Patent ID: 7552726

Claim:
A tubular radiation absorbing device for solar heating applications, which comprises a central tube ( 3 ); a glass tubular jacket ( 2 ) surrounding the central tube ( 3 ) so as to form a ring-shaped space ( 4 ) between the tubular jacket and the central tube; an expansion compensating device ( 10 ) connected between the central tube ( 3 ) and the glass tubular jacket ( 2 ), so that the tubular jacket and the compensating device are movable longitudinally relative to each other and so as to form an inner annular space ( 30 ) between the central tube ( 3 ) and the expansion compensating device ( 10 ); a connecting element ( 20 ) connecting an inner end ( 12 ) of the expansion compensating device ( 10 ) with the central tube ( 3 ) and extending from the inner end ( 12 ) of the expansion compensating device through said inner annular space ( 30 ), wherein said inner annular space ( 30 ) is divided into a first annular space ( 31 ) between the central tube ( 3 ) and the connecting element ( 20 ) and a second annular space ( 32 ) between the connecting element ( 20 ) and the expansion compensating device ( 10 ), said second annular space ( 32 ) being connected with an outer atmosphere; and at least one hydrogen window ( 50 ) arranged in the connecting element ( 20 ) so that the at least one hydrogen window ( 50 ) is protected from incident solar radiation by the expansion compensating device ( 10 ) and so that hydrogen collecting in the first annular space ( 31 ) passes through the at least one hydrogen window ( 50 ) into the second annular space ( 32 ) and subsequently escapes into the outer atmosphere.