A distributed point-focusing photothermal system

Abstract

A distributed point-focusing solar thermal system includes multiple solar collectors for collecting solar thermal energy, a working fluid for the solar collectors, and a mirror field for the solar collectors. The solar collectors are arranged in rows and columns, forming a matrix with multiple rows running north-south and columns running east-west. The mirror field is a square field centered on point O, the shadow cast by the solar collectors at noon on the spring or autumn equinox. The square mirror field is divided into a fixed mirror field area and a variable mirror field area. This distributed point-focusing solar thermal system improves the light-gathering efficiency of the concentrators, increases the ratio of mirror surface area to land area, improves land utilization, increases the effective irradiation area of ​​the solar collectors, effectively improves the utilization rate of light resources, reduces costs, and thus improves economic benefits.

Description

Technical Field

[0001] This invention relates to the field of tower-type photothermal concentrator technology, specifically to a distributed point-focusing photothermal system. Background Technology

[0002] As an important renewable energy source, solar energy has the advantages of abundant resources, long lifespan, wide distribution, safety, cleanliness, and reliable technology. Developing and utilizing solar energy can significantly reduce environmental pollution, alleviate the energy crisis, and is expected to become an important alternative energy source to fossil fuels.

[0003] Solar thermal concentrating and storage systems are a type of high-temperature utilization of solar thermal resources. The accumulated heat can be used for various heat-related applications such as steam generation and power generation. Based on different heat concentration methods, solar thermal power generation technologies can be divided into tower, trough, disc, and Fresnel types. Tower concentrating systems, with their high heat collection efficiency, high thermal conversion efficiency, high overall system efficiency, significant potential for cost reduction, and suitability for large-scale applications, have become the main direction for large-scale applications in the solar thermal industry. Solar tower systems are also known as centralized concentrating systems. They consist of many large solar reflectors, commonly called heliostats, installed over a large area. Each heliostat is equipped with a tracking mechanism to accurately reflect and concentrate sunlight onto a receiver at the top of a tall tower. The concentration ratio at the receiver can exceed 1000 times. Here, the absorbed solar energy is converted into heat energy, which is then transferred to the working fluid. However, the development of this technology is still hampered by many obstacles, mainly due to three reasons: first, the cost of heliostat tracking is too high; second, the land utilization rate of the heliostat field is low, making it impossible to achieve large-scale light concentration; and third, the bottom of the heliostat is severely obstructed, resulting in low efficiency in the effective utilization area. Therefore, the current cost of heat concentration in tower solar thermal systems remains high, and there is still a long way to go before it meets market requirements. Summary of the Invention

[0004] To address the above problems, this invention proposes a distributed point-focusing solar thermal system to solve one or more of the aforementioned technical issues. This invention can fully utilize solar energy resources and achieve optimal coordination.

[0005] To achieve the above technical solution, the present invention provides a distributed point-focusing solar thermal system, including multiple solar thermal collectors for collecting solar thermal energy, a thermal working fluid circulating in the solar thermal collectors, and a mirror field of the solar thermal collectors.

[0006] The solar collectors are arranged in rows and columns, meaning that multiple solar collectors are arranged in multiple rows along a north-south direction and in multiple columns along an east-west direction, forming a matrix distributed in both north-south and east-west directions.

[0007] The mirror field of the solar thermal collector is a square mirror field centered on point O, the shadow formed by the solar thermal collector at noon on the spring or autumn equinox.

[0008] The square mirror field of the solar collector is divided into two parts: a fixed mirror field area and a variable mirror field area. The fixed mirror field of the solar collector is located in the mirror field area close to the solar collector. The variable mirror field area of ​​the solar collector is located in m rows or n columns away from the solar collector, where m≥1 and n≥1.

[0009] The solar collector 1 is equipped with a dynamic tracking system on the concentrator 4 in the variable mirror field area.

[0010] Furthermore, the concentrator in the variable mirror field area of ​​the solar thermal collector dynamically tracks the four solar thermal collectors adjacent to the concentrator, selects one of the four solar thermal collectors, and then the concentrator focuses and reflects sunlight onto the selected solar thermal collector with maximum concentrating efficiency.

[0011] Furthermore, the semi-major axis of the square mirror field is r = 0.5h·tanθ ~ 3h·tanθ, where h is the height of the solar thermal collector and θ is the latitude of the distributed point focusing solar thermal system. This forms a square mirror field with a side length of 2r, centered on the shadow O point formed by the solar thermal collector at noon on the spring or autumn equinox.

[0012] Furthermore, a concentrating mirror is installed in the mirror field of the solar thermal collector, and the concentrating mirror is distributed with the shadow O point formed by the solar thermal collector at 12 noon on the spring or autumn equinox as the center.

[0013] Furthermore, the concentrator is equipped with a dual-axis automatic tracking system; the dual-axis automatic tracking system automatically tracks the changes in the azimuth and altitude angles of the sun, realizes real-time tracking of the sun, and always maintains maximum efficiency in reflecting and focusing sunlight onto the solar thermal collector.

[0014] Furthermore, the working fluid of the solar collector is a liquid, a gas, or a phase change fluid.

[0015] Furthermore, it also includes a solar collector mounting frame corresponding to each of the multiple solar collector devices; the solar collector mounting frame includes a column, a crossbeam, suspension wires, and ground wires; the column is fixed to the ground, the crossbeam is installed and fixed to the upper part of the column, and both ends of the crossbeam are fixed to the top of the column by suspension wires; the end of the crossbeam closest to the column is fixed to the ground by ground wires, thus assembling the solar collector mounting frame; the solar collector device is installed and fixed at the end of the crossbeam of the solar collector mounting frame away from the column.

[0016] Furthermore, the heat input and output pipes of the solar thermal collector are connected to the main pipe on the ground along the crossbeams and columns of the solar thermal collector's mounting frame, respectively.

[0017] Compared with the prior art, the present invention has the following advantages: through the design of the dynamic tracking system of the concentrator and the rational design of the square mirror field of the solar collector, the mirror surface utilization rate of the concentrator is improved, and the ratio of mirror surface area to land area is 1:2-1:3, thereby improving the land utilization rate; in addition, through the design of the solar collector mounting frame, the shading at the bottom of the solar collector is avoided, thereby increasing the effective irradiation area of ​​the solar collector. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall framework of the distributed point-focusing photothermal system of the present invention.

[0019] Figure 2 This is a mirror field design diagram of the solar thermal collector of the present invention.

[0020] Figure 3 This is a schematic diagram of the mirror field structure of the solar thermal collector of the present invention.

[0021] Figure 4 This is a schematic diagram of the mirror field movement time of the solar thermal collector of the present invention.

[0022] Figure 5 This is a schematic diagram of the mirror field corresponding to the solar thermal collector at different times according to the present invention.

[0023] Figure 6 This is a schematic diagram of the mounting frame of the solar thermal collector of the present invention.

[0024] In the diagram: 1. Solar collector; 21. Horizontal beam; 22. Column; 31. Suspended wire; 32. Ground wire; 4. Concentrating mirror; 5. Mirror field. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] Please refer to Figure 1The distributed point-focusing solar thermal system of the present invention shown includes: multiple solar thermal collectors 1 for collecting solar thermal energy, and a working fluid for the solar thermal collectors 1, wherein the working fluid is steam; the solar thermal collectors 1 are arranged in rows and columns, that is, multiple solar thermal collectors 1 are arranged in multiple rows in a north-south direction and in multiple columns in an east-west direction, forming a matrix distributed in the north-south and east-west directions; each solar thermal collector 1 has its own mirror field 5.

[0027] Please refer to Figure 2 As shown in Figures a and b, the mirror field 5 of the solar thermal collector is a square mirror field 5 formed with the shadow O point formed by the solar thermal collector 1 at noon (12 noon) on the spring or autumn equinox as the center. The semi-major axis r of the square mirror field 5 is determined by the height h of the solar thermal collector 1 and the latitude θ of the system, and r = 0.5h·tanθ ~ 3h·tanθ.

[0028] Please refer to Figure 2 As shown in Figure c, the area within the dashed line where the solar collector 1 is located is the mirror field 5 of the solar collector 1. The mirror field is a square with point O as the center and 2r as the side length.

[0029] Please refer to Figure 3 As shown, a series of concentrating mirrors 4 are installed in the mirror field 5 where the solar collector 1 is located. The concentrating mirrors 4 are arranged with the shadow O formed by the solar collector 1 at noon on the spring or autumn equinox as the center. The mirror surface of the concentrating mirror 4 at point O is perpendicular to the sunlight. Then, the other concentrating mirrors 4 are arranged in the north-south and east-west directions with point O as the center, so that all the concentrating mirrors 4 can concentrate the light while keeping the normal of the concentrating mirror 4 as parallel to the sunlight as possible, that is, the mirror surface of the concentrating mirror 4 is as perpendicular to the sunlight as possible. In addition, the distance between adjacent concentrating mirrors 4 should ensure that one concentrating mirror does not leave a shadow on the adjacent concentrating mirror, nor can it concentrate the light onto the back of the mirror in front.

[0030] To ensure that the concentrator 4 can concentrate sunlight onto the solar collector 1 with maximum efficiency, the concentrator 4 is equipped with a dual-axis automatic tracking system for the sun. The dual-axis automatic tracking system automatically tracks the changes in the azimuth and altitude angles of the sun to achieve real-time tracking of the sun and keep the mirror surface as perpendicular to the sunlight as possible at all times, so as to focus the sunlight onto the solar collector 1 it serves with maximum efficiency.

[0031] The square mirror field of the solar collector 1 is divided into two parts: a fixed mirror field area and a variable mirror field area. The fixed mirror field of the solar collector 1 is located in the mirror field area close to the solar collector 1. The variable mirror field of the solar collector 1 is located in m rows or n columns away from the solar collector 1, where m≥1 and n≥1. The concentrator 4 in the variable mirror field area of ​​the solar collector 1 is equipped with a dynamic tracking system. Depending on the time of day, the concentrator 4 in the variable mirror field area of ​​the solar collector 1 dynamically tracks the four solar collectors adjacent to it. As needed, it selects one of these four solar collectors to achieve its maximum light-gathering efficiency, and then focuses and reflects the sunlight onto that solar collector.

[0032] When the distributed point-focusing solar thermal system of this invention is working, the position of the shadow of the solar collector 1 under the sun varies at different times each day, depending on the sunrise and sunset. Consequently, the square mirror field of the solar collector 1 also changes. The new mirror field is centered on the new shadow point O of the solar collector 1, and the direction of the line connecting the direct below the solar collector 1 to the shadow point O is the direction of the new semi-major axis r, forming a new square mirror field. Please refer to [reference needed]. Figure 4 As shown, at noon, when the sun is due south, the mirror field of each solar collector 1 forms a square mirror field with the middle of the adjacent solar collectors as the dividing line. In the morning, when the sun is in the east or south-east direction, the shadows of each row of solar collectors 1 move west or north-west, and the mirror field of the solar collector 1 also moves west or north-west. In the afternoon, when the sun is in the west-southwest or west direction, the shadows of each row of solar collectors 1 move east-northeast or east, and the mirror field of the solar collector 1 also moves east-northeast or east. When the mirror field changes as described above, if the concentrator 4 of the adjacent solar collector changes its mirror field area and enters the new square mirror field, it is replaced by the solar collector 1 corresponding to the new square mirror field through a dynamic tracking system. Then, through a dual-axis automatic tracking system for the sun, the sunlight is concentrated and reflected onto the solar collector 1.

[0033] Taking a specific day in Beijing as an example, the position of the shadow cast by solar collector 1 under the sun varies at different times, and the square mirror field of solar collector 1 also changes. Please refer to... Figure 5 As shown, point A represents the sun's position at noon, point B represents the sun's position at a certain time in the afternoon, and point C represents the sun's position at a certain time in the morning. When the sun is at point A, the mirror field of solar collector 1 is as follows. Figure 5 The solid-line square centered at point O is shown; when the sun is at point B, the mirror field of solar collector 1 is as follows. Figure 5The solid square shown is partially overlapped with the dashed square centered at point O2; when the sun is at point C, the mirror field of solar collector 1 is as follows. Figure 5 The solid square shown has a partially overlapping dashed square centered at point O1; the overlapping part of the three squares is the fixed mirror field area of ​​the solar collector 1, and the part outside the fixed mirror field area in the solid square is the variable mirror field area; the mirror field outside the solid square mirror field, within the range of the two dashed square mirror fields, is the variable mirror field area of ​​the solar collector adjacent to the solar collector 1.

[0034] refer to Figure 6 The distributed point-focusing solar thermal system of the present invention also includes solar collector mounting frames corresponding to multiple solar collector devices 1. The solar collector mounting frame includes a column 22, a crossbeam 21, suspension wires 31, and a ground wire 32. The column 22 is fixed to the ground, and the crossbeam 21 is installed and fixed to the upper part of the column 22. Both ends of the crossbeam 21 are fixed to the top of the column 22 via suspension wires 31. The end of the crossbeam 21 closest to the column 22 is fixed to the ground via the ground wires 32, thus assembling the solar collector mounting frame. The solar collector device 1 is installed and fixed to the end of the crossbeam 21 of the solar collector mounting frame away from the column 22.

[0035] Furthermore, the input and output pipes of the heat working medium of the solar thermal collector 1 are connected to the main pipe on the ground along the crossbeam 21 and the column 22, respectively.

[0036] The distributed solar thermal system of this invention has the following beneficial effects:

[0037] 1. By designing the dynamic tracking system of the condenser lens 4, the cosine effect is reduced, the drift problem is solved, and the condenser lens can work efficiently in both the morning and afternoon, improving the mirror utilization rate of the condenser lens and increasing the overall focusing efficiency by more than 25%.

[0038] 2. Through the rational design of the square mirror field 5 of the solar thermal collector 1, one mirror can prevent another from casting a shadow, and the rear mirror blocks the light on the back of the front door, thereby improving the land utilization rate and achieving a mirror area to land area ratio of 1:2-1:3, which is more than twice as high as the current mirror area to land area ratio of 1:5-1:6.

[0039] 3. The design of the mounting frame of the solar collector 1, compared with the support column of the existing solar collector 1, means that the bottom of the solar collector 1 of the present invention is no longer blocked, thereby increasing the effective irradiation area of ​​the solar collector 1.

[0040] 4. In this invention, liquid, gas or phase change working fluid is used as the heat medium of solar thermal collector 1, which can be directly used for power generation and heating, thereby improving thermal utilization efficiency.

[0041] It should be noted that in the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0042] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A distributed point-focusing photothermal system, characterized in that: It includes multiple solar collectors for collecting solar thermal energy, a circulating heat transfer fluid within the solar collectors, and a mirror field for the solar collectors. The solar collectors are arranged in rows and columns, forming a matrix with north-south and east-west orientations. The mirror field is a square field centered on point O, the shadow cast by the solar collectors at noon on the spring or autumn equinox. A concentrator is installed within this square field. The square mirror field is divided into a fixed mirror field area and a variable mirror field area. The fixed mirror field is located close to the solar collectors. The variable mirror field is located in m rows or n columns away from the solar collectors, where m ≥ 1 and n ≥ 1. The concentrator in the variable mirror field area of ​​the device is equipped with a dynamic tracking system. Point A represents the position of the sun at noon, point B represents the position of the sun at a certain time in the afternoon, and point C represents the position of the sun at a certain time in the morning. When the sun is at point A, the mirror field of the solar collector is a solid square centered at point O. When the sun is at point B, the mirror field of the solar collector is a partially overlapping dashed square centered at point O2, which is slightly below the solid square. When the sun is at point C, the mirror field of the solar collector is a partially overlapping dashed square centered at point O1, which is slightly above the solid square. The overlapping part of the three squares is the fixed mirror field area of ​​the solar collector. The part outside the fixed mirror field area in the solid square is the variable mirror field area. The mirror field outside the solid square mirror field area, within the range of the two dashed square mirror fields, is the variable mirror field area of ​​the solar collector adjacent to the solar collector.

2. The distributed point-focusing photothermal system according to claim 1, characterized in that: The concentrator in the variable mirror field area of ​​the solar thermal collector dynamically tracks the four solar thermal collectors adjacent to the concentrator. It selects one of the four solar thermal collectors and then the concentrator focuses and reflects sunlight onto the selected solar thermal collector with maximum concentrating efficiency.

3. The distributed point-focusing photothermal system according to claim 1, characterized in that: The semi-major axis of the square mirror field is r = 0.5h·tanθ ~ 3h·tanθ, where h is the height of the solar thermal collector and θ is the latitude of the distributed point focusing solar thermal system. This forms a square mirror field with a side length of 2r, centered on the shadow O point formed by the solar thermal collector at noon on the spring or autumn equinox.

4. The distributed point-focusing photothermal system according to claim 1, characterized in that: A concentrating mirror is installed in the mirror field of the solar thermal collector, and the concentrating mirrors are distributed with the shadow O formed by the solar thermal collector at 12 noon on the spring or autumn equinox as the center.

5. A distributed point-focusing photothermal system according to claim 1, characterized in that: The concentrator is equipped with a dual-axis automatic tracking system; the dual-axis automatic tracking system automatically tracks the changes in the azimuth and altitude angles of the sun, realizes real-time tracking of the sun, and always maintains maximum efficiency in reflecting and focusing sunlight onto the solar thermal collector.

6. A distributed point-focusing photothermal system according to claim 1, characterized in that: The working fluid of the solar collector is a liquid, a gas, or a phase change fluid.

7. A distributed point-focusing photothermal system according to claim 1, characterized in that: It also includes solar collector mounting frames that correspond one-to-one with multiple solar collector devices; the solar collector mounting frame includes a column, a crossbeam, suspension wires, and ground wires; the column is fixed to the ground, the crossbeam is installed and fixed to the upper part of the column, and both ends of the crossbeam are fixed to the top of the column by suspension wires; the end of the crossbeam closest to the column is fixed to the ground by ground wires, thus assembling the solar collector mounting frame; the solar collector is installed and fixed to the end of the crossbeam of the solar collector mounting frame away from the column.

8. A distributed point-focusing photothermal system according to claim 1 or 7, characterized in that: The heat input and output pipes of the solar collector are connected to the main pipe on the ground through the crossbeams and columns of the solar collector's mounting frame.

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