Rapid calculation method for shadow shielding efficiency of tower-type photo-thermal mirror field

Abstract

The invention relates to the field of tower-type solar power generation, and discloses a tower-type photo-thermal mirror field shadow shielding efficiency rapid calculation method, which comprises the following steps: dividing a mirror field into a plurality of square grids according to coordinate data of heliostats, and determining the grid to which each heliostat belongs; for each heliostat, determining a neighbor heliostat of the heliostat; re-dividing the heliostat field into a plurality of square grids, and randomly selecting a heliostat from each grid as a typical heliostat; for each typical heliostat, calculating the shadow shielding proportion generated by the neighbor heliostat, and taking the shadow shielding proportion of the typical heliostat as the shadow shielding proportion of the grid where the typical heliostat is located; and the shadow shielding proportions of all typical heliostats are calculated, so that the shadow shielding efficiency of the whole heliostat field is calculated. According to the method disclosed by the invention, the calculation speed of the shadow shielding efficiency is improved while the calculation precision is ensured, and the balance point of the calculation precision and the calculation speed can be adjusted through different values of the parameters.

Description

Technical Field

[0001] This invention relates to the field of tower solar power generation, and in particular to a rapid calculation method for the shading efficiency of tower solar thermal mirror fields. Background Technology

[0002] Tower-type concentrated solar power (CSP) technology utilizes a large-scale heliostat field to reflect and focus sunlight onto a receiver at the top of a central receiver tower, heating the heat transfer medium to drive a steam turbine for power generation. This represents an important direction for renewable energy utilization. In this system, the optical efficiency of the heliostat field is a key factor determining the overall energy conversion performance, while shading losses (including shadows cast by adjacent heliostats and obstruction of reflected light paths) are one of the main sources of decreased field efficiency, often second only to cosine losses in impact. Accurate calculation of the field's shading efficiency is crucial for optimal field design, real-time performance evaluation, and operational control.

[0003] Currently, the mainstream calculation method is high-precision numerical simulation. These methods (such as Monte Carlo ray tracing-based methods [Hu Yeguang, 2018, Research on Multi-stage Reflective Concentrating Mirror Fields of Tower Solar Thermal Power Generation Systems; Mao Yuanyuan et al., 2025, Optimization Method for Concentric Mirror Field Layout Centered on Solar Collector Towers in Mid-to-Low Latitudes, CN120105666A]) simulate the physical propagation paths of numerous sunlight rays to accurately calculate the area where each heliostat is blocked or causes shading under a specific solar position, thereby calculating efficiency loss. Although theoretically the most accurate, its calculation process involves complex three-dimensional geometric operations, ray intersection judgments, and numerous iterations, consuming enormous computational resources and taking extremely long times. For large commercial mirror fields containing tens or even hundreds of thousands of heliostats, a complete efficiency calculation may take several hours or even days, severely limiting its application in rapid mirror field layout optimization, design scheme comparison, and operation control systems requiring real-time or near-real-time efficiency feedback.

[0004] Given this situation, some methods for simplifying geometric models and empirical formulas have been proposed. For example, the geometric projection method is used to calculate the shading efficiency of heliostats while ignoring the overlapping part of shading [Cheng Xiaolong, 2018, Research on Optimization Design of Tower Power Plant Mirror Field Layout Based on Optical Efficiency]. This method does improve computational efficiency, but the accuracy decreases significantly. Wang Meng et al. [Wang Meng et al., 2024, A Method for Calculating the Optical Efficiency of Mirror Field in Tower Solar Thermal Power Plant, CN117421884A] calculated the shading efficiency by meshing the front heliostat and projecting the mesh points and the vertices of the adjacent heliostats along the direction of incident light or reflected light onto the mirror field plane. This method considers the overlapping part of shading and improves the calculation accuracy. However, with the increasing scale of mirror fields in actual projects (for example, the area of ​​the Ruoqiang 100MW tower solar thermal mirror field has reached 650,000 square meters), this method still has low computational efficiency in scenarios such as rapid layout optimization of mirror fields and comparison of design schemes. On the other hand, if the influence of overlapping shading is not considered, the accuracy is insufficient.

[0005] Therefore, existing technologies present a clear contradiction: high-precision methods struggle to meet the urgent computational speed demands of engineering practice, while fast methods often sacrifice necessary computational accuracy and universality. This contradiction becomes a bottleneck hindering the efficient design and intelligent operation of tower-type photothermal mirror fields. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a rapid calculation method for the shadow occlusion efficiency of a tower-type photothermal mirror field. This method improves the calculation speed of shadow occlusion efficiency while ensuring calculation accuracy, and the balance between calculation accuracy and speed can be adjusted by taking different values ​​of the parameters.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A rapid method for calculating the shading efficiency of a tower-type photothermal mirror field includes the following steps:

[0009] Step 1: Based on the heliostat coordinate data, divide the mirror field into several square grids, determine the grid to which each heliostat belongs, and record which heliostats are in each grid;

[0010] Step 2: Within the grid framework of Step 1, for each heliostat, determine the heliostats in its own grid and adjacent grids that are less than the distance threshold as neighboring heliostats; adjacent grids refer to the three grids above the grid and the grid to the right of the grid in which the heliostat is located.

[0011] Step 3: Select new side lengths and re-divide the mirror field into several square grids. Then, randomly select one heliostat from each grid as a typical heliostat.

[0012] Step 4: For each typical heliostat, calculate the occlusion ratio of its neighboring heliostats, and use the occlusion ratio of the typical heliostat as the occlusion ratio of its grid.

[0013] Step 5: Calculate the shading ratio of all typical heliostats to estimate the shading efficiency of the entire field of view.

[0014] In the above scheme, the method for step 1 is as follows:

[0015] The minimum and maximum x-coordinates of all heliostats within the field of view are denoted as x0 and x1 respectively. min and x max The minimum and maximum values ​​of the y-coordinate are denoted as y = y'. min and y max , with (x min ,y min ), (x max ,y min ), (x max ,y max ), (x min ,y max Four points define a rectangular mirror field region, and the grid is divided into squares with a side length of d. cell,field This value satisfies 2d thre ≥d cell,field ≥d thre ;d thre Distance threshold;

[0016] After partitioning, there are n x,field line n y,field Column grid, satisfying:

[0017] x max -x min +d cell,field >n x,field d cell,field ≥x max -x min

[0018] y max -y min +d cell,field >n y,field d cell,field ≥y max -y min

[0019] Columns are numbered from left to right, starting with 0; rows are numbered from bottom to top, also starting with 0; the grid is numbered by column and row numbers. For column number i... x The row number is i y The grid number is (i x i y );

[0020] Let the coordinates of a heliostat be (x h ,y h If ), then the column number i of the grid to which it belongs is... x,h and row number i y,h Represented as:

[0021]

[0022] in, Indicates rounding down;

[0023] Calculate the grid to which each heliostat belongs using the above formula, and record which heliostats are in each grid.

[0024] In the above scheme, step 2 is performed as follows:

[0025] For a heliostat in a grid, calculate its distance to other heliostats in the same grid. If the distance is less than a distance threshold d... thre If they are neighboring heliostats, then they are the neighboring heliostats in the grid. Repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the grid.

[0026] For a heliostat in a grid, calculate its distance to each heliostat in the adjacent grids. If the distance is less than the distance threshold d... thre If they are neighboring heliostats, then they are neighboring heliostats; repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the adjacent grid.

[0027] Adding the two sets of neighboring heliostats together yields all the neighboring heliostats for each heliostat.

[0028] In the above scheme, step 4 includes the following process:

[0029] Step 4.1: Identify neighboring heliostats that may cast shadows in front of a typical heliostat, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat.

[0030] Step 4.2: Determine if there are neighboring heliostats that may be obstructing a typical heliostat in front of it, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat.

[0031] Step 4.3: Remove the overlapping parts in the shadow occlusion area to obtain the shadow occlusion ratio.

[0032] In a further technical solution, step 4.1, the specific method for determining neighboring heliostats that may cast shadows in front of a typical heliostat is as follows:

[0033] First, calculate the normal direction of a typical heliostat:

[0034] If the center coordinate of the absorber is (x r ,y r ,z r The coordinates of a typical heliostat, numbered h, are (x...). h ,y h ,z h If the unit vector of the reflected ray from the center of the heliostat is (x), then... reflect,h ,y reflect,h ,z reflect,h ) is represented as:

[0035]

[0036] Where, d r,h The distance between the receiver and this typical heliostat is expressed as:

[0037]

[0038] The solar unit vector (x) at the current moment s ,y s ,z s If the normal direction unit vector (x) is given, then... n ,y n ,z n ) is represented as:

[0039]

[0040] Where d0 represents the normalization factor of the normal vector, expressed as:

[0041]

[0042] The coordinates of a neighboring heliostat of this typical heliostat are (x... nei ,y nei ,z nei The vector from the typical heliostat to its neighboring heliostat is (x...). nei -x h ,y nei -y h ,z nei -z h The dot product of this vector and the normal direction of this typical heliostat is:

[0043] (x nei -x h )x n +(y nei -y h )y n +(z nei -z h)z n

[0044] If the value is greater than 0, then the neighboring heliostat is located in front of the typical heliostat;

[0045] Repeat this operation for all neighboring heliostats of the typical heliostat to select all neighboring heliostats located in front of the typical heliostat.

[0046] Let the angle threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied,

[0047]

[0048] The neighboring heliostat may cast a shadow on this typical heliostat.

[0049] In a further technical solution, step 4.1, the specific method for calculating the mirror projection coordinates of neighboring heliostats that may be shadowed on the typical heliostat is as follows:

[0050] Let the coordinates of this typical heliostat be (x h ,y h ,z h ), the solar unit vector at the current moment (x) s ,y s ,z s The coordinates of a neighboring heliostat located in front of the current heliostat and within the angle threshold are (x...). nei ,y nei ,z nei If the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y), then the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y). nei -x h ,y nei -y h ,z nei -z h ), abbreviated as (x nei,h ,y nei,h ,z nei,h ); Normal vector (x) n ,y n ,z n The reduced component p in the xy plane is expressed as:

[0051]

[0052] If p = 0, then the mirror coordinates (x) of the projection point of the neighboring heliostat onto the plane of the current typical heliostat are... e ,ye ) is represented as:

[0053]

[0054] Among them, the mirror coordinate system represents a planar coordinate system with the current heliostat center as the origin, the length direction of the mirror as the x-axis, and the width direction of the mirror as the y-axis;

[0055] If p≠0, the heliostat coordinates of the projection point (x) nei,proj,h ,y nei,proj,h ,z nei,proj,h ) is represented as:

[0056]

[0057] The mirror coordinates of the projection point (x) e ,y e ) is represented as:

[0058]

[0059] In a further technical solution, step 4.2, the specific method for determining whether a neighboring heliostat might be obstructing the view in front of a typical heliostat is to replace the incident light with the reflected light. Following the method in step 4.1, the neighboring heliostats that might be obstructing the view in front of a typical heliostat can be determined. Let the angle threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied,

[0060]

[0061] The neighboring heliostat may cause obstruction on this typical heliostat.

[0062] In a further technical solution, step 4.2, the method for calculating the mirror projection coordinates of a neighboring heliostat that may be obstructing the view on the typical heliostat is as follows:

[0063] If p = 0, then the mirror coordinates (x′) of the projection point of a neighboring heliostat that may be obstructing the plane of the current typical heliostat are as follows: e ,y′ e ) is represented as:

[0064]

[0065] If p≠0, the coordinates (x′) of the projection point of the neighboring heliostat center nei,proj,h ,y′ nei,proj,h ,z′nei,proj,h ) is represented as:

[0066]

[0067] Its coordinates in the mirror coordinate system are:

[0068]

[0069] In a further technical solution, the specific method of step 4.3 is as follows:

[0070] (1) Determine if there is shadow occlusion;

[0071] If |x e | <L x And |y e | <L y If |x′ e | <L x And |y′ e | <L y This will cause occlusion, where L x L represents the length of the mirror. y Indicates the width of the mirror; (x e ,y e () represents the mirror coordinates of the projection point of the neighboring heliostat coordinates onto the plane where the current typical heliostat is located;

[0072] (2) Group the projected coordinates that produce shadow occlusion;

[0073] Group the projection points of the centers of adjacent heliostats that are shaded by whether they are located to the left or right of the current typical heliostat; if x e If x' < 0, then it is assigned to group 1; otherwise, it is assigned to group 2. e If the value is less than 0, the child will be assigned to group 3; otherwise, they will be assigned to group 4.

[0074] (3) Calculate the length and width of each shadow occlusion rectangle;

[0075] The length L of a shaded rectangle s,x and width L s,y They are represented as follows:

[0076] L s,x =L x -|x e |

[0077] L s,y =L y -|y e |

[0078] Similarly, a rectangle of length L that is obscured... b,x and width Lb,y They are represented as follows:

[0079] L b,x =L x -|x′ e |

[0080] L b,y =L y -|y′ e |

[0081] (4) Calculate the shadow occlusion ratio of each group after deduplication;

[0082] For the shadowed case, the maximum values ​​of the length and width of a set of shadowed rectangles are L and L respectively. s,x,max and L s,y,max Let the side length of a small square grid be L. cell Then the maximum value of the length and width of this set of rectangular shaded areas corresponds to the number of grid cells N. s,x,max and N s,y,max They are respectively:

[0083] N s,x,max =round(L s,x,max / L cell )

[0084] N s,y,max =round(L s,y,max / L cell )

[0085] Here, round(...) means rounding to the nearest integer;

[0086] For each of these rectangles, we can calculate the number of cells N corresponding to its length and width. s,x and N s,y They are respectively:

[0087] N s,x =round(L s,x / L cell )

[0088] N s,y =round(L s,y / L cell )

[0089] Then define a size of N s,x,max ×N s,y,max Matrix M g Initially, all elements are 0, and one cell in a rectangle corresponds to a matrix M. g An element in the array is given, where g represents the group number; the element corresponding to each rectangle in this group is then assigned the value 1, i.e., let:

[0090] Mg,ij (N s,y ≥i≥1,N s,x ≥j≥1)=1

[0091] The above operation will not recalculate the overlapping shadow area for matrix M. g The number of shaded squares can be obtained by summing all the elements.

[0092] For occlusion cases, the calculation method is the same as for shadow cases;

[0093] Adding the number of shadowed squares in the four groups together and dividing by the area of ​​the heliostat gives the shadowing ratio r of a typical heliostat numbered h. h ,Right now

[0094]

[0095] In the above scheme, the specific method of step 5 is as follows:

[0096] For each typical heliostat selected within the grid defined in step 3, the shading ratio is calculated according to step 4. The shading ratio of other heliostats within a grid is taken as the same as the result of the typical heliostat within that grid. Then, the shading ratio r of each heliostat is calculated. h If all of these can be obtained, then the overall shadow occlusion efficiency η of the mirror field can be expressed as:

[0097]

[0098] Where, N helio This represents the total number of heliostats in the field of view.

[0099] Through the above technical solution, the rapid calculation method for shadow occlusion efficiency of tower-type photothermal mirror field provided by the present invention has the following beneficial effects:

[0100] 1. This invention transforms global brute-force calculation into local grid calculation by using a "grid partitioning + neighbor search algorithm", which greatly reduces the amount of computation without reducing accuracy.

[0101] 2. By adopting the "typical heliostat selection" strategy, the computational load was reduced and the computational efficiency was improved with a slight decrease in accuracy.

[0102] 3. The central projection method of adjacent heliostats and the rectangular approximation of the projection shape of nearby heliostats are used. The central projection of heliostats is used instead of the geometric projection of heliostats, which greatly reduces the amount of calculation without reducing the calculation accuracy.

[0103] 4. The shadow occlusion grid partitioning matrix assignment method avoids directly calculating the overlap of geometric shapes, reducing computational complexity. While ensuring sufficient accuracy, it significantly reduces the amount of computation and improves computational efficiency.

[0104] 5. The grid size and shadow occlusion rectangle size of a typical heliostat are adjustable, making the calculation accuracy and computational load adjustable. Appropriate parameters can be selected according to the actual situation.

[0105] 6. The method proposed in this invention provides an effective means for rapid calculation when selecting tower height, heat storage capacity, mirror size and layout in the design of photothermal mirror fields. Attached Figure Description

[0106] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0107] Figure 1 This is a schematic diagram of a rapid calculation method for the shadow occlusion efficiency of a tower-type photothermal mirror field disclosed in an embodiment of the present invention.

[0108] Figure 2 A schematic diagram showing the selection of a neighboring heliostat. Detailed Implementation

[0109] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0110] This invention provides a rapid method for calculating the shadow occlusion efficiency of a tower-type photothermal mirror field, such as... Figure 1 As shown, it includes the following steps:

[0111] Step 1: Based on the heliostat coordinate data, divide the mirror field into several square grids, determine the grid to which each heliostat belongs, and record which heliostats are in each grid.

[0112] The specific method is as follows:

[0113] The minimum and maximum x-coordinates of all heliostats within the field of view are denoted as x0 and x1 respectively. min and x max The minimum and maximum values ​​of the y-coordinate are denoted as y = y'. min and y max , with (x min ,y min ), (x max ,y min ), (x max ,y max ), (x min ,y max Four points define a rectangular mirror field region, and the grid is divided into squares with a side length of d. cell,field This value satisfies 2d thre ≥d cell,field ≥d thre ;dthre Distance threshold;

[0114] After partitioning, there are n x,field line n y,field Column grid, satisfying:

[0115] x max -x min +d cell,field >n x,field d cell,field ≥x max -x min

[0116] y max -y min +d cell,field >n y,field d cell,field ≥y max -y min

[0117] Columns are numbered from left to right, starting with 0; rows are numbered from bottom to top, also starting with 0; the grid is numbered by column and row numbers. For column number i... x The row number is i y The grid number is (i x i y );

[0118] Let the coordinates of a heliostat be (x h ,y h If ), then the column number i of the grid to which it belongs is... x,h and row number i y,h Represented as:

[0119]

[0120] in, Indicates rounding down;

[0121] Calculate the grid to which each heliostat belongs using the above formula, and record which heliostats are in each grid.

[0122] Step 2: Within the grid framework of Step 1, for each heliostat, identify the heliostats within its own grid and adjacent grids that are less than a distance threshold as neighboring heliostats; adjacent grids refer to the three grids above (top left, top right, and top right) and the grid to the right of the grid containing the heliostat, such as... Figure 2 As shown.

[0123] The specific method is as follows:

[0124] For a heliostat in a grid, calculate its distance to other heliostats in the same grid. If the distance is less than a distance threshold d... threIf they are neighboring heliostats, then they are neighboring heliostats. Repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the grid. If the distance has already been calculated with all other heliostats, it will not be calculated again.

[0125] For a heliostat in a grid, calculate its distance to each heliostat in the adjacent grids. If the distance is less than the distance threshold d... thre If they are neighboring heliostats, then they are neighboring heliostats; repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the adjacent grid.

[0126] Adding the two sets of neighboring heliostats together yields all the neighboring heliostats for each heliostat.

[0127] Step 3, reselect the side length d cell,field,2 The mirror field is re-divided into several square grids, and then a heliostat is randomly selected from each grid as a typical heliostat. When the side length of the grid is less than the minimum distance between the heliostats, all heliostats will be selected as typical heliostats, which has the highest accuracy but the largest amount of computation.

[0128] Step 4: For each typical heliostat, calculate the occlusion ratio of its neighboring heliostats, and use the occlusion ratio of the typical heliostat as the occlusion ratio of its grid.

[0129] The process includes the following:

[0130] Step 4.1: Identify neighboring heliostats that may cast shadows in front of a typical heliostat, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat.

[0131] The specific method for determining neighboring heliostats that may cast a shadow in front of a typical heliostat is as follows:

[0132] First, calculate the normal direction of a typical heliostat:

[0133] If the center coordinate of the absorber is (x r ,y r ,z r The coordinates of a typical heliostat, numbered h, are (x...). h ,y h ,z h If the unit vector of the reflected ray from the center of the heliostat is (x), then... reflect,h ,y reflect,h ,z reflect,h ) is represented as:

[0134]

[0135] Where, d r,hThe distance between the receiver and this typical heliostat is expressed as:

[0136]

[0137] The solar unit vector (x) at the current moment s ,y s ,z s If the normal direction unit vector (x) is given, then... n ,y n ,z n ) is represented as:

[0138]

[0139] Where d0 represents the normalization factor of the normal vector, expressed as:

[0140]

[0141] The coordinates of a neighboring heliostat of this typical heliostat are (x... nei ,y nei ,z nei The vector from the typical heliostat to its neighboring heliostat is (x...). nei -x h ,y nei -y h ,z nei -z h The dot product of this vector and the normal direction of this typical heliostat is:

[0142] (x nei -x h )x n +(y nei -y h )y n +(z nei -z h )z n

[0143] If the value is greater than 0, then the neighboring heliostat is located in front of the typical heliostat;

[0144] Repeat this operation for all neighboring heliostats of the typical heliostat to select all neighboring heliostats located in front of the typical heliostat.

[0145] Only heliostats within a certain angular range on either side of the line on which the incident ray projects onto the ground can produce a shadow on the current heliostat. Let the angular threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied,

[0146]

[0147] The neighboring heliostat may cast a shadow on this typical heliostat.

[0148] The specific method for calculating the mirror projection coordinates of neighboring heliostats that may be shadowed onto this typical heliostat is as follows:

[0149] Let the coordinates of this typical heliostat be (x h ,y h ,z h ), the solar unit vector at the current moment (x) s ,y s ,z s The coordinates of a neighboring heliostat located in front of the current heliostat and within the angle threshold are (x...). nei ,y nei ,z nei If the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y), then the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y). nei -x h ,y nei -y h ,z nei -z h ), abbreviated as (x nei,h ,y nei,h ,z nei,h ); Normal vector (x) n ,y n ,z n The reduced component p in the xy plane is expressed as:

[0150]

[0151] The equation of a straight line parallel to the incident ray passing through the center of the mirror of a neighboring heliostat in this typical heliostat coordinate system is:

[0152]

[0153] If p = 0, then the normal vector points directly upwards, and the equation of the heliostat plane is:

[0154]

[0155] By combining the equations of the line and the plane, we can obtain the mirror coordinates (x, y) of the projection point of the neighboring heliostat onto the plane containing the current typical heliostat. e ,y e ), represented as:

[0156]

[0157] Among them, the mirror coordinate system represents a planar coordinate system with the current heliostat center as the origin, the length direction of the mirror as the x-axis, and the width direction of the mirror as the y-axis;

[0158] If p≠0, the equation of the heliostat plane is:

[0159] x n x+y n y+z n z = 0

[0160] The equation of the line from the x-axis of the mirror coordinate system to the heliostat coordinate system is:

[0161]

[0162] That is, the vector of the x-axis in the mirror coordinate system is (n y ,-n x If the x-axis passes through the center of the mirror and is perpendicular to the x-axis of the mirror coordinate system, then the equation of the plane is:

[0163] y n xx n y = 0

[0164] This plane is the plane defined by the normal and the y-axis of the mirror coordinate system;

[0165] The equation of the line from the y-axis of the mirror coordinate system to the heliostat coordinate system is:

[0166]

[0167] The equation of the plane determined by the normal and the x-axis of the mirror coordinate system is:

[0168] x n z n x+y n z n y-(x n 2 +y n 2 z = 0

[0169] The distance from the projection point to the x-axis of the mirror coordinate system is the y-axis. e The distance from the projection point to the y-axis of the mirror coordinate system is x. e That is, the distance vector from the projection point to the plane determined by the normal and the x-axis of the mirror coordinate system is y. e The distance vector from the projection point to the plane defined by the normal and the y-axis of the mirror coordinate system is x. e ;

[0170] The coordinates of the projection point are the intersection of the line parallel to the incident ray passing through the center of the neighboring heliostat's mirror and the heliostat plane, i.e., the point determined by the following system of equations:

[0171]

[0172] Solving for the coordinates (x) of the projection point yields the coordinates. nei,proj,h ,y nei,proj,h ,z nei,proj,h ) is represented as:

[0173]

[0174] Since the distance vector from the projection point to the plane determined by the normal and the y-axis of the mirror coordinate system is x e Then it is represented as:

[0175]

[0176] The distance vector from the projection point to the plane defined by the normal and the x-axis of the mirror coordinate system is y. e ,but

[0177]

[0178] Step 4.2: Determine if there are neighboring heliostats that may be obstructing a typical heliostat in front of it, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat.

[0179] The specific method for determining which neighboring heliostats might be obstructing the path in front of a typical heliostat is to replace the incident ray with the reflected ray, and then follow the method in step 4.1 to find which neighboring heliostats might be obstructing the path in front of a typical heliostat; let the angle threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied,

[0180]

[0181] The neighboring heliostat may cause obstruction on this typical heliostat.

[0182] The method for calculating the mirror projection coordinates of a neighboring heliostat that may cause occlusion on this typical heliostat is as follows:

[0183] If p = 0, then the mirror coordinates (x′) of the projection point of a neighboring heliostat that may be obstructing the plane of the current typical heliostat are as follows: e ,y′ e ) is represented as:

[0184]

[0185] If p≠0, the coordinates (x′) of the projection point of the neighboring heliostat center nei,proj,h ,y′ nei,proj,h ,z′ nei,proj,h ) is represented as:

[0186]

[0187] Its coordinates in the mirror coordinate system are:

[0188]

[0189] Step 4.3: Remove the overlapping parts in the shadow occlusion area to obtain the shadow occlusion ratio.

[0190] The specific method is as follows:

[0191] (1) Determine if there is shadow occlusion;

[0192] If |x e | <L x And |y e | <L y If |x′ e | <L x And |y′ e | <L y This will cause occlusion, where L x L represents the length of the mirror. y Indicates the width of the mirror; (x e ,y e () represents the mirror coordinates of the projection point of the neighboring heliostat coordinates onto the plane where the current typical heliostat is located;

[0193] (2) Group the projected coordinates that produce shadow occlusion;

[0194] Group the projection points of the centers of adjacent heliostats that are shaded by whether they are located to the left or right of the current typical heliostat; if x e If x' < 0, then it is assigned to group 1; otherwise, it is assigned to group 2. e If the value is less than 0, the child will be assigned to group 3; otherwise, they will be assigned to group 4.

[0195] (3) Calculate the length and width of each shadow occlusion rectangle;

[0196] The length L of a shaded rectangle s,x and width L s,y They are represented as follows:

[0197] L s,x =L x -|x e |

[0198] Ls,y =L y -|y e |

[0199] Similarly, a rectangle of length L that is obscured... b,x and width L b,y They are represented as follows:

[0200] L b,x =L x -|x′ e |

[0201] L b,y =L y -|y′ e |

[0202] (4) Calculate the shadow occlusion ratio of each group after deduplication;

[0203] For the shadowed case, the maximum values ​​of the length and width of a set of shadowed rectangles are L and L respectively. s,x,max and L s,y,max Let the side length of a small square grid be L. cell Then the maximum value of the length and width of this set of rectangular shaded areas corresponds to the number of grid cells N. s,x,max and N s,y,max They are respectively:

[0204] N s,x,max =round(L s,x,max / L cell )

[0205] N s,y,max =round(L s,y,max / L cell )

[0206] Here, round(...) means rounding to the nearest integer;

[0207] For each of these rectangles, we can calculate the number of cells N corresponding to its length and width. s,x and N s,y They are respectively:

[0208] N s,x =round(L s,x / L cell )

[0209] N s,y =round(L s,y / L cell )

[0210] Then define a size of N s,x,max ×N s,y,max Matrix M gInitially, all elements are 0, and one cell in a rectangle corresponds to a matrix M. g An element in the array is given, where g represents the group number; the element corresponding to each rectangle in this group is then assigned the value 1, i.e., let:

[0211] M g,ij (N s,y ≥i≥1,N s,x ≥j≥1)=1

[0212] The above operation will not recalculate the overlapping shadow area for matrix M. g The number of shaded squares can be obtained by summing all the elements.

[0213] For occlusion cases, the calculation method is the same as for shadow cases;

[0214] Adding the number of shadowed squares in the four groups together and dividing by the area of ​​the heliostat gives the shadowing ratio r of a typical heliostat numbered h. h ,Right now

[0215]

[0216] Step 5: Calculate the shading ratio of all typical heliostats to estimate the shading efficiency of the entire field of view.

[0217] The specific method is as follows:

[0218] For each typical heliostat selected within the grid defined in step 3, the shading ratio is calculated according to step 4. The shading ratio of other heliostats within a grid is taken as the same as the result of the typical heliostat within that grid. Then, the shading ratio r of each heliostat is calculated. h If all of these can be obtained, then the overall shadow occlusion efficiency η of the mirror field can be expressed as:

[0219]

[0220] Where, N helio This represents the total number of heliostats in the field of view.

[0221] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rapid calculation method for the shadow occlusion efficiency of a tower-type photothermal mirror field, characterized in that, Includes the following steps: Step 1: Based on the heliostat coordinate data, divide the mirror field into several square grids, determine the grid to which each heliostat belongs, and record which heliostats are in each grid; Step 2: Within the grid framework of Step 1, for each heliostat, determine the heliostats in its own grid and adjacent grids that are less than the distance threshold as neighboring heliostats; adjacent grids refer to the three grids above the grid and the grid to the right of the grid in which the heliostat is located. Step 3: Select new side lengths and re-divide the mirror field into several square grids. Then, randomly select one heliostat from each grid as a typical heliostat. Step 4: For each typical heliostat, calculate the occlusion ratio of its neighboring heliostats, and use the occlusion ratio of the typical heliostat as the occlusion ratio of its grid. Step 5: Calculate the shading ratio of all typical heliostats to estimate the shading efficiency of the entire field of view.

2. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 1, characterized in that, The method for step 1 is as follows: The minimum and maximum x-coordinates of all heliostats within the field of view are denoted as x0 and x1 respectively. min and x max The minimum and maximum values ​​of the y-coordinate are denoted as y = y'. min and y max , with (x min ,y min ), (x max ,y min ), (x max ,y max ), (x min ,y max Four points define a rectangular mirror field region, and the grid is divided into squares with a side length of d. cell,field This value satisfies 2d thre ≥d cell,field ≥d thre ;d thre Distance threshold; After partitioning, there are n x,field line n y,field Column grid, satisfying: x max -x min +d cell,field >n x,field d cell,field ≥x max -x min y max -y min +d cell,field >n y,field d cell,field ≥y max -y min Columns are numbered from left to right, starting with 0; rows are numbered from bottom to top, also starting with 0; the grid is numbered by column and row numbers. For column number i... x The row number is i y The grid number is (i x i y ); Let the coordinates of a heliostat be (x h ,y h If ), then the column number i of the grid to which it belongs is... x,h and row number i y,h Represented as: in, Indicates rounding down; Calculate the grid to which each heliostat belongs using the above formula, and record which heliostats are in each grid.

3. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 1, characterized in that, Step 2 is as follows: For a heliostat in a grid, calculate its distance to other heliostats in the same grid. If the distance is less than a distance threshold d... thre If they are neighboring heliostats, then they are the neighboring heliostats in the grid. Repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the grid. For a heliostat in a grid, calculate its distance to each heliostat in the adjacent grids. If the distance is less than the distance threshold d... thre If they are neighboring heliostats, then they are neighboring heliostats; repeat this operation for each heliostat in the grid and record the neighboring heliostats of each heliostat in the adjacent grid. Adding the two sets of neighboring heliostats together yields all the neighboring heliostats for each heliostat.

4. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 1, characterized in that, Step 4 includes the following process: Step 4.1: Identify neighboring heliostats that may cast shadows in front of a typical heliostat, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat. Step 4.2: Determine if there are neighboring heliostats that may be obstructing a typical heliostat in front of it, and calculate the mirror projection coordinates of these neighboring heliostats on the typical heliostat. Step 4.3: Remove the overlapping parts in the shadow occlusion area to obtain the shadow occlusion ratio.

5. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 4, characterized in that, In step 4.1, the specific method for determining neighboring heliostats that may cast a shadow in front of a typical heliostat is as follows: First, calculate the normal direction of a typical heliostat: If the center coordinate of the absorber is (x r ,y r ,z r The coordinates of a typical heliostat, numbered h, are (x...). h ,y h ,z h If the unit vector of the reflected ray from the center of the heliostat is (x), then... reflect,h ,y reflect,h ,z reflect,h ) is represented as: Where, d r,h The distance between the receiver and this typical heliostat is expressed as: The solar unit vector (x) at the current moment s ,y s ,z s If the normal direction unit vector (x) is given, then... n ,y n ,z n ) is represented as: Where d0 represents the normalization factor of the normal vector, expressed as: The coordinates of a neighboring heliostat of this typical heliostat are (x... nei ,y nei ,z nei The vector from the typical heliostat to its neighboring heliostat is (x...). nei -x h ,y nei -y h ,z nei -z h The dot product of this vector and the normal direction of this typical heliostat is: (x nei -x h )x n +(y nei -y h )y n +(z nei -z h )z n If the value is greater than 0, then the neighboring heliostat is located in front of the typical heliostat; Repeat this operation for all neighboring heliostats of the typical heliostat to select all neighboring heliostats located in front of the typical heliostat. Let the angle threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied, The neighboring heliostat may cast a shadow on this typical heliostat.

6. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 4, characterized in that, In step 4.1, the specific method for calculating the mirror projection coordinates of neighboring heliostats that may be shadowed on the typical heliostat is as follows: Let the coordinates of this typical heliostat be (x h ,y h ,z h ), the solar unit vector at the current moment (x) s ,y s ,z s The coordinates of a neighboring heliostat located in front of the current heliostat and within the angle threshold are (x...). nei ,y nei ,z nei If the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y), then the relative coordinates of the neighboring heliostat with respect to the current heliostat are (x, y). nei -x h ,y nei -y h ,z nei -z h ), abbreviated as (x nei,h ,y nei,h ,z nei,h ); Normal vector (x) n ,y n ,z n The reduced component p in the xy plane is expressed as: If p = 0, then the mirror coordinates (x) of the projection point of the neighboring heliostat onto the plane of the current typical heliostat are... e ,y e ) is represented as: Among them, the mirror coordinate system represents a planar coordinate system with the current heliostat center as the origin, the length direction of the mirror as the x-axis, and the width direction of the mirror as the y-axis; If p≠0, the heliostat coordinates of the projection point (x) nei,proj,h ,y nei,proj,h ,z nei,proj,h ) is represented as: The mirror coordinates of the projection point (x) e ,y e ) is represented as:

7. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 5, characterized in that, In step 4.2, the specific method for determining which neighboring heliostats might be obstructing the path in front of a typical heliostat is to replace the incident ray with the reflected ray. Following the method in step 4.1, the neighboring heliostats that might be obstructing the path in front of a typical heliostat can be determined. Let the angle threshold be α. thre The coordinates (x) of a neighboring heliostat located in front of this typical heliostat. nei ,y nei ,z nei When the following formula is satisfied, The neighboring heliostat may cause obstruction on this typical heliostat.

8. The method for rapidly calculating the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 7, characterized in that, In step 4.2, the method for calculating the mirror projection coordinates of potentially obstructing neighboring heliostats on the typical heliostat is as follows: If p = 0, then the mirror coordinates (x′) of the projection point of a neighboring heliostat that may be obstructing the plane of the current typical heliostat are as follows: e ,y′ e ) is represented as: If p≠0, the coordinates (x′) of the projection point of the neighboring heliostat center nei,proj,h ,y′ nei,proj,h ,z′ nei,proj,h ) is represented as: Its coordinates in the mirror coordinate system are:

9. A rapid calculation method for the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 4, characterized in that, The specific method for step 4.3 is as follows: (1) Determine if there is shadow occlusion; If |x e | <L x And |y e | <L y If |x′ e | <L x And |y′ e | <L y This will cause occlusion, where L x L represents the length of the mirror. y Indicates the width of the mirror; (x e ,y e () represents the mirror coordinates of the projection point of the neighboring heliostat coordinates onto the plane where the current typical heliostat is located; (2) Group the projected coordinates that produce shadow occlusion; Group the projection points of the centers of adjacent heliostats that are shaded by whether they are located to the left or right of the current typical heliostat; if x e If x' < 0, then it is assigned to group 1; otherwise, it is assigned to group 2. e If the value is less than 0, the child will be assigned to group 3; otherwise, they will be assigned to group 4. (3) Calculate the length and width of each shadow occlusion rectangle; The length L of a shaded rectangle s,x and width L s,y They are represented as follows: L s,x =L x -|x e | L s,y =L y -|y e | Similarly, a rectangle of length L that is obscured... b,x and width L b,y They are represented as follows: L b,x =L x -|x′ e | L b,y =L y -|y′ e | (4) Calculate the shadow occlusion ratio of each group after deduplication; For the shadowed case, the maximum values ​​of the length and width of a set of shadowed rectangles are L and L respectively. s,x,max and L s,y,max Let the side length of a small square grid be L. cell Then the maximum value of the length and width of this set of rectangular shaded areas corresponds to the number of grid cells N. s,x,max and N s,y,max They are respectively: N s,x,max =round(L s,x,max / L cell ) N s,y,max =round(L s,y,max / L cell ) Here, round(...) means rounding to the nearest integer; For each of these rectangles, we can calculate the number of cells N corresponding to its length and width. s,x and N s,y They are respectively: N s,x =round(L s,x / L cell ) N s,y =round(L s,y / L cell ) Then define a size of N s,x,max ×N s,y,max Matrix M g Initially, all elements are 0, and one cell in a rectangle corresponds to a matrix M. g An element in the array is given, where g represents the group number; the element corresponding to each rectangle in this group is then assigned the value 1, i.e., let: M g,ij (N s,y ≥i≥1,N s,x ≥j≥1)=1 The above operation will not recalculate the overlapping shadow area for matrix M. g The number of shaded squares can be obtained by summing all the elements. For occlusion cases, the calculation method is the same as for shadow cases; Adding the number of shadowed squares in the four groups together and dividing by the area of ​​the heliostat gives the shadowing ratio r of a typical heliostat numbered h. h ,Right now 10. A rapid calculation method for the shadow occlusion efficiency of a tower-type photothermal mirror field according to claim 1, characterized in that, The specific method for step 5 is as follows: For each typical heliostat selected within the grid defined in step 3, the shading ratio is calculated according to step 4. The shading ratio of other heliostats within a grid is taken as the same as the result of the typical heliostat within that grid. Then, the shading ratio r of each heliostat is calculated. h If all of these can be obtained, then the overall shadow occlusion efficiency η of the mirror field can be expressed as: Where, N helio This represents the total number of heliostats in the field of view.

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