Lightweight, low cost solar energy collector

Abstract

A lightweight solar concentrator of the reflecting parabolic or trough type is realized via a thin reflecting film, an inflatable structural housing and tensioned fibers. The reflector element itself is a thin, flexible, specularly-reflecting sheet or film. The film is maintained in the parabolic trough shape by means of a plurality of tensioned fibers arranged to be parallel to the longitudinal axis of the parabola. Fiber ends are terminated in two spaced anchorplates, each containing a plurality of holes, which lie on a desired parabolic contour. In a preferred embodiment, these fibers are arrayed in pairs with one fiber contacting the front side of the reflecting film and the other contacting the back side of the reflecting film. The reflective surface is thereby slidably captured between arrays of fibers, which control the shape, and position of the reflective film. Gas pressure in the inflatable housing generates fiber tension to achieve a truer parabolic shape. A plurality of bridges and or retention clips may be employed in certain embodiments to maintain the position of the reflective surface relative to the fibers.

1 . A solar concentrator comprising:
 a membrane reflector having a unitary line focus;   a transparent tubular housing enclosing said reflector; and   a plurality of strings extending within said tubular housing, wherein said plurality of strings shape said reflector to have a substantially stepless parabolic cross-section.   
     
     
         2 . (canceled) 
     
     
         3 . The concentrator recited in  claim 1  wherein said strings are in a state of tension. 
     
     
         4 . The concentrator recited in  claim 1  wherein said strings are arranged in pairs, each such pair having a string on front and back surfaces of said reflector. 
     
     
         5 . The concentrator recited in  claim 4  wherein said string pairs are in a state of tension. 
     
     
         6 . The concentrator recited in  claim 1  wherein said housing is internally pressurized above external atmospheric pressure by a gas within said housing. 
     
     
         7 .- 8 . (canceled) 
     
     
         9 . The concentrator recited in  claim 1  wherein said housing comprises opposed end plates, a gas in said housing being pressurized to cause said endplates to be extended further from one another; and wherein said reflector is shaped by a plurality of string pairs, each said pair supporting said reflector on front and back surfaces of said reflector, said string pairs being connected to said endplates and being subjected to tension depending on the separation between said endplates. 
     
     
         10 . (canceled) 
     
     
         11 . The concentrator recited in  claim 1  further comprising a solar energy receiver extending along at least a portion of said line focus. 
     
     
         12 . The concentrator recited in  claim 1  further comprising means for rotating said housing to control the orientation of said reflector relative to incident sunlight. 
     
     
         13 .- 15 . (canceled) 
     
     
         16 . The concentrator recited in  claim 1  wherein said membrane reflector is slidably received by said strings without any significant tension being applied to said membrane reflector. 
     
     
         17 . The concentrator recited in  claim 9  wherein said endplates each comprise an axially flexible material. 
     
     
         18 . The concentrator recited in  claim 1  further comprising at least one bridge operatively positioned at an interval along the length of the strings to provide means to maintain the string positions in a desired parabolic shape. 
     
     
         19 . The concentrator recited in  claim 1  wherein said membrane reflector comprises a plurality of adjacent membrane reflector sections. 
     
     
         20 . The concentrator recited in  claim 19  further comprising at least one retention clip operatively connected to said adjacent membrane reflector sections to operatively position said reflector sections relative to the strings. 
     
     
         21 .- 22 . (canceled) 
     
     
         23 . A parabolic trough solar energy concentrator comprising a stepless parabolic reflector shaped by a plurality of tensioned string pairs extending along said reflector, each said tensioned string pair having respective strings positioned on opposed surfaces of said reflector. 
     
     
         24 . The concentrator recited in  claim 23  further comprising a gas-tight tubular transparent housing enclosing said reflector. 
     
     
         25 . The concentrator recited in  claim 23  wherein said reflector comprises a film having a reflective surface and wherein said film is received between said pairs of strings without any significant tension being applied to said film. 
     
     
         26 . The concentrator recited in  claim 24  wherein said housing is hermetically sealed by a pair of opposed endplates, each such endplate comprising an axially flexible material. 
     
     
         27 . (canceled) 
     
     
         28 . The concentrator recited in  claim 24  wherein a gas inside said housing is under pressure and wherein said pressure at least partially contributes to said tension of said strings. 
     
     
         29 . (canceled) 
     
     
         30 . The concentrator recited in  claim 24  further comprising means for rotating said concentrator to control the orientation of said reflector and receiver relative to incident sunlight. 
     
     
         31 . (canceled) 
     
     
         32 . The concentrator recited in  claim 23  wherein said reflector comprises a plurality of reflector sections. 
     
     
         33 . The concentrator recited in  claim 32  further comprising at least one retention clip operatively connected to two or more reflector sections to operatively position said reflector sections relative to the strings. 
     
     
         34 . The concentrator recited in  claim 32  further comprising at least one bridge operatively positioned at an interval along the length of the strings and between a pair of adjacent reflector sections to provide means to maintain the string positions in a desired parabolic shape. 
     
     
         35 . (canceled)