Asymmetrical cone-type secondary concentrators for Fresnel type reflectors in solar towers

Wolfgang Spirkl*, Andreas Timinger, Harald Ries, Abraham Kribus, Julius A. Muschaweck

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations


In solar tower plants, where a rotationally symmetric field of heliostats surrounds the tower, an axisymmetric secondary concentrator such as a Compound Parabolic Concentrator (CPC) or a tailored concentrator or a cone is the obvious choice. For locations at higher latitudes, however, the reflecting area of the heliostats may be used more efficiently if the field of heliostats is located opposite to the sun as seen from the tower. Then the field is asymmetric with regard to the tower. In the case of an asymmetric field, an axisymmetric concentrator necessarily has a concentration significantly lower than the upper limit. Furthermore, the area on the ground from which a tilted axisymmetric concentrator accepts radiation is an ellipse, including also heliostats very distant to the tower producing a large image of the sun. Therefore we investigate asymmetric secondaries. From the shape of the edge ray reflectors constructed for rays in the central south-north plane we conclude that a skew cone reflector might be appropriate for the field and optimized its free parameters by means of raytracing. Asymmetric concentrators may increase the concentration by up to 25% at the same efficiency compared to optimized axisymmetric CPC or cone reflectors.

Original languageEnglish
Pages (from-to)86-93
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1997
Externally publishedYes
EventNonimaging Optics: Maximum Efficiency Light Transfer IV - San Diego, CA, United States
Duration: 27 Jul 199727 Jul 1997


  • Nonimaging optics
  • Raytracing
  • Secondary concentrators
  • Solar tower plants


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