Solar thermal collection system

Abstract

The solar thermal system (1) comprises: a solar thermal panel (2) having a non-insulated part (2c) for convective heat transfer between itself and the surrounding air, which transfers radiant heat from sunlight and convective heat from the surrounding air to a heat carrier (M); a heat carrier circulation line (4) for transporting the heat carrier (M) from a heat carrier tank (3) for storing the heat carrier (M) to the solar thermal panel (2) and for transporting the heat carrier (M) from the solar thermal panel (2) to the heat carrier tank (3); a heat carrier flow control mechanism (5) for switching whether the flow of the heat carrier (M) along the heat carrier circulation line (4) is possible and for adjusting the flow rate of the heat carrier (M); and a control device (9). The control device (9) measures the amount of radiative heat input (Q1) to the solar collector panel (2), measures the amount of convective heat transfer (Q2) between the solar collector panel (2) and the surrounding air, and controls the heat carrier flow control mechanism (5) based on the amount of radiative heat input (Q1) and the amount of convective heat transfer (Q2).

Description

Technical Field

[0001] This disclosure relates to solar thermal collection systems. Background Technology

[0002] Patent Document 1 discloses a solar collector control device that supplies a heat carrier from a heat storage tank to a collector, heats the heat carrier with solar heat in the collector, and then returns the heat carrier from the collector to the heat storage tank. The device switches the operation of the pump that circulates the heat carrier according to the internal temperature conditions of the collector and the heat storage tank. For example, the pump operates when the temperature of the collector is higher than the temperature of the heat storage tank by a predetermined temperature, or when the temperature of the heat carrier returning to the piping section is higher than the temperature of the heat storage tank by a predetermined temperature.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 58-102062. Summary of the Invention

[0004] The problem that the invention aims to solve In conventional solar thermal systems as described above, the focus in the panel-shaped collector is on transferring radiant heat from sunlight to the heat carrier. However, there is room for improvement regarding the heat obtained from the collector.

[0005] The subject of this disclosure is to improve the heat obtained by solar thermal collectors.

[0006] Methods for solving problems One aspect of this disclosure provides a solar thermal collection system comprising: a solar thermal collection panel having a hollow portion for allowing a heat carrier to circulate, a light-receiving portion for receiving sunlight, and a non-insulated portion for convective heat transfer between the panel and the surrounding air, transferring radiant heat from the sunlight and convective heat from the surrounding air to the heat carrier; a heat carrier tank for storing the heat carrier; a heat carrier circulation circuit for transporting the heat carrier from the heat carrier tank to the solar thermal collection panel and from the solar thermal collection panel to the heat carrier tank; a heat carrier circulation control mechanism for switching whether the heat carrier can circulate along the heat carrier circulation circuit and adjusting the flow rate of the heat carrier; and a control device; wherein the control device measures the amount of radiant heat input to the solar thermal collection panel, measures the amount of convective heat transfer between the solar thermal collection panel and the surrounding air, and controls the heat carrier circulation control mechanism based on the amount of radiant heat input and the amount of convective heat transfer.

[0007] Here, solar collector panels typically employ insulation to prevent convective heat transfer with the surrounding air. In contrast, according to the aforementioned structure, the solar collector panel actively includes a non-insulated section designed to facilitate convective heat transfer with the surrounding air. Therefore, in the solar collector panel, not only radiative heat from sunlight but also convective heat from the surrounding air can be transferred to the heat carrier, increasing the amount of heat gained in the solar collector panel. Furthermore, the flow of the heat carrier can be switched based on the radiative heat input and the convective heat transfer, or the flow rate of the heat carrier can be adjusted. Thus, optimization of heat recovery by the heat carrier can be achieved.

[0008] Alternatively, when the aforementioned convective heat is transferred from the aforementioned solar collector panel to the aforementioned surrounding air, the aforementioned convective heat transfer becomes negative; when the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is less than the absolute value of the aforementioned convective heat transfer, the aforementioned heat carrier flow control mechanism controls the aforementioned heat carrier to stop the supply of the aforementioned heat carrier to the aforementioned solar collector panel.

[0009] Here, when a non-insulated part is provided on the solar collector panel to obtain convective heat from the surrounding air, the dissipation of convective heat from the solar collector panel to the surrounding air is also considered, depending on the situation. In contrast, according to the above structure, if the amount of convective heat transferred from the solar collector panel to the surrounding air exceeds the amount of radiative heat input received by the solar collector panel, the supply of heat carrier stops. Therefore, cooling of the heat carrier can be prevented, and optimization of heat recovery by the heat carrier can be achieved.

[0010] Alternatively, when the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is greater than or equal to the absolute value of the aforementioned convective heat transfer, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to supply the aforementioned heat carrier to the aforementioned solar collector panel.

[0011] According to the above structure, when the convective heat transfer from the solar collector panel to the surrounding air is less than the radiative heat input received by the solar collector panel, the heat carrier circulates. Therefore, the heat carrier can be heated using the heat obtained from the solar collector panel.

[0012] Alternatively, when the aforementioned convective heat transfer is positive, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to supply the aforementioned heat carrier to the aforementioned solar collector panel.

[0013] According to the above structure, the heat carrier circulates when convective heat enters the solar collector panel from the surrounding air. Therefore, the heat carrier can be heated using the heat obtained from the solar collector panel.

[0014] Alternatively, the aforementioned solar thermal collection system may also include a solar radiation meter for measuring the total solar radiation throughout the day; the aforementioned control device measures the total solar radiation throughout the day as the heat per unit time based on the total solar radiation measured by the aforementioned solar radiation meter and the surface area of ​​the aforementioned light-receiving part.

[0015] Based on the above structure, the radiative heat input can be measured sequentially as the heat per unit time, based on the measurement results of the total daily solar radiation, which may vary at any moment. Since the flow of the heat carrier can be switched or the flow rate of the heat carrier can be adjusted based on such radiative heat input, the control is more responsive to environmental changes such as cloud cover variations, and it is easier to optimize the heat recovery performed by the heat carrier.

[0016] Alternatively, the aforementioned solar thermal system may also include: an external gas temperature sensor for measuring the temperature of the air surrounding the solar thermal collector panel; and a panel temperature sensor for measuring the temperature on the side of the solar thermal collector panel; the aforementioned control device measures the convective heat transfer as heat per unit time based on the temperature difference measured by the external gas temperature sensor and the panel temperature sensor, the outer surface area of ​​the non-insulated part, and the convective heat transfer coefficient of the non-insulated part.

[0017] Based on the above structure, the convective heat transfer can be measured sequentially as the heat per unit time, based on the measurement results of the temperature difference, which may change at any moment. Since the flow of the heat carrier can be switched or the flow rate of the heat carrier can be adjusted based on such convective heat transfer, the control's ability to follow environmental changes such as temperature fluctuations is improved, and the heat recovery by the heat carrier can be easily optimized.

[0018] Alternatively, the aforementioned panel temperature sensor may consist of at least one surface temperature sensor that measures the surface temperature of the aforementioned non-insulated part, an inlet temperature sensor that measures the temperature near the inlet of the aforementioned hollow part, and an outlet temperature sensor that measures the temperature near the outlet of the aforementioned hollow part.

[0019] Based on the above structure, the panel temperature can be measured with good accuracy.

[0020] Alternatively, the aforementioned heat transfer tank may include a first heat transfer tank and a second heat transfer tank that is separate from the first heat transfer tank; the aforementioned heat transfer circulation line may include an inflow line that transports the aforementioned heat transfer material from the aforementioned first heat transfer tank to the aforementioned hollow section, and an outflow line that transports the aforementioned heat transfer material from the aforementioned hollow section to the aforementioned second heat transfer tank.

[0021] According to the above structure, since the temperature of the heat carrier supplied to the solar collector panel is lower than the temperature of the solar collector panel during the heat collection time, the temperature difference can be maintained at a large level. Therefore, the heat transfer from the solar collector panel to the heat carrier can be maintained at a high level. As a result, the heat storage in the second tank obtained by the solar collector panel can be increased.

[0022] Alternatively, the aforementioned heat transfer fluid circulation line may also include a return line branching off from the aforementioned outflow line to send the aforementioned heat transfer fluid back to the aforementioned first heat transfer fluid tank; the aforementioned heat transfer fluid flow control mechanism includes a direction switching mechanism, which switches between the state of transporting the aforementioned heat transfer fluid to the aforementioned second heat transfer fluid tank via the aforementioned outflow line and the state of sending the aforementioned heat transfer fluid back to the aforementioned first heat transfer fluid tank via the aforementioned return line.

[0023] In the above structure, when the heat transfer medium returns from the first heat transfer medium tank to the first heat transfer medium tank via the solar collector panel, the temperature of the heat transfer medium in the first heat transfer medium tank can be increased, resulting in a high-temperature heat transfer medium. Furthermore, when the heat transfer medium is transported from the first heat transfer medium tank to the second heat transfer medium tank via the solar collector panel, although the temperature of the heat transfer medium does not increase compared to the case where it is returned to the first heat transfer medium tank, the heat collection capacity is maximized.

[0024] Alternatively, the aforementioned heat transfer tank may be a layered type with an outlet at the bottom and an inlet at the top; the aforementioned heat transfer circulation line may include an inflow line connecting the aforementioned outlet of the aforementioned heat transfer tank to the aforementioned hollow portion, and an outflow line connecting the aforementioned hollow portion to the aforementioned inlet of the aforementioned heat transfer tank.

[0025] Based on the above structure, a high heat collection level can be maintained without increasing the number of heat transfer tanks.

[0026] Invention Effects According to this disclosure, it is possible to improve the heat obtained by solar thermal collector panels. Attached Figure Description

[0027] Figure 1 This is a schematic diagram showing the overall structure of the solar thermal collection system according to the first embodiment.

[0028] Figure 2A This is a 3D view of a solar collector panel.

[0029] Figure 2B This is an exploded 3D view of a solar collector panel.

[0030] Figure 2C This is a cross-sectional view of a solar collector panel.

[0031] Figure 3This is a schematic diagram showing the main parts of the solar thermal collection system according to the first embodiment.

[0032] Figure 4 It is a flowchart representing the process performed by the control device.

[0033] Figure 5 It is a graph showing the time-varying changes in radiant heat input, external gas temperature, and panel temperature.

[0034] Figure 6 This is a schematic diagram of the solar thermal collection system according to the second embodiment.

[0035] Figure 7 This is a schematic diagram of the solar thermal collection system according to the third embodiment.

[0036] Figure 8 This is a schematic diagram of the solar thermal collection system according to the fourth embodiment. Detailed Implementation

[0037] Hereinafter, the embodiments will be described with reference to the accompanying drawings. Furthermore, the same or corresponding elements are given the same reference numerals throughout the drawings, and repetition of detailed descriptions is omitted.

[0038] (First Embodiment) Reference Figure 1 The solar thermal system 1 of the first embodiment includes a solar thermal panel 2, a heat carrier tank 3, a heat carrier circulation line 4, and a heat carrier flow control mechanism 5.

[0039] The solar collector panel 2 is a flat plate, forming a flow path for the liquid heat carrier M to circulate. The heat carrier tank 3 stores the heat carrier M. The heat carrier M is, for example, water. However, a liquid other than water can also be used as the heat carrier M, as in antifreeze with ethylene glycol as its main component.

[0040] In this embodiment, the heat carrier tank 3 is a single unit. The heat carrier circulation line 4 includes an inflow line 4a that transports the heat carrier M from the heat carrier tank 3 to the solar collector panel 2, and an outflow line 4b that transports the heat carrier M from the solar collector panel 2 to the heat carrier tank 3.

[0041] The heat transfer tank 3 has an insulated structure, which can maintain the temperature of the heat transfer medium M in the heat transfer tank 3 at the required temperature regardless of the ambient temperature. The inflow line 4a and the outflow line 4b are composed of piping components such as metal or resin pipes. The piping components may also have an insulated structure.

[0042] The heat transfer fluid flow control mechanism 5 performs at least one of the following: switching whether the heat transfer fluid M can flow along the heat transfer fluid circulation line 4, and adjusting the flow rate of the heat transfer fluid M along the heat transfer fluid circulation line 4. In this embodiment, the heat transfer fluid flow control mechanism 5 is configured to be able to switch and adjust both.

[0043] The heat transfer fluid flow control mechanism 5 may include a pump 5a that pressurizes the heat transfer fluid M along the heat transfer fluid circulation line 4, and a valve 5b clamped on the heat transfer fluid circulation line 4. In the illustrated example, the pump 5a and valve 5b are clamped on the inflow line 4a, but the pump 5a may also be located inside the heat transfer fluid tank 3, and the valve 5b may also be clamped on the outflow line 4b.

[0044] In this embodiment, as an example, pump 5a is a constant-capacity type, and valve 5b is a flow regulating valve. The flowability of the heat transfer fluid M is switched by changing the operating state and the stopped state of pump 5a. The flow rate of the heat transfer fluid M is adjusted by adjusting the opening degree of valve 5b. However, this is just one example; when valve 5b is an on / off valve, the flowability of the heat transfer fluid M can be switched by changing the open and closed states of valve 5b. When pump 5a is a variable-capacity type, the ejection quantity and thus the flow rate of the heat transfer fluid M can be adjusted by adjusting the capacity of pump 5a.

[0045] Pump 5a pumps the heat transfer medium M from the heat transfer medium tank 3 to the solar collector panel 2 via inflow line 4a. As the heat transfer medium M flows through the interior of the solar collector panel 2, it is heated by the heat collected within the panel. If the heat transfer medium M flows out of the solar collector panel 2, it is transported back to the heat transfer medium tank 3 via outflow line 4b. Thus, warm water is stored in the heat transfer medium tank 3.

[0046] Next, refer to Figures 2A to 2C The structure of the solar collector panel 2 will be described below. The solar collector panel 2 has a panel body 11, a first manifold 12, a second manifold 13, an inlet 14, and an outlet 15.

[0047] The panel body 11 is made of extruded aluminum alloy. The preferred aluminum alloy is the 1000 series, which has excellent thermal conductivity, or the 6000 series, which has both excellent thermal conductivity and strength.

[0048] The panel body 11 has a first main wall 11a, a second main wall 11b, and a pair of side walls 11c. The first main wall 11a, the second main wall 11b, and the pair of side walls 11c form a long, wide, and low-height angled tube, with openings at both ends in the longitudinal direction. This longitudinal direction is the extrusion direction. The first main wall 11a is a rectangular flat plate. Its long side extends in the longitudinal direction of the panel body 11, its short side extends in the width direction of the panel body 11, and its thickness direction corresponds to its height direction. The pair of side walls 11c are erected from the two side edges of the first main wall 11a. The second main wall 11b is a flat plate of the same shape as the first main wall 11a, arranged parallel to the first main wall 11a, and completely overlaps the first main wall 11a when viewed in the thickness direction, connecting the ends of the pair of side walls 11c to each other. These four walls define wide and low-height rectangular openings at both ends in the longitudinal direction.

[0049] The panel body 11 has a plurality of partitions 11d. The plurality of partitions 11d extend parallel to the side walls 11c between a pair of side walls 11c, connecting the inner surfaces of the first main wall 11a and the second main wall 11b to each other. With the help of the partitions 11d, the space surrounded by the aforementioned four walls is divided into a plurality of hollow portions 2a arranged in the width direction.

[0050] In the example shown, there are six partition walls 11d and seven hollow sections 2a, one more than the number of partition walls 11d, but the number of hollow sections 2a can be varied appropriately. Each hollow section 2a has a rectangular cross-section. By using extrusion molding, such a structure with multiple closed cross-sections or multiple hollow sections 2a can be manufactured integrally and continuously. In the example shown, the first main wall 11a, the second main wall 11b, and the pair of side walls 11c are flat, but as long as they have hollow sections inside, they can also be non-flat and have irregularities, and multiple protrusions (fins) can be provided on at least one side of the first main wall 11a, the second main wall 11b, and the pair of side walls 11c. By providing irregularities and fins, the light-receiving area and the contact area with air are increased, thereby increasing the radiative heat input and convective heat transfer.

[0051] Each hollow section 2a has openings at both ends along its length. The first manifold 12 closes the opening at one end of the hollow section 2a. The second manifold 13 closes the opening at the other end of the hollow section 2a. Both the first manifold 12 and the second manifold 13 close all the openings of the multiple hollow sections 2a together.

[0052] The first manifold 12 has a cover plate 12a, a peripheral wall 12b extending from the periphery of the cover plate 12a, and an internal space 12c surrounded by the cover plate 12a and the peripheral wall 12b. The internal space 12c is open on the side opposite to the cover plate 12a. The cross-section of the internal space 12c (the cross-section of the inner peripheral surface of the peripheral wall 12b) has the same shape as the cross-section of the outer peripheral surface of the panel body 11 (in this embodiment, it is rectangular). The first manifold 12 abuts against one end of the panel body 11 and is liquid-tightly joined to the panel body 11.

[0053] The same applies to the other end in the longitudinal direction. The second manifold 13, like the first manifold 12, has a cover plate 13a, a peripheral wall 13b, and an internal space 13c, and is also attached to the other end in the longitudinal direction of the panel body 11, just like the first manifold 12.

[0054] Inlet 14 and outlet 15 are located in the first manifold 12 or the second manifold 13. Inlet 14 is connected to inflow line 4a (see reference). Figure 1 and Figure 3 Connecting outlet 15 to outflow line 4b (refer to...) Figure 1 and Figure 3 The inlet 14 is cylindrical or pipe-connected manifold, and the inflow line 4a, as a piping component, is liquid-tightly connected to the inlet 14. The same applies to the outlet 15 and the outflow line 4b.

[0055] In this embodiment, a single inlet 14 is provided in the first manifold 12, and a single outlet 15 is provided in the second manifold 13. The inlet 14 and outlet 15 pass through corresponding cover plates 12a and 13a. The heat carrier M flows into the internal space 12c of the first manifold 12 through the inlet 14, and then branches from the internal space 12c into multiple hollow sections 2a. The heat carrier M merges from the multiple hollow sections 2a into the internal space 13c of the second manifold 13, and then flows out from the internal space 13c through the outlet 15.

[0056] Thus, the heat carrier M flows from one side to the other along the length direction via the solar collector panel 2. The heat carrier M flows through the hollow portion 2a in a state that fills the hollow portion 2a, that is, in contact with the wall and inner surface of the panel body 11 that defines the hollow portion 2a.

[0057] Reference Figure 3The solar collector panel 2 has a light-receiving portion 2b for receiving sunlight. The solar collector panel 2 transfers radiant heat from sunlight to the heat carrier M. Furthermore, the solar collector panel 2 actively has a non-insulated portion 2c intended for convective heat transfer with the surrounding air. When convective heat is transferred from the surrounding air to the solar collector panel 2, the solar collector panel 2 transfers this convective heat to the heat carrier M. Radiant heat and convective heat are transferred to the heat carrier M via solid-state heat transfer within the panel body 11, thereby heating the heat carrier M.

[0058] The heat Q acquired by the solar collector panel 2 per unit time can be defined as the sum of the radiative heat input Q1 and the convective heat transfer Q2 (Q = Q1 + Q2). The heat carrier M is heated from the inlet 14 to the outlet 15 by a temperature rise corresponding to the acquired heat Q and the flow rate of the heat carrier M.

[0059] "Radiant heat input Q1" can be defined as the amount (W) of radiant heat input per unit time to the solar collector panel 2 (especially its light-receiving part 2b) by sunlight. Radiant heat input Q1 is expressed by the following formula (1).

[0060] Q1=αWsunAsun ……(1) Here, α is the emissivity (dimensionless) of the surface of the solar collector panel 2, and more specifically, the emissivity of the light-receiving part 2b. Wsun is the total daily solar radiation (W / m²). 2 Asun is the light-receiving area (m²) of the solar collector panel 2. 2 More specifically, it refers to the surface area of ​​the light-receiving part 2b (hereinafter simply referred to as the light-receiving area Asun).

[0061] The light-receiving part 2b is all or part of the outer surfaces of the first main wall 11a, the second main wall 11b, a pair of side walls 11c, the first manifold 12, and the second manifold 13. The surface of the light-receiving part 2b is painted black. As a result, the emissivity α of the light-receiving part 2b becomes close to 1, increasing the heat collection ratio of the solar collector panel 2. Since the emissivity of aluminum alloy is from 10... -2 Up to 10 -1 The value is on the order of magnitude, so even though the main body of the panel 11 is made of aluminum alloy, the effect brought by the coating is significant. In addition, the heat collection ratio is a dimensionless value obtained by dividing the heat energy per unit area obtained by solar radiation by the total solar radiation Wsun. The closer it is to 1, the higher the heat collection efficiency.

[0062] "Convective heat transfer Q2" can be defined as the amount (W) of convective heat exchanged per unit time between the surrounding air and the solar collector panel 2 (especially its non-insulated part 2c). Convective heat transfer Q2 is expressed by the following formula (2).

[0063] Q2=μ(Tair-Tp)Ap……(2) Here, μ is the convective heat transfer coefficient of the solar collector panel 2 (W / K·m). 2 More specifically, it is the convective heat transfer coefficient of the non-insulated part 2c. Tair is the temperature (K) of the air surrounding the solar collector panel 2 (hereinafter referred to as the external gas temperature Tair). Tp is the temperature (K) of the side of the solar collector panel 2 (hereinafter referred to as the panel temperature Tp). Ap is the outer surface area (m²) of the solar collector panel 2. 2 More specifically, it refers to the outer surface area of ​​the non-insulated part 2c (hereinafter simply referred to as the outer surface area Ap).

[0064] The heat carrier M is in contact with the inner surface of the wall defining the hollow portion 2a. The inner surfaces of the first main wall 11a, the second main wall 11b, the pair of side walls 11c, the first manifold 12, and the second manifold 13 are substantially entirely in contact with the heat carrier M, and their outer surfaces are substantially entirely in contact with the surrounding air. In this embodiment, it goes without saying that no heat-insulating material is provided on either their inner or outer surfaces. Therefore, the four walls constituting the panel body 11 and the manifolds 12 and 13 substantially entirely function as the non-insulated portion 2c.

[0065] As shown in equation (2) above, the convective heat transfer Q2 is directly proportional to the temperature difference between the external gas temperature Tair and the panel temperature Tp. When the external gas temperature Tair is higher than the panel temperature Tp, the convective heat transfer Q2 becomes positive. Convective heat is transferred from the surrounding air to the solar collector panel 2 (especially its non-insulated part 2c). Conversely, when the panel temperature Tp is higher than the external gas temperature Tair, the convective heat transfer Q2 becomes negative. Convective heat is transferred from the solar collector panel 2 (especially its non-insulated part 2c) to the surrounding air.

[0066] The emissivity α, the light-receiving area Asun, the convective heat transfer coefficient μ, and the external surface area Ap are determined according to the design specifications of the solar collector panel 2. These parameters can be treated as constants during both the design and operational phases of the solar collector panel 2. However, the total daily solar irradiance Wsun, the external gas temperature Tair, and the panel temperature Tp change constantly. Real-time measurement of these parameters is required when calculating the radiative heat input Q1 and the convective heat transfer Q2.

[0067] Return to Figure 1The solar thermal collector system 1 also includes a sunmeter 6, an external gas temperature sensor 7, and a panel temperature sensor 8. The sunmeter 6 is located near the receiving part 2b and measures the total daily solar radiation Wsun. The external gas temperature sensor 7 is located on the exterior of the solar thermal collector panel 2 and near the solar thermal collector panel 2, and measures or detects the external gas temperature Tair. The panel temperature sensor 8 is located on the surface or inside the solar thermal collector panel 2 and measures or detects the panel temperature Tp.

[0068] The panel temperature sensor 8 is composed of at least one of a surface temperature sensor 8a, an inlet temperature sensor 8b, and an outlet temperature sensor 8c. The surface temperature sensor 8a measures the surface temperature of the solar collector panel 2 (hereinafter referred to as surface temperature Tsf), particularly the temperature of the outer surface of the non-insulated part 2c. The inlet temperature sensor 8b measures the temperature near the inlet 14 of the heat carrier M of the solar collector panel 2 (hereinafter referred to as inlet temperature Tin). The outlet temperature sensor 8c measures the temperature near the outlet 15 of the heat carrier M of the solar collector panel 2 (hereinafter referred to as outlet temperature Tout). The inlet temperature Tin can be the temperature of the inner surface of the solar collector panel 2 near the inlet 14, or it can be the temperature of the heat carrier M flowing near the inlet 14. The same applies to the outlet temperature Tout.

[0069] Alternatively, any one of the surface temperature Tsf, inlet temperature Tin, and outlet temperature Tout can be treated as the panel temperature Tp. The panel temperature Tp can also be the average of two or more of the surface temperature Tsf, inlet temperature Tin, and outlet temperature Tout. The surface temperature Tsf can also be measured at multiple points on a solar collector panel 2. In this case, the average of multiple surface temperature Tsf measurements can be treated as a single measurement result of the surface temperature Tsf.

[0070] The solar thermal collector system 1 also includes a control device 9. The control device 9 is connected to a solar transilluminator 6, an external gas temperature sensor 7, and a panel temperature sensor 8, and sequentially acquires the measurement results of these elements at a predetermined sampling period. The control device 9 is also connected to a heat carrier flow control mechanism 5, and controls the heat carrier flow control mechanism 5 based on the measurement results. In other words, the control device 9, based on the measurement results, controls whether the heat carrier M can flow along the heat carrier circulation path 4, or controls the flow rate of the heat carrier M along the heat carrier circulation path 4.

[0071] The control device 9 may include, for example, a CPU (Central Processing Unit) or MPU (Micro Processing Unit) that works with software to perform predetermined functions. The control device 9 can be composed of hardware circuits such as dedicated or reconfigurable electronic circuits designed to perform predetermined functions, or it can be composed of various semiconductor integrated circuits. Examples of various semiconductor integrated circuits include, in addition to CPUs and MPUs, microcomputers, DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and ASICs (Application Specific Integrated Circuits). Furthermore, the control device 9 may also include storage devices such as RAM (Random Access Memory) and ROM (Read Only Memory). Specifically, the control device 9 may be composed of, for example, an information processing device such as a desktop PC, a notebook PC, a workstation, or a tablet computer, or a printed circuit board with equivalent functionality.

[0072] The storage device of the control device 9 stores programs and information for performing the processes described below. Examples of information pre-stored in the storage device include the values ​​of emissivity α, light-receiving area Asun, convective heat transfer coefficient μ, and external surface area Ap.

[0073] Figure 4 This represents the process flow executed by control device 9. Control device 9 repeatedly executes the process along the illustrated flow every predetermined control cycle.

[0074] The control device 9 acquires the measurement results of the total solar radiation Wsun output from the solar radiation meter 6, the external gas temperature Tair output from the external gas temperature sensor 7, and the panel temperature Tp output from the panel temperature sensor 8 (step S1). The panel temperature Tp, as described above, can be the surface temperature Tsf itself, the inlet temperature Tin itself, the outlet temperature Tout itself, or it can be calculated based on these multiple temperatures. The control device 9 can also set the acquired measurement result as the panel temperature Tp, or it can arithmetically use the panel temperature Tp as the measurement result based on the multiple acquired measurement results.

[0075] Next, the control device 9 calculates the radiative heat input Q1 according to the above formula (1) (step S2). The emissivity α and the light-receiving area Asun in formula (1) can be read from the storage device.

[0076] Furthermore, the control device 9 calculates the convective heat transfer Q2 based on the measured temperature difference between the external gas temperature Tair and the panel temperature Tp, according to the above formula (2) (step S2). The convective heat transfer coefficient μ and the external surface area Ap, which are factors in formula (2), can be read from the storage device.

[0077] Next, the control device 9 determines whether the measured convective heat transfer Q2 is 0 or positive (step S3a). If the convective heat transfer Q2 is negative (S3a: no), it determines whether the absolute value of the radiative heat input Q1 is greater than or equal to the absolute value of the convective heat transfer Q2 (step S3b).

[0078] If the convective heat transfer Q2 is 0 or positive (S3a: Yes), the control device 9 controls the heat carrier flow control mechanism 5 to continue the flow of the heat carrier M (step S4). If the convective heat transfer Q2 is negative (S3a: No) and the absolute value of the radiant heat input Q1 is greater than or equal to the absolute value of the convective heat transfer Q2 (S3b: Yes), the process also proceeds to step S4. To ensure the continued flow of the heat carrier M, the control device 9, for example, continues the operation of the pump 5a and maintains the opening of the valve 5b at a predetermined opening or higher.

[0079] If the convective heat transfer Q2 is negative (S3a: No) and the absolute value of the radiative heat input Q1 is less than the absolute value of the convective heat transfer Q2 (S3b: No), the control device 9 controls the heat carrier flow control mechanism 5 to stop the flow of the heat carrier M (step S5). To stop the flow of the heat carrier M, the control device 9, for example, stops the pump 5a and sets the opening of the valve 5b to fully closed.

[0080] Here, the radiative heat input Q1 is proportional to the total daily solar radiation Wsun. Since the total daily solar radiation Wsun cannot be negative, the radiative heat input Q1 is also 0 or positive. If the convective heat transfer Q2 is 0 or positive (S3a: Yes), then the acquired heat Q is 0 or positive. Even if the convective heat transfer Q2 is negative, as long as the absolute value of the convective heat transfer Q2 is lower than the radiative heat input Q1 (or its absolute value) (S3b: Yes), the acquired heat Q is also positive. Thus, if the acquired heat Q is 0 or positive, the flow of heat carrier M continues (step S4).

[0081] Conversely, if the convective heat transfer Q2 is negative, and the absolute value of the convective heat transfer Q2 is higher than the radiative heat input Q1 (or its absolute value) (S3b: No), then the heat received Q is negative. In this case, if the heat carrier M passes through the solar collector panel 2, the heat carrier M may cool down. If the heat received Q is negative, the flow of heat carrier M stops (step S5), thereby preventing the cooling of heat carrier M from occurring.

[0082] Figure 5This represents the temporal changes in radiant heat input Q1, external gas temperature Tair, and panel temperature Tp from before sunrise to after sunset on a clear day. The horizontal axis represents time. The vertical axis represents heat (W) or temperature (K) per unit time with arbitrary scales.

[0083] The radiant heat input Q1 is directly proportional to the total daily solar radiation Wsun. Therefore, although the total daily solar radiation Wsun is not shown in the diagram, it changes over time in the same way as the radiant heat input Q1. The convective heat transfer Q2 depends on the temperature difference between the external gas temperature Tair and the panel temperature Tp. Therefore, the greater the temperature difference (the difference in the vertical axis coordinates between the external gas temperature Tair and the panel temperature Tp at the same moment), the greater the absolute value of the convective heat transfer Q2. When the external gas temperature Tair is higher than the panel temperature Tp (refer to the right descending shaded area), the convective heat transfer Q2 is positive. When the external gas temperature Tair is lower than the panel temperature Tp (refer to the right ascending shaded area), the convective heat transfer Q2 is negative.

[0084] The radiative heat input Q1 and the total daily solar radiation Wsun reach their maximum values ​​at the time of upper zenith, and then shift symmetrically with the time of upper zenith as the baseline. This is because the example illustrates a day with clear skies throughout the day; the radiative heat input Q1 and the total daily solar radiation Wsun may vary in complex ways depending on cloud cover.

[0085] The external gas temperature Tair, like the total solar radiation Wsun, shifts in the same direction, reaching its maximum near the time of upper zenith. In contrast, the panel temperature Tp reaches its maximum later than the time of upper zenith. After sunrise, the panel temperature Tp rises towards its maximum, but continues to rise at a temperature lower than the external gas temperature Tair. The time t1 during Tp's ascent towards its maximum is higher than the external gas temperature Tair. Time t1 is around the time of upper zenith. After reaching its maximum, the panel temperature Tp decreases while maintaining a higher temperature than the external gas temperature Tair.

[0086] Before time t1, the convective heat transfer Q2 is positive, so the heat carrier M flows, and the temperature of the heat carrier M inside the heat carrier tank 3 rises. At time t1, the convective heat transfer Q2 changes from positive to negative. Immediately after time t1, the temperature difference is small, and the absolute value of the convective heat transfer Q2 is small. On the other hand, since time t1 is near the upper zenith, sufficient solar radiation is received. The radiative heat input Q1 is significantly higher than the absolute value of the convective heat transfer Q2, and the acquired heat Q becomes positive. Therefore, even though the convective heat transfer Q2 turns negative, the flow of heat carrier M continues, and the acquired heat Q is continuously recovered by heat carrier M.

[0087] Then, the temperature difference continues to widen until near the moment when the panel temperature Tp reaches its maximum value. As sunset approaches, without narrowing the temporarily widened temperature difference, the total daily solar radiation Wsun, and consequently the radiative heat input Q1, decreases significantly. At time t2, when the radiative heat input Q1 reaches the absolute value of the convective heat input Q2, the acquired heat Q turns from positive to negative. At time t2, the flow of heat carrier M ceases, preventing the heat carrier M from cooling down in the time band after time t2.

[0088] According to the solar thermal collection system 1 of this embodiment, the solar thermal collection panel 2 actively has a non-insulated portion 2c that is expected to generate convective heat transfer between the solar thermal collection panel 2 and the surrounding air. Therefore, in the solar thermal collection panel 2, not only radiative heat from sunlight but also convective heat from the surrounding air can be transferred to the heat carrier M, increasing the heat gain Q in the solar thermal collection panel 2. Furthermore, the switching of the flow of heat carrier M or the adjustment of the flow rate of heat carrier M is based on the radiative heat input Q1 and the convective heat transfer Q2. Therefore, optimization of heat recovery by the heat carrier M can be achieved.

[0089] Specifically, when the convective heat transfer Q2 is negative and the radiative heat input Q1 is less than the absolute value of the convective heat transfer Q2, the control device 9 controls the heat carrier flow control mechanism 5 to stop the supply of heat carrier M to the solar collector panel 2. Thus, when the convective heat transfer Q2 from the solar collector panel 2 to the surrounding air is higher than the radiative heat input Q1 received by the solar collector panel 2, the supply of heat carrier M stops. That is, when the heat received Q is negative, the supply of heat carrier M stops, thus preventing the heat carrier M from cooling down on the solar collector panel 2.

[0090] Conversely, even if the convective heat transfer Q2 is negative, the control device 9 still controls the heat carrier flow control mechanism 5 to supply the heat carrier M to the solar collector panel 2 when the radiant heat input Q1 is greater than the absolute value of the convective heat transfer Q2. Thus, if the obtained heat Q is positive, the obtained heat can be recovered using the heat carrier M.

[0091] Based on measurements of the potentially variable daily solar radiation Wsun, the radiative heat input Q1 is measured sequentially as the heat per unit time. Similarly, based on measurements of the potentially variable temperature difference between the external gas temperature Tair and the panel temperature Tp, the convective heat transfer Q2 is measured sequentially as the heat per unit time. Based on these radiative heat input Q1 and convective heat transfer Q2, the obtained heat Q is also evaluated as the heat per unit time. Therefore, the control's ability to adapt to environmental changes can be improved, and heat recovery from the heat carrier M can be optimized. For example, pump 5a can be stopped immediately in response to a sudden increase in cloud cover or a rise in external gas temperature, preventing heat loss from the heat carrier M.

[0092] Return to Figure 1 The heat recovered by the heat carrier M can also be utilized in the agricultural greenhouse 90. The agricultural greenhouse 90 is a preferred application example of the solar thermal collection system 1 of this embodiment.

[0093] An agricultural greenhouse 90 is constructed on a generally horizontal, rectangular site. The agricultural greenhouse 90 has a body 91 formed from steel or extruded aluminum. The entire body 91 is covered by an outer skin (not shown) formed from a translucent material (e.g., polyvinyl chloride). Thus, the interior of the agricultural greenhouse 90 is protected from wind and rain. The body 91 includes columns 91a erected at the four corners and the center of the site, trusses and beams 91b spanning the upper ends of the columns 91a, and a roof 91c mounted on the trusses and beams 91b. The roof shape is not particularly limited; for example, it can be A-frame or arched. Inside the agricultural greenhouse 90, plants 99 are cultivated in a culture medium 98. The plants 99 are preferably crops. The culture medium 98 is the growth medium for the plants 99, appropriately selected from soil, rock wool, and nutrient solutions, taking into account compatibility with the cultivated plants 99.

[0094] The solar thermal collection system 1 is used to assist in the growth of plants 99. The temperature of the culture medium 98 and plants 99 can also be adjusted using the heat recovered by the heat carrier M. In this case, the solar thermal collection panel 2 is preferably positioned directly below the roof 91c of the agricultural greenhouse 90 (inside the agricultural greenhouse 90) with the light-receiving part 2b facing south. Since the roof is transparent, the air inside the agricultural greenhouse 90 is heated by sunlight, so the solar thermal collection panel 2 can collect convective heat from the heated air inside the agricultural greenhouse 90, in addition to the radiant heat input from the sunlight passing through the transparent roof. By placing the heat carrier tank 3 inside the agricultural greenhouse 90, an insulation effect from the air inside the agricultural greenhouse 90 can be expected. Alternatively, it can be placed outside the agricultural greenhouse 90, but in this case, the tank structure requires higher insulation than when placed inside the agricultural greenhouse 90. The same effect can be achieved by placing the solar thermal collection panel 2 on the roof or wall of a building or other structure, allowing for the collection of radiant and convective heat from the building structure heated by sunlight.

[0095] (Second Implementation) Next, refer to Figure 6 The solar thermal collection system 1 of the second embodiment will be described with a focus on the differences from the first embodiment.

[0096] In this embodiment, the heat transfer tank 3 includes a first heat transfer tank 3a and a second heat transfer tank 3b, which is separate from the first heat transfer tank 3a. An inflow line 4a connects the first heat transfer tank 3a to the inlet of the solar collector panel 2, transporting the heat transfer medium M from the first heat transfer tank 3a to the hollow section 2a. An outflow line 4b connects the outlet of the solar collector panel 2 to the second heat transfer tank 3b, transporting the heat transfer medium M from the hollow section 2a to the second heat transfer tank 3b.

[0097] In this case, since the heat carrier M after heat recovery is stored in the second heat carrier tank 3b, the heat carrier M in the first heat carrier tank 3a is maintained at a low temperature. Therefore, the panel temperature Tp can be maintained at a low temperature, and the convective heat transfer Q2 can be maintained at a relatively high positive value. Consequently, the heat gain Q in the solar collector panel 2 can be increased.

[0098] (Third implementation) Next, refer to Figure 7 The solar thermal collection system 1 of the third embodiment will be described with a focus on the differences from the second embodiment.

[0099] In this embodiment, the heat transfer tank 3 also includes a first heat transfer tank 3a and a second heat transfer tank 3b, which is separate from the first heat transfer tank 3a. The heat transfer circulation line 4, like in the second embodiment, includes an inflow line 4a and an outflow line 4b. The heat transfer circulation line 4 also includes a return line 4c, which branches off from the outflow line 4b and returns the heat transfer medium M to the first heat transfer tank 3a.

[0100] The heat transfer fluid flow control mechanism 5 includes a three-way valve 5c located at the point where the return line 4c branches off from the outflow line 4b. The three-way valve 5c is an example of a direction switching mechanism that switches the direction of heat transfer fluid M transport. The three-way valve 5c switches between states where heat transfer fluid M flowing from the solar collector panel 2 is transported via the outflow line 4b to the second heat transfer fluid tank 3b, and states where heat transfer fluid M flowing from the solar collector panel 2 is returned to the first heat transfer fluid tank 3a via the return line 4c. The three-way valve 5c is a solenoid valve and is connected to the control device 9. The switching of the state of the three-way valve 5c is controlled by the control device 9. Here, the control device 9 controls the switching of the three-way valve 5c so that if the heat obtained Q (=Q1+Q2) calculated by the control device 9 is greater than the reference value set by the user, the heat carrier M is sent back to the first heat carrier tank 3a to make it a high-temperature heat carrier; if it is less than the reference value, the heat carrier M is sent to the second heat carrier tank 3b to maximize the heat collection.

[0101] According to this embodiment, depending on the situation, it is possible to switch between a state where the temperature of the heat carrier M supplied to the solar collector panel 2 is maintained at a low level and a state where the heat carrier M is preheated.

[0102] (Fourth implementation) Next, refer to Figure 8 The solar thermal collection system 1 of the fourth embodiment will be described with a focus on the differences from the first embodiment.

[0103] In this embodiment, the heat transfer tank 3 is a single unit, similar to that in the first embodiment. However, the heat transfer tank 3 is a layered type. That is, the heat transfer tank 3 has an outlet at the bottom and an inlet at the top. At the bottom, a lower temperature heat transfer medium M is stored, and at the top, a higher temperature heat transfer medium after heat recovery is stored. No active convection occurs within the heat transfer tank 3, therefore the same heat transfer medium M at different temperatures is stored in two layers. An inflow line 4a connects the outlet of the heat transfer tank 3 to the inlet of the solar collector panel. An outflow line 4b connects the outlet of the solar collector panel 2 to the inlet of the heat transfer tank 3.

[0104] According to this embodiment, the convective heat transfer Q2 can be maintained at a relatively high positive value without increasing the number of tanks, just like in the second embodiment, thereby increasing the heat transfer Q obtained by the solar collector panel 2.

[0105] (Modified example) The implementation method has been described so far, but the above structure can be appropriately modified within the scope of the spirit of the present invention.

[0106] The panel body 11 of the solar collector panel 2 is not limited to extruded aluminum alloy; it can also be manufactured using other materials and methods. For example, the panel body 11 can be formed by stacking two aluminum sheets. In this case, a groove is formed in at least one of the sheets. By closing the groove with the other sheet, a hollow portion can be formed. Steel or copper can also be used as materials other than aluminum.

[0107] Multiple solar collector panels 2 can also be installed. In this case, the inflow line 4a connects the heat transfer tank 3 in parallel with multiple inlets, and the outflow line 4b connects the heat transfer tank 3 in parallel with multiple outlets.

[0108] The control device 80 can also control the heat transfer fluid flow control mechanism 5 to adjust the flow rate of the heat transfer fluid M based on the heat obtained Q.

[0109] The solar thermal collection system 1 can be applied to purposes other than agricultural greenhouses 90. For example, it can also be installed on buildings or houses to effectively utilize the generation of warm water used in the building.

[0110] This disclosure may include the following schemes.

[0111] (Option 1) A solar thermal collection system includes: a solar thermal collection panel having a hollow portion for allowing a heat carrier to circulate, a light-receiving portion for receiving sunlight, and a non-insulated portion for convective heat transfer between the panel and the surrounding air, transferring radiant heat from the sunlight and convective heat from the surrounding air to the heat carrier; a heat carrier tank for storing the heat carrier; a heat carrier circulation line for transporting the heat carrier from the heat carrier tank to the solar thermal collection panel and from the solar thermal collection panel to the heat carrier tank; a heat carrier circulation control mechanism for switching whether the heat carrier can circulate along the heat carrier circulation line and adjusting the flow rate of the heat carrier; and a control device; the control device measures the amount of radiant heat input to the solar thermal collection panel, measures the amount of convective heat transfer between the solar thermal collection panel and the surrounding air, and controls the heat carrier circulation control mechanism based on the amount of radiant heat input and the amount of convective heat transfer.

[0112] (Option 2) As described in Scheme 1, when the aforementioned convective heat is transferred from the aforementioned solar collector panel to the aforementioned surrounding air, the aforementioned convective heat transfer becomes negative; when the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is less than the absolute value of the aforementioned convective heat transfer, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to stop the supply of the aforementioned heat carrier to the aforementioned solar collector panel.

[0113] (Option 3) As described in Scheme 1 or 2, in the solar thermal collection system, when the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is greater than the absolute value of the aforementioned convective heat transfer, the aforementioned heat carrier flow control mechanism controls the aforementioned heat carrier to supply the aforementioned heat carrier to the aforementioned solar thermal collection panel.

[0114] (Option 4) In any one of the embodiments 1 to 3, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to supply the aforementioned heat carrier to the aforementioned solar collector panel when the aforementioned convective heat transfer is positive.

[0115] (Option 5) The solar thermal collection system according to any one of Schemes 1 to 4 further includes a solar radiation meter for measuring the total solar radiation throughout the day; the aforementioned control device measures the total solar radiation throughout the day as heat per unit time based on the total solar radiation measured by the aforementioned solar radiation meter and the surface area of ​​the aforementioned light-receiving part.

[0116] (Option 6) The solar thermal collection system according to any one of Schemes 1 to 5 further comprises: an external gas temperature sensor for measuring the temperature of the surrounding air of the aforementioned solar thermal collection panel; and a panel temperature sensor for measuring the temperature of the aforementioned solar thermal collection panel side; the aforementioned control device measures the aforementioned convective heat transfer as heat per unit time based on the temperature difference measured by the aforementioned external gas temperature sensor and the aforementioned panel temperature sensor, the outer surface area of ​​the aforementioned non-insulated part, and the convective heat transfer coefficient of the aforementioned non-insulated part.

[0117] (Option 7) As described in Scheme 6, the solar thermal collector system comprises at least one surface temperature sensor that measures the surface temperature of the aforementioned non-insulated part, an inlet temperature sensor that measures the temperature near the inlet of the aforementioned hollow part, and an outlet temperature sensor that measures the temperature near the outlet of the aforementioned hollow part.

[0118] (Option 8) As described in any one of Schemes 1 to 7, the aforementioned heat carrier tank includes a first heat carrier tank and a second heat carrier tank that is separate from the first heat carrier tank; the aforementioned heat carrier circulation line includes an inflow line that transports the aforementioned heat carrier from the aforementioned first heat carrier tank to the aforementioned hollow section, and an outflow line that transports the aforementioned heat carrier from the aforementioned hollow section to the aforementioned second heat carrier tank.

[0119] (Option 9) As described in Scheme 8, the solar thermal collection system further includes a return line that branches off from the outflow line to send the heat carrier back to the first heat carrier tank; the heat carrier flow control mechanism includes a direction switching mechanism that switches between the state of transporting the heat carrier to the second heat carrier tank via the outflow line and the state of sending the heat carrier back to the first heat carrier tank via the return line.

[0120] (Option 10) As in any one of Schemes 1 to 7, the aforementioned heat carrier tank is a layered type having an outlet at the bottom and an inlet at the top; the aforementioned heat carrier circulation line includes an inflow line connecting the aforementioned outlet of the aforementioned heat carrier tank to the aforementioned hollow part, and an outflow line connecting the aforementioned hollow part to the aforementioned inlet of the aforementioned heat carrier tank.

[0121] This application is accompanied by a priority claim based on Japanese Patent Application No. 2023-188416, filed on November 2, 2023. Japanese Patent Application No. 2023-188416 is incorporated herein by reference.

[0122] Explanation of reference numerals in the attached figures 1. Solar thermal collection system 2. Solar thermal collector panel 2a Hollow section 2b Light-receiving section 2c Non-insulated part 3 Heat transfer tank 3a First heat transfer tank 3b Second heat transfer tank 4. Heat transfer fluid circulation circuit 4a Inflow route 4b Outflow Line 4c Return Line 5. Heat transfer fluid flow control mechanism 5a pump 5b valve 5c three-way valve 6-day shooting plan 7. External gas temperature sensor 8 Panel Temperature Sensor 8a Surface Temperature Sensor 8b Inlet temperature sensor 8c outlet temperature sensor 9. Control device 11 Panel Body 11a First Main Wall 11b Second Main Wall 11c sidewall 11d next door 12 First Collection Pipe 13 Second Collection Pipe 12a, 13a cover plates 12b, 13b Perimeter 12c, 13c interior space 14 Entrances 15 Exports 90 agricultural greenhouses 91. Body Column 91a 91b Beam 91c roof 98 Culture Medium 99 plants Ap external surface area Asun light-receiving area M heat carrier Q1 Radiant heat input Q2 Convection heat transfer Tair external gas temperature Tp panel temperature Tin inlet temperature Tout outlet temperature Tsf surface temperature Wsun's total daily solar radiation α emissivity μ is the convective heat transfer coefficient.

Claims

1. A solar thermal collection system, characterized in that, have: A solar collector panel has a hollow part for allowing heat carrier to circulate, a light-receiving part for receiving sunlight, and a non-insulated part for convective heat transfer between the panel and the surrounding air, which transfers radiative heat from the aforementioned sunlight and convective heat from the aforementioned surrounding air to the aforementioned heat carrier. A heat transfer container for storing the aforementioned heat transfer medium; The heat carrier circulation circuit transports the aforementioned heat carrier from the aforementioned heat carrier tank to the aforementioned solar collector panel, and the aforementioned heat carrier from the aforementioned solar collector panel to the aforementioned heat carrier tank. The heat transfer fluid flow control mechanism performs at least one of the following: switching the flowability of the heat transfer fluid along the aforementioned heat transfer fluid circulation path and adjusting the flow rate of the aforementioned heat transfer fluid; and Control device; The aforementioned control device The amount of radiant heat input to the aforementioned solar collector panel was measured. Measure the convective heat transfer between the aforementioned solar collector panel and the surrounding air. Based on the aforementioned radiative heat input and convective heat transfer, the aforementioned heat carrier flow control mechanism is used to control the flow of heat.

2. The solar thermal collection system as described in claim 1, characterized in that, When the aforementioned convective heat is transferred from the aforementioned solar collector panel to the aforementioned surrounding air, the aforementioned convective heat transfer becomes negative; When the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is less than the absolute value of the aforementioned convective heat transfer, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to stop the supply of the aforementioned heat carrier to the aforementioned solar collector panel.

3. The solar thermal collection system as described in claim 2, characterized in that, When the aforementioned convective heat transfer is negative and the aforementioned radiative heat input is greater than or equal to the absolute value of the aforementioned convective heat transfer, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to supply the aforementioned heat carrier to the aforementioned solar collector panel.

4. The solar thermal collection system as described in claim 2, characterized in that, When the aforementioned convective heat transfer is positive, the aforementioned control device controls the aforementioned heat carrier flow control mechanism to supply the aforementioned heat carrier to the aforementioned solar collector panel.

5. The solar thermal collection system according to any one of claims 1 to 4, characterized in that, It also has a sunmeter for measuring the total solar radiation throughout the day; The aforementioned control device measures the aforementioned radiant heat input as heat per unit time based on the aforementioned total solar radiation measured by the aforementioned solar radiation meter and the aforementioned surface area of ​​the aforementioned light-receiving part.

6. The solar thermal collection system according to any one of claims 1 to 4, characterized in that, It also has: An external gas temperature sensor measures the temperature of the air surrounding the aforementioned solar collector panel; and A panel temperature sensor measures the temperature on the side of the aforementioned solar collector panel. The aforementioned control device measures the heat transfer per unit time based on the temperature difference measured by the aforementioned external gas temperature sensor and the aforementioned panel temperature sensor, the outer surface area of ​​the aforementioned non-insulated part, and the convective heat transfer coefficient of the aforementioned non-insulated part.

7. The solar thermal collection system as described in claim 6, characterized in that, The aforementioned panel temperature sensor comprises at least one surface temperature sensor that measures the surface temperature of the aforementioned non-insulated part, an inlet temperature sensor that measures the temperature near the inlet of the aforementioned hollow part, and an outlet temperature sensor that measures the temperature near the outlet of the aforementioned hollow part.

8. The solar thermal collection system according to any one of claims 1 to 4, characterized in that, The aforementioned heat transfer tank includes a first heat transfer tank and a second heat transfer tank that is separate from the first heat transfer tank; The aforementioned heat transfer fluid circulation circuit includes an inflow line that transports the aforementioned heat transfer fluid from the aforementioned first heat transfer fluid tank to the aforementioned hollow section, and an outflow line that transports the aforementioned heat transfer fluid from the aforementioned hollow section to the aforementioned second heat transfer fluid tank.

9. The solar thermal collection system as described in claim 8, characterized in that, The aforementioned heat transfer fluid circulation circuit also includes a return line that branches off from the aforementioned outflow line and sends the aforementioned heat transfer fluid back to the aforementioned first heat transfer fluid tank; The aforementioned heat transfer fluid flow control mechanism includes a direction switching mechanism, which switches between the state of transporting the aforementioned heat transfer fluid to the aforementioned second heat transfer fluid tank via the aforementioned outflow line and the state of sending the aforementioned heat transfer fluid back to the aforementioned first heat transfer fluid tank via the aforementioned return line.

10. The solar thermal collection system according to any one of claims 1 to 4, characterized in that, The aforementioned heat transfer tank is a layered type with an outlet located at the bottom and an inlet located at the top; The aforementioned heat transfer fluid circulation line includes an inflow line connecting the aforementioned outlet of the aforementioned heat transfer fluid tank to the aforementioned hollow portion, and an outflow line connecting the aforementioned hollow portion to the aforementioned inlet of the aforementioned heat transfer fluid tank.

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