Patent ID: 7240675

Claim:
A parabolic trough collector comprising individual absorber tubes ( 13 ) connected end-to-end and aligned coaxially with each other so that a heat transfer fluid is able to flow through said individual absorber tubes ( 13 ); glass tubes ( 15 ) enclosing the individual absorber tubes ( 13 ) so that the individual absorber tubes ( 13 ) connected with each other extend through the glass tubes ( 15 ); flexible unions ( 17 ) for compensating differing length changes of the individual absorber tubes and the glass tubes due to thermal expansion, said flexible unions ( 17 ) connecting opposite ends of each of the glass tubes to the individual absorber tubes ( 13 ) so that a space is formed between each of the glass tubes and the absorber tubes; and conical collars ( 20 ; 21 , 24 ) arranged on the glass tubes to partially or fully cover said flexible unions ( 17 ), said conical collars having outer sides facing away from the glass tubes; wherein said conical collars ( 20 ; 21 , 24 ) have mirror surfaces on said outer sides arranged to reflect radiation directed toward said flexible unions ( 17 ) so that said radiation reflected by the mirror surfaces passes through the glass tubes ( 15 ) and then onto the absorber tubes ( 13 ).