Heliostat glass survey and analysis

Abstract

A comprehensive survey of both foreign and domestic sources of low distortion, high transmission flat glass with a nominal thickness of 3 mm was undertaken. The purpose of the survey was to determine the characteristics, availability and cost of glass for use in second surface heliostat mirrors for the Barstow pilot plant and future commercial central receiver plants. Information obtained from the manufacturers and the results of investigations performed at Sandia Laboratories at Albuquerque and Livermore were compiled with the PNL characterization data to generate the specifications for the GFE glass to be used in the Barstow pilot plant. During the course of the survey, nine of the major glass manufacturers were contacted for information and assistance. These manufacturers were PPG, Corning, Ford, LOF, CE, ASG, Fourco, Schott, and Guardian. Eleven different flat glass samples from seven of the domestic sources and one foreign source were characterized for solar transmittance, flatness and durability. The samples were representative of four different manufacturing processes: float, fusion, rolled, and twin ground. The results and implications of these glass characterization studies and a brief summary of the manufacturer survey are presented.