CN105509339A - Free-surface secondary reflection concentrator system for efficient solar energy thermal/electric conversion - Google Patents

Abstract

The invention relates to a concentrator system for efficient solar energy thermal/electric conversion, in particular to a free-surface secondary reflection concentrator system for efficient solar energy thermal/electric conversion. The invention aims at solving the technical problem that at present, the area of an entrance of a heat absorption cavity of the traditional solar dish type concentration system is limited, so that the traditional solar dish type concentration system is not capable of receiving the energy of all light spots and can intercept the energy of the light spots; therefore, resource waste is caused. The free-surface secondary reflection concentrator system for efficient solar energy thermal/electric conversion comprises a primary mirror, a secondary mirror and a receiver, wherein the primary mirror, the secondary mirror and the receiver respectively have an axisymmetric structure and are arranged coaxially; the receiver consists of a heat absorber, a concentrating photovoltaic cell panel and a flange; the concentrating photovoltaic cell panel is arranged at the outer side of the flange; a free-form surface of the secondary mirror is determined as follows: 1, dissociaton of a starting point and a target point; 2, solution of discrete points of the free-form surface of the secondary mirror; 3, drawing of the surface of the secondary mirror. The free-surface secondary reflection concentrator system for efficient solar energy thermal/electric conversion is applied to the field of solar energy.

Description

A kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity

Technical field

The present invention relates to a kind of condenser system efficiently changed for solar heat/electricity.

Background technology

Along with the development of precise machine machining, and the arrival of newborn 3D printing technique, the design of advanced optical system is made to become high efficient and flexible more, because free form surface has higher design freedom and space layout flexibly relative to traditional approach, the design of optical system is simplified, makes it have compact conformation, high usage and the advantage such as energy-conservation.Different with traditional optical system, scope of freedom type light path system does not have certain specific face type equation, equation formulations can not be utilized to define it, free form surface is made up of many spatial point often, carries out connection afterwards reconstruct final acquisition face, space shape by non-uniform rational B-spline (NURBS) curve or alternate manner.This technology is applied seldom in field of solar energy, still has to be developed.Gauss's energy flow point cloth that tradition solar energy dish-style lens system obtains, is characterized in higher the closer to center position energy flow valuve, in the outer part can the aobvious reduction of lumen.In actual applications, for ensureing sealing and security, the inlet area of solar energy heat absorbing cavity is limited, many times can not receive the energy of whole hot spot, therefore can intercept it, casts out the gathering light spot energy in outside, causes the waste of resource.

Summary of the invention

The present invention is that the inlet area of the heat absorption cavity that will solve current traditional solar energy dish-style lens system is limited, the energy of whole hot spot can not be received, can intercept it, cause the technical problem of the waste of resource, and a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity is provided.

Scope of freedom Opticai Concentrating System With Secondary Reflection for the efficient conversion of solar heat/electricity of the present invention adopts scope of freedom type Cassegrain to reflect lens system, is made up of a secondary mirror, secondary mirror and receiver; One secondary mirror, secondary mirror and receiver are all axially symmetric structures, and a secondary mirror, secondary mirror and receiver three are coaxial; One secondary mirror is connected by support with secondary mirror, and the concave surface of a secondary mirror is towards secondary mirror, and receiver is fixed on support, and Bracket setting is on the axis of a secondary mirror, secondary mirror and receiver three; Receiver is made up of heat dump and condensation photovoltaic cell panel and flange, and flange is arranged on the optical window end of heat dump, and condensation photovoltaic cell panel is arranged on the outside of flange, and the optical window of heat dump is towards secondary mirror; Heat dump is cylindrical, and condensation photovoltaic cell panel is hollow ring;

One secondary mirror adopts traditional solar energy dish-style parabolic mirror, and secondary mirror is the mirror surface of a free form surface form, and the determination mode of the free form surface of secondary mirror is as follows:

One, initial sum impact point is discrete:

Determine the size of a secondary mirror and receiver, computing formula is as follows:

w(R _max ²-R _min ²)/C _G＝(r _max ²-r _min ²)(1)，

W is the occupation ratio of condensation photovoltaic subsystem, C _gthe geometric concentrating ratio of condensation photovoltaic subsystem, R _maxthe outer radii of a secondary mirror, R _minthe inner radii of a secondary mirror, r _maxthe outer radii of condensation photovoltaic cell panel in receiver, r _minthe inner radii of the condensation photovoltaic cell panel in receiver, R _min>=r _max, wherein five is known quantity, can obtain the 6th amount, determine the size of a secondary mirror and receiver;

Set up three-dimensional cartesian coordinate system (x, y, z), initial point O is the intersection point of support and a secondary mirror, z-axis is pointed to the axis in secondary mirror direction, y-axis be parallel to condensation photovoltaic cell panel in receiver radius and point to the axis in condensation photovoltaic cell panel direction by initial point, x-axis be through initial point O and with the axis of z-axis and y-axis place plane orthogonal, only getting z-axis and y-axis is that the region of positive number calculates;

A secondary mirror is got n some P _{i, j-1}, n is positive integer, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of n point, and i is positive integer, and No. 1 is that on a secondary mirror, y-axis coordinate value equals R _maxpoint, No. n is that on a secondary mirror, y-axis coordinate value equals R _minpoint, sequence number i progressively increases along No. 1 to No. n, y _{i, j-1}be the coordinate value in y-axis in this n point, computing formula is as follows:

y _i,j-1＝y _1,j-1-(i-1)×(y _1,j-1-y _n,j-1)/n(2)；

Point P _{i, j-1}z-axis coordinate adopt formula z=y ²/ 4f calculates, and f is the focal length of a secondary mirror;

Determine point optical node P on a secondary mirror _{k, j-1}, calculate its y-axis coordinate value y _{k, j-1}, computing formula is as follows:

$y_{k,j-1}=\sqrt{(1-w){R_{\max }}^2+{{\mathrm{wR}}_{\min }}^2}---\left(3\right),$ n＞k＞1，

If the n got on a secondary mirror some P _{i, j-1}do not comprise a point optical node P _{k, j-1}, then a y-axis coordinate value and y is looked in n point on a secondary mirror _{k, j-1}immediate some P _{i, j-1}as a point optical node P _{k, j-1};

Get m some P on the receiver _{i, j+1}, m is positive integer and m=n, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of m point, and i is positive integer, and No. 1 is that on receiver, y-axis coordinate value equals r _maxpoint, sequence number i progressively increases along No. 1 to No. m, y _{i, j+1}the coordinate value in y-axis in this m point, y _{k, j+1}equal r _min, the y of remaining m-1 point _{i, j+1}computing formula is as follows:

Y _{i, j+1}=y _{1, j+1}-(i-1) × (y _{1, j+1}-y _{n, j+1}during)/m, i≤k

(4)；

Y _{i, j+1}during=0, i > k

Two, the solving of secondary mirror free form surface discrete point:

Setting P _i,jthe point P on a mirror is mapped to for solar irradiation _{i, j-1}reflex to point corresponding in secondary mirror, θ _ifor P _i,jcorresponding reflection half-angle, θ _iaccount form as follows:

${\mathrm{\θ}}_i=\frac{1}{2}{\cos }^{-1}(-v_{i,j}\·v_{i,j+1})---\left(5\right),$

V _i,jand v _{i, j+1}representation vector respectively and vector unit vector;

N _ifor a P _i,jnormal vector, n _iobtained by following formula:

Matrix Rot (x, θ _i) be:

$Rot(x,{\mathrm{\θ}}_i)=\left[\begin{array}{cccc}1& 0& 0& 0\\ 0& {\mathrm{cos\θ}}_i& {\mathrm{sin\θ}}_i& 0\\ 0& -{\mathrm{sin\θ}}_i& {\mathrm{cos\θ}}_i& 0\\ 0& 0& 0& 1\end{array}\right]---\left(7\right);$

Point P _{1, j}coordinate be known quantity, its normal vector n ₁also can obtain accordingly,

Normal vector n _ireverse extending line be vectorial V _i, adjacent two normal vector n _iand n _i-1corresponding reverse extending alignment amount V _iwith vectorial V _i-1intersection point be C _i-1, make vectorial V _i-1=vectorial V _i, i.e. following formula:

$\left\{\begin{array}{c}{V}_{i-1}=P_{i-1,j}+n_{i-1}{t}_{i-1}\\ V_i=P_{i,j}+n_i{t}_i\end{array}\right.---\left(8\right),$

T _i-1and t _ibe respectively vectorial V _i-1with vectorial V _iargument, i.e. t _ipoint P _i,jto a C _ilength;

P _i,jbe expressed from the next:

P _i,j＝P _i,j-1+λ _iv _i,j(9)，

λ _ifor vector mould;

Formula (5) (7) (9) are substituted in (6), draws n _iwith parameter lambda _imonotropic function, substitute in formula (8), with t _i-1and t _ifor unknown number, obtain function:

$t_i=\frac{P_{i-1,j}\left(z\right)+n_{i-1}\left(z\right)\left(P_{i,j-1}\right(y)+{\mathrm{\λ}}_i{v}_{i,j}(y)-P_{i-1,j}(y\left)\right)}{n_{i-1}\left(y\right)}-\frac{P_{i,j-1}\left(z\right)+{\mathrm{\λ}}_i{v}_{i,j}\left(z\right)}{n_i\left(z\right)-n_{i-1}\left(z\right)n_i\left(y\right)/n_{i-1}\left(y\right)}---\left(10\right);$

Point C _i-1coordinate be:

C _i-1＝P _i,j+n _it _i(11)；

Formula (10) is substituted in (11) and draws a C _i-1coordinate, then will C be put _i-1coordinate and formula (9) substitute into formula (12), can λ be tried to achieve _ivalue, by λ _ivalue substitute into formula (9), can P be tried to achieve _i,jcoordinate;

Three, secondary mirror curved surface is drawn: by P _i,jcoordinate adopt non-homogeneous B spline curve to connect reconstruct to obtain secondary mirror free curve, draw secondary mirror free curve, a secondary mirror and receiver with the three-dimensional constructing function of graphics software, curve is rotated around z-axis, obtain three-dimensional free surface.

The particular location of receiver of the present invention on support can regulate according to actual needs voluntarily, regulates the change in location of receiver that the free form surface of secondary mirror can be made again to solve.

Advantage of the present invention:

1, gross energy utilization rate and conversion efficiency high

The skew ray vector transmission principle that the present invention adopts can obtain optimal energy flow point cloth according to the concrete condition that can flow receiving plane, the peak value that acquisition one secondary mirror reflects can be flowed the highest part energy by heat dump, condensation photovoltaic cell panel receives the energy of remainder, and the energy flow point cloth borrowing the optimal design of secondary scope of freedom mirror to obtain homogenising, the mounting flange of cell panel and heat dump will obtain minimum energy, and this system makes as far as possible many energy effectively be transformed;

2, processing cost is manufactured low

A secondary mirror of the present invention adopts traditional dish-style collector, so only needs the secondary mirror that fabrication design area is less accordingly, saves processing and manufacturing cost;

3, safety and reliability strong

Land use models is closed in concentration photovoltaic system solar heat often/Electricity Federation, especially the weakest in high power concentrator situation, hold flimsy link most, this method achieves the homogenising energy flow point cloth of concentration photovoltaic system, significantly improves safety and the reliability of system;

4, design freedom is high

Based on the skew ray vector transmission method for designing that the present invention proposes, can according to the particular demands of user, adaptability structured parameter is obtained as adapted to the key elements such as any receiving plane position, light splitting ratio, prefocus stream size and uniformity, guarantee system running state is best, and design freedom is high.

This method is based on the incident ray in universal significance, and unconventional mode (must be parallel to the ray vectors of optical axis incidence) solves, the method utilizes basic vector correlation, namely mirror reflection law and law vector matrix derivation relational expression solve, possess good universality, many parameter requirements such as any receiving plane position, light splitting ratio, prefocus stream size and uniformity can be adapted to.

Accompanying drawing explanation

Fig. 1 is the schematic diagram for the scope of freedom Opticai Concentrating System With Secondary Reflection of the efficient conversion of solar heat/electricity in detailed description of the invention two, and 1 is a secondary mirror, and 2 is secondary mirror, and 4 is heat dumps, and 3 is condensation photovoltaic cell panels;

Fig. 2 is the upward view of receiver in detailed description of the invention two, and 4 is heat dumps, and 3 is condensation photovoltaic cell panels;

Fig. 3 is the optical schematic diagram for the scope of freedom Opticai Concentrating System With Secondary Reflection of the efficient conversion of solar heat/electricity in detailed description of the invention two, and 1 is a secondary mirror, and 2 is secondary mirror, and 4 is heat dumps, and 3 is condensation photovoltaic cell panels;

Fig. 4 is the optical schematic diagram of secondary mirror in detailed description of the invention two, and 2 is secondary mirror;

Fig. 5 is the light transmission path profile of test two, and 2 is secondary mirror;

Fig. 6 is the light transmission path profile of test three, and 2 is secondary mirror;

Fig. 7 is receiver focusing energy stream cloud charts in test one, and 3 is condensation photovoltaic cell panels, and 4 is heat dumps, and 6 is centers of circle of heat dump.

Detailed description of the invention

Detailed description of the invention one: present embodiment is a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity, adopts scope of freedom type Cassegrain to reflect lens system, is made up of a secondary mirror 1, secondary mirror 2 and receiver; One secondary mirror 1, secondary mirror 2 and receiver are all axially symmetric structures, and a secondary mirror 1, secondary mirror 2 and receiver three are coaxial; One secondary mirror 1 is connected by support 5 with secondary mirror 2, and the concave surface of a secondary mirror 1 is towards secondary mirror 2, and receiver is fixed on support 5, and support 5 is arranged on the axis of a secondary mirror 1, secondary mirror 2 and receiver three; Receiver is made up of heat dump 4 and condensation photovoltaic cell panel 3 and flange, and flange is arranged on the optical window end of heat dump 4, and condensation photovoltaic cell panel 3 is arranged on the outside of flange, and the optical window of heat dump 4 is towards secondary mirror 2; Heat dump 4 is cylindrical, and condensation photovoltaic cell panel 3 is hollow rings;

One secondary mirror adopts traditional solar energy dish-style parabolic mirror, and secondary mirror is the mirror surface of a free form surface form, and the determination mode of the free form surface of secondary mirror is as follows:

One, initial sum impact point is discrete:

Determine the size of a secondary mirror and receiver, computing formula is as follows:

w(R _max ²-R _min ²)/C _G＝(r _max ²-r _min ²)(1)，

W is the occupation ratio of condensation photovoltaic subsystem, C _gthe geometric concentrating ratio of condensation photovoltaic subsystem, R _maxthe outer radii of a secondary mirror, R _minthe inner radii of a secondary mirror, r _maxthe outer radii of condensation photovoltaic cell panel in receiver, r _minthe inner radii of the condensation photovoltaic cell panel in receiver, R _min>=r _max, wherein five is known quantity, can obtain the 6th amount, determine the size of a secondary mirror and receiver;

Set up three-dimensional cartesian coordinate system (x, y, z), initial point O is the intersection point of support and a secondary mirror, z-axis is pointed to the axis in secondary mirror direction, y-axis be parallel to condensation photovoltaic cell panel in receiver radius and point to the axis in condensation photovoltaic cell panel direction by initial point, x-axis be through initial point O and with the axis of z-axis and y-axis place plane orthogonal, only getting z-axis and y-axis is that the region of positive number calculates;

A secondary mirror is got n some P _{i, j-1}, n is positive integer, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of n point, and i is positive integer, and No. 1 is that on a secondary mirror, y-axis coordinate value equals R _maxpoint, No. n is that on a secondary mirror, y-axis coordinate value equals R _minpoint, sequence number i progressively increases along No. 1 to No. n, y _{i, j-1}be the coordinate value in y-axis in this n point, computing formula is as follows:

y _i,j-1＝y _1,j-1-(i-1)×(y _1,j-1-y _n,j-1)/n(2)；

Point P _{i, j-1}z-axis coordinate adopt formula z=y ²/ 4f calculates, and f is the focal length of a secondary mirror;

Determine point optical node P on a secondary mirror _{k, j-1}, calculate its y-axis coordinate value y _{k, j-1}, computing formula is as follows:

$y_{k,j-1}=\sqrt{(1-w){R_{\max }}^2+{{\mathrm{wR}}_{\min }}^2}---\left(3\right),$ n＞k＞1，

If the n got on a secondary mirror some P _{i, j-1}do not comprise a point optical node P _{k, j-1}, then a y-axis coordinate value and y is looked in n point on a secondary mirror _{k, j-1}immediate some P _{i, j-1}as a point optical node P _{k, j-1};

Get m some P on the receiver _{i, j+1}, m is positive integer and m=n, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of m point, and i is positive integer, and No. 1 is that on receiver, y-axis coordinate value equals r _maxpoint, sequence number i progressively increases along No. 1 to No. m, y _{i, j+1}the coordinate value in y-axis in this m point, y _{k, j+1}equal r _min, the y of remaining m-1 point _{i, j+1}computing formula is as follows:

Y _{i, j+1}=y _{1, j+1}-(i-1) × (y _{1, j+1}-y _{n, j+1}during)/m, i≤k

(4)；

Y _{i, j+1}during=0, i > k

Two, the solving of secondary mirror free form surface discrete point:

Setting P _i,jthe point P on a mirror is mapped to for solar irradiation _{i, j-1}reflex to point corresponding in secondary mirror, θ _ifor P _i,jcorresponding reflection half-angle, θ _iaccount form as follows:

${\mathrm{\θ}}_i=\frac{1}{2}{\cos }^{-1}(-v_{i,j}\·v_{i,j+1})---\left(5\right),$

V _i,jand v _{i, j+1}representation vector respectively and vector unit vector;

N _ifor a P _i,jnormal vector, n _iobtained by following formula:

Matrix Rot (x, θ _i) be:

$Rot(x,{\mathrm{\θ}}_i)=\left[\begin{array}{cccc}1& 0& 0& 0\\ 0& {\mathrm{cos\θ}}_i& {\mathrm{sin\θ}}_1& 0\\ 0& -{\mathrm{sin\θ}}_i& {\mathrm{cos\θ}}_i& 0\\ 0& 0& 0& 1\end{array}\right]---\left(7\right);$

Point P _{1, j}coordinate be known quantity, its normal vector n ₁also can obtain accordingly,

Normal vector n _ireverse extending line be vectorial V _i, adjacent two normal vector n _iand n _i-1corresponding reverse extending alignment amount V _iwith vectorial V _i-1intersection point be C _i-1, make vectorial V _i-1=vectorial V _i, i.e. following formula:

$\left\{\begin{array}{c}{V}_{i-1}=P_{i-1,j}+n_{i-1}{t}_{i-1}\\ V_i=P_{i,j}+n_i{t}_i\end{array}\right.---\left(8\right),$

T _i-1and t _ibe respectively vectorial V _i-1with vectorial V _iargument, i.e. t _ipoint P _i,jto a C _ilength;

P _i,jbe expressed from the next:

P _i,j＝P _i,j-1+λ _iv _i,j(9)，

λ _ifor vector mould;

Formula (5) (7) (9) are substituted in (6), draws n _iwith parameter lambda _imonotropic function, substitute in formula (8), with t _i-1and t _ifor unknown number, obtain function:

$t_i=\frac{P_{i-1,j}\left(z\right)+n_{i-1}\left(z\right)\left(P_{i,j-1}\right(y)+{\mathrm{\λ}}_i{v}_{i,j}(y)-P_{i-1,j}(y\left)\right)}{n_{i-1}\left(y\right)}-\frac{P_{i,j-1}\left(z\right)+{\mathrm{\λ}}_i{v}_{i,j}\left(z\right)}{n_i\left(z\right)-n_{i-1}\left(z\right)n_i\left(y\right)/n_{i-1}\left(y\right)}---\left(10\right);$

Point C _i-1coordinate be:

C _i-1＝P _i,j+n _it _i(11)；

Formula (10) is substituted in (11) and draws a C _i-1coordinate, then will C be put _i-1coordinate and formula (9) substitute into formula (12), can λ be tried to achieve _ivalue, by λ _ivalue substitute into formula (9), can P be tried to achieve _i,jcoordinate;

Three, secondary mirror curved surface is drawn: by P _i,jcoordinate adopt non-homogeneous B spline curve to connect reconstruct to obtain secondary mirror free curve, draw secondary mirror free curve, a secondary mirror and receiver with the three-dimensional constructing function of graphics software, curve is rotated around z-axis, obtain three-dimensional free surface.

Detailed description of the invention two: the difference of present embodiment and detailed description of the invention one is: described receiver is arranged on the point of intersection with a secondary mirror 1 on support 5.Other are identical with detailed description of the invention one.

Detailed description of the invention three: the difference of present embodiment and detailed description of the invention one or two is: described receiver to be arranged on support 5 with a secondary mirror 1 apart from 1/4 place for support 5 length.Other are identical with detailed description of the invention one or two.

Detailed description of the invention four: the difference of present embodiment and detailed description of the invention one to three is:: described receiver to be arranged on support 5 with a secondary mirror 1 apart from 1/3 place for support 5 length.Other are identical with detailed description of the invention one to three.

Detailed description of the invention five: the difference of present embodiment and detailed description of the invention one to four is:: described receiver to be arranged on support 5 with a secondary mirror 1 apart from 1/2 place for support 5 length.Other are identical with detailed description of the invention one to four.

By following verification experimental verification beneficial effect of the present invention:

Test one: this test is the scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity, adopts scope of freedom type Cassegrain to reflect lens system, is made up of a secondary mirror 1, secondary mirror 2 and receiver; One secondary mirror 1, secondary mirror 2 and receiver are all axially symmetric structures, and a secondary mirror 1, secondary mirror 2 and receiver three are coaxial; One secondary mirror 1 is connected by support 5 with secondary mirror 2, and the concave surface of a secondary mirror 1 is towards secondary mirror 2, and receiver is fixed on support 5, and support 5 is arranged on the axis of a secondary mirror 1, secondary mirror 2 and receiver three; Receiver is made up of heat dump 4 and condensation photovoltaic cell panel 3 and flange, and flange is arranged on the optical window end of heat dump 4, and condensation photovoltaic cell panel 3 is arranged on the outside of flange, and the optical window of heat dump 4 is towards secondary mirror 2; Heat dump 4 is cylindrical, and condensation photovoltaic cell panel 3 is hollow rings;

One secondary mirror adopts traditional solar energy dish-style parabolic mirror, and secondary mirror is the mirror surface of a free form surface form, and the determination mode of the free form surface of secondary mirror is as follows:

One, initial sum impact point is discrete:

Determine the size of a secondary mirror and receiver, computing formula is as follows:

w(R _max ²-R _min ²)/C _G＝(r _max ²-r _min ²)(1)，

W is the occupation ratio of condensation photovoltaic subsystem, C _gthe geometric concentrating ratio of condensation photovoltaic subsystem, R _maxthe outer radii of a secondary mirror, R _minthe inner radii of a secondary mirror, r _maxthe outer radii of condensation photovoltaic cell panel in receiver, r _minthe inner radii of the condensation photovoltaic cell panel in receiver, R _min>=r _max, wherein five is known quantity, can obtain the 6th amount, determine the size of a secondary mirror and receiver;

Set up three-dimensional cartesian coordinate system (x, y, z), initial point O is the intersection point of support and a secondary mirror, z-axis is pointed to the axis in secondary mirror direction, y-axis be parallel to condensation photovoltaic cell panel in receiver radius and point to the axis in condensation photovoltaic cell panel direction by initial point, x-axis be through initial point O and with the axis of z-axis and y-axis place plane orthogonal, only getting z-axis and y-axis is that the region of positive number calculates;

A secondary mirror is got 100 some P _{i, j-1}, n is positive integer, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of n point, and i is positive integer, and No. 1 is that on a secondary mirror, y-axis coordinate value equals R _maxpoint, No. n is that on a secondary mirror, y-axis coordinate value equals R _minpoint, sequence number i progressively increases along No. 1 to No. n, y _{i, j-1}be the coordinate value in y-axis in this n point, computing formula is as follows:

y _i,j-1＝y _1,j-1-(i-1)×(y _1,j-1-y _n,j-1)/n(2)；

Point P _{i, j-1}z-axis coordinate adopt formula z=y ²/ 4f calculates, and f is the focal length of a secondary mirror;

Determine point optical node P on a secondary mirror _{k, j-1}, calculate its y-axis coordinate value y _{k, j-1}, computing formula is as follows:

$y_{k,j-1}=\sqrt{(1-w){R_{\max }}^2+{{\mathrm{wR}}_{\min }}^2}---\left(3\right),$ n＞k＞1，

100 some P that a secondary mirror is got _{i, j-1}do not comprise a point optical node P _{k, j-1}, in 100 points on a secondary mirror, look for a y-axis coordinate value and y _{k, j-1}immediate some P _{50, j-1}as a point optical node P _{k, j-1};

Get 100 some P on the receiver _{i, j+1}, the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of 100 points, and i is positive integer, and No. 1 is that on receiver, y-axis coordinate value equals r _maxpoint, sequence number i progressively increases along No. 1 to No. 100, y _{i, j+1}the coordinate value in y-axis in these 100 points, y _{k, j+1}equal r _min, the y of remaining 99 point _{i, j+1}computing formula is as follows:

Y _{i, j+1}=y _{1, j+1}-(i-1) × (y _{1, j+1}-y _{n, j+1}during)/m, i≤k

(4)；

Y _{i, j+1}during=0, i > k

Two, the solving of secondary mirror free form surface discrete point:

Setting P _i,jthe point P on a mirror is mapped to for solar irradiation _{i, j-1}reflex to point corresponding in secondary mirror, θ _ifor P _i,jcorresponding reflection half-angle, θ _iaccount form as follows:

${\mathrm{\θ}}_i=\frac{1}{2}{\cos }^{-1}(-v_{i,j}\·v_{i,j+1})---\left(5\right),$

V _i,jand v _{i, j+1}representation vector respectively and vector unit vector;

N _ifor a P _i,jnormal vector, n _iobtained by following formula:

Matrix Rot (x, θ _i) be:

$Rot(x,{\mathrm{\θ}}_i)=\left[\begin{array}{cccc}1& 0& 0& 0\\ 0& {\mathrm{cos\θ}}_i& {\mathrm{sin\θ}}_i& 0\\ 0& -{\mathrm{sin\θ}}_i& {\mathrm{cos\θ}}_i& 0\\ 0& 0& 0& 1\end{array}\right]---\left(7\right);$

Point P _{1, j}coordinate be known quantity, its normal vector n ₁also can obtain accordingly,

Normal vector n _ireverse extending line be vectorial V _i, adjacent two normal vector n _iand n _i-1corresponding reverse extending alignment amount V _iwith vectorial V _i-1intersection point be C _i-1, make vectorial V _i-1=vectorial V _i, i.e. following formula:

$\left\{\begin{array}{c}{V}_{i-1}=P_{i-1,j}+n_{i-1}{t}_{i-1}\\ V_i=P_{i,j}+n_i{t}_i\end{array}\right.---\left(8\right),$

T _i-1and t _ibe respectively vectorial V _i-1with vectorial V _iargument, i.e. t _ipoint P _i,jto a C _ilength;

P _i,jbe expressed from the next:

P _i,j＝P _i,j-1+λ _iv _i,j(9)，

λ _ifor vector mould;

Formula (5) (7) (9) are substituted in (6), draws n _iwith parameter lambda _imonotropic function, substitute in formula (8), with t _i-1and t _ifor unknown number, obtain function:

$t_i=\frac{P_{i-1,j}\left(z\right)+n_{i-1}\left(z\right)\left(P_{i,j-1}\right(y)+{\mathrm{\λ}}_i{v}_{i,j}(y)-P_{i-1,j}(y\left)\right)}{n_{i-1}\left(y\right)}-\frac{P_{i,j-1}\left(z\right)+{\mathrm{\λ}}_i{v}_{i,j}\left(z\right)}{n_i\left(z\right)-n_{i-1}\left(z\right)n_i\left(y\right)/n_{i-1}\left(y\right)}---\left(10\right);$

Point C _i-1coordinate be:

C _i-1＝P _i,j+n _it _i(11)；

Formula (10) is substituted in (11) and draws a C _i-1coordinate, then will C be put _i-1coordinate and formula (9) substitute into formula (12), can λ be tried to achieve _ivalue, by λ _ivalue substitute into formula (9), can P be tried to achieve _i,jcoordinate;

Table 1 is the relevant parameter of a secondary mirror, secondary mirror and receiver in test one,

Table 1

The outer radii r of condensation photovoltaic cell panel is drawn by formula 1 _maxfor 0.5m.

The coordinate of 100 points in secondary mirror is finally tried to achieve in table 2 by above-mentioned formula:

Table 2

Three, secondary mirror curved surface is drawn: by P _i,jcoordinate adopt non-homogeneous B spline curve to connect reconstruct to obtain secondary mirror free curve, draw secondary mirror free curve, a secondary mirror and receiver with the three-dimensional constructing function of graphics software, curve is rotated around z-axis, obtain three-dimensional free surface.

Test two: the geometric concentrating ratio that this test is condensation photovoltaic subsystem with the difference of test one is 60suns, other known quantity is all the same.

Test three: this test and the difference of test two are receiver distance one secondary mirror 3m, and other known quantity is all the same.

Fig. 5 is the light transmission path profile of test two, 2 is secondary mirror, Fig. 6 is the light transmission path profile of test three, 2 is secondary mirror, as can be seen from the figure secondary mirror free form surface recessed-convexity depends primarily on the height of receiver, after the reflection of secondary mirror free form surface, collected light is divided into two parts, a part is collected at center and a bit uses as high-temperature hot conversion, another part is evenly distributed on receiver surrounding and changes for condensation photovoltaic, along with the increase of receiver height, secondary mirror scope of freedom mirror convexly transfers fovea superior to by lower gradually.In addition, because the size of condensation photovoltaic cell panel is fixed, along with the increase of receiver height, light splitting transitional region is made to become more obvious.

Fig. 7 is receiver focusing energy stream cloud charts in test one, 3 is condensation photovoltaic cell panels, 4 is heat dumps, 6 is centers of circle of heat dump, light-colored part to flow stronger region, and black to flow more weak region, and as can be seen from the figure all ray vectors distributions all coincide with setting target vector, namely focusing energy stream in center converges in the initial point of heat dump, and condensation photovoltaic cell panel obtains energy flow point cloth then completely evenly.Because all heat dump intended recipient vectors all accurately will converge at round dot, it is very high that peak value can be flowed in Shi Qi center.

Because the free minute surface of secondary exists deviation at the law vector of transitional region, even if for spot light, the light splitting transition region on receiving plane still can receive a part of light, but the loss of this part is little, negligible.

Claims (5)

1. the scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity, it is characterized in that the scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity adopts scope of freedom type Cassegrain to reflect lens system, be made up of a secondary mirror (1), secondary mirror (2) and receiver; One secondary mirror (1), secondary mirror (2) and receiver are all axially symmetric structures, and a secondary mirror (1), secondary mirror (2) and receiver three are coaxial; One secondary mirror (1) is connected by support (5) with secondary mirror (2), the concave surface of one secondary mirror (1) is towards secondary mirror (2), receiver is fixed on support (5), and support (5) is arranged on the axis of a secondary mirror (1), secondary mirror (2) and receiver three; Receiver is made up of heat dump (4) and condensation photovoltaic cell panel (3) and flange, flange is arranged on the optical window end of heat dump (4), condensation photovoltaic cell panel (3) is arranged on the outside of flange, and the optical window of heat dump (4) is towards secondary mirror (2); Heat dump (4) is cylindrical, and condensation photovoltaic cell panel (3) is hollow ring;

One secondary mirror adopts traditional solar energy dish-style parabolic mirror, and secondary mirror is the mirror surface of a free form surface form, and the determination mode of the free form surface of secondary mirror is as follows:

One, initial sum impact point is discrete:

Determine the size of a secondary mirror and receiver, computing formula is as follows:

w(R _max ²-R _min ²)/C _G＝(r _max ²-r _min ²)(1)，

W is the occupation ratio of condensation photovoltaic subsystem, C _gthe geometric concentrating ratio of condensation photovoltaic subsystem, R _maxthe outer radii of a secondary mirror, R _minthe inner radii of a secondary mirror, r _maxthe outer radii of condensation photovoltaic cell panel in receiver, r _minthe inner radii of the condensation photovoltaic cell panel in receiver, R _min>=r _max, wherein five is known quantity, can obtain the 6th amount, determine the size of a secondary mirror and receiver;

Set up three-dimensional cartesian coordinate system (x, y, z), initial point O is the intersection point of support and a secondary mirror, z-axis is pointed to the axis in secondary mirror direction, y-axis be parallel to condensation photovoltaic cell panel in receiver radius and point to the axis in condensation photovoltaic cell panel direction by initial point, x-axis be through initial point O and with the axis of z-axis and y-axis place plane orthogonal, only getting z-axis and y-axis is that the region of positive number calculates;

A secondary mirror is got n some P _{i, j-1}, n is positive integer, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of n point, and i is positive integer, and No. 1 is that on a secondary mirror, y-axis coordinate value equals R _maxpoint, No. n is that on a secondary mirror, y-axis coordinate value equals R _minpoint, sequence number i progressively increases along No. 1 to No. n, y _{i, j-1}be the coordinate value in y-axis in this n point, computing formula is as follows:

y _i，j-1＝Y _1，j-1-(i-1)×(y _1，j-1-Y _n，j-1)/n(2)；

Point P _{i, j-1}z-axis coordinate adopt formula z=y ²/ 4f calculates, and f is the focal length of a secondary mirror;

Determine point optical node P on a secondary mirror _{k, j-1}, calculate its y-axis coordinate value y _{k, j-1}, computing formula is as follows:

$\begin{array}{cc}{y}_{k,j-1}=\sqrt{(1-w){R_{\max }}^2+{{\mathrm{wR}}_{\min }}^2}& \left(3\right),n>k>1\end{array},$

If the n got on a secondary mirror some P _{i, j-1}do not comprise a point optical node P _{k, j-1}, then a y-axis coordinate value and Y is looked in n point on a secondary mirror _{k, j-1}immediate some P _{i, j-1}as a point optical node P _{k, j-1};

Get m some P on the receiver _{i, j+1}, m is positive integer and m=n, and the difference of the y-axis coordinate value of all adjacent two points is equal, and i is the sequence number of m point, and i is positive integer, and No. 1 is that on receiver, y-axis coordinate value equals r _maxpoint, sequence number i progressively increases along No. 1 to No. m, y _{i, j+1}the coordinate value in y-axis in this m point, Y _{k, j+1}equal r _min, the y of remaining m-1 point _{i, j+1}computing formula is as follows:

Y _{i, j+1}=Y _{1, j+1}-(i-1) × (y _{1, j+1}-Y _{n, j+1}during)/m, i≤k

(4)；

Y _{i, j+1}during=0, i > k

Two, the solving of secondary mirror free form surface discrete point:

Setting P _{i, j}the point P on a mirror is mapped to for solar irradiation _{i, j-1}reflex to point corresponding in secondary mirror, θ _ifor P _{i, j}corresponding reflection half-angle, θ _iaccount form as follows:

${\mathrm{\θ}}_i=\frac{1}{2}{\cos }^{-1}(-v_{i,j}\·v_{i,j+1})---\left(5\right),$

V _{i, j}and v _{i, j+1}representation vector respectively and vector unit vector;

N _ifor a P _{i, j}normal vector, n _iobtained by following formula:

Matrix Rot (x, θ _i) be:

$Rot(x,{\mathrm{\θ}}_i)=\left[\begin{array}{cccc}1& 0& 0& 0\\ 0& {\mathrm{cos\θ}}_i& {\mathrm{sin\θ}}_i& 0\\ 0& -{\mathrm{sin\θ}}_i& {\mathrm{cos\θ}}_i& 0\\ 0& 0& 0& 1\end{array}\right]---\left(7\right);$

Point P _{1, j}coordinate be known quantity, its normal vector n ₁also can obtain accordingly,

Normal vector n _ireverse extending line be vectorial V _i, adjacent two normal vector n _iand n _i-1corresponding reverse extending alignment amount V _iwith vectorial V _i-1intersection point be C _i-1, make vectorial V _i-1=vectorial V _i, i.e. following formula:

$\left\{\begin{array}{c}{V}_{i-1}=P_{i-1,j}+n_{i-1}{t}_{i-1}\\ V_i=P_{i,j}+n_i{t}_i\end{array}\right.---\left(8\right),$

T _i-1and t _ibe respectively vectorial V _i-1with vectorial V _iargument, i.e. t _ipoint P _{i, j}to a C _ilength;

P _{i, j}be expressed from the next:

P _i，j＝P _i，j-1+λ _iv _i，j(9)，

λ _ifor vector mould;

Formula (5) (7) (9) are substituted in (6), draws n _iwith parameter lambda _imonotropic function, substitute in formula (8), with t _i-1and t _ifor unknown number, obtain function:

$t_i=\frac{P_{i-1,j}\left(z\right)+n_{i-1}\left(z\right)\left(P_{i,j-1}\right(y)+{\mathrm{\λ}}_i{v}_{i,j}\left(y\right)-P_{i-1,j}\left(y\right))}{n_{i-1}\left(y\right)}-\frac{P_{i,j-1}\left(z\right)+{\mathrm{\λ}}_i{v}_{i,j}\left(z\right)}{n_i\left(z\right)-n_{i-1}\left(z\right)n_i\left(y\right)/n_{i-1}\left(y\right)}---\left(10\right);$

Point C _i-1coordinate be:

C _i-1＝P _i，j+n _it _i(11)；

Formula (10) is substituted in (11) and draws a C _i-1coordinate, then will C be put _i-1coordinate and formula (9) substitute into formula (12), can λ be tried to achieve _ivalue, by λ _ivalue substitute into formula (9), can P be tried to achieve _{i, j}coordinate;

Three, secondary mirror curved surface is drawn: by P _{i, j}coordinate adopt non-homogeneous B spline curve to connect reconstruct to obtain secondary mirror free curve, draw secondary mirror free curve, a secondary mirror and receiver with the three-dimensional constructing function of graphics software, curve is rotated around z-axis, obtain three-dimensional free surface.

2. a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity according to claim 1, is characterized in that described receiver is arranged on the point of intersection of support (5) and a secondary mirror (1).

3. a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity according to claim 1, is characterized in that described receiver is arranged on 1/4 place that support (5) is above support (5) length with a secondary mirror (1) distance.

4. a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity according to claim 1, is characterized in that described receiver is arranged on 1/3 place that support (5) is above support (5) length with a secondary mirror (1) distance.

5. a kind of scope of freedom Opticai Concentrating System With Secondary Reflection efficiently changed for solar heat/electricity according to claim 1, is characterized in that described receiver is arranged on 1/2 place that support (5) is above support (5) length with a secondary mirror (1) distance.