A method for designing a circular arc-shaped secondary mirror and a trough-type concentrating solar power system comprising the circular arc-shaped secondary mirror

Abstract

The application provides a kind of circular arc secondary mirror design method and contain circular arc secondary mirror's slot type light-gathering heat collection system, belong to solar light-gathering heat collection technical field. In order to solve the existing secondary reflection slot type light-gathering system's parabolic surface type, composite parabolic surface type and flat plate type curve structure complex, it is easy to cause light-gathering effect to be poor due to processing error;Secondary reflection mirror installation and use will cause the defocusing phenomenon caused by mirror shape error and tracking error to cause the deflection of incidence angle, affect light-gathering effect problem. The application is by installing a kind of circular arc secondary mirror, and the radius, position and width of circular arc secondary mirror are calculated, to ensure that the reflected light through the secondary mirror is maximized to irradiate on the heat collecting tube, to improve the optical efficiency while reducing the processing difficulty.

Description

Technical Field

[0001] This invention relates to the field of solar concentrating and heat collection technology, and more specifically, to a design method for an arc-shaped secondary reflector and a trough-type concentrating and heat collection system containing an arc-shaped secondary reflector. Background Technology

[0002] Solar energy, as the most promising and readily available renewable energy source, has significant development potential. To enhance its energy flux density and utilization value, solar energy is generally concentrated. Energy flux density refers to the amount of energy or power that can be obtained per unit area (e.g., square meters) or produced per unit weight (e.g., kilograms) of energy within a given space. Currently, the main concentrating devices include dish, trough, tower, and linear Fresnel systems. The most mature and widely used technology at present is trough concentrating technology, accounting for over 90% of the solar concentrating market. Therefore, improving the optical efficiency of trough concentrating solar collectors is of great research value.

[0003] Considering that actual trough-type solar concentrators suffer from tracking errors and mirror shape processing errors during operation, incident light rays will be deflected to some extent after the first reflection from the mirror, resulting in a decrease in the optical efficiency of the collector tubes. Therefore, a secondary reflector needs to be added to the traditional system to intercept the deflected light rays as much as possible, ensuring that more of the light falls onto the collector tubes.

[0004] Current secondary reflectors include parabolic, compound parabolic, and flat types. However, considering practical manufacturing issues, parabolic and compound parabolic reflectors, due to their complex curved structures, are prone to errors that can lead to poor light concentration. For example, the invention patent for a trough-type concentrated solar power generation system with a secondary reflector (application number: 201910588554.0) includes a primary reflector, a heat collection tube, and a secondary reflector. The primary reflector has a parabolic surface profile, and the heat collection tube is located at the focal point of the primary reflector. The secondary reflector's surface profile is composed of multiple parabolas with different focal lengths, and the surface profile of the secondary reflector involves... All parabolic foci converge with the primary reflector; due to its linear structure, the focusing effect of the flat plate type is not ideal, such as the invention patent composite curved surface secondary reflection concentrator (application number: CN200910035182.5), which includes a heat collection tube, a planar primary reflector, a folded planar secondary reflector, a composite circular arc primary reflector, a composite parabolic secondary reflector, and a support frame; the heat collection tube consists of two parallel heat collection tubes and is located inside the composite parabolic secondary reflector, and the support frame is located below the composite circular arc primary reflector and is used to fix the composite circular arc primary reflector.

[0005] Therefore, in order to solve the problem of light deflection, a secondary reflector with a simple structure and good focusing effect is needed to improve optical efficiency. Therefore, this paper considers setting up an arc-shaped secondary reflector. Summary of the Invention

[0006] The technical problem to be solved by this invention is:

[0007] To address the problems of existing secondary reflector-type focusing systems with complex parabolic, composite parabolic, and flat curved structures, which are prone to poor focusing effect due to processing errors; and the defocusing phenomenon caused by mirror shape errors and tracking errors during the installation and use of secondary reflectors, which causes incident angle deflection and affects the focusing effect.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0009] This invention provides a design method for an arc-shaped secondary reflector, used to determine the radius, position, and width of the arc-shaped secondary reflector, including the following steps:

[0010] Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the intersection of the mirror surfaces is point O, and the distance from point O to point A is OA.

[0011]

[0012] In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector.

[0013] Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the intersection point O of the parabolic primary mirror surface. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary mirror.

[0014]

[0015]

[0016] Step 3: Based on the positional relationship OO′ between the arc-shaped secondary reflector and the heat collection tube, calculate the relative position OC of the arc-shaped secondary reflector.

[0017] Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector.

[0018]

[0019] In the formula, a is the length of OB, and b1 is the coefficient between OO′ and radius r;

[0020] The position d of the secondary reflector is,

[0021]

[0022] Furthermore, the arc-shaped secondary reflector is an arc-shaped structure with point O′ located on the vertical line of the heat collection tube as the center, radius r, relative position d from the center of the heat collection tube, and width W.

[0023] Furthermore, in step three, the specific calculation steps include:

[0024] Let OC = b*r. Through optical software simulation and fitting, we obtain OC = 0.9226r - 0.0343.

[0025] Approximately OC≈0.9r

[0026] OO′=r-OC≈0.1r, that is, OO′=b1*r

[0027] To simplify the calculation, let OB = a.

[0028] In ΔOBO′, by the Law of Cosines:

[0029]

[0030] Substituting the values:

[0031]

[0032] The solution yields:

[0033]

[0034] Furthermore, when the intersection of the parabolic primary reflector and the center of the heat collection tube do not coincide, including when the parabolic primary reflector is in a vertical or tilted state, the heat collection tube is offset upward or downward along the rod direction to the focal point of the parabolic primary reflector.

[0035] Furthermore, when the parabolic primary reflector is in a vertical position, the heat collection tube is offset vertically upwards from the focal point of the parabolic primary reflector, and the offset amount is... hour,

[0036] Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the intersection of the mirror surfaces is point O, and the distance from point O to point A is OA.

[0037]

[0038] In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector.

[0039] Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the intersection point O of the parabolic primary mirror surface. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary mirror.

[0040]

[0041]

[0042] Step 3: Based on the positional relationship OO′ between the arc-shaped secondary reflector and the heat collection tube, calculate the relative position OC of the arc-shaped secondary reflector.

[0043] Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector.

[0044]

[0045] In the formula, OO1 is the vertical upward offset l1 between the center O1 of the heat collection tube and the focal point of the parabolic primary reflector;

[0046] The position d of the secondary reflector is,

[0047]

[0048] Furthermore, the coefficient b is taken as 0.92 to 0.96.

[0049] Furthermore, when the parabolic primary reflector is in a vertical position, the heat collection tube is offset vertically downwards from the focal point of the parabolic primary reflector, and the offset amount is... hour,

[0050] Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the intersection of the mirror surfaces is point O, and the distance from point O to point A is OA.

[0051]

[0052] In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector.

[0053] Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the intersection point O of the parabolic primary mirror surface. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary mirror.

[0054]

[0055]

[0056] Step 3: Based on the positional relationship OO′ between the arc-shaped secondary reflector and the heat collection tube, calculate the relative position OC of the arc-shaped secondary reflector.

[0057] Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector.

[0058]

[0059] In the formula, OO1 is the vertical downward offset l2 between the center O1 of the heat collection tube and the focal point of the parabolic primary reflector;

[0060] The position d of the secondary reflector is,

[0061]

[0062] Furthermore, the coefficient b is taken as 0.92 to 0.99.

[0063] Furthermore, when the parabolic primary reflector is in an inclined state, the heat collection tube is offset downwards along the rod direction from the focal point of the parabolic primary reflector, and the offset amount is... hour,

[0064] Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the intersection of the mirror surfaces is point O, and the distance from point O to point A is OA.

[0065]

[0066] In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector.

[0067] Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the intersection point O of the parabolic primary mirror surface. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary mirror.

[0068]

[0069]

[0070] Step 3: Decompose the total offset OO2 along the rod direction into horizontal and vertical components, that is, calculate the relative position O2C of the secondary reflector while simultaneously considering both horizontal and vertical offsets.

[0071] OM = OO2cos∠MOO2

[0072] ON = OO2cos∠NOO2

[0073] Where ∠MOO2 is the angle between the rod and the horizontal direction; ∠NOO2 is the angle between the rod and the vertical direction;

[0074] For scenarios where horizontal offset is easy to measure, the following method can be used: Right now

[0075] Where x is the horizontal offset of the heat collection tube; θ1 is the angle between the rod and the horizontal direction;

[0076] Let O2C = b*r

[0077] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is between 0.92 and 0.99.

[0078] OO′=r-OC=r-O2C+OO2

[0079] That is, OO′=b1*r+l2

[0080] In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector.

[0081] Given the horizontal offset, we can deduce l2, and then, by the law of cosines, we have:

[0082]

[0083] Substitution

[0084] have:

[0085]

[0086] The position d of the secondary reflector is,

[0087]

[0088] For scenarios where vertical offset is easy to measure, the following method can be used: Right now Where y is the vertical offset of the heat collection tube; θ2 is the angle between the rod and the vertical direction;

[0089] Let O2C = b*r

[0090] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is between 0.92 and 0.99.

[0091] OO′=r-OC=r-O2C+OO2

[0092] That is, OO′=b1*r+l2

[0093] In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector. Given the vertical offset, l2 can be deduced, and then by the cosine theorem, we have:

[0094]

[0095] Substitution

[0096] have:

[0097]

[0098] The position d of the secondary reflector is,

[0099]

[0100] A trough-type concentrating solar thermal system containing an arc-shaped secondary reflector further includes a parabolic primary reflector and a heat collection tube. The central axis of the heat collection tube coincides with the focal line of the parabolic primary reflector. The cross-sections of both the parabolic primary reflector and the arc-shaped secondary reflector are arc-shaped. The arc-shaped secondary reflector is located above the heat collection tube, and the openings of the parabolic primary reflector and the parabolic secondary reflector are arranged facing each other.

[0101] Compared with the prior art, the beneficial effects of the present invention are:

[0102] This invention discloses a design method for an arc-shaped secondary reflector and a trough-type solar concentrating and heat collection system containing an arc-shaped secondary reflector. The arc-shaped secondary reflector adopts an arc-shaped structure, which is simple and easy to process compared with the curved structures of parabolic, compound parabolic and flat plates. It can effectively avoid the problem of poor light concentration effect caused by processing errors.

[0103] This invention discloses a design method for an arc-shaped secondary reflector and a trough-type concentrating solar collector system containing an arc-shaped secondary reflector. The placement, radius, and width of the arc-shaped secondary reflector are determined using geometric optics principles and optical software simulation to ensure that the reflected light from the secondary reflector illuminates the solar collector tube to the maximum extent, thereby improving optical efficiency.

[0104] This invention provides a design method for an arc-shaped secondary reflector and a trough-type concentrating solar collector system containing the arc-shaped secondary reflector. Considering the case where the collector tube is vertically offset from the focal point of the parabolic primary reflector due to installation errors, the invention provides corrected fitting parameters to improve the accuracy of the design method. Attached Figure Description

[0105] Figure 1 This is a schematic diagram of an arc-shaped secondary reflector system in an embodiment of the present invention;

[0106] Figure 2 This is step one of the design methods for an arc-shaped secondary reflector in an embodiment of the present invention;

[0107] Figure 3 This is step two of the design method for an arc-shaped secondary reflector in an embodiment of the present invention;

[0108] Figure 4 This is step three of the design method for an arc-shaped secondary reflector in an embodiment of the present invention;

[0109] Figure 5 This invention provides a design method for an arc-shaped secondary reflector in a trough-type concentrating solar collector system with a vertically upward-offset collector tube.

[0110] Figure 6This invention provides a design method for an arc-shaped secondary reflector in a trough-type concentrating solar collector system with a vertically downward offset collector tube.

[0111] Figure 7 This is a schematic diagram of the offset direction when the heat collection tube is offset vertically in an embodiment of the present invention. Detailed Implementation

[0112] In the description of this invention, it should be noted that the terms used in the various embodiments, such as "upper," "lower," "front," "rear," "left," and "right," which indicate orientation, are only used to simplify the description of the positional relationships based on the accompanying drawings and do not mean that the components and devices referred to must be operated in accordance with the specific orientations and defined operations, methods, and structures in the specification. Such directional terms do not constitute a limitation of this invention.

[0113] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0114] Specific Implementation Plan 1: Combining Figures 1 to 6 As shown, the present invention provides a trough-type concentrating solar thermal system, including a parabolic primary reflector, a heat collection tube, and an arc-shaped secondary reflector. The central axis of the heat collection tube coincides with the focal line of the parabolic primary reflector. The cross-sections of the parabolic primary reflector and the arc-shaped secondary reflector are both arc-shaped. The arc-shaped secondary reflector is located above the heat collection tube, and the openings of the parabolic primary reflector and the parabolic secondary reflector are arranged facing each other.

[0115] Specific Implementation Plan Two: Combining Figures 1 to 4 As shown, this invention provides a design method for an arc-shaped secondary reflector in a trough-type concentrating solar collector system, used to determine the radius, position, and width of the arc-shaped secondary reflector, wherein the width is the spacing between the ends of the arc-shaped secondary reflector, including the following steps:

[0116] The parabolic equation of the primary reflector is x. 2 =4fy, the radius of the inner tube of the heat collector is r. a The angle between the reflected ray and the normal is called the position angle.

[0117] Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, and the intersection of the mirror surfaces is point O. At this point, the intersection of the parabolic primary mirror surfaces coincides with the center of the heat collection tube. The distance from point O to point A is OA.

[0118] From the equation of the parabola, we have:

[0119]

[0120] In the formula, the height of the parabola is h; α is the tracking error angle; W a is the opening width of the parabolic primary reflector; f is the focal length of the parabolic primary reflector.

[0121] When the edge corner When less than 90°,

[0122]

[0123] At the same time,

[0124]

[0125] In the formula, The edge angle of the parabolic primary reflector is defined as 0°, and the bottom position angle of the heat collection tube is defined as increasing counterclockwise. The maximum position angle is also called the edge angle of the parabolic primary reflector.

[0126] The joint organization includes:

[0127]

[0128] Similarly, when The above formula still holds true if the angle is greater than or equal to 90°.

[0129] RQ is a ray parallel to the principal axis, whose reflected ray OQ passes through the focal point, and whose focal radius is OQ.

[0130]

[0131] At the edge, x0 = W a When the value is 2, OQ reaches its maximum value.

[0132]

[0133] Considering the existence of tracking errors and mirror shape processing errors, which cause light to defocus, the light divergence is most severe, that is, the maximum OA is corresponding to the edge of the parabola, and the maximum value is:

[0134]

[0135]

[0136]

[0137] Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the intersection point O of the parabolic primary mirror surface. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary mirror.

[0138]

[0139]

[0140] Step 3: Based on the positional relationship OO′ between the arc-shaped secondary reflector and the heat collection tube, calculate the relative position OC of the arc-shaped secondary reflector.

[0141] Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector.

[0142] Let OC = b*r. Through simulation and fitting using optical software, we obtain OC = 0.9226r - 0.0343. The optical software could be TracePro.

[0143] Approximately OC≈0.9r

[0144] OO′=r-OC≈0.1r, that is, OO′=b1*r

[0145] To simplify the calculation, let OB = a.

[0146] In ΔOBO′, by the Law of Cosines:

[0147]

[0148] Substituting the values:

[0149]

[0150] Solving for the given information, we get:

[0151]

[0152] In the formula, a is the length of OB; b1 is the coefficient between OO′ and radius r.

[0153] In summary, the radius r of the secondary reflector is...

[0154]

[0155] The width W of the secondary reflector is,

[0156]

[0157] The position d of the secondary reflector is,

[0158]

[0159] In summary, a circular arc-shaped secondary reflector for a trough-type concentrating solar collector is a circular arc structure with point O′ located on the vertical line of the collector tube as the center, radius r, relative position d from the center of the collector tube, and width W.

[0160] The other combinations and connections in this implementation scheme are the same as in Specific Implementation Scheme 1.

[0161] Specific Implementation Plan Three: Combining Figure 5 As shown, when the central axis of the heat collection tube shifts upward along the rod direction at the focal line of the parabolic primary reflector, when the shift amount...

[0162] Unlike the second specific implementation scheme, in step three, the relative position O1C of the arc-shaped secondary reflector is calculated based on the positional relationship O1O′ between the focal points of the arc-shaped secondary reflector and the parabolic primary reflector, and the vertical offset l1 between the center O1 of the heat collection tube and the focal point of the parabolic primary reflector.

[0163] Wherein, O1C is the vertical distance from the top of the secondary reflector to the center O1 of the heat collection tube, that is, the relative position of the secondary reflector.

[0164] Let O1C = b*r

[0165] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is 0.92 to 0.96.

[0166] OO′=r-OC=r-O1C-OO1, that is, OO′=b1*r-l1

[0167] In the formula, OO1 is the upward offset l1 of the center O1 of the heat collection tube and the focal point of the parabolic primary reflector along the rod direction.

[0168] By the Law of Cosines:

[0169]

[0170]

[0171] The other combinations and connections in this implementation scheme are the same as those in specific implementation scheme one or two.

[0172] In summary, the radius r of the secondary reflector is...

[0173]

[0174] The width W of the secondary reflector is,

[0175]

[0176] The position d of the secondary reflector is,

[0177]

[0178] In summary, a circular arc-shaped secondary reflector for a trough-type concentrating solar collector with a vertically upward-offset collector tube is proposed. This is a circular arc structure with point O′ located on the vertical line of the collector tube as the center, radius r, relative position d from the center of the collector tube, and width W.

[0179] Specific Implementation Plan Four: Combining Figure 6 As shown, when the central axis of the heat collection tube is shifted vertically downwards from the focal line of the parabolic primary reflector, when the shift amount...

[0180] Unlike the second specific implementation scheme, in step three, the relative position O2C of the arc-shaped secondary reflector is calculated based on the positional relationship O2O′ between the focal points of the arc-shaped secondary reflector and the parabolic primary reflector, and the vertical offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector.

[0181] Where O2C is the vertical distance from the top of the secondary reflector to the center O2 of the heat collection tube, that is, the relative position of the secondary reflector.

[0182] Let O2C = b*r

[0183] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is 0.92 to 0.99.

[0184] OO′=r-OC=r-O2C+OO2, that is, OO′=b1*r+l2

[0185] In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector.

[0186] By the Law of Cosines:

[0187]

[0188]

[0189] The other combinations and connections in this implementation scheme are the same as those in specific implementation scheme one or two.

[0190] In summary, the radius r of the secondary reflector is...

[0191]

[0192] The width W of the secondary reflector is,

[0193]

[0194] The position d of the secondary reflector is,

[0195]

[0196] In summary, a circular arc-shaped secondary reflector for a trough-type concentrating solar collector with a vertically downward offset collector tube is proposed. This is a circular arc structure with point O′ located on the vertical line of the collector tube as the center, radius r, relative position d from the center of the collector tube, and width W.

[0197] It should be noted that, in combination Figure 7 As shown, in specific embodiments three and four, only the vertical offset of the heat collection tube is considered. This is because:

[0198] 1. Combination Figure 7 a. When the trough collector is in a vertical position, it is common for the collector tubes to deviate in the vertical direction, for example, due to gravity, material expansion, or external mechanical vibration.

[0199] 2. Combining Figure 7 b. When the trough solar collector performs single-axis tracking of the sun, it is in an inclined state. At this time, the offset corresponding to the above calculation method is along the rod direction. It can be decomposed into horizontal and vertical offsets, so that both horizontal and vertical offsets can be considered.

[0200] Taking the downward displacement along the rod direction of a trough solar collector when it is tilted as an example, as shown in the figure:

[0201] Firstly, when the trough-type solar collector is tilted, the collector tubes, constrained by the rod, are prone to slippage along the rod direction if a certain offset occurs. To comprehensively consider both horizontal and vertical offset of the collector tubes, the total offset can be decomposed, such as... Figure 7 As shown,

[0202] OM = OO2cos∠MOO2

[0203] ON = OO2cos∠NOO2

[0204] Where ∠MOO2 is the angle between the rod and the horizontal direction; ∠NOO2 is the angle between the rod and the vertical direction;

[0205] For scenarios where horizontal offset is easy to measure, the following method can be used: Right now

[0206] Where x is the horizontal offset of the heat collection tube; θ1 is the angle between the rod and the horizontal direction.

[0207] Let O2C = b*r

[0208] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is between 0.92 and 0.99.

[0209] OO′=r-OC=r-O2C+OO2

[0210] That is, OO′=b1*r+l2

[0211] In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector.

[0212] Given the horizontal offset, we can deduce l2, and then, by the law of cosines, we have:

[0213]

[0214] Substitution

[0215] have:

[0216]

[0217] In summary, the radius r of the secondary reflector is...

[0218]

[0219] The width W of the secondary reflector is,

[0220]

[0221] The position d of the secondary reflector is,

[0222]

[0223] For scenarios where vertical offset is easy to measure, the following method can be used: Right now

[0224] Where y is the vertical offset of the heat collection tube; θ2 is the angle between the rod and the vertical direction;

[0225] Let O2C = b*r

[0226] In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is between 0.92 and 0.99.

[0227] OO′=r-OC=r-O2C+OO2

[0228] That is, OO′=b1*r+l2

[0229] In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector.

[0230] Given the vertical offset, we can deduce l2, and then, by the law of cosines, we have:

[0231]

[0232] Substitution

[0233] have:

[0234]

[0235] In summary, the radius r of the secondary reflector is...

[0236]

[0237] The width W of the secondary reflector is,

[0238]

[0239] The position d of the secondary reflector is,

[0240]

[0241] Example

[0242] Take the opening width W of the parabolic primary reflector a =5m, focal length f=1.84m, edge angle Heat collector tube radius R a =0.35m, with an allowable tracking error α = 2°. Based on the above design method and principle, a secondary reflector was obtained, modeled in optical software, and the effects of not installing a secondary reflector and installing a secondary reflector were compared.

[0243] The evaluation index is defined as the light reception rate η, which is the ratio of the number of light rays received by the surface of the receiver to the total number of light rays falling on the parabolic primary reflector.

[0244]

[0245] In the formula, m is the luminous flux received by the surface of the heat collection tube, and n is the total luminous flux received by the surface of the parabolic primary reflector.

[0246] (1) Based on the structural parameters of the parabolic primary reflector and the tracking error angle α, determine the distance OA of the tangent circle of the most divergent ray located at the edge corner.

[0247]

[0248] (2) Determine the distance OB between the point where the most divergent ray intersects the edge line on one side and the point where the parabolic primary reflector intersects the surface. The structure on the other side is symmetrical. At the same time, calculate the width BD of the secondary reflector based on OB and the edge angle.

[0249]

[0250]

[0251] (3) Based on the relative position relationship OO′ between the secondary reflector and the heat collection tube, calculate the relative position OC of the secondary reflector, and the radius r of the secondary reflector is given.

[0252]

[0253] The relative position d of the secondary reflector is,

[0254] d = OC ≈ 0.9r = 0.126m

[0255] (4) Compare the light reception rates of the image with and without a secondary reflector using optical software.

[0256] No secondary reflector installed:

[0257] Add a secondary reflector:

[0258] The fact that η2 >> η1 clearly indicates that the optical efficiency of the heat collection tube is significantly improved after the addition of the arc-shaped secondary reflector.

[0259] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A design method for an arc-shaped secondary reflector, characterized in that: The steps for determining the radius, position, and width of a circular arc-shaped secondary reflector include: Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the focal point of the parabolic primary mirror is point O, and the distance from point O to point A is OA. In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector. Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the focal point O of the parabolic primary mirror. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary reflector. ； Step 3: Based on the positional relationship between the arc-shaped secondary reflector and the heat collection tube. Calculate the relative position OC of the arc-shaped secondary reflector. Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector. In the formula, a is the length of OB, and b1 is... The coefficient with radius r; the arc-shaped secondary reflector is located on the perpendicular bisector of the collector tube. The point is the center of the circle; The position d of the secondary reflector is, 。 2. The design method of an arc-shaped secondary reflector according to claim 1, characterized in that: The arc-shaped secondary reflector is located on the vertical line of the heat collection tube. A circular arc structure with point as center, radius r, relative distance d from the center of the heat collection tube, and width W.

3. The design method for an arc-shaped secondary reflector according to claim 2, characterized in that: In step three, the specific calculation steps include: Let OC = b*r. Through optical software simulation and fitting, we obtain OC = 0.9226r - 0.0343. Approximately OC ≈ 0.9r ,Right now To simplify the calculation, let OB = a. exist In the case of cosines, by the law of cosines: Substituting the values: The solution yields: 。 4. The design method of an arc-shaped secondary reflector according to claim 3, characterized in that: When the focal point of the parabolic primary reflector does not coincide with the center of the heat collection tube, including when the parabolic primary reflector is in a vertical or tilted state, the heat collection tube shifts upward or downward along the rod direction from the focal point of the parabolic primary reflector.

5. The design method of an arc-shaped secondary reflector according to claim 4, characterized in that: When the parabolic primary reflector is in a vertical position, the heat collection tube is offset vertically upwards from the focal point of the parabolic primary reflector, and the offset amount is... hour, Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the focal point of the parabolic primary mirror is point O, and the distance from point O to point A is OA. In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector. Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the focal point O of the parabolic primary mirror. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary reflector. ； Step 3: Based on the positional relationship between the arc-shaped secondary reflector and the heat collection tube. Calculate the relative position OC of the arc-shaped secondary reflector. Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector. In the formula, OO1 is the vertical upward offset l1 between the center O1 of the heat collection tube and the focal point of the parabolic primary reflector; The position d of the secondary reflector is, 。 6. The design method of an arc-shaped secondary reflector according to claim 5, characterized in that: The coefficient b is taken as 0.92~0.

96.

7. The design method of an arc-shaped secondary reflector according to claim 4, characterized in that: When the parabolic primary reflector is in a vertical position, the heat collection tube is offset vertically downwards from the focal point of the parabolic primary reflector, and the offset amount is... hour, Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the focal point of the parabolic primary mirror is point O, and the distance from point O to point A is OA. In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector. Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the focal point O of the parabolic primary mirror. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary reflector. ； Step 3: Based on the positional relationship between the arc-shaped secondary reflector and the heat collection tube. Calculate the relative position OC of the arc-shaped secondary reflector. Where OC is the vertical distance from the top of the arc-shaped secondary reflector to the center of the heat collection tube, i.e., the relative position of the arc-shaped secondary reflector; r is the radius of the arc-shaped secondary reflector. In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector; The position d of the secondary reflector is, 。 8. The design method of an arc-shaped secondary reflector according to claim 7, characterized in that: The coefficient b is taken as 0.92~0.

99.

9. The design method of an arc-shaped secondary reflector according to claim 4, characterized in that: When the parabolic primary reflector is tilted, the heat collection tube is offset downwards along the rod direction from the focal point of the parabolic primary reflector, and the offset amount is... hour, Step 1: Based on the structural parameters of the parabolic primary mirror and the tracking error angle α, determine the circle of tangency for the most divergent rays located at one edge corner of the parabolic primary mirror. The point of tangency is point A, the focal point of the parabolic primary mirror is point O, and the distance from point O to point A is OA. In the formula, α is the tracking error angle, and W a The width of the parabolic opening. OQ is the edge angle; OQ is the focal radius of the parabolic primary reflector. Step 2: Determine the distance OB from the intersection point B of the most diverging ray of the parabolic primary mirror and the other edge line to the focal point O of the parabolic primary mirror. Since the cross-section of the circular arc secondary mirror is axisymmetric, based on OB and the edge angle... Calculate the width BD of the secondary reflector. ； Step 3: Decompose the total offset OO2 along the rod direction into horizontal and vertical components, that is, calculate the relative position O2C of the secondary reflector while simultaneously considering both horizontal and vertical offsets. in, The angle between the rod and the horizontal direction; The angle between the rod and the vertical direction; For scenarios where horizontal offset is easy to measure, the following method can be used: ,Right now , Where x is the horizontal offset of the heat collector tube; The angle between the rod and the horizontal direction; Let O2C = b*r In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is 0.92~0.

99. Right now In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector. Given the horizontal offset, we can deduce l2, and then, by the law of cosines, we have: Substitution have: The position d of the secondary reflector is, For scenarios where vertical offset is easy to measure, the following method can be used: ,Right now , Where y is the vertical offset of the heat collector tube; The angle between the rod and the vertical direction; Let O2C = b*r In the formula, b is the coefficient between OC and radius r, and the recommended coefficient b is 0.92~0.

99. Right now In the formula, OO2 is the vertical downward offset l2 between the center O2 of the heat collection tube and the focal point of the parabolic primary reflector. Given the vertical offset, we can deduce l2, and then, by the law of cosines, we have: Substitution have: The position d of the secondary reflector is, 。 10. A trough-type solar concentrating and thermal collecting system comprising the arc-shaped secondary reflector design method according to any one of claims 1-9, characterized in that: It also includes a parabolic primary reflector and a heat collection tube. The central axis of the heat collection tube coincides with the focal line of the parabolic primary reflector. The cross-section of the parabolic primary reflector is parabolic, and the cross-section of the arc-shaped secondary reflector is arc-shaped. The arc-shaped secondary reflector is located above the heat collection tube, and the openings of the parabolic primary reflector and the parabolic secondary reflector are arranged facing each other.

Images