using an operation merit function (step #40). The operation determination unit 53 compares the derived evaluation merit value with the merit determination threshold set by the threshold setting unit 52 (step #41). If the evaluation merit value is equal to or greater than the merit determination threshold ("Yes" in step #41), the operation determination unit 53 provisionally determines that operation should be performed (step #42). If the evaluation merit value is below the merit determination threshold ("No" in step #41), the operation determination unit 53 provisionally determines that operation should be stopped (step #43).

Next, in step #12 of Figure 5, the driving determination unit 53 proceeds to step #13 if the result of the provisional determination of the driving feasibility determination process is that driving should be stopped, and proceeds to step #16 if the result of the provisional determination of the driving feasibility determination process is that driving should be performed.

In step #13, the operation determination unit 53 performs a power outage possibility determination process, and if a planned power outage date and time exists within the future power outage determination period, it determines that there is a high possibility of a power outage occurring during that power outage determination period, and if there is no planned power outage date and time within the future power outage determination period, it determines that there is a low possibility of a power outage occurring during that power outage determination period. Then, in step #14, if the operation determination unit 53 determines that there is a high possibility of a power outage occurring, it proceeds to step #16, and if it determines that there is a low possibility of a power outage occurring, it proceeds to step #17.

In step #16, the operation determination unit 53 outputs a determination result that operation should be performed to the operation control unit 54. In step #17, the operation determination unit 53 outputs a determination result that operation should be stopped to the operation control unit 54. Then, the operation control unit 54 outputs an operation execution command or an operation stop command to the solid oxide fuel cell 1 based on the determination result of the operation determination unit 53.

In this embodiment, the operation control unit 54 is configured to issue an operation execution command to the solid oxide fuel cell 1 if the operation feasibility determination process provisionally determines that operation should be stopped, but if the power outage possibility determination process determines that a power outage is highly likely. Furthermore, the operation control unit 54 is configured to issue an operation execution command to the solid oxide fuel cell 1 if the operation feasibility determination process provisionally determines that operation should be performed. Furthermore, the operation control unit 54 is configured to issue an operation stop command to the solid oxide fuel cell 1 if the operation feasibility determination process provisionally determines that operation should be stopped, and if the power outage possibility determination process determines that a power outage is highly unlikely.

When this operation control device 100 is used, the operation of the solid oxide fuel cell 1 is automatically started or stopped based on the determination result of the operation determination unit 53. However, if the final decision on whether to start or stop operation is left to the user, the determination result of the operation determination unit 53 is notified to the user via a remote control, typically installed as a bathroom remote control or kitchen remote control, and an operation start command or operation stop command is given in response to the user's instruction using the remote control.

Next, several operating modes of the fuel cell system described above will be explained. Figure 8 shows an example of a common system configuration that can realize these operating modes. Here, the operation control device 100 is equipped with each functional unit described using Figure 2, and a remote control LC installed in the bathroom or kitchen is used as the information input/output device IOD of the operation control device 100. Furthermore, the operation control device 100 can be connected via the communication unit 50 to a remote management center (management computer) 200 operated by the management company that manages this fuel cell system so as to be able to exchange data, and can be connected to an information providing server 300 so as to be able to exchange data.

Here, the load calculation unit 51, threshold setting unit 52, driving determination unit 53, and driving control unit 54, which constitute the functions of the driving control device 100, are similar to those described above with reference to Figure 2. In addition to the above, the driving control device 100 also includes a driving merit function storage unit 55, an output data processing unit 56, an input data processing unit 57, and a notification processing unit 58. In this embodiment, the driving merit function storage unit 55 stores, in the form of a lookup table, the driving merit function M = h(E), which derives the driving merit value (a type of alternative value): M, which indicates the driving merit, from the average calculated value: E calculated by the load calculation unit 51, as described with reference to Figures 2 and 3. Furthermore, the driving merit function storage unit 55 stores, in the form of a lookup table, the formula for deriving the evaluated merit value from the average calculated value: E and standard deviation: σ calculated by the load calculation unit 51, i.e., MV = (1/2) x (h(E - σ) + h(E + σ)). This equation also uses the operating merit function, so the two lookup tables above can be constructed in an integrated manner.

The output data processing unit 56 transmits control signals for controlling various operating devices in a fuel cell system such as that shown in FIG. 1 based on commands from the operation control unit 54. The operating devices to be controlled include fuel cell operating device D1 for operating the solid oxide fuel cell 1, power system operating device D2 for supplying power to the power load unit 3, and hot water system operating device D3 for supplying hot water to the heat load unit 4 such as a water heater. Furthermore, the output data processing unit 56 transmits an alarm signal to an alarm device 60 incorporated in the remote control LC. The alarm device 60 includes a display 61 such as an LCD, a buzzer 62, and a lamp 63, and the alarm data is generated by the alarm processing unit 58. Although not shown, a similar alarm device 60 may be installed in a location separate from the remote control LC.

The input data processing unit 57 processes the power load measurement values sent from the power load measuring means 16 and the thermal load measurement values sent from the thermal load measuring means 17, and provides the processed signals to the load calculation unit 51. Furthermore, the input data processing unit 57 is also connected to the remote control LC, and processes operation signals sent via the touch panel 64 of the remote control, and provides these to the operation control unit 54, etc., enabling manual management and control of the fuel cell system.

The management center (management computer) 200 is configured with an operating merit function management unit 201 and a fuel cell operation information management unit 202. The management center 200 modifies the operating merit function based on fluctuations in various costs, etc. The operating merit function management unit 201 accesses the operation control device 100 in each user's home based on such modifications to the operating merit function and updates the lookup table stored in the operating merit function storage unit 55. The fuel cell operation information management unit 202 records and manages the operating status (operating specifications, operating conditions, operating history, etc.) of the fuel cell system in each user's home.

Second Embodiment
The fuel cell system of the second embodiment differs from the above-described embodiments in the method of determining whether to operate or stop the operation. The fuel cell system of the second embodiment will be described below, but a description of the same configuration as the above-described embodiments will be omitted.

Figure 9 is a flowchart explaining the determination made by the operation determination unit 53 as to whether to operate or stop the solid oxide fuel cell 1. Figure 9 is the flowchart explained in Figure 5 of the first embodiment, to which step #15 has been added.

In step #15, the operation determination unit 53 performs a cost verification process to determine whether the first operating cost of continuing to operate the solid oxide fuel cell 1 is greater than the second operating cost of starting up the solid oxide fuel cell 1 after stopping its operation. Specifically, the operation determination unit 53 performs a cost verification process to verify the first operating cost required to continue operating the solid oxide fuel cell 1 until the predicted power outage date and time within the power outage determination period when there is a high possibility of a power outage occurring during the power outage determination period, and the second operating cost required to complete start-up of the solid oxide fuel cell 1 at the predicted power outage date and time after stopping the operation of the solid oxide fuel cell 1.

The calculation of the first operating cost and the second operating cost will be described assuming, for example, that all of the load power of the power load unit 3 is covered by the power generated by the solid oxide fuel cell 1, and any surplus power is sold to the commercial power source 15. In this case, the operation determination unit 53 identifies the load power amount of the power load unit 3 during a predetermined past period (e.g., one month) when the solid oxide fuel cell 1 was operating, the amount of power generated during that period, and the amount of power sold to the commercial power source 15 during that period. The operation determination unit 53 then calculates, for that operation period, "gas cost required for operation" - "electricity cost for the amount of power sold" - "electricity cost assuming that (load power amount - amount of power sold) was purchased." In other words, the value (total cost) is calculated by subtracting the profit from selling power and the profit from not purchasing power from the cost required to operate the solid oxide fuel cell 1. The operation determination unit 53 calculates the cost per hour of operation by dividing the calculated total cost by the period (hours) during which operation was performed. Then, the operation determination unit 53 multiplies the calculated cost per hour of operation by the total time from the present time to the predicted power outage date and time, thereby determining the first operating cost required to continue operating the solid oxide fuel cell 1 until the predicted power outage date and time.

The operation determination unit 53 also calculates the sum of the shutdown cost (electricity and gas costs) required to currently shut down the operation of the solid oxide fuel cell 1 and the startup cost (electricity and gas costs) required to complete startup of the solid oxide fuel cell 1 at the predicted power outage date and time after continuing the shutdown, and determines this as the second operating cost.

Then, in step #15, if the first operating cost is greater than the second operating cost, the operation determination unit 53 proceeds to step #17 and outputs a determination result that operation should be stopped to the operation control unit 54. In this case, the operation control unit 54 stops the operation of the solid oxide fuel cell 1, and then completes the start-up of the solid oxide fuel cell 1 by the predicted power outage date and time.
On the other hand, in step #15, if the first operating cost is not greater than the second operating cost, the operation determination unit 53 outputs a determination result that the process should proceed to step #16 and operation should be performed to the operation control unit 54. Then, the operation control unit 54 outputs an operation execution command or an operation stop command to the solid oxide fuel cell 1 based on the determination result of the operation determination unit 53.

Third Embodiment
The fuel cell system of the third embodiment differs from the above-described embodiments in the method of determining whether to operate or stop the operation. The fuel cell system of the third embodiment will be described below, but a description of the same configuration as the above-described embodiments will be omitted.

FIG. 10 is a flowchart illustrating the determination made by the operation determination unit 53 as to whether to operate or stop the solid oxide fuel cell 1 .
In step #20, the operation determination unit 53 determines whether it is the timing for operation determination, that is, whether it is the day to determine whether operation/stop is to be performed. For example, if the timing for this operation determination is set to once a month at the end of the month, the operation determination unit 53 will use the calendar function to determine that the current time is the end of the month (determined as "Yes" in step #20), and will proceed to step #21. On the other hand, if the operation determination unit 53 uses the calendar function to determine that the current time is not the end of the month (determined as "No" in step #20), it will repeat the determination in step #20.

In step #21, the operation determination unit 53 performs a power outage possibility determination process, and if a planned power outage date and time exists within the future power outage determination period, it determines that there is a high possibility of a power outage occurring during that power outage determination period, and if there is no planned power outage date and time within the future power outage determination period, it determines that there is a low possibility of a power outage occurring during that power outage determination period. Then, in step #22, if the operation determination unit 53 determines that there is a high possibility of a power outage occurring, it proceeds to step #25, and if it determines that there is a low possibility of a power outage occurring, it proceeds to step #23.

In step #23, the driving determination unit 53 performs driving feasibility determination processing similar to that described above with reference to Figures 6 and 7.

Next, in step #24, if the result of the provisional determination of the driving feasibility determination process is that driving should be stopped, the driving determination unit 53 proceeds to step #26, and if the result of the provisional determination of the driving feasibility determination process is that driving should be performed, the driving determination unit 53 proceeds to step #25.

In step #25, the operation determination unit 53 outputs a determination result that operation should be performed to the operation control unit 54. In step #26, the operation determination unit 53 outputs a determination result that operation should be stopped to the operation control unit 54. Then, the operation control unit 54 outputs an operation execution command or an operation stop command to the solid oxide fuel cell 1 based on the determination result of the operation determination unit 53.

In this manner, in this embodiment, the operation control unit 54 is configured to issue an operation execution command to the solid oxide fuel cell 1 if the power outage possibility determination process determines that there is a high possibility of a power outage, regardless of the result of the operation feasibility determination process; if the power outage possibility determination process determines that there is a low possibility of a power outage, issue an operation execution command to the solid oxide fuel cell 1 if the operation feasibility determination process provisionally determines that operation should be carried out; and issue an operation stop command to the solid oxide fuel cell 1 if the operation feasibility determination process provisionally determines that operation should be stopped.

<Another embodiment>
<1>
In the above embodiment, a specific example of the configuration of the fuel cell system has been described, but the configuration can be changed as appropriate.

<2>
In the above embodiment, the operation possibility determination process and the power outage possibility determination process have been described using specific examples, but the content of these processes can be changed as appropriate.

<3>
In the above embodiment, the operation feasibility determination process and power outage possibility determination process were explained, focusing mainly on the power load of the power load section 3 as the energy load section L, but the operation feasibility determination process and power outage possibility determination process may also take into account the thermal load of the thermal load section 4 as the energy load section L.

＜4＞
In the second embodiment described above, the operation determination unit 53 outputs a determination result indicating that operation should be stopped if the first operating cost is greater than the second operating cost to the operation control unit 54 (steps #15 and #17 in FIG. 9 ), and the operation control unit 54 stops operation of the solid oxide fuel cell 1 and then completes startup of the solid oxide fuel cell 1 by the predicted power outage date and time. However, if the period from the present time to the predicted power outage date and time is short, it may be difficult to stop operation of the solid oxide fuel cell 1 during that time and then complete startup of the solid oxide fuel cell 1 by the predicted power outage date and time. Taking such cases into consideration, even if the operation determination unit 53 determines that the first operating cost is greater than the second operating cost in step #15 of Figure 9 (i.e., even if it is preferable from a cost perspective to stop operation of the solid oxide fuel cell 1), if the period from the present time to the predicted power outage date and time is shorter than the period required to complete startup of the solid oxide fuel cell 1 after stopping the power generation operation of the solid oxide fuel cell 1, it may output a determination result to the operation control unit 54 that the solid oxide fuel cell 1 should be operated (operation should be continued).

<5>
The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope of not departing from the purpose of the present invention.

The present invention can be used in a fuel cell system that can start and stop operation of a solid oxide fuel cell at appropriate times while taking into account future power outages.

1: Solid oxide fuel cell 2: Hot water storage tank 3: Power load section (energy load section L)
4: Heat load section (energy load section L)
16: Power load measuring means (load measuring unit S)
17: Heat load measuring means (load measuring unit S)
51: Load calculation unit 52: Threshold value setting unit 53: Driving determination unit 54: Driving control unit S: Load measurement unit

Claims (6)

A fuel cell system that supplies energy generated from a solid oxide fuel cell that can be selectively controlled to operate or stop operation to an energy load unit,
a load measuring unit that measures load energy required by the energy load unit;
a load calculation unit that calculates an average calculation value of the load measurement values of the load measurement unit measured over a predetermined determination period;
an operation determination unit that outputs a determination result that the solid oxide fuel cell should be operated or stopped based on the result of an operation feasibility determination process that makes a provisional determination that the solid oxide fuel cell should be operated or stopped based on the average calculation value or a substitute value derived from the average calculation value and a determination threshold value, the result of a power outage possibility determination process that determines the degree of possibility of a power outage occurring in a future power outage determination period, and the result of a cost verification process that verifies a first operating cost that will be required to continue operating the solid oxide fuel cell until a predicted power outage date and time within the power outage determination period if a power outage is likely to occur in the power outage determination period, and a second operating cost that will be required to complete start-up of the solid oxide fuel cell at the predicted power outage date and time after the operation of the solid oxide fuel cell is stopped;
a threshold value setting unit that sets the determination threshold value;
an operation control unit that issues an operation execution command or an operation stop command to the solid oxide fuel cell based on the determination result output by the operation determination unit ,
The operation determination unit outputs the determination result that operation of the solid oxide fuel cell should be stopped if the operation feasibility determination process provisionally determines that operation should be stopped, the power outage possibility determination process determines that there is a high possibility of a power outage, and the cost verification process determines that the first operating cost is greater than the second operating cost . The fuel cell system of claim 1, wherein the operation determination unit outputs the determination result that the solid oxide fuel cell should be operated when the operation feasibility determination process provisionally determines that operation should be stopped, the power outage possibility determination process determines that there is a high possibility of a power outage, and the cost verification process determines that the first operating cost is not greater than the second operating cost. 3. The fuel cell system according to claim 1, wherein the operation control unit outputs the determination result that the solid oxide fuel cell should be operated when it is provisionally determined in the operation feasibility determination process that operation should be performed. The fuel cell system according to any one of claims 1 to 3, wherein the operation control unit outputs the determination result that the operation of the solid oxide fuel cell should be stopped when the operation feasibility determination process provisionally determines that operation should be stopped and the power outage possibility determination process determines that the possibility of a power outage is low. The fuel cell system according to any one of claims 1 to 4, wherein the alternative value is a function value of an operating merit function that derives the operating merit of the solid oxide fuel cell from the average calculated value, and the threshold setting unit sets a judgment threshold converted into the operating merit as a merit judgment threshold. 6. The fuel cell system according to claim 5 , wherein the operational benefit is a reduction in primary energy consumption, a reduction in energy costs, or a reduction in carbon dioxide emissions obtained by operating the solid oxide fuel cell, or a combination thereof.