U.S. patent application number 12/286688 was filed with the patent office on 2009-04-02 for aligned multiple flat mirror reflector array for concentrating sunlight onto a solar cell.
Invention is credited to Jinchun Xie.
Application Number | 20090084375 12/286688 |
Document ID | / |
Family ID | 40506791 |
Filed Date | 2009-04-02 |
United States Patent
Application |
20090084375 |
Kind Code |
A1 |
Xie; Jinchun |
April 2, 2009 |
Aligned multiple flat mirror reflector array for concentrating
sunlight onto a solar cell
Abstract
An aligned multiple flat mirror reflector array for
concentrating sunlight onto a solar cell is disclosed. The
reflector array includes a concentrating dish and a plurality of
flat mirrors disposed on an inside surface of the concentrating
dish, the plurality of flat mirrors being disposed and aligned on
the inside surface of the concentrating dish such that sunlight
impinging upon each of the plurality of flat mirrors is reflected
upon the solar cell.
Inventors: |
Xie; Jinchun; (Redwood City,
CA) |
Correspondence
Address: |
SCHEIN & CAI LLP
111 W. ST. JOHN ST., SUITE 1250
SAN JOSE
CA
95113
US
|
Family ID: |
40506791 |
Appl. No.: |
12/286688 |
Filed: |
September 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60997253 |
Oct 1, 2007 |
|
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|
Current U.S.
Class: |
126/684 |
Current CPC
Class: |
F24S 23/77 20180501;
F24S 23/80 20180501; Y02E 10/47 20130101; F24S 30/452 20180501;
H01L 31/0547 20141201; Y02E 10/52 20130101 |
Class at
Publication: |
126/684 |
International
Class: |
F24J 2/10 20060101
F24J002/10; F24J 2/12 20060101 F24J002/12; F24J 2/16 20060101
F24J002/16 |
Claims
1. A solar reflector array for concentrating sunlight onto a solar
cell comprising: a concentrating dish; and a plurality of flat
mirrors disposed on an inside surface of the concentrating dish,
the plurality of flat mirrors being disposed and aligned on the
inside surface of the concentrating dish such that sunlight
impinging upon each of the plurality of flat mirrors is reflected
upon the solar cell.
2. The solar reflector array of claim 1, wherein the solar cell is
disposed a distance from a center of the concentrating dish.
3. The solar reflector array of claim 1, wherein the concentrating
dish is tiltable about a first axis and rotatable about a second
axis perpendicular to the first axis.
4. The solar reflector array of claim 3, wherein the concentrating
dish is mounted to a support frame tiltable about the first
axis.
5. The solar reflector array of claim 1, wherein the concentrating
dish has a parabolic profile.
6. The solar reflector array of claim 1, wherein the concentrating
dish has a spherical profile.
7. A solar reflector array for concentrating sunlight onto a solar
cell comprising: a concentrating dish; and a plurality of panels
disposed on an inside surface of the concentrating dish, the
plurality of panels being disposed and aligned on the inside
surface of the concentrating dish such that sunlight impinging upon
each of the plurality of panels is reflected upon the solar cell,
each of the plurality of panels comprises a plurality of flat
mirrors.
8. The solar reflector array of claim 7, wherein the solar cell is
disposed a distance from a center of the concentrating dish.
9. The solar reflector array of claim 7, wherein the concentrating
dish is tiltable about a first axis and rotatable about a second
axis perpendicular to the first axis.
10. The solar reflector array of claim 9, wherein the concentrating
dish is mounted to a support frame tiltable about the first
axis.
11. The solar reflector array of claim 7, wherein each of the
plurality of panels is adjustably mountable to a support structure
comprising an inner ring and an outer ring, a first of the
plurality of panels being mountable to three contact points of the
inner ring, and each of the remaining plurality of panels being
mountable to a contact point of the inner ring and two contact
points of the outer ring.
12. The solar reflector array of claim 11, wherein the inner ring
has a smaller diameter than the outer ring and the outer ring is
disposed in a plane above that of the inner ring relative to a tilt
axis of the concentrator dish.
13. A solar reflector array for concentrating sunlight onto a solar
cell comprising: a flat concentrating platform; and a plurality of
flat mirrors disposed on a surface of the flat concentrating
platform, the plurality of flat mirrors being disposed and aligned
on the flat surface of the concentrating platform such that
sunlight impinging upon each of the plurality of flat mirrors is
reflected upon the solar cell.
14. The solar reflector array of claim 13, wherein the solar cell
is disposed a distance from a center of the flat concentrating
platform.
15. The solar reflector array of claim 13, wherein the flat
concentrating platform is tiltable about a first axis and rotatable
about a second axis perpendicular to the first axis.
16. The solar reflector array of claim 15, wherein the flat
concentrating platform is mounted to a support frame tiltable about
the first axis.
17. A method for concentrating sunlight onto a solar cell
comprising the steps of: mounting a plurality of flat mirrors on a
concentrating dish; and tilting and rotating the concentrating dish
about first and second axes respectively such that each of the
plurality of mirrors are aligned to reflect sunlight impinging
thereon upon the solar cell.
18. The method of claim 17, further comprising mounting the solar
cell a distance from a center of the concentrating dish.
19. The method of claim 17, further comprising mounting the solar
cell a distance roughly equal to half the diameter of the
concentrating dish from a center of the concentrating dish.
20. The method of claim 17, wherein mounting the plurality of flat
mirrors on the concentrating dish comprises aligning each of the
plurality of flat mirrors such that incident sunlight is reflected
upon the solar cell.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
119(e) from provisional patent application Ser. No. 60/997,253,
entitled "Aligned Multiple Flat Mirror Reflectors Array To
Concentrate Sunlight Onto Solar Cell", filed on Oct. 1, 2007, the
disclosure of which is herein incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to solar reflector
arrays and more particularly to an aligned multiple flat mirror
reflector array for concentrating sunlight onto a solar cell.
[0003] The use of reflectors for focusing sunlight are well know.
For example, U.S. Pat. No. 6,042,240 entitled "Adjustable Three
Dimensional Focal Length Tracking Reflector Array" discloses a
reflector positioned in orbit about a celestial body to focus
sunlight on objects such as space debris to heat up and vaporize
such debris. The reflector includes a plurality of units in an
array, with each of the units including a plurality of subunits.
Each of the units rotates about a first axis and each of the
subunits is tiltable about a second axis which is perpendicular to
the first axis. A reflecting surface is mounted on each of the
subunits such that the reflecting surface rotates with its
respective unit and tilts with its respective subunit. Each of the
units and each of the subunits is independently controllable.
[0004] U.S. Patent Application Publication No. 2004/0074490
entitled "Solar Energy Reflector Array" discloses a heliostat
comprising a reflector element and a carrier that is arranged to
support the reflector element above a ground plane. A drive means
is arranged to impart pivotal drive to the carrier about a fixed,
first axis that is, in use of the heliostat, disposed substantially
parallel to the ground plane. The heliostat further comprises a
means mounting the reflector element to the carrier in a manner
which permits pivotal movement of the reflector element with
respect to the carrier and about a second axis that is not parallel
to the first axis.
[0005] Known reflector arrays suffer the disadvantage that they are
complex and thus expensive to manufacture and deploy. What is
needed therefore is an aligned multiple flat mirror reflector array
for concentrating sunlight onto a solar cell that is of relatively
simple construction and inexpensive to manufacture and deploy.
SUMMARY OF THE INVENTION
[0006] In accordance with one aspect of the invention, an aligned
multiple flat mirror reflector array for concentrating sunlight
onto a solar cell includes a concentrating dish and a plurality of
flat mirrors disposed on an inside surface of the concentrating
dish, the plurality of flat mirrors being disposed and aligned on
the inside surface of the concentrating dish such that sunlight
impinging upon each of the plurality of flat mirrors is reflected
upon the solar cell.
[0007] In accordance with another aspect of the invention, an
aligned multiple flat mirror reflector array for concentrating
sunlight onto a solar cell includes a concentrating dish and a
plurality of panels disposed on an inside surface of the
concentrating dish, the plurality of panels being disposed and
aligned on the inside surface of the concentrating dish such that
sunlight impinging upon each of the plurality of panels is
reflected upon the solar cell, each of the plurality of panels
comprises a plurality of flat mirrors.
[0008] In accordance with yet another aspect of the invention, an
aligned multiple flat mirror reflector array for concentrating
sunlight onto a solar cell includes a flat concentrating platform
and a plurality of flat mirrors disposed on a surface of the flat
concentrating platform, the plurality of flat mirrors being
disposed and aligned on the flat surface of the concentrating
platform such that sunlight impinging upon each of the plurality of
flat mirrors is reflected upon the solar cell.
[0009] In accordance with another aspect of the invention, a method
for concentrating sunlight onto a solar cell includes the steps of
mounting a plurality of flat mirrors on a concentrating dish, and
tilting and rotating the concentrating dish about first and second
axes respectively such that each of the plurality of mirrors are
aligned to reflect sunlight impinging thereon upon the solar
cell.
[0010] There has been outlined, rather broadly, the more important
features of the invention in order that the detailed description
thereof that follows may be better understood, and in order that
the present contribution to the art may be better appreciated.
There are, of course, additional features of the invention that
will be described below and which will form the subject matter of
the claims appended herein.
[0011] In this respect, before explaining at least one embodiment
of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
design and to the sequence of steps and processes set forth in the
following description or illustrated in the drawings. The invention
is capable of other embodiments and of being practiced and carried
out in various ways. Also, it is to be understood that the
phraseology and terminology employed herein, as well as the
abstract, are for the purpose of description and should not be
regarded as limiting.
[0012] As such, those skilled in the art will appreciate that the
conception upon which this disclosure is based may readily be
utilized as a basis for the designing of other structures and
methods for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent structures and methods insofar as they
do not depart from the spirit and scope of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the drawings:
[0014] FIG. 1 illustrates a perspective view of an aligned multiple
flat mirror reflector array for concentrating sunlight onto a solar
cell in accordance with the invention;
[0015] FIG. 2A illustrates a partial side elevation view of the
reflector array of FIG. 1;
[0016] FIG. 2B illustrates a plan view of a concentrator dish in
accordance with the invention;
[0017] FIG. 2C is a schematic representation of three flat mirrors
of the concentrator dish of FIG. 2B;
[0018] FIG. 3 is a schematic representation of a plurality of flat
mirrors of the concentrator dish of FIG. 2B;
[0019] FIG. 4A illustrates a plan view of a first alternative
concentrator dish in accordance with the invention;
[0020] FIG. 4B illustrates a side elevation view of the
concentrator dish of FIG. 4A;
[0021] FIG. 4C illustrates a panel of the concentrator dish of FIG.
4A;
[0022] FIG. 4D illustrates a side elevation view of the panel of
FIG. 4C;
[0023] FIG. 5A illustrates a second alternative concentrator dish
in accordance with the invention;
[0024] FIG. 5B illustrates a side elevation view of the
concentrator dish of FIG. 5A;
[0025] FIG. 6A illustrates an expanded view of a corner panel of
the concentrator dish of FIG. 5A;
[0026] FIG. 6B illustrates a side elevation view of the corner
panel of FIG. 6A;
[0027] FIG. 7A illustrates a third alternative embodiment of the
concentrator dish in accordance with the invention;
[0028] FIG. 7B illustrates a side elevation view of the
concentrator dish of FIG. 7A;
[0029] FIG. 8 is a schematic representation of a plurality of flat
mirrors of the concentrator dish of FIG. 7A;
[0030] FIG. 9 is a schematic representation of a flat mirror in
relation to a solar cell in accordance with the invention;
[0031] FIG. 10A illustrates a reflected image on the solar cell in
accordance with the invention;
[0032] FIG. 10B is a graph showing a light intensity distribution
in accordance with the invention;
[0033] FIG. 11 is a table showing the relationship between mirror
tilt angle and mirror width, reduced width, light projection, void
space and cell width in accordance with the invention; and
[0034] FIG. 12 is a flow chart of a method for concentrating
sunlight onto a solar cell in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] An aligned multiple flat mirror reflector array to
concentrate sunlight onto a solar cell generally designated 100 is
shown in FIG. 1 facing the sun. A concentrating dish 110 is fixedly
attached to a support frame 120 that is in turn tiltably mounted to
a rotatable post 130. Tilting of the concentrating dish 110
(indicated at arrow A) and rotation of the rotatable post 130
(indicated at arrow B) are programmably controlled by motors (not
shown) to enable the concentrating dish 110 to follow the
trajectory of the sun moving across the sky and maintain the
concentrating dish 110 facing the sun. The concentrating dish 110
has a round, concave shape and preferably includes about 1000 flat
mirrors that reflect parallel sunlight rays onto a solar cell 140
disposed above the center of the concentrating dish 110. The
concentrating dish 110 effectively concentrates about 1000 times
the intensity of the incident sunlight onto the solar cell 140.
[0036] With reference to FIG. 2A, the concentrating dish 110 is
shown having a parabolic profile. The concentrating dish 110 is
attached to the support frame 120 that is tiltable about an axis
210. Parallel sunlight rays are reflected onto the solar cell 140
by a plurality of mirrors 220 (FIG. 2B) arranged on the inside
surface of the concentrating dish 110. The solar cell 140 is
supported above the concentrating dish 110 by beams 230 attached to
the support frame 120.
[0037] With reference to FIG. 2B, the concentrating dish 110 is
shown having a round structure. 1064 square mirrors 220 are closely
distributed on the inside surface of the concentrating dish 110 in
covering relationship thereto and are arranged in vertical and
horizontal lines. As illustrated in FIG. 2C, mirrors 220a, 220b and
220c are aligned in three different directions. Each mirror 220a,
220b and 220c reflects a square projection without focusing the
light, however each mirror's direction is adjusted so that the
light reflected thereby is concentrated at the solar cell 140.
[0038] FIG. 3 illustrates reflection onto the solar cell 140 by
mirrors 300a, 300b, 300c, and mirrors 220a, 220b and 220c. Mirror
300a is disposed perpendicular to the direction of the sun's rays
and reflects the sun's rays perpendicularly to the solar cell 140.
Mirror's 300a, 300c, 220a, 220b and 220c are disposed at an angle
to reflect the sun's rays onto the solar cell 140. To avoid
blockage between mirrors, each mirror's position is raised in
elevation along the extent of the inside surface of the
concentrating dish 110 (represented in FIG. 3 by the curve 310)
beginning with a lowest disposition of mirror 300a and ending with
a highest disposition of mirror 220a. At the same time, the mirrors
are tightly fitted against each other. The curve 310 is preferably
parabolic or spherical in profile.
[0039] A first alternative embodiment of the invention is shown in
FIGS. 4A-4D. A structured concentrating dish 400 includes a support
network 410 for supporting multiple panels 420. The support network
is supported within a tiltable mount structure 415. Each panel 420
includes a 4.times.4 array of flat mirrors 430 angled to face
different directions. Mirrors 430 are mounted to a support 440. At
the corner of each panel 420 is disposed a panel mount hole 450.
Each panel 420 is screwed to elements of the support network 410
utilizing the mount holes 450.
[0040] A 7.times.7 array of panels 420 forms a square array 460
disposed in the middle of the support network 410. Disposed around
the square array 460 are four panels 420 forming a roughly
polygonal network 470 of panels 420. Following assembly of the
structured concentrating dish 400, the 65 panels 420 provide 1040
mirrors 430 operable to reflect the sun's rays to a solar cell (not
shown).
[0041] A second alternative embodiment of the invention is shown in
FIGS. 5A and 5B. A concentrating dish 500 includes seven panels
505, 510, 515, 520, 525, 530 and 535. Panel 505 includes a
12.times.12 array of mirrors mounted to an inner ring 540 at
contact points 540a, 540b and 540c thereof. Panel 510 having 140
mirrors is mounted at contact points 550a and 550b of an outer ring
550 and at contact point 540d of the inner ring 540. Panel 515
having 147 mirrors is mounted at contact points 550c and 550d of
the outer ring 550 and at contact point 540e of the inner ring 540.
Panel 520 having 147 mirrors is mounted at contact points 550e and
550f of the out ring 550 and at contact point 540f of the inner
ring 540. Panel 525 having 140 mirrors is mounted at contact points
550g and 550h of an outer ring 550 and at contact point 540g of the
inner ring 540. Panel 530 having 147 mirrors is mounted at contact
points 550i and 550j of the outer ring 550 and at contact point
540h of the inner ring 540. Panel 535 having 147 mirrors is mounted
at contact points 550k and 550m of the outer ring 550 and at
contact point 540i of the inner ring 540.
[0042] Panel 505 is mounted at three contact points of the inner
ring 540 while each of panels 510, 515, 520, 525, 530 and 535 are
mounted at two contact points of the outer ring 550 and one contact
point of the inner ring 540. This triangular configuration provides
support to the panels and a mechanism to finely align the panels by
adjusting the spacing of the panels relative to the contact
points.
[0043] With particular reference to FIG. 5B, inner and outer rings
540 and 550 are shown forming part of a support structure 560 for
holding the panels 505, 510, 515, 520, 525, 530 and 535 in the
proper orientation.
[0044] The triangular configuration of the second embodiment is
further shown in FIG. 6A. Panel 515 is mounted to the outer ring
550 at contact points 550c and 550d, and to the inner ring 540 at
contact point 540e. Connection between the panel 515 and the
contact point 540e may include bolting the panel 515 to the contact
point 540e by means of bolt 600. Space between the contact point
540e and the panel 515 provides adjustability to the orientation of
the panel 515.
[0045] In accordance with the second embodiment of the invention,
the inner and outer rings 540 and 550 are aligned concentrically
and supported by a support frame 610. To achieve a concave
structure, the outer ring 550 is disposed in a plane above the
inner ring 540 relative to a tilt axis 620.
[0046] A third alternative embodiment of the invention is shown in
FIGS. 7A and 7B. A square concentrating platform 700 includes a
32.times.32 array of mirrors 710 supported by a flat support
structure 720. As shown in FIG. 8, mirrors 710 are disposed on the
support structure 720 at different angles such that the sun's rays
are reflected onto a solar cell 730 disposed a distance H from the
support structure 720. The mirrors 710 are disposed a distance away
from each other to avoid blocking the reflected light from adjacent
mirrors 710 as illustrated by the positions of mirrors 710a, 710b
and 710c. Air conduits 740 may be provided between adjacent mirrors
710 to allow for air flow between adjacent mirrors 710 to thereby
reduce wind drag and provide for a stable structure.
[0047] FIG. 9 illustrates reflection from a representative mirror
900 and projection onto a solar cell 910. To provide a square
projection onto the solar cell 910 having a width d, a projected
beam has a width d=d cos .theta.. The mirror 910 has an effective
width d'=d cos .theta./cos(.theta./2).
[0048] With reference to FIG. 10A, a circular solar cell 1000
includes a square window 1010 coated with an anti-reflection
material to allow transmission of light therethrough. Area 1030 is
coated with a high reflection material to block transmission of
light therethrough. Projections 1020 of light reflected from
mirrors of the concentrating dishes of the invention are
illustrated and the distribution of light intensity on the solar
cell 1000 shown in FIG. 10B. Curve 1040 represents the total solar
power distribution showing a high degree of uniformity across the
solar cell 1000. Curve 1050 represents light intensity of a well
aligned mirror while curve 1060 represents light intensity of a
slightly misaligned mirror. Due to the fact that the reflected
light is not focused by the mirrors, there are no hot spots on the
solar cell 1000 and consequently no overheating or heat damage to
the solar cell 1000.
[0049] In operation, the concentrating dish 110, 400, and 500 and
concentrating platform 700 of the invention is tilted in a vertical
direction and rotated horizontally to face the sun directly.
Tilting of the concentrating dish 110, 400, and 500 and
concentrating platform 700 is achieved by rotating the
concentrating dish 110, 400, and 500 and concentrating platform 700
relative to an axis perpendicular to the rotatable post (rotatable
post 130 in FIG. 1). Such tilting is achieved by means of a motor
(not shown). In similar fashion, a motor (not shown) rotates the
rotatable post. The two axes of rotation provide for tracking of
the sun during each season.
[0050] Each of the concentrating dishes 110, 400, and 500 and
concentrating platform 700 are comprised of a plurality of flat
mirrors. Each mirror reflects an unfocused reflection of incident
sun light onto a solar cell. The reflected light has a same shape
as the mirror. The reflected light from the mirrors overlaps to
enhance the illumination onto the solar cell by the number of
mirrors used.
[0051] With reference to FIG. 3, for the mirror 300c located at
radius r and h from the solar cell 140, the mirror 300c is tilted
at an angle .theta. between the incident and reflected rays. The
angle .theta. is also the projection angle for the reflected ray on
the solar cell 140. The angle .theta. can be calculated from the
dish structure and solar cell position H to be,
.theta.=tan.sup.-1[r/(H-h)]. (1)
The sunlight projection angle on the mirror is .theta./2. With
reference to FIG. 9, to keep the projected light on the solar cell
910 as a d by d square, the width of the mirror 900 having a tilted
axis is reduced to,
d'=d cos .theta./cos(.theta./2). (2)
The length remains unchanged. At the sunlight end,
d''=d cos .theta. (3)
The ray of sunlight at mirror tilt axis is reduced too. Thus in the
central locations of the concentrating dishes, little tilting is
required and the mirrors have a generally square shape. For
locations away from the central location, larger tilting is
required and the effective areas of the mirrors have a rectangular
or diamond shape.
[0052] As shown in FIG. 2A, the concentrating dish 110 includes the
frame support 120 preferably formed of sheet metal or equivalent
material. On the inside surface of the concentrating dish 110, 1000
mirror steps are made by plastic molding or sheet metal deforming.
Each step is made with a specific tilting angle toward the central
solar cell 140 in accordance with equation (1). Flat mirrors 220
are glued on the designed mirror steps. In principle, any flat
mirror can be used. In practice, internal silver coated mirrors are
most preferred. The soda lime glass is a preferred material for
flat mirror glass because it has good solar transmission
characteristics. Sunlight passes through the thin glass and is
reflected by the silver coating in the glass to the solar cell 140.
This provides a great advantage using the internal reflection in
this particular application. The glass is the most durable
protection layer for the mirror coating to last over all weather
conditions outdoors. A dish is manufactured as a whole piece with
support frame 120.
[0053] With reference to FIGS. 4A-4D, the concentrating dish 400
includes a framed network comprising 65 squares to support a
plurality of panels 420. The framed network is joined onto the
mount structure 415. Each mirror 430 of each panel 420 is oriented
in a specific direction when manufactured. On the back side of each
panel 420, there four panel mount holes 450 are disposed at the
corners thereof. Each panel 420 has a rigid structure with sheet
metal forming a back plate. Each panel 420 is made for its specific
location on the concentrating dish 400 and can be installed in the
field. This embodiment provides for simplified transportation and
installation procedures.
[0054] The second embodiment of the invention shown in FIGS. 5A and
5B and in FIGS. 6A and 6B includes 1064 mirrors divided into 7
panels 505, 510, 515, 520, 525, 530 and 535, three panels 505, 510
and 525 having a near-square shape and disposed in a middle section
of the concentrating dish 500, and four panels 515, 520, 530 and
535 having a near-triangle shape and disposed in top and bottom
sections of the concentrating dish. Each panel 505, 510, 515, 520,
525, 530 and 535 is made on a rigid panel carrier with the mirrors
attached thereto. The panels 505, 510, 515, 520, 525, 530 and 535
are manufactured in a process similar to the process described
above with reference to panels 420. As previously described, each
panel 505, 510, 515, 520, 525, 530 and 535 is mounted to the two
ring mounting structure at 3 contact points. This three point
mounting system advantageously provides for a stable structure and
fine tuning of the alignment of the panel 505, 510, 515, 520, 525,
530 and 535. The two ring structure is simple and can be precisely
made during the manufacture of the concentrating dish 500. The two
rings 540 and 550 are connected to the support structure 560 to
form a strong and rigid structure. In accordance with the second
embodiment of the invention, a simple and durable structure is
provided that reduces the work involved in transporting and
installing the concentrating dish 500.
[0055] The third embodiment of the invention shown in FIGS. 7A and
7B and in FIG. 8 provides a 32.times.32 array of 1024 square
mirrors d 710 distributed on the flat support structure 720. In
this configuration there is provided a space between adjacent
mirrors to avoid one mirror blocking the reflected light of the
adjacent mirror. The minimum space between the edges of two
adjacent mirrors is calculated as
v=d' sin(.theta./2)tan .theta., (4)
where d' is the mirror width described in equation (2) and .theta.
is the angle between incident light and reflected light. For the
flat structure, .theta. is simply calculated as following.
.theta.=tan.sup.-1(R/H). (5)
In case of a tilt angle .theta.=45.degree., the mirror reduced
width d'=0.765d, space v=0.383, d'=0.293d, sunlight projection
d''=0.707d and cell width v+d''=d. The values for other tilt angles
are listed in Table I shown in FIG. 11. As the mirror is tilted,
the space between adjacent mirrors becomes larger and sunlight
projection smaller. The cell width as the sum of the two is
unchanged. The mirrors are distributed in even cells. The spaces
between adjacent mirrors may advantageously be used as air conduits
740 to reduce wind drag. While the shape of the concentrating dish
700 has been described as square, those skilled in the art will
recognize that other shapes are possible including hexagonal,
octagonal or near-round shapes. In addition, mirrors can be grouped
onto pre-mounted panels and the panels installed on the flat
support structure 720 as described above.
[0056] In the above embodiments, on the order of 1000 flat mirrors
are most preferred to achieve on the order of 1000 light
concentration. Other numbers of flat mirrors, such as 100, 500,
1500, and 2000 can be employed to achieve different ratio
concentrations. In one of preferred application, the mirror size is
100.times.100 mm.sup.2 and 1000 mirrors form a concentrating dish
covering a 10 m.sup.2 area. In another preferred application, the
concentrating dish can be made of roughly 1000 one square foot
mirrors to cover an area of 1000 ft.sup.2 or 100 m.sup.2. In yet
another preferred application, the concentrating dish can be made
of roughly 1000 1''.times.1'' mirrors to cover an area of 2.5
m.sup.2. For a given concentrating dish, the preferred solar cell
height from the center of the concentrating dish is roughly half of
the diameter of the concentrating dish.
[0057] A method for concentrating sunlight onto a solar cell
generally designated 1200 is shown in FIG. 12. In a first step 1210
a plurality of flat mirrors are mounted on a concentrating dish. In
a second step 1220 the concentrating dish is tilted and rotated
about first and second axes respectively such that each of the
plurality of mirrors are aligned to reflect sunlight impinging
thereon upon the solar cell. The solar cell is preferably mounted a
distance equal to half the diameter of the concentrating dish from
a center of the concentrating dish. Mounting the plurality of flat
mirrors on the concentrating dish comprises aligning each of the
plurality of flat mirrors such that incident sunlight is reflected
upon the solar cell.
[0058] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *