JP7369949B2 - cogeneration system - Google Patents

Description

The present disclosure relates to a cogeneration system.

BACKGROUND ART Cogeneration systems that include a hot water storage unit that stores hot water obtained by recovering exhaust heat from fuel cells have been known.

For example, Patent Document 1 describes a cogeneration system including a power generation unit, a hot water storage unit, a heater, and a control means. The power generation unit is a fuel cell unit and generates electricity and heat. The hot water storage unit stores hot water heated by the heat generated by the power generation unit. The heater increases the temperature of hot water stored in the hot water storage unit. The control means controls the heater based on a predicted value of the amount of heat stored in the hot water storage unit. The hot water storage unit has a backup boiler. The backup boiler has a burner that burns raw fuel, and heats the hot water when the temperature of the hot water does not reach a desired temperature.

Japanese Patent Application Publication No. 2012-207829

The technique described in Patent Document 1 has room for reexamination from the viewpoint of reducing energy consumption. Therefore, the present disclosure provides a cogeneration system that is advantageous from the viewpoint of reducing energy consumption.

The cogeneration system in this disclosure includes:
a fuel cell unit that generates electricity and heat;
a hot water storage unit that stores hot water heated by the heat generated by the fuel cell unit;
a control unit that causes the fuel cell unit to follow a load by operating the fuel cell unit according to at least a first control;
a first heater that heats water stored in the hot water storage unit using electric power;
A storage unit that stores historical data indicating past power loads and past heat loads;
The control unit predicts power demand and heat demand for a predetermined period in the future based on the historical data, and controls the hot water storage unit when a heat shortage state requiring heat generation from the first heater is predicted to occur. Calculating the insufficient amount of heat in the hot water storage unit based on the amount of stored hot water and the heat demand;
The control unit controls at least an amount of power generation and a power generation time of the fuel cell unit based on a first amount of heat generated in the fuel cell unit when the fuel cell unit is operated according to the first control and the amount of heat that is insufficient. The fuel cell unit is operated according to a second control in which the first control is increased by one.

The above cogeneration system is advantageous from the viewpoint of reducing energy consumption.

Configuration diagram of cogeneration system in Embodiment 1 Flowchart showing an example of control of a cogeneration system Flowchart showing an example of control of a cogeneration system Flowchart showing an example of control of a cogeneration system

(Findings that formed the basis of this disclosure)
At the time when the present inventors came up with the present disclosure, there was a system as a cogeneration system that was equipped with a hot water storage unit that stored hot water from which exhaust heat from a fuel cell was recovered. In such a system, the hot water storage unit has a backup boiler, and the temperature of the hot water being tapped is adjusted to a desired temperature using the backup boiler. In such a cogeneration system, when controlling the fuel cell to generate electricity so as to follow the load, there is a possibility that the hot water obtained by recovering the exhaust heat of the fuel cell will be insufficient to meet the demand for hot water supply. In this case, it is necessary to use a backup boiler to heat the hot water discharged from the hot water storage unit.

The use of a backup boiler cannot be said to be advantageous from the viewpoint of reducing the manufacturing cost of a cogeneration system. Therefore, when operating the fuel cell unit to follow the load, the water previously stored in the hot water storage unit is heated using an electric heater, taking into consideration the predicted hot water demand. It is conceivable to store an amount of hot water.

On the other hand, the present inventor discovered the problem that there is room to reduce energy consumption when a cogeneration system is equipped with such a heater, and in order to solve the problem, the subject of the present disclosure is configured. I ended up doing it.

Therefore, the present disclosure provides a cogeneration system that is advantageous from the viewpoint of reducing energy consumption.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

(Embodiment 1)
Embodiment 1 will be described below with reference to FIGS. 1, 2, 3, and 4.

[1-1. composition]
As shown in FIG. 1, the cogeneration system 1 includes a fuel cell unit 10, a hot water storage unit 20, a control section 30, a first heater 40, and a storage section 35. Fuel cell unit 10 generates electricity and heat. In the fuel cell unit 10, electric power and heat are generated by a reaction between a fuel gas such as hydrogen and an oxidizing agent such as air. The fuel cell for this reaction is, for example, a polymer electrolyte fuel cell, a solid oxide fuel cell, or a phosphoric acid fuel cell. The hot water storage unit 20 stores hot water heated by the heat generated by the fuel cell unit 10. As shown in FIG. 1, the cogeneration system 1 includes, for example, a water circuit 15 and a heat exchanger 15a. The water circuit 15 connects the fuel cell unit 10 and the hot water storage unit 20. Water circulates between the fuel cell unit 10 and the hot water storage unit 20 through the water circuit 15 . The heat exchanger 15a is disposed inside the fuel cell unit 10, and heats water passing through the water circuit 15 using heat generated in the fuel cell unit 10. The heat exchanger 15a is configured to, for example, exchange heat between a heat medium heated by heat generated in the fuel cell unit 10 and water in the water circuit 15.

The control unit 30 causes the fuel cell unit 10 to follow the load by operating the fuel cell unit 10 according to at least the first control. The control unit 30 is typically a microcomputer that can execute a program for operating the fuel cell unit 10. The control section 30 is arranged in the fuel cell unit 10, for example.

The first heater 40 heats the water stored in the hot water storage unit 20 using electric power. The first heater 40 is, for example, a resistance heating electric heater. The first heater 40 is arranged, for example, in the hot water storage unit 20.

As shown in FIG. 1, the hot water storage unit 20 includes, for example, a tank 21, a circulation path 22, and a plurality of temperature sensors 24. The tank 21 stores hot water. The circulation path 22 circulates hot water between the inside of the tank 21 and the outside of the tank 21 . The first heater 40 heats water in the circulation path 22, for example. For example, both ends of the circulation path 22 are connected to the tank 21. For example, one end of the circulation path 22 is connected to the vicinity of the bottom of the tank 21, and the other end of the circulation path 22 is connected to the tank 21 above the one end of the circulation path 22. For example, water inside the tank 21 is extracted from one end of the circulation path 22, and water heated by the first heater 40 is returned to the tank 21 from the other end of the circulation path 22. A supply path for supplying city water to the tank 21 may be connected to the bottom of the tank 21 .

The plurality of temperature sensors 24 are arranged at different heights inside the tank 21, for example. Each temperature sensor 24 includes, for example, a thermocouple or a thermistor. The control unit 30 is communicably connected to each temperature sensor 24 so that data indicating the detection results of each temperature sensor 24 can be acquired.

The storage unit 35 stores historical data. The historical data is data indicating past power loads and past heat loads. The storage unit 35 is, for example, a nonvolatile memory. The control unit 30 is communicably connected to the storage unit 35 so that history data can be acquired from the storage unit 35.

The fuel cell unit 10 further includes, for example, a second heater 12. The second heater 12 uses electric power to heat a heat medium that recovers heat generated by the fuel cell unit 10. The second heater 12 heats water in the water circuit 15, for example. The second heater 12 is, for example, a resistance heating electric heater. The second heater 12 may be supplied with electric power generated by the fuel cell unit 10 .

As shown in FIG. 1, the cogeneration system 1 further includes, for example, a power measurement unit 32. The power measurement unit 32 measures, for example, power consumption in a home or facility to which the cogeneration system 1 supplies power. The control unit 30 is communicably connected to the power measurement unit 32 so that data indicating measurement results can be acquired from the power measurement unit 32.

[1-2. motion]
The operation of the cogeneration system 1 configured as described above will be explained with reference to FIGS. 2, 3, and 4. The cogeneration system 1 is operated according to the process shown in FIG. 2, for example.

In step S101, the control unit 30 acquires history data of power load and heat load. Next, in step S102, the control unit 30 predicts power demand and heat demand for a predetermined period in the future based on the acquired history data. Next, in step S103, the control unit 30 calculates a time period in which the first heater 40 generates heat. Next, in step S104, the control unit 30 determines whether there is a time period in which the first heater 40 generates heat. If the determination result in step S104 is negative, the process proceeds to step S105, and the control unit 30 operates the fuel cell unit 10 according to the first control. Thereby, the fuel cell unit 10 is operated to follow the load. The future predetermined period in the prediction of electric power demand and heat demand is, for example, the scheduled start time of the fuel cell unit 10 in the power generation plan for the first control, and the scheduled end time of the fuel cell unit 10 in the power generation plan. including the period between. In two consecutive power generation plans, the future predetermined period in predicting power demand and heat demand is the scheduled start time of the preceding power generation plan and the scheduled start time of the subsequent power generation plan or the end of operation of the subsequent power generation plan. It may be a period between the scheduled time and the scheduled time.

If the determination result in step S104 is affirmative, the control unit 30 proceeds to step S106 and calculates the amount of heat insufficient in the hot water storage unit 20. Next, in step S107, the control unit 30 calculates necessary power generation parameters from the insufficient amount of heat in the hot water storage unit 20 and the time until the first heater 40 generates heat. The power generation parameters include, for example, the power generation amount and power generation time of the fuel cell unit 10. According to this power generation parameter, the second control is realized in which at least one of the power generation amount and the power generation time of the fuel cell unit is increased compared to the first control.

Next, the control unit 30 proceeds to step S108 and operates the fuel cell unit 10 according to the second control. Thereafter, the process proceeds to step S109, and the control unit 30 determines whether there is a time period in which the first heater 40 generates heat. If the determination result in step S109 is negative, the series of processing ends.

If the determination result in step S109 is affirmative, then the control unit 30 proceeds to step S110. In step S110, the control unit 30 determines whether the amount of hot water stored in the hot water storage unit 20 after operating the fuel cell unit 10 according to the second control is insufficient for the heat demand. If the determination result in step S110 is affirmative, the process proceeds to step S111, where the first heater 40 generates heat, and the series of processes ends. On the other hand, if the determination result in step S109 is negative, the series of processes is ended without causing the first heater 40 to generate heat.

"Calculation of the time period in which the first heater 40 generates heat" and "calculation of insufficient heat amount" in steps S103 to S106 are performed, for example, according to the process shown in FIG. 3.

As shown in FIG. 3, the control unit 30 acquires the predicted value of heat demand based on historical data and the current amount H1 of hot water stored in the hot water storage unit 20 in step S201. The hot water amount H1 can be determined, for example, based on data indicating detection results from the plurality of temperature sensors 24.

For example, water is stored inside the tank 21 so as to form a temperature stratification, and hot water tends to exist in the upper part of the tank 21. On the other hand, low-temperature water such as city water is supplied from the bottom of the tank 21, for example. The larger the number of temperature sensors 24 that detect a temperature equal to or higher than a specific temperature, the higher the hot water amount H1 is determined. Further, the higher the temperature detected by the plurality of temperature sensors 24, the higher the hot water amount H1 can be determined. In this way, the amount H1 of hot water may be a physical amount corresponding to the amount of heat of the hot water stored inside the tank 21.

Next, the control unit 30 sets the search target time n to the current time in step S202. Next, the control unit 30 proceeds to step S203 and calculates an integrated value A of predicted values of heat demand from the current time to the search target time n. Next, the control unit 30 proceeds to step S204, and calculates the amount B of hot water stored in the hot water storage unit 20 at the search target time n by subtracting the integrated value A from the current amount H1 of hot water. Next, the control unit 30 proceeds to step S205 and determines whether the hot water amount B is less than the threshold value Lt. Note that when the amount of hot water stored in the hot water storage unit 20 becomes less than the threshold value Lt, the first heater 40 generates heat to heat the water, and a predetermined amount of hot water is stored in the hot water storage unit 20.

If the determination result in step S205 is negative, the process advances to step S206, and it is determined whether the search target time n is equal to or greater than the scheduled search time N. In other words, it is determined whether the search target time n is the same as the search scheduled time N and whether the search target time n has passed the search scheduled time N. If the determination result in step S206 is negative, the process proceeds to step S207, where the control unit 30 increments the search target time n by a predetermined time, and returns to step S203. Thereafter, the processes from steps S203 to S207 are repeated until the determination result in step S205 becomes affirmative or until the determination result in step S206 becomes affirmative.

If the determination result in step S205 is affirmative, the control unit 30 proceeds to step S208 and sets the search target time n to the time when the first heater 40 generates heat. Next, the control unit 30 proceeds to step S209 and calculates the insufficient amount of heat c. After that, the process moves to step S107. The insufficient amount of heat c corresponds to the amount of hot water that is insufficient in the hot water storage unit 20 relative to the heat demand. For example, when the hot water amount B is a negative value, the insufficient heat amount c corresponds to the value obtained by adding the threshold Lt to the absolute value of the hot water amount B.

If the determination result in step S206 is affirmative, it is determined that there is no time period in which the first heater 40 generates heat and that there is no insufficient amount of heat, and the process moves to step S107.

The "calculation of power generation parameters" in step S107 is performed, for example, according to the process shown in FIG. 4.

As shown in FIG. 4, in step 301, the control unit 30 acquires the time a when the first heater 40 generates heat, the predicted value b of the power demand, and the insufficient amount of heat c. The time a and the insufficient amount of heat c are the values calculated in steps S201 to S210, and the predicted value b is the value predicted in step S102.

Next, the control unit 30 proceeds to step S302 and sets the start target time d to the difference (at) obtained by subtracting the predetermined time t from the time a. In addition, the control unit 30 sets the power generation increase amount α to zero.

Next, the control unit 30 calculates the total amount of heat e generated by the power generation in the fuel cell unit 10 from time d to time a. In this calculation, b+α is used as the value of the amount of power generation. Note that the value of α is adjusted so that b+α is equal to or less than the maximum power generation amount. In the first control, the fuel cell unit 10 generates power according to the predicted value b.

Next, the process proceeds to step S304, and the control unit 30 determines whether the insufficient amount of heat c is smaller than the total amount of heat e. If the determination result in step S304 is negative, the process advances to step S305, and the control unit 30 determines whether the increased amount α of power generation is the upper limit value. If the determination result in step S305 is negative, the control unit 30 increments the power generation increase amount α in step S306, and returns to step S303.

If the determination result in step S305 is affirmative, the process proceeds to step S307, and the control unit 30 determines whether or not the start target time d is the current time. If this determination result is negative, the control unit 30 proceeds to step S308, decrements the start target time d by a predetermined time t, changes the power generation increase amount α to 0, and proceeds to step S303.

The processes from step S303 to step S308 are repeated until the determination result in step S304 becomes affirmative or until the determination result in step S307 becomes affirmative.

If the determination result in step S304 is positive, or if the determination result in step S307 is positive, the control unit 30 proceeds to step S309. In step S309, the control unit 30 sets the power generation time period from time d to time a, and determines the power generation increase amount α. After that, the control unit 30 moves to step S108 and operates the fuel cell unit 10 according to the second control defined by the power generation time period from time d to time a and the power generation increase amount α.

[1-3. Effects, etc.]
As described above, in this embodiment, the cogeneration system 1 includes the fuel cell unit 10, the hot water storage unit 20, the control section 30, the first heater 40, and the storage section 35. Fuel cell unit 10 generates electricity and heat. The hot water storage unit 20 stores hot water heated by the heat generated by the fuel cell unit 10. The control unit 30 causes the fuel cell unit 10 to follow the load by operating the fuel cell unit 10 according to at least the first control (see step S105). The first heater 40 heats the water stored in the hot water storage unit 20 using electric power. The storage unit 35 stores history data indicating past power loads and past heat loads. In addition, the control unit 30 predicts power demand and heat demand for a predetermined period in the future based on historical data (see step S102). When a heat shortage state requiring heat generation from the first heater 40 is predicted to occur, the control unit 30 determines the insufficient amount of heat in the hot water storage unit 20 based on the amount of hot water stored in the hot water storage unit 20 and the heat demand. is calculated (see step S105 and FIG. 3). In this case, the control unit 30 operates the fuel cell unit 10 according to the second control (see step S108). In the second control, at least one of the power generation amount and power generation time of the fuel cell unit 10 is increased relative to the first control based on the first heat amount and the insufficient heat amount (see step S107 and FIG. 4). The first amount of heat is the amount of heat generated in the fuel cell unit 10 when the fuel cell unit 10 is operated according to the first control.

As a result, at least one of the power generation amount and the power generation time of the fuel cell unit 10 increases with respect to the control that causes the fuel cell unit 10 to follow the load, so that the amount of heat generated by the first heater 40 can be reduced. Therefore, the cogeneration system 1 is advantageous from the viewpoint of reducing energy consumption.

As in the present embodiment, the control unit 30 may determine whether or not the first heater 40 needs to generate heat after operating the fuel cell unit 10 according to the second control (see step S109).

This allows the first heater 40 to generate heat only when necessary after the fuel cell unit 10 is operated according to the second control. Therefore, the cogeneration system 1 is more advantageous from the viewpoint of reducing energy consumption.

As in the present embodiment, when the amount of hot water stored in the hot water storage unit 20 after operating the fuel cell unit 10 according to the second control is insufficient for the heat demand, the control unit 30 causes the first heater 40 to generate heat. You may let them. On the other hand, the control unit 30 does not need to cause the first heater 40 to generate heat when the amount of hot water stored in the hot water storage unit 20 after operating the fuel cell unit 10 according to the second control is sufficient for the heat demand. These processes are performed based on the amount of hot water stored in the hot water storage unit 20, the second amount of heat generated in the fuel cell unit 10 when the fuel cell unit 10 is operated according to the second control, and the heat demand. (See step S110).

As a result, the first heater 40 does not generate heat when the hot water stored in the hot water storage unit 20 is sufficient for the heat demand after operating the fuel cell unit 10 according to the second control. For example, after operating the fuel cell unit 10 according to the second control, if there is no or little demand for heat such as hot water supply and space heating, even if the amount of hot water stored in the hot water storage unit 20 is less than the threshold value Lt, the first control The heater does not generate heat. Therefore, the amount of heat generated by the first heater 40 can be reduced, and the cogeneration system 1 is more advantageous from the viewpoint of reducing energy consumption.

As in this embodiment, the fuel cell unit 10 may include a second heater 12 that uses electric power to heat a heat medium that recovers heat generated in the fuel cell unit 10. In this case, the first amount of heat generated by the fuel cell unit 10 when the fuel cell unit 10 is operated according to the first control may include the amount of heat generated by the second heater 12.

As a result, the heat medium can be heated to a desired temperature by the second heater 12, and the first heat amount generated in the fuel cell unit 10 when operating according to the first control is taken into account in consideration of the heat amount generated by the second heater 12. You can decide. Therefore, details of the second control can be appropriately determined.

As in this embodiment, the fuel cell unit 10 may include a second heater 12 that uses electric power to heat a heat medium that recovers heat generated in the fuel cell unit 10. In this case, the second amount of heat generated by the fuel cell unit 10 when the fuel cell unit 10 is operated according to the second control may include the amount of heat generated by the second heater 12.

As a result, the heat medium can be heated to a desired temperature by the second heater 12, and the second heat amount generated in the fuel cell unit 10 when operating according to the second control is taken into consideration. You can decide. Therefore, it can be appropriately determined whether the amount of hot water stored in the hot water storage unit 20 after operating the fuel cell unit 10 according to the second control is insufficient for the heat demand.

As in this embodiment, the hot water storage unit 20 may include a tank 21 that stores hot water, and a circulation path 22 that circulates water between the inside of the tank 21 and the outside of the tank 21. The first heater 40 may heat the water in the circulation path 22 .

Thereby, the first heater 40 heats the water in the circulation path 22, and the heated water is returned to the tank 21 through the circulation path 22. Thereby, the state of hot water in the hot water storage unit 20 can be quickly brought close to a desired state without disturbing temperature stratification.

(Other embodiments)
In the first embodiment, an example has been described in which the control section 30 is arranged inside the fuel cell unit 10. However, the control section 30 may be placed outside the fuel cell unit 10.

In the first embodiment, an example has been described in which the heat exchanger 15a is a heat exchanger that exchanges heat between the heat medium heated by the heat generated in the fuel cell unit 10 and the water in the water circuit 15. However, the heat exchanger 15a may be placed in contact with a heat source of heat generated by the fuel cell unit 10, for example. An example of a heat source is a fuel cell.

In the first embodiment, an example has been described in which the second heater 12 is a heater that heats water in the water circuit 15. However, the object to be heated by the second heater 12 may be other than water in the water circuit 15. For example, the second heater 12 may exchange heat with water in the water circuit 15 in the heat exchanger 15a and heat a heat medium heated by heat generated in the fuel cell unit 10.

In the first embodiment, the power generation parameters are calculated such that the start target time d is kept constant until the power generation increase amount α reaches the upper limit value. However, the power generation parameters may be calculated so that the start target time d is brought forward before the power generation increase amount α reaches the upper limit value.

Note that the above-described embodiments are for illustrating the technology of the present disclosure, and therefore various changes, substitutions, additions, omissions, etc. can be made within the scope of the claims or equivalents thereof.

The present disclosure can be applied to a cogeneration system that stores hot water obtained by recovering exhaust heat from fuel cells.

1 Cogeneration system 10 Fuel cell unit 12 Second heater 20 Hot water storage unit 21 Tank 22 Circulation path 30 Control section 35 Storage section 40 First heater

Claims (6)

a fuel cell unit that generates electricity and heat;
a hot water storage unit that stores hot water heated by the heat generated by the fuel cell unit;
a control unit that causes the fuel cell unit to follow a load by operating the fuel cell unit according to at least a first control;
a first heater that heats water stored in the hot water storage unit using electric power generated from a source other than the fuel cell unit ;
a second heater to which electric power generated by the fuel cell unit is supplied;
A storage unit that stores historical data indicating past power loads and past heat loads;
The control unit predicts power demand and heat demand for a predetermined period in the future based on the historical data, and controls the hot water storage unit when a heat shortage state requiring heat generation from the first heater is predicted to occur. Calculating the insufficient amount of heat in the hot water storage unit based on the amount of stored hot water and the heat demand;
The control unit controls at least an amount of power generation and a power generation time of the fuel cell unit based on a first amount of heat generated in the fuel cell unit when the fuel cell unit is operated according to the first control and the amount of heat that is insufficient. operating the fuel cell unit according to a second control in which one is increased relative to the first control;
cogeneration system. The cogeneration system according to claim 1, wherein the control unit determines whether heat generation by the first heater is necessary after operating the fuel cell unit according to the second control. The control unit is configured to control the amount of hot water according to the second control based on the amount of hot water, a second amount of heat generated in the fuel cell unit when the fuel cell unit is operated according to the second control, and the heat demand. causing the first heater to generate heat when the amount of hot water stored in the hot water storage unit after operating the fuel cell unit is insufficient for the heat demand;
The control unit is configured to control the amount of hot water according to the second control based on the amount of hot water, a second amount of heat generated in the fuel cell unit when the fuel cell unit is operated according to the second control, and the heat demand. not causing the first heater to generate heat when the amount of hot water stored in the hot water storage unit after operating the fuel cell unit is sufficient for the heat demand;
The cogeneration system according to claim 1 or 2. The second heater heats a heat medium that recovers heat generated by the fuel cell unit using electric power generated by the fuel cell unit ,
The first amount of heat includes the amount of heat generated by the second heater.
A cogeneration system according to any one of claims 1 to 3. The second heater heats a heat medium that recovers heat generated by the fuel cell unit using electric power generated by the fuel cell unit ,
The second amount of heat includes the amount of heat generated by the second heater.
The cogeneration system according to claim 3. The hot water storage unit has a tank that stores hot water, and a circulation path that circulates water between the inside of the tank and the outside of the tank,
the first heater heats water in the circulation path;
A cogeneration system according to any one of claims 1 to 5.

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