Patent ID: 7637259

Claim:
A parabolic trough collector comprising: an absorber tube ( 13 ) through which a heat transfer fluid is able to flow; a parabolic reflector ( 11 ) that focuses solar radiation onto the absorber tube; cladding tubes ( 15 ) enclosing the absorber tube ( 13 ) so that the absorber tube ( 13 ) extends through the cladding tubes ( 15 ); compensation pieces ( 17 ) for compensating differing length changes of the absorber tube and the cladding tubes due to thermal expansion, said compensation pieces ( 17 ) connecting the cladding tubes ( 15 ) to the absorber tube ( 13 ) so that connection areas ( 50 ) are formed between the cladding tubes; and mirror collars ( 20 ) arranged around the cladding tubes in the connection areas to partially or fully cover said compensation pieces ( 17 ) to provide at least partial protection of the compensation pieces ( 17 ) from the solar radiation; wherein the mirror collars ( 20 ) each have at least one reflective metal surface facing away from the cladding tubes ( 15 ) and said at least one reflective metal surface reflects a part of the solar radiation directed toward the cladding tubes ( 15 ) so that said part of the solar radiation passes through the cladding tubes ( 15 ) to the absorber tube ( 13 ); and wherein said at least one reflective metal surface consists of at least one planar surface ( 30 ).