CN114488367A

CN114488367A - Catadioptric nine-module uniform light-gathering Fresnel lens

Info

Publication number: CN114488367A
Application number: CN202210199664.XA
Authority: CN
Inventors: 戴强; 于津健; 张亚勋
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2022-03-02
Filing date: 2022-03-02
Publication date: 2022-05-13

Abstract

The invention provides a refraction and reflection type nine-module uniform light-gathering Fresnel lens, which adopts the design of a right-angled triangular tooth shape with equal tooth height and a central convex lens, wherein the inner ring of the Fresnel lens adopts refraction light gathering, and the outer ring realizes reflection light gathering by a total reflection principle and a high reflection film, so that the problem of limited caliber of the Fresnel lens is solved, the light spot distribution area of the lens on a receiving surface is enlarged, no focus with highly concentrated energy exists on the receiving surface, and the phenomenon of high energy of four corners in the design of the Fresnel lens is avoided. The right-angled triangle tooth shape of the catadioptric nine-module uniform light-gathering Fresnel lens avoids the phenomenon of energy concentration at the focus, and the energy is uniformly distributed on a certain area of the receiving surface; the design also reduces the processing difficulty, reduces the cost and improves the optical efficiency.

Description

Catadioptric nine-module uniform light-gathering Fresnel lens

Technical Field

The invention relates to a uniform light-gathering Fresnel lens, in particular to a catadioptric nine-module uniform light-gathering Fresnel lens.

Background

At present, the Fresnel lens is widely applied to the field of photovoltaic condensation, and is characterized in that redundant materials are removed on the basis of keeping the curvature radius of the surface of the lens, and each ring on the lens is equivalent to an independent equal-focal-length lens, so that the cost is reduced, and the Fresnel lens is suitable for non-imaging optical condensation. However, the conventional fresnel lens has a problem of poor light-condensing uniformity, which may cause local overheating on the surface of the receiver, resulting in damage to the device, and meanwhile, the conventional uniform light-condensing fresnel lens has some disadvantages, such as limited lens aperture and low optical efficiency.

For example, Wu Heli, Wuhan university of science and engineering, in "Fresnel solar concentrator research" a uniform plane corrugated inward Fresnel lens, which realizes uniform light concentration, but the design adopts the same mode as the traditional Fresnel lens, the surface annular belt adopts the design of equal annular distance, the annular distance is 1mm, and the tooth height is 0-0.8mm, and it can be known from looking up related documents that the processing precision of the traditional Fresnel lens in China is in the order of tens of microns, the relative error of the tooth height caused by insufficient processing precision is large, and the improvement of the optical efficiency is severely limited. The center of the Fresnel lens in the paper is a plane glass plate, on a receiving surface, because focal spots of the Fresnel lens are positioned on four corners, the energy of the four corners of the receiving surface is larger than the central energy of the receiving surface, and light spots formed by the plane glass plate do not greatly contribute to the improvement of the irradiance uniformity of the receiving surface. More importantly, the design does not solve the problem of limitation of the total reflection phenomenon on the size of the lens, the light condensation is realized only by means of refraction, and when the aperture of the Fresnel lens is gradually increased, the total reflection phenomenon inevitably occurs, so that the increase of the aperture of the lens and the increase of the optical efficiency are seriously limited.

Korean LEE sun JUN proposed a fresnel lens combination for collecting solar energy in patent No. KR20110041073A, which is obtained by layering a plurality of lattice-shaped square fresnel lenses. The lattice-shaped square Fresnel lens is formed by a pair of linear Fresnel lenses which are overlapped with each other in mutually orthogonal directions, and has a central square convex lens, and a pyramidal lattice-shaped lens element having a curvature is formed on the outer periphery of the square convex lens. Each pyramidal lens element acts as a separate lens to achieve focusing. The plurality of grid-shaped square Fresnel lenses are layered and superposed, so that the focal length of the lens complex is shortened, the manufacture of an ultra-large lens is facilitated, and the heat loss in the heat collection process is reduced. However, this design lacks a uniform light-condensing function, and in order to satisfy the light-condensing requirements, each pyramidal lattice lens element has a different curvature, and each lattice lens element needs to be processed by repeated movement of a tool, which causes difficulty in processing and a large loss in optical efficiency due to processing errors.

The Shanghai electric power college's Yindanyan et al in the design and analysis of a toric focal spot total internal reflection Fresnel lens proposes a toric focal spot total internal reflection Fresnel lens, which realizes light condensation by means of two total reflections, but considers the total reflection condition n sin i_NMore than or equal to 1, when polymethyl methacrylate (PMMA) is used, two times of total reflection can not occur when the ring belt inclination angle is less than 66 degrees, so that the generation of stray light is avoided. The design adopts a circular ring belt design, so that the improvement of uniformity is limited by the number of ring belts and the geometric concentration ratio of the Fresnel lens; meanwhile, the ring-surface focal spot total internal reflection Fresnel lens is circular, and the formed focal spot is a ring surface, so that the Fresnel lens is obviously not suitable for splicing a large solar array.

In addition, the above background art and other fresnel lenses generally have no anti-reflection film on their surfaces, and after practical simulation tests, the relative energy loss caused by reflection on the plane and refraction surface of the fresnel lens can reach 8% with and without the anti-reflection film, and thus, the reflection loss is not negligible.

Disclosure of Invention

The invention aims to solve the problem of uneven focusing of the conventional Fresnel lens, and provides a catadioptric nine-module uniform light-gathering Fresnel lens, which can effectively solve the problems of poor light-gathering uniformity and local overheating on the surface of a receiver of the Fresnel lens.

The purpose of the invention is realized as follows: the refraction and reflection type nine-module uniform light-gathering Fresnel lens is calculated through a non-imaging optical principle, the Fresnel lens is decomposed into nine parts, and the uniformity of the energy distribution of focusing light spots on the whole receiving surface is improved according to the superposition principle of a light field. The working surface of the Fresnel lens adopts the working modes of inner ring refraction type condensation and outer ring reflection condensation, so that the defect that light rays are totally reflected on a ring zone with a large ring number (counted from the center outwards) on the Fresnel lens after the aperture and the geometric condensation ratio of the Fresnel lens are gradually increased is overcome, and the uniform condensation Fresnel lens with parameters of any size, high geometric condensation ratio, low F number and the like can be obtained.

In order to achieve the purpose, the catadioptric nine-module uniform light-gathering Fresnel lens is formed by splicing a square convex lens, four parallel straight stripe rectangular Fresnel lenses and four arc stripe square Fresnel lenses; the lens surface of the parallel straight stripe Fresnel lens is recorded with parallel straight stripes from wide to narrow; the arc stripe square Fresnel lens surface is recorded with concentric quarter arc stripes from wide to narrow, each stripe is of an equal-thickness inclined plane structure, and the cross sections of the stripes are right-angled triangles; the refraction and reflection type nine-module uniform light-gathering Fresnel lens is characterized in that the short sides of four parallel straight stripe rectangular Fresnel lenses are tightly connected with a square convex lens, the long sides of the four parallel straight stripe rectangular Fresnel lenses are sequentially connected with four arc stripe square Fresnel lenses, the four arc stripe square Fresnel lenses are respectively connected with four corners of a central lens, and each stripe forms an annular zone;

fresnel lens surface zone satisfies n sin i at incident angle i_NThe girdle band with the relation of less than 1 is an inner ring which is designed based on the law of refraction, the plane where the bevel edge is positioned and other surfaces of the refraction and reflection type nine-module uniform light-gathering Fresnel lens are coated with antireflection films, and the incidence angle i satisfies n sin i_NThe annular zone with the relation of being more than or equal to 1 is an outer ring, the outer ring is designed based on the law of total reflection and the law of reflection, and on the basis of the design of an original anti-reflection film, a plane where a right-angle side of a right-angle triangular tooth form perpendicular to the surface of the Fresnel lens is located is plated with a high-reflection film.

Furthermore, the stripes of the arc stripe square Fresnel lens have a common circle center;

furthermore, the design of a right-angled triangular tooth shape with equal tooth height and a central convex lens is adopted, the inner ring of the Fresnel lens adopts refraction condensation, the outer ring realizes reflection condensation by depending on the total reflection principle and a high reflection film, and the energy concentration phenomenon at the focus is avoided by the right-angled triangular tooth shape.

Compared with the prior art, the invention has the beneficial effects that:

the refraction-reflection type nine-module uniform light-gathering Fresnel lens applied to photovoltaic power generation comprises a square convex lens, nine light spots are generated on a receiving surface by nine modules including four parallel straight stripe rectangular Fresnel lenses and four arc stripe square Fresnel lenses, the uniformity of the energy of the focused light spots is improved through light spot energy superposition, local hot spots formed by uneven light gathering of the traditional point light-gathering Fresnel lens are avoided, and the service life of a solar cell applied by the invention is prolonged; the modular design makes processing and combination easier, can be used to construct large-area solar concentrator arrays, and greatly improves efficiency. The Fresnel lens surface annular zone meets n sin i at an incidence angle i_NThe ring belt with the relation of less than 1 is an inner ring which is designed based on the refraction law and satisfies n sin i with the incidence angle i_NThe annular zone with the relation of more than or equal to 1 is an outer ring, the outer ring is designed based on the law of total reflection and the law of reflection, the defect that the lens caliber of the right-angled triangular toothed Fresnel lens is generally restricted by the phenomenon of total reflection is overcome, and flexible design is achieved. The invention adopts right-angled triangle tooth form, converts the focus with concentrated energy into light spots with certain area, simultaneously reduces the influence of process errors in the actual production process on the optical efficiency of the Fresnel lens and ensures the optical efficiency. In addition, the plane of the right-angle side of the annular belt of the Fresnel lens, which is vertical to the surface of the lens, is plated with the high-reflection film, and the plane of the inclined side and other surfaces of the refraction and reflection type nine-module uniform light-gathering Fresnel lens are plated with the anti-reflection films, so that the improvement of the optical efficiency and the light-gathering uniformity is facilitated.

Drawings

Fig. 1 is a front view of a catadioptric nine-module uniform condensing fresnel lens;

FIG. 2 is a schematic view of a square convex lens;

FIG. 3 is a surface zone distribution of eight Fresnel lens modules;

FIG. 4 is a parallel straight-striped rectangular Fresnel lens;

FIG. 5 is a schematic view of a circular-arc stripe square Fresnel lens;

FIG. 6 is a schematic diagram of a circular-arc stripe square Fresnel lens cut from a Fresnel lens having zone parameters meeting the design requirements of the circular-arc stripe square Fresnel lens;

fig. 7 shows the light path of a sunlight incident catadioptric nine-module uniform condensing fresnel lens.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the present invention is limited to the following examples, and all the technologies realized based on the above patent contents are included in the scope of the present invention.

The refraction and reflection type nine-module uniform light-gathering Fresnel lens is divided into nine modules, the center position of the refraction and reflection type nine-module uniform light-gathering Fresnel lens is a square convex lens, four sides of the convex lens are respectively connected with four parallel straight stripe rectangular Fresnel lenses, four corners of the convex lens are connected with four arc stripe square Fresnel lenses, and the whole structure is in central symmetry.

The central convex lens is positioned in the center of the whole lens system, each Fresnel lens is arranged around the central convex lens, and the parallel straight stripe rectangular Fresnel lenses and the circular arc stripe square Fresnel lenses are arranged at intervals.

The parallel straight stripe rectangular Fresnel lens is connected with the central convex lens, the width of the parallel straight stripe rectangular Fresnel lens is equal to the side length of the square convex lens, and the stripes are of an equal-thickness inclined plane structure.

And respectively determining the size and the curvature radius of the central square convex lens, the size, the tooth height, the thickness, the ring width and the ring number of the four parallel straight stripe rectangular Fresnel lenses, the size, the tooth height, the thickness, the ring width and the ring number of the four arc stripe square Fresnel lenses, the size and the position parameters of a receiving surface and the material parameters of nine modules according to optical design calculation.

The tooth-shaped sections of the two Fresnel lenses are right-angled triangles, a right-angled side of each right-angled triangle is perpendicular to the surface of each Fresnel lens, the tooth heights of the right-angled triangle are the same, and the inclined sides form refraction surfaces of incident light.

The refraction and reflection type nine-module uniform condensation Fresnel lens ring belt is in a right-angled triangle tooth shape, a plane where a right-angle edge of the ring belt perpendicular to the surface of the Fresnel lens is located is plated with a high-reflection film, and a plane where a bevel edge is located and other surfaces of the refraction and reflection type nine-module uniform condensation Fresnel lens are plated with antireflection films, so that the transmittance of the whole lens can be increased, and the limitation of the total reflection phenomenon of the outer ring belt of the Fresnel lens on the size of the Fresnel lens is broken through.

The design principle of the annular zone of the Fresnel lens with small working surface number (counted from the center outwards) is based on the refraction law to realize light condensation, so that light rays are focused on a receiving surface after passing through the Fresnel lens; the design principle of the annular zone with the larger number of working surface rings of the Fresnel lens realizes light condensation based on the law of total reflection and the law of reflection, light rays are focused on a receiving surface through primary total reflection, primary reflection and primary refraction after entering the Fresnel lens, the defect that the total reflection phenomenon restricts the aperture enlargement of the common Fresnel lens is converted into the advantage that the aperture of the Fresnel lens is enlarged by utilizing the total reflection principle, and the limitation of the total reflection phenomenon on the aperture of the Fresnel lens and the geometric condensation ratio is broken through.

The lens surface of the square Fresnel lens with the circular arc stripes is inscribed with concentric circular arcs with the circular distance from large to small, the stripes are of an equal tooth height inclined plane structure, and two sides of the stripes are connected with the rectangular Fresnel lens with the parallel straight stripes. Further, the stripes of the arc stripe square Fresnel lens have a common circle center.

Fig. 1 shows a front view of a catadioptric nine-module uniform condensing fresnel lens according to this embodiment. The Fresnel lens is formed by splicing a square convex lens 1, four parallel straight stripe rectangular Fresnel lenses 2 and four arc stripe square Fresnel lenses 3. The lens surface of the Fresnel lens 2 with the parallel straight stripes is recorded with the parallel straight stripes from wide to narrow; the arc stripe square Fresnel lens 3 is characterized in that concentric quarter arc stripes from wide to narrow are recorded on the surface, and the heights of the stripes are equal.

Nine even spotlight fresnel lens of module of catadioptric formula are by the minor face and the square convex lens zonulae occludens of four parallel straight stripe rectangle fresnel lens 2, and the long limit connects gradually with four circular arc stripe square fresnel lens 3, and four circular arc stripe square fresnel lens 3 meet with four angles of central lens respectively.

The refraction and reflection type nine-module uniform light-gathering Fresnel lens can be derived from the following formula:

the thickness of the central convex lens is consistent with the tooth height of the Fresnel lens, and is obtained by the geometrical relationship:

R²＝(R-h)²+r² (1)

wherein R is the curvature radius of the central convex lens, h is the thickness, and R is the half width of the central convex lens.

As shown in fig. 2, the spherical focal length formula of the center lens is as follows:

wherein n' is the ambient refractive index and n is the refractive index of the lens material. Therefore, the focal length of the lens is obtained, and further, the irradiance distribution of the catadioptric nine-module uniform light-gathering Fresnel lens on a receiving surface is determined.

As shown by the tooth-shaped section 4 of the right triangle with equal tooth height, the tooth-shaped section of each ring is in a right triangle. When n sin i_NWhen the thickness is less than or equal to 1, the annular belt of the Fresnel lens is designed based on the refraction principle, the plane of the inclined edge and other surfaces of the refraction and reflection type nine-module uniform light-gathering Fresnel lens are plated with anti-reflection films, and when n sin i_NWhen the reflection angle is larger than or equal to 1, the annular zone of the Fresnel lens is designed based on the total reflection principle and the reflection principle, and on the basis of the design of an original anti-reflection film, a plane where a right-angle side of a right-angle triangular tooth shape perpendicular to the surface of the Fresnel lens is located is plated with a high-reflection film, such as a light path diagram 7 of a Fresnel lens module.

Deducing a Fresnel lens ring zone design formula designed based on a refraction principle, and obtaining the parameters of each ring according to an optical formula and a geometric relation, wherein the parameters of each ring meet the following requirements:

n sin i_N＝n′sin i′_N (3)

β_N＝90°-i′_N+i_N (6)

wherein, a_NFor each ring width, i_NIs an incident angle of i'_NAngle of refraction, α_NThe included angle between the right-angle side and the hypotenuse of the right-angled triangle perpendicular to the plane of the Fresnel lens is beta_NIs the included angle between the refracted ray and the Fresnel lens plane, and N is the number of rings.

Deducing a Fresnel lens ring zone design formula designed on the basis of a total reflection principle and a reflection principle, and obtaining parameters of each ring according to an optical formula and a geometric relationship, wherein the parameters of each ring meet the following conditions:

n sin i_N＝n′sin i′_N (8)

i_N＝i”_N (9)

γ_N＝90°-i′_N+α_N (12)

wherein, γ_NThe included angle is formed by the refracted ray and a right-angle side of the right-angle triangle tooth shape, and the right-angle side is vertical to the surface of the Fresnel lens.

The formulas (1) to (13) are derived formulas related to the patent of the present invention, but the obtaining of the lens parameters is not limited to the above formulas, so as to achieve the purpose of uniform light condensation, and form a catadioptric nine-module uniform light condensation fresnel lens. The lens is not limited to the above-described embodiments, but can be extended to any embodiment that can implement uniform light collection.

As shown in fig. 7, the light path of the sunlight incident catadioptric nine-module uniform condensing fresnel lens is made of PMMA and other common materials, and the present embodiment can be designed and manufactured through the following steps:

the size of a refraction and reflection type nine-module uniform light-gathering Fresnel lens is determined, the size of a square convex lens is 10mm multiplied by 10mm, the size of 2 parallel straight stripe rectangular Fresnel lens is 10mm multiplied by 40mm, the size of 3 circular arc stripe square Fresnel lens is 40mm multiplied by 40mm, the whole size is 90mm multiplied by 90mm, the tooth height h is 0.4mm, the thickness is 1mm, the distance between a receiving surface and the lens is 89.8mm, and the size of the receiving surface is 10mm multiplied by 10 mm.

And calculating the light path of each ring of edge light rays according to the edge light ray principle and the design requirement of uniform surface light condensation. Further, parameters of each ring of the Fresnel lens are determined, and each ring parameter is derived based on the intersection of the marginal ray of each right-angled triangle section and the focus of the central convex lens, so that the Fresnel lens does not have a focus with highly concentrated energy.

The central square lens 1 in the catadioptric nine-module uniform condensing fresnel lens described in this embodiment may be cut from a common circular convex lens, a square is made in the common circular convex lens, four vertex angles of the square are located on the edges of the convex lens, and the square convex lens 1 is obtained by cutting, as shown in fig. 2.

The circular-arc-stripe square fresnel lens 3 described in this embodiment is obtained by cutting a fresnel lens whose girdle parameters meet the design requirements of the circular-arc-stripe square fresnel lens, as shown in fig. 6, a square is made in an equal-thickness inclined fresnel lens, four vertex angles of the square are located on the boundary of a circular equal-thickness inclined plane fresnel lens, the square fresnel lens is cut along a cutting line 7, and then the square fresnel lens is symmetrically divided into four modules along a central line, so as to ensure that the side length of the square fresnel lens is equal to the long side of the rectangular fresnel lens, as shown in fig. 5.

As shown in fig. 4, the parallel straight stripe rectangular fresnel lens 2 described in this embodiment ensures that the width of the parallel straight stripe rectangular fresnel lens 2 is equal to the side length of the central square convex lens 1, and the length is equal to the side length of the circular arc stripe square fresnel lens 3.

The surface zones of the eight fresnel lens modules are distributed as shown in fig. 3, and include an inner zone 6 and an outer zone 5.

In conclusion, the catadioptric nine-module uniform light-gathering Fresnel lens is designed, and square uniform light-gathering spots can be generated.

The refraction and reflection type nine-module uniform light-gathering Fresnel lens provided by the invention is designed by adopting a right-angled triangular tooth shape with equal tooth height and a central convex lens, the inner ring of the Fresnel lens adopts refraction light gathering, and the outer ring realizes reflection light gathering by virtue of a total reflection principle and a high reflection film, so that the problem of limited caliber of the Fresnel lens is solved, the light spot distribution area of the Fresnel lens on a receiving surface is enlarged, no focus with highly concentrated energy exists on the receiving surface, and the phenomenon of high energy of four corners in the Fresnel lens design is avoided. The right-angled triangle tooth shape of the catadioptric nine-module uniform light-gathering Fresnel lens avoids the phenomenon of energy concentration at the focus, and the energy is uniformly distributed on a certain area of the receiving surface; the design also reduces the processing difficulty, reduces the cost and improves the optical efficiency.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the technical scope of the present invention.

Claims

1. A refraction-reflection type nine-module uniform light-gathering Fresnel lens is characterized by being formed by splicing a square convex lens, four parallel straight stripe rectangular Fresnel lenses and four arc stripe square Fresnel lenses; the lens surface of the parallel straight stripe Fresnel lens is recorded with parallel straight stripes from wide to narrow; the arc stripe square Fresnel lens surface is recorded with concentric quarter arc stripes from wide to narrow, each stripe is of an equal-thickness inclined plane structure, and the cross sections of the stripes are right-angled triangles; the refraction and reflection type nine-module uniform light-gathering Fresnel lens is characterized in that the short sides of four parallel straight stripe rectangular Fresnel lenses are tightly connected with a square convex lens, the long sides of the four parallel straight stripe rectangular Fresnel lenses are sequentially connected with four arc stripe square Fresnel lenses, the four arc stripe square Fresnel lenses are respectively connected with four corners of a central lens, and each stripe forms an annular zone;

fresnel lens surface zone satisfies n sin i at incident angle i_N<The girdle band in relation 1 is an inner ring which is designed based on the law of refraction, the plane where the bevel edge is located and other surfaces of the refraction and reflection type nine-module uniform light-gathering Fresnel lens are plated with antireflection films, and the incidence angle i satisfies n sin i_NThe annular zone with the relation of being more than or equal to 1 is an outer ring, the outer ring is designed based on the law of total reflection and the law of reflection, and on the basis of the design of an original anti-reflection film, a plane where a right-angle side of a right-angle triangular tooth form perpendicular to the surface of the Fresnel lens is located is plated with a high-reflection film.

2. The catadioptric nine-module uniform concentration fresnel lens of claim 1, wherein the stripes of the circular arc stripe square fresnel lens have a common center.

3. The refraction-reflection type nine-module uniform light-gathering Fresnel lens according to claim 1, characterized in that the design of a right-angled triangular tooth profile with equal tooth height and a central convex lens is adopted, the inner ring of the Fresnel lens adopts refraction light gathering, the outer ring realizes reflection light gathering by means of a total reflection principle and a high reflection film, and the right-angled triangular tooth profile avoids the phenomenon of energy concentration at the focus.