Solar Thermal Energy Absorber Tube

Abstract

An absorber tube is provided that includes an inner tube and an outer tube that at least partially surrounds the inner tube and is concentric with the inner tube. An expansion element is present and is configured for expanding in response to differences in thermal expansion between the inner tube and the outer tube. A getter is located radially at a position between the inner tube and the outer tube.

1 . An absorber tube, comprising:
 an inner tube;   an outer tube surrounding at least a portion of the inner tube and concentric with the inner tube;   an expansion element configured for expanding in response to differences in thermal expansion between the inner tube and the outer tube; and   a getter located radially at a position between the inner tube and the outer tube.   
     
     
         2 . The absorber tube as set forth in  claim 1 , wherein the getter is located at a position between the inner tube and the outer tube such that the getter does not extend longitudinally beyond an end of the outer tube. 
     
     
         3 . The absorber tube as set forth in  claim 1 , wherein the getter is located at a position between the inner tube and the outer tube such that at least a portion of the getter extends longitudinally beyond an end of the outer tube. 
     
     
         4 . The absorber tube as set forth in  claim 1 , wherein the getter is a barium getter. 
     
     
         5 . The absorber tube as set forth in  claim 1 , further comprising a plate that is attached to the expansion element and that defines a getter trough, wherein the getter is carried by the getter trough. 
     
     
         6 . The absorber tube as set forth in  claim 1 , wherein the getter includes two pieces that are located at an angle of 180° from one another about the concentric axis of the inner tube and the outer tube. 
     
     
         7 . The absorber tube as set forth in  claim 1 , wherein at least a portion of the getter is located on the inner wall of the outer tube and is configured to change colors upon the introduction of air into the location between the inner tube and the outer tube. 
     
     
         8 . The absorber tube as set forth in  claim 1 , further comprising:
 a connecting member attached to the end of the outer tube and extending from the end of the outer tube such that the connecting member is located completely longitudinally beyond the outer tube, wherein the connecting member is attached to the expansion element; and   a cap attached to the inner tube, wherein the cap has a longitudinally extending portion that is attached to the expansion element;   wherein the expansion element has a series of radially extending portions connected by curved portions, wherein the curved portions extend in both the radial and longitudinal directions, and wherein the entire expansion element is located beyond the end of the outer tube in the longitudinal direction.   
     
     
         9 . An absorber tube, comprising:
 an inner tube;   an outer tube at least partially surrounding the inner tube and concentric with the inner tube;   a connecting member attached to an end of the outer tube; and   an expansion element attached to the connecting member, wherein the expansion element is configured for expanding in response to differences in thermal expansion between the inner tube and the outer tube, wherein the expansion element is located completely beyond the end of the outer tube in the longitudinal direction.   
     
     
         10 . The absorber tube as set forth in  claim 9 , wherein a vacuum is present between the inner tube and the outer tube, and wherein the outer tube is made at least partially of glass. 
     
     
         11 . The absorber tube as set forth in  claim 9 , wherein thermal expansion of the inner tube at a rate faster than thermal expansion of the outer tube causes the expansion element to expand in the longitudinal direction; and
 wherein thermal contraction of the inner tube at a rate faster than thermal contraction of the outer tube causes the expansion element to contract in the longitudinal direction.   
     
     
         12 . The absorber tube as set forth in  claim 9 , further comprising a cap attached to the inner tube, wherein the cap has a longitudinally extending portion that is attached to the expansion element, wherein the expansion element is located completely beyond the connecting member in the longitudinal direction with respect to the outer tube, and wherein the longitudinally extending portion of the cap is located completely beyond the expansion element in the longitudinal direction with respect to the outer tube. 
     
     
         13 . The absorber tube as set forth in  claim 9 , wherein the expansion element has a series of radially extending portions connected by curved portions, wherein the curved portions extend in both the radial and longitudinal directions. 
     
     
         14 . The absorber tube as set forth in  claim 9 , further comprising a getter located radially at a position between the inner tube and the outer tube, wherein the getter is located at a position between the inner tube and the outer tube such that the getter does not extend longitudinally beyond the end of the outer tube. 
     
     
         15 . The absorber tube as set forth in  claim 14 , wherein the getter is a barium getter and further comprising a plate that is attached to the expansion element and that defines a getter trough, wherein the getter is carried by the getter trough. 
     
     
         16 . An absorber tube, comprising:
 an inner tube;   an outer tube at least partially surrounding the inner tube and concentric with the inner tube;   a cap attached to the inner tube, wherein the cap has a longitudinally extending portion that extends in the longitudinal direction;   a connecting member attached to an end of the outer tube; and   an expansion element attached to the longitudinally extending portion of the cap, wherein the expansion element is attached to the connecting member, wherein the expansion element is located completely between the longitudinally extending portion of the cap and the connecting member in the longitudinal direction.   
     
     
         17 . The absorber tube as set forth in  claim 16 , wherein thermal expansion of the inner tube at a rate faster than thermal expansion of the outer tube causes the expansion element to expand in the longitudinal direction;
 wherein thermal contraction of the inner tube at a rate faster than thermal contraction of the outer tube causes the expansion element to contract in the longitudinal direction;   wherein the expansion element is located completely beyond the end of the outer tube in the longitudinal direction;   wherein the connecting member extends from the end of the outer tube such that the connecting member is located completely longitudinally beyond the outer tube.   
     
     
         18 . The absorber tube as set forth in  claim 16 , wherein a vacuum is formed in the space between the outer wall of the inner tube and the inner wall of the outer tube, and further comprising a getter located within the space between the outer wall of the inner tube and the inner wall of the outer tube. 
     
     
         19 . The absorber tube as set forth in  claim 18 , wherein the getter includes two pieces that are located at an angle of 180° from one another about the concentric axis of the inner tube and the outer tube. 
     
     
         20 . The absorber tube as set forth in  claim 18 , wherein at least a portion of the getter is located on the inner wall of the outer tube and is configured to change colors upon the introduction of air into the space between the outer wall of the inner tube and the inner wall of the outer tube.