Method and system for constructing reflective non-imaging solar concentrating system

Abstract

The invention discloses a method and a system for constructing a reflective non-imaging solar concentrating system. The method comprises the following steps of: determining a concentrating system structure and a target energy flux density distribution condition; determining the energy mapping relation between the condenser and the receiver; establishing the energy mapping relation between the reflecting surface and the receiving surface according to the geometrical optical reflection law; according to the to-be-designed energy flux density distribution condition of the receiving surface, determining a mapping relation between an incidence point of the incident light on the reflecting surface and an arrival point on the corresponding receiving surface; deducing a generatrix coordinate iterative formula of the condensing reflecting surface according to the energy mapping relation; coordinates of sampling points on the reflecting surface of the condensation system are calculated and fitted into a curve, and a condensation system reflecting surface model meeting the mapping relation is generated; and performing optical simulation and analysis on the established system model, and feeding back and optimizing the structure of the condensation system according to a simulation result. And the problem of non-uniform distribution of solar concentrating energy flow is solved while relatively high optical efficiency is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of solar energy utilization, and in particular to a reflective non-imaging solar energy concentrating system construction method and system. Background Art

[0002] Solar concentrating system is a key component for solar energy utilization. Currently, the four common commercial solar concentrating systems are tower, trough, dish and linear Fresnel solar concentrating and collecting systems. However, in many solar concentrating systems, there is a common problem of uneven distribution of solar concentrating energy flow. The uneven distribution of solar concentrating energy flow will cause the local temperature of the system receiver to be too high. In the CPV system, the uneven energy distribution will cause the local photocurrent effect of the photovoltaic cell to be different, resulting in current mismatch, which will lead to a significant reduction in the current of the entire photovoltaic cell array. At the same time, the fill factor will also be affected, causing the photovoltaic cell array to short-circuit or even burn, reducing the photoelectric conversion efficiency of the system; in the concentrating and collecting system, the uneven energy distribution will cause the receiver to form an uneven temperature field and thermal stress field distribution, and even cause the receiver to burn due to excessive temperature or thermal stress cracking.

[0003] In order to solve the problem of uneven distribution of solar energy flux, many scholars have conducted research in this area and proposed corresponding countermeasures, such as adding secondary focusing elements to the focusing system, optimizing the concentrator structure, improving the parabolic algorithm, etc. However, the improved concentrator spots are mostly still Gaussian distributed, and there are relatively few studies on improving the uniformity of the concentrated energy flux of reflective solar concentrators. Therefore, it is of great significance and value to propose a universal method that can effectively improve the energy flux density distribution of reflective solar concentrators. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for constructing a reflective non-imaging solar energy concentrating system in response to the above-mentioned problems currently existing.

[0005] The technical solution of the present invention is as follows:

[0006] A method for constructing a reflective non-imaging solar energy concentrating system comprises the following steps:

[0007] Confirm the design goals: determine the focusing system structure and target energy flux density distribution;

[0008] Determine the energy mapping relationship: According to the law of geometrical optics reflection, establish the energy mapping relationship between the reflecting surface and the receiving surface; according to the energy flux density distribution of the receiving surface to be designed, determine the mapping relationship between the incident point of the incident light on the reflecting surface and the corresponding arrival point on the receiving surface;

[0009] Determine the iterative formula of the generatrix coordinates: According to the energy mapping relationship and the reflection law, derive the iterative formula of the generatrix coordinates of the focusing reflection surface;

[0010] Calculate coordinates and fit the surface: According to the generatrix coordinate iteration formula, calculate the coordinates of the sampling points on the reflection surface of the focusing system, and fit them into a curve to generate a reflection surface model of the focusing system that satisfies the mapping relationship;

[0011] Simulation analysis and optimization: Perform optical simulation and analysis on the established system model, and optimize the focusing system structure based on the simulation results.

[0012] Furthermore, when the reflective non-imaging solar concentrator system adopts a circular flat-plate receiver, the goal is to obtain a uniform energy flow distribution, and the construction method of the circular flat-plate receiver RNC system includes:

[0013] Determine the design goal and determine whether to obtain uniform energy flux density distribution on the circular flat receiver;

[0014] The solar radiation incident on the opening of the concentrator's lighting surface is divided into N areas according to equal energy, and the area of ​​each area is equal, that is, the equal area method is used for division;

[0015] According to the division of the daylighting surface openings, the reflective curved surface is also divided into N areas; solar radiation is incident on the corresponding area of ​​the reflective surface, and each area reflects the solar radiation on it to the receiver absorption surface;

[0016] The receiver absorption surface is also divided into N concentric rings according to the equal area method; each small area on the reflection surface is mapped to a ring on the receiver absorption surface;

[0017] According to the expected energy flux distribution on the receiving absorption surface, the generatrix coordinates of the reflecting surface are determined iteratively;

[0018] The coordinates of each sampling point on the reflection surface are calculated iteratively according to the generatrix coordinate formula;

[0019] According to the sampling point coordinate data, the circular flat-panel receiver RNC system modeling and optical simulation are carried out, and ray tracing is performed to analyze the energy flux density distribution on the receiver absorption surface;

[0020] The system geometry is repeatedly modified and improved according to specific requirements of optical efficiency and energy flux density uniformity.

[0021] Further, the equal area method comprises the following steps:

[0022] The shape of the opening lighting surface of the reflective mirror is circular. The opening lighting surface is divided into equal-area areas, that is, the opening lighting surface is divided into concentric rings of equal area. The formula is as follows:

[0023]

[0024] Where k is the serial number of the divided equal-area regions, which is a value from 0 to n; S qk is the area of ​​the qkth ring on the reflector opening lighting surface; r qk is the outer radius of the qkth ring on the reflector opening lighting surface; D is the diameter of the circular flat receiver RNC system opening sampling surface, d is the diameter of the circular receiver RNC system receiver; r q0 and r qn They are and The calculation formula for the outer radius of the ring corresponding to each area is:

[0025]

[0026] Calculate the Q of each point on the opening lighting surface in turn 1 , Q 2 , …, Q k and Q n The radius value r corresponding to the point qk , and the opening surface Q in the two-dimensional coordinates k With the reflecting surface P k The corresponding horizontal coordinate values ​​are the same, so P can be determined k The horizontal coordinates of each point; Q 0 and P 0 The points are q 1 Area and p 1 The starting point of the area, the corresponding horizontal coordinate value on the two-dimensional coordinate is the same as r q0 The value of is the same as d;

[0027] Irradiation to P n The solar radiation in the area will be reflected to the receiver r n The area of ​​the concentric rings of equal area on the receiver is calculated as follows:

[0028]

[0029] Among them, r rk is the outer radius of the kth concentric ring divided on the receiver absorption surface, and the horizontal coordinate value of each point on the receiver is obtained.

[0030] Furthermore, the ordinate values ​​of the sampling points of the iterative formula for determining the generatrix coordinates are calculated by a broken line algorithm and a midpoint algorithm, and the broken line algorithm includes the following steps:

[0031] Find the first area p on the reflection surface 1 The first and last coordinate points of the area, namely P 0 and P 1 ;

[0032] The second area p 2 The starting point of the area is p 1 The end point of the zone P 1 , and so on, construct P k (x k ,y k ) and its adjacent point P k+1 (x k+1 ,y k+1 ) to obtain P k+1 point;

[0033] Incident on p 1 The light in the area reaches the first ring r of the receiving surface after reflection. 1 The coordinates of each point are not repeated, that is, P 1 (x 1 ,y 1 ) on the receiving surface is R 1 (X 1 ,Y 1 ) point, P k (x k ,y k ) on the receiving surface is R k (X k ,Y k )point;

[0034] Incident light L 1 P 1 The unit vector of is:

[0035] After P 1 The unit vector of the reflected light at a point is:

[0036] Perform normalization:

[0037]

[0038] According to the law of reflection:

[0039]

[0040] P 1 Normal vector N of the point 1 for:

[0041]

[0042] By the normal vector N 1 Ask for a little P 1 The slope of the tangent line is:

[0043]

[0044] When the incident light energy is divided finely, that is, when there are more sampling points on the reflection surface, 1 The intersection of the tangent line of a point and the adjacent sampling light can be approximated as P 2 Point, pass P 1 The slope of a point can be expressed as P 1 and P 2 The coordinates are expressed as:

[0045]

[0046] Calculate P 2 The vertical coordinate y 2 , deduce that any point P on the reflection surface k+1 The vertical coordinate y k+1 :

[0047]

[0048] On the reflection surface, any point P k+1 The vertical coordinate y k+1 The previous point P adjacent to it k , target point R on the absorption surface k and its horizontal coordinate x k+1 related; and p k+1 The initial point of the region is p k The end point of the area, and so on, can be deduced to obtain the coordinates of the sampling points designed for the entire reflection surface.

[0049] Furthermore, the midpoint algorithm includes:

[0050] p k The light in the area is reflected to the absorption surface R k In the area, p k The two endpoints of the region are Ⅰ and Ⅱ, the midpoint is Ⅲ, R, r k The two endpoints of the zone are Ⅳ and Ⅴ, the midpoint is Ⅵ, and the k Make auxiliary lines a and b at the midpoint III of the zone, where a is the vertical incident direction of sunlight and b is perpendicular to the line segment taken on the surface. Make a line segment parallel to the selected line segment on the surface through the midpoint VI of the absorption surface, intersecting a at point VII and b at point VIII.

[0051] According to the geometric relationship, the coordinates of each point have the following relationship:

[0052] x Ⅲ =x Ⅶ ;

[0053]

[0054] (x Ⅶ -x Ⅷ ) 2 +(yⅦ -y Ⅷ ) 2 +(x Ⅲ -x Ⅷ ) 2 +(y Ⅲ -y Ⅷ ) 2 =(y Ⅲ -y Ⅶ ) 2 ;

[0055] Combining the above formulas, we can get:

[0056]

[0057] Any area p on the reflecting surface k The ordinate y of the end point II of the zone Ⅱ With starting point Ⅰ, R on the absorption surface k The two endpoints IV and V of the region and their horizontal coordinates x Ⅱ Related, p (k+1) The initial point of the region is p k The end point of the area, and so on, the ordinate value of the sampling coordinate point on the entire reflection surface can be calculated.

[0058] The present application also includes a circular flat-panel receiver reflective non-imaging solar energy concentrating system, which is designed and constructed using a reflective non-imaging solar energy concentrating system construction method, including a receiver, a reflector, a rotating screw, a crank, a lock, a support bearing and a rotating handle. The diameter of the lighting surface opening is 500mm, the diameter of the circular flat-panel receiver is 100mm, and the system height is 223mm.

[0059] The present application also includes a cylindrical receiver reflective non-imaging solar energy concentrating system, which is designed and constructed using a reflective non-imaging solar energy concentrating system construction method, with a lighting surface opening diameter of 3000mm, a cylindrical receiver diameter of 250mm, a cylindrical receiver height of 500mm, and a width of 300mm at the connection between the reflector and the receiver; or a lighting surface opening diameter of 500mm, a cylindrical receiver diameter of 40mm, a cylindrical receiver height of 100mm, and a width of 50mm at the connection between the reflector and the receiver.

[0060] The present application also includes a special-shaped receiver reflective non-imaging solar energy concentrating system, which is designed and constructed using a reflective non-imaging solar energy concentrating system construction method, including a regular hexagonal RNC system, a diamond RNC system and an arbitrary shape RNC system.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] A reflective non-imaging solar concentrator system construction method and system, a reflective non-imaging solar concentrator system (Reflective Non-imaging Solar Concentrator, RNC) design method is proposed based on non-imaging optical theory, free surface design method and geometric optical theory, provides a specific design process and surface calculation method, and can design various types of non-imaging solar concentrators, including solar concentrator systems with uniform energy flow distribution, stepped distribution or other distribution types. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a flow chart of the design method of the reflective non-imaging solar concentrator system (RNC) of the present application.

[0064] Figure 2 This is an energy mapping diagram of the circular flat-plate receiver reflective non-imaging solar energy concentrating system of the present application.

[0065] Figure 3 This is a two-dimensional optical path diagram of the energy mapping area of ​​this application.

[0066] Figure 4 This is a schematic diagram of the equal area division of the opening lighting surface of this application.

[0067] Figure 5 This is a schematic diagram of the equal area division of the receiver absorption surface of this application.

[0068] Figure 6 This is a schematic diagram of the coordinate points of the broken line algorithm of this application.

[0069] Figure 7 This is the calculation principle diagram of the midpoint algorithm of this application.

[0070] Figure 8 This is a cloud diagram of solar radiation energy flow on the receiver absorption surface of this application.

[0071] Fig. 9 This is a solar radiation energy flow curve diagram on the central cross section of the receiver absorption surface of the present application.

[0072] Fig.10 This is a partial optical path diagram of the circular flat-panel receiver RNC system of the present application.

[0073] Fig.11 This is a partial optical path diagram of a conventional solar dish concentrator of this application.

[0074] Fig.12 This is a cloud diagram of solar radiation energy flow on the absorption surface of the circular flat-panel receiver RNC system of the present application.

[0075] Fig.13This is a cloud diagram of solar radiation energy flow of a conventional solar dish concentrating system of the present application.

[0076] Fig.14 This is a comparison chart of the optical performance of the circular flat-panel receiver RNC system of the present application and the traditional solar dish concentrating system.

[0077] Fig.15 This is a structural diagram of the cylindrical receiver RNC system of the present application.

[0078] Fig.16 This is the cylindrical receiver RNC system model of this application.

[0079] Fig.17 This is a schematic diagram of a regular hexagonal RNC system of the present application.

[0080] Fig.18 This is the spot diagram of the regular hexagonal RNC system of this application.

[0081] Fig.19 This is a schematic diagram of a diamond-shaped RNC system of the present application.

[0082] Fig. 20 This is the diamond-shaped RNC system spot diagram of this application.

[0083] Fig.21 This is a schematic diagram of an arbitrary-shaped RNC system of the present application.

[0084] Fig. 22 This is the light spot diagram of the arbitrary-shaped RNC system of this application.

[0085] Fig.23 The stepped energy flow density distribution system of this application Figure 1 .

[0086] Fig.24 The stepped energy flow density distribution system of this application Figure 2 .

[0087] Fig.25 This is a structural diagram of the experimental device of the circular flat-panel receiver RNC system of this application.

[0088] Fig.26 This is a physical picture of the circular flat-panel receiver RNC system of this application. DETAILED DESCRIPTION

[0089] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0090] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0091] See also Figure 1-14 , a method for constructing a reflective non-imaging solar concentrating system, such as Figure 1 As shown, the following steps are included:

[0092] Confirm the design goals: determine the focusing system structure and target energy flux density distribution;

[0093] Determine the energy mapping relationship: According to the law of geometrical optics reflection, establish the energy mapping relationship between the reflecting surface and the receiving surface; according to the energy flux density distribution of the receiving surface to be designed, determine the mapping relationship between the incident point of the incident light on the reflecting surface and the corresponding arrival point on the receiving surface;

[0094] Determine the iterative formula of the generatrix coordinates: According to the energy mapping relationship and the reflection law, derive the iterative formula of the generatrix coordinates of the focusing reflection surface;

[0095] Calculate coordinates and fit the surface: According to the generatrix coordinate iteration formula, calculate the coordinates of the sampling points on the reflection surface of the focusing system, and fit them into a curve to generate a reflection surface model of the focusing system that satisfies the mapping relationship;

[0096] Simulation analysis and optimization: Perform optical simulation and analysis on the established system model, and optimize the focusing system structure based on the simulation results.

[0097] The design of a reflective non-imaging solar concentrator (RNC) is an inverse process, that is, given the properties of the incident light source and the energy distribution on the absorption surface, a reflector is designed to achieve the corresponding energy distribution. There are two key points in this design: first, determine the energy mapping relationship between the reflective surface and the receiving surface. In the process of determining the energy mapping relationship, different energy mapping area division methods need to be adopted according to the actual situation; second, determine the iterative formula of the generatrix coordinates of the reflection surface and calculate the sampling point coordinates of the reflection surface.

[0098] If the reflective non-imaging solar concentrator system adopts a circular flat-plate receiver and aims to obtain uniform energy flow distribution, the construction method of the circular flat-plate receiver RNC system includes:

[0099] Determine the design goal and determine whether to obtain uniform energy flux density distribution on the circular flat receiver;

[0100] The solar radiation incident on the opening of the concentrator's lighting surface is divided into N areas according to equal energy, and the area of ​​each area is equal, that is, the equal area method is used for division;

[0101] According to the division of the daylighting surface openings, the reflective curved surface is also divided into N areas; solar radiation is incident on the corresponding area of ​​the reflective surface, and each area reflects the solar radiation on it to the receiver absorption surface;

[0102] The receiver absorption surface is also divided into N concentric rings according to the equal area method; each small area on the reflection surface is mapped to a ring on the receiver absorption surface;

[0103] According to the expected energy flux distribution on the receiving absorption surface, the generatrix coordinates of the reflecting surface are determined iteratively;

[0104] The coordinates of each sampling point on the reflection surface are calculated iteratively according to the generatrix coordinate formula;

[0105] According to the sampling point coordinate data, the circular flat-panel receiver RNC system modeling and optical simulation are carried out, and ray tracing is performed to analyze the energy flux density distribution on the receiver absorption surface;

[0106] The system geometry is repeatedly modified and improved according to specific requirements of optical efficiency and energy flux density uniformity.

[0107] The equal-area method includes the following steps:

[0108] The two-dimensional energy mapping relationship between the reflective surface and the absorbing surface of the circular flat-panel receiver RNC system is as follows: Figure 2 In order to describe the energy mapping relationship of the system, the two-dimensional optical path diagram is as follows Figure 3 shown.

[0109] The reflective surface of the RNC system is obtained by rotating a two-dimensional curve around the central axis. Therefore, the opening lighting surface of the reflective mirror is circular. The opening lighting surface is divided into equal-area areas, that is, the opening lighting surface is divided into concentric rings of equal area, such as Figure 4 As shown in the figure, the areas of the divided regions are equal, and the formula is as follows:

[0110]

[0111] Where k is the serial number of the divided equal-area regions, which is a value from 0 to n; S qk is the area of ​​the qkth ring on the reflector opening lighting surface; r qk is the outer radius of the qkth ring on the reflector opening lighting surface; D is the diameter of the circular flat receiver RNC system opening sampling surface, d is the diameter of the circular receiver RNC system receiver; r q0 and r qn They are and The calculation formula for the outer radius of the ring corresponding to each area is:

[0112]

[0113] The areas q divided by the opening lighting surface k The corresponding division is performed on the reflection surface, that is, Figure 3 Each p on the reflection surface shown k Area. Calculate each point Q on the opening lighting surface in turn. 1 , Q 2 , …, Q k and Q n The radius value r corresponding to the point qk , and the opening surface Q in the two-dimensional coordinates k With the reflecting surface P k The corresponding horizontal coordinate values ​​are the same, so P can be determined k The horizontal coordinates of each point; Q 0 and P 0 The points are q 1 Area and p 1 The starting point of the area, the corresponding horizontal coordinate value on the two-dimensional coordinate is the same as r q0 The value of is the same as d;

[0114] like Figure 5 As shown, irradiation to P n The solar radiation in the area will be reflected to the receiver r n The area of ​​the concentric rings of equal area on the receiver is calculated as follows:

[0115]

[0116] Among them, r rk is the outer radius of the kth concentric ring divided on the receiver absorption surface, and the horizontal coordinate value of each point on the receiver is obtained.

[0117] The ordinate values ​​of the sampling points of the iterative formula for determining the generatrix coordinates are calculated by a broken line algorithm and a midpoint algorithm. The broken line algorithm includes the following steps:

[0118] by Figure 3 Take the light path in as an example to find the first area p on the reflection surface 1The first and last coordinate points of the area, namely P 0 and P 1 ;

[0119] The second area p 2 The starting point of the area is p 1 The end point of the zone P 1 , and so on, construct P k (x k ,y k ) and its adjacent point y k+1 (x k+1 ,y k+1 ) to obtain P k+1 point;

[0120] The optical path diagram is as follows Figure 6 As shown, the incident 1 The light in the area reaches the first ring r of the receiving surface after reflection. 1 The coordinates of each point are not repeated, that is, P 1 (x 1 ,y 1 ) on the receiving surface is R 1 (X 1 ,Y 1 ) point, P k (x k ,y k ) on the receiving surface is R k (X k ,Y k )point;

[0121] Incident light L 1 P 1 The unit vector of is:

[0122] After P 1 The unit vector of the reflected light at a point is:

[0123] Perform normalization:

[0124]

[0125] According to the law of reflection:

[0126]

[0127] P 1 Normal vector N of the point 1 for:

[0128]

[0129] By the normal vector N1 Ask for a little P 1 The slope of the tangent line is:

[0130]

[0131] When the incident light energy is divided finely, that is, when there are more sampling points on the reflection surface, 1 The intersection of the tangent line of a point and the adjacent sampling light can be approximated as P 2 Point, pass P 1 The slope of a point can be expressed as P 1 and P 2 The coordinates are expressed as:

[0132]

[0133] Calculate P 2 The vertical coordinate y 2 , deduce that any point P on the reflection surface k+1 The vertical coordinate y k+1 :

[0134]

[0135] On the reflection surface, any point P k+1 The vertical coordinate y k+1 The previous point P adjacent to it k , target point R on the absorption surface k and its horizontal coordinate x k+1 related; and p k+1 The initial point of the region is p k The end point of the area, and so on, can be deduced to obtain the coordinates of the sampling points designed for the entire reflection surface.

[0136] The midpoint algorithm includes:

[0137] The calculation principle diagram is as follows Figure 7 As shown, p k The light in the area is reflected to the absorption surface R k In the area, p k The two endpoints of the region are Ⅰ and Ⅱ, the midpoint is Ⅲ, R, r k The two endpoints of the zone are Ⅳ and Ⅴ, the midpoint is Ⅵ, and the k Make auxiliary lines a and b at the midpoint III of the zone, where a is the vertical incident direction of sunlight and b is perpendicular to the line segment taken on the surface. Make a line segment parallel to the selected line segment on the surface through the midpoint VI of the absorption surface, intersecting a at point VII and b at point VIII.

[0138] According to the geometric relationship, the coordinates of each point have the following relationship:

[0139] x Ⅲ =x Ⅶ ;

[0140]

[0141] (x Ⅶ -x Ⅷ ) 2 +(y Ⅶ -y Ⅷ ) 2 +(x Ⅲ -x Ⅷ ) 2 +(y Ⅲ -y Ⅷ ) 2 =(y Ⅲ -y Ⅶ ) 2 ;

[0142] Combining the above formulas, we can get:

[0143]

[0144] Any area p on the reflecting surface k The ordinate y of the end point II of the zone Ⅱ With starting point Ⅰ, R on the absorption surface k The two endpoints IV and V of the region and their horizontal coordinates x Ⅱ Related, p (k+1) The initial point of the region is p k The end point of the area, and so on, the ordinate value of the sampling coordinate point on the entire reflection surface can be calculated.

[0145] Modeling analysis:

[0146] A circular flat-panel receiver RNC system with a lighting opening diameter of 1200mm, a receiver absorption surface diameter of 60mm, and a focal height of 600mm will be preliminarily designed. According to the mapping area division and surface design method, the coordinates of the sampling points on the entire two-dimensional reflection surface can be obtained. The concentrating reflector model is constructed using SolidWorks software, and the concentrating reflector model and the receiver model are imported into TracePro software. The ray tracing method is used to analyze them. The solar radiation energy flow cloud map on the receiver absorption surface of the system and the solar radiation energy flow curve on the central section of the receiver absorption surface are shown in the figure. Figure 8 and Fig. 9 According to the simulation results, under the ideal condition that the reflectivity of the reflector is 1, the absorptivity of the receiver is 1, and there is no error, the focusing system has an optical efficiency of 0.99334 and a flux density uniformity of 0.919, and the optical performance is excellent.

[0147] The solar energy concentrating system designed by adopting the design method of reflective non-imaging solar energy concentrating system has excellent optical performance.

[0148] Comparison between circular flat receiver RNC system and solar dish concentrator:

[0149] A circular flat-plate receiver RNC system with a lighting opening diameter of 1200mm, a receiver absorption surface diameter of 60mm, and a focal height of 600mm and a traditional solar dish concentrator were designed and optically simulated, and their optical performances were compared.

[0150] After the two sets of focusing systems are modeled, optical tracing simulation will be performed on the two sets of systems respectively. The properties and light source settings of the two sets of focusing systems are the same, and the properties are set to ideal focusing systems, that is, the reflectivity of the concentrator is set to 1, and the absorptivity of the receiver is set to 1. Through ray tracing simulation, the local light path diagram is as follows Fig.10 and 11 As shown in the figure, the concentrator of the circular flat-panel receiver RNC system can evenly reflect light onto the entire absorption surface; the concentrator of the traditional solar dish concentrating system reflects light to the midpoint of the absorption surface, that is, the focus of the concentrating system. Fig.12 and 13 The following are cloud diagrams of solar radiation energy flow on the absorption surface of the two sets of concentrating system receivers. It can be seen from the figure that the solar radiation received by the circular flat-plate receiver RNC system is distributed on the entire absorption surface, while the solar radiation received by the traditional solar dish concentrating system is concentrated at the focus.

[0151] Fig.14 This is a comparison chart of the optical performance of the circular flat-panel receiver RNC system and the traditional solar dish concentrator system. It can be seen from the figure that the optical efficiency of the circular flat-panel receiver RNC system is only 0.004 lower than that of the traditional solar dish concentrator system, and the two are similar; however, the uniformity of the concentrated energy flux density of the two is very different. The uniformity of the concentrated energy flux density of the circular flat-panel receiver RNC system is about 0.919, while that of the traditional solar dish concentrator system is only 0.003. In summary, compared with the traditional solar dish concentrator system, the optical efficiency of the circular flat-panel receiver RNC system with the same geometric structure parameters is similar, but the energy flux density uniformity of the circular flat-panel receiver RNC system is much higher than that of the traditional solar dish concentrator system.

[0152] In addition, the design method of reflective non-imaging solar concentrating system is universal and can be used to design various systems, such as cylindrical receiver RNC system, special-shaped RNC system, stepped energy flow distribution RNC system, etc.

[0153] In order to verify the accuracy of the design method of reflective non-imaging solar concentrator system, a circular flat-plate receiver reflective non-imaging solar concentrator experimental system was designed and constructed using a reflective non-imaging solar concentrator system construction method. Fig.25 and Fig.26 As shown, it includes a receiver, a reflector, a rotating screw, a crank handle, a lock, a support bearing and a rotating handle. The diameter of the lighting surface opening is 500mm, the diameter of the circular flat plate receiver is 100mm, and the system height is 223mm.

[0154] In the whole experimental system, the positions of the reflector and the receiver are fixed, and the sun is tracked by a rotating device, and the energy flux density on the absorption surface of the receiver is measured by an energy flux density measuring device. After many experimental measurements, when the installation error (10mm) and operation error of the experimental system are large, the system can still maintain good optical performance, with energy flux density uniformity above 0.666 and optical efficiency above 0.730.

[0155] A cylindrical receiver reflective non-imaging solar energy concentrating system is designed and constructed using a reflective non-imaging solar energy concentrating system construction method, such as Fig.15 and Fig.16 As shown in the figure, according to the simulation results of tracepro software, the cylindrical receiver RNC systems with different geometric structures have excellent optical performance. For example, the cylindrical receiver RNC system with a lighting surface opening diameter of 3000mm, a cylindrical receiver diameter of 250mm, a cylindrical receiver height of 500mm, and a width of 300mm at the connection between the reflector and the receiver has an optical efficiency of 0.980 and an energy flux density uniformity of 0.988; the cylindrical receiver RNC system with a lighting surface opening diameter of 500mm, a cylindrical receiver diameter of 40mm, a cylindrical receiver height of 100mm, and a width of 50mm at the connection between the reflector and the receiver has an optical efficiency of 0.980 and an energy flux density uniformity of 0.947.

[0156] like Fig.15 As shown, P L is the opening diameter of the reflector lighting opening, R L is the diameter of the cylindrical receiver, R G is the height of the cylindrical receiver, K L is the width of the connection between the reflector and the receiver. The concentrator is a rotationally symmetrical structure, so when designing it, you only need to design its two-dimensional outline, and then rotate it through the symmetry axis to obtain its three-dimensional solid model.

[0157] A special-shaped receiver reflective non-imaging solar concentrator system is designed and constructed using a reflective non-imaging solar concentrator system construction method, including a regular hexagonal RNC system, a diamond RNC system and an arbitrary shape RNC system. Fig.17 , Fig.18 , Fig.19 , Fig. 20 , Fig.21 and Fig. 22 As shown, it is a special-shaped RNC system modified from the circular flat-panel receiver RNC system, and the uniformity of the energy flux density of the light spot is still above 93%.

[0158] like Fig.23 and Fig.24 The light spots of different stepped energy flux density distribution systems designed by RNC design method are designed. When designing the system, the energy mapping relationship is designed according to the energy flux distribution requirements, and the required stepped energy flux density distribution system is obtained.

[0159] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for constructing a reflective non-imaging solar energy concentrating system, characterized in that: The following steps are involved: Confirm the design goals: determine the focusing system structure and target energy flux density distribution; Determine the energy mapping relationship: According to the law of geometrical optics reflection, establish the energy mapping relationship between the reflecting surface and the receiving surface; according to the energy flux density distribution of the receiving surface to be designed, determine the mapping relationship between the incident point of the incident light on the reflecting surface and the corresponding arrival point on the receiving surface; Determine the iterative formula of the generatrix coordinates: According to the energy mapping relationship and the reflection law, derive the iterative formula of the generatrix coordinates of the focusing reflection surface; Calculate coordinates and fit the surface: According to the generatrix coordinate iteration formula, calculate the coordinates of the sampling points on the reflection surface of the focusing system, and fit them into a curve to generate a reflection surface model of the focusing system that satisfies the mapping relationship; Simulation analysis and optimization: Perform optical simulation and analysis on the established system model, and optimize the focusing system structure based on the simulation results.

2. A method for constructing a reflective non-imaging solar energy concentrating system according to claim 1, characterized in that: When the reflective non-imaging solar energy concentrating system adopts a circular flat-plate receiver, the circular flat-plate receiver RNC system construction method includes: Determine the design goal and determine whether to obtain uniform energy flux density distribution on the circular flat receiver; The solar radiation incident on the opening of the concentrator's lighting surface is divided into N areas according to equal energy, and the area of ​​each area is equal, that is, the equal area method is used for division; According to the division of the daylighting surface openings, the reflective curved surface is also divided into N areas; solar radiation is incident on the corresponding area of ​​the reflective surface, and each area reflects the solar radiation on it to the receiver absorption surface; The receiver absorption surface is also divided into N concentric rings according to the equal area method; each small area on the reflection surface is mapped to a ring on the receiver absorption surface; According to the expected energy flux distribution on the receiving absorption surface, the generatrix coordinates of the reflecting surface are determined iteratively; The coordinates of each sampling point on the reflection surface are calculated iteratively according to the generatrix coordinate formula; According to the sampling point coordinate data, the circular flat-panel receiver RNC system modeling and optical simulation are carried out, and ray tracing is performed to analyze the energy flux density distribution on the receiver absorption surface; The system geometry is repeatedly modified and improved according to specific requirements of optical efficiency and energy flux density uniformity.

3. The method for constructing a reflective non-imaging solar energy concentrating system according to claim 2, characterized in that: The equal area method comprises the following steps: The shape of the opening lighting surface of the reflective mirror is circular. The opening lighting surface is divided into equal-area areas, that is, the opening lighting surface is divided into concentric rings of equal area. The formula is as follows: Where k is the serial number of the divided equal-area regions, which is a value from 0 to n; Sqk is the area of ​​the qkth ring on the reflector opening lighting surface; r qk is the outer radius of the qkth ring on the reflector opening lighting surface; D is the diameter of the circular flat receiver RNC system opening lighting surface, d is the diameter of the circular receiver RNC system receiver; r q0 and r qn They are and The calculation formula for the outer radius of the ring corresponding to each area is: Calculate the points Q1, Q2, ..., Q on the opening lighting surface in turn. k and Q n The radius value r corresponding to the point qk , and the opening surface Q in the two-dimensional coordinates k With the reflecting surface P k The corresponding horizontal coordinate values ​​are the same, so P can be determined k The horizontal coordinates of each point; Q0 and P0 are the starting points of the q1 area and p1 area respectively, and the corresponding horizontal coordinate values ​​on the two-dimensional coordinates are the same as r q0 The value of is the same as d; Irradiation to P n The solar radiation in the area will be reflected to the receiver r n The area of ​​the concentric rings of equal area on the receiver is calculated as follows: Among them, r rk is the outer radius of the kth concentric ring divided on the receiver absorption surface, and the horizontal coordinate value of each point on the receiver is obtained.

4. The method for constructing a reflective non-imaging solar energy concentrating system according to claim 3, characterized in that: The ordinate values ​​of the sampling points of the iterative formula for determining the generatrix coordinates are calculated by a broken line algorithm and a midpoint algorithm, and the broken line algorithm includes the following steps: Find the first and last coordinate points of the first area p1 on the reflection surface, namely P0 and P1; The starting point of the second area p2 is the end point P1 of the p1 area, and so on. k (x k ,y k ) and its adjacent point P k+1 (x k+1 ,y k+1 ) to obtain P k+1 point; The light incident into the p1 region reaches the first ring r1 of the receiving surface after reflection, and the coordinates of each point are not repeated, that is, the coordinates of the reflected light of point P1 (x1, y1) on the receiving surface are point R1 (X1, Y1), P k (x k ,y k The coordinate of the reflected light from point ) on the receiving surface is R k (X k , Y k )point; The unit vector of the incident light ray L1P1 is: The unit vector of the reflected light passing through point P1 is: Perform normalization: According to the law of reflection: The normal vector N1 of point P1 is: The slope of the tangent line through point P1 is obtained from the normal vector N1: When the energy of the incident light is divided into finer parts, that is, when there are more sampling points on the reflection surface, the intersection of the tangent line through point P1 and the adjacent sampling light can be approximated as point P2, and the slope through point P1 can be expressed by the coordinates of P1 and P2: Calculate the ordinate y2 of P2 and deduce the value of any point P on the reflection surface k+1 The vertical coordinate y k+1 : On the reflection surface, any point P k+1 The vertical coordinate y k+1 The previous point P adjacent to it k , target point R on the absorption surface k and its horizontal coordinate x k+1 related; and p k+1 The initial point of the region is p k The end point of the area, and so on, can be deduced to obtain the coordinates of the sampling points designed for the entire reflection surface.

5. A method for constructing a reflective non-imaging solar energy concentrating system according to claim 4, characterized in that: The midpoint algorithm includes: p k The light in the area is reflected to the absorption surface R k In the area, p k The two endpoints of the region are I and II, the midpoint is III, R, r k The two endpoints of the region are IV and V, the midpoint is VI, and the k Make auxiliary lines a and b at the midpoint III of the area, where a is the vertical incident direction of sunlight and b is perpendicular to the line segment taken on the surface. Make a line segment parallel to the selected line segment on the surface through the midpoint VI of the absorption surface, intersecting a at point VII and b at point VIII. According to the geometric relationship, the coordinates of each point have the following relationship: x III =x VII ; (x VII -x VIII ) 2 +(and VII -and VIII ) 2 +(x III -x VIII ) 2 +(and III -and VIII ) 2 (and III -and VII ) 2 ; Combining the above formulas, we can get: Any area p on the reflecting surface k The ordinate y of the end point of zone II II With starting point I, absorbing surface R k The two endpoints IV and V of the region and its horizontal coordinate x II Related, p (k+1) The initial point of the region is p k The end point of the area, and so on, the ordinate value of the sampling coordinate point on the entire reflection surface can be calculated.

6. A circular flat-plate receiver reflective non-imaging solar concentrating system, characterized in that: The reflective non-imaging solar energy concentrating system is designed and constructed by using the construction method of any one of claims 1 to 5, including a receiver, a reflector, a rotating screw, a crank, a lock, a support bearing and a rotating handle, the diameter of the lighting surface opening is 500 mm, the diameter of the circular flat-panel receiver is 100 mm, and the system height is 223 mm.

7. A cylindrical receiver reflective non-imaging solar concentrating system, characterized in that: A reflective non-imaging solar energy concentrating system is designed and constructed by adopting a construction method of a reflective non-imaging solar energy concentrating system as described in any one of claims 1 to 5, wherein the diameter of the lighting surface opening is 3000mm, the diameter of the cylindrical receiver is 250mm, the height of the cylindrical receiver is 500mm, and the width of the connection between the reflector and the receiver is 300mm; or the diameter of the lighting surface opening is 500mm, the diameter of the cylindrical receiver is 40mm, the height of the cylindrical receiver is 100mm, and the width of the connection between the reflector and the receiver is 50mm.

8. A reflective non-imaging solar energy concentrating system with a special-shaped receiver, characterized in that: The reflective non-imaging solar energy concentrating system is designed and constructed by using a reflective non-imaging solar energy concentrating system construction method as described in any one of claims 1 to 5, including a regular hexagonal RNC system, a diamond RNC system and an arbitrary shape RNC system.

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