Shaping solar concentrator mirrors by radiative heating

J Roger P Angel, Thomas Stalcup, Brian Wheelwright, Stephen Warner, Kimberly Hammer, Mira Frenkel

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations

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 m<sup>2</sup> 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.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherSPIE
Volume9175
ISBN (Print)9781628412024
DOIs
StatePublished - 2014
EventHigh and Low Concentrator Systems for Solar Energy Applications IX - San Diego, United States
Duration: Aug 19 2014Aug 20 2014

Other

OtherHigh and Low Concentrator Systems for Solar Energy Applications IX
CountryUnited States
CitySan Diego
Period8/19/148/20/14

Keywords

  • furnace
  • glass shaping
  • mirror fabrication
  • second-surface
  • slope metrology
  • Solar reflectors

ASJC Scopus subject areas

  • Applied Mathematics
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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