JP6963749B2 - Hot water storage system - Google Patents

Description

The present invention relates to a hot water storage hot water supply system equipped with a heat pump type heat source machine and a combustion type heat source machine so that the generated power of a solar power generation device can be used, and is particularly based on the future hot water supply use predicted based on the hot water supply usage history. Regarding the hot water storage system that stores hot water.

Conventionally, hot water storage devices equipped with a heat pump type heat source machine for preheating hot water for hot water supply and bathtub filling and storing it in a hot water storage tank, and a combustion type heat source machine for heating hot water when using hot water supply etc. Widely used. Such a hot water storage water heater usually has a higher operating efficiency of the heat pump type heat source machine than the operating efficiency of the combustion type heat source machine. It is configured to use the hot water stored in the hot water storage tank for hot water supply, etc. by the hot water storage operation of the heat pump type heat source machine based on the above.

On the other hand, in a household equipped with a photovoltaic power generation device, the generated power is supplied to the household, and when the generated power exceeds the power used in the household and there is surplus power, the power is sold. When there is surplus electric power that can be sold, for example, as in Patent Document 1, a hot water supply system is known in which a heat pump type heat source machine is driven by the surplus electric power to perform a hot water storage operation.

Japanese Unexamined Patent Publication No. 2017-36842

However, in Patent Document 1, since the hot water storage operation is performed when there is surplus electric power, the stored hot water is stored for a long time until the hot water is used, and the temperature drops due to heat dissipation, so that the hot water cannot be used for hot water supply and may be wasted. In addition, the generated power of the photovoltaic power generation device fluctuates depending on the time of day and the weather, and the surplus power is not stable because the power is used at home. Therefore, the heat pump type heat source machine may be repeatedly driven and stopped due to the fluctuation of the surplus electric power, and the operation efficiency may be deteriorated due to the start loss of the heat pump type heat source machine.

An object of the present invention is that when the hot water storage operation is performed using the surplus electric power of the photovoltaic power generation device, the stored hot water can be stored so as not to be wasted, and the deterioration of the operating efficiency of the heat pump type heat source machine is suppressed. It is to provide a hot water storage and hot water supply system that is possible.

The invention of claim 1 uses a heat pump type heat source machine, a combustion type heat source machine, a hot water storage tank for storing hot water heated by the hot water storage operation of the heat pump type heat source machine, and hot water supply using a required amount of heat based on a hot water supply usage prediction. In a hot water storage system equipped with a control means for controlling the hot water storage operation so as to store the hot water in the hot water storage tank by a time and a solar power generation device, the hot water storage operation is executed using the generated power of the solar power generation device. The control means uses the surplus power when the generated power has surplus power that can be sold and the time from the current time to the hot water supply use time is equal to or less than the first predetermined time. It is characterized in that the advance hot water storage operation is executed, in which the hot water storage operation is started before the hot water storage operation start time set based on the hot water supply usage prediction.

According to the above configuration, the predicted amount of heat required for hot water supply is stored in the hot water storage tank by hot water storage operation, and if there is surplus power generated by the photovoltaic power generation device, the surplus power is used for hot water storage operation. Can be done. In the case of hot water storage operation that uses surplus electricity, the hot water storage operation is performed when the time from the current time to the predicted hot water supply usage time is less than the first predetermined time, so the storage time in the hot water storage tank is shortened and the temperature of the hot water due to heat dissipation. By reducing the decrease, it is possible to maintain hot water supply, and the stored hot water is not wasted.

The invention of claim 2 is the invention of claim 1, wherein when the surplus electric power is exhausted during the execution of the advanced hot water storage operation, the hot water storage completion time and the sun when the advanced hot water storage operation is continued. Compared with the power generation end set time of the photovoltaic power generation device, the advanced hot water storage operation is continued when the same time or the hot water storage completion time is earlier, and the advanced hot water storage operation is performed when the hot water storage completion time is later. It is characterized by stopping.

According to the above configuration, if the surplus power is exhausted due to the weather or the like during the advance hot water storage operation, if the hot water storage operation is continued with the commercial power supplied from the commercial power source, the power generation differs depending on the installation environment of the solar power generation device. When the hot water storage is completed by the power generation end set time for which the power generation end time is set for a possible time, the hot water storage operation is continued. If there is surplus power again while the hot water storage operation is continuing, the surplus power can be used for hot water storage operation, and the hot water storage operation is avoided intermittently to prevent deterioration of the operating efficiency of the heat pump type heat source machine. be able to. If the hot water storage is not completed by the power generation end set time, the advanced hot water storage operation is stopped. As a result, it is possible to prevent the temperature of the hot water stored in the hot water storage operation using commercial power from dropping due to heat dissipation until the hot water is used.

The invention of claim 3 is the invention of claim 2, wherein when the advance hot water storage operation is stopped, the hot water storage operation is performed in order to store the unstored heat amount of the required heat amount by the hot water supply use time. When the time difference between the time when the operation is started and the time when the surplus power is exhausted is equal to or less than the second predetermined time, the advanced hot water storage operation is not stopped.

According to the above configuration, when the advanced hot water storage operation is not completed by the power generation end set time, the time difference from the time when the surplus power is exhausted to the start time of the hot water storage operation for storing the unstored heat of the required heat is the second. If it is less than the specified time, the advanced hot water storage operation is not stopped. This makes it possible to prevent deterioration of operating efficiency due to start-up loss of the heat pump type heat source machine.

According to the hot water storage and hot water supply system of the present invention, when the hot water storage operation is performed using the surplus electric power of the photovoltaic power generation device, the hot water can be stored so that the stored hot water is not wasted, and the operation efficiency of the heat pump type heat source machine is increased. It is possible to suppress the deterioration of.

It is a figure which shows the whole structure of the hot water storage system which concerns on embodiment of this invention. It is a figure which shows the configuration example of a heat pump type heat source machine and a hot water storage hot water supply unit. It is a flowchart of hot water storage operation using surplus electric power. It is a time chart which shows the 1st example of the hot water storage operation using surplus electric power. It is a time chart which shows the 2nd example of the hot water storage operation using surplus electric power. It is a time chart which shows the 3rd example of the hot water storage operation using surplus electric power. It is a time chart which shows the 4th example of the hot water storage operation using surplus electric power.

Hereinafter, embodiments for carrying out the present invention will be described based on examples.

First, the overall configuration of the hot water storage and hot water supply system 1 of the present invention will be described with reference to FIGS. 1 and 2.
The hot water storage and hot water supply system 1 includes a heat pump type heat source machine 2, a hot water storage and hot water supply unit 3, and a solar power generation device 4. The hot water storage and hot water supply unit 3 uses the hot water storage tank 11 for storing the hot water heated by the hot water storage operation of the heat pump type heat source machine 2, the combustion type heat source machine 12, and the required hot water storage heat amount (required heat amount) based on the hot water supply usage prediction. It is provided with a control unit 13 (control means) that controls the hot water storage operation so that the hot water is stored in the hot water storage tank 11 by the time. The heat pump type heat source machine 2 absorbs heat from the outside air to heat hot water based on a command from the control unit 13 for hot water storage operation, and stores the heated hot water in the hot water storage tank 11.

The solar power generation device 4 is connected to a junction box 6 for collecting the DC power generated by the solar panel 5 generated by sunlight, and to convert the DC power from the junction box 6 into AC power (generated power). It is composed of a power conditioner 7 connected to the power conditioner 7 and a distribution board 8 connected so that the electric power generated from the power conditioner 7 can be distributed to the places of use in the home. The distribution board 8 also distributes AC power (commercial power) from the commercial power supply line 9 to the places used in the home. The generated power supplied from the power conditioner 7 is distributed to the home, and the surplus power is sent from the distribution board 8 to the outside via the commercial power supply line 9 for sale.

A part of the electric power distributed from the distribution board 8 is supplied to the hot water storage hot water supply unit 3 via the power supply line 3a, and the electric power for driving is supplied from the hot water storage hot water supply unit 3 to the heat pump type heat source machine 2 via the power supply line 2a. Will be done. The heat pump type heat source machine 2 and the hot water storage hot water supply unit 3 can be driven by using the generated power and the commercial power distributed from the distribution board 8 independently or in combination with each other.

The hot water storage unit 3 uses the hot water stored in the hot water storage tank 11 heated by the heat pump type heat source machine 2 for hot water supply and filling of the bathtub 29. Further, in the case of high-temperature hot water supply in which the hot water of the hot water storage tank 11 cannot be supplied or the reheating operation of the bathtub 29, the hot water heated by burning the fuel in the combustion type heat source machine 12 is used for the hot water supply or the reheating operation.

A hot water discharge passage 14 for discharging hot water stored in the hot water storage tank 11 is connected to the upper part of the hot water storage tank 11. The hot water outlet passage 14 is connected to the hot water mixing valve 15, and a hot water temperature sensor 14a for detecting the hot water temperature of the hot water supplied to the hot water mixing valve 15 is provided. Further, at the lower part of the hot water storage tank 11, a water supply passage 16 for supplying clean water from a clean water source is connected to the hot water storage tank 11. A water supply temperature sensor 16a for detecting the water supply temperature of the clean water supplied from the water supply source is provided in the water supply passage 16.

The hot and cold water mixing valve 15 can mix the hot water of the hot water outlet passage 14 and the clean water of the bypass passage 17 which is branched from the hot water supply passage 16 and is connected so as to be able to supply clean water to the hot water mixing valve 15, and the mixing ratio thereof can be adjusted. Is. A hot water supply passage 18 is connected to the hot water mixing valve 15, and the hot water mixed by the hot water mixing valve 15 flows through the hot water supply passage 18 and is supplied to a hot water tap or the like (not shown). Further, the hot water mixed by the hot water mixing valve 15 can be filled in the bathtub 29 via the hot water filling passage 19 that branches from the hot water supply passage 18 and is connected to the reheating circuit 32. A hot water supply temperature sensor 18a for detecting the hot water supply temperature is provided in the hot water supply passage 18.

An upstream heating passage 21a for supplying hot water to the heat pump type heat source machine 2 is connected to the lower part of the hot water storage tank 11, and a downstream heating passage 21b for supplying hot water heated by the heat pump type heat source machine 2 to the hot water storage tank 11 is a hot water storage tank. A circulation heating circuit 21 is formed which is connected to the upper part of 11 and allows hot water to be circulated by a boiling pump 22 between the hot water storage tank 11 and the heat pump type heat source machine 2. A temperature sensor 23a for detecting the inflow temperature of the heat pump type heat source machine 2 is provided in the upstream heating passage 21a, and a temperature sensor 23b for detecting the hot water discharge temperature of the heat pump type heat source machine 2 is provided in the downstream heating passage 21b. There is.

A plurality of hot water storage temperature sensors 11a to 11d for detecting the temperature of the stored hot water are provided on the outer periphery of the hot water storage tank 11 at predetermined intervals in the vertical direction. The hot water storage temperature sensors 11a to 11d and the hot water storage tank 11 are covered with a heat insulating material (not shown) that reduces heat dissipation from the hot water storage tank 11.

The combustion heating passage 24 for heating the hot water of the hot water storage tank 11 by the combustion type heat source machine 12 is branched from the hot water outlet passage 14 and connected to the combustion type heat source machine 12. The combustion hot water discharge passage 25 for discharging the hot water heated by the combustion type heat source machine 12 is connected to the hot water discharge passage 14 on the downstream side of the branch portion of the combustion heating passage 24 via a regulating valve 26. The adjusting valve 26 adjusts the amount of hot water supplied to the hot water outlet 14 through the combustion hot water passage 25. The combustion heating passage 24 is provided with a three-way valve 27 and a pump 28 for sending hot water to the combustion type heat source machine 12.

The heat exchanger passage 30 branched from the combustion hot water passage 25 is connected to the three-way valve 27. The three-way valve 27 is switched so that the hot water of the hot water storage tank 11 or the hot water of the heat exchanger passage 30 can be supplied to the combustion type heat source machine 12. A heat exchanger 30a and an on-off valve 30b are arranged in the heat exchanger passage 30. Further, a branch passage portion 16b branched from the water supply passage 16 is connected between the on-off valve 30b of the heat exchanger passage 30 and the three-way valve 27. The heat exchanger 30a is used for a reheating operation in which the hot water of the bathtub 29 flowing through the reheating circuit 32 is heated by heat exchange with the hot water heated by the combustion type heat source machine 12 by the operation of the reheating pump 31.

The heat pump type heat source machine 2 includes a heat pump circuit 37 in which a compressor 33, a condensing heat exchanger 34, an expansion valve 35, and an evaporation heat exchanger 36 are connected by a refrigerant pipe. In this heat pump type heat source machine 2, the refrigerant sealed in the refrigerant pipe is compressed by the compressor 33 to raise the temperature, and the boiling pump 22 is driven to drive the hot water flowing through the circulation heating circuit 21 in the condensed heat exchanger 34. It is heated by heat exchange with a high-temperature refrigerant and stored in the hot water storage tank 11. The refrigerant after heat exchange expands with the expansion valve 35 to become lower than the outside air, absorbs heat from the outside air with the evaporation heat exchanger 36, and then is introduced into the compressor 33 again.

The heat of vaporization exchanger 36 includes an outside air temperature sensor 36a for detecting the outside air temperature and a blower 36b. Further, the heat pump type heat source machine 2 includes an auxiliary control unit 38 that controls a compressor 33, an expansion valve 35, a blower 36b, and the like. The auxiliary control unit 38 is communicably connected to the control unit 13 which is the main control means of the hot water storage and hot water supply system 1, and controls the heat pump type heat source machine 2 based on the command of the control unit 13.

The control unit 13 is communicably connected to the distribution board 8 and receives the power generation status and the presence / absence of surplus power that can be sold. The control unit 13 controls the hot water supply operation and the like based on the detection signal of the hot water supply temperature sensor 14a and the like, and also obtains the hot water supply amount and various temperatures in the past hot water supply use, the hot water supply history such as the hot water supply use time, and the power generation status history. I remember learning. Then, based on this hot water supply history, future hot water supply usage prediction is repeated at predetermined time intervals (for example, every 5 minutes), and the solar power generation device 4 that changes depending on the season, installation environment, etc. based on the power generation status history can generate power. Set the start time and end time of the time zone (power generation end setting time te) for each day. In addition, an operation terminal 13a for operations such as setting the hot water supply set temperature by the user is connected to the control unit 13 so as to be able to communicate. The operation terminal 13a is provided with a plurality of switches and the like for various settings, and is configured so that various input settings such as a hot water supply set temperature and a hot water filling time can be set. The power generation end setting time te may be set from the operation terminal 13a.

In the hot water supply usage prediction, the required hot water storage heat amount is calculated based on the predicted hot water supply usage amount, and the hot water storage operation start time t3 is set so that the hot water storage of the required hot water storage heat amount is completed by the predicted hot water supply usage time t4. Further, when there is surplus electric power that can be sold, the control unit 13 starts the hot water storage operation before the set hot water storage operation start time t3 when the hot water storage operation is possible using the surplus electric power. To execute. Then, it is controlled so that the hot water storage of the required hot water storage heat amount is completed by the predicted hot water supply usage time t4. The control of hot water storage by the control unit 13 will be described with reference to the flowchart of FIG. Si (i = 1, 2, ...) In the figure represents a step.

First, in S1, it is determined whether or not there is surplus power. If the determination of S1 is Yes, the process proceeds to S2, and if the determination of S1 is No, the process returns to S1. Next, in S2, it is determined whether or not the time α from the current time t1 to the predicted hot water supply usage time t4 is equal to or less than the first predetermined time T1 (for example, 3 hours). If the determination of S2 is Yes, the process proceeds to S3, and if the determination of S2 is No, the process returns to S1. Next, in S3, the advance hot water storage operation for starting hot water storage is started at a time t1 earlier than the hot water storage operation start time t3 set based on the hot water supply usage prediction, and the process proceeds to S4.

Next, in S4, it is determined whether or not there is surplus power. If the determination in S4 is Yes, the process proceeds to S5, and in S5, it is determined whether or not the current time is before the power generation end set time te. If the determination in S5 is Yes, it is possible that the hot water storage can be completed using the surplus electric power, so the process proceeds to S6 to continue the advanced hot water storage operation and proceed to S7. Then, in S7, it is determined whether or not the hot water storage is completed when the advanced hot water storage heat amount becomes equal to the required hot water storage heat amount set based on the hot water supply usage prediction. If the determination in S7 is Yes, the process proceeds to S8 to end the hot water storage operation, and if the determination in S7 is No, the process returns to S4.

On the other hand, if the determination in S4 is No, the process proceeds to S9, and it is determined whether or not the hot water storage completion time t2 when the advanced hot water storage operation is continued in S9 is before the power generation end setting time te. If the judgment of S9 is Yes, it is expected to return to the state with surplus power, so proceed to S5 so that the advanced hot water storage operation can be continued, and if the judgment of S9 is No, S10 to stop the advanced hot water storage operation. Proceed to. Then, in S10, the remaining required hot water storage heat amount (unstored heat amount) obtained by subtracting the advanced hot water storage heat amount up to the time tv when the surplus electric power disappears from the required hot water storage heat amount is calculated, and the remaining required hot water storage heat amount is stored by the hot water supply use time t4. Set the hot water storage operation start time t3'.

Next, in S11, it is determined whether or not the time difference β between the time tv when the surplus power is exhausted and the hot water storage operation start time t3'of the remaining required hot water storage amount is equal to or less than the second predetermined time T2 (for example, 1 hour). If the determination in S11 is Yes, the process proceeds to S5 so that the advanced hot water storage operation can be continued. If the determination in S11 is No, the process proceeds to S13 to stop the advanced hot water storage operation and proceed to S14.

If the determination in S5 is No, the process proceeds to S12, and it is determined whether or not the heat dissipation loss when the advanced hot water storage operation is continued in S12 is smaller than the start-up loss due to the restart of the heat pump type heat source machine 2. The heat dissipation loss is the amount of heat that is reduced by the heat radiation from the hot water storage tank 11. The start-up loss cannot store hot water equivalent to the difference between the amount of heat that can be stored during stable drive and the amount of heat that can be stored when the operating efficiency from start-up to stable drive is low when the heat pump type heat source machine 2 is driven with the same electric power. The amount of heat. If the determination in S12 is Yes, the process proceeds to S6, and if the determination in S12 is No, the process proceeds to S13 to stop the hot water storage operation and proceed to S14.

Next, in S14, it is determined whether or not the hot water storage operation start time t3'for storing the remaining required hot water storage heat amount has been reached by the hot water supply use time t4. If the determination in S14 is Yes, the process proceeds to S15, the hot water storage operation is performed, and the process proceeds to S16. In S16, it is determined whether or not the storage of the remaining required hot water storage heat is completed. If the determination in S16 is Yes, the process proceeds to S8 to end the hot water storage, and if the determination in S16 is No, the process returns to S15. If the determination in S14 is No, the determination in S14 is repeated until the hot water storage operation start time t3'.

The hot water storage when the above hot water storage control is performed will be described with reference to the time charts of FIGS. 4 to 7. At time t1, the time α until the hot water supply usage time t4 is equal to or less than the first predetermined time T1, and since there is surplus electric power, the hot water storage operation is started before the hot water storage operation start time t3 of the required hot water storage heat amount (FIG. 3). See S1 to S3). Then, as in the first example shown in FIG. 4, if the surplus electric power is not exhausted during the execution of the advanced hot water storage operation, the hot water storage of the advanced hot water storage heat amount equivalent to the required hot water storage heat amount is completed at time t2, and the hot water storage is completed. (See S4 to S8 in FIG. 3).

As in the second example shown in FIG. 5, even if there is no surplus power at the time tv during the advance hot water storage operation, the hot water storage completion time t2 when the advance hot water storage operation is continued is before the power generation end setting time te. The advance hot water storage operation is continued by using commercial power or when the surplus power is returned to a state (see S9 in FIG. 3). Then, the hot water storage of the advanced hot water storage heat amount equivalent to the required hot water storage heat amount is completed at time t2, and the hot water storage is completed.

As in the third example shown in FIG. 6, even if the surplus power is exhausted at the time tv during the advanced hot water storage operation and the hot water storage completion time t2 when the advanced hot water storage operation is continued is later than the power generation end setting time te. If the time difference β from the time tv to the hot water storage operation start time t3'is less than or equal to the second predetermined time T2, the advanced hot water storage operation is continued (see S11 in FIG. 3). Since the start-up loss when starting the heat pump type heat source machine 2 at time t3'is larger than the heat dissipation loss from the hot water storage completion time t2 to the hot water supply use time t4, deterioration of operation efficiency is avoided by continuing the hot water storage operation. ..

As in the fourth example shown in FIG. 7, the surplus power disappears at the time tv during the advance hot water storage operation, and the hot water storage completion time t2 when the advance hot water storage operation is continued is after the power generation end setting time te. When the time difference β from the time tv to the hot water storage operation start time t3'is longer than the second predetermined time T2, the hot water storage operation is stopped because the heat dissipation loss is larger than the start loss (see S11 and S13 in FIG. 3). Then, the hot water storage operation of the remaining required hot water storage heat amount is started at the hot water storage operation start time t3'.

The operation and effect of the hot water storage and hot water supply system 1 of the present invention will be described.
The hot water storage and hot water supply system 1 stores the required amount of hot water storage heat required for the predicted hot water supply use in the hot water storage tank 11 by the hot water storage operation, and if the generated power of the photovoltaic power generation device 4 has surplus power that can be sold, the surplus power is used. It can be used for hot water storage operation. In the case of hot water storage operation using surplus electric power, the advance hot water storage operation is performed when the time α from the current time t1 to the predicted hot water supply use time t4 is equal to or less than the first predetermined time T1, so that the storage time in the hot water storage tank 11 Can be shortened to reduce the temperature drop of hot water due to heat dissipation, and the stored hot water is not wasted.

If the surplus power runs out due to the weather or the like during the advance hot water storage operation, if the advance hot water storage operation is continued with the power supplied from the commercial power source, the time zone during which power can be generated differs depending on the installation environment of the photovoltaic power generation device 4. When the hot water storage is completed by the power generation end set time te for which the end time of the above is set, the advanced hot water storage operation is continued. If there is surplus power again while the advanced hot water storage operation is being continued, the surplus power can be used for hot water storage operation, and the operation efficiency of the heat pump type heat source machine 2 can be avoided by avoiding intermittent hot water storage operation. Can be prevented from deteriorating.

If the hot water storage is not completed by the power generation end setting time te, the advanced hot water storage operation is stopped, and the waiting is performed until the hot water storage operation start time t3'of the remaining required hot water storage heat amount of the required hot water storage heat amount. As a result, it is possible to prevent a temperature drop due to heat dissipation until the hot water supply use time t4 of the hot water stored by the advanced hot water storage operation using commercial power. Even when the hot water storage by the advanced hot water storage operation is not completed by the power generation end set time te, the hot water storage operation start time for storing the remaining required hot water storage heat amount, which is the unstored heat amount of the required heat amount, from the time tv when the surplus power is exhausted. When the time difference β up to t3'is equal to or less than the second predetermined time T2, the advanced hot water storage operation is not stopped. This makes it possible to prevent deterioration of operating efficiency due to start-up loss of the heat pump type heat source machine 2.

In addition, a person skilled in the art can carry out the embodiment in a form in which various modifications are added to the above embodiment without deviating from the gist of the present invention, and the present invention also includes such modified forms.

1: Hot water storage system 2: Heat pump type heat source machine 3: Hot water storage unit 4: Solar power generation device 5: Solar panel 6: Junction box 7: Power conditioner 8: Distribution board 9: Commercial power supply line 11: Hot water storage tank 12 : Combustion type heat source machine 13: Control unit (control means)
13a: Operation terminal 21: Circulation heating circuit

Claims (3)

A heat pump type heat source machine, a combustion type heat source machine, a hot water storage tank for storing hot water heated by the hot water storage operation of the heat pump type heat source machine, and a required amount of heat to the hot water storage tank by the hot water supply usage time based on a hot water supply usage prediction. In a hot water storage system equipped with a control means for controlling the hot water storage operation so as to store the hot water and a solar power generation device,
The hot water storage operation is configured to be feasible using the generated power of the solar power generation device, and the control means has surplus power that can be sold in the generated power and is from the current time to the hot water supply use time. When the time is less than or equal to the first predetermined time, the hot water storage operation using the surplus electric power is executed before the hot water storage operation start time set based on the hot water supply usage prediction. Hot water storage and hot water supply system. When the surplus electric power is exhausted during the execution of the advanced hot water storage operation, the control means compares the hot water storage completion time when the advanced hot water storage operation is continued with the power generation end setting time of the photovoltaic power generation device. The first aspect of claim 1, wherein the advanced hot water storage operation is continued when the same time or the hot water storage completion time is earlier, and the advanced hot water storage operation is stopped when the hot water storage completion time is later. Hot water storage and hot water supply system. When the advance hot water storage operation is stopped, the control means has a time when the hot water storage operation is started and a time when the surplus power is exhausted in order to store the unstored heat amount of the required heat amount by the hot water supply use time. The hot water storage system according to claim 2, wherein the advanced hot water storage operation is not stopped when the time difference between the two is not more than the second predetermined time.

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