Method for producing an absorber for a solar collector, and a solar collector

Abstract

A method for producing a solar heat absorber for a solar collector, the solar heat absorber having a fluid inlet and a fluid outlet. The method includes the steps of providing a first and a second substantially flat metal plate, laser welding the plates together at least along a perimeter of the plates, providing at least a circumferential weld while pressing the plates together, placing the welded plates in a press that provides its pressure at the weld or welds and the press applying a pressure of at least 200 tons per m 2 of absorber, and then providing a fluid under a pressure to the absorber via at least one of the fluid inlet and the fluid outlet.

What is claimed is: 
     
         1 . A method for producing an absorber for a solar collector, the absorber having a fluid inlet and a fluid outlet, the method comprising:
 providing a first substantially flat metal plate and a second substantially flat metal plate;   laser welding the first substantially flat metal plate and the second substantially flat metal plate together at least along a perimeter of the first substantially flat metal plate and the second substantially flat metal plate via at least a circumferential weld, while pressing together the first substantially flat metal plate and the second substantially flat metal plate;   placing the welded first substantially flat metal plate and the welded second substantially flat metal plate in a press and applying pressure at the welds using a pressure of at least 200 tons per m 2  of the absorber;   providing a fluid under a pressure to the absorber via at least one of the fluid inlet and the fluid outlet, the fluid being applied at a pressure difference of at least 20 bar between the fluid inlet and the fluid outlet to thereby inflate the absorber, expanding the welded first substantially flat metal plate and the welded second substantially flat metal plate to thereby create a permanent fluid channel between the first substantially flat metal plate and the second substantially flat metal plate and also fluidically-couple the fluid inlet to the fluid outlet.   
     
     
         2 . The method of  claim 1 , further comprising providing at least one through hole in one of the first substantially flat metal plate and the second substantially flat metal plate to thereby provide the fluid inlet, and at least one through hole in one of the first substantially flat metal plate and the second substantially flat metal plate to thereby provide the fluid outlet. 
     
     
         3 . The method of  claim 1 , further comprising pressing the first substantially flat metal plate and the second substantially flat metal plate on top of one another along at least a perimeter of the first substantially flat metal plate and the second substantially flat metal plate. 
     
     
         4 . The method of  claim 1 , wherein the press comprises a die having a pattern which has the shape of the weld and which extends 1-20 mm from the basic surface of the die. 
     
     
         5 . The method of  claim 4 , wherein the press comprises a first die having the pattern the shape of the weld, and a second, opposite die that has the shape of the weld such that when pressing the welded metal plates, both patterns press the weld between them. 
     
     
         6 . The method of  claim 1 , wherein the press comprises a die having a pattern which has the shape of the weld and which extends 1-5 mm from the basic surface of the die. 
     
     
         7 . The method of  claim 6 , wherein the press comprises a first die having the pattern the shape of the weld, and a second, opposite die that also has the shape of the weld such that when pressing the welded metal plates, both patterns press the weld between them. 
     
     
         8 . The method of  claim 1 , wherein the welding of the first substantially flat metal plate and the second substantially flat metal plate includes proving spot welds in the fluid channel for welding together the metal plates in the fluid channel to thereby provide flow turbulence means between the inlet and the outlet. 
     
     
         9 . The method of  claim 1 , wherein the weld comprises a circumferential weld enclosing at least the inlet and the outlet. 
     
     
         10 . The method of  claim 9 , further comprising providing one or more welds that provide boundaries of one or more zigzag fluid channels fluid coupling the inlet and the outlet. 
     
     
         11 . The method of  claim 9 , further comprising providing in an alternating manner first and second welds such that the first welds run from the circumferential weld at one first end of the absorber end and that end before the circumferential weld at an opposite second end of the absorber, and the second welds run from the circumferential weld at the opposite, second end and that end before the circumferential weld at the first end of the solar heat absorber. 
     
     
         12 . The method of  claim 1 , wherein spot welds are welded within a circumference of the circumferential weld. 
     
     
         13 . The method of  claim 1 , wherein the circumferential weld is provided to enclose at least the fluid inlet and the fluid outlet, and one or more welds are provided that provide boundaries of one or more fluid channels between the fluid inlet and the fluid outlet, the welds providing a fluid channel spiralling from a side of the absorber to a centre of the absorber. 
     
     
         14 . The method of  claim 1 , wherein before the first substantially flat metal plate and the second substantially flat metal plate are placed on top of one another, weld-preventing layers are provided between the first substantially flat metal plate and the second substantially flat metal plate at the positions of the fluid inlet and the fluid outlet. 
     
     
         15 . The method of  claim 1 , wherein at the location of one of the inlet and the outlet, one of the first substantially flat metal plate and the second substantially flat metal plate is provided with a through hole. 
     
     
         16 . The method of  claim 1 , wherein before the first substantially flat metal plate and the second substantially flat metal plate are expanded, nipples provided with a flange are provided at the through holes and welded to one of the first substantially flat metal plate and the second substantially flat metal plate with the flange around the through holes before the fluid under pressure is provided to the absorber. 
     
     
         17 . The method of  claim 1 , wherein before the first substantially flat metal plate and the second substantially flat metal plate are expanded, nipples are provided at the through holes and attached to one of the first substantially flat metal plate and the second substantially flat metal plate and around the through holes before the fluid under pressure is provided to the absorber without attaching together the first substantially flat metal plate and the second substantially flat metal plate at the locations of the through holes. 
     
     
         18 . The method of  claim 1 , further comprising coating the solar collectors after welding, and transporting the coated solar collectors after coating using a transport system having a buffer sized to retain the coated solar collectors at a time sufficient to permit the coating to dry. 
     
     
         19 . A solar collector comprising:
 a solar heat absorber including a fluid inlet and a fluid outlet;   a first substantially flat metal plate and a second substantially flat metal plate being laser welded to the first substantially flat metal plate at least along a perimeter of the first substantially flat metal plate and the second substantially flat metal plate, and including at least a circumferential weld;   a fluid channel provided between the first substantially flat metal plate and the second substantially flat metal plate; and   wherein the fluid inlet is fluidically coupled to the fluid outlet.   
     
     
         20 . A solar collector comprising:
 a solar heat absorber including a first metal plate and a second metal plate welded together at respective perimeters thereof via a continuous, circumferential weld, a fluid inlet and a fluid outlet provided within the circumferential weld, at least one continuous weld extending between the fluid inlet and the fluid outlet, and a plurality of spot welds within the circumferential weld.