Solar concentrator array

A solar concentrator panel having an array of off axis cylindrical parabolic mirrors with an optical design of relatively short focal length solar cells arranged in line that converts sunlight to electricity. The back surface of the mirrors are used as the solar cell mount and the heat sink for the adjacent mirror. By appropriate positioning of the adjacent mirror so that the focal line of the parabola falls within the boundary or rim of the mirror reflected solar light can be directed to the solar cell mounted on the back of the adjacent mirror and converted to electricity

BACKGROUND OF THE INVENTION 
The present invention relates generally to an improvement in photovoltaic 
concentrator arrangements for space applications and more particularly, 
but not by way of limitation, to a space deployable system to convert 
solar energy into electrical energy by directing concentrated solar energy 
onto photovoltaic solar cells which convert this solar energy into 
electrical energy and more particularly, to an array of concentrator 
elements wherein the solar mirror reflectors use the back surface of 
adjacent mirror reflector to support their associated solar cells and act 
as an integral heat sink for said cells. 
A number of photovoltaic arrangements for converting sunlight into 
electricity have been proposed for space applications. For example, the 
proposed space station generally discloses large planar photovoltaic cell 
arrays that extend from each side of a support structure in an opposed 
arrangement. The present proposed planar photovoltaic arrangements clearly 
could be improved by an arrangement which would be more compact and have 
higher energy output per square foot of occupied surface. The present 
invention is believed to overcome the shortcomings of the previously known 
planar photovoltaic cell arrangement for space applications while 
providing a number of advantages over those previously known planar 
photovoltaic cell arrangements. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention contemplates a plurality of spaced 
apart cylindrical off axis parabolic mirror elements that are positioned 
adjacent to each other. The back of each mirror element is positioned so 
that the focal line of the next adjacent mirror is on the back surface of 
that mirror where the photovoltaic solar cell assembly positioned thereon 
receives that focused light and the mirror structure is designed to 
provide a heat sink effect for each mirror and the solar cell assembly. 
The combination reflector, heat sink and solar cell mount, which resembles 
a Venetian blind slat, can easily be fabricated to require tolerances 
through a number of means, including extrusion of a metal part, 
roll-forming, slip rolling, machining, and electroforming. 
An additional advantage of the design is that the mirror backside upon 
which is mounted the solar cell assembly also can be used as a waste-heat 
emitting radiator, further combining functions and eliminating the need 
for a separate radiator component. 
A further advantage of the design is that the mirror facing and backing the 
solar cell assembly can prevent or diminish the effects of 
electromagnetic, particulate (electrons, protons, etc.), and off-axis 
laser irradiation from accessing the solar cell through shielding and 
baffling of the solar cell by the mirror bulk material. 
An object of this invention is to provide a photovoltaic solar electric 
producing array that occupies a smaller given area of space than existing 
photovoltaic arrays for the energy produced thereby. 
Another object of this invention is to produce a photovoltaic solar 
electric producing array that can prevent or diminish the effects of 
electromagnetic, particulate, and off axis-laser irradiations from 
accessing the solar cell through shielding and baffling of the solar cell. 
Further objects, features and advantages of the invention will be evident 
from the detailed description, when read in conjunction with the 
accompanying drawings which illustrate the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
FIG. 1 depicts a single reflector 10 of the present invention. The 
reflector has an off axis parabolic contoured reflective surface 12 and a 
bottom surface (backside) 14 that may also have a reflective surface 16 
thereon, hereinafter explained in more detail. A mounting slot 18 is 
provided on the bottom surface (backside) 14 for receiving a solar cell 
assembly therein. The solar cell assembly fits within slot 18 with its 
outer surface flush with the bottom surface of the reflector forming a 
smooth continuation of the bottom surface. The mirror has a generally 
thick bulk to act as a heat sink hereinafter discussed. 
FIG. 2 depicts a cross-sectional showing view of an array of concentrator 
elements. Only three concentrator elements are shown for ease of 
explanation. It should be understood that any convenient number of 
additional concentrator elements may be added to the array shown, limited 
only by the required electricity produced therefrom and the area available 
for their placement. FIG. 2 shows the off-axis parabolic front surface 12, 
the solar cell assembly 20, the variation of the thickness through the 
reflector as indicated along the reflector between arrows 22 and 24 which 
allows for appropriate heat sinking, although a constant thickness 
reflector could also be utilized. 
Incoming light, shown by broken arrows 26 reflects off of the front surface 
12 of the reflector panel 10 and is concentrated onto the surface of the 
photovoltaic solar cell 20. The arrows 28 show the flow of heat from the 
solar cell 20 through the body of the reflector panel 10. Wavy arrows 30 
show the emission of waste heat by radiation to space off of the reflector 
panel. 
The contour of the surface 12 of the reflector panel 10 follows the 
equation Y=0.115X 2, where Y and X are given in centimeters and X ranges 
from 0.5 to 5.0. With this curvature, the focus of the parabola is at the 
coordinate point (0, 2.174) so that the ratio of focal distance to 
aperture diameter (F/d) of this design is approximately 0.5 centimeters. 
Other curvatures and F/ds could be used, although the above curvature is 
optimized for the purpose intended. The scaling of the parabola is also to 
provide sufficiently short path lengths for thermal conduction to the 
needed emissive area. 
Increasing the F/d moves the solar cell assembly position up the panel 
bottom surface (backside) and reducing the F/d positions the solar cell 
assembly down the solar panel bottom surface (backside). The variations of 
the F/d are used to ideally position the solar cell assemble on the panel 
bottom surface 14 for the purpose intended. 
While the drawing FIG. 2 shows the waste heat being rejected off the bottom 
surface 14 of the panel 10, a separate radiator plate attached to mirror 
16 could also be used. The advantage of using a separate radiator is that 
it would allow the mirror back surface (backside) 14 to be reflective, 
rather than emissive, in the infrared spectral region. This feature has 
benefits for laser survivability of this design since absorption of 
infrared lasers would not occur near the solar panel assembly. 
As aforementioned, while the drawing FIG. 2 shows an array of three 
concentrator elements, any number of panels can be placed in a row of 
panel-cells. The number of rows of panel-cells can be built up into 
two-dimensional arrays of elements to provide higher power levels. 
The various components of the photovoltaic panels of the invention are 
chosen to be suitable for the purposes intended. 
While specific embodiments of the photovoltaic panels have been shown and 
fully explained above for the purpose of illustration it should be 
understood that many alterations, modifications and substitutions may be 
made to the instant invention disclosure without departing from the spirit 
and scope of the invention as defined by the appended claims.