Novel cylindrical surface reflector splicing groove type solar heat collection system

Abstract

The utility model discloses a novel cylindrical surface reflector spliced groove type solar heat collection system, which comprises a reflector group and a receiver, the reflector group is formed by splicing a plurality of strip-shaped cylindrical surface reflectors, the adjacent cylindrical surface reflectors are connected end to end and are tightly arranged, the whole spliced reflecting surface is a continuous surface, the strip-shaped cylindrical surface reflectors share a focal point, and the receiver is connected with the reflector group. The receiver is mounted on a common focus of the strip-shaped cylindrical surface reflectors, the receiver is a strip-shaped cavity receiver or a flat plate receiver, the centers of the strip-shaped cylindrical surface reflectors are mounted on a common reference curve, and the reflectors and the receiver are obliquely mounted on the azimuth tracking equipment. And a second tracking device is arranged between the azimuth tracking device receiver and the azimuth tracking device receiver, so that the receiver is rotated to track the change of the solar altitude.

Description

Technical Field

[0001] This utility model relates to the field of trough solar collector technology, specifically a novel cylindrical reflector splicing trough solar collector system. Background Technology

[0002] Concentrated solar collectors use concentrating technology to focus a large amount of low-density solar energy onto a small area, forming high-density solar energy. This generates high-temperature heat energy for solar thermal power generation. It can also store heat for continuous power generation, making it the most promising thermal power generation technology to replace coal-fired power plants. Currently, the main concentrated solar collector technologies include tower, trough, linear Fresnel, and dish concentrators. Among these, the trough solar collector, using a linear focusing parabolic concentrator, is the most mature technology, commercialized over 30 years ago, and boasts stable performance. However, its concentration ratio is less than 30, its operating temperature is low, and its performance is difficult to improve. One of the main reasons for this is the high manufacturing cost and large optical errors associated with using a linear focusing parabolic concentrator, resulting in a low concentration ratio.

[0003] Patent CN200520134069.X proposes using a slotted arc-shaped reflector instead of a parabolic reflector. This simplifies the manufacturing process and significantly reduces the cost of reflector manufacturing, but it also significantly reduces performance. The main reason is that cylindrical reflectors have significant aberrations. With the same slot width, the width-to-focal-length ratio of a cylindrical reflector must be much smaller than that of a parabolic reflector to eliminate aberrations. With the same slot system width, the focal length of a cylindrical reflector must be much larger than that of a parabolic slot system. Since the receiver radius is proportional to the focal length, it will be much larger than that of a parabolic slot system, thus reducing the light concentration ratio and operating temperature, resulting in performance far lower than that of a conventional parabolic slot system.

[0004] The proposed solution in patent CN200920231849.4 includes using multiple arc-shaped reflectors to replace the parabolic reflector, but it does not provide a method for splicing the multiple arc-shaped reflectors to simulate the parabolic reflector. For example, in embodiments 1 and 2, two arc-shaped reflectors are used to replace the parabolic reflector, but there are still significant aberrations. The improved version, including embodiment 3, although it uses multiple arc surfaces spliced ​​together, does not describe how to determine the position, surface direction, and radius of each arc-shaped reflector. In the given implementation diagram, the arc-shaped reflectors are staggered and deviate significantly from the parabolic surface, making it difficult to guarantee performance.

[0005] CN201110462998.3 proposes using plane mirrors to construct a trough-type parabolic reflector. Since the plane mirror will inevitably produce a parallel light spot with the same width as the plane mirror on the focal plane, the light concentration ratio of the system will be greatly reduced, and its performance will be far lower than that of the parabolic trough system.

[0006] The proposed solution in patent CN200920231849.4 suggests using a composite parabolic surface for secondary focusing to improve performance and light concentration ratio. However, the composite parabolic surface used in this system reflects light multiple times, requiring very high processing precision. Otherwise, the error of the reflected light will increase linearly with the number of reflections, thereby reducing system performance and making the solution very uneconomical.

[0007] Patent CN202320187846.5 proposes using multiple cylindrical mirrors spliced ​​together to form a line-focusing reflector. The center of each cylindrical mirror lies on a parabolic surface, and its normal direction coincides with the normal on the corresponding parabolic surface. The center of each spliced ​​cylindrical surface lies on the axis of symmetry of the solar concentrator system, thus determining the radius of curvature of the spliced ​​cylindrical surface. However, this scheme is limited by the parabolic surface splicing. We found that the centers of the spliced ​​reflectors can form arbitrary curves, without being limited by the parabolic surface, thus improving efficiency. Furthermore, based on this, we proposed a new line-focusing system using spliced ​​cylindrical surfaces, which significantly improves efficiency. Utility Model Content

[0008] The purpose of this invention is to provide a novel cylindrical reflector splicing trough-type solar thermal collector system, overcoming the shortcomings of existing technologies and offering a new type of cylindrical reflector splicing trough-type solar thermal collector system with higher optical efficiency, reduced processing difficulty, and lower cost. This invention is an improvement upon patent CN202320187846.5. The invention's first point is the use of multiple cylindrical reflectors spliced ​​together, with the curve formed by the centers of each reflector being any curve other than the parabola described in the previous patent; it also specifies the requirements for the center position and radius of curvature of each spliced ​​reflector. The second point is that the preferred scheme requires the centers of the spliced ​​reflectors to be on a reference circle, the diameter of which is equal to the system's focal length; and it is tilted and mounted on an azimuth tracking device, improving the cosine factor and efficiency in high-latitude regions, making the system performance approach that of Earth axis tracking. The third point is the introduction of a compact splicing structure, with the splicing surfaces forming a continuous surface, eliminating the hazards of wind vibration caused by gaps between the splicing surfaces and stabilizing system performance. The fourth point is the introduction of a design method for the above system, replacing the current method that requires complex research to provide optimized design parameters.

[0009] To achieve the above objectives, this utility model provides the following technical solution:

[0010] A novel cylindrical reflector splicing trough-type solar thermal collector system is characterized by comprising a reflector assembly and a receiver. The reflector assembly is composed of multiple strip-shaped cylindrical reflectors spliced ​​together, with adjacent cylindrical reflectors connected end-to-end and closely arranged. The entire spliced ​​reflective surface is a continuous surface. The strip-shaped cylindrical reflectors share a common focal point. The receiver is installed at the common focal point of the strip-shaped cylindrical reflectors. The receiver is a strip-shaped cavity receiver or a flat plate receiver. The centers of the strip-shaped cylindrical reflectors are all mounted on a common reference curve. Both the reflectors and the receiver are tilted and mounted on an azimuth tracking device. A second tracking device is installed between the receiver and the azimuth tracking device, thereby rotating the receiver to track changes in the solar altitude angle.

[0011] The reference curve can be a straight line, a circle, an ellipse, a hyperbola, or other curves, and the radius of curvature r of the strip-shaped cylindrical reflector is determined by the following formula:

[0012]

[0013] in, The edge corner of the center, Its distance from the focal point;

[0014] When the reference curve is a circle, its radius of curvature is equal to half the focal length of the heat collection system.

[0015] When the reference surface is a parabola, a cylindrical surface with a radius equal to the focal length, or a compact structure, the initial design value of the edge angle of the solar thermal collector system is set. The The value range is 30-50 degrees, preferably 45 degrees; based on the light transmission radius and edge corner Calculate the focal length of the parabolic trough The formula for its calculation is:

[0016]

[0017] in, W is the focal length of the parabolic trough, and W is the half-width of light transmission for the novel trough-type solar thermal collector system. Design initial values ​​for the edge corners;

[0018] When the reference plane is a sphere with a diameter equal to the system focal length, the initial focal length is chosen to be equal to the system's light transmission diameter.

[0019] The half-width w of the cylindrical reflector is determined by the following formula:

[0020] in, Let σ be the focal length of the parabolic trough, and σ be the variance of the Gaussian distribution of the reflected light intensity. Design initial values ​​for the edge corners;

[0021] The formula for approximating the value of σ is:

[0022]

[0023] in, The variance of the Gaussian distribution of the solar photosphere. It is the variance of the reflector slope error distribution; It is the Gaussian distribution variance of the tracking error; It is the Gaussian distribution variance of the system installation error; It is the variance of the Gaussian distribution of the error in the reflector material.

[0024] The initial value of the receiver half-width R is calculated using the following formula:

[0025]

[0026] Where W is the half-groove width of the trough solar collector system. σ is the edge angle of the parabolic trough solar collector system, σ is the variance of the Gaussian distribution of reflected light intensity, and λ is the average incident angle of sunlight in the parabolic trough solar collector system.

[0027] The position and radius of curvature of the cylindrical reflector are calculated starting from the first reflector with the smallest edge angle, specifically as follows:

[0028] When using a compact structure, the center coordinates are The edge angle is Satisfying the equation:

[0029]

[0030] in, For receiver radius, For the focal length of the parabolic trough, The starting position edge angle. This is the maximum radial width of the spherical mirror;

[0031] The edge angles are obtained by solving. This allows us to obtain the center coordinates; then, we calculate the radius of curvature of the reflecting mirror. :

[0032]

[0033] in, Let be the radius of curvature of the mirror. For the focal length of the parabolic trough, The starting position edge angle;

[0034] Then calculate the position of the other end of the first reflector. Then calculate the center position of the second mirror in sequence. It satisfies the system of equations:

[0035]

[0036]

[0037]

[0038] in, For receiver radius, This is the angle of the edge of the second mirror. For the focal length of the parabolic trough, This is the maximum radial width of the spherical mirror;

[0039] Solving the system of equations yields the center coordinates and edge angles of the second mirror, as well as the radius of curvature. Repeat the above steps to calculate the center coordinates, edge angles, and radii of curvature of each mirror in turn.

[0040] When the centers of each mirror lie on a known reference plane, the radius of that reference plane is... Then the first reflecting mirror satisfies the system of equations:

[0041]

[0042]

[0043]

[0044] in, This is the angle of the edge of the second mirror. For the focal length of the parabolic trough, The maximum radial width of the spherical mirror. The radius of the reference surface;

[0045] Solving the system of equations yields the coordinates of the center of the first mirror, its edge angle, and its radius of curvature.

[0046] Repeat the above steps to calculate the center coordinates, edge angles, and radius of curvature of each mirror in turn.

[0047] When the receiver uses a strip cavity receiver, a cylindrical transparent glass cover is installed at the opening of the strip cavity receiver, and the concave side is placed inside the cavity receiver; or a receiver consisting of a transparent outer tube and a metal tube with a selective absorption coating on the surface is used, with V-shaped fins connected to the metal tube.

[0048] The system also includes a V-groove concentrator, the inlet of which is installed on the focal plane of the trough solar collector system, and the receiver is installed at the outlet of the V-groove concentrator. The V-groove concentrator consists of two inclined plane mirrors, with the reflecting surface forming an angle θ of 2-10 degrees with the vertical direction. The inlet half-width of the V-groove concentrator is equal to the radius or half-width R of the receiver tube of the trough solar collector system, and the outlet width of the V-groove concentrator... Then, with the addition of a V-groove reflecting condenser, the receiver tube radius or half-width... If they are equal, calculate using the following formula:

[0049]

[0050] in, For the receiver tube radius or half-width of a trough solar thermal collector system, The angle between the reflecting surface and the vertical direction. It is the edge corner of a trough solar thermal collector system.

[0051] Compared with the prior art, the beneficial effects of this utility model are:

[0052] This invention utilizes cylindrical reflectors to construct a line-focusing trough-type concentrating solar thermal system, overcoming the limitation that the reflective surface is parabolic. It proposes a compact splicing structure, creating a continuous reflective surface and eliminating gaps between the splicing surfaces, thereby eliminating the hazards caused by wind vibration and stabilizing system performance. The trough system operates in a natural environment and is affected by wind. If there are small gaps between the splicing surfaces, vibrations will occur under wind, increasing optical errors and affecting system performance. Another design proposed in this invention uses cylindrical surface splicing, with the centers of all cylindrical surfaces on a circle whose diameter equals the system's focal length. This is then mounted on an azimuth tracking device, with another tracking device installed between the receiver and the azimuth tracking device to track changes in the solar declination angle. This design is more efficient than traditional parabolic trough systems with single-axis tracking, especially in high-latitude regions, primarily due to a larger cosine factor. The receiver's small size and light weight reduce the requirements for the tracking device, significantly lowering costs. This design is easily scalable, further reducing costs, making it a high-efficiency, low-cost solution. The gap between adjacent cylindrical mirrors in this design is much larger than in a parabolic splicing system, minimizing wind vibration impact, which can be eliminated by increasing support strength. However, this trough collector, when installed on a horizontal north-south or east-west tracking axis, performs significantly worse than a compact splicing surface system and therefore cannot replace it. Its performance is better when installed on an azimuth tracking device, making it particularly suitable for locations with latitudes greater than 30 degrees.

[0053] The solar collector can also be installed on a ground axis tracking device to periodically adjust the tracking axis; at the same time, another tracking device can be installed between the ground axis and the receiver to drive the receiver to change direction and track the changes in the solar declination angle, which can achieve a dual-axis tracking effect with an efficiency close to that of a dual-axis tracking system, thereby greatly improving the system efficiency. It is an ultra-high efficiency and low-cost solution. Attached Figure Description

[0054] Figure 1 This utility model presents a schematic diagram of the structural principle of a novel cylindrical reflector splicing groove solar collector system with a fixed cylindrical reflector splicing line and a focusing groove system.

[0055] Figure 2 This invention relates to three types of cavity receivers used in a novel cylindrical reflector splicing groove solar thermal collector system.

[0056] Figure 3 This utility model discloses a novel cylindrical reflector splicing groove solar thermal collector system with a cavity receiver and a V-groove concentrator, featuring a fixed cylindrical reflector splicing line focusing groove system structure diagram;

[0057] Figure 4 This utility model discloses a novel cylindrical reflector splicing groove solar thermal system with a V-groove reflective concentrator, which is a structural diagram of a tightly spliced ​​cylindrical reflector splicing groove system.

[0058] Figure 5 This invention provides a novel cylindrical reflector splicing groove solar collector system, which presents a novel cylindrical splicing line focusing scheme compared with the traditional parabolic scheme.

[0059] In the diagram: 1. Reflector, 11. Insulation layer, 12. Vacuum collector tube, 13. Receiver cover, 14. Absorber tube, 15. Absorber plate, 16. Glass, 17. Air or vacuum, 3. Receiver, 4. Transparent glass cover, 5. V-groove reflector. Detailed Implementation

[0060] The technical solutions of the present invention will now be described in detail with reference to the accompanying drawings of the embodiments.

[0061] like Figure 1-5As shown, a novel cylindrical reflector splicing trough-type solar thermal collection system is characterized by comprising a reflector group and a receiver. The reflector group is composed of multiple strip-shaped cylindrical reflectors spliced ​​together. Adjacent cylindrical reflectors are connected end-to-end and closely arranged, with the entire spliced ​​reflective surface being a continuous surface. The strip-shaped cylindrical reflectors share a common focal point. The receiver is installed at the common focal point of the strip-shaped cylindrical reflectors. The receiver is a strip-shaped cavity receiver or a flat plate receiver. The centers of the strip-shaped cylindrical reflectors are all installed on a common reference curve. Both the reflectors and the receiver are tilted and installed on an azimuth tracking device. A second tracking device is installed between the receiver and the azimuth tracking device, thereby rotating the receiver to track changes in the solar altitude angle.

[0062] The reference curve can be a straight line, a circle, an ellipse, a hyperbola, or other curves, and the radius of curvature r of the strip-shaped cylindrical reflector is determined by the following formula:

[0063]

[0064] in, The edge corner of the center, Its distance from the focal point;

[0065] When the reference curve is a circle, its radius of curvature is equal to half the focal length of the heat collection system.

[0066] When the reference surface is a parabola, a cylindrical surface with a radius equal to the focal length, or a compact structure, the initial design value of the edge angle of the solar thermal collector system is set. The The value range is 30-50 degrees, preferably 45 degrees; based on the light transmission radius and edge corner Calculate the focal length of the parabolic trough The formula for its calculation is:

[0067]

[0068] in, W is the focal length of the parabolic trough, and W is the half-width of light transmission for the novel trough-type solar thermal collector system. Design initial values ​​for the edge corners;

[0069] When the reference plane is a sphere with a diameter equal to the system focal length, the initial focal length is chosen to be equal to the system's light transmission diameter.

[0070] The half-width w of the cylindrical reflector is determined by the following formula:

[0071] in, Let σ be the focal length of the parabolic trough, and σ be the variance of the Gaussian distribution of the reflected light intensity. Design initial values ​​for the edge corners;

[0072] The formula for approximating the value of σ is:

[0073]

[0074] in, The variance of the Gaussian distribution of the solar photosphere. It is the variance of the reflector slope error distribution; It is the Gaussian distribution variance of the tracking error; It is the Gaussian distribution variance of the system installation error; It is the variance of the Gaussian distribution of the error in the reflector material.

[0075] The initial value of the receiver half-width R is calculated using the following formula:

[0076]

[0077] Where W is the half-groove width of the trough solar collector system. σ is the edge angle of the parabolic trough solar collector system, σ is the variance of the Gaussian distribution of reflected light intensity, and λ is the average incident angle of sunlight in the parabolic trough solar collector system.

[0078] The position and radius of curvature of the cylindrical reflector are calculated starting from the first reflector with the smallest edge angle, specifically as follows:

[0079] When using a compact structure, the center coordinates are The edge angle is Satisfying the equation:

[0080]

[0081] in, For receiver radius, For the focal length of the parabolic trough, The starting position edge angle. This is the maximum radial width of the spherical mirror;

[0082] The edge angles are obtained by solving. This allows us to obtain the center coordinates; then, we calculate the radius of curvature of the reflecting mirror. :

[0083]

[0084] in, Let be the radius of curvature of the mirror. For the focal length of the parabolic trough, The starting position edge angle;

[0085] Then calculate the position of the other end of the first reflector. Then calculate the center position of the second mirror in sequence. It satisfies the system of equations:

[0086]

[0087]

[0088]

[0089] in, For receiver radius, This is the angle of the edge of the second mirror. For the focal length of the parabolic trough, This is the maximum radial width of the spherical mirror;

[0090] Solving the system of equations yields the center coordinates and edge angles of the second mirror, as well as the radius of curvature. Repeat the above steps to calculate the center coordinates, edge angles, and radii of curvature of each mirror in turn.

[0091] When the centers of each mirror lie on a known reference plane, the radius of that reference plane is... Then the first reflecting mirror satisfies the system of equations:

[0092]

[0093]

[0094]

[0095] in, This is the angle of the edge of the second mirror. For the focal length of the parabolic trough, The maximum radial width of the spherical mirror. The radius of the reference surface;

[0096] Solving the system of equations yields the coordinates of the center of the first mirror, its edge angle, and its radius of curvature.

[0097] Repeat the above steps to calculate the center coordinates, edge angles, and radius of curvature of each mirror in turn.

[0098] When the receiver uses a strip cavity receiver, a cylindrical transparent glass cover is installed at the opening of the strip cavity receiver, and the concave side is placed inside the cavity receiver; or a receiver consisting of a transparent outer tube and a metal tube with a selective absorption coating on the surface is used, with V-shaped fins connected to the metal tube.

[0099] The system also includes a V-groove concentrator, the inlet of which is installed on the focal plane of the trough solar collector system, and the receiver is installed at the outlet of the V-groove concentrator. The V-groove concentrator consists of two inclined plane mirrors, with the reflecting surface forming an angle θ of 2-10 degrees with the vertical direction. The inlet half-width of the V-groove concentrator is equal to the radius or half-width R of the receiver tube of the trough solar collector system, and the outlet width of the V-groove concentrator... Then, with the addition of a V-groove reflecting condenser, the receiver tube radius or half-width... If they are equal, calculate using the following formula:

[0100]

[0101] in, For the receiver tube radius or half-width of a trough solar thermal collector system, The angle between the reflecting surface and the vertical direction. It is the edge corner of a trough solar thermal collector system.

[0102] Example 1: As Figure 1 and 2 As shown in the figure, M0 and Mi are two cylindrical reflectors installed in the system; one other cylindrical reflector is omitted. The receiver is mounted on a tracking device that can rotate around the center of a reference circle to track changes in the solar altitude angle. When the incident ray is S, the receiver rotates from position A (at perpendicular incidence) around the center O to A', and both reflectors M0 and Mi reflect the ray to receiver A'. We established a ray tracing program to simulate and calculate the system performance and design optimization program; the optimization results are shown below. Figure 5 ;

[0103] If the system is installed at 40 degrees North latitude, with a 12-meter-wide trough, a cavity-embedded vacuum collector tube is used as the receiver. A line-focusing trough reflector is constructed by splicing together strip-shaped cylindrical reflectors, each with a half-width of 0.6 meters after tilting. The centers of all strip-shaped reflectors lie on the curve of a circle with a diameter equal to the focal length. The angle between the center normal vector of each strip-shaped reflector and the principal axis OA is equal to one-quarter of the central angle θi, thus determining the installation direction of each strip-shaped cylindrical reflector. The system is tilted and mounted on an azimuth tracking device to track changes in the sun's azimuth. The goal is to maximize the annual average solar thermal efficiency. Other optimization conditions include a receiver heat loss of 2.8511 kW / m² per unit area, a parabolic slope error of 3 mrad, a cylindrical slope error of 1 mrad, and material and other errors of 1 mrad. The second scheme is an improvement on the first scheme, adding a V-groove concentrator to its receiver.

[0104] Except for the fixed reflector which uses azimuth tracking, all others use north-south horizontal axis tracking; the spliced ​​parabolic surface means that the centers of all spliced ​​cylindrical surfaces lie on the parabola; the reference circle splicing means that the centers of all spliced ​​cylindrical surfaces lie on a circle with a radius equal to the focal length; the fixed reflector means that the centers of all spliced ​​cylindrical surfaces lie on a circle with a radius directly equal to the focal length. Close splicing means that all spliced ​​cylindrical reflectors are tightly connected to each other, forming a continuous curved surface.

[0105] In the table, ρτα represents the specular reflectivity. Glass cover transmittance The receiver tube absorptivity α = 0.96, plus a 5% contamination loss (vacuum collector tube); these are the physical property parameters for a traditional parabolic system using a vacuum collector tube. If it's a cavity receiver, even if all receivers use cavity-embedded vacuum collector tubes... Figure 2 The first receiver in the cavity has an absorption rate of 98% for the light entering the cavity. Transmittance is not a concern because the light that doesn't pass through the glass cover is repeatedly intercepted and absorbed inside the cavity. In other words... Heat loss is calculated based on vacuum collector tubes. If using... Figure 2 The second receiver, which welds fins onto the inner tube of a conventional vacuum collector tube to form a V-shaped receiving surface, only improves the absorptivity while the transmittance remains at 0.96. The third receiver, by changing the outer casing to a concave shape, can further improve the transmittance to 0.98, thereby improving system performance. This technical solution is based on the first receiver.

[0106] The end-point / blocking calculation in the table is the product of blocking and shading effects and atmospheric absorption factor for fixed reflectors; for others, it is the end-point factor.

[0107] The second option in the table is the fixed reflector marked with #, which adds a V-groove condenser to the receiver. The condenser uses a small number of reflectors, so high-quality reflectors should be used, and the reflectivity should be set to 0.98.

[0108] The receiver uses Figure 1 The cavity receiver shown consists of multiple vacuum heat collection tubes embedded inside the cavity, forming the receiving surface. The optimized focal ratio is 1.514; the geometric concentration ratio is 30.3; the performance of the optimized design scheme based on simulation calculations is shown in Table 1.

[0109] The performance of the first fixed reflector system includes a cosine factor of 0.964, an interception rate of 0.974, a blocking, shading, and atmospheric absorption factor of 0.983, an optical efficiency of 0.800, and a photothermal efficiency of 0.640. In comparison, the photothermal efficiency of the optimized design of the traditional parabolic surface (the third scheme in the table) is 0.454; and the photothermal efficiency of the spliced ​​parabolic surface (the fourth and fifth schemes) is 0.593; both are significantly lower than the scheme proposed in this invention. The reference spherical splicing system uses a cylindrical reference surface with a radius equal to the focal length, and is installed on the north-south horizontal axis tracking system. The last three optimized schemes in the table are the results when the working location is at a latitude of 30 degrees. For comparison, if the system is installed at 30 degrees north latitude, the optimized photothermal efficiency is 64.3%, slightly better than at 40 degrees north latitude. This is because at 30 degrees latitude, there is more solar energy available during the working time, resulting in relatively less heat loss. Its performance is superior to that of traditional parabolic surfaces, which have larger optical errors, but inferior to parabolic trough systems using cylindrical mirrors. However, our simulations show that the fixed-mirror system is more efficient in winter than in summer, thus better suited to the higher energy consumption demands of winter.

[0110] Adding a V-groove concentrator to the receiver optimizes the performance of the proposed solution, as shown in the second result in the table. Figure 4 The performance can be further improved. Even with the 2% reflection loss due to the secondary focusing, the annual average photothermal efficiency increases to 65.4%, which is 6.1% higher than the north-south horizontal axis focusing system.

[0111] Example 2, as Figure 2 As shown, the trough is 8 meters wide, using a strip-shaped cavity as the receiver. The cavity contains a vacuum heat collection tube, and a tightly assembled trough-type reflector is constructed using 0.4-meter-wide strip-shaped cylindrical reflectors. Each reflector reflects sunlight from the center to the focal point. The radius of curvature of each cylindrical reflector is calculated according to the formula described. The system is installed at a latitude of 40 degrees on a north-south horizontal tracking axis. Other conditions are the same as in Example 1. The optimized focal ratio is 0.456; the geometric focusing ratio is 54.4; simulation calculations show the following performance optimizations: cosine factor is 0.852, interception rate is 0.977, terminal and atmospheric absorption factor is 0.972, optical efficiency is 0.700, and photothermal efficiency is 0.593. This is significantly lower than the photothermal efficiency of the traditional parabolic optimized design (0.454). The photothermal efficiency of the spliced ​​parabolic surface is 0.593, which is the same for both. However, the focal ratio of the tightly spliced ​​surface is slightly smaller. In addition, the seamless splicing surface is more compact, which eliminates the wind vibration problem caused by the small gaps between the splicing surfaces and the resulting optical errors, thereby stabilizing the system performance.

Claims

1. A novel cylindrical reflector splicing trough type solar thermal collection system, characterized in that, The system includes a reflector assembly and a receiver. The reflector assembly is composed of multiple strip-shaped cylindrical reflectors joined together, with adjacent cylindrical reflectors connected end-to-end and closely arranged. The entire spliced ​​reflective surface is a continuous surface. The strip-shaped cylindrical reflectors share a common focal point. The receiver is mounted on the common focal point of the strip-shaped cylindrical reflectors. The receiver is either a strip-shaped cavity receiver or a flat plate receiver. The centers of the strip-shaped cylindrical reflectors are all mounted on a common reference curve. Both the reflectors and the receiver are mounted at an angle on an azimuth tracking device. A second tracking device is installed between the receiver and the azimuth tracking device, thereby rotating the receiver to track changes in the solar altitude angle.

2. The novel cylindrical reflector splicing groove solar thermal collection system according to claim 1, characterized in that, The reference curve can be a straight line, a circle, an ellipse, or a hyperbola, and the radius of curvature r of the strip-shaped cylindrical reflector is determined by the following formula: ， in, The edge corner of the center, Its distance from the focal point; When the reference curve is a circle, its radius of curvature is equal to half the focal length of the heat collection system.

3. The novel cylindrical reflector splicing groove solar thermal collection system according to claim 1, characterized in that, When the reference surface is a parabola, a cylindrical surface with a radius equal to the focal length, or a compact structure, set the initial design value for the edge angle of the solar thermal collector system. The The value range is 30-50 degrees; based on the light transmission radius. and edge corner Calculate the focal length of the parabolic trough The formula for its calculation is: ， in, W is the focal length of the parabolic trough, and W is the half-width of light transmission for the novel trough-type solar thermal collector system. Design initial values ​​for the edge corners; When the reference plane is a sphere with a diameter equal to the system focal length, the initial focal length is chosen to be equal to the system's light transmission diameter.

4. The novel cylindrical reflector splicing groove solar thermal collection system according to claim 1, characterized in that, The half-width w of the cylindrical reflector is determined by the following formula: , in, Let σ be the focal length of the parabolic trough, and σ be the variance of the Gaussian distribution of the reflected light intensity. Design initial values ​​for the edge corners; The formula for approximating the value of σ is: ， in, The variance of the Gaussian distribution of the solar photosphere. It is the variance of the reflector slope error distribution; It is the Gaussian distribution variance of the tracking error; It is the Gaussian distribution variance of the system installation error; It is the variance of the Gaussian distribution of the error in the reflector material.

5. A novel cylindrical reflector splicing groove solar thermal collection system according to claim 1, characterized in that, The initial value of the receiver half-width R is calculated using the following formula: ， Where W is the half-groove width of the trough solar collector system. σ is the edge angle of the parabolic trough solar collector system, σ is the variance of the Gaussian distribution of reflected light intensity, and λ is the average incident angle of sunlight in the parabolic trough solar collector system.

6. A novel cylindrical reflector splicing trough type solar thermal collector system according to claim 1, characterized in that, When the receiver uses a strip cavity receiver, a cylindrical transparent glass cover is installed at the opening of the strip cavity receiver, and the concave side is placed inside the cavity receiver; or a receiver consisting of a transparent outer tube and a metal tube with a selective absorption coating on the surface is used, with V-shaped fins connected to the metal tube.

7. A novel cylindrical reflector splicing trough type solar thermal collector system according to claim 1, characterized in that, The system also includes a V-groove concentrator, the inlet of which is installed on the focal plane of the trough solar collector system, and the receiver is installed at the outlet of the V-groove concentrator. The V-groove concentrator consists of two inclined plane mirrors, with the reflecting surface forming an angle θ of 2-10 degrees with the vertical direction. The inlet half-width of the V-groove concentrator is equal to the radius or half-width R of the receiver tube of the trough solar collector system, and the outlet width of the V-groove concentrator... Then, with the addition of a V-groove reflecting condenser, the receiver tube radius or half-width... If they are equal, calculate using the following formula: ， in, For the receiver tube radius or half-width of a trough solar thermal collector system, The angle between the reflecting surface and the vertical direction. It is the edge corner of a trough solar thermal collector system.

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