Thermal storage system

Abstract

To provide a heat storage system that efficiently stores, in a heat storage tank, heat collected by a heat collection device.SOLUTION: A heat storage system 1 comprises: a heat collection device 10 that collects heat generated by a heat source with a collectible heat quantity varied and supplies the heat to a heat medium TM1; a heat storage tank 20 with a heat storage material 26 undergoing a phase change between solid and liquid, that facilitates heat exchange between a heat medium TM2 to which the heat is directly or indirectly supplied from the heat collection device 10, and the heat storage material 26; conveyance mechanisms 41 and 43 to 48 for conveying the heat media TM1 and TM2 from the heat collection device 10 to the heat storage tank 20; and a control device 80 for controlling the conveyance mechanisms 45 and 48 such that the heat medium TM2 retaining the heat supplied from the heat collection device 10, when flowing into the heat storage tank 20, reaches a first predetermined temperature that is a melting point or higher of the heat storage material 26.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a heat storage system, and more particularly to a heat storage system that stores heat extracted from a heat source whose extractable heat amount varies in a latent heat storage material. [Background technology]

[0002] As the effects of global warming become more pronounced, attempts are being made to increase the proportion of fossil fuels substituted with renewable energy, which contributes to reducing carbon dioxide emissions that cause global warming. Systems that utilize solar heat, one type of renewable energy, have been put into practical use, in which solar thermal energy is collected in a solar collector and used for hot water supply and heating / cooling. One example of this system is one that includes a solar collector that collects heat generated by irradiation with sunlight and a heat storage tank that stores the solar heat collected by the collector, and circulates a heat medium (e.g., water) between them to store the heat (see, for example, Patent Document 1).

[0003] The system described in Patent Document 1 stores heat in a heat storage tank using a heat medium (e.g., water) that can be circulated by a pump, so the heat storage density is low and the heat storage tank must be large to obtain a relatively large heat storage capacity.On the other hand, as a heat storage tank with a high heat storage density, there is a latent heat storage device that uses a phase change material (PCM) as the heat storage material and stores heat by utilizing the latent heat generated when the heat storage material transforms into a solid-liquid phase (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-166783 [Patent Document 2] Patent No. 6630946 Summary of the Invention [Problem to be solved by the invention]

[0005] If the latent heat storage device disclosed in Patent Document 2 could be applied to a solar heat collection system, it would be possible to achieve a system capable of storing collected solar heat at a high density, which would be ideal. However, the amount of solar radiation fluctuates greatly with changes in weather. If the amount of solar radiation decreases during heat storage, the temperature of the heat medium drops, and a low-temperature heat medium flows into the heat storage tank, heat is transferred (heat dissipated) from the heat storage material to the heat medium, and the heat storage material drops below its melting point, changing from a liquid phase to a solid phase, thereby reducing the heat storage efficiency. As such, simply replacing the heat storage tank in a conventional solar heat collection system with a latent heat storage device makes it difficult to achieve stable heat storage.

[0006] In view of the above-mentioned problems, the present disclosure relates to providing a heat storage system that can efficiently store heat collected by a heat collection device in a heat storage tank. [Means for solving the problem]

[0007] A heat storage system according to a first aspect of the present disclosure includes a heat extraction device that extracts heat generated from a heat source whose extractable heat quantity varies and supplies the extracted heat to a heat medium; a heat storage tank that has a heat storage material that undergoes a phase change between solid and liquid and performs heat exchange between the heat medium supplied directly or indirectly from the heat extraction device and the heat storage material; a transport mechanism that transports the heat medium from the heat extraction device to the heat storage tank; and a control device that controls the transport mechanism so that the heat medium, which holds the heat supplied from the heat extraction device, reaches a first predetermined temperature that is equal to or higher than the melting point of the heat storage material when it flows into the heat storage tank.

[0008] By configuring it in this manner, it is possible to prevent a relatively low-temperature heat medium from flowing into the heat storage tank during heat storage, thereby preventing the heat storage material that has once been liquefied from solidifying, and allowing the heat collected by the heat collection equipment to be efficiently stored in the heat storage tank.

[0009] Furthermore, a heat storage system according to a second aspect of the present disclosure is the heat storage system according to the first aspect of the present disclosure, further comprising a supply mechanism that directly or indirectly supplies the heat medium, which holds the heat released from the heat storage tank, to a heat utilization device that utilizes the heat stored in the heat storage tank, wherein the heat storage tank comprises a heat transfer cylinder through which the heat medium flows, an outer cylinder arranged around the heat transfer cylinder with a predetermined space therebetween and holding the heat storage material in the space between the outer surface of the heat transfer cylinder and the inner surface of the outer cylinder, blades that are close to or in sliding contact with the outer surface of the heat transfer cylinder, and a moving mechanism that moves the heat transfer cylinder relative to the blades, and the control device controls at least one of the supply mechanism and the moving mechanism so that the heat medium exiting the heat storage tank towards the heat utilization device reaches a second predetermined temperature.

[0010] With this configuration, a stable amount of heat can be supplied to the heat-utilization device from the heat storage tank that stores heat extracted from a heat source whose extractable amount of heat varies.

[0011] Furthermore, a heat storage system according to a third aspect of the present disclosure is the heat storage system according to the second aspect of the present disclosure, wherein the heat storage tank has a first temperature detector arranged at a position among the heat storage materials held in the space where the change of the heat storage material from solid to liquid is finalized when the heat storage material receives heat from the heat medium, and the control device controls the conveying mechanism to stop the flow of the heat medium holding the heat supplied from the heat collection equipment into the heat storage tank when the temperature detected by the first temperature detector reaches a third predetermined temperature that is higher than or equal to the melting point of the heat storage material.

[0012] With this configuration, it can be assumed that the heat storage tank is fully charged when the temperature detector detects the third predetermined temperature, and further inflow of heat into the heat storage tank can be prevented.

[0013] Furthermore, a heat storage system according to a fourth aspect of the present disclosure is a heat storage system according to any one of the first to third aspects of the present disclosure, wherein the heat collection device is a solar heat collector that collects solar heat, and the heat storage system further includes a solar radiation-related physical quantity measuring instrument that detects a physical quantity that changes in real time following changes in the amount of solar radiation, and the control device controls the transport mechanism based on the value detected by the solar radiation-related physical quantity measuring instrument.

[0014] With this configuration, when the amount of solar radiation changes, the change can be reflected in the control without delay, and it is possible to prevent the heat medium having a temperature below the first predetermined temperature from flowing into the heat storage tank.

[0015] Furthermore, a heat storage system according to a fifth aspect of the present disclosure is a heat storage system according to any one of the first to third aspects of the present disclosure, which is provided with a second temperature detector that detects the temperature of the heat medium at the outlet of the heat collection device, and the control device controls the conveying mechanism based on the value detected by the second temperature detector.

[0016] With this configuration, it is possible to maintain the temperature of the heat medium flowing out from the heat extracting device at a desired temperature with a relatively simple configuration.

[0017] Furthermore, a heat storage system according to a sixth aspect of the present disclosure is a heat storage system according to any one of the first to fifth aspects of the present disclosure, wherein the heat storage tank includes a first heat storage tank and a second heat storage tank separate from the first heat storage tank.

[0018] With this configuration, the number of operating heat storage tanks can be adjusted according to the amount of heat required by the heat utilization device.

[0019] Furthermore, a heat storage system according to a seventh aspect of the present disclosure is the heat storage system according to the sixth aspect of the present disclosure, wherein the heat storage material in the first heat storage tank is a first heat storage material, and the heat storage material in the second heat storage tank is a second heat storage material having a melting point different from that of the first heat storage material.

[0020] This configuration allows the heat storage tank to be used preferentially depending on the amount of heat that can be extracted by the heat extraction equipment, improving heat storage efficiency. Also, it allows the heat medium to be supplied at an appropriate temperature to different heat utilization devices that require different heat medium temperatures. [Effects of the Invention]

[0021] According to the present disclosure, it is possible to prevent a heat medium with a relatively low temperature from flowing into the heat storage tank during heat storage, thereby preventing the heat storage material that has once been liquefied from solidifying, and allowing the heat collected by the heat collection equipment to be efficiently stored in the heat storage tank. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic system diagram of a heat storage system according to an embodiment. [Figure 2] 1A is a vertical cross-sectional view of a heat storage tank included in a heat storage system according to one embodiment, and FIG. 1B is a horizontal cross-sectional view of the heat storage tank. [Figure 3] FIG. 3 is a table showing the relationship between the operating state of the heat storage system according to one embodiment and the states of each valve, each pump, and the like. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, identical or similar reference numerals are used to designate identical or corresponding components, and redundant explanations will be omitted.

[0024] First, a heat storage system 1 according to one embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic system diagram of the heat storage system 1. The heat storage system 1 mainly comprises a solar heat collector 10 (hereinafter simply referred to as "heat collector 10") that collects solar heat, a heat storage tank 20, various piping and conveying devices that transport the heat collected by the heat collector 10 to the heat storage tank 20 via a fluid, and a control device 80. In this embodiment, the system further comprises various piping and conveying devices that supply the heat stored in the heat storage tank 20 to a heat utilization device 91 via a fluid.

[0025] The solar collector 10 is a device that supplies collected solar heat to the heat medium TM1. Solar heat is a heat source whose extractable heat amount varies depending on the location where the solar collector 10 is installed, such as the position of the sun during the day and night and the weather. Here, a "heat source with a variable extractable heat amount" typically refers to a heat source whose maximum extractable heat amount increases or decreases over time, contrary to the system user's intention (changes regardless of the system user's intention). In this respect, solar heat differs from heat sources such as boilers, whose maximum extractable heat amount is determined based on a rated value specific to the device (the maximum extractable heat amount does not change) and whose extractable heat amount can be determined by the system user within that range. The solar heat collector 10 corresponds to a heat extracting device. Various known devices can be used as the solar heat collector 10, but it is preferable to use a vacuum tube solar collector, which has excellent heat collection efficiency and a small heat collection area. In an evacuated tube solar collector, the solar heat is usually transferred to a heat medium TM1 by passing the heat medium TM1 through the heat collecting section inside the glass tube. Various fluids such as water, antifreeze, and oil-based fluids can be used as the heat medium TM1, but in this embodiment, antifreeze is used because the solar collector 10 is typically installed outdoors.

[0026] In this embodiment, a heat extraction heat exchanger 41 is provided to change the heat medium TM2, which is different from the heat medium TM1 (antifreeze) that flows into the heat storage tank 20 when the heat collected by the solar collector 10 is transferred to the solar heat storage tank 20. While various fluids that can be used as the heat medium TM1 can be used as the heat medium TM2, water is used in this embodiment. The heat extraction heat exchanger 41 exchanges heat between fluids. A plate-type heat exchanger is typically used, but other common heat exchangers, such as a shell-and-tube heat exchanger, may also be used. The solar collector 10 and the heat extraction heat exchanger 41 are connected by a first heat extraction supply pipe 43 and a first heat extraction return pipe 44. The first heat extraction supply pipe 43 is a flow path that guides the heat medium TM1 from the solar collector 10 to the heat extraction heat exchanger 41. The first heat extraction return pipe 44 is a flow path that guides the heat medium TM1 from the heat extraction heat exchanger 41 to the solar collector 10. In this embodiment, a first heat extraction pump 45 is arranged in the first heat extraction return pipe 44, and is configured to be able to circulate the heat medium TM1 between the solar collector 10 and the heat extraction heat exchanger 41. The first heat extraction pump 45 is typically configured to be able to adjust the discharge flow rate of the heat medium TM1 by inverter control.

[0027] The heat storage tank 20 is capable of storing solar thermal energy collected by the solar collector 10. In this embodiment, two heat storage tanks are provided: a first heat storage tank (hereinafter referred to as the "first heat storage tank 20A") and a second heat storage tank (hereinafter referred to as the "second heat storage tank 20B"). In this embodiment, the first heat storage tank 20A and the second heat storage tank 20B have the same configuration and are separate entities, so they are distinguishable by different names. However, when referring to their common configuration or properties, they will be collectively referred to as the "heat storage tank 20." The heat storage tank 20 employs a phase change material, which changes phase between solid and liquid, as the heat storage material 26 to increase the heat storage density. The heat storage material 26, which uses a phase change material, is capable of reversibly melting and solidifying (capable of repeatedly undergoing reversible phase changes). In this embodiment, sodium acetate trihydrate is used as the heat storage material 26, but there are no particular limitations as long as it is a phase change material that can store heat at a high density by utilizing the latent heat generated during solid-liquid phase transformation, and paraffin, erythritol, molten salt, etc. can also be used depending on the application conditions. By selecting an appropriate material as the heat storage material 26, the heat storage temperature and heat release temperature can be set appropriately.

[0028] The configuration of the heat storage tank 20 will now be described with reference to Figures 2(A) and 2(B). Figure 2(A) is a vertical cross-sectional view of the heat storage tank 20, and Figure 2(B) is a horizontal cross-sectional view of the heat storage tank 20. Figure 2(B) is a horizontal cross-sectional view taken along the arrow BB in Figure 2(A). The heat storage tank 20 has a heat transfer cylinder 21, an outer cylinder 23, blades 25, the above-mentioned heat storage material 26, and a movement mechanism 27.

[0029] The heat transfer cylinder 21 is a cylindrical member through which the heat medium TM2 flows, and in this embodiment, is formed into a hollow cylindrical shape with one end face (the upper end face in this embodiment) open and the other end face (the lower end face in this embodiment) closed. In this embodiment, the heat transfer cylinder 21 is disposed such that the axis of the cylinder extends vertically. Inside the heat transfer cylinder 21, the end of the heat storage tank return pipe 53 opens near the closed end face, and the end of the heat storage tank supply pipe 54 opens near the open end face. The heat storage tank return pipe 53 is a flow path that constitutes part of the flow path that guides the heat medium TM2 of the heat extraction heat exchanger 41 (see FIG. 1 ) to the heat storage tank 20. The heat storage tank supply pipe 54 is a flow path that constitutes part of the flow path that guides the heat medium TM2 of the heat storage tank 20 to the heat extraction heat exchanger 41.

[0030] The outer cylinder 23 is a member that houses the heat transfer cylinder 21. In this embodiment, the outer cylinder 23 is formed in a hollow cylindrical shape and has a larger diameter than the heat transfer cylinder 21. The outer cylinder 23 is not limited to a cylindrical shape, and the cross-sectional shape perpendicular to the axis may be elliptical or polygonal, such as rectangular, pentagonal, or hexagonal. The axial length of the outer cylinder 23 is approximately the same as that of the heat transfer cylinder 21 in the example shown in FIG. 2(A), but may be longer than the heat transfer cylinder 21 (e.g., more than twice that of the heat transfer cylinder 21). In this embodiment, the outer cylinder 23 and the heat transfer cylinder 21 are arranged so that their respective axes overlap, but they may also be arranged so that their respective axes are spaced apart. A space capable of holding the heat storage material 26 is formed between the outer surface of the heat transfer cylinder 21 and the inner surface of the outer cylinder 23. In this embodiment, both end faces of the outer cylinder 23 are closed, but the upper end face may be open, for example.

[0031] The blades 25 are plate-like members provided in the space between the outer surface of the heat transfer cylinder 21 and the inner surface of the outer cylinder 23. The blades 25 serve to prevent the heat storage material 26 from accumulating on the outer surface of the heat transfer cylinder 21 when it changes from a liquid to a solid. The blades 25 also have the function of guiding the dissolved phase near the heat transfer cylinder 21 to the outside (toward the outer cylinder 23) when the heat storage material 26 changes from a solid to a liquid. In this embodiment, four blades 25 are provided, but the number may be three, two, one, or five or more as long as they can perform the above-mentioned functions. The blades 25 typically have a length approximately equal to the axial length of the heat transfer cylinder 21. 2(A) and 2(B), the blades 25 have a width that is approximately equal to the distance between the heat transfer cylinder 21 and the outer cylinder 23 on the radius of the outer cylinder 23, but may have a width that is 1 / 6 to 5 / 6, 1 / 4 to 3 / 4, 1 / 3 to 2 / 3, or 1 / 2 of the distance between the heat transfer cylinder 21 and the outer cylinder 23. In this embodiment, the blades 25 are basically formed into a rectangular shape. One side of the blades 25 having a rectangular shape extends along the axial direction of the heat transfer cylinder 21 and is disposed in close proximity to or in sliding contact with the outer surface of the heat transfer cylinder 21. In this embodiment, the blades 25 are fixed to the outer cylinder 23, but may be attached to another member.

[0032] In this embodiment, the moving mechanism 27 rotates the heat transfer cylinder 21 around its axis. The moving mechanism 27 includes a motor 28 disposed outside the outer cylinder 23 and a shaft 29 rotated by the motor 28. In this embodiment, the shaft 29 penetrates the end face of the outer cylinder 23 and is connected to the closed end face of the heat transfer cylinder 21. A shaft seal device is provided at the portion of the outer cylinder 23 through which the shaft 29 penetrates. The shaft 29 is disposed outside the heat transfer cylinder 21 so as to extend in the same line as the axis of the heat transfer cylinder 21. The moving mechanism 27 is typically inverter-controlled to adjust the rotation speed of the shaft 29 and, therefore, the rotation speed of the heat transfer cylinder 21. Note that, although the moving mechanism 27 is disposed below the heat transfer cylinder 21 in the example shown in FIG. 2(A), the moving mechanism 27 may also be disposed above the heat transfer cylinder 21. In this case, the heat storage tank return pipe 53 and the heat storage tank supply pipe 54 may be disposed at positions away from the axis of the heat transfer cylinder 21. Moreover, instead of fixing the above-mentioned blades 25 to the outer cylinder 23, they may be fixed to a stand (not shown) on which the motor 28 is installed.

[0033] In the heat storage tank 20 configured as described above, when the heat storage material 26 is held in a solid state, a high-temperature heat medium TM2 that retains solar heat collected by the solar collector 10 (see FIG. 1 ) is introduced into the heat transfer cylinder 21, and heat exchange occurs between the heat medium TM2 and the heat storage material 26. The solid heat storage material 26 that receives heat from the high-temperature heat medium TM2 melts and becomes liquid when the temperature reaches or exceeds its melting point (approximately 58°C in the case of sodium acetate trihydrate, which is used in this embodiment). In this way, the heat storage material 26 can store not only sensible heat associated with a temperature rise due to the heat received from the heat medium TM2, but also latent heat associated with a phase change from solid to liquid. In other words, the heat storage material 26 functions as a latent heat storage material. The heat storage material 26 held in a solid state typically melts and spreads outward, from the heat transfer cylinder 21 side toward the outer cylinder 23 side. At this time, in this embodiment, by operating the moving mechanism 27 to rotate the heat transfer cylinder 21, the liquid phase clinging to the vicinity of the heat transfer cylinder 21 is guided by the blades 25 to the side of the outer cylinder 23, which contributes to melting the solid phase heat storage material 26 present on the side of the outer cylinder 23.

[0034] When storing solar heat collected by the solar collector 10 (see FIG. 1 ), if the temperature of the inflowing heat medium TM2 is close to the melting point of the heat storage material 26, the heat storage tank 20 may be considered to have reached its full heat storage capacity (full storage) when all of the stored heat storage material 26 becomes liquid. In this embodiment, to estimate whether the heat storage tank 20 is fully stored, an in-cylinder thermometer 86 is provided in the space between the heat transfer cylinder 21 and the outer cylinder 23. The in-cylinder thermometer 86 is disposed at a position where the heat storage material 26 last changes from solid to liquid and corresponds to a first temperature detector. The position where the heat storage material 26 last changes from solid to liquid does not necessarily have to be the position where the heat storage material 26 lastly melts from solid to liquid, but may be a position where the melting occurs at the end (towards the end). In this embodiment, such a position is estimated to be a position near the side wall of the outer cylinder 23 in the radial direction of the outer cylinder 23. Regarding the height direction, it is possible to locate the in-cylinder thermometer 86 at a lower position in consideration of the tendency for low-temperature fluid to collect at the lower part, and it is possible to locate the in-cylinder thermometer 86 at an upper position in consideration of the fact that the heat medium TM2 is discharged below the heat transfer cylinder 21 and collected at the upper part as in this embodiment. The placement of the in-cylinder thermometer 86 can be determined taking these factors into consideration and the characteristics of the heat storage tank 20. Multiple in-cylinder thermometers 86 may be placed at appropriate intervals. In this case, whether the storage tank is full or not may be determined based on the one with the lowest detected temperature.

[0035] When utilizing (dissipating) the heat stored in the liquid heat storage material 26, a heat medium TM2 having a temperature lower than the freezing point of the liquid heat storage material 26 is introduced into the heat transfer cylinder 21, and heat exchange occurs between the heat medium TM2 and the heat storage material 26. The liquid heat storage material 26, cooled by the low-temperature heat medium TM2, changes to a solid when it reaches its freezing point, and releases heat of solidification during this phase change. The heat of solidification released from the heat storage material 26 is absorbed by the heat medium TM2, causing the temperature of the heat medium TM2 to rise. The heat medium TM2 with the increased temperature is supplied to a heat utilization location (for example, the heat utilization device 91 shown in FIG. 1 ) to be described later and utilized. Meanwhile, the heat storage material 26, which changes from a liquid to a solid, solidifies from the heat transfer cylinder 21 side toward the outer cylinder 23 side. However, when the heat storage material 26 solidifies and accumulates on the outer periphery of the heat transfer cylinder 21, the solid heat storage material 26 has a high thermal resistance, and therefore the transfer of the heat of solidification of the heat storage material 26 to the heat medium TM2 is reduced. Therefore, in this embodiment, during heat dissipation, the movement mechanism 27 is operated to rotate the heat transfer cylinder 21, and the solid heat storage material 26 accumulated around the heat transfer cylinder 21 is peeled off by the blades 25, thereby reducing the thermal resistance caused by the solidified layer and improving the efficiency of heat transfer from the heat storage material 26 to the heat medium TM2. At this time, the amount of heat transferred from the heat storage material 26 to the heat medium TM2 can be adjusted by changing the rotation speed of the heat transfer cylinder 21 (the movement speed between the heat transfer cylinder 21 and the blades 25).

[0036] The description of the heat storage system 1 will continue, again mainly referring to Figure 1. In the following description, when referring to the configuration of the heat storage tank 20, Figures 2(A) and 2(B) will be referenced as appropriate. The heat storage tank 20 and the heat extraction heat exchanger 41 are connected by a second heat extraction supply pipe 46, a second heat extraction return pipe 47, a heat storage tank return pipe 53, and a heat storage tank supply pipe 54. The second heat extraction supply pipe 46 is a flow path that guides the heat medium TM2 that flows out of the heat extraction heat exchanger 41 to the heat storage tank return pipe 53. The heat storage tank return pipe 53 is a flow path that guides the heat medium TM2 that flows in from the second heat extraction supply pipe 46 and the heat medium TM2 from other devices (e.g., a heat utilization device 91) described later, into the inside of the heat transfer cylinder 21 described above. In this embodiment, the heat storage tank return pipe 53 branches into a first heat storage tank return pipe 53A connected to the first heat storage tank 20A and a second heat storage tank return pipe 53B connected to the second heat storage tank 20B on the downstream side in the flow direction of the heat medium TM2. The heat storage tank supply pipe 54 is a flow path that guides the heat medium TM2 flowing out from the heat transfer cylinder 21 to a flow path that supplies the heat medium TM2 to the second heat extraction return pipe 47 and other devices (for example, the heat utilization device 91) described later. In this embodiment, the heat storage tank supply pipe 54 is configured such that the first heat storage tank supply pipe 54A connected to the first heat storage tank 20A and the second heat storage tank supply pipe 54B connected to the second heat storage tank 20B merge into one flow path on the downstream side in the flow direction of the heat medium TM2. When the two heat storage tanks 20A, 20B are referred to collectively as heat storage tanks 20 in reference to their common configuration or properties, the first heat storage tank return pipe 53A and the second heat storage tank return pipe 53B are collectively referred to as the "heat storage tank return pipe 53," and the first heat storage tank supply pipe 54A and the second heat storage tank supply pipe 54B are collectively referred to as the "heat storage tank supply pipe 54." The second heat extraction return pipe 47 is a flow path that guides the heat medium TM2 that has flowed through the heat storage tank supply pipe 54 to the heat extraction heat exchanger 41.

[0037] In this embodiment, a second heat extraction pump 48 is disposed in the second heat extraction return pipe 47, and is configured to circulate the heat medium TM2 between the heat storage tank 20 and the heat extraction heat exchanger 41. The second heat extraction pump 48 is typically inverter-controlled to adjust the discharge flow rate of the heat medium TM2. In this embodiment, solar heat collected by the heat collector 10 and held in the heat medium TM1 is transferred to the heat medium TM2 in the heat extraction heat exchanger 41 and supplied to the heat storage tank 20. In other words, the heat medium TM2 flowing into the heat storage tank 20 is indirectly supplied from the heat collector 10. Therefore, the heat extraction heat exchanger 41, the first heat extraction supply pipe 43, the first heat extraction return pipe 44, the first heat extraction pump 45, the second heat extraction supply pipe 46, the second heat extraction return pipe 47, the second heat extraction pump 48, the heat storage tank return pipe 53, and the heat storage tank supply pipe 54 correspond to a transport mechanism. Furthermore, in this embodiment, the first heat extraction pump 45 and the second heat extraction pump 48 work together to transport the solar heat collected by the solar collector 10 to the heat storage tank 20 via the heat media TM1 and TM2. Therefore, the first heat extraction pump 45 and the second heat extraction pump 48 can be collectively seen as a heat extraction pump of the heat storage system.

[0038] The flow path connecting the heat collector 10 and the heat storage tank 20 is provided with a two-way valve capable of blocking the flow path and a three-way valve for changing the flow direction of the fluid at appropriate locations. In this embodiment, a first two-way valve 61 is provided on the second heat extraction supply pipe 46, a second two-way valve 62 on the first heat storage tank return pipe 53A, a third two-way valve 63 on the first heat storage tank supply pipe 54A, a fourth two-way valve 64 on the second heat storage tank return pipe 53B, and a fifth two-way valve 65 on the second heat storage tank supply pipe 54B. A first three-way valve 71 is provided at the connection between the heat storage tank supply pipe 54 and the second heat extraction return pipe 47. A heat dissipation supply pipe 55 is connected to the remaining port of the first three-way valve 71. The heat dissipation supply pipe 55 is a flow path that guides the heat medium TM2 flowing through the heat storage tank supply pipe 54 to the heat utilization device 91. Instead of the first three-way valve 71, two-way valves may be provided in the second heat collection return pipe 47 and the heat radiation supply pipe 55, respectively.

[0039] The heat utilization device 91 is a device that utilizes the heat stored in the heat storage tank 20. The heat utilization device 91 can be applied to various devices that can utilize the temperature of the heat medium TM2 supplied from the heat storage tank 20. Examples of uses of the heat utilization device 91 include a water heater for heating the interior of an agricultural greenhouse, a seedbed heater for cultivation in an agricultural greenhouse, an agricultural hot water heater, an agricultural cultivation solution heater, an industrial indoor water heater, an industrial hot water heater, a general-purpose heating hot water heater, a general-purpose hot water heater, a medical dialysis fluid heater, an absorption-type hot and cold water generator, and a snow melting machine.

[0040] The heat radiation supply pipe 55 has one end connected to the first three-way valve 71, and the other end connected to the heat utilization device 91. In addition, one end of a heat radiation return pipe 56 is connected to the heat utilization device 91. The heat radiation return pipe 56 is a flow path that guides the heat medium TM2 flowing out from the heat utilization device 91 to the heat storage tank return pipe 53. The other end of the heat radiation return pipe 56 is connected to a connection between the second heat extraction supply pipe 46 and the heat storage tank return pipe 53. A sixth two-way valve 66 is arranged in the heat radiation return pipe 56. Note that, instead of the first two-way valve 61 and the sixth two-way valve 66, a three-way valve may be arranged at a connection between the second heat extraction supply pipe 46, the heat storage tank return pipe 53, and the heat radiation return pipe 56. In addition, in this embodiment, a heat radiation pump 58 is arranged in the heat radiation supply pipe 55, and is configured to circulate the heat medium TM2 between the heat storage tank 20 and the heat utilization device 91. The heat radiation pump 58 is typically inverter-controlled to adjust the discharge flow rate of the heat medium TM2. In this embodiment, the above-described flow path configuration and the heat radiation pump 58 enable the heat medium TM2 flowing out from the heat storage tank 20 to be directly supplied to the heat utilization device 91. In this embodiment, the heat storage tank return pipe 53, the heat storage tank supply pipe 54, the heat radiation supply pipe 55, the heat radiation return pipe 56, and the heat radiation pump 58 correspond to a supply mechanism. Therefore, in this embodiment, the heat storage tank return pipe 53 and the heat storage tank supply pipe 54 serve as both a part of the transport mechanism and a part of the supply mechanism.

[0041] In addition, in this embodiment, a backup system is configured to serve as a substitute in the event that heat cannot be supplied from the heat storage tank 20 to the heat utilization device 91. The backup system includes an auxiliary heat exchanger 73 and associated flow paths. The auxiliary heat exchanger 73 exchanges heat between the heat medium TM3 from an auxiliary heat source (not shown) and the heat medium TM2. A plate-type heat exchanger is typically used for the auxiliary heat exchanger, but other common heat exchangers such as a shell-and-tube heat exchanger may also be used. The auxiliary heat source (not shown) may be hot water produced in a separate system, a geothermal heat pump heat source, an air-cooled heat pump water heater, an oil- or gas-fired boiler, or hot spring waste heat. The auxiliary heat exchanger 73 and the auxiliary heat source (not shown) are connected by an auxiliary circulation pipe 77 through which the heat medium TM3 flows. An auxiliary pump 74 is disposed in the auxiliary circulation pipe 77, which is configured to circulate the heat medium TM3 between the auxiliary heat exchanger 73 and the auxiliary heat source (not shown). The heat medium TM3 can be any of various fluids that can be used for the heat mediums TM1 and TM2. Although the auxiliary heat exchanger 73 is configured as a parallel flow in FIG.

[0042] One end of an auxiliary supply pipe 75 and one end of an auxiliary return pipe 76 are connected to the heat medium TM2 side of the auxiliary heat exchanger 73. The auxiliary supply pipe 75 is a flow path for the heat medium TM2 flowing out of the auxiliary heat exchanger 73, and the auxiliary return pipe 76 is a flow path for the heat medium TM2 flowing into the auxiliary heat exchanger 73. The other end of the auxiliary supply pipe 75 is connected to the heat radiation supply pipe 55 upstream of the heat radiation pump 58. A second three-way valve 72 is provided at the connection between the heat radiation supply pipe 55 and the auxiliary supply pipe 75. Note that, instead of the second three-way valve 72, two-way valves may be provided in the heat radiation supply pipe 55 upstream of the connection portion of the auxiliary supply pipe 75 and in the auxiliary supply pipe 75, respectively. The other end of the auxiliary return pipe 76 is connected to the heat radiation return pipe 56 upstream of the sixth two-way valve 66. A seventh two-way valve 67 is provided in the auxiliary return pipe 76. Instead of the sixth two-way valve 66 and the seventh two-way valve 67, a three-way valve may be disposed at the connection between the heat radiation return pipe 56 and the auxiliary return pipe 76.

[0043] In this embodiment, the system has a relief supply pipe 78 and a relief return pipe 79 for releasing the heat medium TM2 that retains the heat collected by the solar collector 10 to the auxiliary heat exchanger 73. The relief supply pipe 78 is connected to the second heat extraction supply pipe 46 upstream of the first two-way valve 61 and to the auxiliary return pipe 76 downstream of the seventh two-way valve 67. An eighth two-way valve 68 is arranged in the relief supply pipe 78. The relief return pipe 79 is connected to the auxiliary supply pipe 75 upstream of the second three-way valve 72 and to the second heat extraction return pipe 47 downstream of the first three-way valve 71. A ninth two-way valve 69 is arranged in the relief return pipe 79.

[0044] In the thermal storage system 1 according to this embodiment, a pyranometer 81 is provided adjacent to or near the solar collector 10. The pyranometer 81 is an instrument that measures the amount of solar radiation. Therefore, the pyranometer 81 detects a physical quantity that changes in response to changes in the amount of solar radiation, and corresponds to a solar radiation-related physical quantity measuring instrument. The pyranometer 81 is typically one that measures global solar radiation, but may also be one that measures direct solar radiation. The pyranometer 81 is provided to estimate the amount of solar radiation irradiated onto the solar collector 10, and therefore being provided adjacent to or close to the solar collector 10 means being provided within a range where the amount of solar radiation on the solar collector 10 can be estimated.

[0045] The heat storage system 1 also includes several thermometers. Specifically, a heat extraction thermometer 82 that measures the temperature of the heat medium TM1 flowing into the heat extraction heat exchanger 41 is provided in the heat extraction heat exchanger 41 or the first heat extraction supply pipe 43 near the heat extraction heat exchanger 41. A heat storage thermometer 83 that measures the temperature of the heat medium TM2 flowing into the heat storage tank 20 is provided in the heat storage tank 20 or the heat storage tank return pipe 53 near the heat storage tank 20. A heat release thermometer 84 that measures the temperature of the heat medium TM2 flowing out from the heat storage tank 20 is provided in the heat storage tank 20 or the heat storage tank supply pipe 54 near the heat storage tank 20. Although the arrangement of the heat storage thermometer 83 and the heat release thermometer 84 has been described here using the collectively referred to heat storage tank 20 as an example, they are typically provided in each of the first heat storage tank 20A and the second heat storage tank 20B. Further, an auxiliary thermometer 85 for measuring the temperature of the heat medium TM2 flowing out from the auxiliary heat exchanger 73 is provided on the auxiliary outflow pipe 75.

[0046] The control device 80 is a device that controls the operation of the thermal storage system 1. The control device 80 is connected to the motor 28 (see FIG. 2(A)) of the thermal storage tank 20 via a communication line (wired or wireless; the same applies below), and is configured to be able to start and stop the motor 28 and adjust the rotational speed of the shaft 29 (see FIG. 2(A)). The control device 80 is also connected to each of the first heat extraction pump 45, the second heat extraction pump 48, and the heat release pump 58 via communication lines, and is configured to be able to start and stop each pump and adjust the discharge flow rate. The control device 80 is also connected to the auxiliary pump 74 via a communication line, and is configured to be able to start and stop the auxiliary pump 74.

[0047] The control device 80 is also connected to each of the first two-way valve 61 to the ninth two-way valve 69 via communication lines, and is configured to be able to open and close each of the two-way valves 61 to 69. The control device 80 is also connected to each of the first three-way valve 71 and the second three-way valve 72 via communication lines, and is configured to be able to switch the flow paths of each of the three-way valves 71, 72. The control device 80 is also connected to a pyranometer 81 via a communication line, and is configured to be able to receive values ​​measured by the pyranometer 81 as signals. The control device 80 stores the relationship between the values ​​obtained from the pyranometer 81, the flow rate of the heat medium TM1 flowing in and out of the solar collector 10, and the temperature difference of the heat medium TM1 flowing in and out of the solar collector 10. In addition, the control device 80 is connected to each of the heat extraction thermometer 82, heat storage thermometer 83, heat dissipation thermometer 84, auxiliary thermometer 85, and in-cylinder thermometer 86 by communication lines, and is configured to be able to receive the values ​​measured by each thermometer 82 to 86 as signals.

[0048] Next, the operation of the thermal storage system 1 will be described with reference to Fig. 3 in conjunction with Fig. 1 and Figs. 2(A) and 2(B). Fig. 3 is a table showing the relationship between the operating state of the thermal storage system 1 and the states of the valves 61 to 69, 71, and 72 and the pumps 45, 48, 58, and 74. In the following description, unless otherwise specified, the operation of the valves 61 to 69, 71, and 72 and the pumps 45, 48, 58, and 74 is controlled by commands from the control device 80. As shown in Fig. 3, the operating states of the thermal storage system 1 can be roughly divided into a heat storage state, a heat release state, an auxiliary state, and a relief state.

[0049] (Operation in heat storage state) The heat storage state is an operation for storing solar heat collected by the solar collector 10 in the heat storage tank 20. In the heat storage state in this embodiment, as shown in FIG. 3 , the first two-way valve 61 to the fifth two-way valve 65 and the seventh two-way valve 67 are open, and the sixth two-way valve 66 and the eighth two-way valves 68 to ninth two-way valves 69 are closed. The first three-way valve 71 connects the second heat extraction return pipe 47 to the heat storage tank supply pipe 54, and its valve element is oriented to block the flow path to the heat radiation supply pipe 55. The second three-way valve 72 connects the auxiliary supply pipe 75 to the downstream heat radiation supply pipe 55, and its valve element is oriented to block the flow path to the upstream heat radiation supply pipe 55. The first heat extraction pump 45 and the second heat extraction pump 48 are each operated under inverter control. The heat radiation pump 58 and the auxiliary pump 74 are stopped in principle, but may be operated depending on the situation. The motor 28 of each heat storage tank 20 is operated under inverter control.

[0050] For ease of explanation, the case where heat is stored in both the first heat storage tank 20A and the second heat storage tank 20B is shown here, but when heat is stored in only one of them, the two-way valve that allows the heat medium TM2 to flow in and out of the heat storage tank 20 that stores heat is opened, and the motor 28 of that heat storage tank 20 is operated. On the other hand, the two-way valve that does not allow the heat medium TM2 to flow in and out of the heat storage tank 20 is closed, and the motor 28 of that heat storage tank 20 is stopped. For example, when heat is stored in the first heat storage tank 20A but not in the second heat storage tank 20B, the second two-way valve 62 and the third two-way valve 63 are opened, the fourth two-way valve 64 and the fifth two-way valve 65 are closed, the motor 28 of the first heat storage tank 20A is operated, and the motor 28 of the second heat storage tank 20B is stopped.

[0051] As a point to be considered in operation in the heat storage state, the inventors have noticed that it is difficult to control the balance between heat input and output to the heat storage tank 20 because the amount of solar heat that can be collected by the heat collector 10 is not constant. In this embodiment, a latent heat storage material is used as the heat storage material 26 to increase the heat storage density and reduce the size of the heat storage tank 20. However, if the amount of heat collected by the heat collector 10 decreases and the heat medium TM2 that is below the freezing point of the heat storage material 26 enters the heat storage tank 20, heat of solidification is generated from the heat storage material 26, and heat is released even though heat is being stored. In this embodiment, the following heat storage operation control is performed to avoid such inconvenience.

[0052] The main point is that, since the melting point of sodium acetate trihydrate employed as the heat storage material 26 in this embodiment is 58°C, the heat medium TM2 at a temperature equal to or higher than this melting point (preferably higher than the melting point) is caused to flow into the heat storage tank 20 during the heat storage operation. In this embodiment, the temperature of the heat medium TM2 caused to flow into the heat storage tank 20 is set to about 70°C. This temperature of the heat medium TM2 caused to flow into the heat storage tank 20 during the heat storage operation corresponds to the first predetermined temperature. The first predetermined temperature may have a range, for example, from 70°C to 80°C.

[0053] During operation in the heat storage state described above, the heat medium TM1 circulates between the solar collector 10 and the heat extraction heat exchanger 41. The circulation flow rate of the heat medium TM1 may be set to a minimum flow rate to prevent the heat medium TM1 from becoming too high or freezing. As the heat medium TM1 circulates, the heat medium TM1, whose temperature has increased in the solar collector 10, flows into the heat extraction heat exchanger 41. The heat medium TM1, whose temperature has decreased after heat exchange with the heat medium TM2 in the heat extraction heat exchanger 41, leaves the heat extraction heat exchanger 41 and flows back into the solar collector 10. At this time, the control device 80 receives a measurement value from the heat extraction thermometer 82 and controls the discharge flow rate of the first heat extraction pump 45 using an inverter so that the measurement value of the heat extraction thermometer 82 becomes a predetermined value (e.g., 72°C). At this time, if the amount of solar radiation decreases and the temperature of the heat medium TM1 flowing out of the solar collector 10 falls below the predetermined value, it takes some time for the heat extraction thermometer 82 to detect this. Even if the discharge flow rate of the heat extraction pump 45 is reduced after the heat extraction thermometer 82 detects this low temperature, it takes additional time for the measurement value of the heat extraction thermometer 82 to return to a predetermined value. Therefore, in this embodiment, the control device 80 receives measurement values ​​from the actinometer 81 and controls the discharge flow rate of the first heat extraction pump 45 using an inverter to increase or decrease the flow rate of the heat medium TM1 flowing through the solar collector 10 in accordance with the measurement value of the actinometer 81. At this time, the control device 80 compares the measurement value of the actinometer 81 with a relationship stored in the control device 80 and adjusts the discharge flow rate of the first heat extraction pump 45 so that the flow rate of the heat medium TM1 becomes such that the measurement value of the heat extraction thermometer 82 becomes a predetermined value. Controlling the discharge flow rate of the first heat extraction pump 45 in accordance with the measurement value of the actinometer 81 makes it possible to quickly follow changes in the amount of solar radiation and reduce the possibility that the heat medium TM1 will flow into the heat extraction heat exchanger 41 at a temperature lower than a predetermined value.

[0054] The heat medium TM2 circulates between the heat extraction heat exchanger 41 and the heat storage tank 20. Due to this circulation, the heat medium TM2 whose temperature has increased in the heat extraction heat exchanger 41 flows into the heat storage tank 20, and the heat medium TM2 whose temperature has decreased due to heat exchange with the heat storage material 26 in the heat storage tank 20 leaves the heat storage tank 20 and flows back into the heat extraction heat exchanger 41. At this time, the control device 80 receives a measurement value from the heat storage thermometer 83 and controls the discharge flow rate of the second heat extraction pump 48 using an inverter so that the measurement value of the heat storage thermometer 83 becomes a first predetermined temperature (for example, approximately 70°C). The discharge flow rate of the second heat extraction pump 48 may be set to a minimum flow rate from the viewpoint of preventing the heat medium TM2 from freezing. As described above, the heat medium TM2 that has flowed into the heat storage tank 20 exchanges heat with the heat storage material 26, and the heat storage material 26, which was held in a solid state, melts and becomes liquid, spreading outward from the heat transfer cylinder 21 side toward the outer cylinder 23 side. At this time, since the motor 28 is operating, the liquid heat storage material 26 around the heat transfer cylinder 21 is guided by the blades 25 toward the outer cylinder 23, thereby accelerating the melting of the remaining solid heat storage material 26. Furthermore, the control device 80 may receive a measurement value from the in-cylinder thermometer 86, and when the measurement value of the in-cylinder thermometer 86 reaches a predetermined temperature (for example, about 68°C), it may estimate that the heat storage tank 20 is fully charged and stop the flow of the heat medium TM2 at the first predetermined temperature into the heat storage tank 20. The predetermined temperature (for example, about 68°C) measured by the in-cylinder thermometer 86 at which it is estimated that the heat storage tank 20 is fully charged is a temperature equal to or higher than the melting point of the heat storage material 26 and corresponds to the third predetermined temperature. Note that the third predetermined temperature may be a temperature equal to or higher than the melting point of the heat storage material 26 and close to the melting point, or may be a temperature somewhat higher than the melting point. If the third predetermined temperature is set to a temperature higher than the melting point of the heat storage material 26, it is possible to store the difference between the third predetermined temperature and the melting point of the heat storage material 26 as sensible heat. The third predetermined temperature may be determined in consideration of the characteristics of the heat storage material 26. The flow of the heat medium TM2 at the first predetermined temperature into the heat storage tank 20 can be stopped by operating in a release state, which will be described later.

[0055] As mentioned above, the heat radiation pump 58 and the auxiliary pump 74 are stopped in principle during operation in the heat storage state, but may be operated depending on the situation. An example of when the heat radiation pump 58 and the auxiliary pump 74 are operated during operation in the heat storage state is when it is necessary to supply heat to the heat utilization device 91 while heat is being collected by the heat collector 10. In this case, the operation of the heat radiation pump 58 and the auxiliary pump 74 to supply heat to the heat utilization device 91 corresponds to operation in the auxiliary state, which will be described in detail later. In other words, this indicates that operation in the auxiliary state can be performed in parallel with operation in the heat storage state.

[0056] (Operation in heat dissipation mode) The heat dissipation state is an operation for supplying heat stored in the heat storage tank 20 to the heat utilization device 91. In the heat dissipation state in this embodiment, as shown in FIG. 3 , the first two-way valve 61 and the seventh two-way valve 67 are closed, and the other two-way valves 62-66 and 68-69 are open. The first three-way valve 71 connects the heat storage tank supply pipe 54 and the heat dissipation supply pipe 55, and its valve element is oriented to block the flow path to the second heat extraction return pipe 47. The second three-way valve 72 connects the upstream and downstream sides of the heat dissipation supply pipe 55, and its valve element is oriented to block the flow path to the auxiliary supply pipe 75. The first heat extraction pump 45 and the second heat extraction pump 48 are generally stopped, but may be operated depending on the situation. The heat dissipation pump 58 is operated under inverter control, and the auxiliary pump 74 is stopped. The motors 28 of each heat storage tank 20 are operated under inverter control.

[0057] For ease of explanation, the case where heat is dissipated from both first heat storage tank 20A and second heat storage tank 20B is shown here, but when heat is dissipated from only one of them, the two-way valve that allows the heat medium TM2 to flow in and out of the heat storage tank 20 from which heat is to be dissipated is opened, and the motor 28 of that heat storage tank 20 is operated. On the other hand, the two-way valve that does not allow the heat medium TM2 to flow in and out of the heat storage tank 20 is closed, and the motor 28 of that heat storage tank 20 is stopped. For example, when heat is dissipated from first heat storage tank 20A but not from second heat storage tank 20B, second two-way valve 62 and third two-way valve 63 are opened, fourth two-way valve 64 and fifth two-way valve 65 are closed, motor 28 of first heat storage tank 20A is operated, and motor 28 of second heat storage tank 20B is stopped. Whether to radiate heat from one or both of the first heat storage tank 20A and the second heat storage tank 20B may be determined depending on the amount of heat required by the heat-utilization device 91.

[0058] During operation in the heat dissipation state described above, the heat medium TM2 circulates between the heat storage tank 20 and the heat utilization device 91. In this embodiment, the heat medium TM2 flowing out of the heat storage tank 20 is supplied directly to the heat utilization device 91 without passing through a heat exchanger. Due to this circulation, the heat medium TM2 whose temperature has increased in the heat storage tank 20 flows into the heat utilization device 91, and the heat medium TM2 whose temperature has decreased as a result of heat utilization in the heat utilization device 91 leaves the heat utilization device 91 and flows back into the heat storage tank 20. At this time, the control device 80 receives a measurement value from the heat dissipation thermometer 84 and controls the discharge flow rate of the heat dissipation pump 58 and / or the motor 28 of the heat storage tank 20 using an inverter so that the measurement value of the heat dissipation thermometer 84 becomes a second predetermined temperature. Here, the second predetermined temperature is a temperature suitable for supply to the heat utilization device 91 and within a temperature range that can be increased by heating the heat medium TM2 using the heat of solidification of the heat storage material 26, and may be, for example, 40°C. The rotation speed of the motor 28 of the heat storage tank 20 is changed in order to adjust the amount of solid heat storage material 26 peeled off around the heat transfer cylinder 21 by the rotation of the heat transfer cylinder 21, thereby adjusting the amount of heat transferred from solidification of the heat storage material 26 to the heat medium TM2. As described above, when the heat storage material 26 solidifies and accumulates around the heat transfer cylinder 21, the amount of heat transferred to the heat medium TM2 inside the heat transfer cylinder 21 decreases due to the thermal resistance of the solid heat storage material 26. However, if the amount of heat storage material 26 peeled off around the heat transfer cylinder 21 increases, the amount of heat transferred increases, and if the amount of peeled off decreases, the amount of heat transferred decreases. By adjusting this and the flow rate of the heat medium TM2 circulating between the heat storage tank 20 and the heat utilization device 91, the heat medium TM2 supplied to the heat utilization device 91 is adjusted to an appropriate temperature. When the heat stored in the heat storage tank 20 is depleted and it becomes impossible to supply the heat medium TM2 at the second predetermined temperature to the heat utilization device 91, the operation can be shifted to the auxiliary state, which will be described later.

[0059] As mentioned above, the first heat extraction pump 45 and the second heat extraction pump 48 are stopped in principle during operation in the heat dissipation state, but may be operated depending on the situation. An example of when the first heat extraction pump 45 and the second heat extraction pump 48 are operated during operation in the heat dissipation state is when it is necessary to release the heat collected in the heat collector 10 while releasing the heat stored in the heat storage tank 20. In this case, operation of the first heat extraction pump 45 and the second heat extraction pump 48 to release the heat collected in the heat collector 10 corresponds to operation in the release state, which will be described in detail later. In other words, this shows that operation in the release state can be performed in parallel with operation in the heat dissipation state.

[0060] (Assisted driving) The auxiliary state operation is an operation in which, for example, when the heat medium TM2 at the second predetermined temperature cannot be supplied from the heat storage tank 20, heat generated in an auxiliary heat source (not shown) is transferred to the heat medium TM2 and supplied to the heat utilization device 91. When the auxiliary state operation in this embodiment is performed alone, as shown in FIG. 3 , the seventh two-way valve 67 is open, and the other two-way valves 61-66 and 68-69 are closed. The first three-way valve 71 connects the second heat extraction return pipe 47 to the heat storage tank supply pipe 54, and its valve element is oriented to block the flow path to the heat dissipation supply pipe 55. The second three-way valve 72 connects the auxiliary supply pipe 75 to the downstream heat dissipation supply pipe 55, and its valve element is oriented to block the flow path to the upstream heat dissipation supply pipe 55. The first heat extraction pump 45 and the second heat extraction pump 48 are stopped, the heat dissipation pump 58 is operated by inverter control, and the auxiliary pump 74 is operating. The motors 28 of the heat storage tanks 20 are stopped.

[0061] During operation in the auxiliary state described above, the heat medium TM3 heated by an auxiliary heat source (not shown) flows into the auxiliary heat exchanger 73, and the heat medium TM2 circulates between the auxiliary heat exchanger 73 and the heat utilization device 91. In the auxiliary heat exchanger 73, heat exchange occurs between the heat medium TM2 and the heat medium TM3, and the temperature of the heat medium TM2 increases before it flows out of the auxiliary heat exchanger 73. The heat medium TM2 flowing out of the auxiliary heat exchanger 73 is supplied to the heat utilization device 91 by the heat dissipation pump 58. At this time, the control device 80 receives a measurement value from the auxiliary thermometer 85 and controls the discharge flow rate of the heat dissipation pump 58 using an inverter so that the measurement value on the auxiliary thermometer 85 becomes a predetermined value (typically the second predetermined temperature described above). The heat medium TM2 supplied to the heat utilization device 91 has its temperature reduced as heat is utilized in the heat utilization device 91, and then leaves the heat utilization device 91 and flows back into the auxiliary heat exchanger 73. By operating in the auxiliary state in this manner, even if it becomes impossible to supply heat from the heat storage tank 20, the heat utilization device 91 can continue to operate.

[0062] (Driving in a free-for-all state) The release state operation is typically an operation in which heat collected by the heat collector 10 is released to the outside of the system when the heat storage tank 20 becomes full during the heat storage operation. When the release state operation in this embodiment is performed alone, as shown in FIG. 3 , the eighth two-way valve 68 and the ninth two-way valve 69 are open, and the other two-way valves 61 to 67 are closed. The first three-way valve 71 connects the heat storage tank supply pipe 54 and the heat radiation supply pipe 55, and its valve element is oriented to block the flow path to the second heat extraction return pipe 47. The second three-way valve 72 connects the upstream and downstream sides of the heat radiation supply pipe 55, and its valve element is oriented to block the flow path to the auxiliary supply pipe 75. The first heat extraction pump 45 and the second heat extraction pump 48 are each operated by inverter control, and the heat radiation pump 58 is stopped. The auxiliary pump 74 is operating. The motors 28 of the heat storage tanks 20 are stopped.

[0063] During operation in the above-described release state, the heat medium TM1 circulates between the heat collector 10 and the heat extraction heat exchanger 41, just as during heat storage operation. Even during operation in the release state, the discharge flow rate of the first heat extraction pump 45 may be controlled so that the temperature of the heat medium TM1 flowing out of the heat collector 10 is constant. The heat medium TM2 is circulated between the heat extraction heat exchanger 41 and the auxiliary heat exchanger 73 by the second heat extraction pump 48. The heat medium TM3 also flows into and out of the auxiliary heat exchanger 73 by the auxiliary pump 74. At this time, the heat medium TM3 flowing into the auxiliary heat exchanger 73 has a lower temperature than the heat medium TM2 flowing into the auxiliary heat exchanger 73. During operation in the release state, the heat medium TM2 receives heat from the heat medium TM1 in the heat extraction heat exchanger 41 and is transported to the auxiliary heat exchanger 73, where it dissipates heat to the heat medium TM3, lowering its temperature, and then flows back into the heat extraction heat exchanger 41. By operating in the release state in this way, even when the solar heat collected by the heat collector 10 cannot be transported to the heat storage tank 20, it can be properly processed.

[0064] As described above, the thermal storage system 1 according to this embodiment has the following advantages. During the thermal storage operation, the transport mechanism is controlled to cause the heat medium TM2 at a first predetermined temperature to flow into the thermal storage tank 20. This prevents the liquefied thermal storage material 26 from solidifying due to the relatively low-temperature heat medium TM2, allowing efficient storage of heat in the latent heat storage material. Furthermore, since the transport mechanism is controlled according to the measurement value of the pyranometer 81, changes in the amount of solar radiation can be reflected in the control without delay, preventing the heat medium TM2 at a temperature lower than the first predetermined temperature from flowing into the thermal storage tank 20. Furthermore, during the heat dissipation operation, the supply mechanism is controlled to cause the heat medium TM2 at a second predetermined temperature to flow into the heat utilization device 91. This allows the heat collected from solar heat, which has a variable extractable heat quantity, to be supplied to the heat utilization device 91 as a stable amount of heat. Therefore, the thermal storage system 1 according to this embodiment can efficiently and uniformly exchange heat at a relatively low temperature in the thermal storage tank 20. This allows stable heat exchange to be achieved simply by monitoring the temperatures of the heat media TM1 and TM2.

[0065] [others] In the above explanation, the heat collection device is a solar collector 10 that collects solar heat, but it may also be a device (for example, a waste heat heat exchanger) that collects heat generated from a heat source whose heat output changes (and therefore the amount of heat that can be collected changes), such as factory waste heat.

[0066] In the above description, the first heat storage tank 20A and the second heat storage tank 20B have the same configuration. However, the heat storage material 26 of the first heat storage tank 20A and the heat storage material 26 of the second heat storage tank 20B may have different melting points. In this way, it is possible to preferentially use the heat storage tank 20 that stores heat depending on the amount of heat that can be collected by the heat collection device such as the heat collector 10, thereby improving heat storage efficiency. Furthermore, it is possible to supply the heat medium TM2 at an appropriate temperature to different heat utilization devices 91 that require different temperatures of the heat medium TM2. Furthermore, in the above description, two heat storage tanks 20, the first heat storage tank 20A and the second heat storage tank 20B, are provided. However, one heat storage tank 20 may be provided, or three or more heat storage tanks 20 may be provided to increase the heat storage capacity. When three or more heat storage tanks 20 are provided, it is preferable that the heat storage tanks 20 are connected in parallel. Furthermore, the heat storage materials 26 of the heat storage tanks 20 may be the same or may have different melting points.

[0067] In the above description, the heat storage tank 20 is arranged so that the axis of the heat storage tank 20 (the axis of the heat transfer cylinder 21) extends in the vertical direction, and the upper end face of the heat transfer cylinder 21 is open. However, the heat storage tank 20 may be arranged so that the axis of the heat storage tank 20 extends in a direction other than the vertical direction (for example, the horizontal direction). Furthermore, although the heat storage tank return pipe 53 and the heat storage tank supply pipe 54 are arranged so that the heat medium TM2 flows in and out of one end face of the heat transfer cylinder 21 of the heat storage tank 20, the heat storage tank return pipe 53 and the heat storage tank supply pipe 54 may be arranged so that the heat medium TM2 flows in from one end face of the heat transfer cylinder 21 and flows out from the other end face.

[0068] In the above explanation, the primary heat extraction heat exchanger 41 is provided between the heat collector 10 and the heat storage tank 20, but when the same heat medium flows into the heat collector 10 and the heat storage tank 20, the primary heat extraction heat exchanger 41 may be omitted and the heat medium may be directly supplied from the heat collector 10 to the heat storage tank 20. When the heat medium is directly supplied from the heat collector 10 to the heat storage tank 20, the heat collector 10 and the heat storage tank 20 are directly connected by piping, and only one pump is required to circulate the heat between the heat collector 10 and the heat storage tank 20. Furthermore, in the above explanation, the heat medium TM2 is directly supplied from the heat storage tank 20 to the heat utilization device 91, but a heat exchanger may be provided between them to indirectly supply the heat held in the heat medium. By providing a heat exchanger between the heat storage tank 20 and the heat utilization device 91, a heat medium of a different fluid type from the heat medium TM2 flowing in and out of the heat storage tank 20 can be made to flow in and out of the heat utilization device 91, and an appropriate type of fluid can be used as the heat medium according to the characteristics of the heat utilization device 91.

[0069] In the above description, the blades 25 are fixed and the heat transfer cylinder 21 rotates around its axis in the heat storage tank 20. However, the heat transfer cylinder 21 may be fixed and the blades 25 may rotate around the outer surface of the heat transfer cylinder 21, or they may be configured to rotate in opposite directions. In other words, it is sufficient that the heat transfer cylinder 21 is configured to be movable relative to the blades 25 so that the solid heat storage material 26 deposited on the outer surface of the heat transfer cylinder 21 can be peeled off.

[0070] In the above explanation, an in-cylinder thermometer 86 is provided and the measurement value of the in-cylinder thermometer 86 is used to determine whether the tank is fully charged or not. However, the amount of heat stored in the heat storage tank 20 may be estimated from a value obtained by taking into account the amount of heat dissipated in the heat storage tank 20 relative to the amount of heat supplied to the heat recovery heat exchanger 41 (the temperature difference between the inlet and outlet of the heat medium TM2 x flow rate).

[0071] In the above explanation, the first heat extraction pump 45 and the second heat extraction pump 48 are inverter-controlled to adjust the heat amounts of the heat transfer media TM1 and TM2, respectively, but the amount of heat transfer may also be adjusted by other adjustment means. For example, a bypass pipe that bypasses the heat transfer heat exchanger 41 may be provided between the first heat extraction supply pipe 43 and the first heat extraction return pipe 44, and a three-way or two-way valve may be disposed in an appropriate position to adjust the valve opening to adjust the flow rate of the heat transfer media TM1 flowing through the heat extraction heat exchanger 41, thereby adjusting the amount of heat transfer. The same applies to the systems of the second heat extraction supply pipe 46 and the second heat extraction return pipe 47. The same applies to the system of the heat dissipation pump 58.

[0072] In the above explanation, examples of applications of the heat utilization device 91 include a hot water heater for heating the interior of an agricultural greenhouse and an absorption-type hot and cold water generator. When an absorption-type hot and cold water generator is used as the heat utilization device 91, not only an absorption hot and cold water generator that uses only high-temperature water that retains collected solar heat as a heat source, but also a so-called solar absorption hot and cold water generator may be used. A solar absorption hot and cold water generator is an absorption hot and cold water generator that preferentially uses solar heat but uses gas or oil as a heat source when there is a shortage of heat due to a decrease in solar radiation. When a solar absorption hot and cold water generator is used as the heat utilization device 91, gas or oil can function as a backup heat source, so that in the thermal storage system 1, the configuration of a backup system such as the auxiliary heat exchanger 73 and its surrounding piping can be omitted.

[0073] In the above explanation, a solar radiation-related physical quantity measuring instrument that detects a physical quantity that changes in response to a change in the amount of solar radiation is referred to as a pyranometer. Here, the "physical quantity that changes in response to a change in the amount of solar radiation" refers to a physical quantity that changes without delay when the amount of solar radiation changes, and includes the solar radiation itself and the heat medium pressure in the solar thermal collector system. Therefore, the solar radiation-related physical quantity measuring instrument may be a pressure gauge provided in the system of the heat medium TM1 that flows through the solar collector 10 (heat collecting device).

[0074] In the above description, the discharge flow rate of the first heat extraction pump 45 is adjusted to increase or decrease the flow rate of the heat medium TM1 flowing through the solar collector 10 (heat extracting device) according to the measurement value of the pyranometer 81, so that the measurement value of the heat extraction thermometer 82 becomes a predetermined value (e.g., 72°C). However, a second temperature detector may be provided to detect the temperature of the heat medium at the outlet of the heat extracting device, and the first heat extraction pump 45 (transport mechanism) may be controlled based on the value detected by the second temperature detector. Here, the heat medium at the outlet of the heat extracting device refers to the heat medium immediately before or immediately after exiting the heat extracting device, where "immediately before" or "immediately after" refers to a range in which the heat medium has a temperature that can be considered substantially the same as the outlet temperature of the heat extracting device. In this case, the heat extraction thermometer 82 may be disposed at the outlet of the heat extracting device and used as a second temperature detector. Controlling the first heat extraction pump 45 (transport mechanism) based on the value detected by the second temperature detector allows for inexpensive construction of a system configuration. However, from the viewpoint of quickly increasing or decreasing the flow rate of the heat medium in response to changes in the amount of solar radiation, it is preferable to increase or decrease the flow rate of the heat medium in accordance with the measurement value of the solar radiation-related physical quantity measuring instrument. [Explanation of symbols]

[0075] 1. Thermal storage system 10 Heat collector (heat collecting equipment) 20 Heat storage tank 20A 1st heat storage tank 20B 2nd heat storage tank 21 Heat transfer cylinder 23 Outer cylinder 25 Feather 26 Heat storage material 27 Moving mechanism 45 First heat extraction pump (transport mechanism) 48 Second heat extraction pump (transport mechanism) 58 Heat dissipation pump (supply mechanism) 80 Control device 81 Pyranometer (instrument for measuring physical quantities related to solar radiation) 84 Radiation thermometer 86 Cylinder thermometer (first temperature detector) 91 Heat utilization equipment TM1, TM2, TM3 Thermal Media

Claims

1. a heat extraction device that extracts heat generated from a heat source whose extractable heat quantity varies and supplies the extracted heat to a heat medium; a heat storage tank having a heat storage material that undergoes a phase change between solid and liquid, and performing heat exchange between the heat medium supplied directly or indirectly from the heat extracting device and the heat storage material; a transport mechanism that transports the heat medium from the heat extracting device to the heat storage tank, the transport mechanism being capable of adjusting a flow rate of the heat medium being transported; a control device that controls the transport mechanism to increase or decrease the flow rate of the heat medium flowing through the heat extracting device so that the heat medium, which retains the heat supplied from the heat extracting device, reaches a first predetermined temperature that is equal to or higher than the melting point of the heat storage material when it flows into the heat storage tank; The heat collecting device is a solar heat collector that collects solar heat, The solar energy collector further includes a pipe constituting a system of the heat medium flowing through the solar energy collector, and a pressure gauge for detecting the pressure inside the pipe, the control device controls the conveying mechanism based on a change in pressure inside the piping due to a change in the amount of solar radiation detected by the pressure gauge. Heat storage system.

2. a supply mechanism that directly or indirectly supplies the heat medium that retains the heat released from the heat storage tank to a heat utilization device that utilizes the heat stored in the heat storage tank; The heat storage tank is a heat transfer cylinder through which the heat medium flows; an outer cylinder arranged around the heat transfer cylinder with a predetermined space therebetween, the outer cylinder holding the heat storage material in the space between the outer surface of the heat transfer cylinder and the inner surface of the outer cylinder; a blade that is in close proximity to or in sliding contact with the outer surface of the heat transfer cylinder; a movement mechanism that moves the heat transfer cylinder relative to the blades, the control device controls at least one of the supply mechanism and the movement mechanism so that the heat medium flowing from the heat storage tank toward the heat utilization device has a second predetermined temperature. The thermal storage system according to claim 1 .

3. the heat storage tank has a first temperature detector arranged at a position of the heat storage material held in the space where the change of the heat storage material from solid to liquid is finalized when the heat storage material receives heat from the heat medium, The control device controls the transport mechanism to stop the flow of the heat medium, which retains the heat supplied from the heat extracting device, into the heat storage tank when the temperature detected by the first temperature detector reaches a third predetermined temperature that is equal to or higher than the melting point of the heat storage material. The thermal storage system according to claim 2 .

4. an auxiliary heat exchanger that exchanges heat between the heat medium and an external heat medium that is a heat medium from outside the system; a valve for switching the heat medium supplied directly or indirectly from the heat extracting device between flowing into the heat storage tank and flowing into the auxiliary heat exchanger; the heat storage tank has a first temperature detector arranged at a position of the heat storage material held in the space where the change of the heat storage material from solid to liquid is finalized when the heat storage material receives heat from the heat medium, When the temperature detected by the first temperature detector reaches a third predetermined temperature equal to or higher than the melting point of the heat storage material, the control device controls the valve so that the heat medium, which retains the heat supplied from the heat extracting device, flows into the auxiliary heat exchanger without flowing into the heat storage tank. The thermal storage system according to claim 2 .

5. a second temperature detector for detecting the temperature of the heat medium at the outlet of the heat extracting device; the control device controls the transport mechanism based on the value detected by the second temperature detector. The thermal storage system according to claim 1 .

6. The heat storage tank includes a first heat storage tank and a second heat storage tank separate from the first heat storage tank. The heat storage system according to any one of claims 1 to 5.

7. In the first heat storage tank, the heat storage material is a first heat storage material, The second heat storage tank contains a heat storage material having a melting point different from that of the first heat storage material. The thermal storage system according to claim 6.

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