Apparatuses and methods for providing a solar thermal energy absorber tube for a solar collector system

Abstract

Various embodiments provide an absorber tube that comprises an inner tube having an exterior surface, at least a portion of which contains a plurality of coating layers. The absorber tube also includes an outer tube spaced apart from the inner tube so as to define a cavity between the two. At least one of the coating layers may be configured to substantially impede migration of gaseous particles from the interior surface and into said cavity. At least one of the coating layers may be a reflective copper coating that is adhered to the exterior surface via an electrical charging process. An absorber tube comprising a connecting member between central and end portions of the tube is also provided. The central portion may be formed from carbon steel, while remaining portions are formed from stainless steel. Coating layers may be likewise adhered to only the central portion.

That which is claimed: 
     
         1 . An absorber tube configured for the collection of solar thermal energy in a solar concentrator system, said absorber tube comprising:
 an inner tube comprising an interior surface and an exterior surface, at least a portion of said exterior surface comprising a plurality of coating layers; and   an outer tube substantially surrounding said inner tube and being spaced apart from and concentric with said inner tube so as to define a cavity between said inner tube and said outer tube,   wherein at least one of said plurality of coating layers is configured to substantially impede migration of gaseous molecular particles from said interior surface of said inner tube and into said cavity.   
     
     
         2 . The absorber tube of  claim 1 , wherein said plurality of coating layers comprise a reflective layer and an absorptive layer, said reflective layer being substantially intermediate said absorptive layer and said exterior surface of said inner tube. 
     
     
         3 . The absorber tube of  claim 2 , wherein said reflective layer is configured to deflect a substantial portion of said gaseous molecular particles toward said interior surface of said inner tube. 
     
     
         4 . The absorber tube of  claim 2 , wherein said reflective layer comprises a copper coating, said copper coating being configured to deflect a substantial portion of said gaseous molecular particles toward said interior surface of said inner tube. 
     
     
         5 . The absorber tube of  claim 2 , wherein said reflective layer is operatively adhered to said exterior surface of said inner tube. 
     
     
         6 . The absorber tube of  claim 5 , wherein said reflective layer comprises a copper coating that is operatively adhered to said exterior surface of said inner tube by generating an electrical charge between said copper coating and said exterior surface. 
     
     
         7 . The absorber tube of  claim 2 , wherein said absorptive layer comprises a nitride material configured to absorb a substantial portion of the solar thermal energy captured in said solar concentrator system. 
     
     
         8 . The absorber tube of  claim 1 , wherein said plurality of coating layers comprise a reflective layer, a bonding layer, and an absorptive layer, said reflective layer being substantially intermediate said bonding layer and said exterior surface of said inner tube, said bonding layer being substantially intermediate said reflective layer and said absorptive layer. 
     
     
         9 . The absorber tube of  claim 1 , wherein said plurality of coating layers comprise a copper coating, said copper coating being operatively adhered to said exterior surface of said inner tube by generating an electrical charge between said copper coating and said exterior surface, said copper coating further being configured to deflect a substantial portion of said gaseous molecular particles toward an interior volume of said inner tube so as to substantially impede migration of gaseous molecular particles from said interior volume and into said cavity between said inner tube and said outer tube. 
     
     
         10 . The absorber tube of  claim 1 , wherein:
 said inner tube comprises a first end portion, a first connecting member, a second end portion, a second connecting member, and a central portion, said central portion being located intermediate said first and said second connecting portions, said first connecting member being further located intermediate said first end portion and said central portion, said second connecting member being further located intermediate said second end portion and said central portion; and   said at least a portion of said exterior surface of said inner tube comprising said plurality of coating layers consists of said central portion.   
     
     
         11 . The absorber tube of  claim 10 , wherein:
 said central portion is formed from a carbon steel material;   said first and second connecting members are formed from a stainless steel material; and   said first and second end portions are formed from a stainless steel material.   
     
     
         12 . The absorber tube of  claim 10 , wherein:
 said connecting member is substantially disc-shaped and comprises an annular ring portion and a protrusion portion;   a diameter of said annular ring portion is substantially the same as a diameter of said interior surface of said inner tube, such that at least a portion of said annular ring portion is configured to form a seal between said interior surface of said inner tube and said connecting member; and   a diameter of said protrusion portion is substantially the same as a diameter of said exterior surface of said inner tube, such that at least a portion of said protrusion portion is configured to form a seal between a passage through said inner tube and said connecting member.   
     
     
         13 . The absorber tube of  claim 10 , wherein said plurality of coating layers comprise at least a copper coating, said copper coating being operatively adhered to said central portion of said inner tube by generating an electrical charge between said copper coating and said central portion, said copper coating further being configured to deflect a substantial portion of said gaseous molecular particles toward an interior volume of said inner tube so as to substantially impede migration of gaseous molecular particles from said interior volume and into said cavity between said inner tube and said outer tube. 
     
     
         14 . An absorber tube configured for the collection of solar thermal energy in a solar concentrator system, said absorber tube comprising:
 an inner tube comprising:
 (A) a central portion; 
 (B) at least one end portion, said at least one end portion being configured to facilitate mounting the absorber tube relative to said solar concentrator system; and 
 (C) at least one connecting member, said at least one connecting member being located intermediate said central portion and said at least one end portion; and 
   said central portion of said inner tube being formed from a steel-based material having a structural composition substantially different from a material of said at least one end portion.   
     
     
         15 . The absorber tube of  claim 14 , wherein said steel-based material of said central portion comprises carbon steel and said material of said at least one end portion comprises stainless steel. 
     
     
         16 . The absorber tube of  claim 15 , wherein said at least one connecting member is formed from a stainless steel material. 
     
     
         17 . The absorber tube of  claim 14 , wherein said steel-based material of said central portion is at least one of substantially lighter than, substantially harder than, and substantially stronger than said material of said at least one end portion. 
     
     
         18 . The absorber tube of  claim 14 , wherein, during use, the steel-based material of said central portion expands along a longitudinal axis of said inner tube at an expansion rate approximately ⅙ of an expansion rate for said material of said at least one end portion. 
     
     
         19 . The absorber tube of  claim 14 , wherein said connecting member is substantially disc-shaped. 
     
     
         20 . The absorber tube of  claim 14 , wherein said connecting member comprises an annular ring portion and a protrusion portion. 
     
     
         21 . The absorber tube of  claim 20 , wherein:
 a diameter of said annular ring portion is substantially the same as a diameter of an interior surface of said inner tube, such that at least a portion of said annular ring portion is configured to form a seal between said interior surface of said inner tube and said connecting member; and   a diameter of said protrusion portion is substantially the same as a diameter of an exterior surface of said inner tube, such that at least a portion of said protrusion portion is configured to form a seal between a passage through said inner tube and said connecting member.   
     
     
         22 . The absorber tube of  claim 21 , wherein:
 said annular ring portion comprises a first seat portion, said first seat portion being configured to form a seal between an interior surface of said at least one end portion and said connecting member;   said annular ring portion comprises a second seat portion, said second seat portion being configured to form a seal between an interior surface of said central portion and said connecting member; and   said protrusion portion is substantially intermediate said first seat portion and said second seat portion.   
     
     
         23 . The absorber tube of  claim 22 , wherein said first seat portion, said second seat portion, and at least a portion of said protrusion portion are configured to substantially mate with said central portion and said at least one end portion so as to form a press fit there-between. 
     
     
         24 . The absorber tube of  claim 14 , wherein:
 said at least one end portion comprises a first end portion and a second end portion;   said at least one connecting member comprises a first connecting member and a second connecting member, said first connecting member being located intermediate said central portion and said first end portion, said second connecting member being located intermediate said central portion and said second end portion;   said first connecting member comprises a first annular ring portion and a first protrusion portion, a diameter of said first annular ring portion being substantially the same as a diameter of an interior surface of said inner tube, such that at least a portion of said first annular ring portion is configured to form a seal between said interior surface of said inner tube and said first connecting member, a diameter of said first protrusion portion being substantially the same as a diameter of an exterior surface of said inner tube, such that at least a portion of said first protrusion portion is configured to form a seal between a passage through said inner tube and said first connecting member; and   said second connecting member comprises a second annular ring portion and a second protrusion portion, a diameter of said second annular ring portion being substantially the same as a diameter of an interior surface of said inner tube, such that at least a portion of said second annular ring portion is configured to form a seal between said interior surface of said inner tube and said second connecting member, a diameter of said second protrusion portion being substantially the same as a diameter of an exterior surface of said inner tube, such that at least a portion of said second protrusion portion is configured to form a seal between a passage through said inner tube and said second connecting member.   
     
     
         25 . The absorber tube of  claim 24 , wherein:
 said central portion is formed from a carbon steel material;   said first and second connecting members are formed from a stainless steel material; and   said first and second end portions are formed from a stainless steel material.   
     
     
         26 . The absorber tube of  claim 14 , wherein:
 said absorber tube further comprises an outer tube substantially surrounding said inner tube and being spaced apart from and concentric with said inner tube so as to define a cavity between said inner tube and said outer tube;   said central portion of said inner tube comprises an interior surface and an exterior surface, at least a portion of said exterior surface of said central portion comprising a plurality of coating layers; and   at least one of said plurality of coating layers is configured to substantially impede migration of gaseous molecular particles from said interior surface of said central portion of said inner tube and into said cavity.   
     
     
         27 . The absorber tube of  claim 26 , wherein said plurality of coating layers comprise a copper coating, said copper coating being operatively adhered to said exterior surface of said central portion of said inner tube by generating an electrical charge between said copper coating and said exterior surface, said copper coating further being configured to deflect a substantial portion of said gaseous molecular particles toward an interior volume of said central portion of said inner tube so as to substantially impede migration of gaseous molecular particles from said interior volume and into said cavity between said central portion of said inner tube and said outer tube. 
     
     
         28 . The absorber tube of  claim 26 , wherein:
 said plurality of coating layers comprise a reflective layer, a bonding layer, and an absorptive layer, said reflective layer being substantially intermediate said bonding layer and said exterior surface of said inner tube, said bonding layer being substantially intermediate said reflective layer and said absorptive layer;   said reflective layer is configured to deflect a substantial portion of said gaseous molecular particles toward said interior surface of said central portion of said inner tube; and   said absorptive layer is configured to absorb a substantial portion of the solar thermal energy captured in said solar concentrator system .   
     
     
         29 . A method for manufacturing an absorber tube configured for the collection of solar thermal energy in a solar concentrator system, said method comprising the steps of:
 (A) providing an absorber tube comprising:
 (1) an inner tube comprising an interior surface and an exterior surface; and 
 (2) an outer tube substantially surrounding said inner tube and being spaced apart from and concentric with said inner tube so as to define a cavity between said inner tube and said outer tube; 
   (B) inserting a reflective coating material into said cavity between said inner tube and said outer tube; and   (C) creating an electrically charged vacuum within said cavity, such that said reflective coating material is electrically attracted to and thus adhered to said exterior surface of said inner tube.   
     
     
         30 . The method of  claim 29 , wherein:
 said reflective layer comprises a copper coating;   said copper coating is negatively charged; and   said vacuum is positively charged so as to cause the copper coating to be forced into contact with said exterior surface of said inner tube.