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Proceedings Paper

Shaping solar concentrator mirrors by radiative heating
Author(s): Roger Angel; Thomas Stalcup; Brian Wheelwright; Stephen Warner; Kimberly Hammer; Mira Frenkel
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Paper Abstract

Here we report a newly developed method for gravity sag molding of large glass solar reflectors, 1.65 m x 1.65 m square, with either line or point focus, and short focal length. The method is designed for high volume manufacture when incorporated into a production line with separate pre-heating and cooling. The tests reported here have been made in a custom batch furnace, with high power radiative heating to soften the glass for slumping. The mold surface is machined to the required shape as grooves which intersect the glass at cusps, reducing the mold contact area to <1%. Optical metrology of replicas made with the system has been carried out with a novel test using a linear array of coaligned lasers translated in a perpendicular direction across the reflector while the deviation of each beam from perfect focus is measured. Slopes measured over an array of 4000 points show an absolute accuracy of <0.3 mrad rms in sx and sy. The most accurate replicas we have made are from a 2.6 m2 point focus mold, showing slope errors in x and y of 1.0 mrad rms. The slump cycle, starting with rigid flat glass at 500C, uses a 350 kW burst of radiative heating for 200 seconds, followed by radiative and convective cooling.

Paper Details

Date Published: 7 October 2014
PDF: 6 pages
Proc. SPIE 9175, High and Low Concentrator Systems for Solar Energy Applications IX, 91750B (7 October 2014); doi: 10.1117/12.2062394
Show Author Affiliations
Roger Angel, College of Optical Sciences, The Univ. of Arizona (United States)
Steward Observatory, The Univ. of Arizona (United States)
REhnu, Inc. (United States)
Thomas Stalcup, Steward Observtory, The Univ. of Arizona (United States)
REhnu, Inc. (United States)
Brian Wheelwright, College of Optical Sciences, The Univ. of Arizona (United States)
Stephen Warner, Steward Observatory, The Univ. of Arizona (United States)
Kimberly Hammer, College of Optical Sciences, The Univ. of Arizona (United States)
Mira Frenkel, Steward Observatory, The Univ. of Arizona (United States)


Published in SPIE Proceedings Vol. 9175:
High and Low Concentrator Systems for Solar Energy Applications IX
Adam P. Plesniak; Candace Pfefferkorn, Editor(s)

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