Nonimaging solar collector/concentrator

Abstract

A non-imaging solar collecting and concentrating apparatus for use in i.e., passive lighting and solar power applications that is relatively immune from optical incidence angle(s) and therefore does not need to track the movement of the sun to efficiently collect and concentrate solar energy. The apparatus includes a non-planar support structure having a sun-facing entrance and an energy-outputting exit. An interior surface of the structure includes a graded-index structure(s) and/or diffraction grating(s) to enhance the collection and concentration efficiency.

1 . An apparatus for collecting solar or other optical radiation comprising: 
 a curved support structure, defining an interior surface; and    a graded-index medium, disposed throughout the interior of the curved support structure;    such that light rays striking the interior surface of the curved support structure are directed to a common point, said common point being substantially a focal point of the curved surface.    
   
   
       2 . The apparatus of  claim 1 , further comprising: 
 a substantially reflective surface, surrounding the graded-index medium and disposed on the interior surface of the curved support structure.    
   
   
       3 . The optical apparatus of  claim 2 , wherein the interior surface comprises a diffractive grating.  
   
   
       4 . The optical apparatus of  claim 3 , wherein the diffraction grating has between 100 and 2000 grating lines/mm.  
   
   
       5 . The optical apparatus of  claim 3  where the diffraction grating is blazed or otherwise engineered such that the diffraction to the common point is enhanced.  
   
   
       6 . The optical apparatus of  claim 4  wherein the diffraction grating is a binary or step grating having a set of step width, height, and/or spacing variations.  
   
   
       7 . The optical apparatus of  claim 2  further comprising a lens or transmission grating, overlying the curved support structure.  
   
   
       8 . The optical apparatus of  claim 3  wherein the curved support structure is one selected from the group consisting of: a conic parabolic concentrator (CPC), a simple power series concentrator including cubic, quartic, or quintic; a conic exponential concentrator (CEC), a conical shaped concentrator, a straight cone shaped concentrator, a bulb shaped concentrator, and mixed-geometry shaped concentrators.  
   
   
       9 . The optical apparatus of  claim 3  wherein the concentrator exhibits a radial profile defined by: 
         r ( z )= a+bz   n   
     where a and b are constants determining the entrance aperture radius and the exit aperture radius, z is the axial coordinate, and n is a real number.  
   
   
       10 . The optical apparatus of  claim 4  wherein the diffraction grating is a grating superstructure or quasi-regular array of optical scatterers.  
   
   
       11 . A method of collecting solar or other optical energy comprising the steps of: 
 receiving the optical energy on a substantially non-planar structure having a diffractive surface for receiving the optical energy;    diffracting the optical energy to a collecting point; and    collecting the optical energy into a collector positioned at the collecting point.    
   
   
       12 . The method of claim further comprising the steps of reflecting a portion of the solar energy toward the collecting point.  
   
   
       13 . The method of  claim 11  wherein said diffracting step is performed through the effect of a diffractive grating.  
   
   
       14 . The method of  claim 13  wherein said diffractive grating has between 100 and 2000 grating lines/mm.  
   
   
       15 . The method of  claim 11  wherein said diffractive grating is a blazed grating or otherwise engineered such that the diffraction to the common point is enhanced.  
   
   
       16 . The method of  claim 11  wherein said diffractive grating is a binary or step grating having a set of step width, height, and/or spacing variations.  
   
   
       17 . The method of  claim 11  wherein the diffraction grating is a grating superstructure or quasi-regular array of optical scatterers.  
   
   
       18 . The method of  claim 11  further comprising the steps of focusing or directing, through the effect of a lens or transmission grating positioned between the non-planar structure and the optical energy, the optical energy into/onto the diffractive surface.  
   
   
       19 . The method of  claim 11  wherein the curved support structure is one selected from the group consisting of: a conic parabolic concentrator (CPC), a simple power series concentrator including cubic, quartic, or quintic; a conic exponential concentrator (CEC), a conical shaped concentrator, a straight cone shaped concentrator, a bulb shaped concencentrator, and a mixed-geometry shaped concentrator.  
   
   
       20 . An optical collector/concentrator comprising: 
 a curved, means for supporting a diffractive surface wherein said curved supporting means defines an interior surface; and    a means for diffracting light rays, disposed upon the supporting means of the curved support structure;    such that light rays striking the interior surface of the curved support means are directed to a common point, said common point being substantially a focal point of the curved support means