Multi-tube solar collector structure

Abstract

A collector system ( 12 ) is disclosed that comprises a row of linearly conjoined collector structures ( 13 ). The collector system is arranged to be located at a level above a field of reflectors ( 10 ) and to receive solar radiation reflected from the reflectors within the field. The collector structure ( 13 ) comprises an inverted trough ( 16 ) and, located within the trough, a plurality of longitudinally extending absorber tubes ( 30 ) that, in use, are arranged to carry a heat exchange fluid. The absorber tubes ( 30 ) are supported side-by-side within the trough and each absorber tube has a diameter that is small relative to the aperture of the trough. The ratio of the diameter of each absorber tube to the trough aperture dimension is of the order of 0.01:1.00 to 0.10:1:00 and, thus, a plurality of absorber tube functions, in the limit, effectively to simulate a flat plate absorber.

1 . A linear Fresnel collector comprising a stationary collector structure that is arranged to be located at a level above a field of reflectors and to receive solar radiation reflected from reflectors within the field, the collector structure comprising an inverted trough having an aperture and an enclosing window and, located within the trough, a plurality of longitudinally extending absorber tubes that are arranged to carry a heat exchange fluid, each absorber tube having a diameter that is small relative to the aperture of the trough through which the tubes are illuminated, and the absorber tubes being supported side-by-side in coplanar fashion within the trough with some of said absorber tubes being located along margins of the inverted trough, wherein the collector structure is configured such that a portion of heat exchange fluid within the collector structure and having a lower temperature than other of the heat exchange fluid within the collector structure is directed through said tubes located along the margins of the inverted trough. 
     
     
         2 . The collector as claimed in  claim 1  wherein the diameter of each absorber tube to the dimension of the trough aperture has a ratio in the range of 0.01:1.00 to 0.10:1.00. 
     
     
         3 . The collector as claimed in  claim 1  wherein the diameter of each absorber tube to the dimension of the trough aperture has a ratio of about 0.03:1.00. 
     
     
         4 . The collector as claimed in  claim 1  wherein there are about ten to thirty of the absorber tubes supported side-by-side within the trough. 
     
     
         5 . The collector as claimed in  claim 1  wherein there are sixteen of the absorber tubes supported side-by-side within the trough. 
     
     
         6 . The collector as claimed in  claim 1  wherein each of the absorber tubes is constituted by a metal tube. 
     
     
         7 . The collector as claimed in  claim 1  wherein each of the absorber tubes is coated over at least a portion of its surface with a solar absorptive material coating. 
     
     
         8 . The collector as claimed in  claim 1  and incorporating a longitudinally extending roof, and wherein the inverted trough is located in spaced relationship below the roof 
     
     
         9 . The collector as claimed in  claim 8  wherein an insulating material is located in the space between the inverted trough and the roof 
     
     
         10 . The collector as claimed in  claim 1  wherein a window that is substantially transparent to solar radiation extends across the aperture of the inverted trough and thereby closes the trough to create a heat confining cavity within the trough. 
     
     
         11 . The collector as claimed in  claim 10  wherein the window is formed from a flexible plastics sheet material that is connected to marginal side wall portions of the trough. 
     
     
         12 . The collector as claimed in  claim 11  wherein means are provided to pressurise the cavity and thereby inflate the window in a direction away from the absorber tubes. 
     
     
         13 . The collector as claimed in  claim 10  wherein the inverted trough has flared sidewalls. 
     
     
         14 . The collector as claimed in  claim 1  and including flow control for the heat exchange fluid in the plurality of absorber tubes. 
     
     
         15 . The collector as claimed in  claim 1  and including flow control to selectively vary the channeling of the heat exchange fluid into and through the plurality of absorber tubes whereby the absorption aperture of the collector structure is, in use, effectively varied. 
     
     
         16 . The collector as claimed in  claim 1  and comprising a plurality of the collector structures, the collector structures being connected together co-linearly to form a row of the structures. 
     
     
         17 . The collector as claimed in  claim 16  wherein the row has a length and each of the absorber tubes extends along substantially the full length of the row. 
     
     
         18 . The collector as claimed in  claim 1 , wherein the trough is surmounted by a corrugated roof. 
     
     
         19 . The collector as claimed in  claim 1 , wherein the trough is surmounted by a roof that is carried by arched structural members. 
     
     
         20 . The collector as claimed in  claim 2  wherein the aperture is about 1100 mm. 
     
     
         21 . The collector as claimed in  claim 3  wherein the aperture is about 1100 mm. 
     
     
         22 . The collector as claimed in  claim 4  wherein the aperture is about 1100 mm. 
     
     
         23 . The collector as claimed in  claim 5  wherein the aperture is about 1100 mm. 
     
     
         24 . The collector as claimed in  claim 2  wherein a plurality of said tubes each has an outside diameter of about 33 mm. 
     
     
         25 . The collector as claimed in  claim 3  wherein a plurality of said tubes each has an outside diameter of about 33 mm. 
     
     
         26 . The collector as claimed in  claim 4  wherein a plurality of said tubes each has an outside diameter of about 33 mm. 
     
     
         27 . The collector as claimed in  claim 5  wherein a plurality of said tubes each has an outside diameter of about 33 mm. 
     
     
         28 . The collector as claimed in  claim 20  wherein a plurality of said tubes each has an outside diameter of about 33 mm.