Absorber pipe

1. An absorber pipe for solar collectors in solar-thermal power plants having at least one collector mirror, the absorber pipe comprising:

a metal pipe for conducting and heating a heat transfer medium;

a cladding pipe surrounding the metal pipe to form an annular space;

a wall running between the cladding pipe and the metal pipe, the wall sealing the annular space, wherein the wall comprises an outer ring, a transition element, an expansion bellows, and a connection element; and

a retaining device disposed in the annular space at least partially between the expansion bellows and the metal pipe, and having a receiving section configured to receive a getter material of a container filled with getter material, wherein the retaining device is fastened to one of the outer ring, the transition element, the expansion bellows, and the connection element.

2. The absorber pipe according to claim 1 , wherein the retaining device has a first region and a second region, wherein the getter material or the container filled with the getter material is disposed in the first region, a second container filled with protective gas is disposed in the second region, and wherein the first region is turned away from the at least one collector mirror and the second region is facing the at least one collector mirror.

3. The absorber pipe according to claim 1 , wherein the retaining device comprises a reflecting metal or a reflecting layer for reflecting solar radiation.

4. The absorber pipe according to claim 1 , wherein the retaining device comprises a cladding for protecting the getter material from solar radiation.

5. The absorber pipe according to claim 4 , wherein the cladding is wire mesh.

6. The absorber pipe according to claim 4 , wherein the cladding comprises a reflecting section for reflecting solar radiation.

7. The absorber pipe according to claim 4 , wherein the retaining device has a first end and a second end connected to one another by a connection element.

8. The absorber pipe according to claim 1 , further comprising a reflector disposed in the annular space, wherein the reflector is configured to reflect solar radiation into the metal pipe.

9. The absorber pipe according to claim 8 , wherein the wall transitions into the cladding pipe via a glass-metal connection, and wherein the reflector or the retaining device is disposed so that it protects the glass-metal connection from radiation.

10. The absorber pipe according to claim 1 , wherein the retaining device is fastened to the expansion bellows.

11. The absorber pipe according to claim 1 , wherein the retaining device is fastened to the transition element.

12. An absorber pipe for solar collectors in solar-thermal power plants having at least one collector mirror, the absorber pipe comprising:

a metal pipe for conducting and heating a heat transfer medium;

a cladding pipe surrounding the metal pipe to form an annular space;

a getter material disposed in the annular space for binding free hydrogen present in the annular space;

a reflector disposed in the annular space for reflecting solar radiation into the metal pipe, wherein the reflector has a housing with a storage section for fastening and for protecting getter material from the solar radiation;

a wall running between the cladding pipe and the metal pipe, the wall sealing the annular space, wherein the wall comprises an outer ring, a transition element, an expansion bellows, and a connection element; and

a retaining device disposed in the annular space at least partially between the expansion bellows and the metal pipe, and having a receiving section configured to receive a getter material or a container filled with getter material, wherein the retaining device is fastened to one of the outer ring, the transition element, the expansion bellows, and the connection element.

13. The absorber pipe according to claim 12 further comprising a metal wall that extends between the cladding pipe and the metal pipe, at least in sections, in order to seal the annular space, wherein the metal wall transitions into the cladding pipe via a glass-metal connection, and wherein the reflector is disposed so that it protects the glass-metal connection from the solar radiation.

14. The absorber pipe according to claim 13 , wherein the housing is fastened to the metal wall.

15. The absorber pipe according to claim 14 , wherein the housing is fastened to the connection element or to the expansion bellows.

16. The absorber pipe according to claim 12 , further comprising getter material disposed in a portion that is turned away from the collector mirror.

17. The absorber pipe according to claim 13 , wherein the metal wall comprises an outer ring and a transition element, and wherein the housing is fastened to the outer ring or to the transition element.

18. The absorber pipe according to claim 12 , wherein the reflector comprises a reflecting layer on the housing.

19. The absorber pipe according to claim 12 , wherein the reflector comprises a polished surface.

20. The absorber pipe according to claim 12 , wherein the storage section comprises one or more cavities into which getter material can be introduced.

21. The absorber pipe according to claim 20 , wherein the one or more cavities can be closed off by a closure.

22. The absorber pipe according to claim 15 , wherein the expansion bellows has an inner end and an outer end and the housing is fastened to the inner end.

23. The absorber pipe according to claim 16 , wherein the reflector is disposed in the portion that is turned away from the collector mirror.

24. The absorber pipe according to claim 12 , wherein the reflector comprises one or more planar reflecting sections.

25. The absorber pipe according to claim 12 , wherein the housing is fastened to the connection element.

26. The absorber pipe according to claim 12 , wherein the housing is fastened to the expansion bellows.