Window System for a Solar Receiver and Method and Solar Receiver System Employing Same

Abstract

An improved window system for a solar receiver provides a high level of impedance to thermal re-radiation while minimizing Fresnel losses. The window system is characterized by a bundled array of optically transmissive members. In further aspects, a solar receiver employing the window system and a method for manufacture are provided.

1 . A window system for a solar receiver of a type having a solar energy receiving chamber, a solar energy receiving aperture defining an opening to the solar energy receiving chamber, and a solar energy absorber received within the solar energy receiving chamber, said window system comprising:
 a plurality of optically transmissive members formed of an optically transmissive material; and   said plurality of optically transmissive members attached together to form a bundled array.   
     
     
         2 . The window system of  claim 1 , wherein the optically transmissive members are selected from the group consisting of elongate tubes and elongate rods. 
     
     
         3 . The window system of  claim 1 , further comprising:
 a band clamp tightly fitting around the plurality of optically transmissive members to secure the plurality of optically transmissive members into said bundled array.   
     
     
         4 . The window system of  claim 1 , wherein each of the optically transmissive members is a tube having a peripheral wall, an axial bore, and an axis extending through said axial bore, and further comprising:
 said bundled array having a first, light receiving side and a second side opposite the first, light receiving side; and   the first light receiving side forming a generally planar light-receiving face which extends generally perpendicular to the axes of said tubes.   
     
     
         5 . The window system of  claim 4 , wherein each of the tubes has a peripheral wall with a transverse thickness that is much smaller than a diameter of the tubes. 
     
     
         6 . The window system of  claim 4 , wherein said generally planar light-receiving face has a diameter larger than a diameter of the solar energy receiving aperture. 
     
     
         7 . The window system of  claim 1 , wherein said plurality of optically transmissive members are arranged within said bundled array in a close-packed hexagonal configuration. 
     
     
         8 . The window system of  claim 1 , wherein each of said optically transmissive members has a cross-sectional shape selected from circular and polygonal. 
     
     
         9 . The window system of  claim 1 , wherein each of said optically transmissive members is a tube having a first end and a second end opposite the first end, and further wherein one or both of the first end and the second end of one or more of the tubes is rounded, thinned, sharpened, or chamfered. 
     
     
         10 . The window system of  claim 1 , wherein each of said optically transmissive members are of tubular construction and have a first end and a second end opposite the first end, and further wherein the first end is open and the second end is closed. 
     
     
         11 . The window system of  claim 10 , wherein the second end of each optically transmissive member is a closed, hemispherical end. 
     
     
         12 . The window system of  claim 1 , wherein each optically transmissive member has a first end and a second end opposite the first end, and further wherein one or both of the first end and the second end of one or more optically transmissive members of said plurality of optically transmissive members have an enlarged diameter portion, the enlarged diameter portion engaging one or more adjacent optically transmissive members in said bundled array. 
     
     
         13 . The window system of  claim 1 , wherein each of the plurality of optically transmissive members has a length to diameter ratio which is greater than or equal to 3. 
     
     
         14 . The window system of  claim 1 , wherein each of the optically transmissive members is of tubular construction having a diameter in the range of 1- 2 inches.    
     
     
         15 . The window system of  claim 1 , wherein the optically transmissive material is selected from the group consisting of quartz, glass, borosilicate glass, sapphire, and a metal oxide. 
     
     
         16 . A solar receiver, comprising:
 a cavity,   an aperture for receiving light entering the cavity;   a solar absorber disposed within the cavity;   a plurality of optically transmissive members formed of an optically transmissive material attached together to form a bundled array; and   said bundled array disposed on said solar receiver at said aperture.   
     
     
         17 . The solar receiver of  claim 16 , wherein each of the optically transmissive members is of tubular construction, and further comprising:
 said bundled array having a first, outward facing surface and a second, inward facing surface, wherein the first surface is generally planar and aligned with a plane defined by said aperture.   
     
     
         18 . The solar receiver of  claim 17 , further comprising:
 said cavity including a proximal portion configured to avoid direct irradiation by solar energy entering the cavity and a distal portion having an absorber configured to absorb solar radiation entering the cavity, wherein the boundary between the proximal portion and the distal portion defines an absorber plane; and   said bundled array positioned at said aperture so that the first, light receiving surface is aligned with the plane defined by the aperture and the second surface extends to a distance within the cavity intermediate the plane defined by the aperture and the absorber plane.   
     
     
         19 . The solar receiver of  claim 17 , further comprising:
 said cavity including a proximal portion configured to avoid direct irradiation by solar energy entering the cavity and a distal portion having an absorber configured to absorb solar radiation entering the cavity, wherein the boundary between the proximal portion and the distal portion defines an absorber plane; and   said bundled array positioned at said aperture so that the first, light receiving surface is aligned with the plane defined by the aperture and the second surface extends to a distance within the cavity which is aligned with or beyond the absorber plane.   
     
     
         20 . A method for manufacturing a solar receiver, comprising:
 forming a solar receiver of a type having a cavity, an aperture for receiving light entering the cavity, and a solar absorber disposed within the cavity;   girding a plurality of optically transmissive members to form a bundled array, each optically transmissive member of said plurality of optically transmissive members formed of an optically transmissive material; and   attaching said bundled array to said solar receiver at the aperture.