Rigid low cost solar thermal panels

Abstract

A rigid solar thermal panel created from thin flexible materials, including a solar absorber layer of a metal sheet coated with a solar absorbent material having dimples, a tensioned optical film above an upper surface of the solar absorber layer, and an insulation layer. The insulation layer is spaced apart from a lower surface of the solar absorber layer to form a cavity. The dimples project into the cavity and at least one of the dimples is in contact with the insulation layer, thereby providing rigid support for the rigid solar thermal panel.

What is claimed is: 
     
         1 . A rigid solar thermal panel comprising:
 a solar absorber layer comprising a metal sheet coated with a solar absorbent material;   a tensioned optical film above an upper surface of the solar absorber layer; and   an insulation layer below and spaced apart from a lower surface of the solar absorber layer to form a cavity, the metal sheet having dimples projecting into the cavity and at least one of the dimples being in contact with the insulation layer, the contact of the at least one dimple with the insulation layer providing rigid support for the rigid solar thermal panel.   
     
     
         2 . The rigid solar thermal panel of  claim 1 , wherein the dimple is substantially hemispherical. 
     
     
         3 . The rigid solar thermal panel of  claim 1 , wherein the optical film is a film comprising polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). 
     
     
         4 . The rigid solar thermal panel of  claim 1 , wherein the metal sheet is aluminum. 
     
     
         5 . The rigid solar thermal panel of  claim 1 , wherein the metal sheet is copper. 
     
     
         6 . The rigid solar thermal panel of  claim 1 , wherein the solar absorbent material is silicon dioxide. 
     
     
         7 . The rigid solar thermal panel of  claim 1 , further comprising a spring tensioning system that tensions the tensioned optical film over the upper surface of the solar absorber layer. 
     
     
         8 . The rigid solar thermal panel of  claim 7 , further comprising wear strips captured between a spring form along at least one edge of the optical film and a flange of the solar absorber layer, the wear strips configured to protect the optical film from frictional wear. 
     
     
         9 . The rigid solar thermal panel of  claim 1 , wherein the dimples comprise dimples that contact the insulation layer and additional dimples that project into the cavity a shorter distance than the contacting dimples. 
     
     
         10 . The rigid solar thermal panel of  claim 9  wherein the additional dimples are interspersed in the metal layer among the contacting dimples. 
     
     
         11 . The rigid solar thermal panel of  claim 1 , wherein the solar absorber layer has a dimpled area of about 80% to about 90% of a total surface area of the solar absorber layer. 
     
     
         12 . The rigid solar thermal panel of  claim 11 , wherein about 50% to about 70% of the dimpled area comprises contacting dimples and about 20% to about 40%% of the dimpled area comprises shorter dimples. 
     
     
         13 . The rigid solar thermal panel of  claim 9 , wherein the shorter dimples project a distance that is less than about 75% of the height of the cavity of the solar thermal panel. 
     
     
         14 . The rigid solar thermal panel of  claim 1 , wherein the solar absorber layer further comprises integrated side walls and a curved bend between an upper surface of the solar absorber layer and the integrated side walls, the curved bend configured to minimize wear to the optical film. 
     
     
         15 . The rigid solar thermal panel of  claim 14 , wherein the solar absorber layer further comprises integrated flanges at each side wall. 
     
     
         16 . The rigid solar thermal panel of  claim 15 , wherein each of the integrated side walls and flanges includes at least one L-shaped indentation configured to maintain a right angle between the side wall and the flange. 
     
     
         17 . The rigid solar thermal panel of  claim 1 , further comprising a support base beneath the insulation layer. 
     
     
         18 . The rigid solar thermal panel of  claim 17 , wherein the support base includes integral inlet and outlet air passages for the rigid solar thermal panel. 
     
     
         19 . The rigid solar thermal panel of  claim 17 , wherein the support base includes side walls and channels that increase structural rigidity of the solar thermal panel. 
     
     
         20 . The rigid solar thermal panel of  claim 17 , further comprising a support stand comprising a hinge mechanism adjustable to vary a vertical angle of the solar thermal panel relative to the support stand. 
     
     
         21 . The rigid solar thermal panel of  claim 20 , wherein the hinge mechanism comprises a substantially cylindrical component, a brace rotatable about the substantially cylindrical component, a series of radial holes in the brace, and a locking pin, the locking pin preventing rotational movement of the brace about the substantially cylindrical component when the locking pin is located in a radial hole. 
     
     
         22 . A method of manufacturing a rigid solar thermal panel, comprising:
 forming dimples in a metal absorber sheet and side walls along at least two edges of the metal absorber sheet to form a solar absorber layer;   placing an optical film on a surface of the solar absorber layer;   applying a force substantially perpendicular to the surface of the solar absorber layer to cause the metal absorber layer to bow;   securing the optical film on either side of the solar absorber layer proximate to the side walls; and   releasing the force to permit the solar absorber layer to return to its pre-bowed state and to tension the optical film across the surface of the metal absorber layer.   
     
     
         23 . The method of  claim 22 , further comprising placing a spring form at the bonded edges of the optical film. 
     
     
         24 . The method of  claim 22 , further comprising applying wear strips on at least two edges of the optical film, the wear strips preventing direct contact between the film the spring form.