Agricultural heat complementary method and system

Abstract

The invention provides an agricultural heat complementary method and system, and aims to improve the farmland utilization efficiency and promote the development of renewable energy sources. Solar two-way vacuum heat collection pipes which are arranged in a line and communicated end to end are installed in the length direction of a bearing cable, and therefore a solar heat collection suspension cable is formed. And the solar heat collection suspension cable is suspended above a farmland. The system is super large in span and few in pile foundation, operation of a large agricultural machine is not hindered, shadow does not affect photosynthesis, cultivated land can be normally cultivated, and irrigation, light supplementing and rat repelling can be achieved. The application develops a broad new field in which solar heat collection is not affected by farmland planting.

Description

Technical Field

[0001] The present application belongs to the technical fields of solar energy collection and agricultural production, and specifically relates to a method and system for collecting solar energy from above the land - an agricultural heat complementary method and system. Background Art

[0002] The applicant's patent "Off-grid heat storage solar all-weather tobacco curing method (CN117547055A)" discloses a solar tobacco curing system and method. It includes a curing box, a solar collector or a solar photovoltaic power generation system, a heat storage container and a heat storage medium, an electric control valve, a liquid pump or a heat transfer pipe, a temperature control sensor and a controller and other components. It does not need to extend the power grid to the fields in remote mountainous areas, nor does it need to convert solar energy into electrical energy for storage. It can directly or indirectly use the thermal energy of solar energy to bake tobacco leaves and other materials day and night. It abandons the link of first converting solar energy into electrical energy for storage, and then converting electrical energy into thermal energy for use, and completely relies on solar energy (as a clean energy) to heat and bake tobacco leaves and other materials. This technology makes tobacco leaf curing production more energy-saving and environmentally friendly, and is expected to reduce curing costs.

[0003] However, in recent practice at the tobacco planting base in Honghe Prefecture, Yunnan Province, a problem was discovered: the solar vacuum collector tube array needs to occupy a large area of ​​farmland. To build a standard tobacco curing field with 100 curing houses, the solar vacuum collector tube array alone needs to occupy 25 mu of farmland. This huge land demand has caused the project to encounter some significant obstacles. Summary of the invention

[0004] One of the purposes of this application is to provide an agricultural-thermal complementary method and system so as not to occupy land, thereby improving land utilization efficiency and promoting the development of renewable energy.

[0005] The second purpose of this application is to provide an agricultural heat complementary system so as not to occupy land, thereby improving land use efficiency and promoting the development of renewable energy.

[0006] In order to achieve one of the above-mentioned purposes of the invention, the present application provides an agricultural-thermal complementation method as follows.

[0007] The present application provides an agricultural-thermal complementary method, characterized in that it comprises the following steps: ① Connect n solar double-pass vacuum heat collecting tubes with a diameter of D in a row and connected end to end along the length direction of the load-bearing cable to form a solar heat collecting string, wherein n ≥ 5 or 10 or 30 or 100 or 200; the solar double-pass vacuum heat collecting tube is a mature product on the market, and its specific technology is not described here. Please refer to the utility model patents "A double-pass solar vacuum tube with a gourd knot (CN211716906U)", "Double-pass solar vacuum tube with an expansion knot (CN203880985U)" and other patent materials; ② Multiple solar collector strings are spaced at a certain distance and suspended above the ground through tall supports; the height of the solar collector string from the top of the plant is set to H, the span of a single span of the solar collector string is set to L, and the horizontal projection spacing of the solar collector string is set to K; where H ≥ 1m or 2m or 5m or 10m or 20m or 30m, L ≥ 10m or 20m or 50m or 100m or 200m or 500m, and K ≥ 0.2m or 0.5 or 1m or 2m or 5m; ③ Increase the spacing of solar collector strings so that the ratio of the horizontal projection width D (equal to the diameter D of the double-pass vacuum collector tube) of the solar collector string to the horizontal projection spacing K - shading coefficient: D / K≤0.02 or 0.03 or 0.05 or 0.1 or 0.2 or 0.3 or 0.5 or 1, and the ratio of the horizontal projection spacing K to the height H of the solar collector string - spacing-to-height ratio: K / H≤0.1 or 0.5 or 1 or 2, so that the shadow moves quickly and avoid the same midday shadow passing over the same plant for more than 30 minutes.

[0008] Preferably, the agricultural heat complementary method is characterized in that: the solar double-pass vacuum collector tubes are connected by an insulated pipe joint, and the air in the pipe is used as a heat transfer medium to transport hot air from one end of the solar collector string to the other end; or, a water pipe is passed through the solar double-pass vacuum collector tube, and water is used as a heat transfer medium to transport hot water from one end of the solar collector string to the other end.

[0009] Preferably, the agricultural heat complementary method is characterized in that: the solar energy collector string is used as an irrigation water pipe; and a water outlet hole is opened on the insulation pipe joint to discharge water for irrigation.

[0010] Preferably, the agricultural-thermal complementary method is characterized in that it includes any one or more of the following technical measures ① to ⑦: ① Attach an irrigation pipe to the solar collector string to integrate the solar collector string with the irrigation pipe, thereby sharing a load-bearing cable and its tall support; ② Install speakers on the solar collector string to play sounds to drive away birds and mice or play music that plants like to promote plant growth; ③ Install supplementary light on the solar thermal collection string to supplement light for light-loving plants at night to promote plant growth; ④L is 10-320m, D / K≤0.25, H≥1m; ⑤The solar collector string is hung along the north-south direction; ⑥The solar double-pass vacuum collector tube is suspended directly below the load-bearing cable and is arranged in the same direction as the load-bearing cable; ⑦ Increase the height H of the solar collector string from the top of the plant and reduce the shading coefficient D / K, so that the midday shadow of the solar collector string falling on the ground can quickly pass through the plant as the sun moves, ensuring that each midday shadow moves a distance of one midday shadow width every 1-20 minutes, so as to avoid the same shadow staying in the same position on the same plant for too long, which will weaken the photosynthesis of the plant and reduce the yield.

[0011] The present application provides an agricultural heat complementary system, characterized in that it comprises: ① A solar energy double-pass vacuum heat collecting tube string with a diameter of D, which is connected in series along the length direction of the load-bearing cable and is arranged end to end, and is a solar energy heat collecting string; wherein n ≥5 or 10 or 30 or 100 or 200; ② A tall support standing on the ground and a plurality of solar collector strings suspended thereon, located above the ground and spaced a certain distance apart; the height of the solar collector string from the top of the plant is H, the span of a single span of the solar collector string is L, and the horizontal projection spacing of the solar collector string is K; wherein, H ≥ 1m or 2m or 5m or 10m or 20m or 30m, L ≥ 10m or 20m or 50m or 100m or 200m or 500m, K ≥ 0.2m or 0.5 or 1m or 2m or 5m or 10m; ③ The shadow cast by the solar collector string on the ground, including the horizontal projection; among them, the ratio of the horizontal projection width D of the solar collector string to the horizontal projection spacing K - shading coefficient: D / K≤0.02 or 0.03 or 0.05 or 0.10 or 0.20 or 0.30 or 0.50 or 1, the ratio of the horizontal projection spacing K of the solar collector string to the height H - height ratio: K / H≤0.1 or 0.5 or 1 or 2.

[0012] Preferably, the agricultural heat complementary system is characterized in that: the solar double-pass vacuum collector tubes are connected by thermal insulation pipe joints, the air in the tubes is the heat transfer medium, and hot air can be transported from one end of the solar collector string to the other end; or, a water pipe passes through the solar double-pass vacuum collector tubes, water is the heat transfer medium, and hot water can be transported from one end of the solar collector string to the other end.

[0013] Preferably, the agricultural heat complementary system is characterized in that: the solar collector string is also used as an irrigation water pipe; and a water outlet hole is opened on the insulation pipe joint for water outlet irrigation.

[0014] Preferably, the agricultural heat complementary system includes any one or more of the following technical features ① to ⑦: ① An irrigation water pipe is attached to the solar thermal collector string to integrate the solar thermal collector string with the water delivery irrigation water pipe, thereby sharing a load-bearing cable and its towering support; ② A speaker is installed on the solar collector string to play sounds to drive away birds and mice or to play music that plants like to promote plant growth; ③ A supplementary light is installed on the solar collector string to supplement light for light-loving plants at night to promote plant growth; ④L is 10-320m, D / K≤0.25, H≥1m; ⑤The solar collector string is hung along the north-south direction; ⑥The solar double-pass vacuum collector tube is suspended below the load-bearing cable and is arranged in the same direction as the load-bearing cable; ⑦ The height H of the solar collector string from the top of the plant is high enough and the shading coefficient D / K is small enough to ensure that each midday shadow moves a distance of one midday shadow width every 1-20 minutes.

[0015] Research shows that when choosing the shading coefficient, the principle of ensuring that the midday shadow of the solar collector string on the cultivated land can be quickly moved away from the plants should be followed: ensure that each midday shadow moves a distance of the width of the midday shadow every 1-20 minutes (preferably every 1-5 minutes) to avoid the same shadow staying on the same plant for too long (for example, more than 30 minutes), which will weaken the photosynthesis of the plant and reduce the yield. In order to unify the detection standards, the midday shadow is defined here as the shadow cast by the solar collector string on the ground by the sun at noon (i.e. from 11 a.m. to 13 p.m.).

[0016] Research shows that when the shading coefficient D / K≤0.25, the sunlight needed by plants will be blocked for 3-5 minutes every 20 minutes. If the shading is continuously released, the sunlight received by the plants will be reduced by 13-20% on average each time. Reducing sunlight by 13% will have no effect on the photosynthesis and yield of plants; reducing sunlight by 20% will have some effect on the photosynthesis and yield of plants. Therefore, it is not recommended to reduce sunlight by more than 20% in practice.

[0017] Studies have shown that the length of time a shadow stays on the same plant is inversely proportional to H and directly proportional to D. Taking Xiuying District, Haikou City as an example, the shadow movement speed of a solar collector string with a height of 50 meters in the north-south direction at noon on March 4 (11 o'clock) was 68cm / minute; if the height H of the solar collector string is reduced to 4.6 meters, the shadow movement speed will drop to 2.5cm / minute, and if the height H of the solar collector string is reduced to 1.2 meters, the shadow movement speed will drop to 0.6cm / minute. At noon on March 4 (13:30), the height H of the solar collector string was reduced to 5 meters, and the shadow movement speed will drop to 1.3cm / minute. By comparison, it is known that the shadow movement speed of the solar collector string in the east-west direction is very slow, and it only moves more than 1 meter in a whole day. In specific implementation, it should be avoided as much as possible to set up the solar collector string along the east-west direction. It can be seen that in order to reduce the impact of slow shadow movement on plant growth, the hanging height and H of the solar collector string should be increased as much as possible. Since the shadow stays on the plant for a long time when the height H is 1 meter, it will seriously affect the growth of the plant, so it is not recommended to use such a low height H.

[0018] In summary, in specific implementation, the height H should be preferably set to be above 2 m, preferably above 4 m; the horizontal projection spacing K should be preferably set to be above 0.5 m, preferably above 1 m, and D / K≤0.25.

[0019] In specific implementation, the shading coefficient D / K should be selected according to the types of plants in the cultivated land. For plants that need shading nets to adjust the light level and green mountains and rivers that do not care about yield, such as vegetable plants such as lettuce, lettuce, spinach, cabbage, mustard, celery, green forests, grasslands, etc., the shading coefficient D / K can be appropriately increased and the spacing of solar collector strings can be shortened.

[0020] Wen Xinyiyan replied: Farmland, forestland, mountainous land and grassland are collectively referred to as cultivated land. Cultivated land refers to land used for agricultural production, including farmland for cultivating plants, grassland for breeding, forestland for planting and felling timber, and mountainous land for animal husbandry and pasture. The cultivated land mentioned in this application refers to the ground where green plants can grow, including but not limited to forestland, grassland, farmland, green slopes, gullies, flower and tree orchards, and green waters and green mountains, including ditches, canals, roads and ridges within the cultivated land. In addition, it also includes the green belts in the middle of the road and on both sides.

[0021] Compared with the prior art, the present application has the following beneficial technical effects.

[0022] First, it does not occupy arable land: except for a small amount of land occupied by the pile foundation, it does not occupy arable land. Therefore, it can improve the efficiency of arable land use and promote the development of renewable energy.

[0023] Second, the span is large: the solar collector string of the present application connects the double-pass solar collector tubes in a row, which can greatly increase the span, does not occupy arable land, basically does not hinder large-scale agricultural mechanized production, and will not cause any ecological and environmental impact on the original plants in the arable land.

[0024] Third, solar energy collection and irrigation are combined into one: This application adds irrigation water pipes to the solar energy collection string, so that solar energy collection and water irrigation are cleverly and organically combined together, sharing load-bearing cables and high supports, which can be invested and constructed in one time, and the overall cost is greatly reduced.

[0025] Fourthly, heat collection, irrigation and supplementary light are integrated into one: the present application adds night supplementary light to the solar heat collection string, so that heat collection, water supply irrigation and installation of supplementary light are organically combined together, and load-bearing cables and high supports are shared, so the investment and construction can be done in one time, and the overall cost is greatly reduced.

[0026] Fifth, one land for two uses, agriculture and photovoltaic complementarity: The most beneficial technical effect of this application is that it cleverly develops and uses the surplus solar energy resources above the cultivated land, which not only does not occupy the cultivated land and does not affect agricultural and forestry production, but can increase the output value of the cultivated land. It can improve the single agricultural and forestry use of land, increase the value of land, alleviate the contradiction of tight land use for solar thermal collection, and promote the innovative development of complementary agriculture, forestry and clean energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the application of the agricultural heat complementary system of this application (Example 1) on a piece of cultivated land.

[0028] Figure 2 for Figure 1 Schematic diagram of the horizontal projection cross-sectional structure of seven solar collector strings on cultivated land.

[0029] Figure 3 for Figure 1 Schematic diagram of the structure of a solar collector string (internal pipe joint).

[0030] Figure 4 This is a schematic diagram of a solar collector string structure (external pipe connector) in this application.

[0031] Figure 5 This is a schematic diagram of a solar collector string structure with an irrigation water pipe in the present application (Example 2).

[0032] Figure 6 This is a schematic diagram of the structure of a solar collector string (drip irrigation) in the present application (Example 2).

[0033] Figure 7This is a schematic diagram of the structure of a solar collector string with a fill light in the present application (Example 3).

[0034] Figure 8 This is a schematic diagram of a solar collector string structure with a speaker in the present application (Example 4).

[0035] Explanation of the accompanying numbers: 1-solar collector string, 2-load-bearing cable, 3-solar double-pass vacuum collector tube, 301-solar single-pass vacuum collector tube, 302-insulation header, 4-insulation pipe joint, 5-suspension component, 6-high support, 601-support beam, 7-plant, 8-arable land, 9-shadow, 10-drip nozzle, 11-sunlight, 12-water pipe, 13-water droplets, 14-spraying water, 15-supplementary light, 16-speaker, 17-large agricultural machinery, 18-power supply wires, 19-hot air. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by this application easy to understand, this application is further explained below in conjunction with specific implementation methods.

[0037] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on this application. It should also be noted that, for the convenience of description, this application defines the length direction of the solar collector string as the longitudinal direction, and the direction perpendicular thereto as the transverse direction.

[0038] It should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", "communication", etc. should be understood in a broad sense. For example, "communication" can mean electrical communication or direct connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. Embodiment 1

[0039] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, according to the needs of the tobacco curing field with 100 curing houses in the background technology, thousands of solar energy collector strings 1 with a height of 15 meters and a spacing of 1 meter are set up in the sky above the cultivated land 8 near the tobacco curing field in the north-south direction.

[0040] In the first step, the load-bearing cable 2 (preferably with a high tensile strength of more than 1200 MPa) is suspended above the cultivated land 8 through a tall support 6 (similar to a power tower / pole) such as a support column or a cable tower higher than 15 meters, like erecting a high-voltage transmission line, with the interval distance set to 1 meter.

[0041] In order to reduce the number of pile foundations, the lateral spacing between the pile foundations can be appropriately increased to save floor space. For this purpose, the supporting beams 601 in the towering supports 6 may not be rigid beams, but flexible beams, such as very thick steel ropes (not shown).

[0042] The above-mentioned load-bearing cable 2 can be a φ15.2×3 galvanized prestressed steel cable, a high-strength fiber rope, a carbon fiber cable, an aramid cable, a glass fiber cable, a steel wire rope, a lightweight pipe or the like.

[0043] The second step is to purchase a batch of 2-meter-long solar double-pass vacuum collector tubes 3 with an outer diameter of φ70 and an inner diameter of φ60.

[0044] The third step is to purchase a batch of thermal insulation pipe joints 4 and their sealing rubber rings (not shown). The thermal insulation pipe joints 4 can be selected from internal plug-in pipe joints (such as Figure 3 ) can also use an external pipe connector (as shown in Figure 4 Then prepare some iron wires to make the hanging member 5.

[0045] The fourth step is to arrange the solar double-pass vacuum collector tubes 3 in a row along the length direction of the load-bearing cable 2 (preferably along the north-south direction), and connect them end to end with the insulation pipe joints 4 and their sealing rubber rings, so as to form a solar collector string 1 that is tens of meters or even hundreds of meters long.

[0046] It should be noted that, the height H of the solar collector string 1 from the top of the plant, the span L of the solar collector string, and the horizontal projection spacing K of the solar collector string should be set according to the height of the plant 7 according to local conditions; preferably, H ≥ 1m or 2m or 5m or 10m or 20m or 30m or 50m or 100m, L ≥ 10m or 20m or 50m or 100m or 200m or 500m, and K ≥ 0.2m or 0.5 or 1m or 2m or 5m.

[0047] It should also be noted that the spacing of the solar collector strings 1 should be set according to the needs of the plants so that the ratio of the width D of the horizontal projection 9 of the solar collector strings 1 to the spacing K of the horizontal projection 9 - the shading coefficient: D / K≤0.01 or 0.02 or 0.03 or 0.05 or 0.1 or 0.2 or 0.3 or 0.5 or 1.

[0048] Finally, as needed, an insulated gas pipeline can be installed according to the gas transmission requirements of the current solar vacuum tube heat collection system, and the hot air 19 can be transported to the tobacco curing field through the insulated gas pipeline (not shown).

[0049] Instead of using the air in the pipe as the heat transfer medium, heat transfer oil can be used as the heat transfer medium. For example, a heat transfer oil pipe (not shown) is passed through the solar double-pass vacuum heat collection pipe 3, and the heat oil is transported from one end of the solar heat collection string 1 to the other end, and the heat is transferred to the tobacco curing field by the heat transfer oil. Embodiment 2

[0050] like Figure 5 As shown, referring to the steps in the above embodiment, an irrigation pipe 12 can be attached to the solar thermal collector string 1 to integrate the solar thermal collector string 1 and the water delivery irrigation pipe 12 into one, sharing a load-bearing cable 2 and its towering support 6. In this way, the solar thermal collector system of the present application can also be used to spray water on the plants 7 according to the needs of drought.

[0051] like Figure 6 As shown, a drip nozzle 10 can also be connected to each insulation pipe joint 4. The drip nozzle 10 is a device used in a drip irrigation system. It can control the water flow so that the water is slowly released to the roots of the plants in the form of drips. It will not be described here. In this way, the plants 7 can be drip-irrigated at night through the solar double-pass vacuum collector tube 3, thereby achieving dual purposes of one tube, which can collect solar energy and also transport water for irrigation. Embodiment 3

[0052] like Figure 7 As shown, referring to the steps in the above embodiment, a power supply wire 18 and a supplementary light 15 can be attached to the solar thermal collector string 1, so that the solar thermal collector string 1, the supplementary light circuit and the supplementary light 15 (commonly known as a plant growth light) are integrated into one, sharing a load-bearing cable 2 and its towering support 6. In this way, according to the needs of the plants 7, the solar thermal collector system of the present application can also be used to supplement the light for the plants 7 at night to promote the growth of the plants 7. Embodiment 4

[0053] like Figure 8 As shown, referring to the steps in the above embodiment, a power supply wire 18 and a speaker 16 can be attached to the solar thermal collector string 1 to integrate the solar thermal collector string 1 with the broadcast circuit and the speaker 16, sharing a load-bearing cable 2 and its towering support 6. In this way, according to the needs of the plants 7, the solar thermal collector system of the present application can also be used to play music for the plants 7 to promote the growth of the plants 7. Of course, the sound of driving away birds and mice can also be played to protect the fruits of the plants 7.

[0054] In the specific implementation, the existing solar single-pass vacuum heat collecting tube 301 can also be used, connected in parallel through the insulation header 302, and then erected on the load-bearing cable 2, so as to form a solar heat collecting (horizontal) suspension ladder. Research shows that this (horizontal) suspension ladder structure is similar to the existing flexible photovoltaic bracket scheme, such as the utility model "A large-span hyperbolic suspension cable flexible photovoltaic bracket (CN219834036U)", which is complex, difficult to stabilize, easy to generate torque, and easy to be damaged by strong winds. Therefore, it is not recommended to use.

[0055] What is disclosed above is only a preferred embodiment of the present application. The drawings are merely schematic structural diagrams and are not drawn according to the actual size ratio. They cannot be used to limit the scope of rights of the present application. Equivalent changes made based on the claims of the present application still fall within the scope covered by the present application.

Claims

1. A method for agricultural heat complementation, characterized in that: It includes the following steps: ① Connect n solar double-pass vacuum heat collecting tubes with a diameter of D in series along the length direction of the load-bearing cable, which are arranged end to end and connected to form a solar heat collecting string, where n ≥ 5 or 10 or 30 or 100 or 200; ② Multiple solar collector strings are spaced at a certain distance and suspended above the ground through tall supports; the height of the solar collector string from the top of the plant is set to H, the span of a single span of the solar collector string is set to L, and the horizontal projection spacing of the solar collector string is set to K; where H ≥ 1m or 2m or 5m or 10m or 20m or 30m, L ≥ 10m or 20m or 50m or 100m or 200m or 500m, and K ≥ 0.2m or 0.5 or 1m or 2m or 5m; ③ Increase the spacing of solar collector strings so that the ratio of the horizontal projection width D (equal to the diameter D of the double-pass vacuum collector tube) of the solar collector string to the horizontal projection spacing K - shading coefficient: D / K≤0.02 or 0.03 or 0.05 or 0.1 or 0.2 or 0.3 or 0.5 or 1, and the ratio of the horizontal projection spacing K to the height H of the solar collector string - spacing-to-height ratio: K / H≤0.1 or 0.5 or 1 or 2, so that the shadow moves quickly and avoid the same midday shadow passing over the same plant for more than 30 minutes.

2. The agricultural-thermal complementary method according to claim 1, characterized in that: The solar double-pass vacuum collector tubes are connected by insulating pipe joints, and the air in the tube is used as a heat transfer medium to transport hot air from one end of the solar collector string to the other end; or a water pipe is passed through the solar double-pass vacuum collector tube, and water is used as a heat transfer medium to transport hot water from one end of the solar collector string to the other end.

3. The agricultural-thermal complementary method according to claim 2, characterized in that: The solar energy collector string is used as an irrigation water pipe; a water outlet hole is opened on the insulation pipe joint to discharge water for irrigation.

4. The agricultural-thermal complementary method according to claim 1, 2 or 3, characterized in that: It includes any one or more of the following technical measures: ① Attach an irrigation pipe to the solar collector string to integrate the solar collector string with the irrigation pipe, thereby sharing a load-bearing cable and its tall support; ② Install speakers on the solar collector string to play sounds to drive away birds and mice or play music that plants like to promote plant growth; ③ Install supplementary light on the solar thermal collection string to supplement light for light-loving plants at night to promote plant growth; ④L is 10-320m, D / K≤0.25, H≥1m; ⑤The solar collector string is hung along the north-south direction; ⑥The solar double-pass vacuum collector tube is suspended directly below the load-bearing cable and is arranged in the same direction as the load-bearing cable; ⑦ Increase the height H of the solar collector string from the top of the plant and reduce the shading coefficient D / K, so that the midday shadow of the solar collector string falling on the ground can quickly pass through the plant as the sun moves, ensuring that each midday shadow moves a distance of one midday shadow width every 1-20 minutes, so as to avoid the same shadow staying in the same position on the same plant for too long, which will weaken the photosynthesis of the plant and reduce the yield.

5. An agricultural heat complementary system, characterized in that: It includes: ① A solar energy double-pass vacuum heat collecting tube string with a diameter of D, which is connected in series along the length direction of the load-bearing cable and is arranged end to end, and is a solar energy heat collecting string; wherein n ≥5 or 10 or 30 or 100 or 200; ② A tall support standing on the ground and a plurality of solar collector strings suspended thereon, located above the ground and spaced a certain distance apart; the height of the solar collector string from the top of the plant is H, the span of a single span of the solar collector string is L, and the horizontal projection spacing of the solar collector string is K; wherein, H ≥ 1m or 2m or 5m or 10m or 20m or 30m, L ≥ 10m or 20m or 50m or 100m or 200m or 500m, K ≥ 0.2m or 0.5 or 1m or 2m or 5m or 10m; ③ The shadow cast by the solar collector string on the ground, including the horizontal projection; among them, the ratio of the horizontal projection width D of the solar collector string to the horizontal projection spacing K - shading coefficient: D / K≤0.02 or 0.03 or 0.05 or 0.10 or 0.20 or 0.30 or 0.50 or 1, the ratio of the horizontal projection spacing K of the solar collector string to the height H - height ratio: K / H≤0.1 or 0.5 or 1 or 2.

6. The agricultural heat complementary system according to claim 5, characterized in that: The solar double-pass vacuum collector tubes are connected by insulating pipe joints, the air in the tube is the heat transfer medium, and hot air can be transported from one end of the solar collector string to the other end; or, a water pipe passes through the solar double-pass vacuum collector tube, water is the heat transfer medium, and hot water can be transported from one end of the solar collector string to the other end.

7. The agricultural heat complementary system according to claim 6, characterized in that: The solar collector string is also used as an irrigation water pipe; a water outlet hole is opened on the insulation pipe joint to discharge water for irrigation.

8. The agricultural heat complementary system according to claim 5, 6 or 7, comprising any one or more of the following technical features ① to ⑦: ① An irrigation water pipe is attached to the solar thermal collector string to integrate the solar thermal collector string with the water delivery irrigation water pipe, thereby sharing a load-bearing cable and its towering support; ② A speaker is installed on the solar collector string to play sounds to drive away birds and mice or to play music that plants like to promote plant growth; ③ A supplementary light is installed on the solar collector string to supplement light for light-loving plants at night to promote plant growth; ④L is 10-320m, D / K≤0.25, H≥1m; ⑤The solar collector string is hung along the north-south direction; ⑥The solar double-pass vacuum collector tube is suspended below the load-bearing cable and is arranged in the same direction as the load-bearing cable; ⑦ The height H of the solar collector string from the top of the plant is high enough and the shading coefficient D / K is small enough to ensure that each midday shadow moves a distance of one midday shadow width every 1-20 minutes.

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