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Proceedings Paper

Contactless two-stage solar concentrators for tubular absorber
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Paper Abstract

Two new types of two-mirror solar concentrator for tubular receiver, the snail concentrator and the helmet concentrator , are presented. The main feature of these concentrators is that they have a sizable gap between the secondary mirror and the absorber, and they still achieve concentrations close to the thermodynamic limit with high collection efficiencies. This characteristic makes them unique and, on the contrary to the present two-stage designs, allows for the location of the secondary outside the evacuated tube. One of the differences between the snail and the helmet concentrators is that the last is symmetric (as the conventional parabolic trough) but the first is not. For an acceptance angle of (alpha) equals +/- 0.73 degs and a collection efficiency of 96.8% (i.e. 3.2% of the rays incident on the primary mirror within the acceptance angle are rejected), the snail concentrator and the helmet concentrator achieve an average flux concentration of 91.1% and 72.8% of the thermodynamic limit, respectively. The gap between the absorber and the secondary mirror is 6.8 and 12.1 times the absorber radius for each concentrator. Moreover, both concentrators have also high rim angles of the primary mirror: +/- 86.2 degs (helmet) and 3.1 - 98.8 degs (snail). This is of interest for a good mechanical stability of the collector.

Paper Details

Date Published: 3 October 1997
PDF: 12 pages
Proc. SPIE 3139, Nonimaging Optics: Maximum Efficiency Light Transfer IV, (3 October 1997); doi: 10.1117/12.290219
Show Author Affiliations
Pablo Benitez, Instituto de Energia Solar (Spain)
Juan Carlos Minano, Instituto de Energia Solar (Spain)
Raphael Garcia, Instituto de Energia Solar (Spain)
Ruben Mohedano Arroyo, Instituto de Energia Solar (Spain)

Published in SPIE Proceedings Vol. 3139:
Nonimaging Optics: Maximum Efficiency Light Transfer IV
Roland Winston, Editor(s)

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