Reflector element for a solar heat reflector and the method for producing the same

Abstract

Reflector element ( 1 ) for a solar collector which comprises a not mechanically flexed monolithic glass pane ( 2 ) of heat treated glass which due to its enhanced resistance properties becomes self-supported without requiring the presence of any kind of frame member or device to maintain its shape at the normal utilization temperatures. The reflector element is substantially parabolic and can be provided with at least one bore ( 3 ) for a fixing element to fix the reflector element ( 1 ) to a supporting structure.

1 . A reflector element ( 1 ) for a solar heat reflector comprising a self-supported curved not mechanically flexed monolithic heat-treated glass pane ( 2 ) and reflecting means. 
     
     
         2 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that the heat treatment process consists of thermal heat strengthening. 
     
     
         3 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that the heat treatment process consists of thermal tempering. 
     
     
         4 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that it is substantially parabolic. 
     
     
         5 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that it is provided with at least one bore ( 3 ) for a fixing element to fix the reflector element ( 1 ) to a supporting structure. 
     
     
         6 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that the thickness of glass pane ( 2 ) is equal or less than 5 mm. 
     
     
         7 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that its energy reflectance (R E  %) is larger than 92% in the solar spectrum comprising 270 to 2500 nm, with an air mass value of 1.5. 
     
     
         8 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that its light reflectance (RL D65 %) is larger than 94% in the solar spectrum comprising 270 to 2500 nm, with an air mass value of 1.5. 
     
     
         9 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that when the glass pane ( 2 ) is thermally heat strengthened, both reflector element surface sides have a compressive layer with strength in a range between about 20 Mpa and about 69 Mpa. 
     
     
         10 . A reflector element ( 1 ) for a solar heat reflector according to  claim 1 , characterized in that when the glass pane is thermally heat tempered, both reflector element surface sides have a compressive layer with strength in excess of 70 Mpa. 
     
     
         11 . A solar heat reflector comprising at least one reflector element ( 1 ) according to  claim 1 . 
     
     
         12 . A solar heat reflecting installation comprising at least one solar heat reflector according to  claim 11 . 
     
     
         13 . Method for producing the reflector element ( 1 ) of  claim 1  comprising the steps of
 i) cutting off an annealed glass, grinding of the edges of the cut glass pane,   ii) washing the glass pane,   iii) loading the glass pane in a bending furnace for its bending until the desired curved shape,   iv) heat treatment of the glass pane by heating and rapid cooling in order to increase its strength,   v) cooling down the glass pane to normal handling temperature, and   vi) application of a reflective coating ( 10 ) and protective layers ( 11 - 14 ).   
     
     
         14 . Method according to  claim 13  characterized in that the heat treatment is thermal heat strengthening. 
     
     
         15 . Method according to  claim 13  characterized in that the heat treatment is thermal tempering. 
     
     
         16 . Method according to  claim 13  characterized in that the bending furnace bends the glass pane until a substantially parabolic shape. 
     
     
         17 . Method according to  claim 13  characterized in that the step i) of edge grinding additionally comprises the operation of drilling bores ( 3 ) in the glass pane. 
     
     
         18 . Method according to  claim 13  characterized in that the step vi) of application of a reflective coating ( 10 ) and protective layers ( 11 - 14 ) comprises the following steps:
 a) preparation of the glass pane by removing all impurities and minor surface defects on the glass side to be coated, polishing and further warming up to a temperature of about 25° C.,   b) deposition of a layer of metallic silver ( 10 )   c) allowing a reaction time and application of an anticorrosion and antioxidant layer made of metallic copper ( 11 ),   d) allowing a reaction time, rinsing with water, air drying and entering a heating tunnel for the final metal coats ( 10 ,  11 ) drying,   e) application of a “basecoat” paint layer ( 12 ), curing in a infrared curing furnace and an cooling to reduce the glass pane temperature prior to the next step,   f) application of a second layer of paint or “intermediate” paint ( 13 ), curing in a infrared curing furnace and an cooling to reduce the glass pane temperature prior to the next step, and   g) application of a third layer of paint or “top” coat ( 14 ), curing in a infrared curing furnace and an cooling to reduce the glass pane temperature.   
     
     
         19 . Method according to  claim 18  characterized in that the step b) of deposition of a layer of metallic silver ( 10 ) is made after two solutions, a first solution of silver nitrate and a second solution of a reducer, being both solutions independently sprayed and mixed up on top of the glass pane surface ( 2 ). 
     
     
         20 . Method according to  claim 18  characterized in that the layer of metallic silver ( 10 ) has a minimum thickness of 0.7 g/m 2 . 
     
     
         21 . Method according to  claim 18  characterized in that the step c) of deposition of a layer of metallic copper ( 11 ) is made after two solutions, a first solution of copper sulphate and a second solution of a suspension of iron powder, being both solutions independently sprayed and mixed up on top of the layer ( 10 ). 
     
     
         22 . Method according to  claim 18  characterized in that the layer of copper (step c)) has a minimum thickness of 0.3 g/m 2 . 
     
     
         23 . Method according to  claim 18  characterized in that the dry film thickness for the base coat ( 12 ) is in a range between about 20 to 45 micron, the dry film thickness for the intermediate paint ( 13 ) is in a range between about 25 to 55 micron, and the dry film thickness for the top coat ( 14 ) is in a range between about 25 to 55 micron. 
     
     
         24 . Method according to  claim 18  characterized in that the reflecting coating and the protection layers are applied to the convex side off the glass pane ( 2 ).