Sunlight heat collecting system

Abstract

To improve heat quantity acquired from a sunlight heat collection panel.SOLUTION: A sunlight heat collecting system 1 includes: a sunlight heat collection panel 2 that has a non-heat insulation part 2c causing convection heat transfer with surrounding air and transfers radiation heat from the sunlight and convection heat from the surrounding air to a heating medium M; a heating medium circulation line 4 for sending the heating medium M from a heating medium tank 3 that stores the heating medium M to the sunlight heat collection panel 2 and sending the heating medium M from the sunlight heat collection panel 2 to the heating medium tank 3; a heating medium flowing control mechanism 5 that performs at least either of switching between permission and prohibition of flowing of the heating medium M along the heating medium circulation line 4 or regulation of a flow rate of the heating medium M; and a control device 9. The control device 9 measures radiation heat input quantity Q1 to the sunlight heat collection panel 2, measures convection heat transfer quantity Q2 between the sunlight heat collection panel 2 and the surrounding air, and controls the heating medium flowing control mechanism 5 on the basis of the radiation heat input quantity Q1 and the convection heat transfer quantity Q2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a solar heat collecting system. [Background technology]

[0002] Patent Document 1 discloses a solar heat collection control device that supplies a heat medium from a heat storage tank to a heat collection unit, warms the heat medium with solar heat in the heat collection unit, and returns the heat medium from the heat collection unit to the heat storage tank. The pump that circulates the heat medium is switched on and off according to temperature conditions inside the device, such as the heat collection unit and the heat storage tank. For example, the pump operates when the temperature of the heat collection unit is higher than the temperature of the heat storage tank by a predetermined temperature or more, and when the temperature of the heat medium return piping is higher than the temperature of the heat storage tank by a predetermined temperature or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 58-102062 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional solar heat collection systems such as those described above, emphasis is placed on transferring radiant heat from sunlight to a heat medium in the panel-shaped heat collection section, and it is believed that there is room for improvement in the amount of heat acquired in the heat collection section.

[0005] An object of the present invention is to improve the amount of heat acquired by a solar heat collecting panel. [Means for solving the problem]

[0006] One aspect of the present invention provides a solar thermal collection system comprising: a solar thermal collection panel having a hollow section for circulating a heat medium, a light receiving section for receiving solar light, and a non-insulated section for performing convective heat transfer between the solar thermal collection panel and the surrounding air, and transferring radiant heat from the solar light and convective heat from the surrounding air to the heat medium; a heat medium tank for storing the heat medium; a heat medium circulation line for sending the heat medium from the heat medium tank to the solar thermal collection panel and from the solar thermal collection panel to the heat medium tank; a heat medium circulation control mechanism for at least one of switching whether or not the heat medium can flow along the heat medium circulation line and adjusting a flow rate of the heat medium; 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 medium circulation control mechanism based on the amount of radiant heat input and the amount of convective heat transfer.

[0007] Generally, a solar heat collecting panel has been provided with a heat insulating structure to prevent convective heat transfer between the panel and the surrounding air. In contrast, according to the above-mentioned configuration, the solar heat collecting panel proactively has a non-insulated portion that is expected to cause convective heat transfer between the panel and the surrounding air. Therefore, in the solar heat collecting panel, not only the radiant heat from sunlight but also the convective heat from the surrounding air can be transferred to the heat medium, and the amount of heat acquired by the solar heat collecting panel increases. Furthermore, switching between allowing and not allowing the heat medium to flow or adjusting the amount of heat medium to flow is performed based on the amount of radiant heat input and the amount of convective heat transfer. Therefore, heat recovery by the heat medium is optimized.

[0008] When the convective heat is transferred from the solar thermal collection panel to the surrounding air, the amount of convective heat transfer becomes negative, and the control device may control the heat medium flow control mechanism to stop the supply of the heat medium to the solar thermal collection panel when the amount of convective heat transfer is negative and the amount of radiant heat input is less than the absolute value of the amount of convective heat transfer.

[0009] Here, if a non-insulated section is provided in the solar heat collecting panel to obtain convection heat from the surrounding air, it is possible that the convection heat may escape from the solar heat collecting panel into the surrounding air depending on the situation. In contrast, with the above configuration, when the amount of convection heat transferred from the solar heat collecting panel to the surrounding air exceeds the amount of radiant heat input received by the solar heat collecting panel, the supply of the heat medium is stopped. Therefore, it is possible to prevent the temperature of the heat medium from dropping, and to optimize the heat recovery by the heat medium.

[0010] The control device may control the heat medium flow control mechanism so that the heat medium is supplied to the solar thermal collecting panel when the convective heat transfer amount is negative and the radiant heat input amount is greater than or equal to the absolute value of the convective heat transfer amount.

[0011] According to the above configuration, when the amount of convective heat transferred from the solar heat collecting panel to the surrounding air is less than the amount of radiant heat input received by the solar heat collecting panel, the heat medium circulates. Therefore, the heat medium can be heated by the amount of heat acquired by the solar heat collecting panel.

[0012] The control device may control the heat medium flow control mechanism such that the heat medium is supplied to the solar thermal collecting panel when the amount of convective heat transfer is positive.

[0013] According to the above configuration, when convection heat is entering the solar heat collecting panel from the surrounding air, the heat medium circulates. Therefore, the heat medium can be heated by the amount of heat acquired by the solar heat collecting panel.

[0014] The solar heat collecting system may further include a pyranometer that measures global solar radiation, and the control device may measure the radiant heat input as heat quantity per unit time based on the global solar radiation measured by the pyranometer and a surface area of ​​the light receiving unit.

[0015] According to the above configuration, the amount of radiant heat input can be successively measured as the amount of heat per unit time based on the measurement results of the amount of global solar radiation, which may change from moment to moment. Based on such amount of radiant heat input, switching on / off of the flow of the heat medium or adjusting the flow rate of the heat medium is performed, so that the ability to follow the control for environmental changes such as fluctuations in cloud cover is improved, and it is easy to optimize the heat recovery by the heat medium.

[0016] The solar thermal collection system may further include an outside air temperature sensor that measures the temperature of the air surrounding the solar thermal collection panel, and a panel temperature sensor that measures the temperature on the solar thermal collection panel side, and the control device may measure the convective heat transfer amount as a heat quantity per unit time based on the difference in the temperatures measured by the outside air temperature sensor and the panel temperature sensor, respectively, the outer surface area of ​​the non-insulated portion, and the convective heat transfer coefficient of the non-insulated portion.

[0017] According to the above configuration, the amount of convective heat transfer can be successively measured as the amount of heat per unit time based on the measurement result of the temperature difference, which may change from moment to moment. Based on such a convective heat transfer amount, switching on / off of the flow of the heat medium or adjusting the flow rate of the heat medium is performed, so that the ability to follow environmental changes such as temperature fluctuations is improved, and it is easy to optimize the heat recovery by the heat medium.

[0018] The panel temperature sensor may be composed of at least one of a surface temperature sensor that measures the surface temperature of the non-insulated portion, an inlet temperature sensor that measures the temperature near the entrance of the hollow portion, and an outlet temperature sensor that measures the temperature near the exit of the hollow portion.

[0019] According to the above configuration, the panel temperature can be measured with high accuracy.

[0020] The heat medium tank may include a first heat medium tank and a second heat medium tank separate from the first heat medium tank, and the heat medium circulation line may include an inlet line for sending the heat medium from the first heat medium tank to the hollow portion, and an outlet line for sending the heat medium from the hollow portion to the second heat medium tank.

[0021] According to the above configuration, the temperature of the heat medium supplied to the solar heat collecting panel during the heat collection time can be kept lower than the temperature of the solar heat collecting panel, and a large temperature difference can be maintained. Therefore, the amount of heat transferred from the solar heat collecting panel to the heat medium can be kept high, and as a result, the amount of heat stored in the second tank acquired by the solar heat collecting panel can be increased.

[0022] The heat medium circulation line may further include a return line branching from the outflow line and returning the heat medium to the first heat medium tank, and the heat medium flow control mechanism may include a direction switching mechanism that switches between a state in which the heat medium is sent to the second heat medium tank via the outflow line and a state in which the heat medium is returned to the first heat medium tank via the return line.

[0023] In the above configuration, when the heat medium returns from the first heat medium tank to the first heat medium tank via the solar thermal collection panel, the heat medium temperature in the first heat medium tank can be increased, and a high-temperature heat medium can be obtained. Also, when the heat medium is sent from the first heat medium tank to the second heat medium tank via the solar thermal collection panel, the heat medium temperature cannot be made higher than when it is returned to the first heat medium tank, but the amount of heat collected can be maximized.

[0024] The heat transfer medium tank may be a stratified type having an outlet at the bottom and an inlet at the top, and the heat transfer medium circulation line may include an inlet line connecting the outlet of the heat transfer medium tank to the hollow portion, and an outlet line connecting the hollow portion to the inlet of the heat transfer medium tank.

[0025] According to the above configuration, the amount of heat collected can be kept high without increasing the number of heat medium tanks. Effect of the Invention

[0026] According to the present invention, the amount of heat acquired by a solar heat collecting panel can be improved. [Brief description of the drawings]

[0027] [Figure 1] 1 is a schematic diagram showing the overall configuration of a solar heat collecting system according to a first embodiment. [Figure 2A] FIG. [Figure 2B] FIG. [Figure 2C] Cross-sectional view of a solar thermal collector panel. [Diagram 3] 1 is a schematic diagram showing a main part of a solar heat collecting system according to a first embodiment. [Figure 4] 4 is a flowchart showing a process executed by a control device. [Diagram 5] 5 is a graph showing changes over time in the amount of radiant heat input, the outside air temperature, and the panel temperature. [Figure 6] FIG. 11 is a schematic diagram of a solar heat collecting system according to a second embodiment. [Figure 7] FIG. 11 is a schematic diagram of a solar heat collecting system according to a third embodiment. [Figure 8] FIG. 13 is a schematic diagram of a solar heat collecting system according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment will be described with reference to the drawings. Note that the same or corresponding elements are designated by the same reference numerals throughout the drawings, and detailed description thereof will be omitted.

[0029] (First embodiment) With reference to FIG. 1, a solar heat collecting system 1 according to the first embodiment includes a solar heat collecting panel 2, a heat medium tank 3, a heat medium circulation line 4, and a heat medium flow control mechanism 5.

[0030] The solar thermal collecting panel 2 is in the form of a flat plate, and forms a flow path through which the heat medium M in liquid phase flows. The heat medium tank 3 stores the heat medium M. The heat medium M is, for example, water. However, a liquid other than water may be used as the heat medium M, such as an antifreeze solution containing ethylene glycol as a main component.

[0031] In this embodiment, there is a single heat medium tank 3. The heat medium circulation line 4 includes an inflow line 4a that sends the heat medium M from the heat medium tank 3 to the solar heat collecting panel 2, and an outflow line 4b that sends the heat medium M from the solar heat collecting panel 2 to the heat medium tank 3.

[0032] The heat medium tank 3 has a thermal insulation structure, and the temperature of the heat medium M in the heat medium tank 3 can be controlled to a required temperature regardless of the ambient temperature. The inlet line 4a and the outlet line 4b are formed of piping members such as metal or resin pipes. The piping members may also have a thermal insulation structure.

[0033] The heat medium flow control mechanism 5 at least performs one of switching whether or not the heat medium M flows along the heat medium circulation line 4 and adjusting the flow rate of the heat medium M along the heat medium circulation line 4. In this embodiment, the heat medium flow control mechanism 5 is configured to be able to perform both switching and adjustment.

[0034] The heat medium flow control mechanism 5 may include a pump 5a that pumps the heat medium M along the heat medium circulation line 4, and a valve 5b that is disposed on the heat medium circulation line 4. In the illustrated example, the pump 5a and the valve 5b are disposed on the inlet line 4a, but the pump 5a may be provided in the heat medium tank 3, and the valve 5b may be disposed on the outlet line 4b.

[0035] In this embodiment, as an example, the pump 5a is a fixed displacement type, and the valve 5b is a flow rate adjustment valve. The flow rate of the heat medium M is adjusted by adjusting the opening of the valve 5b. However, this is only an example, and if the valve 5b is an on-off valve, the flow rate of the heat medium M can be adjusted by switching between the open state and the closed state of the valve 5b. If the pump 5a is a variable displacement type, the discharge amount of the heat medium M, and therefore the flow rate, can be adjusted by adjusting the capacity of the pump 5a.

[0036] The heat medium M is pressure-fed by a pump 5a from the heat medium tank 3 through the inflow line 4a to the solar thermal collecting panel 2. In the process of circulating inside the solar thermal collecting panel 2, the heat medium M is warmed by the heat collected in the solar thermal collecting panel 2. When the heat medium M flows out of the solar thermal collecting panel 2, it is sent to the heat medium tank 3 through the outflow line 4b. As a result, hot water is stored in the heat medium tank 3.

[0037] 2A to 2C, the structure of the solar thermal collecting panel 2 will be described. The solar thermal collecting panel 2 has a panel body 11, a first header 12, a second header 13, an inlet 14, and an outlet 15.

[0038] The panel body 11 is made of an extruded aluminum alloy material. As the aluminum alloy, 1000 series aluminum alloy having excellent thermal conductivity or 6000 series aluminum alloy having excellent thermal conductivity and strength are suitable.

[0039] 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-backed rectangular tube, and both ends of the rectangular tube in the longitudinal direction are open. This longitudinal direction is the extrusion direction. The first main wall 11a is a rectangular flat plate. The long side extends in the longitudinal direction of the panel body 11, the short side extends in the width direction of the panel body 11, and the plate thickness direction corresponds to the height direction of the panel body 11. The pair of side walls 11c are erected from both 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, is arranged parallel to the first main wall 11a, and completely overlaps the first main wall 11a when viewed in the plate thickness direction, connecting the ends of the pair of side walls 11c. The four walls define a wide, low rectangular opening at each longitudinal end.

[0040] The panel body 11 has a plurality of partition walls 11d. The partition walls 11d extend between a pair of side walls 11c in parallel to the side walls 11c and connect the inner surfaces of the first main wall 11a and the second main wall 11b. The partition walls 11d divide the space surrounded by the four walls into a plurality of hollow portions 2a arranged in the width direction.

[0041] In the illustrated example, there are six partition walls 11d and seven hollow portions 2a, but the number of hollow portions 2a can be changed as appropriate. Each hollow portion 2a has a rectangular cross section. By using extrusion molding, a structure having multiple closed cross sections or multiple hollow portions 2a can be manufactured continuously and integrally. In the illustrated example, 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 a hollow portion inside, they may not be flat and may have irregularities, and multiple protrusions (fins) may be provided on at least one surface of the first main wall 11a, the second main wall 11b, and the pair of side walls 11c. By providing irregularities or fins, the light receiving area and the contact area with the air are increased, and the amount of radiant heat input and the amount of convective heat transfer can be increased.

[0042] Each hollow portion 2a is open at both ends in the longitudinal direction. The first header 12 closes the opening at one end of the hollow portion 2a. The second header 13 closes the opening at the other end of the hollow portion 2a. Both the first header 12 and the second header 13 close the openings of multiple hollow portions 2a collectively.

[0043] The first header 12 has a cover plate 12a, a peripheral wall 12b erected from the peripheral edge 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 the cover plate 12a. The cross section of the internal space 12c (cross section of the inner peripheral surface of the peripheral wall 12b) has the same shape (rectangular in this embodiment) as the cross section of the outer peripheral surface of the panel body 11. The first header 12 abuts against one end of the panel body 11 and is joined to the panel body 11 in a liquid-tight manner.

[0044] The second header 13 has a cover plate 13a, a peripheral wall 13b, and an internal space 13c, similar to the first header 12, and is attached to the other end of the panel body 11 in the longitudinal direction, similar to the first header 12.

[0045] The inlet 14 and the outlet 15 are provided in the first header 12 or the second header 13. The inlet 14 is connected to the inlet line 4a (see Figs. 1 and 3), and the outlet 15 is connected to the outlet line 4b (see Figs. 1 and 3). The inlet 14 is cylindrical or nipple-shaped, and the inlet line 4a, which serves as a piping member, is attached to the inlet 14 in a liquid-tight manner. The same applies to the outlet 15 and the outlet line 4b.

[0046] In this embodiment, a single inlet 14 is provided in the first header 12, and a single outlet 15 is provided in the second header 13. The inlet 14 and the outlet 15 penetrate the corresponding cover plates 12a, 13a. The heat transfer medium M flows into the internal space 12c of the first header 12 through the inlet 14, and is then diverted from the internal space 12c to each of the multiple hollow portions 2a. The heat transfer medium M merges from each of the multiple hollow portions 2a in the internal space 13c of the second header 13, and then flows out of the internal space 13c through the outlet 15.

[0047] In this way, the heat medium M flows in one direction, from one side to the other side in the longitudinal direction, through the solar thermal collecting panel 2. The heat medium M flows through the hollow portion 2a while filling the hollow portion 2a, that is, while contacting the wall and its inner surface of the panel body 11 that defines the hollow portion 2a.

[0048] 3, the solar thermal collecting panel 2 has a light receiving section 2b that receives solar light. The solar thermal collecting panel 2 transfers radiant heat from the solar light to a heat medium M. The solar thermal collecting panel 2 also positively has a non-insulated section 2c that is expected to perform convective heat transfer with the surrounding air. When convective heat is transferred from the surrounding air to the solar thermal collecting panel 2, the solar thermal collecting panel 2 transfers the convective heat to the heat medium M. The radiant heat and convective heat are transferred to the heat medium M by solid-state heat transfer in the panel body 11, whereby the heat medium M is heated.

[0049] The amount of heat Q acquired by the solar thermal collecting panel 2 per unit time can be defined as the sum of the amount of radiative heat input Q1 and the amount of convective heat transfer Q2 (Q=Q1+Q2). The heat medium M rises in temperature from the inlet 14 to the outlet 15 by an amount corresponding to the amount of heat acquired Q and the flow rate of the heat medium M.

[0050] The "amount of radiant heat input Q1" can be defined as the amount of radiant heat (W) input by sunlight to the solar heat collecting panel 2 (particularly, its light receiving portion 2b) per unit time. The amount of radiant heat input Q1 is expressed by the following formula (1).

[0051] Q1=αWsunAsun ……(1) Here, α is the emissivity (dimensionless) of the surface of the solar heat collecting panel 2, more specifically, the emissivity of the light receiving part 2b. Wsun is the total solar radiation (W / m 2 ) Asun is the light receiving area (m2) of the solar heat collecting panel 2. 2 ), more specifically, the surface area of ​​the light receiving portion 2b (hereinafter simply referred to as the light receiving area Asun).

[0052] The light receiving portion 2b is all or part of the outer surfaces of the first main wall 11a, the second main wall 11b, the pair of side walls 11c, the first header 12, and the second header 13. The surface of the light receiving portion 2b is painted black. This makes the emissivity α of the light receiving portion 2b close to 1, improving the heat collection ratio of the solar thermal collecting panel 2. The emissivity of an aluminum alloy is 10 -2 From 10 -1 Since this is an order of magnitude value, the effect of painting is remarkable when the panel body 11 is made of an aluminum alloy. The heat collection ratio is a dimensionless value obtained by dividing the thermal energy per unit area acquired from sunlight by the total solar radiation Wsun, and the closer the ratio is to 1, the higher the heat collection efficiency.

[0053] The "amount of convective heat transfer Q2" can be defined as the amount of convective heat (W) exchanged between the ambient air and the solar thermal collecting panel 2 (particularly, the non-insulated portion 2c) per unit time. The amount of convective heat transfer Q2 is expressed by the following formula (2).

[0054] Q2 = μ(Tair-Tp)Ap ……(2) Here, μ is the convection heat transfer coefficient of the solar collector panel 2 (W / K m 2 ), more specifically, the convection heat transfer coefficient of the non-insulated portion 2c. Tair is the temperature (K) of the air surrounding the solar thermal collecting panel 2 (hereinafter referred to as the outside air temperature Tair). Tp is the temperature (K) on the solar thermal collecting panel 2 side (hereinafter referred to as the panel temperature Tp). Ap is the outer surface area (m 2 ), more specifically, the outer surface area of ​​the non-insulated portion 2c (hereinafter simply referred to as the outer surface area Ap).

[0055] The heat medium M contacts the inner surfaces of the walls that define the hollow portion 2a. Substantially the entire inner surfaces of the first main wall 11a, the second main wall 11b, the pair of side walls 11c, the first header 12, and the second header 13 contact the heat medium M, and substantially the entire outer surfaces of these contact the surrounding air. In this embodiment, no heat insulating material is provided on these inner surfaces, nor on their outer surfaces. Therefore, substantially the entire four walls and headers 12 and 13 that constitute the panel body 11 can serve as the non-insulated portion 2c.

[0056] As shown in the above formula (2), the amount of convective heat transfer Q2 is proportional to the temperature difference between the outside air temperature Tair and the panel temperature Tp. When the outside air temperature Tair exceeds the panel temperature Tp, the amount of convective heat transfer Q2 is positive. Convective heat is transferred from the surrounding air to the solar thermal collecting panel 2 (particularly, its non-insulated portion 2c). Conversely, when the panel temperature Tp exceeds the outside air temperature Tair, the amount of convective heat transfer Q2 is negative. Convective heat is transferred from the solar thermal collecting panel 2 (particularly, its non-insulated portion 2c) to the surrounding air.

[0057] The emissivity α, light receiving area Asun, convective heat transfer coefficient μ, and external surface area Ap are determined according to the design specifications of the solar thermal collecting panel 2. In the design and practical stages of the solar thermal collecting panel 2, these parameters can be treated as constants. Meanwhile, the total solar radiation Wsun, the outside air temperature Tair, and the panel temperature Tp change from moment to moment. When calculating the amount of radiant heat input Q1 and the amount of convective heat transfer Q2, it is necessary to actually measure these parameters.

[0058] Returning to Fig. 1, the solar thermal collecting system 1 further includes an actinometer 6, an outside air temperature sensor 7, and a panel temperature sensor 8. The actinometer 6 is installed near the light receiving unit 2b and measures the total solar radiation Wsun. The outside air temperature sensor 7 is installed outside the solar thermal collecting panel 2 and near the solar thermal collecting panel 2 and measures or detects the outside air temperature Tair. The panel temperature sensor 8 is installed on the surface of or inside the solar thermal collecting panel 2 and measures or detects the panel temperature Tp.

[0059] 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 thermal collecting panel 2 (hereinafter referred to as the surface temperature Tsf), particularly the temperature of the outer surface of the non-insulated portion 2c. The inlet temperature sensor 8b measures the temperature in the vicinity of the inlet 14 of the heat medium M of the solar thermal collecting panel 2 (hereinafter referred to as the inlet temperature Tin). The outlet temperature sensor 8c measures the temperature in the vicinity of the outlet 15 of the heat medium M of the solar thermal collecting panel 2 (hereinafter referred to as the outlet temperature Tout). The inlet temperature Tin may be the temperature of the inner surface of the solar thermal collecting panel 2 near the inlet 14, or may be the temperature of the heat medium M flowing near the inlet 14. The same applies to the outlet temperature Tout.

[0060] Any one of the surface temperature Tsf, the inlet temperature Tin, and the outlet temperature Tout may be treated as the panel temperature Tp. The panel temperature Tp may be an average value of two or more temperatures among the surface temperature Tsf, the inlet temperature Tin, and the outlet temperature Tout. The surface temperature Tsf may be measured at multiple measurement points on one solar thermal collecting panel 2. In that case, the average value of the measurement results of the multiple surface temperatures Tsf may be treated as a single measurement result of the surface temperature Tsf.

[0061] The solar heat collecting system 1 further includes a control device 9. The control device 9 is connected to the pyranometer 6, the outside air temperature sensor 7, and the panel temperature sensor 8, and sequentially acquires the measurement results of these measurement elements at a predetermined sampling period. The control device 9 is connected to the heat medium flow control mechanism 5, and controls the heat medium flow control mechanism 5 based on the measurement results. In other words, the control device 9 controls whether the heat medium M flows along the heat medium circulation line 4, or controls the flow rate of the heat medium M along the heat medium circulation line 4, based on the measurement results.

[0062] The control device 9 includes, for example, a central processing unit (CPU) or a micro processing unit (MPU) that cooperates with software to realize a predetermined function. The control device 9 may be configured with hardware circuits such as a dedicated electronic circuit or a reconfigurable electronic circuit designed to realize a predetermined function, or may be configured with various semiconductor integrated circuits. Examples of various semiconductor integrated circuits include a microcomputer, a digital signal processor (DSP), a field programmable gate array (FPGA), and an application specific integrated circuit (ASIC), in addition to a CPU and an MPU. The control device 9 may also include a storage device such as a random access memory (RAM) and a read only memory (ROM). Specifically, the control device 9 may be configured with, for example, an information processing device such as a desktop personal computer, a notebook computer, a workstation, or a tablet terminal, or a printed circuit board having an equivalent function.

[0063] The storage device of the control device 9 stores programs and information for executing the processes described below. Examples of information stored in advance in the storage device include values ​​of the emissivity α, the light receiving area Asun, the convection heat transfer coefficient μ, and the outer surface area Ap.

[0064] 4 shows a flow of processing executed by the control device 9. The control device 9 repeatedly executes processing according to the flow shown in the figure at predetermined control intervals.

[0065] The control device 9 acquires the measurement results of the total solar radiation Wsun output from the pyranometer 6, the outside air temperature Tair output from the outside air temperature sensor 7, and the panel temperature Tp output from the panel temperature sensor 8 (step S1). As described above, the panel temperature Tp may be the surface temperature Tsf itself, the inlet temperature Tin itself, or the outlet temperature Tout itself, or may be calculated based on these multiple temperatures. The control device 9 may set the acquired measurement result as the panel temperature Tp, or may arithmetically use the panel temperature Tp as a measurement result from the multiple types of acquired measurement results.

[0066] Next, the control device 9 calculates the amount of radiant heat input Q1 according to the above formula (1) (step S2). The emissivity α and the light receiving area Asun as factors in the formula (1) can be read out from the storage device.

[0067] In addition, the control device 9 calculates the convection heat transfer amount Q2 according to the above formula (2) based on the temperature difference between the measured outside air temperature Tair and the panel temperature Tp (step S2). The convection heat transfer coefficient μ and the external surface area Ap as factors in formula (2) can be read from the storage device.

[0068] Next, the control device 9 determines whether the measured amount of convection heat transfer Q2 is 0 or positive (step S3a). If the amount of convection heat transfer Q2 is negative (S3a: NO), it determines whether the absolute value of the amount of radiant heat input Q1 is equal to or greater than the absolute value of the amount of convection heat transfer Q2 (step S3b).

[0069] If the convection heat transfer amount Q2 is 0 or positive (S3a: YES), the control device 9 controls the heat medium flow control mechanism 5 to continue the flow of the heat medium M (step S4). If the convection heat transfer amount Q2 is negative (S3a: NO) and the absolute value of the radiant heat input amount Q1 is equal to or greater than the absolute value of the convection heat transfer amount Q2 (S3b: YES), the process also proceeds to step S4. To continue the flow of the heat medium 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 greater.

[0070] When the convection heat transfer amount Q2 is negative (S3a: NO) and the absolute value of the radiation heat input amount Q1 is less than the absolute value of the convection heat transfer amount Q2 (S3b: NO), the control device 9 controls the heat medium flow control mechanism 5 to stop the flow of the heat medium M (step S5). To stop the flow of the heat medium M, the control device 9, for example, stops the pump 5a and fully closes the valve 5b.

[0071] Here, the radiation heat input Q1 is proportional to the global solar radiation Wsun. Since the global solar radiation Wsun cannot be negative, the radiation heat input Q1 is also zero or positive. If the convection heat transfer amount Q2 is zero or positive (S3a: YES), the heat gain Q is zero or positive. Even if the convection heat transfer amount Q2 is negative, if the absolute value of the convection heat transfer amount Q2 is lower than the radiation heat input Q1 (or its absolute value) (S3b: YES), the heat gain Q is positive. Thus, if the heat gain Q is zero or positive, the flow of the heat medium M continues (step S4).

[0072] On the other hand, if the convection heat transfer amount Q2 is negative and the absolute value of the convection heat transfer amount Q2 exceeds the radiation heat input amount Q1 (or its absolute value) (S3b: NO), the acquired heat amount Q is negative. In this case, if the heat medium M passes through the solar thermal collecting panel 2, there is a risk that the temperature of the heat medium M will decrease. If the acquired heat amount Q is negative, the flow of the heat medium M is stopped (step S5), thereby preventing the temperature of the heat medium M from decreasing.

[0073] Figure 5 shows the time changes of the amount of radiant heat input Q1, the outside air temperature Tair, and the panel temperature Tp on a clear day from before sunrise to after sunset. The horizontal axis shows time. The vertical axis shows the amount of heat (W) or temperature (K) per unit time on an arbitrary scale.

[0074] The amount of radiation heat input Q1 is proportional to the amount of global solar radiation Wsun. Therefore, although not shown in the figure, the amount of global solar radiation Wsun changes over time in the same way as the amount of radiation heat input Q1. The amount of convection heat transfer Q2 depends on the temperature difference between the outside air temperature Tair and the panel temperature Tp. Therefore, the greater the temperature difference (the difference in the vertical axis coordinate between the outside air temperature Tair and the panel temperature Tp at the same time), the greater the absolute value of the amount of convection heat transfer Q2. When the outside air temperature Tair is higher than the panel temperature Tp (see the area hatched downward to the right), the amount of convection heat transfer Q2 is positive. When the outside air temperature Tair is lower than the panel temperature Tp (see the area hatched upward to the right), the amount of convection heat transfer Q2 is negative.

[0075] The amount of radiant heat input Q1 and the amount of global solar radiation Wsun reach their maximum value at the time of meridian and move linearly symmetrically around the time of meridian. This is because the example shows a day with clear skies all day, and the amount of radiant heat input Q1 and the amount of global solar radiation Wsun can change in a complex manner depending on the amount of cloud cover.

[0076] The outdoor air temperature Tair also changes in the same way as the global solar radiation Wsun, and reaches a maximum value near the meridian. In contrast, the panel temperature Tp reaches a maximum value at a time later than the meridian. After sunrise, the panel temperature Tp rises toward the maximum value, but continues to stay lower than the outdoor air temperature Tair. The panel temperature Tp exceeds the outdoor air temperature Tair at time t1 in the process of rising to the maximum value. Time t1 is around the meridian. After reaching the maximum value, the panel temperature Tp decreases while remaining higher than the outdoor air temperature Tair.

[0077] In the time period before time t1, the convection heat transfer amount Q2 is positive, so the heat medium M flows and the temperature of the heat medium M in the heat medium tank 3 rises. At time t1, the convection heat transfer amount Q2 changes from positive to negative. Immediately after time t1, the temperature difference is small and the absolute value of the convection heat transfer amount Q2 is small. On the other hand, since time t1 is near noon, sufficient solar radiation is obtained. The radiant heat input amount Q1 greatly exceeds the absolute value of the convection heat transfer amount Q2, and the acquired heat amount Q becomes positive. Therefore, even if the convection heat transfer amount Q2 turns negative, the heat medium M continues to flow and the acquired heat amount Q continues to be recovered by the heat medium M.

[0078] After that, the temperature difference continues to widen until the time when the panel temperature Tp reaches its maximum value. As sunset approaches, the temperature difference does not narrow, and the total solar radiation Wsun and therefore the radiant heat input Q1 decrease significantly. At time t2, when the radiant heat input Q1 reaches the absolute value of the convective heat transfer Q2, the heat gain Q turns from positive to negative. At time t2, the flow of the heat medium M stops, preventing the temperature of the heat medium M from dropping in the time period after time t2.

[0079] According to the solar heat collecting system 1 of this embodiment, the solar heat collecting panel 2 positively has a non-insulated portion 2c that is expected to cause convective heat transfer with the surrounding air. Therefore, in the solar heat collecting panel 2, not only radiant heat from sunlight but also convective heat from the surrounding air can be transferred to the heat medium M, and the amount of heat acquired Q in the solar heat collecting panel 2 increases. Furthermore, switching between allowing and not allowing the heat medium M to circulate or adjusting the amount of heat medium M circulating is performed based on the amount of radiant heat input Q1 and the amount of convective heat transfer Q2. Therefore, heat recovery by the heat medium M is optimized.

[0080] Specifically, the control device 9 controls the heat medium flow control mechanism 5 to stop the supply of the heat medium M to the solar thermal collecting panel 2 when the convection heat transfer amount Q2 is negative and the radiation heat input amount Q1 is less than the absolute value of the convection heat transfer amount Q2. As a result, the supply of the heat medium is stopped when the convection heat transfer amount Q2 going out from the solar thermal collecting panel 2 to the surrounding air exceeds the radiation heat input amount Q1 received by the solar thermal collecting panel 2. In other words, since the supply of the heat medium M is stopped when the acquired heat amount Q is negative, it is possible to prevent the temperature of the heat medium M from decreasing in the solar thermal collecting panel 2.

[0081] Conversely, even if the convection heat transfer amount Q2 is negative, when the radiation heat input amount Q1 is equal to or greater than the absolute value of the convection heat transfer amount Q2, the control device 9 controls the heat medium flow control mechanism 5 so that the heat medium M is supplied to the solar thermal collecting panel 2. As a result, if the acquired heat amount Q is positive, the acquired heat amount can be recovered by the heat medium M.

[0082] The radiation heat input Q1 is measured sequentially as a heat quantity per unit time based on the measurement result of the global solar radiation Wsun, which may change from moment to moment. The convection heat transfer Q2 is also measured sequentially as a heat quantity per unit time based on the measurement result of the temperature difference between the outside air temperature Tair and the panel temperature Tp, which may change from moment to moment. Based on such radiation heat input Q1 and convection heat transfer Q2, the heat acquisition Q is also evaluated as a heat quantity per unit time. Therefore, it is possible to improve the followability of the control to the environmental change, and to optimize the heat recovery by the heat medium M. For example, it is also possible to immediately stop the pump 5a in response to a sudden increase in cloud cover or an increase in the outside temperature, thereby preventing heat loss from the heat medium M.

[0083] Returning to Fig. 1, the heat thus collected by the heat medium M may be utilized in an agricultural greenhouse 90. The agricultural greenhouse 90 is a suitable application example of the solar heat collecting system 1 according to this embodiment.

[0084] The agricultural house 90 is constructed on a substantially horizontal rectangular site. The agricultural house 90 has a framework 91 formed of steel or aluminum extrusion. The framework 91 is entirely covered with an outer skin (not shown) formed of a light-transmitting material (e.g., polyvinyl chloride). This protects the interior of the agricultural house 90 from wind and rain. The framework 91 includes columns 91a erected at the four corners of the site and between them, girders and beams 91b horizontally installed on the upper ends of the columns 91a, and a roof 91c installed on the girders and beams 91b. The roof shape is not particularly limited, and may be, for example, a gabled or arched shape. In the agricultural house 90, a plant 99 is planted in a culture medium 98. The plant 99 is preferably an agricultural crop. The culture medium 98 is a growth medium for the plant 99, and is appropriately selected from soil, rock wool, culture solution, and the like, taking into consideration compatibility with the plant 99 to be cultivated.

[0085] The solar heat collecting system 1 is used to assist the growth of the plants 99. The temperature of the culture medium 98 and the plants 99 may be adjusted by the heat collected by the heat medium M. In this case, the solar heat collecting panel 2 is preferably installed directly under the roof 91c of the agricultural house 90 (inside the agricultural house 90) with the light receiving portion 2b facing south. Since the roof is transparent and the air inside the agricultural house 90 is heated by sunlight, the solar heat collecting panel 2 can collect not only the radiant heat input from the sunlight penetrating the transparent roof, but also the convective heat transfer from the heated air inside the agricultural house 90. By placing the heat medium tank 3 inside the agricultural house 90, a heat insulating effect by the air inside the agricultural house 90 can be expected. It is to be noted that the heat medium tank 3 may be placed outside the agricultural house 90, but in that case, the tank structure is required to have a higher heat insulating property than when it is placed inside the agricultural house 90. A similar effect can be obtained by installing the solar heat collecting panel 2 on the roof or wall of a building such as a building, and it is expected that radiant heat and convective heat from the building structure heated by sunlight can be collected.

[0086] Second embodiment Next, with reference to FIG. 6, a solar heat collecting system 1 according to a second embodiment will be described, focusing on the differences from the first embodiment.

[0087] In this embodiment, the heat medium tank 3 includes a first heat medium tank 3a and a second heat medium tank 3b that is separate from the first heat medium tank 3a. The inflow line 4a connects the first heat medium tank 3a to the inlet of the solar thermal collecting panel 2, and sends the heat medium M from the first heat medium tank 3a to the hollow portion 2a. The outflow line 4b connects the outlet of the solar thermal collecting panel 2 to the second heat medium tank 3b, and sends the heat medium M from the hollow portion 2a to the second heat medium tank 3b.

[0088] In this case, the heat medium M after heat recovery is stored in the second heat medium tank 3b, so the heat medium M in the first heat medium tank 3a is maintained at a low temperature. This allows the panel temperature Tp to be maintained at a low temperature, and the amount of convective heat transfer Q2 to be maintained at a high positive value. Therefore, the amount of heat Q gained by the solar heat collecting panel 2 can be increased.

[0089] Third embodiment Next, with reference to FIG. 7, a solar heat collecting system 1 according to a third embodiment will be described, focusing on the differences from the second embodiment.

[0090] In this embodiment, the heat medium tank 3 also includes a first heat medium tank 3a and a second heat medium tank 3b separate from the first heat medium tank 3a. The heat medium circulation line 4 includes an inlet line 4a and an outlet line 4b, similar to the second embodiment. The heat medium circulation line 4 further includes a return line 4c that branches off from the outlet line 4b and returns the heat medium M to the first heat medium tank 3a.

[0091] The heat medium flow control mechanism 5 includes a three-way valve 5c provided on a branch point of the return line 4c from the outflow line 4b. The three-way valve 5c is an example of a direction switching mechanism that switches the direction of sending the heat medium M. The three-way valve 5c switches between a state in which the heat medium M flowing out from the solar thermal collecting panel 2 is sent to the second heat medium tank 3b via the outflow line 4b, and a state in which the heat medium M flowing out from the solar thermal collecting panel 2 is returned to the first heat medium tank 3a via the return line 4c. The three-way valve 5c is an electromagnetic 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, if the value of the heat acquisition Q (=Q1+Q2) calculated by the control device 9 is greater than a reference value arbitrarily set by the user, the heat medium M is returned to the first heat medium tank 3a to become a high-temperature heat medium, and if it is smaller than the reference value, the heat medium M is sent to the second heat medium tank 3b to maximize the amount of heat collected, by controlling the switching of the three-way valve 5c.

[0092] According to this embodiment, it is possible to switch between a state in which the temperature of the heat medium M supplied to the solar heat collecting panel 2 is kept low and a state in which the heat medium M is kept warm, depending on the situation.

[0093] (Fourth embodiment) Next, with reference to FIG. 8, a solar heat collecting system 1 according to a fourth embodiment will be described, focusing on the differences from the first embodiment.

[0094] In this embodiment, the heat medium tank 3 is a single tank, as in the first embodiment. However, the heat medium tank 3 is a stratified type. That is, the heat medium tank 3 has an outlet provided at the bottom and an inlet provided at the top. A relatively low-temperature heat medium M is stored at the bottom, and a relatively high-temperature heat medium after heat recovery is stored at the top. There is no active convection in the heat medium tank 3, so the same heat medium M with different temperatures is stored in two layers. The inflow line 4a connects the outlet of the heat medium tank 3 to the inlet of the solar thermal collection panel. The outflow line 4b connects the outlet of the solar thermal collection panel 2 to the inlet of the heat medium tank 3.

[0095] According to this embodiment, the amount of convective heat transfer Q2 can be maintained at a high positive value, similarly to the second embodiment, without increasing the number of tanks, and the amount of heat acquired Q of the solar heat collecting panel 2 can be increased.

[0096] (Modification) Although the embodiment has been described above, the above configuration can be modified as appropriate within the scope of the present invention.

[0097] The panel body 11 of the solar thermal collecting panel 2 is not limited to an aluminum alloy extrusion material, and may be manufactured using other materials and manufacturing methods. For example, the panel body 11 may be formed by overlapping two aluminum plates. In this case, a groove is formed in at least one of the plates. The groove is closed by the other plate to form a hollow portion. Steel or copper may be used as a material other than aluminum.

[0098] There may be provided a plurality of solar thermal collecting panels 2. In this case, the inflow line 4a connects the heat medium tank 3 to a plurality of inlets in parallel, and the outflow line 4b connects the heat medium tank 3 to a plurality of outlets in parallel.

[0099] The control device 80 may control the heat medium flow control mechanism 5 so as to adjust the flow rate of the heat medium M based on the amount of acquired heat Q.

[0100] The solar heat collecting system 1 can be applied to purposes other than the agricultural greenhouse 90. For example, it may be installed in a structure such as a building or a house, and used to generate hot water to be used in the structure.

[0101] The present disclosure may include the following aspects. (Aspect 1) a solar heat collecting panel having a hollow portion for circulating a heat medium, a light receiving portion for receiving sunlight, and a non-insulated portion for performing convective heat transfer between the solar light and the surrounding air, and transferring radiant heat from the sunlight and convective heat from the surrounding air to the heat medium; A heat transfer medium tank for storing the heat transfer medium; a heat medium circulation line for sending the heat medium from the heat medium tank to the solar heat collecting panel and sending the heat medium from the solar heat collecting panel to the heat medium tank; A heat medium flow control mechanism that performs at least one of switching whether or not the heat medium flows along the heat medium circulation line and adjusting a flow rate of the heat medium; A control device, The control device, Measure the amount of radiant heat input to the solar heat collecting panel; Measure the amount of convective heat transfer between the solar thermal collection panel and the ambient air; The heat medium flow control mechanism is controlled based on the amount of radiant heat input and the amount of convective heat transfer. Solar heat collection system. (Aspect 2) When the convective heat is transferred from the solar thermal collection panel to the surrounding air, the convective heat transfer amount becomes negative, The control device controls the heat medium flow control mechanism to stop the supply of the heat medium to the solar thermal collection panel when the convection heat transfer amount is negative and the radiation heat input amount is less than an absolute value of the convection heat transfer amount. 2. The solar thermal collecting system of embodiment 1. (Aspect 3) The control device controls the heat medium flow control mechanism so that the heat medium is supplied to the solar thermal collecting panel when the convection heat transfer amount is negative and the radiation heat input amount is equal to or greater than the absolute value of the convection heat transfer amount. 3. The solar heat collecting system according to claim 1 or 2. (Aspect 4) The control device controls the heat medium flow control mechanism so that the heat medium is supplied to the solar heat collecting panel when the convection heat transfer amount is positive. 4. The solar heat collecting system according to any one of aspects 1 to 3. (Aspect 5) Further comprising a pyranometer for measuring total solar radiation, The control device measures the amount of radiant heat input as a heat amount per unit time based on the amount of global solar radiation measured by the pyranometer and a surface area of ​​the light receiving unit. 5. The solar thermal collecting system according to any one of aspects 1 to 4. (Aspect 6) an outside air temperature sensor for measuring the temperature of the air surrounding the solar thermal collection panel; A panel temperature sensor for measuring the temperature of the solar heat collecting panel side, The control device measures the convective heat transfer amount as a heat amount per unit time based on the difference between the temperatures measured by the outside air temperature sensor and the panel temperature sensor, the outer surface area of ​​the non-insulated portion, and the convective heat transfer coefficient of the non-insulated portion. 6. The solar thermal collecting system according to any one of aspects 1 to 5. (Aspect 7) The panel temperature sensor is composed of at least one of a surface temperature sensor that measures a surface temperature of the non-insulated portion, an inlet temperature sensor that measures a temperature near the inlet of the hollow portion, and an outlet temperature sensor that measures a temperature near the outlet of the hollow portion. 7. The solar thermal collecting system of embodiment 6. (Aspect 8) The heat medium tank includes a first heat medium tank and a second heat medium tank separate from the first heat medium tank, The heat medium circulation line includes an inlet line for sending the heat medium from the first heat medium tank to the hollow portion, and an outlet line for sending the heat medium from the hollow portion to the second heat medium tank. 8. The solar thermal collecting system according to any one of embodiments 1 to 7. (Aspect 9) The heat medium circulation line further includes a return line branching from the outflow line and returning the heat medium to the first heat medium tank; The heat medium flow control mechanism includes a direction switching mechanism that switches between a state in which the heat medium is sent to the second heat medium tank through the outflow line and a state in which the heat medium is returned to the first heat medium tank through the return line. 9. The solar thermal collecting system of embodiment 8. (Aspect 10) The heat transfer medium tank is a stratified type having an outlet at the bottom and an inlet at the top, The heat medium circulation line includes an inlet line connecting the outlet of the heat medium tank to the hollow portion, and an outlet line connecting the hollow portion to the inlet of the heat medium tank. 8. The solar thermal collecting system according to any one of embodiments 1 to 7. [Explanation of symbols]

[0102] 1. Solar heat collection system 2. Solar heat collector panels 2a Hollow part 2b Light receiving part 2c Non-insulated section 3 Heat Transfer Tank 3a First heat transfer tank 3b Second heat transfer tank 4 Heat transfer medium circulation line 4a Inlet line 4b Outlet line 4c Return Line 5 Heat transfer medium flow control mechanism 5a Pump 5b Valve 5c Three-way valve 6 Pyranometer 7. Outside Air 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 1st main wall 11b 2nd main wall 11c side wall 11d Bulkhead 12 First Header 13 Second Header 12a,13a Lid plate 12b,13b Peripheral wall 12c,13c interior space 14 Entrance 15 Exit 90 Agricultural House 91 Body 91a Pillar 91b Beam 91c roof 98 pedi 99 Plants Ap Surface area Asun Light receiving area M Heat Media Q1 Radiated heat Q2 heat flow Tair external temperature Tp temperature Tin inlet temperature Tout outlet temperature Tsf Surface temperature Wsun Total daily solar radiation α emissivity μ Current heat transfer rate

Claims

1. a solar heat collecting panel having a hollow portion for circulating a heat medium, a light receiving portion for receiving sunlight, and a non-insulated portion for performing convective heat transfer between the solar light and the surrounding air, and transferring radiant heat from the sunlight and convective heat from the surrounding air to the heat medium; A heat transfer medium tank for storing the heat transfer medium; a heat medium circulation line for sending the heat medium from the heat medium tank to the solar heat collecting panel and sending the heat medium from the solar heat collecting panel to the heat medium tank; A heat medium flow control mechanism that performs at least one of switching whether or not the heat medium flows along the heat medium circulation line and adjusting a flow rate of the heat medium; A control device, The control device, Measure the amount of radiant heat input to the solar heat collecting panel; Measure the amount of convective heat transfer between the solar thermal collection panel and the ambient air; The heat medium flow control mechanism is controlled based on the amount of radiant heat input and the amount of convective heat transfer. Solar heat collection system.

2. When the convective heat is transferred from the solar thermal collection panel to the surrounding air, the convective heat transfer amount becomes negative, The control device controls the heat medium flow control mechanism to stop the supply of the heat medium to the solar thermal collection panel when the convection heat transfer amount is negative and the radiation heat input amount is less than the absolute value of the convection heat transfer amount. The solar heat collecting system according to claim 1 .

3. The control device controls the heat medium flow control mechanism so that the heat medium is supplied to the solar thermal collection panel when the convection heat transfer amount is negative and the radiation heat input amount is equal to or greater than the absolute value of the convection heat transfer amount. The solar heat collecting system according to claim 2 .

4. The control device controls the heat medium flow control mechanism so that the heat medium is supplied to the solar heat collecting panel when the convection heat transfer amount is positive. The solar heat collecting system according to claim 2 .

5. Further comprising a pyranometer for measuring total solar radiation, The control device measures the amount of radiant heat input as a heat amount per unit time based on the amount of global solar radiation measured by the pyranometer and a surface area of ​​the light receiving unit. The solar heat collecting system according to any one of claims 1 to 4.

6. an outside air temperature sensor for measuring the temperature of the air surrounding the solar thermal collection panel; A panel temperature sensor for measuring the temperature of the solar heat collecting panel side, The control device measures the convective heat transfer amount as a heat amount per unit time based on the difference between the temperatures measured by the outside air temperature sensor and the panel temperature sensor, the outer surface area of ​​the non-insulated portion, and the convective heat transfer coefficient of the non-insulated portion. The solar heat collecting system according to any one of claims 1 to 4.

7. The panel temperature sensor is composed of at least one of a surface temperature sensor that measures a surface temperature of the non-insulated portion, an inlet temperature sensor that measures a temperature near the inlet of the hollow portion, and an outlet temperature sensor that measures a temperature near the outlet of the hollow portion. The solar heat collecting system according to claim 6.

8. The heat medium tank includes a first heat medium tank and a second heat medium tank separate from the first heat medium tank, The heat medium circulation line includes an inlet line for sending the heat medium from the first heat medium tank to the hollow portion, and an outlet line for sending the heat medium from the hollow portion to the second heat medium tank. The solar heat collecting system according to any one of claims 1 to 4.

9. The heat medium circulation line further includes a return line branching from the outflow line and returning the heat medium to the first heat medium tank, The heat medium flow control mechanism includes a direction switching mechanism that switches between a state in which the heat medium is sent to the second heat medium tank through the outflow line and a state in which the heat medium is returned to the first heat medium tank through the return line. The solar heat collecting system according to claim 8.

10. The heat transfer medium tank is a stratified type having an outlet at the bottom and an inlet at the top, The heat medium circulation line includes an inlet line connecting the outlet of the heat medium tank to the hollow portion, and an outlet line connecting the hollow portion to the inlet of the heat medium tank. The solar heat collecting system according to any one of claims 1 to 4.

Images