CN112462513B - Design method of combined paraboloid type solar condenser - Google Patents
Design method of combined paraboloid type solar condenser Download PDFInfo
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Abstract
The invention discloses a design method of a combined paraboloid type solar condenser, which comprises the following steps of firstly, determining optical and operating parameters of the condenser; then, setting the area of a light outlet according to requirements, and setting the value of the light outlet by taking the light concentration power obtained at the light outlet when the sunlight is incident vertically to the light inlet as a design target parameter; then, determining the combination of geometric parameters of the condenser, and establishing a geometric model of a design scheme under each combination; then, simulating the solar energy gathering process in each scheme to obtain corresponding gathering power; finally, selecting a scheme meeting the design requirement, and selecting the scheme with the maximum receiving half angle as a final scheme; and if the scheme meeting the requirements cannot be obtained under the current geometric parameter combination, automatically adjusting the geometric parameter combination, and redesigning until the scheme meeting the requirements is obtained. The geometric design and model construction, optical modeling and performance evaluation of the combined parabolic condenser can be quickly and accurately carried out, and the automatic design of the condenser is realized.
Description
Technical Field
The invention relates to the technical field of light-gathering solar energy utilization, in particular to a design method of a combined paraboloid type solar light gathering device.
Background
Since the 19 th century, fossil energy, mainly coal, oil, and natural gas, has gradually become the mainstay of world energy. With the rapid development of economic society, fossil energy used by human beings is increasing. However, the large use of fossil energy causes increasingly serious environmental problems and a large waste of resources, and the fossil energy is also eventually exhausted. Therefore, the development and utilization of renewable energy represented by solar energy has become a necessary choice for the development of energy in the world.
Among the existing solar energy utilization technologies, the concentrated solar energy utilization technology represented by the concentrated solar energy thermal utilization, the concentrated photovoltaic power generation and the concentrated photo-thermal power generation technology is a solar energy utilization technology which is in a rapid development stage at present. In the light-concentrating solar energy utilization technology, a light concentrator represented by a combined parabolic solar light concentrator is a key device for realizing solar energy concentration.
The typical combined paraboloid type solar concentrator is a whole formed by seamlessly combining 6 partial surfaces of a hexagonal compound paraboloid with a hexagonal cross section and 6 partial surfaces of a revolution surface compound paraboloid with a circular cross section, and the symmetry axes of the two compound paraboloids are overlapped and form the symmetry axis of the concentrator. It can be seen that the combined parabolic solar concentrator is a solar concentrating device with 12 complex curved surfaces. The design of the combined parabolic solar condenser relates to a complex curved surface geometric structure of a reflecting surface of the condenser, a complex propagation and collection process of multiple non-ideal reflection and absorption of solar radiant energy in the condenser and a strong non-imaging condensation characteristic of the condenser, so that the existing design method is difficult to quickly, accurately and conveniently design a reasonable geometric configuration design scheme of the combined parabolic condenser, and simultaneously is difficult to accurately evaluate the solar energy collection performance of the designed geometric configuration design scheme of the condenser, thereby further leading to the failure of realizing automatic, quick and low-cost design. In view of the above, there is a need to develop an automatic and fast design method capable of quickly, accurately and conveniently designing the geometric configuration of the combined parabolic concentrator and evaluating the solar energy concentrating performance of the combined parabolic concentrator.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a design method of a combined parabolic solar concentrator, which can be used for quickly, accurately and conveniently designing and constructing a geometric model of the combined parabolic concentrator, constructing an optical performance simulation calculation model and evaluating solar energy concentration performance, and realizing automatic and rapid design of the combined parabolic solar concentrator.
In order to achieve the above purpose, the technical scheme adopted by the invention comprises the following steps:
1) determining design optical parameters and design operation parameters of a condenser to be designed, wherein the design optical parameters comprise the specular reflectivity rho and the profile error sigma of a reflecting surface of the condenser, and the design operation parameters comprise the direct solar radiation intensity Id；
2) Determining the area S of the light outlet of a condenser2And calculating half a of the width of the opposite side of the hexagonal light outlet of the hexagonal compound paraboloid according to the following formula2：
3) Determining design target parameters of the condenser: the design target parameter includes the solar power Q concentrated at the exit of the concentrator under the condition that sunlight is incident perpendicular to the plane of the entrancereq(ii) a Establishing a right-hand rectangular coordinate system xyz, wherein the z axis is overlapped with the symmetry axis of the condenser, the positive direction of the z axis points to the center of the light inlet from the center of the light outlet of the condenser, and the origin o is positioned at the center of the light outlet of the condenser; defining an azimuth angle beta in an xy plane, and rotating anticlockwise to be positive by taking the positive direction of the y axis as 0 degrees;
4) determining the range and parameter combination of geometric structure parameters of the hexagonal compound paraboloid, wherein the geometric structure parameters comprise: hexagonal composite paraboloid half receiving angle theta1,iAnd half width a of opposite sides of the hexagonal light inlet1,j(ii) a Will theta1,iIs limited within (5 degrees, 30 degrees) and theta1,iIs set to (N)θ-1) species; a is to1,jIs limited to (a)2,a2/sinθ1,i) In which a is1,jIs set to (N)a-1) is NθAnd NaSelecting an initial value;
at the ith value, θ1,iThe following values are taken:
under the j value, a1,jThe following values are taken:
at different values of i and j, θ1,iAnd a1,jIs combined with (N)θ-1)·(Na-1) species;
5) at each theta separately1,iAnd a1,jUnder the value combination, establishing a geometric model of the condenser;
6) at each theta separately1,iAnd a1,jUnder the value combination, the propagation process of solar radiation energy in the condenser is simulated and calculated: establishing an optical model aiming at the geometric model of the condenser, and calculating each theta by adopting an optical simulation method1,iAnd a1,jAggregate under value combination toSolar power Q on light outletdesign,ij；
7) Respectively mixing each kind of theta1,iAnd a1,jSolar power Q collected to light outlet and obtained by calculation under combinationdesign,ijAnd design target parameter QreqAnd comparing, and judging whether the design requirement is met by adopting the following formula:
if at all (N)θ-1)·(Na-1) theta1,iAnd a1,jIf the value combination does not meet the design requirement of the formula, firstly adjusting NθAnd NaThe numerical value is returned to the step 4) to be calculated again until the design requirement of the formula is met, and all the theta meeting the design requirement are recorded1,iAnd a1,jCombining values;
8) comparing and calculating all theta meeting the design requirement1,iSelecting the maximum theta1,iThe corresponding design is the final design result.
Further, the solar power Q collected at the light outlet of the condenser in the step 3) under the condition that the sunlight is incident perpendicular to the plane of the light inletreqSatisfies the following formula:
wherein ρ is a specular reflectivity of the reflecting surface; σ is the profile error of the reflecting surface, rad; i isdW.m. direct solar radiation intensity-2。
Further, N in the step 4)θAnd NaAre set to 25 and 50, respectively.
Further, the step 5) of establishing the geometric model comprises the following steps:
5.1) in the yz plane according to the formula2≤y≤a1,jThe first mirror profile is plotted within:
sin2θ1,i·z2+[2(y+a2)·sinθ1,i-4a2(1+sinθ1,i)]cosθ1,i·z +[(y+a2)2cos2θ1,i-4a2(1+sinθ1,i)(-ysinθ1,i+a2)]＝0
5.2) calculating the distance hij between the light inlet plane and the light outlet plane of the condenser by adopting the following formula:
5.3) designing the geometric parameters of the compound paraboloid of the revolution surface, and calculating the radius r of the light inlet of the compound paraboloid of the revolution surface by adopting the following formula1,j：
r1,j＝a1,j/cos30°
The radius r of the light outlet of the compound paraboloid of the revolution surface is calculated by adopting the following formula2：
r2＝a2/cos10°
Calculating the semi-receiving angle theta of the compound paraboloid of the revolution surface by adopting the following formula2,ij：
[(r1,j+r2)cosθ2,ij+hijsinθ2,ij]2＝4r2(1+sinθ2,ij)(-r1,jsinθ2,ij+hijcosθ2,ij+r2)
5.4) in the yz plane by the formula r2≤y≤r1,jA second mirror profile is plotted within:
sin2θ2,ij·z2+[2(y+r2)·sinθ2,ij-4r2(1+sinθ2,ij)]cosθ2,ij·z +[(y+r2)2cos2θ2,ij-4r2(1+sinθ2,ij)(-ysinθ2,ij+r2)]＝0
5.5) respectively stretching the first mirror surface molded line for 0.5r along the positive and negative directions of the x axis1,jForming a paraboloid; placing the surface in its original positionThe number of the paraboloids is 6, and 5 parts of the paraboloids are respectively rotated by 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees around the z axis, so that 6 paraboloids which are rotationally symmetrically arranged around the z axis are obtained; then, firstly, the intersection line of any two adjacent paraboloids is obtained, and each paraboloid is divided into two parts of curved surfaces by taking the intersection line as a dividing line; then, a radius (r) is drawn on the plane where z is 02+a2The/cos 30) -2 circular ring judges whether the two parts of curved surfaces divided by each paraboloid intersect with the circular ring; then, the part of the two parts of curved surfaces divided by each paraboloid, which are not intersected with the circular ring, is reserved, and the part of the two parts of curved surfaces divided by each paraboloid, which are intersected with the circular ring, is discarded; finally, 6 partial curved surfaces reserved by the 6 paraboloids enclose a hexagonal compound paraboloid with a hexagonal xy section;
5.6) rotating the second mirror surface profile by 360 degrees around the z axis to form a revolution surface three-dimensional compound paraboloid;
5.7) solving 12 arc-shaped intersecting lines at the intersection of the hexagonal compound paraboloid and the revolution surface compound paraboloid, and respectively dividing the hexagonal compound paraboloid and the revolution surface compound paraboloid into different curved surfaces by taking the intersecting lines as dividing lines; then, the 6 parabolic curved surfaces at the azimuth angles beta of 0 °, 60 °, 120 °, 180 °, 240 ° and 300 ° divided by the hexagonal compound paraboloid are retained, and the 6 parabolic curved surfaces at the azimuth angles beta of 30 °, 90 °, 150 °, 210 °, 270 ° and 330 ° divided by the revolution surface compound paraboloid are retained, so as to form a combined parabolic solar concentrator formed by combining 12 parabolic curved surfaces.
Further, the step 6) of simulating and calculating the propagation process of the solar radiation energy in the concentrator comprises the following steps:
6.1) dividing the reflecting surface of the combined parabolic solar concentrator into a finite number of continuous and non-overlapping planar triangular meshes;
6.2) regarding the solar energy vertically incident to the hexagonal light inlet of the condenser as NinThe strips are uniformly projected to light rays with the same power on the light inlet;
6.3) judging whether the light rays entering the light inlet of the condenser hit any one plane triangular grid on the reflecting surface of the condenser; if there is a crossing point between the light and a triangle mesh, then the following formula is used to randomly determine whether the light will be reflected by the reflection surface at the triangle mesh:
if the light is reflected, calculating according to Fresnel reflection law to obtain reflection vector of the light on the reflection surface at the triangular mesh
Radial random deflection angle phi of actual normal vector of triangular mesh relative to ideal normal vector of triangular mesh plane1And random declination angle gamma in circumferential direction1Can be generated using the following formula:
in the formula, λ1、λ2And λ3Are mutually independent random numbers which are uniformly distributed in the interval of 0 to 1;
6.4) judging whether the light rays which are reflected once or for many times by the reflecting surface after entering the light inlet of the condenser have intersection points with the light inlet and the light outlet of the condenser; if it has an intersection point with the light outlet of the condenser, the number N of the light hitting the light outlet is recordedout(ii) a If the intersection point exists between the light source and the light inlet of the condenser, the light is lost from the light inlet and is not collected to the light outlet, and then the propagation process of the next light incident to the light inlet is solved; if the light ray enters the light inlet of the condenser and does not hit any plane triangular grid on the reflecting surface of the condenser after entering the light inlet of the condenser, the light ray directly hits the light outlet of the condenser, and the number N of the light rays hitting the light outlet is recordedout；
6.5) at completion of NinTransmission of light from strip vertically incident on light inlet in condenserAfter the calculation of the playing process, the total number N of the rays hitting the light outlet of the condenser can be obtainedoutAnd further through Qdesign,ij＝Nout·(Id·S1/Nin) Calculating the actual solar power Q collected to the light outletdesign,ij。
Further, all the nodes of the planar triangular meshes in the step 6.1) are required to be located on the reflecting surface of the condenser, the area of each mesh is required to be less than one fifth of the area of the light outlet of the condenser, and the absolute value of the relative deviation of the areas of any two planar triangular meshes is not more than 200%.
Further, the number of the light rays vertically incident to the light inlet in the step 6.2) is not less than (10)6·S1/S2) Strip, S1Is the area of the light inlet, and
each ray represents a solar power of (I)d·S1/Nin) (ii) a The sunlight projected to the same point on the light inlet is regarded as being randomly and uniformly distributed in a cone with the point as a vertex and a cone angle of 0.533 degrees; the unit direction vector of the light randomly incident to the light inlet
Can be represented by the following formula:
in the formula, phi2And gamma2Is a random angle variable; lambda [ alpha ]4And λ5Are independent random numbers uniformly distributed in the interval from 0 to 1.
Further, the step 7) adjusts NθAnd NaThe numerical method comprises the following steps: will NθBecomes 2 times its initial value, NaBecoming 2 times its initial value.
Compared with the existing design method, the design method has the advantages that:
first, the design method of the present invention uses rigorous mathematical expressions to define the geometric model, i.e., position, shape, and size, of the combined parabolic concentrator. The geometric model defined by the mathematical expression is strict and unique after the input geometric parameters are given, and the geometric model can be quickly and conveniently modified by modifying the input geometric parameters, so the design method has the advantages of accurately, quickly and conveniently constructing and designing the geometric model of the condenser.
Secondly, the design method simulates the gathering process of sunlight in the combined parabolic condenser by tracking the propagation of light rays in the condenser, and can solve the problems of ideal optical hypothesis and difficulty in considering complex optical effects such as non-ideal profile optical errors, multiple reflections in the condenser and the like in the traditional design method, thereby accurately establishing an optical model and realizing accurate assessment of the condensing performance.
Thirdly, the design method can automatically modify the design parameters based on the light gathering performance evaluation result until the design requirements are met, thereby realizing the automatic optimization design of the structure of the light gathering device, improving the design efficiency of the light gathering device and reducing the design cost of the light gathering device.
Fourthly, the design method has strong universality and can be widely applied to the design of the combined paraboloid type solar condenser in the solar energy utilization technologies such as light-gathering type solar heat utilization, light-gathering type photovoltaic power generation, light-gathering type photo-thermal power generation and the like.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of the configuration of the combined parabolic solar concentrator of the present invention;
FIG. 3 is a schematic structural view of a hexagonal compound paraboloid of the present invention;
FIG. 4 is a schematic view of the structure of a compound paraboloid of revolution of the present invention;
FIG. 5 is a schematic view of the intersection and mutual division of a hexagonal compound parabola with a paraboloid compound parabola of the present invention;
FIG. 6 is a schematic view of the planar triangular meshing on the reflective surface of the combined parabolic solar concentrator of the present invention;
wherein, 1-light inlet, 2-light outlet, 3-first mirror surface molded line, and 4-second mirror surface molded line.
Detailed Description
The present invention will be further explained with reference to the drawings and specific examples in the specification, and it should be understood that the examples described are only a part of the examples and not all examples of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The invention provides a design method of a combined paraboloid type solar concentrator, which specifically comprises the following steps of:
1) determining design optical parameters and design operation parameters of a condenser to be designed, wherein the design optical parameters comprise the specular reflectivity rho and the profile error sigma of a reflecting surface of the condenser, and the design operation parameters comprise the direct solar radiation intensity Id；
2) The area S of the light outlet 2 of the condenser is designed according to actual requirements2(ii) a Calculating half a of the width of the opposite side of the hexagonal light outlet of the hexagonal compound paraboloid according to the formula (1)2；
3) Determining design target parameters of the combined paraboloid type solar concentrator: the design target parameters include the solar power Q concentrated at the exit 2 of the concentrator under the condition that the sunlight is incident perpendicular to the plane of the entrance 1reqAnd Q isreqShould be within the range shown in formula (2); see fig. 2, 3 and 4The combined parabolic concentrator to be designed is formed by combining a part of surface of a hexagonal compound paraboloid with a hexagonal cross section and a part of surface of a revolution surface compound paraboloid with a circular cross section, the symmetry axes of the two compound paraboloids are superposed to form a symmetry axis of the concentrator, a right-hand rectangular coordinate system xyz is established in the design, the z axis of the right-hand rectangular coordinate system is superposed with the symmetry axis of the concentrator, the positive direction of the x axis points to the center of a light inlet 1 from the center of a light outlet 2 of the concentrator, and an original point o is positioned in the center of the light outlet 2 of the concentrator; defining an azimuth angle beta in an xy plane, wherein the positive direction of the y axis is 0 DEG, and the counterclockwise rotation is positive;
where ρ is a specular reflectance of the reflecting surface; σ is the profile error of the reflecting surface, rad; i isdW.m. direct solar radiation intensity-2；
4) Determining a range and a parameter combination of geometric parameters of the hexagonal compound paraboloid, wherein the geometric parameters comprise: hexagonal composite paraboloid half receiving angle theta1,iAnd half width a of opposite sides of the hexagonal light inlet1,j(ii) a In the design will theta1,iIs limited within (5 DEG, 30 DEG), and theta1,iIs set to (N)θ-1) species; a is to1,jIs limited in the range of (a)2,a2/sinθ1,i) In which a is1,jIs set to (N)a-1) species; will NθAnd NaAre set to 25 and 50, respectively; at the value of the ith parameter, theta1,iTaking values according to the formula (3); under the j value, a1,jTaking values according to the formula (4); at different values of i and j, θ1,iAnd a1,jIs combined with (N)θ-1)·(Na-1) species;
5) at each theta separately1,iAnd a1,jUnder the value combination, a geometric model of the combined paraboloid solar concentrator is established, and the method specifically comprises the following steps:
5.1) in the yz plane according to formula (5) at a2≤y≤a1,jThe first mirror profile 3 is plotted within the range of (a), as shown in fig. 3;
5.2) calculating the distance h between the plane of the light inlet 1 and the plane of the light outlet 2 of the condenser by adopting the formula (6)ij；
5.3) designing the geometric parameters of the revolution surface compound paraboloid, wherein the radius r of the light inlet of the revolution surface compound paraboloid is calculated by adopting the formula (7)1,jCalculating the radius r of the light outlet of the compound paraboloid of revolution surface by adopting the formula (8)2Calculating the semi-receiving angle theta of the compound paraboloid of the revolution surface by adopting the formula (9)2,ij；
r1,j＝a1,j/cos30° (7)
r2＝a2/cos10° (8)
5.4) in the yz plane according to formula (10) at r2≤y≤r1,jThe second mirror profile 4 is plotted within the range of (a), as shown in fig. 4;
5.5) respectively stretching the first mirror surface molded line 3 for 0.5r along the positive and negative directions of the x axis1,jForming a paraboloid; copying 6 parts of the paraboloid in the original position, and respectively rotating 5 parts of the paraboloid around the z-axis by 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees so as to obtain 6 paraboloids which are rotationally and symmetrically arranged around the z-axis; then, firstly, the intersection line of any two adjacent paraboloids is obtained, and each paraboloid is divided into two parts of curved surfaces by taking the intersection line as a dividing line; then, a radius (r) is drawn on the plane where z is 02+a2The/cos 30) -2 circular ring judges whether the two parts of curved surfaces divided by each paraboloid intersect with the circular ring; then, the part of the two parts of curved surfaces divided by each paraboloid, which are not intersected with the circular ring, is reserved, and the part of the two parts of curved surfaces divided by each paraboloid, which are intersected with the circular ring, is discarded; finally, 6 partial curved surfaces remained by the 6 paraboloids surround a hexagonal composite paraboloid with a hexagonal xy section, as shown in fig. 3;
5.6) rotating the second mirror surface molded line 4 by 360 degrees around the z axis to form a revolution surface three-dimensional compound paraboloid, as shown in FIG. 4;
5.7) obtaining 12 arc-shaped intersecting lines at the intersection of the hexagonal compound paraboloid and the revolution surface compound paraboloid, wherein the 12 arc-shaped intersecting lines are respectively an arc line AG, an arc line AH, an arc line BI, an arc line BJ, an arc line CK, an arc line CL, an arc line DM, an arc line DN, an arc line EP, an arc line ET, an arc line FU and an arc line FV shown in the figure 5; dividing the hexagonal compound parabolic surface and the revolution surface compound parabolic surface into different curved surfaces by taking the intersecting line as a dividing line; then, the 6 parabolic curved surfaces at the positions of 0 °, 60 °, 120 °, 180 °, 240 ° and 300 ° of the azimuth angle β divided by the hexagonal compound paraboloid are respectively the curved surface EPDN, the curved surface DMLC, the curved surface CKJB, the curved surface BIHA, the curved surface AGVF and the curved surface FUTE shown in fig. 5, and the 6 parabolic curved surfaces at the positions of 30 °, 90 °, 150 °, 210 °, 270 ° and 330 ° of the azimuth angle β divided by the revolution surface compound paraboloid are respectively the curved surface DNM, the curved surface CLK, the curved surface BJI, the curved surface AHG, the curved surface FUV and the curved surface EPN shown in fig. 5, so as to form a combined parabolic solar concentrator formed by combining 12 parabolic curved surfaces;
6) at each theta separately1,iAnd a1,jUnder the value combination, the propagation process of solar radiation energy in the condenser is simulated and calculated, and the solar power Q which can be concentrated on the light outlet 2 by each condenser design scheme is obtained through calculationdesign,ij(ii) a The simulation calculation of the propagation process of the solar radiation energy in the concentrator specifically comprises the following steps:
6.1) dividing the reflecting surface of the combined parabolic solar concentrator into a finite number of continuous and non-overlapping planar triangular meshes; all the nodes of the plane triangular meshes are required to be positioned on the reflecting surface of the condenser, the area of each mesh is required to be less than one fifth percent of the area of the light outlet of the condenser, and the absolute value of the relative deviation of the areas of any two plane triangular meshes is not more than 200 percent, so that the reflecting surface of the condenser is well fitted by the divided plane triangular meshes, and a mesh distribution schematic diagram is shown in FIG. 6;
6.2) consider solar energy perpendicularly incident on the hexagonal light inlet 1 of the condenser as NinThe light rays with the same power are uniformly projected on the light inlet 1 by the strips; the number of light rays perpendicularly incident to the light inlet 1 is not less than (10)6·S1/S2) Strip, S1Is the area of the light inlet 1, and
each ray represents a solar power of (I)d·S1/Nin) (ii) a Meanwhile, in order to consider the inherent unparallel characteristic of the sunlight, the sunlight projected to the same point on the light inlet 1 is regarded as being randomly and uniformly distributed in a cone with the point as a vertex and a cone angle of 0.533 degrees; the unit direction vector of the light randomly incident to the light inlet
Can be represented by formula (11);
in the formula, phi2And gamma2Random angle variables introduced to account for sun nonparallel characteristics; lambda [ alpha ]4、λ5Are mutually independent random numbers which are uniformly distributed in the interval of 0 to 1;
6.3) judging whether the light rays entering the light inlet 1 of the condenser hit any one plane triangular grid on the reflecting surface of the condenser; if the intersection point of the light ray and a certain triangular mesh exists, the formula (12) is adopted to randomly determine whether the light ray is reflected by the reflecting surface at the triangular mesh; if the light is reflected, calculating according to Fresnel reflection law to obtain reflection vector of the light on the reflection surface at the triangular mesh
The influence of the profile error of the reflecting surface on the normal vector direction of the triangular mesh is considered in the calculation, and the radial random deflection angle phi of the actual normal vector of the triangular mesh relative to the ideal normal vector of the plane of the triangular mesh1And random declination angle gamma in circumferential direction1Can be generated by formula (13); in the calculation, the light rays can be reflected on the reflecting surface of the condenser for multiple times, and the calculation is carried out by adopting the method;
in the formula, λ1、λ2、λ3Are mutually independent random numbers which are uniformly distributed in the interval of 0 to 1;
6.4) judging whether the light rays which are reflected once or for many times by the reflecting surface after entering the light inlet 1 of the condenser have intersection points with the light inlet 1 and the light outlet 2 of the condenser; if it has a crossing point with the light outlet 2 of the condenser, the number N of the light hitting the light outlet 2 is recordedout(ii) a If it has a crossing point with the light inlet 1 of the condenser, it indicates that the light is lost from the light inlet 1 and is not collected to the light outlet 2Then solving the propagation process of the next light ray incident to the light inlet 1; if the light ray enters the light inlet 1 of the condenser and does not hit any plane triangular grid on the reflecting surface of the condenser, the light ray directly hits the light outlet 2 of the condenser, and the number N of the light rays hitting the light outlet 2 is recordedout；
6.5) at completion of NinAfter calculating the propagation process of the light vertically incident on the light inlet 1 in the condenser, the total number N of the light hitting the light outlet 2 of the condenser can be obtainedoutAnd further through Qdesign,ij＝Nout·(Id·S1/Nin) Calculating the actual solar power Q collected at the light outlet 2design,ij；
7) Each kind of theta1,iAnd a1,jSolar power Q collected to the light outlet 2 calculated under combinationdesign,ijAnd design target parameter QreqComparing, judging whether each design scheme meets the design requirement by adopting the formula (14), and recording the theta corresponding to the design scheme meeting the design requirement1,iAnd a1,jCombining values; if at all (N)θ-1)·(Na-1) theta1,iAnd a1,jIf the design schemes of the condenser under the value combination do not meet the design requirement of the formula (14), firstly N is addedθBecomes 2 times its initial value, and N is addedaChanging to 2 times of the initial value, returning to the step 4) to carry out design calculation again until the design requirement of the formula is met, and recording all theta meeting the design requirement1,iAnd a1,jCombining values;
8) comparing and calculating half receiving angles theta of the hexagonal compound parabolic surfaces corresponding to all design schemes meeting the requirement of the formula (14)1,iAnd will be theta1,iThe maximum design scheme is selected as the final design result, namely the half receiving angle of the hexagonal composite polishing surface and the half width of the opposite side of the light inlet 1 are obtained, and the revolution surface composite is obtainedAnd combining the radiuses of the paraboloid light inlet 1 and the paraboloid light outlet 2 to finish the design.
The following table is a list of parameters involved in the design method of the present invention:
the combined parabolic concentrator designed by the design method is an integral formed by seamlessly combining 6 local surfaces of a hexagonal compound paraboloid with a hexagonal cross section and 6 local surfaces of a revolution surface compound paraboloid with a circular cross section, and the symmetry axes of the two compound paraboloids are overlapped and combined to form the symmetry axis of the concentrator, so that the combined parabolic concentrator is solar energy concentrating equipment with 12 curved surfaces.
The design method provided by the invention comprises the following steps of firstly, determining optical and operating parameters of a condenser; then, setting the area of a light outlet according to requirements, and setting the value of the light outlet by taking the light concentration power obtained at the light outlet when the sunlight is incident vertically to the light inlet as a design target parameter; then, determining the combination of geometric parameters of the condenser, and establishing a geometric model of a design scheme under each combination; then, simulating the solar energy gathering process in each scheme to obtain corresponding gathering power; finally, selecting a scheme meeting the design requirement, and selecting the scheme with the maximum receiving half angle as a final scheme; and if the scheme meeting the requirements cannot be obtained under the current geometric parameter combination, automatically adjusting the geometric parameter combination, and redesigning until the scheme meeting the requirements is obtained. The method can quickly, accurately and conveniently realize the design and construction of a geometric model, the construction of an optical performance simulation calculation model and the light gathering performance evaluation of the combined parabolic condenser, and further realize the automatic optimization design of the condenser structure based on the light gathering performance evaluation result, thereby improving the design efficiency of the condenser and reducing the design cost of the condenser; in addition, the design method has strong universality and can be widely applied to the design of the combined paraboloid type solar concentrator in the solar energy utilization technologies such as light-concentrating solar energy heat utilization, light-concentrating photovoltaic power generation, light-concentrating photo-thermal power generation and the like.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A design method of a combined paraboloid type solar concentrator is characterized by comprising the following steps:
1) determining design optical parameters and design operation parameters of a condenser to be designed, wherein the design optical parameters comprise the specular reflectivity rho and the profile error sigma of a reflecting surface of the condenser, and the design operation parameters comprise the direct solar radiation intensity Id；
2) Determining the area S of the light outlet of a condenser2And calculating half a of the width of the opposite side of the hexagonal light outlet of the hexagonal compound paraboloid according to the following formula2：
3) Determining design target parameters of the condenser: the design target parameter includes the solar power Q concentrated at the exit of the concentrator under the condition that sunlight is incident perpendicular to the plane of the entrancereq(ii) a And establishing a right-hand rectangular coordinate system xyz, wherein the z axis is coincident with the symmetry axis of the condenser, and the positive direction of the z axis is convergedThe center of the light outlet of the optical device points to the center of the light inlet, and the origin o is positioned at the center of the light outlet of the optical collector; defining an azimuth angle beta in an xy plane, and rotating anticlockwise to be positive by taking the positive direction of the y axis as 0 degrees;
4) determining the range and parameter combination of geometric structure parameters of the hexagonal compound paraboloid, wherein the geometric structure parameters comprise: hexagonal composite paraboloid half receiving angle theta1,iAnd half width a of opposite sides of the hexagonal light inlet1,j(ii) a Will theta1,iIs limited within (5 DEG, 30 DEG), and theta1,iIs set to (N)θ-1) species; a is to1,jIs limited to (a)2,a2/sinθ1,i) In which a is1,jIs set to (N)a-1) is NθAnd NaSelecting an initial value;
at the ith value, θ1,iThe following values are taken:
under the j value, a1,jThe following values are taken:
at different values of i and j, θ1,iAnd a1,jIs combined with (N)θ-1)·(Na-1) species;
5) at each theta separately1,iAnd a1,jUnder the value combination, the method for establishing the geometric model of the condenser comprises the following steps:
5.1) in the yz plane according to the formula2≤y≤a1,jThe first mirror profile is plotted within:
sin2θ1,i·z2+[2(y+a2)·sinθ1,i-4a2(1+sinθ1,i)]cosθ1,i·z+[(y+a2)2cos2θ1,i-4a2(1+sinθ1,i)(-y sinθ1,i+a2)]＝0
5.2) calculating the distance h between the plane of the light inlet and the plane of the light outlet of the condenser using the following formulaij：
5.3) designing the geometric parameters of the compound paraboloid of the revolution surface, and calculating the radius r of the light inlet of the compound paraboloid of the revolution surface by adopting the following formula1,j：
r1,j＝a1,j/cos30°
The radius r of the light outlet of the compound paraboloid of the revolution surface is calculated by adopting the following formula2：
r2＝a2/cos10°
Calculating the semi-receiving angle theta of the compound paraboloid of the revolution surface by adopting the following formula2,ij：
[(r1,j+r2)cosθ2,ij+hijsinθ2,ij]2
＝4r2(1+sinθ2,ij)(-r1,jsinθ2,ij+hijcosθ2,ij+r2)
5.4) in the yz plane by the formula r2≤y≤r1,jA second mirror profile is plotted within:
sin2θ2,ij·z2+[2(y+r2)·sinθ2,ij-4r2(1+sinθ2,ij)]cosθ2,ij·z+[(y+r2)2cos2θ2,ij-4r2(1+sinθ2,ij)(-ysinθ2,ij+r2)]＝0
5.5) respectively stretching the first mirror surface molded line for 0.5r along the positive and negative directions of the x axis1,jForming a paraboloid; copying 6 parts of the paraboloid in the original position, and respectively rotating 5 parts of the paraboloid around the z-axis by 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees so as to obtain 6 paraboloids which are rotationally symmetrically arranged around the z-axis; then, first, the above-mentionedThe intersection line of any two adjacent paraboloids is used as a dividing line to divide each paraboloid into two parts of curved surfaces; then, a radius (r) is drawn on the plane where z is 02+a2The/cos 30) -2 circular ring judges whether the two parts of curved surfaces divided by each paraboloid intersect with the circular ring; then, the part of the two parts of curved surfaces divided by each paraboloid, which are not intersected with the circular ring, is reserved, and the part of the two parts of curved surfaces divided by each paraboloid, which are intersected with the circular ring, is discarded; finally, 6 partial curved surfaces reserved by the 6 paraboloids enclose a hexagonal compound paraboloid with a hexagonal xy section;
5.6) rotating the second mirror surface profile by 360 degrees around the z axis to form a revolution surface three-dimensional compound paraboloid;
5.7) solving 12 arc-shaped intersecting lines at the intersection of the hexagonal compound paraboloid and the revolution surface compound paraboloid, and respectively dividing the hexagonal compound paraboloid and the revolution surface compound paraboloid into different curved surfaces by taking the intersecting lines as dividing lines; then, 6 parabolic curved surfaces at the positions of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees of azimuth angle beta divided by the hexagonal compound paraboloid are reserved, and at the same time, 6 parabolic curved surfaces at the positions of 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees and 330 degrees of azimuth angle beta divided by the revolution surface compound paraboloid are reserved, so that a combined parabolic condenser formed by combining 12 solar curved surfaces is formed;
6) at each theta separately1,iAnd a1,jUnder the value combination, the propagation process of solar radiation energy in the condenser is simulated and calculated: establishing an optical model aiming at the geometric model of the condenser, and calculating each theta by adopting an optical simulation method1,iAnd a1,jSolar power Q gathered on light outlet under value combinationdesign,ij；
7) Respectively mixing each kind of theta1,iAnd a1,jSolar power Q collected to light outlet and obtained by calculation under combinationdesign,ijAnd design target parameter QreqAnd comparing, and judging whether the design requirement is met by adopting the following formula:
if at all (N)θ-1)·(Na-1) theta1,iAnd a1,jIf the value combination does not satisfy the design requirement of the above formula, firstly adjusting NθAnd NaThe numerical value is returned to the step 4) to be calculated again until the design requirement of the formula is met, and all theta meeting the design requirement are recorded1,iAnd a1,jCombining values;
8) comparing and calculating all theta meeting the design requirement1,iSelecting the maximum theta1,iThe corresponding design is the final design result.
2. The design method of the combined paraboloid type solar energy concentrator according to claim 1, wherein the solar power Q concentrated at the light outlet of the concentrator under the condition that the sunlight is incident perpendicular to the plane of the light inlet in the step 3) isreqSatisfies the following formula:
wherein ρ is a specular reflectivity of the reflecting surface; σ is the profile error of the reflecting surface, rad; i isdW.m. direct solar radiation intensity-2。
3. The design method of the combined paraboloid type solar concentrator according to claim 1, wherein N in the step 4) isθAnd NaAre set to 25 and 50, respectively.
4. The design method of the combined paraboloid type solar concentrator according to claim 1, wherein the step 6) of simulating and calculating the propagation process of solar radiation energy in the concentrator comprises the following steps:
6.1) dividing the reflecting surface of the combined parabolic solar concentrator into a finite number of continuous and non-overlapping planar triangular meshes;
6.2) regarding the solar energy vertically incident to the hexagonal light inlet of the condenser as NinThe light rays with the same power are uniformly projected onto the light inlet by the strips;
6.3) judging whether the light rays entering the light inlet of the condenser hit any one plane triangular grid on the reflecting surface of the condenser; if there is a crossing point between the light and a triangle mesh, then the following formula is used to randomly determine whether the light will be reflected by the reflection surface at the triangle mesh:
if the light is reflected, calculating according to Fresnel reflection law to obtain reflection vector of the light on the reflection surface at the triangular mesh
Radial random deflection angle phi of actual normal vector of triangular mesh relative to ideal normal vector of triangular mesh plane1And random declination angle gamma in circumferential direction1Can be generated using the following formula:
in the formula, λ1、λ2And λ3The random numbers are mutually independent and uniformly distributed in the interval of 0 to 1, and sigma is the profile error of the reflecting surface;
6.4) judging whether the light rays which are reflected once or for many times by the reflecting surface after entering the light inlet of the condenser have intersection points with the light inlet and the light outlet of the condenser; if it has an intersection point with the light outlet of the condenser, the number N of the light hitting the light outlet is recordedout(ii) a If the intersection point of the light ray and the light inlet of the condenser is found, the light ray is lost from the light inlet and is not condensed to the light outlet, and then the next light ray entering the light inlet is solvedA propagation process of the wire; if the light ray enters the light inlet of the condenser and does not hit any plane triangular grid on the reflecting surface of the condenser, the light ray directly hits the light outlet of the condenser, and the number N of the light rays hitting the light outlet is recordedout；
6.5) at completion of NinAfter the calculation of the propagation process of the light rays vertically incident on the light inlet of the strip in the condenser, the total number N of the light rays hitting the light outlet of the condenser can be obtainedoutAnd further through Qdesign,ij＝Nout·(Id·S1/Nin) Calculating the actual solar power Q collected to the light outletdesign,ij，S1The area of the light inlet is shown.
5. The design method of the combined paraboloid type solar energy condenser according to claim 4, wherein all the nodes of the planar triangular meshes in the step 6.1) are required to be located on the reflecting surface of the condenser, the area of each mesh is required to be less than one fifth percent of the area of the light outlet of the condenser, and the absolute value of the relative deviation of the areas of any two planar triangular meshes is not more than 200%.
6. The design method of the combined paraboloid type solar energy condenser according to claim 4, wherein the number of the light rays vertically incident to the light inlet in the step 6.2) is not less than (10)6·S1/S2) Strip, S1Is the area of the light inlet, and
each ray represents a solar power of (I)d·S1/Nin) (ii) a The sunlight projected to the same point on the light inlet is regarded as being randomly and uniformly distributed in a cone with the point as a vertex and a cone angle of 0.533 degrees; the unit direction vector of the light randomly incident to the light inlet
Can be represented by the following formula:
in the formula, phi2And gamma2Is a random angle variable; lambda [ alpha ]4And λ5Are mutually independent random numbers uniformly distributed in the interval from 0 to 1.
7. The design method of claim 1, wherein the step 7) of adjusting N is performedθAnd NaThe numerical method comprises the following steps: will NθBecomes 2 times its initial value, NaBecoming 2 times its initial value.
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