Solar thermal concentrator apparatus, system, and method

Abstract

An apparatus is disclosed including: a trough shaped reflector extending along a longitudinal axis and including at least one reflective surface having a shape which substantially corresponds to an edge ray involute of the absorber.

What is claimed is: 
     
         1 . An absorber for absorbing heat generated due to incident solar light, comprising:
 a hollow double wall structure, said hollow double wall structure comprising:
 an outer transparent tubular enclosure extending along a longitudinal axis from a proximal end to a distal end; and 
 a tubular absorber fin located within the outer transparent tubular enclosure, wherein said outer transparent tubular enclosure is attached to said tubular absorber fin at said proximal end to create an evacuated space between said outer transparent tubular enclosure and said tubular absorber fin; 
   an inner tube disposed within said tubular absorber fin; and   a heat transfer working fluid, wherein said heat transfer working fluid flows through said inner tube from a first end of said inner tube to a second end, and exits through an annular space between the inner tube and the tubular absorber fin in a counter-flow arrangement.   
     
     
         2 . The absorber of  claim 1 , wherein said heat transfer working fluid absorbs heat from the tubular absorber fin and carries said absorbed heat away from said each of said absorbers. 
     
     
         3 . The absorber of  claim 1 , further comprising a plumbing system comprising:
 a pump for pumping said heat transfer working fluid into said absorber;   an input plumbing line for carrying said heat transfer working fluid into said inner tube through said first end; and   an output plumbing line for carrying the heated heat transfer working fluid out of said tubular absorber fin.   
     
     
         4 . The absorber of  claim 1 , wherein said tubular absorber fin comprises a selective surface for absorbing solar light incident through the outer transparent tubular enclosure and convert the solar light to heat. 
     
     
         5 . The absorber of  claim 4 , wherein said heat transfer working fluid enters said inner tube at a first temperature, travels though said inner tube and said tubular absorber fin, absorbs heat from said tubular absorber fin, and exits said tubular absorber fin at a second temperature higher than the first temperature. 
     
     
         6 . The absorber of  claim 4 , wherein said selective surface has an absorptivity between 0.75 and 0.99. 
     
     
         7 . The absorber of  claim 6 , wherein said selective surface exhibits said absorptivity between 150° C. and 200° C. temperature. 
     
     
         8 . The absorber of  claim 4 , wherein said selective surface has an absorptivity of 0.99 or more. 
     
     
         9 . The absorber of  claim 4 , wherein said selective surface has an emissivity between 0.25 and 0.025. 
     
     
         10 . The absorber of  claim 9 , wherein said selective surface exhibits said emissivity between 150° C. and 200° C. temperature. 
     
     
         11 . The absorber of  claim 4 , wherein said selective surface has an emissivity of 0.025 or less. 
     
     
         12 . An apparatus for converting incident solar light to heat, comprising:
 an absorber, said absorber comprising:
 a hollow double wall structure, said hollow double wall structure comprising:
 an outer transparent tubular enclosure extending along a longitudinal axis from a proximal end to a distal end; 
 a tubular absorber fin located within the outer transparent tubular enclosure, wherein said outer transparent tubular enclosure is attached to said tubular absorber fin at said proximal end to create an evacuated space between said outer transparent tubular enclosure and said tubular absorber fin; 
 an inner tube disposed within said tubular absorber fin; and 
 a heat transfer working fluid, wherein said heat transfer working fluid flows through said inner tube from a first end of said inner tube to a second end, and exits through an annular space between the inner tube and the tubular absorber fin in a counter-flow arrangement; 
 
   a reflector disposed proximal to the absorber for reflecting incident solar light onto said absorber.   
     
     
         13 . The apparatus of  claim 12 , wherein said reflector is a trough shaped reflector extending along a longitudinal axis of said absorber, and wherein said trough shaped reflector comprises a pair of reflective surfaces disposed on either side of said absorber. 
     
     
         14 . The apparatus of  claim 13 , wherein:
 each of said absorber is spaced apart from said pair of reflective surfaces by a gap distance; and   a portion of the reflector at the bottom of the trough comprises a reflective cavity having a shape that deviates substantially from an edge ray involute of the absorber.   
     
     
         15 . The apparatus of  claim 14 , wherein the cavity comprises a V-shaped trough extending along the bottom of the reflector in the direction of the longitudinal axis. 
     
     
         16 . The apparatus of  claim 15 , wherein the V-shaped trough comprises an aperture positioned such that the image of the absorber reflected in a wall of the V-shaped trough has a top which is positioned proximal or above the aperture of the V-shaped top in the direction extending from the top of the trough to the bottom of the trough. 
     
     
         17 . The apparatus of  claim 15 , further comprising: an efficiency loss averaged over an acceptance angle relative to an equivalent gapless apparatus of 0.02 or less. 
     
     
         18 . The apparatus of  claim 15 , further comprising: concentration ratio equal to at least 90% of that of an equivalent gapless apparatus. 
     
     
         19 . The apparatus of  claim 15 , wherein the gap distance is less than a radius of the absorber.