Solar heat utilization system

Abstract

To provide a solar heat utilization system capable of stably supplying heat to a heat utilization part side.SOLUTION: The solar heat utilization system 100 includes the second flow path 4 that heats the second heating medium by using the heat of the first heating medium in the heat storage tank 2 and causes the heated second heating medium to flow to the heat utilization unit, the heat exchanger that is provided in the portion of the second flow path 4 passing through the heat storage tank and that performs heat exchange between the first heating medium and the second heating medium, the third flow path 5 that branches from the second flow path 4, does not pass through the heat exchanger, and through which the second heating medium heated by solar heat in the heat collector 1 flows, and the switching unit 7 that switches the flow path through which the second heating medium flows between the second flow path 4 and the third flow path 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solar heat utilization system, and more particularly to a solar heat utilization system equipped with a heat collector. [Background technology]

[0002] BACKGROUND ART Conventionally, a solar heat utilization system equipped with a heat collector is known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a solar energy system (solar heat utilization system) including a heat collector that collects solar energy and a heat exchange system that operates using the energy collected by the heat collector. In Patent Document 1, energy is supplied from the heat collector to the heat exchange system via a heat medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6375294 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the solar heat utilization system (solar energy system) of Patent Document 1, when there is almost no solar radiation, such as at night, the heat collector cannot collect heat and the heat medium is not heated. In this case, it becomes difficult to supply heat to the heat utilization section (heat exchange system). Therefore, there is a demand for a solar heat utilization system that can stably supply heat to the heat utilization section.

[0006] This invention has been made to solve the above-mentioned problems, and one object of this invention is to provide a solar thermal utilization system that can stably supply heat to the heat utilization section. [Means for solving the problem]

[0007] In order to achieve the above object, a solar thermal utilization system according to one aspect of the present invention comprises a heat collector that collects solar heat and heats a first heat medium, a heat storage tank that stores the first heat medium heated in the heat collector, a first flow path that connects the heat collector and the heat storage tank, a second flow path that uses the heat of the first heat medium in the heat storage tank to heat a second heat medium and circulates the heated second heat medium to a heat utilization section, a heat exchanger that is provided in a portion of the second flow path that passes through the heat storage tank and exchanges heat between the first heat medium and the second heat medium, a third flow path that branches off from the second flow path, does not pass through the heat exchanger, and through which the second heat medium heated by solar heat in the heat collector circulates, and a switching section that switches the flow path through which the second heat medium circulates between the second flow path and the third flow path.

[0008] As described above, a solar thermal utilization system according to one aspect of the present invention includes a second flow path that uses heat from a first heat medium in a heat storage tank to heat a second heat medium and circulates the heated second heat medium through a heat utilization unit; a heat exchanger located at a portion of the second flow path that passes through the heat storage tank and performs heat exchange between the first heat medium and the second heat medium; a third flow path that branches off from the second flow path, does not pass through the heat exchanger, and through which the second heat medium heated by solar heat in the solar collector circulates; and a switching unit that switches the flow path through which the second heat medium circulates between the second flow path and the third flow path. By switching to the third flow path using the switching unit, the second heat medium can be directly heated in the solar collector, thereby efficiently supplying sufficient heat to the heat utilization unit with minimal energy loss. Furthermore, by switching to the second flow path using the switching unit, heat can be stored in the first heat medium in the solar storage tank during times when solar heat is available, and the second heat medium can be heated using the heat of the first heat medium in the solar storage tank. Furthermore, by switching to the second flow path using the switching unit, heat can be stored in the first heat medium in the heat storage tank during the hours when solar heat can be used, and sufficient heat can be supplied from the first heat medium in the heat storage tank to the second heat medium during the night when solar heat cannot be used.As a result, heat can be supplied stably to the heat utilization unit.

[0009] In the solar thermal utilization system according to the above aspect, preferably, the switching unit includes a switching valve that switches between the second flow path and the third flow path, and further includes a control unit that controls switching of the switching valve. With this configuration, the control unit can easily switch between the second flow path and the third flow path by switching the switching valve, and therefore it is possible to easily switch to a flow path that can stably supply heat to the second heat medium.

[0010] In this case, the system further includes a temperature sensor that detects the temperature of at least one of the first heat medium or the second heat medium, and the control unit is configured to control the switching of the switching valve based on the detection result of the temperature sensor. With this configuration, the control unit can switch between the second flow path and the third flow path based on the temperature of the first heat medium or the second heat medium, so that when the temperature sensor detects that the first heat medium is high, the control unit can switch to the second flow path so that heat exchange occurs between the first heat medium and the second heat medium. Furthermore, when the temperature sensor detects that the second heat medium is low, the control unit can switch to the flow path that can efficiently heat the second heat medium, based on the temperature of the first heat medium detected by the temperature sensor, between the second flow path in which the second heat medium is heated by heat exchange with the first heat medium, and the third flow path in which the second heat medium is directly heated by the heat collector.

[0011] In the solar thermal utilization system according to the above aspect, the heat exchanger preferably includes a first heat exchanger disposed in the heat storage tank, in which heat exchange occurs between the first heat medium in the heat storage tank and the second heat medium flowing through the second flow path, and a second heat exchanger disposed in the heat storage tank downstream of the first heat exchanger, in which heat exchange occurs between the first heat medium flowing through the first flow path and the second heat medium flowing through the second flow path. With this configuration, the first heat exchanger and the second heat exchanger can heat the second heat medium with the first heat medium in the heat storage tank, and then heat the second heat medium with the first heat medium heated by the heat collector, which has a higher temperature than the first heat medium in the heat storage tank. As a result, even if the temperature of the first heat medium in the heat storage tank is low, the second heat medium can be sufficiently heated by heating the second heat medium with the first heat medium heated by the heat collector, which has a higher temperature than the first heat medium in the heat storage tank. Furthermore, since the heat exchanger is disposed inside the heat storage tank, even if the heat of the first heat medium leaks out of the heat exchanger, the heat is stored in the first heat medium inside the heat storage tank, thereby reducing energy loss.

[0012] In this case, the second heat exchanger is preferably a double-pipe heat exchanger having the second flow path disposed on the inside and the first flow path disposed on the outside. With this configuration, since the first flow path is disposed on the outside, when heat is imparted from the first heat medium to the second heat medium circulating in the second heat exchanger, leakage of the heat imparted to the second heat medium to the outside of the second heat exchanger can be suppressed, thereby suppressing energy loss.

[0013] In the solar thermal utilization system according to the above aspect, the first flow path preferably includes an inlet-side flow path that supplies the first heat medium from the heat collector to the heat storage tank via either an upper inlet located above the vertical center of the heat storage tank or a lower inlet located below the vertical center of the heat storage tank, an outlet-side flow path that supplies the first heat medium from the heat collector to the heat storage tank via either an upper outlet located above the vertical center of the heat storage tank or a lower outlet located below the vertical center of the heat storage tank, an inlet-side flow path switching unit that switches between the upper inlet and the lower inlet, and an outlet-side flow path switching unit that switches between the upper outlet and the lower outlet. With this configuration, when a relatively low-temperature first heat medium is stored below the heat storage tank, by switching the inlet-side flow path from the upper inlet to the lower inlet by the inlet-side flow path switching unit, the first heat medium heated in the heat collector can be supplied to the relatively low-temperature first heat medium stored below the heat storage tank, thereby heating the first heat medium stored below. Furthermore, by switching the outlet-side flow path from the upper outlet to the lower outlet using the outlet-side flow path switching unit, the first heat medium stored below and having a relatively low temperature can be supplied to the heat collector and heated.

[0014] In this case, preferably, the system further includes a control unit that switches between the inlet-side flow path switching unit and the outlet-side flow path switching unit based on the temperature of the heat storage tank. With this configuration, when the temperature in the upper part of the heat storage tank is high, the inlet-side flow path switching unit switches the inlet-side flow path from the upper inlet to the lower inlet, so that the first heat medium heated in the heat collector can be supplied to the lower first heat medium, which has a relatively low temperature. Also, when the temperature in the lower part of the heat storage tank is low, the outlet-side flow path switching unit switches the outlet-side flow path from the upper outlet to the lower outlet, so that the lower first heat medium, which has a relatively low temperature, can be heated in the heat collector.

[0015] In the solar thermal utilization system according to the above aspect, preferably, the first flow path includes a pump, and further includes a bypass flow path branching from the first flow path and bypassing the pump, and the bypass flow path is provided with a relief valve that opens in response to the pressure of the first heat medium in the heat storage tank. With this configuration, for example, when the pressure in the heat storage tank increases after the pump stops, the relief valve opens, and the pressure can be used to press the first heat medium from the heat storage tank to the heat collector, thereby circulating the first heat medium. As a result, even when the pump stops, the temperature of the first heat medium can be lowered by circulating the first heat medium, and the pressure in the heat storage tank can be lowered.

[0016] In the solar thermal utilization system according to the above aspect, the heat storage tank is preferably configured to suppress freezing by the second heat medium heated by the heat utilization unit. With this configuration, freezing of the heat storage tank is suppressed by the second heat medium heated in the heat utilization unit, so that it is not necessary to change the first heat medium to an antifreeze liquid or to remove the first heat medium from the heat storage tank in order to suppress freezing.

[0017] In the solar thermal utilization system equipped with the control unit, preferably, the heat utilization unit uses the heat of the second heat medium to cool the air and includes a fan that circulates the cooled air, and the control unit is configured to control the fan to have a higher rotation speed when the temperature inside the heat storage tank is equal to or higher than a predetermined temperature than when the temperature inside the heat storage tank is below the predetermined temperature. With this configuration, increasing the rotation speed of the fan increases the amount of cooling of the air in the heat utilization unit, and therefore increases the amount of heat of the first heat medium supplied to the second heat medium. As a result, when the temperature inside the heat storage tank is equal to or higher than the predetermined temperature, the heat inside the heat storage tank can be efficiently utilized to lower the temperature inside the heat storage tank.

[0018] In this case, the heat utilization unit preferably includes a cold storage material disposed downstream of the fan, and the control unit is configured to control the rotation speed of the fan so that the temperature of the air blown to the cold storage material is equal to or lower than the freezing point of the cold storage material when the temperature inside the heat storage tank is equal to or higher than a predetermined temperature. With this configuration, by increasing the rotation speed of the fan so that the temperature is equal to or lower than the freezing point of the cold storage material, the cold storage material can be solidified and cold stored, and therefore the energy inside the heat storage tank can be used to cool the heat utilization unit.

[0019] In the solar thermal utilization system according to the above aspect, the heat storage tank is preferably configured to be adjacent to either a storage unit that stores items to be heated using the second heat medium or a container that stores items to be heated using the second heat medium. With this configuration, when heat leaks from the heat storage tank to the outside, the storage unit or the container can be heated by the leaked heat, and the storage unit or the container can be efficiently heated by the second heat medium and the heat leaked from the heat storage tank. As a result, the heat leaked from the second heat medium and the heat storage tank is used to heat the storage unit or the container, thereby suppressing energy loss.

[0020] In the solar heat utilization system according to the above aspect, the heat utilization unit is preferably one of a vending machine, an item storage unit, an air conditioner, and a beverage brewing device. With this configuration, solar heat can be utilized for heating or cooling any of the vending machine, the item storage unit, the air conditioner, and the beverage brewing device. [Effects of the Invention]

[0021] According to the present invention, as described above, it is possible to provide a solar heat utilization system capable of stably supplying heat to the heat utilization section side. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating an example of a solar heat utilization system according to a first embodiment. [Figure 2]6 is a flowchart of control for switching between the second flow path and the third flow path in the first embodiment. [Figure 3] FIG. 2 is a diagram for explaining a case where the heat utilization unit in the first embodiment is a vending machine. [Figure 4] FIG. 10 is a diagram for explaining another example in which the heat utilization unit in the first embodiment is a vending machine. [Figure 5] FIG. 2 is a diagram for explaining an example in which the heat utilization section is an item storage section in the first embodiment. [Figure 6] FIG. 2 is a diagram for explaining an example in which the heat utilization unit in the first embodiment is an air conditioner. [Figure 7] FIG. 3 is a diagram showing another example of the solar heat utilization system in the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of a solar heat utilization system according to a second embodiment. [Figure 9] FIG. 4 is a diagram illustrating an example of a second heat exchanger. [Figure 10] FIG. 10 is a diagram illustrating an example of a solar heat utilization system according to a third embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of a solar heat utilization system according to a fourth embodiment. [Figure 12] FIG. 10 is a diagram showing another example of the solar heat utilization system according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0024] The configuration of a solar heat utilization system 100 according to the first embodiment will be described with reference to FIGS.

[0025] [First embodiment] The solar thermal utilization system 100 shown in FIG. 1 includes a solar collector 1, a heat storage tank 2, a first flow path 3, a second flow path 4, a third flow path 5, a heat exchanger 6, a switching unit 7, a control unit 8, and a temperature sensor 9. The solar thermal utilization system 100 is composed of two components: a heat utilization unit 10 and a heat collection unit 20. The heat utilization unit 10 includes an ejector flow path and a refrigeration cycle. The heat collection unit 20 includes at least the solar collector 1. Note that in the drawings of the present application, the portion enclosed by a dashed square indicates that it is a single device. In FIG. 1, the dashed square indicates that the heat utilization unit 10 and the heat collection unit 20 are separate entities. Also, in the drawings of the present application, the ejector flow path and the refrigeration cycle included in the heat utilization unit 10 are separated by a dashed line.

[0026] The solar collector 1 is configured to collect solar heat and heat a first heat medium. The solar collector 1 is provided with piping that forms a first flow path 3. As an example, the first heat medium is water. The first heat medium is heated by heat exchange with solar heat as it passes through the solar collector 1. The solar collector 1 is provided at an angle to the vertical direction, and the first heat medium flows obliquely from the lower side to the upper side in the vertical direction. The solar collector 1 is also configured so that the temperature of the first heat medium on the upper side is higher than that of the first heat medium on the lower side.

[0027] The heat storage tank 2 is configured to store the first heat medium heated in the heat collector 1. As an example, the heat storage tank 2 is a tank. A heat exchanger 6 is arranged in the heat storage tank 2, which exchanges heat between the first heat medium and the second heat medium. Of the first heat medium stored in the heat storage tank 2, the first heat medium located at the top has a higher temperature than the first heat medium located at the bottom. Furthermore, although the first heat medium in the heat storage tank 2 is generally in a liquid phase, depending on the degree of heating of the heat collector 1, the first heat medium located at the top may become a gas phase.

[0028] The first flow path 3 is configured to connect the heat collector 1 and the heat storage tank 2. The first flow path 3 is configured with piping. A pump 11 is provided in the first flow path 3, and by driving the pump 11, a first heat medium is circulated between the heat collector 1 and the heat storage tank 2. The first flow path 3 includes a flow path connecting the heat collector 1 to an outlet located on the lower side of the heat storage tank 2, a flow path passing through the heat collector 1, and a flow path connecting the heat collector 1 to an inlet located on the upper side of the heat storage tank 2. The first heat medium flowing through the first flow path 3 is configured to flow obliquely from the lower side to the upper side of the heat collector 1, which is inclined with respect to the vertical direction, and then flow into the heat storage tank 2 from the upper side of the heat storage tank 2. Furthermore, the first heat medium flowing through the first flow path 3 is configured to flow into the heat storage tank 2 from the upper side of the heat storage tank 2, and then flow from the lower side of the heat storage tank 2 into the lower side of the heat collector 1 by the pump 11.

[0029] The second flow path 4 is configured to heat the second heat medium by utilizing the heat of the first heat medium in the heat storage tank 2, and to circulate the heated second heat medium to the heat utilization section 10. A heat exchanger 6 is provided in the portion of the second flow path 4 that passes through the heat storage tank 2. The heat exchanger 6 is configured to exchange heat between the first heat medium and the second heat medium. The second heat medium is, for example, ammonia or carbon dioxide.

[0030] The second flow path 4 includes an ejector flow path provided with an ejector 41, an evaporator 42, and a condenser 43, through which the second heat medium flows. The ejector 41 is configured to mix the low-pressure second heat medium supplied from the evaporator 42 with the high-temperature, high-pressure second heat medium that has flowed through the heat collector 1 or the heat storage tank 2, and supply the medium-pressure second heat medium to the condenser 43. The ejector 41 is configured to inject the high-temperature, high-pressure second heat medium that has flowed through the heat collector 1 or the heat storage tank 2, thereby injecting the medium-pressure second heat medium while mixing it with the low-pressure second heat medium supplied from the evaporator 42. The medium-pressure second heat medium injected from the ejector 41 is condensed and cooled in the condenser 43, and then a portion of it is heated in the evaporator 42 by heat exchange with the second heat medium flowing in the refrigeration cycle. The remaining second heat medium is condensed in the condenser 43, and then flows into the heat collector 1 via the third flow path 5, or into the heat storage tank 2 via the second flow path 4. The ejector flow path is provided with a flow path switching unit 45. The flow path switching unit 45 is configured to switch between a flow path that supplies the second heat medium that has flowed through the heat collector 1 or the heat storage tank 2 to the ejector 41, and a flow path that heats or cools the second heat medium with air that has been heated or cooled in the heating and cooling unit 44 of the refrigeration cycle.

[0031] The third flow path 5 branches off from the second flow path 4 and is configured so as not to pass through the heat exchanger 6. The third flow path 5 is configured so that the second heat medium heated by solar heat in the solar collector 1 flows through it. The third flow path 5 branches off from the second flow path 4 and passes through the solar collector 1 without passing through the thermal storage tank 2, before returning to the second flow path 4. The third flow path 5 is configured so as to return to the second flow path 4 near the outlet of the heat exchanger 6. The third flow path 5 is provided with a check valve 5a that prevents the second heat medium from flowing backward from the ejector flow path side toward the solar collector 1 side.

[0032] The heat exchanger 6 is disposed above the heat storage tank 2. As an example, the heat exchanger 6 is a throw-in type heat exchanger. The heat exchanger 6 has a coil shape and is disposed in the first heat medium stored in the heat storage tank 2. In other words, the heat exchanger 6 constitutes part of the second flow path 4 and is surrounded by the first heat medium. Therefore, when the second heat medium flows through the heat exchanger 6, the second heat medium exchanges heat with the first heat medium and receives heat from the first heat medium, thereby heating the second heat medium.

[0033] The switching unit 7 is configured to switch the flow path through which the second heat medium flows between the second flow path 4 and the third flow path 5. The switching unit 7 includes a switching valve 7a that switches between the second flow path 4 and the third flow path 5. The switching valve 7a is, for example, a three-way valve. The switching valve 7a is connected to a flow path through which the second heat medium flows from the ejector flow path, the second flow path 4 connected to the inlet of the heat exchanger 6, and the third flow path 5. The switching valve 7a is also configured to use the flow path through which the second heat medium flows from the ejector flow path as its inlet, and switch between an outlet connected to the second flow path 4 connected to the inlet of the heat exchanger 6 and an outlet connected to the third flow path 5.

[0034] The control unit 8 is configured to control the switching of the switching valve 7a. The control unit 8 is, for example, the control unit 8 of the heat utilization unit 10.

[0035] The temperature sensor 9 detects the temperature of at least one of the first heat medium or the second heat medium. In this embodiment, the temperature sensor 9 includes a first temperature sensor 9a provided in the third flow path 5 through which the second heat medium that has passed through the heat collector 1 is supplied to the heat storage tank 2, a second temperature sensor 9b provided in the heat storage tank 2, and a third temperature sensor 9c provided in the first flow path 3 through which the first heat medium that has passed through the heat collector 1 is supplied to the heat storage tank 2.

[0036] The control unit 8 is configured to control the switching of the switching valve 7a based on the detection result of the temperature sensor 9. When the heat utilization unit 10 is operating, the second heat medium is initially configured to pass through the third flow path 5 and be heated by the heat collector 1. When the heat utilization unit 10 is operating and the detection result of the first temperature sensor 9a is less than the first threshold value and the detection result of the second temperature sensor 9b is equal to or greater than the second threshold value, the control unit 8 is configured to switch from the third flow path 5 to the second flow path 4 to heat the second heat medium in the heat storage tank 2. In this case, the pump 11 may be stopped when only heating the second heat medium is performed, and may be driven when heating the second heat medium and storing heat in the heat storage tank 2.

[0037] Furthermore, when the heat utilization unit 10 is operating, if the detection result of the first temperature sensor 9a is less than the first threshold value and the detection result of the second temperature sensor 9b is less than the second threshold value, the control unit 8 does not perform control to switch from the third flow path 5 to the second flow path 4. In this case, the pump 11 may be operating to store heat in the heat storage tank 2. Furthermore, if the detection result of the third temperature sensor 9c is less than a predetermined value, the control unit 8 is configured to switch from the third flow path 5 to the second flow path 4 to store heat in the heat storage tank 2. In this case, the pump 11 is operated. The first threshold value is a temperature at which the heat demand of the heat utilization unit 10 can be met. The second threshold value is a temperature at which the heat demand of the heat utilization unit 10 can be met. Note that the first threshold value and the second threshold value may be the same or different.

[0038] When the heat utilization unit 10 is not operating, the second heat medium flows through the second flow path 4 and is heated by the heat exchanger 6 of the heat storage tank 2. When the heat utilization unit 10 is not operating and the detection result of the third temperature sensor 9c is equal to or higher than the third threshold value, the control unit 8 is configured to switch from the third flow path 5 to the second flow path 4 to heat the second heat medium while heating the heat storage tank 2. In this case, the pump 11 is operating.

[0039] The heat utilization unit 10 is one of a vending machine, an item storage unit, an air conditioner, and a beverage brewing device. The heat utilization unit 10 is configured to heat or cool air using a heated second heat medium. The heat utilization unit 10 includes a refrigeration cycle that circulates the second heat medium. The refrigeration cycle is configured to circulate the second heat medium through an evaporator 42 in the ejector flow path, and to perform heat exchange between the second heat medium in the refrigeration cycle and the second heat medium in the ejector flow path. The refrigeration cycle has a heating / cooling unit 44 that heats or cools the air after passing through the evaporator 42 in the ejector flow path. The second heat medium that has circulated through the heating / cooling unit 44 is supplied to the ejector flow path and the refrigeration cycle, respectively.

[0040] 2, the control by the control unit 8 to switch the switching unit 7 based on the detection result of the temperature sensor 9 will be described. In step S1, the steps to be followed differ depending on whether or not there is a request for heat utilization from the heat utilization unit 10. Specifically, the steps to be followed differ depending on whether or not the refrigeration cycle of the heat utilization unit 10 is operating. If it is operating, the process proceeds to step S2, and if it is not operating, the process proceeds to step S8.

[0041] In step S2, the step to be followed differs depending on whether or not the first temperature sensor 9a detects a temperature equal to or greater than the first threshold. If the temperature is equal to or greater than the first threshold, the process proceeds to step S3, where the switching unit 7 is controlled to switch to the third flow path 5. In step S4, the step to be followed differs depending on whether or not the first temperature sensor 9a detects a temperature equal to or greater than the first threshold. If the first temperature sensor 9a detects a temperature equal to or greater than the first threshold, the process returns to step S1, and if the temperature is less than the first threshold, the control to switch the switching unit 7 ends. Note that step S3 is not performed if the second heat medium is flowing through the third flow path 5, and if the answer to step S2 is YES, the process proceeds to step S4.

[0042] If the temperature is less than the first threshold in step S2, the process proceeds to step S5. In step S5, the step to be followed differs depending on whether or not the second temperature sensor 9b detects a temperature equal to or greater than the second threshold. If the temperature is equal to or greater than the second threshold, the process proceeds to step S6 and switches to the second flow path 4, and if the temperature is less than the second threshold, the process returns to step S1. In step S7, the step to be followed differs depending on whether or not the second temperature sensor 9b detects a temperature equal to or greater than the second threshold. If the temperature sensor 9b detects a temperature equal to or greater than the second threshold, the process returns to step S1, and if the temperature is less than the second threshold, the control to switch the switching unit 7 is terminated.

[0043] In step S8, the step to be followed differs depending on whether or not the third temperature sensor 9c detects a temperature equal to or greater than the third threshold. If the temperature is equal to or greater than the third threshold, the process proceeds to step S9, where the process switches to the second flow path 4. In step S10, the step to be followed differs depending on whether or not the third temperature sensor 9c detects a temperature equal to or greater than the third threshold. If the third temperature sensor 9c detects a temperature equal to or greater than the third threshold, the process returns to step S1, and if the temperature is less than the third threshold, the control to switch the switching unit 7 is terminated.

[0044] (Preventing freezing of heat storage tank) The heat storage tank 2 is configured to suppress freezing by the second heat medium heated by the heat utilization unit 10. Specifically, the second heat medium flowing through the ejector flow path is heated by air heated by the refrigeration cycle, and the heated second heat medium is flowed to the heat exchanger 6. In the heat exchanger 6, the heat of the second heat medium heats the first heat medium in the heat storage tank 2, thereby suppressing freezing of the first heat medium and the heat storage tank 2. The second heat medium heated in the heat collector 1 or the heat storage tank 2 is switched by the flow path switching unit 45 so that it flows into a flow path heated by air heated in the heating / cooling unit 44 of the refrigeration cycle. The second heat medium heated by the heated air flows through the second flow path 4 and exchanges heat with the first heat medium in the heat storage tank 2 in the heat exchanger 6. As a result, the first heat medium in the heat storage tank 2 is heated, thereby suppressing freezing of the first heat medium and the heat storage tank 2.

[0045] (Example of heat utilization part) The heat utilization unit 10 includes a fan 12 that circulates the cooled air. The control unit 8 is configured to control the rotation speed of the fan 12 to be higher when the temperature inside the heat storage tank 2 is equal to or higher than a predetermined temperature than when the temperature inside the heat storage tank 2 is lower than the predetermined temperature. The control unit 8 may increase the rotation speed of the fan 12 and also control the temperature of the evaporator to be maintained at a predetermined value.

[0046] As shown in FIG. 3, for example, a case will be described in which the heat utilization unit 10 is a vending machine. In the case of a vending machine, a refrigerator 30 including at least a refrigeration cycle is disposed at the bottom of the cabinet. When cooling a product 50, heat is exchanged with a second heat medium in the heating / cooling unit 44 of the refrigerator 30, and the product 50 is cooled by the cooled interior air. At this time, the heating / cooling unit 44 functions as an evaporator. When heating a product 50, heat is exchanged with a second heat medium in the heating / cooling unit 44 of the refrigerator 30, and the product 50 is heated by the heated interior air. At this time, the heating / cooling unit functions as a condenser.

[0047] When cooling products 50 in a vending machine, if the temperature inside heat storage tank 2 is below a predetermined temperature, the rotation speed of fan 12 is reduced to primarily cool products 50 placed lower and secondarily cool products 50 placed higher. In this case, if the temperature inside heat storage tank 2 reaches or exceeds the predetermined temperature, control unit 8 controls fan 12 to rotate at a higher speed than when the temperature inside heat storage tank 2 is below the predetermined temperature, thereby cooling the entire interior of the vending machine. The predetermined temperature is set, for example, based on the pressure and boiling point of the first heat medium so as to be below the boiling point. In addition, the evaporation temperature of the evaporator (heating / cooling unit 44) of the refrigeration cycle of refrigerator 30 is adjusted to be low.

[0048] FIG. 4 shows another example in which the heat utilization unit 10 is a vending machine. The heat utilization unit 10 includes a cold storage material 13 disposed downstream of a fan 12. The control unit 8 is configured to control the rotation speed of the fan 12 so that the temperature of the air blown to the cold storage material 13 is equal to or lower than the freezing point of the cold storage material 13 when the temperature inside the heat storage tank 2 is equal to or higher than a predetermined temperature. When the temperature inside the heat storage tank 2 is lower than the predetermined temperature, the control unit 8 reduces the rotation speed of the fan 12 to adjust the temperature of the air blown to the cold storage material 13 to a temperature at which the cold storage material 13 does not freeze. As a result, the cold storage material 13 does not freeze and does not store cold. When the temperature inside the heat storage tank 2 is equal to or higher than the predetermined temperature, the control unit 8 controls the rotation speed of the fan 12 to increase and also controls the evaporation temperature in the evaporator (heating / cooling unit 44) to decrease, thereby adjusting the temperature of the air blown to the cold storage material 13 to a temperature at or lower than the freezing point of the cold storage material 13. This causes the cold storage material 13 to solidify and store cold, thereby converting the heat of the first heat medium into cold air and storing it. The cold storage material 13 is configured to be, for example, liquid or gel-like at room temperature, which is higher than the freezing point, and to be solid below the freezing point.

[0049] FIG. 5 shows an example in which the heat utilization unit 10 is an item storage unit (showcase). The item storage unit includes adjacent sales shelves 10a and storage shelves 10b. In the case of an item storage unit, products 50 on sales shelves 10a are cooled using air cooled by an evaporator (heating / cooling unit 44) of a refrigerator 30 that includes at least a refrigeration cycle. In this case, when the temperature inside the heat storage tank 2 is below a predetermined temperature, the fan 14a on sales shelves 10a is operated, and the fan 14b on storage shelves 10b is either rotated at a slower speed or stopped, thereby cooling the products 50 on sales shelves 10a but not the products 50 on storage shelves 10b. Furthermore, when the temperature inside the heat storage tank 2 reaches or exceeds the predetermined temperature, the control unit 8 controls the fan 14b on storage shelves 10b to rotate at a faster speed than when the temperature inside the heat storage tank 2 is below the predetermined temperature, and also lowers the evaporation temperature of the evaporator to cool the sales shelves 10a and storage shelves 10b. The predetermined temperature is set, for example, based on the pressure and boiling point of the first heat medium so as to be below the boiling point.

[0050] FIG. 6 shows a case where the heat utilization unit 10 is an air conditioner. An air conditioner cools or heats the room by cooling or heating air taken in from the outside using a heating / cooling unit 44 of a refrigerator 30 that includes at least a refrigeration cycle, and blowing the air out. When cooling the room, the heating / cooling unit 44 functions as an evaporator, and when heating the room, the heating / cooling unit 44 functions as a condenser. When the heat utilization unit 10 is an air conditioner, when the temperature inside the heat storage tank 2 reaches or exceeds a predetermined temperature, the control unit 8 controls the blown air to flow along the ceiling, thereby forming an airflow that blows down from the ceiling to the floor, thereby cooling the entire room. When the temperature inside the heat storage tank 2 falls below the predetermined temperature, the control unit 8 controls the blown air to flow down to the floor rather than along the ceiling, thereby cooling the room.

[0051] (Heat storage tank placement) As shown in FIG. 7, the heat storage tank 2 may be configured adjacent to either a storage unit that stores items to be heated using the second heat medium or a container that stores items to be heated using the second heat medium. In other words, while the heat collection unit 20 in FIG. 1 is composed of the heat collector 1 and the heat storage tank 2, in the example of FIG. 7, the heat collection unit 20 is composed of the heat collector 1, and the heat storage tank 2 is provided inside the heat utilization unit 10. As an example, the storage unit is a storage cabinet (hot cabinet) in which hot products 50 of a vending machine are stored, and the container is a hot water tank that stores hot water for a beverage production device. The storage cabinet in which hot products 50 of the vending machine are stored is configured to receive air heated using a heated second heat medium. The hot water tank is configured to store hot water heated using the second heat medium.

[0052] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0053] As described above, the first embodiment includes the second flow path 4, which heats the second heat medium using the heat of the first heat medium in the heat storage tank 2 and circulates the heated second heat medium to the heat utilization unit 10; the heat exchanger 6, which is provided at a portion of the second flow path 4 that passes through the heat storage tank 2 and performs heat exchange between the first heat medium and the second heat medium; the third flow path 5, which branches off from the second flow path 4 and does not pass through the heat exchanger 6, and through which the second heat medium heated by solar heat in the solar collector 1 circulates; and the switching unit 7, which switches the flow path through which the second heat medium circulates between the second flow path 4 and the third flow path 5. As a result, by switching to the third flow path 5 using the switching unit 7, the second heat medium can be directly heated in the solar collector 1, and sufficient heat can be efficiently supplied to the heat utilization unit 10 with little energy loss. Furthermore, by switching to the second flow path 4 using the switching unit 7, it is possible to store heat in the first heat medium in the heat storage tank 2 and heat the second heat medium using the heat of the first heat medium in the heat storage tank 2 during times when solar heat is available. Furthermore, by switching to the second flow path 4 using the switching unit 7, heat can be stored in the first heat medium in the heat storage tank 2 during the hours when solar heat can be used, and therefore sufficient heat can be supplied from the first heat medium in the heat storage tank 2 to the second heat medium during the night when solar heat cannot be used. As a result, heat can be supplied stably to the heat utilization unit 10.

[0054] Furthermore, in the first embodiment, as described above, the switching unit 7 includes the switching valve 7a that switches between the second flow path 4 and the third flow path 5, and further includes the control unit 8 that controls the switching of the switching valve 7a. As a result, by the control unit 8 switching the switching valve 7a, it is possible to easily switch between the second flow path 4 and the third flow path 5, and therefore it is possible to easily switch between a flow path that can stably supply heat to the second heat medium.

[0055] Furthermore, in the first embodiment, as described above, the system further includes a temperature sensor 9 that detects the temperature of at least one of the first heat medium or the second heat medium, and the control unit 8 is configured to control the switching of the switching valve 7a based on the detection result of the temperature sensor 9. As a result, the control unit 8 can switch between the second flow path 4 and the third flow path 5 based on the temperature of the first heat medium or the second heat medium, and therefore, when the temperature sensor 9 detects that the first heat medium is high, the control unit 8 can switch to the second flow path 4 so that heat is exchanged between the first heat medium and the second heat medium. Furthermore, when the temperature sensor 9 detects that the temperature of the second heat medium is low, the control unit 8 can switch to the flow path that can efficiently heat the second heat medium, between the second flow path 4 in which the second heat medium is heated by heat exchange with the first heat medium, and the third flow path 5 in which the second heat medium is directly heated by the heat collector 1, based on the temperature of the first heat medium detected by the temperature sensor 9.

[0056] Furthermore, in the first embodiment, as described above, the heat storage tank 2 is configured to suppress freezing by the second heat medium heated by the heat utilization unit 10. As a result, by suppressing freezing of the heat storage tank 2 by the second heat medium heated in the heat utilization unit 10, it is not necessary to change the first heat medium to an antifreeze liquid or to remove the first heat medium from the heat storage tank 2 in order to suppress freezing.

[0057] Furthermore, in the first embodiment, as described above, the heat utilization unit 10 cools the air by utilizing the heat of the second heat medium and includes the fan 12 that circulates the cooled air, and the control unit 8 is configured to control the rotation speed of the fan 12 to be higher when the temperature inside the heat storage tank 2 is equal to or higher than a predetermined temperature than when the temperature inside the heat storage tank 2 is below the predetermined temperature. As a result, as the rotation speed of the fan 12 is increased, the amount of cooling of the air in the heat utilization unit 10 also increases, and the amount of heat of the first heat medium supplied to the second heat medium increases. As a result, when the temperature inside the heat storage tank 2 is equal to or higher than the predetermined temperature, the heat inside the heat storage tank 2 can be efficiently utilized to lower the temperature inside the heat storage tank 2.

[0058] Furthermore, in the first embodiment, as described above, the heat utilization unit 10 includes the cold storage material 13 arranged downstream of the fan 12, and the control unit 8 is configured to control the rotation speed of the fan 12 when the temperature inside the heat storage tank 2 is equal to or higher than a predetermined temperature so that the temperature of the air blown to the cold storage material 13 is equal to or lower than the freezing point of the cold storage material 13. In this way, by increasing the rotation speed of the fan 12 so that the temperature is equal to or lower than the freezing point of the cold storage material 13, the cold storage material 13 can be solidified and cold stored, and therefore the energy inside the heat storage tank 2 can be used to cool the heat utilization unit 10.

[0059] Furthermore, in the first embodiment, as described above, the heat storage tank 2 is configured to be adjacent to either a storage unit that stores items to be heated using the second heat medium, or a container that stores items to be heated using the second heat medium. This allows the storage unit or container to be heated when heat leaks from the heat storage tank 2 to the outside, and therefore the storage unit or container can be efficiently heated by the second heat medium and the heat leaked from the heat storage tank 2. As a result, the heat leaked from the second heat medium and the heat from the heat storage tank 2 is used to heat the storage unit or container, thereby reducing energy loss.

[0060] In the first embodiment, as described above, the heat utilization unit 10 is one of a vending machine, an item storage unit, an air conditioner, and a beverage preparation device. This allows solar heat to be used for heating or cooling the vending machine, the item storage unit, the air conditioner, or the beverage preparation device.

[0061] [Second embodiment] Next, the configuration of a solar heat utilization system 200 according to a second embodiment of the present invention will be described with reference to Figures 8 and 9. In the second embodiment, unlike the first embodiment, the heat exchanger 206 includes a first heat exchanger 206a and a second heat exchanger 206b. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0062] 8, the heat exchanger 206 includes a first heat exchanger 206a and a second heat exchanger 206b. The first heat exchanger 206a is configured to exchange heat between the first heat medium in the heat storage tank 2 and the second heat medium flowing through the second flow path 4. The first heat exchanger 206a is disposed in the first heat medium stored in the heat storage tank 2, similar to the heat exchanger 6 of the first embodiment. The first heat exchanger 206a is disposed above the center of the heat storage tank 2. The second heat exchanger 206b is disposed in the second flow path 4, downstream of the first heat exchanger 206a in the heat storage tank 2. The second heat exchanger 206b is configured to exchange heat between the first heat medium flowing through the first flow path 3 and the second heat medium flowing through the second flow path 4.

[0063] 9, the second heat exchanger 206b is a double-pipe heat exchanger. The second heat exchanger 206b has the second flow path 4 disposed inside and the first flow path 3 disposed outside. In other words, the first flow path 3 covers the outer periphery of the second flow path 4. As a result, even if a portion of the heat of the first heat medium leaks when the heat is transferred from the first heat medium circulating through the first flow path 3 to the second heat medium circulating through the second flow path 4, the heat leaks into the heat storage tank 2, and the heat is stored in the heat storage tank 2, thereby reducing heat loss.

[0064] The second heat exchanger 206b is configured to further heat the second heat medium heated by the first heat exchanger 206a. In particular, when the temperature of the first heat medium stored in the heat storage tank 2 is low and lower than the temperature of the first heat medium heated by the heat collector 1, heat exchange by the second heat exchanger 206b can be performed with the first heat medium with a higher temperature heated by the heat collector 1, thereby efficiently heating the second heat medium. In this case, step S5 of FIG. 2 is configured to switch to the second flow path 4 regardless of whether the second temperature sensor 9b is equal to or greater than the second threshold. Even when the temperature is less than the second threshold, switching to the second flow path 4 allows heating by the second heat exchanger 206b, so the second heat medium can be sufficiently heated.

[0065] The other configurations of the second embodiment are the same as those of the first embodiment.

[0066] (Effects of the second embodiment) As described above, the second embodiment includes the second flow path 4, which heats the second heat medium using the heat of the first heat medium in the heat storage tank 2 and circulates the heated second heat medium to the heat utilization unit 10; the heat exchanger 6, which is provided at a portion of the second flow path 4 that passes through the heat storage tank 2 and performs heat exchange between the first heat medium and the second heat medium; the third flow path 5, which branches off from the second flow path 4 and does not pass through the heat exchanger 6, and through which the second heat medium heated by solar heat in the solar collector 1 circulates; and the switching unit 7, which switches the flow path through which the second heat medium circulates between the second flow path 4 and the third flow path 5. As a result, by switching to the third flow path 5 using the switching unit 7, the second heat medium can be directly heated in the solar collector 1, and sufficient heat can be efficiently supplied to the heat utilization unit 10 with little energy loss. Furthermore, by switching to the second flow path 4 using the switching unit 7, it is possible to store heat in the first heat medium in the thermal storage tank 2 and heat the second heat medium using the heat of the first heat medium in the thermal storage tank 2 during times when solar heat is available. Furthermore, by switching to the second flow path 4 using the switching unit 7, heat can be stored in the first heat medium in the heat storage tank 2 during the hours when solar heat can be used, and therefore sufficient heat can be supplied from the first heat medium in the heat storage tank 2 to the second heat medium during the night when solar heat cannot be used. As a result, heat can be supplied stably to the heat utilization unit 10.

[0067] In the second embodiment, as described above, the heat exchanger 206 includes the first heat exchanger 206a, which is disposed in the heat storage tank 2 and performs heat exchange between the first heat medium in the heat storage tank 2 and the second heat medium flowing through the second flow path 4, and the second heat exchanger 206b, which is disposed downstream of the first heat exchanger 206a in the heat storage tank 2 and performs heat exchange between the first heat medium flowing through the first flow path 3 and the second heat medium flowing through the second flow path 4. With this, the first heat exchanger 206a and the second heat exchanger 206b can heat the second heat medium with the first heat medium in the heat storage tank 2, and then heat the second heat medium with the first heat medium that has a higher temperature than the first heat medium in the heat storage tank 2 that has been heated by the heat collector 1. As a result, even when the temperature of the first heat medium in the heat storage tank 2 is low, the second heat medium can be sufficiently heated by heating the second heat medium with the first heat medium that has a higher temperature than the first heat medium in the heat storage tank 2 that has been heated by the heat collector 1. Furthermore, since the heat exchanger 206 is disposed inside the heat storage tank 2, even if the heat of the first heat medium leaks out of the heat exchanger 206, the heat is stored in the first heat medium inside the heat storage tank 2. As a result, energy loss can be suppressed.

[0068] In the second embodiment, as described above, the second heat exchanger 206b is a double-pipe heat exchanger in which the second flow path 4 is arranged on the inside and the first flow path 3 is arranged on the outside. As a result, by arranging the second flow path 4 on the inside, when heat is imparted from the first heat medium to the second heat medium circulating inside the second heat exchanger 206b, it is possible to prevent the heat imparted to the second heat medium from leaking outside the second heat exchanger 206b, and therefore it is possible to suppress energy loss.

[0069] The other effects of the second embodiment are the same as those of the first embodiment.

[0070] [Third embodiment] Next, the configuration of a solar heat utilization system 300 according to a third embodiment of the present invention will be described with reference to Fig. 10. In the third embodiment, unlike the first embodiment, the first flow path 3 is provided with a plurality of inlets leading to the heat storage tank 2 and a plurality of outlets leading from the heat storage tank 2. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0071] As shown in FIG. 10 , the first flow path 3 includes an inlet-side flow path 3a, an outlet-side flow path 3b, an inlet-side flow path switching unit 3c, and an outlet-side flow path switching unit 3d. The inlet-side flow path 3a is configured to supply the first heat medium from the heat collector 1 to the heat storage tank 2 via either an upper inlet 3e located above the vertical center of the heat storage tank 2 or a lower inlet 3f located below the vertical center of the heat storage tank 2. The outlet-side flow path 3b is configured to supply the first heat medium from the heat storage tank 2 to the heat collector 1 via either an upper outlet 3g located above the vertical center of the heat storage tank 2 or a lower outlet 3h located below the vertical center of the heat storage tank 2. The inlet-side flow path switching unit 3c is configured to switch between the upper inlet 3e and the lower inlet 3f. The outlet-side flow path switching unit 3d is configured to switch between the upper outlet 3g and the lower outlet 3h.

[0072] In the initial state, the control unit 8 switches between the inlet side flow path switching unit 3c and the outlet side flow path switching unit 3d so that the first heat medium flows into the heat storage tank 2 through the upper inlet 3e and flows from the heat storage tank 2 to the heat collector 1 through the lower outlet 3h.

[0073] A case where the load required by the heat utilization unit 10 is small will be described. A case where the load required by the heat utilization unit 10 is small includes a case where the operation of the heat utilization unit 10 is stopped and a case where the difference between the external temperature and the set temperature of the heat utilization unit 10 is small and the operation of the heat utilization unit 10 is low. In this case, the heat of the first heat medium stored in the heat storage tank 2 is not utilized very much. Therefore, the control unit 8 switches the inlet-side flow path switching unit 3c from the initial state to cause the first heat medium to flow into the heat storage tank 2 through the lower inlet 3f and to flow from the heat storage tank 2 to the solar collector 1 through the lower outlet 3h. This heat medium is heated in the lower part, where the temperature of the first heat medium is lower than in the upper part where the heat exchanger 6 is provided. Therefore, the heat of the first heat medium is not utilized very much. This prevents the heat from accumulating in the heat storage tank 2 and boiling of the upper first heat medium. It also prevents the heat from leaking due to insufficient heat storage.

[0074] The case where the amount of solar radiation is small will be described. In this case, the amount of heat heated by the first heat medium by the solar collector 1 decreases. Therefore, the control unit 8 switches the outlet-side flow path switching unit 3d to cause the first heat medium to flow into the solar collector 1 via the upper outlet 3g while maintaining the initial state in which the first heat medium flows into the solar storage tank 2 from the upper inlet 3e. As a result, the upper first heat medium, which has a higher temperature than the lower first heat medium in the solar storage tank 2, is heated by the solar collector 1. This makes it possible to increase the temperature of the first heat medium supplied from the solar collector 1 to the solar storage tank 2 compared to heating the lower first heat medium, which has a lower temperature. Furthermore, the high-temperature first heat medium heats the higher-temperature first heat medium above the solar storage tank 2, further increasing the temperature of the upper first heat medium. By repeating this process, the first heat medium can be efficiently heated, and the second heat medium can be sufficiently heated using the first heat medium.

[0075] The control unit 8 is configured to perform control to switch between the inlet-side flow path switching unit 3c and the outlet-side flow path switching unit 3d based on the temperature of the heat storage tank 2. Specifically, the control unit 8 is configured to perform control to switch between the inlet-side flow path switching unit 3c and the outlet-side flow path switching unit 3d based on the temperature of the heat storage tank 2 detected by a second temperature sensor 9b provided at least in one of the upper, lower, and center portions of the heat storage tank 2. As an example, a case will be described in which the second temperature sensors 9b are provided above and below the heat storage tank 2. In this case, when the temperature in the upper portion is close to the boiling point, the control unit 8 controls the inlet-side flow path switching unit 3c to switch to the lower inlet 3f. As a result, the first heat medium heated in the solar collector 1 flows downward, where the temperature is lower, and therefore, it is possible to prevent the first heat medium in the upper portion from being heated and boiling. In addition, when the temperature difference between the upper and lower temperatures is large, the inlet-side flow path switching unit 3c is controlled to supply the first heat medium to the heat storage tank 2 from the lower inlet 3f so as to heat the lower heat medium, and the outlet-side flow path switching unit 3d is controlled to supply the first heat medium to the heat collector 1 from the lower outlet 3h.

[0076] The other configurations of the third embodiment are the same as those of the first embodiment.

[0077] (Effects of the third embodiment) As described above, the third embodiment includes the second flow path 4, which heats the second heat medium using the heat of the first heat medium in the heat storage tank 2 and circulates the heated second heat medium to the heat utilization unit 10; the heat exchanger 6, which is provided at a portion of the second flow path 4 that passes through the heat storage tank 2 and performs heat exchange between the first heat medium and the second heat medium; the third flow path 5, which branches off from the second flow path 4 and does not pass through the heat exchanger 6, and through which the second heat medium heated by solar heat in the solar collector 1 circulates; and the switching unit 7, which switches the flow path through which the second heat medium circulates between the second flow path 4 and the third flow path 5. By switching to the third flow path 5 using the switching unit 7, the second heat medium can be directly heated in the solar collector 1, and sufficient heat can be efficiently supplied to the heat utilization unit 10 with little energy loss. Furthermore, by switching to the second flow path 4 using the switching unit 7, the second heat medium can be heated using the heat of the first heat medium in the solar storage tank 2 while heat is stored in the first heat medium in the solar storage tank 2 during times when solar heat is available. Furthermore, by switching to the second flow path 4 using the switching unit 7, heat can be stored in the first heat medium in the heat storage tank 2 during the hours when solar heat can be used, and therefore sufficient heat can be supplied from the first heat medium in the heat storage tank 2 to the second heat medium during the night when solar heat cannot be used. As a result, heat can be supplied stably to the heat utilization unit 10.

[0078] In the third embodiment, as described above, the first flow path 3 includes an inlet-side flow path 3a that supplies the first heat medium from the heat collector 1 to the heat storage tank 2 via either an upper inlet 3e located above the vertical center of the heat storage tank 2 or a lower inlet 3f located below the vertical center of the heat storage tank 2, an outlet-side flow path 3b that supplies the first heat medium from the heat collector 1 to the heat storage tank 2 via either an upper outlet 3g located above the vertical center of the heat storage tank 2 or a lower outlet 3h located below the vertical center of the heat storage tank 2, an inlet-side flow path switching unit 3c that switches between the upper inlet 3e and the lower inlet 3f, and an outlet-side flow path switching unit 3d that switches between the upper outlet 3g and the lower outlet 3h. As a result, by switching the inlet-side flow path 3a from the upper inlet 3e to the lower inlet 3f by the inlet-side flow path switching unit 3c, when a first heat medium with a relatively low temperature is stored below the heat storage tank 2, the first heat medium heated in the heat collector 1 can be supplied to the first heat medium with a relatively low temperature stored below, thereby heating the first heat medium stored below. Also, by switching the outlet-side flow path 3b from the upper outlet 3g to the lower outlet 3h by the outlet-side flow path switching unit 3d, the first heat medium with a relatively low temperature stored below can be supplied to the heat collector 1 and heated.

[0079] As described above, the third embodiment further includes a control unit 8 that switches between the inlet-side flow path switching unit 3c and the outlet-side flow path switching unit 3d based on the temperature of the heat storage tank 2. As a result, when the temperature in the upper part of the heat storage tank 2 is high, the inlet-side flow path switching unit 3c switches the inlet-side flow path 3a from the upper inlet 3e to the lower inlet 3f, so that the first heat medium heated in the heat collector 1 can be supplied to the lower first heat medium having a relatively low temperature. Furthermore, when the temperature in the lower part of the heat storage tank 2 is low, the outlet-side flow path switching unit 3d switches the outlet-side flow path 3b from the upper outlet 3g to the lower outlet 3h, so that the lower first heat medium having a relatively low temperature can be heated in the heat collector 1.

[0080] The other effects of the third embodiment are the same as those of the first embodiment.

[0081] [Fourth embodiment] Next, the configuration of a solar heat utilization system 400 according to a fourth embodiment of the present invention will be described with reference to Figures 11 and 12. Unlike the first embodiment, the fourth embodiment includes a bypass flow path 16. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0082] As shown in FIG. 11 , the first flow path 3 further includes a bypass flow path 16 that branches off from the first flow path 3 and bypasses the pump 11. The bypass flow path 16 is provided with a relief valve 17 that opens in response to the pressure of the first heat medium in the heat storage tank 2. When the pump 11 stops, the bypass flow path 16 opens in response to the pressure of the first heat medium in the heat storage tank 2, thereby forcing the first heat medium below the heat storage tank 2 to flow through the first flow path 3 to the heat collector 1 by the pressure of the first heat medium itself. The forced flow of the first heat medium is heated in the heat collector 1 and returns to the heat storage tank 2. The relief valve 17 opens, for example, when the temperature of the first heat medium stored above the heat storage tank 2 approaches its boiling point and the pressure inside the heat storage tank 2 exceeds a predetermined value. After opening, the relief valve 17 returns to a closed state when the pressure inside the heat storage tank 2 falls below a predetermined value.

[0083] The first heat medium flowing through the bypass flow path 16 is configured to return to the first flow path 3. The first heat medium flowing through the first flow path 3 is configured to flow through the heat collector 1 and then into the heat storage tank 2. The first heat medium flowing through the bypass flow path 16 has a lower temperature than the first heat medium stored above the heat storage tank 2, and is heated by the heat collector 1 before returning to the heat storage tank 2. The first heat medium returned to the heat storage tank 2 has a lower temperature than the first heat medium stored above the heat storage tank 2, and cools the first heat medium stored above the heat storage tank 2. As a result, the temperature of the first heat medium stored above the heat storage tank 2 decreases, and the pressure inside the heat storage tank 2 decreases. As a result, when the pressure inside the heat storage tank 2 falls below a predetermined value, the relief valve 17 returns to its closed state.

[0084] As shown in FIG. 12 , the bypass flow path 16 may be provided separately from the first flow path 3. In this case, it is preferable that the flow in the first flow path 3 in the solar collector 1 is from the low-temperature side to the high-temperature side, while the bypass flow path 16 is configured to form an opposing flow from the high-temperature side to the low-temperature side. In FIG. 12 , the first heat medium flowing in the first flow path 3 is heated by flowing from the low-temperature side to the high-temperature side, while the first heat medium flowing in the bypass flow path 16 is cooled by flowing from the high-temperature side to the low-temperature side. The first heat medium with a lowered temperature flows above the thermal storage tank 2, thereby cooling the relatively high-temperature first heat medium located above the thermal storage tank 2. This reduces the pressure of the first heat medium in the thermal storage tank 2. Then, when the pressure inside the thermal storage tank 2 falls below a predetermined value, the relief valve 17 returns to its closed state.

[0085] The other configurations of the fourth embodiment are the same as those of the first embodiment.

[0086] (Effects of the fourth embodiment) As described above, the fourth embodiment includes the second flow path 4, which heats the second heat medium using the heat of the first heat medium in the heat storage tank 2 and circulates the heated second heat medium to the heat utilization unit 10; the heat exchanger 6, which is provided at a portion of the second flow path 4 that passes through the heat storage tank 2 and performs heat exchange between the first heat medium and the second heat medium; the third flow path 5, which branches off from the second flow path 4 and does not pass through the heat exchanger 6, and through which the second heat medium heated by solar heat in the solar collector 1 circulates; and the switching unit 7, which switches the flow path through which the second heat medium circulates between the second flow path 4 and the third flow path 5. By switching to the third flow path 5 using the switching unit 7, the second heat medium can be directly heated in the solar collector 1, and sufficient heat can be efficiently supplied to the heat utilization unit 10 with little energy loss. Furthermore, by switching to the second flow path 4 using the switching unit 7, the second heat medium can be heated using the heat of the first heat medium in the solar storage tank 2 while heat is stored in the first heat medium in the solar storage tank 2 during a time period when solar heat is available. Furthermore, by switching to the second flow path 4 using the switching unit 7, heat can be stored in the first heat medium in the heat storage tank 2 during the hours when solar heat can be used, and therefore sufficient heat can be supplied from the first heat medium in the heat storage tank 2 to the second heat medium during the night when solar heat cannot be used. As a result, heat can be supplied stably to the heat utilization unit 10.

[0087] In the fourth embodiment, as described above, the first flow path 3 includes the pump 11 and further includes a bypass flow path 16 that branches off from the first flow path 3 and bypasses the pump 11, and the bypass flow path 16 is provided with a relief valve 17 that opens depending on the pressure of the first heat medium in the heat storage tank 2. As a result, for example, when the pressure in the heat storage tank 2 increases after the pump 11 stops, the relief valve 17 opens, and the pressure can be used to press the first heat medium from the heat storage tank 2 to the heat collector 1, so that the first heat medium can be circulated. As a result, even when the pump 11 stops, the first heat medium circulates, so that the temperature of the first heat medium can be lowered, and the pressure in the heat storage tank 2 can be lowered.

[0088] The other effects of the fourth embodiment are the same as those of the first embodiment.

[0089] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0090] For example, in the first to fourth embodiments, the heat utilization unit includes a refrigeration cycle, but the present invention is not limited to this. In the present invention, the heat utilization unit does not have to include a refrigeration cycle. In this case, the object may be cooled or heated by the ejector flow path.

[0091] In the first to fourth embodiments, the temperature sensor is configured to detect the temperature of the first heat medium and the temperature of the second heat medium, but the present invention is not limited to this. In the present invention, the temperature sensor may be configured to detect either the temperature of the first heat medium or the temperature of the second heat medium. In this case, the second temperature sensor and either the first temperature sensor or the third temperature sensor are provided.

[0092] In addition, in the first to fourth embodiments, the temperature sensor includes both the first temperature sensor and the third temperature sensor, but the present invention is not limited to this. In the present invention, the temperature sensor may include either the first temperature sensor or the third temperature sensor.

[0093] In the first to fourth embodiments, the heat storage tank is configured to suppress freezing by the second heat medium heated by the heat utilization unit, but the present invention is not limited to this. In the present invention, the heat storage tank may be suppressed from freezing by a heat source other than the second heat medium heated by the heat utilization unit, such as a heater.

[0094] In the first to fourth embodiments, the control unit is configured to control the fan to have a higher rotation speed when the temperature inside the heat storage tank is equal to or higher than a predetermined temperature, compared to when the temperature inside the heat storage tank is below the predetermined temperature. However, the present invention is not limited to this. In the present invention, the control unit does not have to control the fan to have a higher rotation speed.

[0095] In the second embodiment, the second heat exchanger is a double-pipe heat exchanger, but the present invention is not limited to this. In the present invention, the second heat exchanger may be a heat exchanger other than a double-pipe heat exchanger, and as an example, may be a heat exchanger in which the first flow path and the second flow path are arranged side by side.

[0096] In the third embodiment, the temperature sensors are disposed above and below the heat storage tank, but the present invention is not limited to this. In the present invention, the temperature sensor may be disposed at the center of the heat storage tank. In this case, the temperature sensor may be disposed above or below the heat storage tank, or may not be disposed above or below the heat storage tank. Furthermore, the control unit may switch between the inlet-side flow path switching unit and the outlet-side flow path switching unit based on the detection result of the first temperature sensor. For example, the first heat medium may be supplied to the heat storage tank from the lower inlet when the temperature of the first heat medium in the inlet-side flow path detected by the first temperature sensor is higher than a threshold value.

[0097] Furthermore, although the second to fourth embodiments are described as independent embodiments, the present invention is not limited to these. The present invention may also be configured by combining at least two of the second to fourth embodiments and their modifications. [Explanation of symbols]

[0098] 1 Heat collector 2 Heat storage tank 3 First flow path 3a Inlet side flow path 3b Outlet side flow path 3c Inlet flow path switching section 3d Outlet side flow path switching section 3e Upper entrance 3f lower entrance 3g upper exit 3h lower exit 4 Second flow path 5 Third Flow Path 6, 206 heat exchanger 7 Switching section 7a Switching valve 8 Control Unit 9 Temperature Sensor 10 Heat utilization section 11 Pump 12 Fans 13 Cold storage material 16 Bypass flow path 17 Relief valve 45 Flow path switching section 100, 200, 300, 400 Solar thermal utilization system 206a 1st heat exchanger 206b 2nd heat exchanger

Claims

1. a heat collector that collects solar heat and heats a first heat medium; a heat storage tank that stores the first heat medium heated in the heat collector; a first flow path connecting the heat collector and the heat storage tank; a second flow path that heats a second heat medium by utilizing heat of the first heat medium in the heat storage tank and circulates the heated second heat medium through a heat utilization unit; a heat exchanger provided in a portion of the second flow path passing through the heat storage tank, the heat exchanger performing heat exchange between the first heat medium and the second heat medium; a third flow path that branches off from the second flow path, does not pass through the heat exchanger, and through which the second heat medium heated by solar heat in the heat collector flows; A solar thermal utilization system comprising: a switching unit that switches a flow path through which the second heat medium flows between the second flow path and the third flow path.

2. the switching unit includes a switching valve that switches between the second flow path and the third flow path, The solar heat utilization system according to claim 1 , further comprising a control unit that controls switching of the switching valve.

3. Further provided is a temperature sensor that detects the temperature of at least one of the first heat medium or the second heat medium; The solar heat utilization system according to claim 2 , wherein the control unit is configured to control switching of the switching valve based on a detection result of the temperature sensor.

4. 2. The solar thermal utilization system according to claim 1, wherein the heat exchanger includes a first heat exchanger disposed within the heat storage tank, in which heat exchange occurs between the first heat medium in the heat storage tank and the second heat medium flowing through the second flow path, and a second heat exchanger disposed downstream of the first heat exchanger within the heat storage tank, in which heat exchange occurs between the first heat medium flowing through the first flow path and the second heat medium flowing through the second flow path.

5. 5. The solar thermal utilization system according to claim 4, wherein the second heat exchanger is a double-pipe heat exchanger in which the second flow path is arranged on the inside and the first flow path is arranged on the outside.

6. 2. The solar thermal utilization system according to claim 1, wherein the first flow path includes: an inlet-side flow path that supplies the first heat medium from the heat collector to the heat storage tank via either an upper inlet located above the vertical center of the heat storage tank or a lower inlet located below the vertical center of the heat storage tank; an outlet-side flow path that supplies the first heat medium from the heat collector to the heat storage tank via either an upper outlet located above the vertical center of the heat storage tank or a lower outlet located below the vertical center of the heat storage tank; an inlet-side flow path switching unit that switches between the upper inlet and the lower inlet; and an outlet-side flow path switching unit that switches between the upper outlet and the lower outlet.

7. The solar heat utilization system according to claim 6 , further comprising a control unit that switches between the inlet-side flow path switching unit and the outlet-side flow path switching unit based on a temperature of the heat storage tank.

8. the first flow path includes a pump; a bypass flow path branching from the first flow path and bypassing the pump; The solar thermal utilization system according to claim 1 , wherein the bypass flow path is provided with a relief valve that opens in response to the pressure of the first heat medium in the heat storage tank.

9. The solar thermal utilization system according to claim 1 , wherein the heat storage tank is configured to suppress freezing by the second heat medium heated by the heat utilization unit.

10. the heat utilization unit uses heat of the second heat medium to cool air and includes a fan that circulates the cooled air; 3. The solar thermal utilization system according to claim 2, wherein the control unit is configured to control the rotation speed of the fan to be higher when the temperature inside the heat storage tank is equal to or higher than a predetermined temperature than when the temperature inside the heat storage tank is lower than the predetermined temperature.

11. the heat utilization unit includes a cold storage material disposed downstream of the fan, The solar thermal utilization system of claim 10, wherein the control unit is configured to control the rotation speed of the fan so that the temperature of the air blown to the heat storage material is equal to or lower than the freezing point of the heat storage material when the temperature inside the heat storage tank is equal to or higher than the predetermined temperature.

12. 2. The solar thermal utilization system of claim 1, wherein the heat storage tank is configured to be adjacent to either a storage section in which items to be heated using the second heat medium are stored, or a container in which the items to be heated using the second heat medium are stored.

13. The solar heat utilization system according to claim 1 , wherein the heat utilization unit is one of a vending machine, an article storage unit, an air conditioner, and a beverage preparation device.

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