A method for setting focal length partitions of a lens field

Abstract

This invention relates to the field of solar tower thermal technology and discloses a method for zoning the focal length of a mirror field. This method divides the field into different annular zones based on the distance between the heliostats and the thermal absorption tower. The heliostats in each zone use the same focal length. This method addresses the problems of low setup efficiency and slow production progress in existing technologies.

Description

Technical Field

[0001] The present invention relates to the field of solar tower photothermal technology, and in particular to a method for setting focal length zoning of a mirror field. Background Art

[0002] Tower solar thermal power generation technology utilizes a large number of independently tracked heliostats to reflect solar radiation onto a heat sink mounted atop a tall tower. This heats the working fluid within the sink, generating electricity from the heat energy of the high-temperature medium. This technology offers the advantages of a high concentration ratio and high operating temperature. The quality of the solar spot reflected by the heliostats significantly influences the efficiency of the heat sink in converting solar energy into heat.

[0003] To achieve a smaller, more ideally shaped light spot reflected by a heliostat, an ideal focal length is typically set for each heliostat based on its distance from the receiver. This focal length is then maintained during the heliostat production process. Therefore, for a full mirror field, especially a concentric arc field, the focal length must be set for each ring of heliostats. For a wheat field field, a different focal length must be considered for each heliostat. This focal length setting method requires constant adjustment of the production tooling used to set the heliostat curvature (the focal length setting is also the curvature setting, with the curvature value being twice the focal length) during production. This process consumes considerable time during the heliostat production process, increasing production costs while also reducing production schedules and efficiency. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a method for setting the focal length of a mirror field by partitioning, which solves the problems of low setting efficiency and slow production progress in the existing technology.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] A method for setting focal length zones of a mirror field is provided. The method divides the mirror field into different annular zones according to the distance between the heliostats and the heat absorbing tower. The heliostats in each zone use the same focal length.

[0007] As a preferred technical solution, dividing the mirror field into different annular areas includes the following steps:

[0008] S1, calculate the spot size at the ideal focal length of each heliostat in the mirror field and form a spot size curve;

[0009] S2, setting a minimum spot size limit and a maximum spot size limit for each area; wherein the minimum spot size limit and the maximum spot size limit are set according to the size curve in step S1;

[0010] S3, before setting a uniform focal length for each area, limiting the difference between the maximum spot and the minimum spot in each area.

[0011] As a preferred technical solution, if the mirror field is arranged in a staggered manner, the following steps are also included:

[0012] S4: Before setting a uniform focal length for each area, the focal length of the entire field of view is divided into zones according to the natural layout of the field of view. At the same time, the difference in the spot size of each zone after the focal length is divided is verified to ensure that the spot size after the uniform focal length is set in the focal length zone does not exceed the limit set in step S3.

[0013] As a preferred technical solution, step S4 includes the following steps:

[0014] S41, respectively calculate the ideal focal length f1 of the heliostat closest to the heat absorption tower in a certain area, the ideal focal length f n , in [f1,f n ] select n focal length values ​​arithmetically within the range; where n>2 and n is an integer;

[0015] S42, respectively calculating the spot size of each heliostat corresponding to the n focal length values ​​in S41;

[0016] S43, at each focal length value, after accumulating the focal lengths of all heliostats in the entire region, select the focal length value f corresponding to the minimum value of the accumulated focal lengths. m It is the optimal focal length for all heliostats in this area.

[0017] As a preferred technical solution, step S4 further includes the following steps:

[0018] S44, using the path optimization method, f m The front and rear focal length values ​​are selected. The selection principle is to reduce the order of magnitude of the selected value until the focal length value is refined to cm. The focal length at this time is the final unified focal length of the field of view partition. Among them, f m The front and rear focal length values ​​refer to [f m -f m-1 , f m +f m+1 ] range of focal length.

[0019] As a preferred technical solution, in step S1, each ring heliostat is selected from heliostats with the same radial orientation centered on the heat absorbing tower in the mirror field.

[0020] As a preferred technical solution, in step S2, the size limit of the minimum light spot and the size limit of the maximum light spot are also set according to the distribution of the absorber target points in the mirror field.

[0021] As a preferred technical solution, in step S1, each ring of the mirror field is on a concentric circle with the center of the heat absorption tower as the center.

[0022] As a preferred technical solution, the mirror field including 74 rings of heliostats is divided into five areas, each of which is divided according to the natural division of the heliostat array.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention significantly reduces the number of focal length adjustments and greatly improves production efficiency, thereby significantly improving production progress;

[0025] (2) While the present invention divides the mirror field into zones and sets the focal length, it does not cause the light spot of the heliostat to become larger than the heat absorber and generate excessive overflow loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a mirror field of a solar thermal power station in an embodiment of the present invention;

[0027] Figure 2 for Figure 1 Schematic diagram of the focal length division of the medium mirror field. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0029] Example 1

[0030] like Figures 1 to 2 As shown, the present invention will solve the low efficiency of the mirror field curvature setting method of the existing heliostat production technology and propose a new idea for the mirror field curvature setting method.

[0031] The present invention addresses the problems of a numerical design method for the focal length of a mirror field during mirror field design and frequent adjustment of the focal length of heliostats in a mirror field during production, which leads to slow production progress. The present invention aims to propose a new method for setting the focal length of a mirror field to address the problem of slow production progress of large quantities of heliostats. Based on the method for setting the focal length of a mirror field, a new method for calculating the focal length of the mirror field is proposed to ensure that the light spot of the heliostats in the mirror field meets the requirements of the heat absorber.

[0032] 1) Method for setting the focal length of the mirror field: Divide the mirror field into different annular areas according to the distance between the heliostat and the heat absorbing tower, and use the same focal length for the heliostats in each area.

[0033] 2) The division method for the area in 1) is as follows:

[0034] ① First, calculate the spot size of each ring of heliostats in the field, generating a spot size curve (including both the longitudinal and lateral dimensions of the spot projected onto the absorber surface). The calculation time should be selected as the design point. Each ring of heliostats should be located in the same radial orientation with respect to the absorber tower within the field. The same applies hereafter. For a field with 10,000 heliostats arranged in a ring, selecting the same radial orientation means selecting all heliostats directly south of the tower (or in other directions).

[0035] ② Input the minimum and maximum spot size limits for each focal length partition (the limits are calculated based on the ideal focal length). The maximum and minimum limits are set according to the size curve in ①, taking into account the distribution method of the absorber target points in the mirror field;

[0036] ③ Before setting a unified focal length for each partition, limit the maximum and minimum spot differences projected onto the heat absorber.

[0037] ④ For staggered lens arrangements, this arrangement naturally forms layout zones. The lens field focal length zones are set according to the layout zones, and the spot size difference value of each zone after the focal length zone is verified. The spot size after setting the same focal length within the focal length zone cannot exceed the limit set in ③.

[0038] ⑤ For the mirror field arranged in the wheat field or other mirror fields without natural layout partitions, only follow the layout methods ①, ②, and ③.

[0039] 3) In the above method, the method for setting the focal length of the heliostat in each partition is as follows:

[0040] ① Calculate the ideal focal lengths f1 and f2 of the heliostat closest to and farthest from the tower respectively. n , in [f1,f n ] range and select n values ​​​​(assuming f1=100, f n =300, select 5 values ​​in arithmetic progression, namely: 100, 150, 200, 250, 300, n=5. );

[0041] ②For each focal length value, calculate the spot size of each heliostat at that value;

[0042] ③ At each focal length value, after accumulating the focal lengths of all heliostats in the entire area, the focal length value f corresponding to the minimum value of the accumulated focal lengths is selected. m (1 <m<n);

[0043] ④Use the path optimization method to find the path of f mThe previous and subsequent values ​​are further refined and selected until the focal length value is refined to the unit of cm. The focal length at this time is the unified focal length of the mirror field area (five data points of 100, 150, 200, 250, and 300 are selected as the calculation data of the spot size, and 200 is finally obtained as the optimal data. Then, the values ​​of 160, 170...200, 210,...240 and so on are calculated. Assuming that 210 is the optimal value, the data of 201, 202...210, 211, 212 and so on are calculated. Regarding the orders of magnitude in the present invention, for example, tens, hundreds, and thousands are different orders of magnitude.).

[0044] The present invention can achieve the following technical effects:

[0045] 1. In a mirror field arranged concentrically with a tower as the center, for example, if there are 74 heliostat rings in the field, if each ring of heliostats needs to have its ideal curvature set on the heliostat curvature setting tooling during production, then the tooling will be set up 74 times. If the curvature setting tooling cannot be fully automated, each adjustment will take one working day. The total adjustment time is 74 working days.

[0046] According to the present invention, the 74 heliostat rings are divided into five zones. Each zone is divided according to the natural layout of the heliostat array, such as the first zone (rings 1-12), the second zone (rings 13-30), the third zone (rings 31-48), the fourth zone (rings 49-66), and the fifth zone (rings 67-74). The focus adjustment table only needs to be adjusted five times.

[0047] 2. While setting the focal length by zoning the mirror field, the heliostat spot size does not grow large enough to extend beyond the receiver, resulting in excessive overflow losses. When the light spot reflected by each ring of heliostats is calculated using the ideal focal length, the spot size gradually increases with the number of rings. However, according to the zoning focal length setting method described in 1), the calculated spot size of each heliostat zone approaches stability as the number of rings increases. That is, the spot size of the first and last heliostats in each zone does not vary much. Therefore, it can be inferred that after zoning the focal length, the spot size of the first and last heliostats in each zone does not differ much, which actually benefits the energy flux distribution on the receiver surface. Zoning the focal length of the mirror field also facilitates the setting of multiple target points on the receiver.

[0048] This invention is a method for increasing the efficiency of heliostat manufacturing by zoning the mirror field and setting curvature. This method for zoning the focal length of the mirror field ensures minimal variation in the amount of heat collected on the absorber surface. The calculation process ensures rapid production while also ensuring numerical accuracy of the focal length.

[0049] The present invention has the following characteristics:

[0050] The focal length of solar tower thermal mirror field is set in different zones, the focal length zoning method of the mirror field is used, and the focal length calculation method used for the focal length zoning of solar tower thermal mirror field is used.

[0051] Example 2

[0052] like Figures 1 to 2 As shown, as a further optimization of Example 1, based on Example 1, this embodiment also includes the following technical features:

[0053] Figure 1 In the 1990s, the mirror field is composed of tens of thousands of heliostats, forming an arc-shaped array. Due to the array pattern of the mirror field, the mirror field spontaneously forms 6 layout partitions, and 6 curvature partitions are set according to the 6 layout partitions. Each partition has Figure 2 (1, 2, 3, 4, 5, and 6 represent the curvature partition numbers respectively).

[0054] Zone 1 (Ring 1-Ring 12): The curvature is set to 531.33 meters;

[0055] Zone 2 (Ring 13-Ring 30): The curvature is set to 737.73 meters;

[0056] Zone 3 (Ring 31-Ring 48): The curvature is set to 1059.29 meters;

[0057] Zone 4 (Ring 49-Ring 66): The curvature is set to 1487.78 meters;

[0058] Zone 5 (Ring 67-Ring 79): The curvature is set to 1943.5 meters;

[0059] Zone 6 (Ring 80-Ring 88): The curvature is set to 2404.3 meters.

[0060] The present invention is further described below:

[0061] ① A tower solar thermal power generation project consists of 88 heliostats. The entire field is divided into five zones based on a staggered arc arrangement. In principle, five curvature zones are created according to the field layout. That is, each zone has an identical heliostat curvature profile for all heliostats.

[0062] ② Taking the first layout zone as an example, the ideal curvatures of the first and last rings of the zone are calculated to be 476.56m and 582.29m respectively.

[0063] ③ Using the calculation interval [476, 582] and a calculation step of 10 meters, calculate the spot size of all heliostats in the first section of the field for each curvature value. Since the heat absorber receiving the spot is typically rectangular, record the horizontal and vertical dimensions of each heliostat's spot separately. Multiply the horizontal dimension by the vertical dimension to obtain the rectangular area that completely encloses the spot. At this curvature, add the cumulative value of the spot size area (rectangular area) of all heliostats as the optimal focal length for all heliostats in that section of the field and record it. The minimum cumulative spot value corresponds to the optimal curvature value in the interval [476, 582]. The calculated curvature is 526 meters.

[0064] ④ Add 10m to or subtract 10m from the optimal curvature value of 526m, forming a calculation interval of [516, 536]. Set the calculation step size to 1m and repeat steps ③ to calculate the sum of the spot area for the entire area. The final optimal curvature is calculated to be 524m.

[0065] ⑤ If a more accurate value is needed, further optimization can be performed on the better value in ④.

[0066] ⑥ Verify the curvature calculated for each zone. The spot size variation obtained for the first zone does not exceed 1m, so it can be adopted. However, when verifying the uniform curvature of zone ⑤, it was found that the spot size variation was larger. Therefore, the fifth zone was further divided into two zones, and the calculations from steps ② to ⑤ were repeated separately.

[0067] In this solution, it usually takes one working day to adjust the focal length of the heliostats on the workbench for setting the focal length. If the ideal focal length is used for each ring of heliostats in the mirror field, the workbench needs to be adjusted at least 88 times. However, the mirror field of this project is unevenly distributed from north to south, and each heliostat actually has a unique ideal focal length. If each heliostat is adjusted according to the ideal focal length, the focus workbench needs to be adjusted tens of thousands of times. By setting the focal length by zone in the mirror field, the production efficiency of the heliostats in the mirror field has been significantly improved.

[0068] At the same time, the truncation efficiency of the mirror field has not decreased significantly.

[0069] As described above, the present invention can be preferably implemented.

[0070] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0071] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Based on the technical essence of the present invention and within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement of the above embodiment shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for setting focal length partitions of a lens field, characterized in that: The mirror field is divided into different annular areas based on the distance between the heliostats and the heat absorbing tower. The heliostats in each area use the same focal length. Dividing the mirror field into different annular areas includes the following steps: S1, calculate the spot size at the ideal focal length of each heliostat in the mirror field and form a spot size curve; S2, setting a minimum spot size limit and a maximum spot size limit for each area; wherein the minimum spot size limit and the maximum spot size limit are set according to the size curve in step S1; S3, before setting a unified focal length for each area, limiting the difference between the maximum spot and the minimum spot in each area; S4, before setting a unified focal length for each area, the focal length of the entire field of view is divided into zones according to the natural layout of the field of view, and the difference in the spot size of each zone after the focal length is divided is verified, so that the spot size after the unified focal length is set in the focal length zone does not exceed the limit set in step S3; Step S4 includes the following steps: S41, respectively calculate the ideal focal length f1 of the heliostat closest to the heat absorption tower in a certain area, the ideal focal length f n , in [f1,f n ] select n focal length values ​​​​arithmetically within the range; where n>2 and n is an integer; S42, respectively calculating the spot size of each heliostat corresponding to the n focal length values ​​in S41; S43, at each focal length value, after accumulating the focal lengths of the heliostats in the above region, select the focal length value f corresponding to the minimum value of the accumulated focal lengths. m As the optimal focal length for all heliostats in the mirror field in this area.

2. The method for setting focal length zones of a mirror field according to claim 1, wherein: Step S4 further includes the following steps: S44, using the path optimization method, f m The front and rear focal length values ​​are selected. The selection principle is to reduce the order of magnitude of the selected value until the focal length value is refined to cm. The focal length at this time is the final unified focal length of the mirror field in this area. m The front and rear focal length values ​​refer to [f m -f m-1 , f m +f m+1 ] range of focal length.

3. The method for setting focal length zones of a mirror field according to claim 2, wherein: In step S1 , each ring heliostat selects a heliostat in the mirror field with the same radial orientation centered on the heat absorbing tower.

4. The method for setting focal length zones of a mirror field according to claim 3, wherein: In step S2, the size limit of the minimum light spot and the size limit of the maximum light spot are also set according to the distribution of the absorber target points in the mirror field.

5. A method for setting focal length zones of a mirror field according to any one of claims 1 to 4, characterized in that: In step S1, each ring of the mirror field is on a concentric circle with the center of the heat absorption tower as the center.

6. A method for setting focal length zones of a mirror field according to claim 5, characterized in that: The mirror field consisting of 74 rings of heliostats is divided into five areas, each of which is divided according to the natural divisions of the heliostat array.

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