CN115540367A - Sectional CPC solar concentrator and design method thereof - Google Patents

Abstract

The invention provides a segmented CPC solar concentrator and its design method. The composite parabolic reflector is fixed in the frame; the flat receiving surface is the heat-absorbing surface of the flat light concentrating receiver, and the composite parabolic reflector is symmetrically placed on the flat plate. Both sides of the receiving surface; the compound parabolic reflector is composed of multiple sub-reflectors, and each sub-reflector is connected end-to-end in turn, and the focal lines generated by each sub-reflector on the flat receiving surface are evenly arranged from the middle to both sides from bottom to top. The positions of the focal lines of each sub-mirror are different, and the focal lines are parallel to each other. In the present invention, the profile of the traditional trough-type parabolic concentrator is designed in sections, so that the energy flow density on the receiving surface of the flat plate is evenly distributed in multi-focal lines, and the uniformity of the energy flow density distribution on the receiving surface of the flat plate of the concentrator is effectively improved. , which greatly reduces the concentration of thermal stress on the receiving surface of the flat plate, thereby effectively prolonging the service life of the concentrator.

Description

A segmented CPC solar concentrator and its design method

technical field

The invention belongs to the field of solar concentrators, in particular to a segmented CPC solar concentrator and a design method thereof.

Background technique

Solar energy is a clean and renewable energy, which plays an increasingly important role in national economic development and people's daily life. The solar energy flux density irradiated on the ground is relatively low, about 1kW/m ² , which limits the degree of solar energy utilization and photothermal/photoelectric conversion efficiency. The solar concentrator gathers the sunlight together, enhances the solar energy flux density on the receiving surface of the flat plate, and lays the foundation for solar energy medium and high temperature heat utilization and concentrated photovoltaic power generation.

According to the way of light propagation, solar concentrators can be divided into three categories: reflective concentrators, refraction concentrators, and hybrid concentrators. The tower-type and dish-type concentrators in the reflective concentrator gather the incident sunlight into a point shape and concentrate it in a small range, which greatly improves the solar energy flux density, but it needs two-dimensional tracking of the sun's motion azimuth, and the tracking device And control system cost is higher. Reflective concentrators such as trough type, compound parabolic reflector, and linear Fresnel converge the sunlight into a linear shape and project it onto the receiving surface of the flat panel. The tracking accuracy required is small, and one-dimensional tracking is sufficient. Among them, the flat-plate compound parabolic reflector concentrator (CPC for short) is a solar heat collection device at medium temperature. This kind of concentrator is designed according to the principle of edge light, and can reflect the incident light within a given acceptance angle range to the receiver. On the other hand, the receiver is a flat plate, and the concentrator has a simple structure, and the processing accuracy of the concentrating surface is not high.

At present, CPC has been promoted and utilized in solar energy medium and low temperature occasions, such as heating, material drying, and heat preservation of agricultural facilities. Sunlight is irradiated on the parabolic surface through the CPC lighting surface, and then converges on the flat receiving surface after one or more reflections. The light transmission process loses less, and the incident light within the range of the receiving angle can be effectively collected. However, limited by the structural characteristics of CPC, the distribution of solar energy flow on the flat receiving surface is extremely uneven, showing the characteristics of high at both ends and low in the middle, and the difference is huge. This extremely uneven energy flow distribution makes the photothermal conversion process inefficient, and at the same time causes uneven temperature distribution of the conversion device, which is prone to thermal stress damage, which affects and limits the promotion of CPC concentrators and the efficient use of solar energy.

Contents of the invention

When the traditional CPC is running, the distribution of energy flux density on the receiving surface of the flat plate is not uniform, which not only reduces the photothermal efficiency, but also makes the conversion device very easy to cause thermal stress damage due to the large temperature difference. The focal point of each profile line is evenly distributed, which greatly improves the uniformity of solar energy flow distribution on the flat receiving surface, thereby laying the foundation for the safe and economical operation of CPC.

The specific technical solutions are:

A segmented CPC solar concentrator, comprising: a frame, a composite parabolic reflector, a flat receiving surface, an incident surface, a backing plate, a glass cover; the composite parabolic reflector is fixed in the frame; the flat receiving surface is a flat plate The heat-absorbing surface of the light concentrating receiver; the compound parabolic reflector is symmetrically placed on both sides of the flat receiving surface; the compound parabolic reflector is composed of multiple sub-reflectors, and each sub-reflector is connected end-to-end in sequence, and each sub-reflector from bottom to top The focal lines produced by the mirrors on the receiving surface of the plate are evenly arranged from the middle to both sides in sequence, and the focal lines of each sub-mirror are in different positions, and the focal lines are parallel to each other;

A backing plate is arranged under the receiving surface of the flat panel, and a glass cover is arranged on the top of the frame.

The specific design method of the multi-segment sub-mirror of the compound parabolic reflector is as follows:

S1. Determine the number of segments: The concentration ratio of the given concentrator is C, that is, the ratio of the area of the incident surface to the area of the receiving surface of the plate is C; when the sunlight is incident perpendicular to the incident surface, a part of the light is directly irradiated on the receiving surface of the plate , the other part of the light is reflected by the compound parabolic reflector and converges on the receiving surface of the flat plate, so as to achieve the purpose of concentrating light. Since only the light reflected by the compound parabolic reflector will form a focal line on the receiving surface of the plate, in order to improve the uniformity of light distribution on the receiving surface of the plate, the compound parabolic reflector is designed in sections, and the number of side sub-reflectors for C-1.

S2. Determine the arrangement of focal lines: each sub-reflector generates independent focal lines, and the left and right sides of the compound parabolic reflector are symmetrical, so the number of focal lines is 2 (C-1), which are evenly distributed on the receiving surface of the plate. The sub-mirrors on one side are connected end-to-end in turn, and the focal lines generated by the sub-mirrors on the flat receiving surface from bottom to top are evenly arranged in sequence from the middle to both sides.

S3. The profiled line equation of each paraboloid segment:

Given that the width of the flat receiving surface in the segmented concentrator is 2L, the sub-reflectors of the compound parabolic reflector are connected end to end in turn, and the initial section is fixed at the side of the flat receiving surface; XY is established with the midpoint of the flat receiving surface as the origin Two-dimensional Cartesian coordinate system, the XY coordinate plane is perpendicular to the focal line of each sub-mirror and the receiving surface of the plate, the intersection line of the XY coordinate plane and the receiving surface of the plate is the X axis, and the intersection line of the XY coordinate plane and the symmetry plane of the condenser is the Y axis . Starting from the sub-mirror connected to the receiving surface of the flat plate, number the sub-mirror with number i from bottom to top, and the initial segment is No. 1. Assume that the i-th segmented sub-mirror is in the XY coordinate system. The expression is 2P _i (Yb _i )=(Xa _i ) ² , and the parabolic line equation of the i-th segmented sub-mirror on the XY plane is determined by the following formula:

2P _i (y _i -b _i )=(xi-ai) ² (3)

The abscissa of the initial point of the i-th segmented sub-mirror:

x _i = iL (4)

The coordinates of the initial point of the i+1 segmented sub-mirror:

x _i+1 ＝(i+1)L＝x' _i y _i+1 ＝y' _i (5)

The initial point of the first segmented submirror is known:

x ₁ =L y ₁ =0 (6)

In the formula: a _i , b _i are the vertex parameters of the parabolic equation expression of the i-th segmented sub-mirror on the XY plane;

x _i , y _i are the initial point parameters of the parabolic equation expression of the i-th segmented sub-mirror on the XY plane;

x' _i , y' _i is the termination point parameter of the parabolic equation expression of the i-th segmented sub-mirror on the XY plane; it is also the initial point of the i+1 segmented sub-mirror's parabolic equation expression on the XY plane parameter;

C is the concentration ratio of the segmented parabolic concentrator;

P _i is the quasi-focal length of the i-th segmented sub-mirror in the parabolic equation expression on the XY plane.

Substituting formula (6)(2)(1) into formula (3), the parabolic equation of the first segmented sub-mirror on the XY plane can be obtained. Substituting formula (5) into the calculation of the parabolic equation of the first paragraph, the initial coordinates of the sub-reflector in the XY plane parabola are obtained, and similarly, the parabolic equation of each sub-reflector in the XY two-dimensional Cartesian coordinate system can be determined by successive iterations Expression, and the starting and ending coordinates ( _xi , y _i ) (x' _i , y' _i ) of all paraboloids in the XY two-dimensional Cartesian coordinate system to determine the installation position of the sub-mirror.

When the plurality of compound parabolic mirrors are arranged, the starting position of the (i+1)th parabolic mirror is located at the end position of the (i)th reflecting mirror, so as to minimize the gaps between the sub-mirrors.

The invention provides a segmented CPC solar concentrator and its design method. The traditional trough parabolic concentrator profile is designed in segments, so that the energy flux density on the receiving surface of the flat plate is evenly distributed in multi-focal lines. , which effectively improves the uniformity of energy flux density distribution on the receiving surface of the concentrator plate, greatly reduces the concentration of thermal stress on the receiving surface of the plate, and thus effectively prolongs the service life of the concentrator.

Description of drawings

Fig. 1a is the energy flow density distribution diagram of ordinary CPC;

Fig. 1 b is the energy flow density distribution diagram of segmented CPC of the present invention;

Fig. 2 is the structural diagram of segmented solar heat collector of the present invention;

Fig. 3 is the schematic diagram of the reflected light of segmented parabolic solar concentrator of the present invention;

Figure 4 is a schematic diagram of a common CPC light concentrator.

detailed description

The specific technical solutions of the present invention are described in conjunction with the examples.

Under the condition of parallel light incidence, as shown in Figure 1a, only the light incident on the reflector can produce the concentrating effect of ordinary CPC. Based on the comparison of the effective light-gathering incident surface area and the ineffective light-gathering incident area and the average theory, the compound parabolic reflector 2-2 is segmented to obtain the C-1 sub-reflector. On this basis, the focal lines of each segment are evenly distributed on the plate receiving surface 2-3, so that the focal lines are parallel to each other, and the distance between every two adjacent focal lines is equal. Given that the width of the flat receiving surface 2-3 in the segmented concentrator is 2L, all the sub-reflectors are connected to each other in turn, and an initial segment of the sub-reflector is fixed at the end of the flat receiving surface 2-3. The XY two-dimensional Cartesian coordinate system is established with the midpoint of the 2-3 type line of the flat receiving surface as the origin, and the XY coordinate plane is perpendicular to the focal line of the reflection surface of each sub-mirror and the flat receiving surface 2-3, and the XY coordinate plane and the flat receiving surface 2-3 The intersection line is the X axis, and the intersection line between the XY coordinate plane and the symmetry plane of the concentrator is the Y axis. From bottom to top, with the segmented sub-mirror connected to the flat receiving surface 2-3 as the starting surface, the sub-reflectors are numbered i in turn, and the number of the initial sub-mirror is No. 1, and the i-th sub-mirror is defined in The coordinates of the initial endpoint of the truncation segment on the XY coordinate plane are (x _i , y _i ). Since the adjacent sub-mirrors have a side collinear, the end point of the i-th sub-reflector on the XY coordinate plane is the same as The i+1th sub-mirror has the same initial end point coordinates of the intercept line segment on the XY coordinate plane, which is (x _i+1 , y _i+1 ). Assume that the i-th sub-mirror is on the XY coordinate system, the line equation expression 2P _i (Yb _i )=(Xa _i ) ² . Since the intercept point of the focal line of the sub-mirror on the XY coordinate plane (referred to as the profile focus) is on the X-axis, and the focal point is the same as the abscissa of the apex of the sub-mirror, the coordinates of the profile focus of the i-th sub-mirror are ( a _i , 0), according to the nature of the parabola, the apex and the focal point are located on the same vertical axis, and the difference between the vertical coordinates is the focal length, which is half of the quasi-focal length _Pi , so we have

n为单侧子反射镜的总数。所以第i个子反射镜对应的型线焦点坐标为

型线焦点在y轴右侧取正，左侧取负。顶点横坐标与焦点横坐标一致，所以顶点横坐标有：Under the condition that the effective light-receiving area of each sub-reflector remains unchanged, in order to relatively reduce the material cost of each sub-reflector, the focal line of the left sub-reflector can be set on the right side of the 2-3 symmetry plane of the receiving surface of the plate. Half, the focal line of the right side sub-reflector is located at the left half of the 2-3 symmetrical plane of the flat receiving surface (the reason is that the arc length of the parabolic shape has been reduced). Since there are i sub-mirrors on both sides, there are 2i focal lines on the receiving surface 2-3 of the plate. Assuming that the receiving surface 2-3 of the plate has a width of 2L, the distance between two adjacent focal lines is

n is the total number of single-sided sub-reflectors. Therefore, the coordinates of the profile focal point corresponding to the i-th sub-mirror are

The focus of the profile line is positive on the right side of the y-axis and negative on the left side. The abscissa of the vertex is consistent with the abscissa of the focus, so the abscissa of the vertex is:

The abscissa of the initial point of the i-th segmented sub-mirror:

x _i = iL (4)

As shown in Figure 3, the initial point of each segment is a connection point. Let x _i , y _i be the initial point parameters of the i-th sub-mirror in the parabola equation expression on the XY plane. x' _i , y' _i are the parameters of the termination point of the i-th sub-mirror's parabolic equation expression on the XY plane. Then, the initial parameter of the i-th sub-reflector is the initial point parameter of the parabolic equation expression of the i+1-th sub-reflector on the XY plane.

The coordinates of the initial point of the i+1 segmented sub-mirror:

x _i+1 ＝(i+1)L＝x' _i y _i+1 ＝y' _i (5)

The sectional line of the first sub-reflector on the X-Y plane passes through the end point A of the sectional line of the flat receiving surface on the X-Y plane, so there are:

X ₁ =L, Y ₁ =0

In the case of known concentration ratio, by substituting formula (6)(2)(1) into the general parabola formula 2P _i (y _i -b _i )=( _xi -a _i ) ² , the first paragraph can be obtained The parabolic equation of the mirror in the XY plane. Substituting formula (5) into the calculation of the parabolic equation of the first paragraph, the initial coordinates of the sub-reflector in the XY plane parabola are obtained, and similarly, the parabolic equation of each sub-reflector in the XY two-dimensional Cartesian coordinate system can be determined by successive iterations Expression, and the starting and ending coordinates ( _xi , y _i ) (x' _i , y' _i ) of all paraboloids in the XY two-dimensional Cartesian coordinate system to determine the installation position of the sub-mirror.

Advantages of the present invention compared with the prior art: as shown in Figure 4, the reflector profiles on the left and right sides of the traditional CPC concentrator are a complete parabola. Only one focal point is created on the plate receiving surface, at the endpoint of the shape line of the plate receiving surface. In the present invention, the traditional CPC profile is designed in sections, so that the energy flow density on the receiving surface of the plate is distributed in multiple focal lines, thereby greatly improving the uniformity of the energy flow density distribution on the receiving surface of the plate, and reducing the concentration of thermal stress on the receiving surface of the plate , prolong the service life of the device. The models of the traditional CPC solar concentrator and the segmented CPC solar concentrator with the same concentration ratio of 6 are respectively imported into the tracePro software for optical tracing simulation, and the energy flux density distribution on the receiving surface of the plate can be obtained. When the solar irradiance of each ray is 700W/m ² , the energy flux density distribution on the receiving surface of the two concentrator plates is shown in Figure 1. It can be seen from Figure ¹ that the energy flux density on the flat receiving surface of the traditional CPC concentrator presents a distribution trend of high on ^both sides and low in the middle. ×10 ⁸ W/m ² , the energy-flux density range is 5.82×10 ¹⁰ W/m ² ; while the energy-flux density on the flat receiving surface of the segmented CPC concentrator has an approximately sinusoidal distribution, and the energy-flux density near each focal point Roughly the same, about 1.25×10 ¹⁰ W/m ² , the minimum value is 5.25×10 ⁸ W/m ² , and the extreme difference is 1.1975×10 ¹⁰ W/m ² , so the energy flow on the receiving surface of the segmented CPC plate The density difference is much smaller than the receiving surface of the traditional CPC flat plate, which shows that under the same working conditions, the energy flux density distribution uniformity of the segmented CPC solar concentrator proposed by the present invention is much higher than that of the traditional CPC concentrator, thereby effectively improving the CPC concentrator. Optical device safety and economy.

The present invention will be described in detail below in conjunction with examples. Frame 2-1, compound parabolic reflector 2-2, flat receiving surface 2-3, incident surface 2-4, backing plate 2-5, glass cover plate 2-6;

Refer to Figure 2 for a structural schematic diagram of a segmented CPC solar collector with a concentration ratio of 6. The overall collector is composed of a frame 2-1, a flat panel receiver 2-3, and a compound parabolic reflector 2-2. As shown in Figure 1, the composite parabolic reflector 2-2 is placed inside the frame 2-1, and a glass cover plate 2-6 is added at the upper end of the frame 2-1 to reduce the convective heat transfer between the environment and the flat receiving surface; The parabolic reflector 2-2 adopts a uniform segmented design and includes multiple sub-reflectors, so that the parabolic focal lines of each sub-reflector are uniformly distributed on the flat receiving surface 2-3. All the light rays reflected by the compound parabolic reflector 2-2 are evenly distributed on the flat receiving surface 2-3 to achieve the effect of uniform energy flow density distribution on the flat receiving surface; the segments of the compound parabolic reflector 2-2 are sequentially connected in rows according to numbers , the end of the sub-reflector of the previous segment is connected with the initial segment of the sub-reflector of the rear segment to form a whole, and the initial segment of the whole body and the 2-3 segments of the flat receiving surface are fixed to each other, so as to maximize the stability of its placement.

As shown in Figure 3, an XY two-dimensional rectangular coordinate system is established, and the XY coordinate plane is perpendicular to the focal line of the parabolic reflection surface of each sub-reflector and the receiving surface of the flat-panel receiver. As shown in Figure 3, the O point is the origin, and the vertical is Y Axis, the horizontal is the X axis. Regardless of whether a tracking device is added, the incident light at noon is perpendicular to the receiving surface 2-3 of the flat panel, which is used as the analysis time of the concentrator. On the XY coordinate plane, the segmented CPC line is composed of five segments: AB, BC, CD, DE, and EF. The focal lines of the paraboloids of each sub-reflector are on the same plane, and the vertical axes of the paraboloids of each segment are vertical to each other. parallel. Now take the left of the Y axis as the positive direction, and number the sub-mirrors i in turn, and the AB section is the starting number 1. The abscissa and the ordinate of the initial position on the i-th sub-reflector are defined as X _i , respectively, so there are initial coordinates (X _i , Y _i ) of the _i -th sub-reflector. Initial conditions, AO=40, concentration ratio C=6, then the incident surface FF'=240, and the incident surface is segmented evenly, so the initial coordinates of the first segment are (20,0), and the initial abscissa coordinates of the subsequent segments x _{i+ 1} = x _i +20. Since the focal point is evenly distributed on the flat receiving surface 2-3, the focal point coordinates (-2, 0), (-6, 0), (-10, 0), (-14, 0), ( -18, 0). The vertical axes of the paraboloids of each sub-reflector are vertical and parallel to each other, so the abscissa of the apex of the parabola of the sub-reflectors is consistent with the abscissa of the focal point.

Assuming that the i-th sub-mirror 2-1 is expressed as 2P _i (Yb _i )=(Xa _i ) ² on the XY coordinate system, the parabolic profile equation of the i-th sub-mirror on the XY plane is given by the following formula Sure:

2P _i (y _i -b _i )＝( _xi -a _i ) ² (3)

The abscissa of the initial point of the i-th segmented sub-mirror:

x _i = iL (4)

The coordinates of the initial point of the i+1 segmented sub-mirror:

x _i+1 ＝(i+1)L＝x' _i y _i+1 ＝y' _i (5)

The initial point of the first segmented submirror is known:

x ₁ =L y ₁ =0 (6)

In the formula: a _i , b _i are the vertex parameters of the parabolic equation expression of the i-th sub-mirror on the XY plane.

x _i , y _i are the initial point parameters of the parabolic equation expression of the ith sub-mirror on the XY plane.

x' _i , y' _i are the parameters of the termination point of the i-th sub-mirror's parabolic equation expression on the XY plane, and are also the initial point parameters of the i+1th sub-reflector's parabolic equation expression on the XY plane.

C is the concentration ratio of the segmented parabolic concentrator;

P _i is the quasi-focal length of the i-th sub-mirror in the parabolic equation expression on the XY plane.

By substituting (6)(2)(1) into (3), the parabolic equation of the first sub-mirror on the XY plane can be obtained. Substituting formula (5) into the calculation of the parabolic equation of the first paragraph, the initial coordinates of the sub-reflector in the XY plane parabola are obtained, and similarly, the parabolic equation of each sub-reflector in the XY two-dimensional Cartesian coordinate system can be determined by successive iterations Expression, and the starting and ending coordinates ( _xi , y _i ) (x' _i , y' _i ) of all paraboloids in the XY two-dimensional Cartesian coordinate system to determine the installation position of the sub-mirror. The specific parameters of the example are shown in Table 1:

Table 1 Parameter table of each sub-reflector

initial point coordinates end point coordinates Vertex coordinates focus coordinates Quasi-focal length p_i first paragraph (20,0) (40, 29.090) (-2, -11) (-2, 0) twenty two second paragraph (40, 29.090) (60, 73.296) (-6, -12.667) (-6, 0) 25.334 third paragraph (60, 73.296) (80, 130.325) (-10, -14.068) (-10, 0) 28.136 fourth paragraph (80, 130.325) (100, 198.830) (-14, -15.181) (-14, 0) 30.362 fifth paragraph (100, 198.830) (120, 277.895) (-18, -16.189) (-18, 0) 32.378

The first equation: 44(y+11)=(x+2) ²

The second equation: 50.668(y+12.667)=(x+6) ²

The third equation: 56.272(y+14.068)=(x+10) ²

The fourth equation: 60.724(y+15.181)=(x+14) ²

The fifth paragraph equation: 64.756(y+16.189)=(x+18) ²

The above description is only a preferred embodiment of the present disclosure and an illustration of the applied technical principle. It should be understood by those skilled in the art that the scope of the invention involved in this disclosure is not limited to the technical solution formed by the specific combination of the above technical features, but also covers the technical solutions made by the above technical features without departing from the inventive concept. Other technical solutions formed by any combination of or equivalent features thereof. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this disclosure.

Claims (3)

1. A segmented CPC solar concentrator, comprising: the device comprises a frame (2-1), a compound parabolic reflector (2-2), a flat receiving surface (2-3) and an incidence surface (2-4);

the compound parabolic reflector (2-2) is fixed in the frame (2-1); the compound parabolic reflectors (2-2) are symmetrically arranged on two sides of the flat receiving surface (2-3);

the flat receiving surface (2-3) is a heat absorption surface of a flat light-gathering receiving body;

the compound parabolic reflector (2-2) is composed of a plurality of sections of sub reflectors, the sub reflectors are sequentially connected end to end, focal lines generated by the sub reflectors on the flat receiving surface (2-3) from bottom to top are sequentially and uniformly distributed from the middle to two sides, the focal lines of the sub reflectors are different in position and are parallel to each other.

2. A segmented CPC solar concentrator according to claim 1, characterized by that, the flat receiving surface (2-3) is provided with a backing plate (2-5) below, and the frame (2-1) is provided with a glass cover plate (2-6) on top.

3. A method of designing a segmented CPC solar concentrator, according to claim 1 or 2, comprising the steps of:

s1, determining the number of segments:

the ratio of the sectional parabolic condenser is given as C, namely the ratio of the area of the incident surface (2-4) to the area of the flat receiving surface (2-3) is C; the number of the sub-reflectors on each side of the flat receiving surface (2-3) is C-1;

s2, determining focal line arrangement:

each section of sub-reflector generates an independent focal line, the left side and the right side of the compound parabolic reflector (2-2) are symmetrical, the number of the focal lines is 2 (C-1), and the focal lines are uniformly distributed on the flat receiving surface (2-3); all the sub-reflectors on one side are sequentially connected end to end, and focal lines generated by all the sub-reflectors on the flat receiving surface (2-3) from bottom to top are sequentially and uniformly distributed from the middle to two sides;

s3, a section line equation of each paraboloid:

the width of a flat receiving surface (2-3) in the given sectional type condenser is 2L, sub reflectors of the compound parabolic reflector (2-2) are sequentially connected end to end, and an initial section is fixed at the side edge of the flat receiving surface (2-3); an X-Y two-dimensional rectangular coordinate system is established by taking the molded line midpoint of the flat plate receiving surface (2-3) as an origin, an X-Y coordinate plane is perpendicular to each sub-reflector focal line and the flat plate receiving surface (2-3), the intersection line of the X-Y coordinate plane and the flat plate receiving surface (2-3) is taken as an X axis, and the intersection line of the X-Y coordinate plane and the condenser symmetric plane is taken as a Y axis; the sub-reflectors connected with a flat receiving surface (2-3) are used as the starting point, the sub-reflectors are sequentially numbered i from bottom to top, the starting section is number 1, and the linear equation expression of the ith segmented sub-reflector on an X-Y coordinate system is assumed to be 2P _i (Y-b _i )＝(X-a _i ) ² The parabolic profile equation of the ith segmented sub-mirror in the X-Y plane is determined by:

2P _i (y _i -b _i )＝(x _i -a _i ) ² (3)

initial point abscissa of ith segmented sub-mirror:

x _i ＝iL (4)

initial point coordinates of the i +1 th segmented sub-reflector:

x _i+1 ＝(i+1)L＝x’ _i y _i+1 ＝y’ _i (5)

the first segmented sub-mirror has a known initial point:

x ₁ ＝L y ₁ ＝0 (6)

in the formula: a is _i ，b _i The vertex parameter of the parabolic equation expression of the ith subsection reflecting mirror on the X-Y plane is set;

x _i ，y _i initial point parameters of a parabolic equation expression of the ith segmented sub-reflector on an X-Y plane;

x’ _i ，y’ _i the end point parameter of the parabolic equation expression of the ith segmented sub-reflector on the X-Y plane is obtained; the initial point parameter of the parabolic equation expression of the i +1 th segmented sub-reflector on the X-Y plane is also provided;

P _i a quasi-focal length of a parabolic equation expression of the ith segmented sub-reflector on an X-Y plane;

substituting the equations (6), (2) and (1) into the equation (3) to obtain the parabolic equation of the 1 st segmented sub-reflector on the X-Y plane; substituting the formula (5) into the equation to calculate the 1 st segment of parabolic equation to obtain the initial coordinates of the lower segment of sub-reflectors in the X-Y plane parabola, and sequentially iterating the same to determine the parabolic equation expression of each sub-reflector in the X-Y two-dimensional rectangular coordinate system and the start and end coordinates (X) of the transversal lines of all the paraboloids in the X-Y two-dimensional rectangular coordinate system _i ，y _i )(x’ _i ，y’ _i ) Thereby determining the mounting position of the sub-mirror;

when the plurality of compound parabolic reflectors (2-2) are arranged, the starting position of the (i + 1) th parabolic reflector is positioned at the tail end position of the ith reflector.

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