Patent Publication Number: US-2012024374-A1

Title: Solar energy concentrator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-in-Part of pending U.S. patent application Ser. No. 12/572,913, published as 2010/0108124, filed Oct. 2, 2009, the entire contents whereof are incorporated into this application by reference herein and this application claims priority to U.S. Provisional Application Ser. No. 61/403,853, filed Sep. 22, 2010, the entire contents whereof are incorporated into this application by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to solar panels used to generate electrical or thermal power. More specifically the present invention relates to solar panels comprising an array of solar concentrators utilizing photovoltaic cells to generate electrical power. 
     BACKGROUND OF THE INVENTION 
     Concentrators for solar energy have been in use for many years. These devices are used to focus the sun&#39;s energy into a small area to raise the power level being concentrated on a photovoltaic cell to generate electrical power directly, or on a fluid line to heat water to make steam to drive a turbine to generate electrical power. 
     One difficulty with these concentrators has been that they are generally large and bulky and are not suitable for residential applications or other locations where the aesthetics of the installation are of importance. Additionally they are very susceptible to environmental damage due to wind and other elements. 
     In a common implementation a refractive or reflective lens is used to focus the energy on a small photovoltaic cell. An example of a refractive device 100 is presented in FIG. 1 and shows a refractive lens 104 concentrating solar illumination 108 on a photovoltaic cell 112. This simple device concentrates light in a manner similar to the child&#39;s experiment wherein sunlight passing through a magnifying glass is focused onto a sheet of paper, thus setting it alight. Arrays of these are ganged together to generate greater amounts of power. An example of a reflective solar concentrator device 200 previously disclosed in FIG. 3 of U.S. Pat. No. 4,177,083, the contents whereof are incorporated by reference, is presented in FIG. 2. The optical principle is identical to that of a Cassegrain telescope first made known in the seventeenth century, with an energy conversion device replacing the eyepiece. Specifically, solar illumination 204 enters the device 200 and is reflected off of a main reflector 208 to a sub-reflector 212. The sub-reflector 212 reflects the illumination 204 to a photovoltaic cell 216. It suffers from the deficiency that the sub-reflector 212 blocks a substantial portion of the aperture of the main reflector 208 and thus decreases the ability of the device to concentrate light. 
     Stepped wave guides have long been known in the art. In U.S. Pat. No. 5,202,950, Arego et al, and U.S. Pat. No. 5,050,946, Hathaway et al, the contents of which are incorporated herein by reference in their entirety, one inventor of the present invention discloses a faceted light pipe and a light pipe system suitable to backlight a transmissive liquid crystal display from a single side light. In Arego et al, FIG. 8 depicts one embodiment of the light pipe further described in column 6, line 53, to column 7, line 58. FIG. 3 of this document repeats FIG. 8 previously referenced. In FIG. 3 the front surface portion 304 and the rear surface portion 308 of the light pipe 320 are substantially parallel. As stated in Arego et al these surfaces are specular surfaces so as to avoid diffuse reflections or refraction that make control of the light path more difficult. The light facet 312 is oriented at an angle α of 135° from the parallel rear surface portion 308. The light facets 312 are optionally coated with a reflective material 316, stated to be aluminum. The light facet 312 is designed to perform an angle transformation on light propagating in TIR mode within the light pipe 320 to allow that light to exit the light pipe 320 in order to provide illumination for the LCD. 
     FIG. 4 depicts an embodiment of the solar concentrator 400 disclosed in this application. The concentrator 400 includes a mirror assembly 404 to collect and concentrate solar radiation and to direct it to a set of turn mirrors 408 affixed to a stepped wave-guide 412. The turn mirrors 408 are arrayed so as to receive the solar radiation from the mirror assembly 404 and to reflect the solar radiation into the stepped wave-guide 412 at least partially using TIR between a plurality of parallel surfaces. The stepped wave-guide 412 captures the light redirected by the turn mirrors 408 so that the light propagates in TIR mode to a target. A Simple Parabolic Concentrator (SPC) 416 is optionally installed at the end of the propagation path of the stepped wave-guide 412 to further concentrate the captured light. Finally, a photovoltaic cell (PVC) can be affixed to the stepped wave-guide 412 or to the optional SPC 416 at the PVC mounting position 420 to convert the concentrated solar radiation to electrical energy. 
     As shown in FIG. 4, three axes of the system are defined. The longitudinal axis is the long axis of the solar concentrator 400. The transverse axis is the axis across the surface of the solar concentrator 400 orthogonal to the longitudinal axis. The solar axis is the axis orthogonal to the longitudinal and transverse axes and therefore orthogonal to the upper and lower surfaces of the stepped wave-guide 412. 
     Faceted light pipes like those disclosed by Arego, et al., have also been described in solar applications in U.S. Pub. No. 2009/0064993 to Ghosh et al. (Banyan). However, there remains a need for an improved system that can yield higher efficiency and be practically manufactured at a reasonable cost. 
     The cost advantages of a solar concentrator can best be realized if the concentration ratio is high. Highly efficient photovoltaic (PV) cells can efficiently convert a flux density equivalent to many hundreds of suns. Concentration ratios approaching 1000:1 and higher are considered desirable. The concentration goal is best determined after consideration of the technical and cost constraints a solar concentrator system must satisfy. 
     SUMMARY OF THE INVENTION 
     A light concentrator in the form of a relatively thin, planar assembly takes sunlight in at an orientation normal to the planar surface and direct it via a plurality of small linear aspheric or spherical sections into a TIR (total internal reflection) light guide which collects and transports the sunlight from the linear aspheric sections to one edge of the light guide where it illuminates a solar photovoltaic cell or heats water or other medium. The illuminated point may be referred to as an optical target. As is well known in the art of light guides, TIR is the most efficient method for transporting light within a wave-guide. The efficiency of reflection is nominally 100% with the only losses coming from the transmission efficiency of the optical material. Optionally the solar energy may undergo an additional stage of concentration, for example through the use of a Simple Parabolic Concentrator (SPC) or similar device. 
     The concentrator of the present invention can include a plurality of aspheric mirror sections in a first stage, or element of concentration in the system. Each aspheric mirror section concentrates light by illuminating a turn mirror that redirects the light down a wave guide (light pipe) that relies upon Total Internal Reflection (TIR) and geometric optics to contain the light within the wave guide. In this application the wave-guide assembly is not co-extensive with the transverse axis of the mirror assembly but is rather substantially but perhaps not totally centered over the mirror assembly. The wave-guide assembly comprises a single optical assembly with multiple turn mirrors affixed thereto. In a different embodiment the wave-guide assembly comprises a series of loosely coupled optical layers each possessing a turn mirror that is associated with one of the reflector subsections on the mirror assembly. The resulting system will exhibit increased efficiency when the aperture blockage caused the presence of the light guide assembly is exceeded by the increase in efficiency due to the presence of a fully open aperture over the remainder of the reflector assembly. A disadvantage of the solar concentrator of  FIG. 4  is the need to further concentrate light in a second stage along the transverse axis. This reduces the portion of the area of the total assembly over which solar radiation can be collected, thus resulting in the generation of less electrical power per unit area than would be the case if secondary concentration were not otherwise required. 
     A concentrator with very high gain and a method of constructing a concentrator using plastic extrusion and aluminum or silver metallization to produce low cost, thin concentrators with very high gain is described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a known refractive solar concentrator. 
         FIG. 2  depicts a known reflective solar concentrator based on Cassegrain optics. 
         FIG. 3  is a depiction of a wave-guide from the backlight assembly of a flat panel liquid crystal display. 
         FIG. 4  is a previously disclosed solar concentrator. 
         FIG. 5  is an isometric depiction of a solar concentrator system and assembly after the present invention. 
         FIG. 6A  is a plan view of a solar concentrator assembly without the photovoltaic cell assembly 
         FIG. 6B  is a side view of a solar concentrator assembly without the photovoltaic cell assembly. 
         FIG. 7A  is a simplified side view of a solar concentrator assembly 
         FIG. 7B  is a simplified side view of one stage of a solar concentrator assembly. 
         FIG. 7C  is a detailed view of a wave-guide assembly section and associated turn mirror. 
         FIG. 7D  is a perspective depiction of a turn mirror affixed in close proximity to an angled surface at the extremity of a wave-guide segment; 
         FIG. 7E  is a side depiction of a turn mirror affixed in close proximity to an angled surface at the extremity of a wave-guide segment; 
         FIG. 7F  is a simplified side view of a turn mirror affixed in close proximity to an angled surface at the extremity of a wave-guide segment; 
         FIG. 7G  is a simplified side view of a TIR mode ray trace inside a depiction of an external turn mirror affixed to an angled surface at the extremity of a wave-guide segment; 
         FIG. 7H  depicts a simplified side view of a non-TIR ray trace inside a depiction of an external turn mirror affixed to an angled surface at the extremity of a wave-guide segment; 
         FIG. 8A  is a detailed view of a single stage of a solar concentrator assembly. 
         FIG. 8B  is a detailed view of a wave-guide support cradle. 
         FIG. 9A  is a side view of three stages of a solar concentrator assembly after the present invention. 
         FIG. 9B  is a side view of a single stage of a solar contractor assembly 
         FIG. 10A  is an isometric depiction of the upper surface of two reflector assemblies with assembly hardware. 
         FIG. 10B  is an expanded isometric view of a small number of mirror units from two reflector assemblies. 
         FIG. 10C  is an isometric depiction of the under side of two reflector assemblies with assembly hardware. 
         FIG. 11A  is an isometric depiction of a first embodiment of a photovoltaic cell assembly with photovoltaic cell attached 
         FIG. 11B  is a view of a photovoltaic cell. 
         FIG. 11C  is depiction of a photovoltaic cell assembly aligned to be mated to a solar concentrator assembly with light tunnels affixed thereto. 
         FIG. 11D  is a view of an alternate embodiment of a photovoltaic cell assembly with light tunnel and mounting flange integral thereto. 
         FIG. 11E  depicts the alternate embodiment of  FIG. 11D  mounted to a solar concentrator assembly. 
         FIG. 11F  depicts and alternate configuration of a photovoltaic cell. 
         FIG. 12  is an expanded side view of one wave-guide support and alignment structure. 
         FIG. 13A  presents an exploded view of a solar concentrator assembly unit. 
         FIG. 13B  presents a view of an assembled solar concentrator assembly unit 
         FIG. 14  is a simplified electrical diagram of a plurality of solar concentrator assemblies within a solar concentrator assembly unit. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     In a pending patent application Ser. No. 12/572,306 the inventors of this invention disclose many aspects of the design and fabrication of solar energy concentrators and components thereof, the contents whereof are incorporated into this application by reference in its entirety. 
       FIG. 5  depicts an embodiment of solar concentrator assembly  500  disclosed in this application. The solar concentrator system and assembly  500  includes mirror assembly  510  to collect and concentrate solar radiation and to direct it to a set of turn mirrors  520  affixed to the wave-guide assembly segments  535  (not shown) of wave-guide assembly  530 . The turn mirrors  520  are arrayed so as to receive the solar radiation from the mirror assembly  510  and to reflect the solar radiation into the wave-guide assembly segment  535  to which it is affixed at least partially using TIR between a plurality of surfaces of the layer. The segments  535  of wave-guide assembly  530  capture the light redirected by the turn mirrors  520  so that the light propagates in TIR mode to a target. A photovoltaic cell (PVC) assembly  560  is coupled to wave-guide assembly  530  through light tunnel  620 . 
     Mirror assembly  510  may be made of a choice of materials. Examples include cast metal, plastic molding, and PMMA acrylic. The individual mirror segments may be fabricated separately and then mounted to a suitable frame. 
       FIG. 6A  depicts a plan view of solar concentrator assembly  500 .  FIG. 6A  presents a two-channel system, although those familiar with the art of solar concentrators will understand that each channel is optically separate and a solar concentrator may comprise a fewer or greater numbers of channels. Mirror assemblies  510  comprises eight mirror segments  515  (one example circled) although those familiar with the art of solar concentrators will understand that a mirror assembly may comprise a fewer or greater number of mirror segments. Two instances of wave-guide assembly  530  are depicted, each comprised of wave-guide assembly segment  535  (not shown) with a turn mirror  520  affixed that is uniquely associated with one mirror segment  515 . Wave-guide support riser  540  positions each segment  535  of the wave-guide assembly  530  in the correct position to receive solar energy reflected by each mirror segment  515  and additionally supports other wave-guide segments  535  that are above that segment. A photovoltaic cell assembly  560  (not shown) is installed at position  561  to receive the concentrated solar energy and convert said solar energy to electrical energy. 
       FIG. 6A  is rendered to depict a width of mirror assembly  510  along the transverse axis that is far greater than the width of wave-guide assembly  530 . The ratio of these two distances places an upper bound on the geometric concentration ratio along the transverse axis. Computer modeling reveals that a concentration ratio in the range of about 35 to about 40 along the transverse axis is possible. 
       FIG. 6B  presents a side view of solar concentrator assembly  500 . Wave-guide assembly  530  (encircled by the dashed oval) is positioned above mirror assembly  510  by wave-guide support riser  540 . Individual turn mirrors  520  are located above each mirror assembly. A photovoltaic cell assembly  560  (not shown) is attached at mounting position  561 . 
       FIG. 7A  presents a simplified side view of solar concentrator assembly  500 . Wave-guide assembly  530  receives reflected light from a plurality of mirror segments  515  that form mirror assembly  510 . Each mirror segment  515  of mirror assembly  510  is associated with a single wave-guide segment  535  (not shown). A photovoltaic cell assembly (not shown) is mounted at mounting position  561 . 
       FIG. 7B  presents one stage  590  of a solar concentrator assembly  500 . Depicted are single mirror segment  515  and uniquely associated wave-guide segment  535  with turn mirror  520  affixed thereto. Other wave-guide segments  535  are also depicted that are uniquely associated with other mirror segments  515  (not shown). Ray traces A and B depict paths demonstrating the collection of solar radiation by mirror segment  515 , reflection by turn mirror  520  allowing entry into wave-guide segment  535  and subsequent TIR propagation within wave-guide segment  535 . Solar radiation collected by other mirror segments  515  propagates within associated wave-guide segment  535  in parallel to this wave-guide. Because of fresnel losses associated with the series of surfaces associated with wave guide segments  535  of wave-guide assembly  530  (not shown) ray traces A and B in reality are slight in front of or behind the apparent position. 
       FIG. 7C  depicts a piece of a single wave-guide segment  535  with turn mirror  520  affixed thereto. Angle a represents the angle formed between wave-guide segment  535  and the edges of turn mirror  520 . The edges of turn mirror  520  parallel to the transverse axis form a right angle to the longitudinal axis of wave-guide segment. A value for angle α is selected after modeling analysis of the need to present a turn mirror  520  target of sufficient size to capture as much light as possible from mirror segment  515  and reflect those rays of light at an angle sufficient to support TIR within wave-guide segment  535 . In one embodiment angle α is approximately 45°. In another embodiment angle α is approximately 30°. Those of ordinary skill in the art will recognize the utility of other angles in this invention. 
       FIGS. 7D and 7E  present an alternative means of implementing a turn mirror on wave-guide segment  535 . Wave-guide segment  535  includes an angled surface  536  (shown at the right end only) at the end opposite the photovoltaic cell assembly (not shown). A separate turn mirror  537  is affixed to wave-guide  535  in close proximity and parallel to angled surface  536 , preferably with a very small air gap on the order of at least 20 micrometers. Turn mirror  537  including its side tabs is preferably coated with a highly reflective mirror surface. The mirrored surfaces may be realized by sputtering silver or aluminum to the surface of turn mirror  537  or alternatively the surfaces may be coated with a dielectric stack as is well known in the art. The turn mirror is affixed by the tabs to the sides of wave-guide segment  535  by adhesive or other means. 
       FIG. 7F  depicts use on wave-guide segment  535  of a turn mirror  537  separated from the angled surface  536  by a small air gap. Angled surface  536  is substantially parallel to external turn mirror  537 . This facilitates two types of reflection.  FIG. 7G  depicts a ray trace A that satisfies the requirements to reflect from angled surface  536  in TIR mode and then TIR from the surfaces of wave-guide segment  535 . The reflection from angled surface  536  will be at the highest possible efficiency.  FIG. 7H  depicts a ray trace B that does not satisfy the requirements to reflect from angled surface  536  in TIR mode. Ray trace B propagates across the air gap and is reflected by external turn mirror  537 . Reflect ray trace B propagates back across the air gap and re-enters wave-guide segment  535  at angled surface  536 . The refracted ray trace B now satisfies the requirements for TIR reflection and propagates through wave-guide segment  535  in that mode. The reflection from external turn mirror  537  will be of lesser efficiency than a TIR reflection. 
     In a simulation of an implementation of the present system mirror assembly  510  segments  515  are defined in the following data table: 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                 Vertex of 
               
               
                 Mirror 
                 Longitudinal 
                 Transverse 
                 Radius of 
                 Conic 
                 Mirror 
               
               
                 Segment 
                 Length 
                 Width 
                 Curvature 
                 Constant 
                 Location 
               
               
                   
               
             
            
               
                 MS 1 
                 45 
                 45 
                 58.883 
                 −0.964 
                 All mirror 
               
               
                 MS 2 
                 45 
                 45 
                 61.334 
                 −0.964 
                 vertices 
               
               
                 MS 3 
                 45 
                 45 
                 63.835 
                 −0.964 
                 are 
               
               
                 MS 4 
                 45 
                 45 
                 66.335 
                 −0.964 
                 located 
               
               
                 MS 5 
                 45 
                 45 
                 68.836 
                 −0.964 
                 29 mm 
               
               
                 MS 6 
                 45 
                 45 
                 71.336 
                 −0.964 
                 below 
               
               
                 MS 7 
                 45 
                 45 
                 73.837 
                 −0.964 
                 the bottom 
               
               
                 MS 8 
                 45 
                 45 
                 76.337 
                 −0.964 
                 of the 
               
               
                   
                   
                   
                   
                   
                 lowest 
               
               
                   
                   
                   
                   
                   
                 wave- 
               
               
                   
                   
                   
                   
                   
                 guide 
               
               
                   
                   
                   
                   
                   
                 segment. 
               
               
                   
               
               
                 All dimensions are in millimeters. 
               
            
           
         
       
     
     Where MS  1  is located closest to the photovoltaic cell and MS  8  is located at the end opposite the PVC assembly. Radius of curvature and conic constant are used in the following equation. 
     
       
         
           
             z 
             = 
             
               
                 
                   cr 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                          
                         
                           c 
                           2 
                         
                          
                         
                           r 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   ∑ 
                   
                     i 
                     = 
                     1 
                   
                   12 
                 
                  
                 
                   
                     α 
                     i 
                   
                    
                   
                     r 
                     i 
                   
                 
               
             
           
         
       
     
     Each wave-guide segment  535  is fabricated separately. The table below presents data for a set of wave-guide segments  535  and turn mirrors  520  that form a wave-guide assembly  530  to function with the mirror assembly  510  described in the previous table. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Wave-Guide 
                 Longitudinal 
                 Transverse 
                   
                 Turn Mirror 
               
               
                 Segment 
                 Length 
                 Width 
                 Thickness 
                 Angle α 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 WGS 1 
                 27.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 2 
                 67.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 3 
                 112.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 4 
                 157.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 5 
                 202.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 6 
                 247.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 7 
                 292.5 
                 1.25 
                 1.25 
                 45° 
               
               
                 WGS 8 
                 337.5 
                 1.25 
                 1.25 
                 45° 
               
               
                   
               
               
                 All dimensions in mm 
               
            
           
         
       
     
     The reflector mirrors in the example cited above are each rotationally symmetric and formed as a square  45  millimeters on a side. Although nominally possessing identical concentration ratios the presence of the wave-guide assembly over mirror segments MS 1  to MS 7  along the longitudinal axis blocks the entire transverse aperture by a width of 1.25 millimeters and thus reduces the effective aperture available across the transverse axis by 1.25 millimeters. Thus the input aperture is effectively 45 mm×43.75 mm or 1968.75 square millimeters and the output aperture is 1.25 mm square or 1.5625 square millimeters. The ratio of these two factors reveals the limiting effective geometric concentration ratio of this example to be at least 1260. The wave-guide segment above MS  8  extends only half way across and is only one layer thick and therefore presents less of an impediment to the transmission of solar radiation. Therefore the input aperture is 2025 square millimeters. In this case the limiting geometric concentration ratio is 2025 sq mm divided by 1.25 mm squared or 1296. 
       FIG. 8A  depicts a single stage  570  of the solar concentrator. Wave-guide assembly  530  is shown mounted on riser assembly  540 . Wave-guide segment support cradle  550  is mounted on riser base  545 . Riser retention cap  555  is placed over the wave-guide assembly to hold it in place. Rise base  545  is attached to the frame of mirror assembly  510  (partially shown). Assembly alignment fixture  575  and its integral assembly alignment post  580  are mounted over mirror segment  515 . Concentrated solar energy exits the end of the wave-guide assembly to illuminate a PVC assembly  560  (not shown) mounted at point  561 . 
       FIG. 8B  depicts details of wave-guide segment support cradle  550 . Each wave-guide segment  535  is supported by a different wave-guide segment  535  below it. (Only the bottom segment is indicated.) The wave-guide segment at the bottom of wave-guide assembly  530  is supported by wave-guide support cradle  550 . Wave-guide support cradle  550  is mounted on riser base  545 . Riser retention cap  555  is placed over the wave-guide assembly to insure it remains in place during any movement of the solar concentrator assembly  500  (not shown). 
       FIG. 8B  depicts wave-guide segment support cradle  550  as attached to only a single wave-guide segment  535 . This enables wave-guide support cradle  550  to grasp wave-guide segment  535  and thereby control the position of turn mirror  520  (not shown) during thermal expansion and contraction of the various components of solar concentrator assembly  500 . (not shown) Preferably the position of turn mirror  520  (not shown) does not move relative to the center of mirror segment  515 . (not shown) 
       FIG. 8B  depicts wave-guide segment support cradle  550  as being constructed from two assembly sections. This facilitates the manufacturing of the support cradle with support tabs extending vertically from the support arm, which in turn grasps wave-guide segment  535  immediately above it. 
     Those familiar with the physics of TIR will recognize that the points at which the wave-guide segments  535  of assembly  530  are touched by components of wave-guide segment support cradle  550  may cause the TIR condition not to be satisfied which in turn may cause some loss of concentrated solar radiation. Losses at these points can be minimized by affixing a reflective material such as silver or other suitable material to each wave-guide segment  535  at that point or to wave-guide segment support cradle  550  or to both. 
       FIG. 9A  depicts a side view of two stages  570  (one circled) of solar concentrator assembly  500  (not shown). Wave-guide assembly  530  is mounted over mirror assembly  510  such that turn mirror  520  is directly placed over the center of mirror segment  515  (not shown). Wave-guide assembly  530  is supported by wave-guide segment support cradle  550 . Wave-guide segment support cradle is supported by riser base  545 . Wave-guide assembly is held in place by riser retention cap  555 . 
       FIG. 9B  presents a partial view of a single stage  570  of a solar concentrator assembly  500  (not shown). Wave-guide assembly  530  is positioned over a mirror segment  515  (not shown) of mirror assembly  510  such that turn mirror  520  is positioned immediately over the center of mirror segment  515 . Wave-guide segment support cradle  550  is attached to wave-guide segment  535  and is supported by riser base  545 . Riser retention cap  555  holds wave-guide segments  535  of wave-guide assembly  530  in place. 
       FIG. 9B  shows the layers (each wave guide segment  535 ) that comprise wave-guide assembly  530 . Each wave-guide segment  535  is a separate wave-guide that propagates the solar radiation within it to the mounting point closest to photovoltaic cell assembly  600 . Those familiar with the physics of TIR will recognize that some radiation may cross over from one wave-guide segment  535  to another. The wave-guide segments  535  are loosely coupled so crossover between segments can occur. Because of the random nature of any couplings it is expected that this will not adversely affect the uniformity of the concentrated solar radiation at PVC mounting point  561 . 
     In an alternate embodiment of wave-guide assembly  530  the layers may be assembled by optical adhesive to form a single unit. The advantage is improved uniformity but the penalty is that the mirror assembly and the wave-guide assembly may be fabricated of materials with similar coefficients of thermal expansion in the designed thermal operating range. In another alternate embodiment the wave-guide assembly may be fabricated from a single piece of material. 
       FIG. 10A  presents an isometric view of a two-channel mirror assembly structure  510 . Mirror assembly  510  comprises, in this figure, 16 mirror segments  515 , and assembly alignment fixture  575 , including assembly alignment post  580 . Each mirror segment  515  is held in place by fixing means such as adhesive. In an alternate embodiment mirror assembly  510  is formed as a monolithic structure that comprise mirror segments  515 , and assembly alignment fixture  575  including assembly alignment post  580 . The mirror segments  515  on the structure may be coated by sputtering or by deposition. All components of upper side of the structure would thus have a reflective coating that would coincidentally reduce heating due to absorption. 
       FIG. 10B  presents details of a part of mirror segments  515 . Each mirror is surmounted by assembly alignment fixture  575 , including assembly alignment post  580 . By using assembly alignment fixture  575  and assembly alignment post  580  as part of the structure of the mirror assembly  510 , the vertex of each mirror segment  515  is at a predetermined location relative to the alignment post. 
       FIG. 10C  depicts a bottom view of mirror assembly  510 . In the alternate embodiment identified in the teaching of  FIG. 10A  all elements shown in  FIG. 10C  represent a monolithic structure. 
       FIG.11A  depicts photovoltaic cell assembly  600 . Photovoltaic cell assembly  600  comprises heat sink  610  and photovoltaic cell subassembly  630  affixed thereto and second photovoltaic cell  630  subassembly brought forward for added detail.  FIG. 11B  depicts a photovoltaic cell subassembly  630  comprising photovoltaic cell  660 , bypass diodes  670 , cladded ceramic mounting  690  and electrical contacts  680 . Photovoltaic cell assemblies similar to the depiction of  FIG. 11B  are available from several sources on a commercial basis. 
       FIG. 11C  depicts photovoltaic cell assembly  600  aligned for mounting to solar concentrator assembly. Light tunnel  620  is affixed to riser assembly  540  by flange assembly  640  and the ends of wave-guide assembly  530  are aligned so that those ends terminate within light tunnel  620  to insure optimal capture of solar radiation. Photovoltaic cell  660  and photovoltaic cell subassembly  630  are constructed so that the exit end of light tunnel  620  is closely aligned with photovoltaic cell  660 . Assembly may be facilitated by use of appropriately design alignment pins and the like as is well known in the art. 
     Those of ordinary skill in the art will recognize that a wave-guide of constant cross-section does not perform an angle transform upon solar radiation or any other form of light propagating within it in TIR mode and will recall that the range of angles present at the exit of the wave-guide will be the same as the range of angles of the solar radiation that enters it. For a crown glass material with an index of refraction of approximately 1.5 the critical angle (relative to the normal to the material) is 41.8°. Any solar radiation at an angle between 41.8° and 90° to the normal will remain at that angle until it leaves the wave-guide segment. Upon departing the wave-guide segment the beam is refracted to a far greater range of angles with the ultimate limit being 90°. The practical limit is the range of angles in the light reflected from the concentrator mirror relative to the normal to the wave-guide segment as modified by the turn mirror. Therefore as a matter of sound design practice it is important to limit any gaps between light tunnel  620  and photovoltaic cell subassembly  630  to the minimum practical distance. 
       FIG. 11D  depicts another embodiment of a photovoltaic cell assembly  605 . Photovoltaic cell assembly  605  comprises heat sink  615 , photovoltaic cell subassembly  630  with photovoltaic cell  660  affixed thereto, light tunnel  625 , flange mount  645  and support spacers  647 . Photovoltaic cell subassembly  630  is affixed to heat sink  615  and light tunnel  625  is mated to flange assembly  645  which is in turn mated to heat sink  615  by support spacers  647 . The light tunnel is aligned to insure efficient transfer of the solar radiation onto photovoltaic cell  660 . 
       FIG. 11E  presents a view of photovoltaic cell assembly  605  coupled to a solar concentrator assembly after the present invention. Wave-guide assembly  530  is routed through riser assembly  540  into light tunnel  620 . Flange assembly  645  is mounted in close proximity to riser assembly with light tunnel  620  aligned with wave-guide assembly  530 , thus enabling the capture of solar radiation. 
       FIG. 11F  depicts an alternate photovoltaic cell subassembly  631 . Photovoltaic cell subassembly  631  comprises photovoltaic cell  661 , bypass diodes  671 , electrical contacts  681  and ceramic substrate  691 . Photovoltaic cell subassembly  631  offers improvements in two respects. Photovoltaic cell  661  is more closely matched to the dimensions and aspect ratio of the exit of light tunnel  620  and electrical contacts  681  are located above the level of the heat sink to facilitate wiring of the entire assembly after construction. 
       FIG. 12  depicts a means of aligning the turn mirror  520  to the proper point over mirror segment  515 . Alignment jig  590  is inserted onto assembly alignment post  580  and assembly alignment fixture  575 . Wave-guide segment  535  is then adjusted so that turn mirror  520  just touches alignment jig  590 . Wave-guide segment  535  is supported by wave-guide segment support cradle  550 . Wave-guide segment support cradle  550  is supported by riser base  545 . Riser retention cap  555  is installed after all wave-guide segments  535  are installed and aligned. 
     A practical solar energy system will require a significant number of solar energy concentrator assemblies similar to solar energy concentrator assembly  500  shown in  FIG. 5  to produce sufficient electrical energy to be of economic value.  FIG. 13A  depicts an exploded isometric view of a unit of a solar concentrator system  1100  comprising a plurality of solar energy concentrator assemblies  1000  and its associate components to protect it from the elements. The plurality of solar energy concentrator assemblies is inserted into a weather cover frame  1024  and a transparent weather cover  1028  is attached thereto.  FIG. 13B  presents a weatherproof solar energy system unit  1100  based on the components of  FIG. 5  and  FIG. 13A . The individual solar concentrator assemblies are oriented such that the output of each photovoltaic cell is oriented along one axis at the center of the array, thus simplifying the wiring of the array. 
       FIG. 14  depicts a simplified electrical diagram of a solar concentrator system unit comprising a plurality of solar concentrator assemblies  1210 , connected by electrical connection system  1220  to external electrical output point  1230 , located at the periphery of the weather cover frame  1024 . Other locations would be obvious to those of ordinary skill in the art of optomechanical design. The PV cells of an individual solar concentrator assembly may be wired in series, parallel or a combination of the two. The combined output of a solar concentrator system unit may be wired in series, parallel or a combination of the two.