Solar thermal collector

Abstract

A solar thermal collector comprising multiplicity of chords and webs is disclosed. The first, second and third horizontal chord of the solar thermal collector are connected to one another by webs positioned vertically to said horizontal chords. The first horizontal chord is transparent and the second horizontal chord, which is positioned between the first and third horizontal chords, absorbs thermal radiation and is perforated. The horizontal chords and said webs of the inventive solar thermal collector comprise thermoplastic materials. Producing the solar thermal collector including perforating the second horizontal chord by means of a laser beam is also disclosed.

1 . A solar thermal collector comprising a first, second and third horizontal chords that are connected to one another by webs vertical to said horizontal chords in which the first horizontal chord is transparent and the second horizontal chord, which is positioned between the first and third horizontal chords, absorbs radiation and is perforated with a multiplicity of holes, said horizontal chords and said webs comprising thermoplastic materials.  
   
   
       2 . The solar thermal collector according to  claim 1 , characterised in that the proportion of the perforated surface in the whole surface of the second horizontal web is at most 3%  
   
   
       3 . The solar thermal collector of  claim 2  wherein the proportion is at most 1%.  
   
   
       4 . The solar thermal collector of  claim 2  wherein the proportion is 0.1 to 0.4%.  
   
   
       5 . The solar thermal collector according to  claim 1  wherein the horizontal chords have a thickness of 0.2 to 2 mm.  
   
   
       6 . Solar thermal collector according to  claim 1  or  2  wherein chords and webs are forming at least two superimposed rows of adjacent chambers, which are separated from each other and may be flowed through by a heat exchange gas in particular by air.  
   
   
       7 . Solar thermal collector according to  claim 6  wherein the superimposed chambers are connected by a multiplicity of holes.  
   
   
       8 . Solar thermal collector according to  claim 6  or  7  wherein the chambers are closed at their ends and the chambers located above the second (absorbing) horizontal chord have at least one inlet for a heat exchange gas and the chambers located below the second horizontal chord have at least one outlet for heated solar thermal collector gas.  
   
   
       9 . Solar thermal collector according to  claim 6  or  7  wherein the chambers are connected to a blower which optionally is part of a pumping circuit.  
   
   
       10 . Solar thermal collector according to  claim 6  or  7  wherein the cross section of the chambers preferably has a cross section area of 0,25 to 3600 mm 2 .  
   
   
       11 . The solar thermal collector according to  claim 1  wherein the vertical webs have a height of 3 to 50 mm.  
   
   
       12 . The solar thermal collector according to  claim 1  wherein the thermoplastics material is at least one member selected from the group consisting of polycarbonate, polymethyl methacrylate, polystyrene, polyethylene, polyethylene terephthalate, thermoplastic polyurethane and polyvinyl chloride.  
   
   
       13 . The solar thermal collector according to  claim 1  wherein the second horizontal chord and/or the third horizontal chord comprise at least one member selected from the group consisting of polybutylene terephthalate, polystyrene, thermoplastic polyurethane and acrylonitrile/butadiene/styrene/copolymer.  
   
   
       14 . The solar thermal collector according to  claim 1  wherein the second horizontal chord contains carbon black.  
   
   
       15 . A method for the production of the solar thermal collector of  claim 1  comprising in a first step forming a multiple web panel by coextrusion of a transparent and a radiation absorbing thermoplastic material with a plurality of horizontally oriented chords, which are connected by a plurality of vertical webs and wherein the second horizontal chord comprises the radiation absorbing thermoplastic material and in a second step directing a laser beam through the first horizontal chord onto the second horizontal web in a manner calculated to perforate said second horizontal chord and providing the chord with a multiplicity of holes.  
   
   
       16 . The method according to  claim 10  wherein the laser beam has a wavelength in the range of 800 to 1200 nm.