JP5345879B2 - Solar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately store solar heat collected by a heat collecting panel. <P>SOLUTION: A solar system includes: the heat collecting panel 10 for collecting solar heat; and a storage tank 20 for heating hot water stored inside by the heat collected by the heat collecting panel 10 and supplying the heated hot water to a hot water consuming part 31 or a heat consuming part 30. The solar system further includes: a storage capacity changing means A for changing the amount of hot water stored in the storage tank 20; and a heat collecting state determination means B for determining the heat collecting state by the heat collecting panel 10. When the heat collecting state determination means B determines a high heat collecting state, in which heat quantity higher than that in a low heat collecting state which is determined as the low heat collecting state is collected, the storage capacity changing means A changes the storage capacity of the hot water stored in the storage tank 20 to the larger side. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a heat collecting panel for collecting solar heat, and a storage for heating hot water stored therein by heat collected by the heat collecting panel and supplying the heated hot water to a hot water consumption section or a heat consumption section. The present invention relates to a solar system including a tank.

  A conventional solar system includes a heat collecting panel that collects solar heat and a storage tank that stores hot water heated by the heat collected by the heat collecting panel. A circulation circuit for circulating a heat medium (generally antifreeze) is provided between the heat collection panel and the storage tank, and the heat medium is heated by the heat collected by the heat collection panel. The heated heat medium is supplied to the storage tank, hot water stored in the storage tank is heated, and hot water heated by the heat collected by the heat collection panel is stored in the storage tank. The hot water stored in the storage tank is supplied to a hot water consuming section such as a bathtub or a heat consuming section such as a floor heater or a bathroom dryer, and the hot water stored in the storage tank is filled with water or heated. Yes. In addition, when the temperature of hot water stored in the storage tank is lower than the temperature required by the hot water consumption section or heat consumption section, the hot water stored in the storage tank is heated by the auxiliary heat source unit. In addition, the water is supplied to the hot water consumption section and the heat consumption section (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 11-159889

  In such a solar system, in general, as the storage capacity of hot water stored in the storage tank increases, the amount of hot water that can be stored in the storage tank increases, so a large amount of hot water is supplied to the hot water consumption section and the heat consumption section. The energy saving performance will be improved. However, if the storage capacity of the storage tank is increased too much, the temperature of the hot water stored in the storage tank will be difficult to rise. It becomes impossible to heat to the temperature required in the heat consuming part. Therefore, after the hot water stored in the storage tank is heated by the auxiliary heat source device, the hot water is often supplied to the hot water consumption section and the heat consumption section, which may reduce the energy saving performance.

Therefore, in designing such a storage capacity of the hot water tank in such a system, for example, as shown in FIG. 4, an average value for one year is obtained for the heat collection amount of the heat collection panel. In the average value, the relationship between the storage capacity of the storage tank and COP (coefficient of performance: a coefficient used as a guideline for energy consumption efficiency) is obtained. And it is possible to set the storage capacity of a hot water tank so that it may become the optimal storage capacity (P point in FIG. 4) which shows the highest COP. Note that the COP fluctuation curve in FIG. 4 is obtained when the heat collection area of the heat collection panel is 6 m ² .

  However, at the time of low heat collection such as in winter, the amount of heat collected by the heat collection panel is small, so that the optimum storage capacity tends to decrease (in FIG. 4, the peak P of the fluctuation curve tends to move to the black arrow side). is there. On the contrary, at the time of high heat collection such as summer, the amount of heat collected by the heat collection panel increases, so that the optimum storage capacity tends to increase (in FIG. 4, the apex P of the fluctuation curve moves to the white arrow side). There is a tendency. Therefore, as described above, there is a limit to improving energy savings by simply setting the storage capacity of the storage tank in the solar system to a fixed capacity determined using the average value of the optimal storage capacity throughout the year. It was.

  The present invention has been made paying attention to such a problem, and the purpose thereof is a solar that can appropriately store solar heat collected by a heat collecting panel in a storage tank and improve energy saving performance. The purpose is to realize the system.

In order to achieve this object, a solar system according to the present invention includes a heat collecting panel that collects solar heat, and hot water stored inside is heated by the heat collected by the heat collecting panel. A solar system comprising a storage tank for supplying hot water consumption section or heat consumption section,
The characteristic configuration includes a storage capacity changing unit that changes a storage capacity of hot water stored in the storage tank, and a heat collection state determination unit that determines a heat collection state of the heat collection panel,
When the heat collection state determination unit determines that the heat collection state is a high heat collection state that collects a higher amount of heat than the low heat collection state, the storage capacity changing unit is stored in the storage tank. The storage capacity of the hot water is changed to the larger side ,
The heat collection state determination means includes
In the first determination period for determining the heat collection state, the heat collection state of the heat collection panel is determined based on the highest reached outside air temperature measured by the outside air temperature measurement unit that measures the temperature of the outside air. In the second determination period longer than the first determination period, when the approximate straight line of the highest reached outside air temperature tends to increase, it is determined that the heat collection state is high, and the approximate straight line of the highest reached outside air temperature Is in a downward trend, it is determined that the low heat collection state,
Or
In the said 1st determination period, it is comprised so that the heat collecting state of the said heat collection panel may be determined based on the highest reached hot water temperature which the hot water temperature measurement part which measures the temperature of the hot water stored by the storage tank measures. In addition, in the second determination period longer than the first determination period, when the approximate straight line of the highest reached hot water temperature tends to increase, it is determined that the heat collection state is high, and the highest reached hot water temperature is approximated. When the straight line has a downward trend, the low heat collection state is determined .

According to the above characteristic configuration, when it is determined that the heat collection state of the heat collection panel is higher in the heat collection state than in the low heat collection state, the storage capacity of the storage tank can be changed to a larger side. Therefore, the COP (coefficient of performance) of the entire system can be improved by changing the storage capacity of the storage tank so as to follow the heat collection state.
For example, in the case of a low heat collection state where the amount of heat collected by the heat collection panel is low, such as in winter, the storage capacity of the storage tank is changed to a smaller side, and the temperature of the hot water in the storage tank is likely to rise. COP (coefficient of performance) can be improved by raising the hot water led from the storage tank to the heat consuming unit or the like and reducing the frequency with which the auxiliary heat source device or the like is used.
On the other hand, if the heat collection panel is in a high heat collection state, such as in the summer, the storage capacity of the storage tank is changed to a larger side, and the heat collection in the storage tank is performed in a state where there is a large amount of heat. The solar heat collected by the heat panel can be stored appropriately and the COP (coefficient of performance) can be improved.
From the above, it is possible to realize a solar system that can appropriately save the solar heat collected by the heat collection panel in the storage tank and improve the energy saving performance.
Furthermore, normally, when the highest attained outside air temperature or the highest attained hot water temperature is high, the heat collection state of the heat collection panel is high, and when the highest ultimate outside air temperature or the highest ultimate hot water temperature is low, the heat collection state of the heat collection panel is low. Has a certain relationship. Therefore, according to the above characteristic configuration, for example, when the first determination period for determining the heat collection state is 24 hours (one day), which is the solar heat collection period, based on the highest reached outdoor air temperature or the highest reached hot water temperature. Since the heat collection state of the heat collection panel is determined using a certain relationship between the highest reached outside air temperature or the highest reached hot water temperature and the heat collection state, the heat collection state in the first determination period is appropriately determined. be able to.
Furthermore, the second determination period refers to a period of about one month longer than the first determination period of, for example, about 24 hours (one day). In addition, when the highest reached hot water temperature or the highest reached outdoor air temperature tends to increase, a change tendency (inclination of increase) of the highest reached hot water temperature or the highest reached outdoor air temperature is set in advance in the second determination period. Larger than the slope of the high heat collection state judgment line
Say goodbye. On the other hand, when the highest reached hot water temperature or the highest reached outdoor air temperature is in a downward trend, the change tendency (the downward slope) of the highest reached hot water temperature or the highest reached outdoor air temperature is preset in the second determination period. A case where the slope is smaller than the slope of the low heat collection state determination line.
According to the above characteristic configuration, since the heat collection state is determined in the second determination period based on whether the highest reached hot water temperature or the highest reached outside air temperature is in an upward trend or a downward trend, the maximum attainment at a certain point in time is simply performed. The heat collection state can be determined with higher accuracy than in the case where the determination is made only from the value of the hot water temperature or the maximum attained outside air temperature.
As described above, also in this determination, once the predetermined heat collection state is determined, the current heat collection state is maintained until it is determined that the current heat collection state is different from the current heat collection state. It shall continue to be determined that there is.

  According to a further characteristic configuration of the present invention, the storage capacity changing means is an open / closed state of a supply intermittent valve for intermittently supplying water to the storage tank and a discharge intermittent valve for intermittently discharging hot water from the storage tank. To change the storage capacity of the storage tank.

According to the above characteristic configuration, the storage capacity of the storage tank is changed by switching the open / close state of the supply intermittent valve or the discharge intermittent valve based on the heat collection state of the heat collection panel. The storage capacity of the storage tank can be adapted to the heat collection amount of the heat collection panel by a relatively simple operation without physically changing.
For example, when it is determined that the heat collection state is low in winter, etc., the storage capacity is reduced by draining hot water from the storage tank with the discharge intermittent valve open until the water level measurement unit measures the low water level. The storage capacity can be made suitable for a low heat collection state.
On the other hand, when it is determined that the heat collection state is high in summer, etc., the water supply interrupting valve is opened until the water level measurement unit measures the high water level, supplying water to the storage tank and increasing the storage capacity. The storage capacity can be made suitable for a high heat collection state.
In addition, after changing the storage capacity of the storage tank based on the determination result of the heat collection state determination means, the storage capacity of the storage tank is not changed until the determination of the heat collection state different from the current heat collection state is made. It adjusts suitably so that a storage capacity may be maintained.

  According to a further feature of the present invention, the storage capacity changing means switches the open / close state of a storage space interrupting valve that intermittently connects a plurality of storage spaces provided in the storage tank, and stores the storage space. The capacity of the storage space of the tank is changed.

  According to the above characteristic configuration, the capacity of the storage space in which the hot water is stored is changed by opening and closing the storage space intermittent valve according to the heat collection state of the heat collection panel. The storage capacity of the storage tank can be adapted to the heat collection amount of the heat collection panel in a relatively short time.

It is a schematic block diagram of the solar system of this invention. The graph which shows the change tendency of the maximum hot water (outside air) temperature and the heat collection state judgment method based on it The figure which shows another embodiment of the storage tank and storage capacity change means of this invention. The figure which shows the fluctuation | variation of COP with respect to the storage capacity of a storage tank

Prior to the description of the solar system according to the present invention, its basic configuration will be described with reference to FIG.
As shown in FIG. 1, the solar system of the present invention includes a heat collecting panel 10 that collects solar heat, a hot water supply unit such as a bathtub (an example of the hot water consumption unit 30) or a heater, a floor heating panel, and a bathroom dryer. And a storage tank 20 to be supplied to a machine (an example of the heat consumption unit 31). A circulation circuit 11 in which a heat medium circulates is provided between the heat collection panel 10 and the storage tank 20, and solar heat collected by the heat collection panel 10 circulates in the circulation circuit 11. The heat medium is guided to the heat exchanging unit 21 provided inside the storage tank 20 and is stored as heat of hot water in the storage tank 20.

  The inside of the heat collecting panel 10 is configured so that the heat medium is heated by solar heat and naturally convects from below to above, and the heat medium forms a temperature stratification from above to below. Then, the heat medium warmed by the heat collecting panel 10 is guided to the outgoing path of the circulation circuit 11 described later.

  The circulation circuit 11 connects the forward path above the heat collection panel 10, connects the return path below the heat collection panel 10, and exchanges heat between the forward path and the return path provided in the storage tank 20. It arrange | positions so that the part 21 may be interposed. When the heat collection panel 10 has a predetermined amount of heat collection, the heat medium is pumped by the circulation pump P provided in the circulation circuit 11, and the heat collection panel 10 and the heat exchange unit 21 of the storage tank 20 are exchanged. The amount of heat obtained in the heat collecting panel 10 is circulated through the space, and the hot water stored in the storage tank 20 is heated by dissipating heat in the heat exchange unit 21. A first temperature sensor 12 that measures the temperature of the heat medium that has exited the heat collecting panel 10 is provided in the outgoing path of the circulation circuit 11, and the heat that has exited from the storage tank 20 is provided in the return path of the circulation circuit 11. A second temperature sensor 13 for measuring the temperature of the medium is provided.

  The storage tank 20 is a storage tank surrounded by a heat insulating material (not shown), and is configured to be able to increase the water level by adjusting the water supply by switching the open / close state of the water supply intermittent valve 22. The water level can be lowered by adjusting the drainage by switching the open / close state of the drainage intermittent valve 23. The storage tank 20 is provided with a pair of high water level sensors 24 for detecting a high water level and a pair of low water level sensors 25 for detecting a low water level as energized water level sensors.

  The hot water stored in the storage tank 20 can be circulated and supplied to the hot water consumption section 30 such as a hot water supply section, and can be circulated and supplied to the heat consumption section 31 such as a heater, a bathroom dryer, and a floor heating panel. ing. Hot water discharged from the storage tank 20 is adjusted to an appropriate temperature by an external water supply (not shown) or an auxiliary heat source device 32 and then supplied to the hot water consumption unit 30 or the heat consumption unit 31.

  The above is the basic configuration of the solar system of the present invention. Hereinafter, the characteristic configuration of the solar system of the present invention will be described with reference to FIGS. 1 and 2. The solar system of the present invention is characterized in that the storage capacity changing means A changes the storage capacity of the storage tank 20 based on the determination result of the heat collection state determination means B that determines the heat collection state of the heat collection panel 10. And

  As shown in FIG. 1, the control device 40 measures the temperature of the heat medium that has exited the first temperature sensor 12 that measures the temperature of the heat medium that has exited the heat collection panel 10 and the heat exchange unit 21 of the storage tank 20. Based on the measured temperature of the second temperature sensor 13 to be measured, the driving state of the circulation pump P is determined. For example, when the measured temperature of the first temperature sensor 12 is higher than the measured temperature of the second temperature sensor 13, the hot water stored in the storage tank 20 can be heated by the heat collected by the heat collection panel 10. And the circulation pump P is driven. Conversely, when the measured temperature of the first temperature sensor 12 is lower than or equal to the measured temperature of the second temperature sensor 13, hot water stored in the storage tank 20 by the heat collected by the heat collection panel 10 is used. It is determined that heating is not possible, and the circulation pump P is stopped.

[Storage capacity change means]
Furthermore, the control device 40 functions as a storage capacity changing unit A that changes the storage capacity of the storage tank 20 based on the determination result of the heat collection state of the heat collection panel 10.
When it is determined that the heat collecting panel 10 is in the high heat collecting state, the control device 40 detects that the lower of the high water level is below the lower limit of one of the pair of high water level sensors 24, the high water level sensor 24 Until it is detected that the upper limit of the water level has been reached, the water supply intermittent valve 22 is opened to supply hot water into the storage tank 20. Thereby, the control apparatus 40 is setting the storage capacity to the high water level level in the high heat collection state.
On the other hand, when it is determined that the heat collecting panel 10 is in the low heat collecting state, when one of the pair of low water level sensors 25 detects an upper limit of the low water level or more, the low water level is detected by one of the pair of low water level sensors 25. Until the level becomes less than the upper limit, the drainage intermittent valve 23 is opened to lower the water level. Further, when the other of the pair of low water level sensors 25 detects that the low water level is less than the lower limit, the water supply intermittent valve 22 is opened until the other of the low water level sensors 25 detects that the upper limit of the low water level has been reached. Hot water is supplied into the storage tank 20 by valve. Thereby, the control apparatus 40 is setting the storage capacity to the low water level level in the low heat collection state.
From the above, when the heat collection state of the heat collection panel is higher than the low heat collection state, the storage capacity of the storage tank 20 is changed to a larger side and the COP (coefficient of performance) of the solar system is increased. Can be made.

[Heat collection state determination means]
Since the control apparatus 40 of this invention determines a heat collecting state based on the external temperature or the stored hot water temperature, the embodiment is based on FIG. 2 in the following (A) and (B). I will explain.
In the first determination period T1, which is 24 hours (one day), which is the solar heat collection period, the control device 40 reaches the maximum reached by the outside air temperature sensor 14 (an example of the outside air temperature measurement unit) that measures the outside air temperature. The heat collection state of the heat collecting panel is determined based on the hot water temperature sensor 15 (an example of the hot water temperature measuring unit) that measures the outside air temperature or the temperature of hot water stored in the storage tank 20. It also functions as the heat collection state determination means B.
In the heat collection state determination means B, the determination is made in substantially the same manner based on either the highest reached hot water temperature or the highest reached outdoor air temperature. A method will be described.

(A) [determination using the slope of the approximate straight line and the slope of the judgment line of the maximum hot water temperature]
First, the determination method for determining the heat collection state of the storage tank 20 by comparing the inclination of the approximate straight line of the maximum hot water temperature with the inclination of the determination line stored in advance by the heat collection state determination means B will be described. .
In FIG. 2 (a), the black circles represent the maximum reached hot water temperature in each first determination period T1, and the solid line represents the approximate straight line f1 (maximum reached hot water temperature in the second determination period T2 longer than the first determination period). For example, it is derived based on the least square method or the like), and the alternate long and short dash line represents the high heat collection state determination straight line f2. The second determination period T2 is specifically determined as a period of about one month.
In the second determination period T2, for example, when the inclination of the approximate straight line f1 of the maximum reached hot water temperature is larger than the inclination α of the high heat collection state determination line f2, the control device 40 determines that the heat collection state is high. .
Also in FIG. 2 (b), the black circle and the solid line indicate the same as in FIG. 2 (a), but the alternate long and short dash line f4 indicates the low heat collection state determination straight line f4. . In the second determination period T2, for example, when the inclination of the approximate straight line f1 of the maximum reached hot water temperature is smaller than the inclination β of the low heat collection state determination line f4, the control device 40 determines that the heat collection state is low.

(B) [Judgment Using Maximum Achieving Temperature Value and Judgment Threshold]
Next, a determination method in which the heat collection state determination means B determines the heat collection state of the storage tank 20 by comparing the maximum reached hot water temperature value with a determination threshold value will be described.
In FIG. 2A, a two-dot chain line indicates a high heat collection state determination threshold f3. In the second determination period T2 of about one month, for example, the control device 40, for example, when the highest reached hot water temperature exceeds the high heat collection state determination threshold f3 more than a predetermined number of times, or continuously, the high heat collection state determination threshold value When it exceeds f3, it determines with it being a high heat collection state.
On the other hand, in FIG. 2B, the two-dot chain line indicates the low heat collection state determination threshold f5. In the second determination period T2 of about one month, for example, the control device 40 is configured such that, for example, the maximum reached hot water temperature is lower than the low heat collection state determination threshold f5 more than a predetermined number of times or continuously. When it is less than f5, it is determined that the heat collecting state is low.
Thus, in 2nd determination period T2 longer than 1st determination period T1, it determines based on the value of several maximum ultimate hot water temperature, for example, the maximum ultimate hot water temperature in a certain time, and the high heat collection state determination threshold value Compared with the case where f3 or the low heat collection state determination threshold f5 is compared, the determination accuracy can be increased.

  Here, the high heat collection state determination threshold f3 is a temperature of about 25 degrees to 40 degrees when determined using the outside air temperature, and a temperature of about 70 degrees to 90 degrees when determined using the hot water temperature. It is. On the other hand, the low heat collection state determination threshold f5 is a temperature of about 0 to 15 degrees when determined using the outside air temperature, and a temperature of 10 to 30 degrees when determining using the hot water temperature. is there.

[Another embodiment]
( 1 ) The storage tank 20 can be configured by providing a water pressure measurement type water level sensor 26 as shown in FIG. 3 (a), and the control means 40 is based on the measurement result of the water level sensor 26. It can also function as storage capacity changing means A that changes the storage capacity of the storage tank 20. According to this, by providing the single water pressure measurement type water level sensor 26, it is possible to measure both the high water level and the low water level, and to easily set the multi-stage water level.

( 2 ) As shown in FIG. 3 (b), the storage tank 20 is divided into a plurality of storage spaces V1 to V3, and a first intermittent valve that intermittently connects a communication path that connects the storage spaces V1 and V2. 27 and a storage tank having a sealed divided storage space provided with a second intermittent valve 28 that intermittently connects the communication path that connects the storage spaces V2 and V3. In the said structure, the heat exchange part 21 is arrange | positioned so that the hot water stored in the storage space V1 may be heated.
The control device 40 functions as storage capacity changing means A that appropriately changes the storage capacity of the storage tank 20 by switching the open / close state of the first intermittent valve 27 and the second intermittent valve 28. For example, when the storage capacity is small, the first intermittent valve 27 is closed and only the first storage space V1 is usable. When the storage capacity is a medium capacity, the first intermittent valve 27 is opened and the second intermittent valve 28 is closed so that only the first storage space V1 and the second storage space V2 can be used. . When the storage capacity is large, both the first intermittent valve 27 and the second intermittent valve 28 are opened, and all the storage spaces V1 to V3 are made usable.

( 3 ) In the above embodiment, the first determination period T1 is 24 hours (one day), which is the solar heat collection period, but it may be only during the daytime from sunrise to sunset when solar heat can be recovered. Moreover, it is good also as a period longer than 24 hours (1 day) which is a heat collection period, for example, it is good also as a period of about one week.

( 4 ) In the above embodiment, the second determination period T2 is a period of about one month, but is a period longer than the first determination period T1, and is six months (period between summer and winter) Any period may be used as long as it is shorter.

( 5 ) In the above-described embodiment, the heat collection state determination means B has been described as performing the two-stage determination of the low heat collection state and the high heat collection state. Thus, it is possible to perform multi-stage determination.
For example, in the above-described embodiment, the heat collection state determination means B determines the heat collection state, the rotation speed of the circulation pump that circulates the heat medium, the high heat collection state determination rotation speed, and the low heat collection state determination. Although the determination is made by comparing with the rotation speed, the determination may be made by comparison with the medium heat collection state determination rotation speed at which the heat collection state is medium.
Moreover, in the said another embodiment, when the heat collection state determination means B determined the heat collection state, it determined based on the high heat collection state determination threshold value and the low heat collection state determination threshold value. The determination may be made in comparison with a medium heat collection state determination threshold value that is medium.

  The solar system of the present invention can be effectively used as a solar system capable of appropriately storing solar heat collected by a heat collection panel.

DESCRIPTION OF SYMBOLS 10: Heat collection panel 11: Circulation circuit 12: 1st temperature sensor 13: 2nd temperature sensor 14: Outside temperature sensor 15: Hot water temperature sensor 20: Reservoir 21: Heat exchange part 22: Water supply interruption valve 23: Drainage interruption valve 24: High water level sensor 25: Low water level sensor 30: Hot water supply unit 31: Heat consumption unit A: Storage capacity switching unit B: Heat collection state determination unit T1: First determination period T2: Second determination period f3: High heat collection state Determination threshold value α: High heat collection state determination straight line slope f5: Low heat collection state determination straight line β: Low heat collection state determination straight line inclination 27: First intermittent valve 28: Second intermittent valve V1: First storage space V2: Second storage space V3: Third storage space

Claims (3)

A heat collecting panel for collecting solar heat,
A solar system comprising a storage tank that heats hot water stored inside by the heat collected by the heat collecting panel and supplies the heated hot water to a hot water consumption section or a heat consumption section,
A storage capacity changing means for changing a storage capacity of hot water stored in the storage tank;
A heat collecting state determining means for determining a heat collecting state of the heat collecting panel;
When the heat collection state determination unit determines that the heat collection state is a high heat collection state that collects a higher amount of heat than the low heat collection state, the storage capacity changing unit is stored in the storage tank. The storage capacity of the hot water is changed to the larger side ,
The heat collection state determination means includes
In the first determination period for determining the heat collection state, the heat collection state of the heat collection panel is determined based on the highest reached outside air temperature measured by the outside air temperature measurement unit that measures the temperature of the outside air. In the second determination period longer than the first determination period, when the approximate straight line of the highest reached outside air temperature tends to increase, it is determined that the heat collection state is high, and the approximate straight line of the highest reached outside air temperature Is in a downward trend, it is determined that the low heat collection state,
Or
In the said 1st determination period, it is comprised so that the heat collecting state of the said heat collection panel may be determined based on the highest reached hot water temperature which the hot water temperature measurement part which measures the temperature of the hot water stored by the storage tank measures. In addition, in the second determination period longer than the first determination period, when the approximate straight line of the highest reached hot water temperature tends to increase, it is determined that the heat collection state is high, and the highest reached hot water temperature is approximated. The solar system which determines that it is the said low heat collecting state, when a straight line has the downward tendency.   The storage capacity changing means switches the open / closed state between a supply interrupt valve for intermittently supplying water to the storage tank and a discharge interrupt valve for intermittently discharging hot water from the storage tank to store the storage tank. The solar system according to claim 1, wherein the capacity is changed.   The storage capacity changing means changes a capacity of the storage space of the storage tank by switching an open / close state of a storage space intermittent valve that intermittently connects a communication path connecting a plurality of storage spaces provided in the storage tank. The solar system according to claim 1.

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