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Title: Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix

Abstract

Concentrating solar power (CSP) companies have deployed thin-glass mirrors produced by wet-silver processes on {approx}1-mmthick, relatively lightweight glass. These mirrors are bonded to metal substrates in commercial installations and have the confidence of the CSP industry. Initial hemispherical reflectance is {approx}93%-96%, and the cost is {approx}$$16.1/m{sup 2}-$$43.0/m{sup 2}. However, corrosion was observed in mirror elements of operational solar systems deployed outdoors for 2 years. National Renewable Energy Laboratory (NREL) Advanced Materials Team has been investigating this problem. First, it was noted that this corrosion is very similar to the corrosion bands and spots observed on small (45 mm x 67 mm) thin-glass mirrors laminated to metal substrates with several different types of adhesives and subjected to accelerated exposure testing (AET) at NREL. The corrosion appears as dark splotches in the center of the mirror, with a corresponding 5%-20% loss in reflectivity. Secondly, two significant changes in mirror manufacture have occurred in the wet-chemistry process because of environmental concerns. The first is the method of forming a copper-free reflective mirror, and the second is the use of lead-free paints. However, the copper-free process requires stringent quality control and the lead-free paints were developed for interior applications. A test matrix of 84 combinations of sample constructions (mirror type/backprotective paint/adhesive/substrate) was devised for AET as a designed experiment to identify the most-promising mirrors, paints, and adhesives for use with concentrator designs. Two types of accelerated exposure were used: an Atlas Ci5000 WeatherOmeter (CI5000) and a BlueM damp-heat chamber. Based on an analysis of variance (ANOVA), the various factors and interactions were modeled. These samples now have more than 36 months of accelerated exposure, and most samples have completed their test cycle. We will discuss the results of the final exposure testing of these mirror samples. Glass mirrors with copper back-layers and heavily leaded paints have been considered robust for outdoor use. However, the basic mirror composition of the new mirrors is radically different from that of historically durable solar mirrors, and the outdoor durability must be determined.

Authors:
; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
981974
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: Proceedings of Energy Sustainability 2007 (ES2007), 27-30 June 2007, Long Beach, California
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ADHESIVES; BETA-AMINOETHYL ISOTHIOUREA; COPPER; CORROSION; ENERGY; GLASS; INDUSTRY; INTERACTIONS; METALS; METHYL METHANESULFONATE; MIRRORS; NATIONAL RENEWABLE ENERGY LABORATORY; PAINTS; POWER; PROCEEDINGS; QUALITY CONTROL; REFLECTIVITY; SOLAR SYSTEM; SUBSTRATES; TESTING; Solar Energy - Photovoltaics

Citation Formats

Kennedy, C. E., Terwilliger, K., and Jorgensen, G. J.. Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix. United States: N. p., 2007. Web.
Kennedy, C. E., Terwilliger, K., & Jorgensen, G. J.. Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix. United States.
Kennedy, C. E., Terwilliger, K., and Jorgensen, G. J.. Mon . "Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix". United States. doi:.
@article{osti_981974,
title = {Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix},
author = {Kennedy, C. E. and Terwilliger, K. and Jorgensen, G. J.},
abstractNote = {Concentrating solar power (CSP) companies have deployed thin-glass mirrors produced by wet-silver processes on {approx}1-mmthick, relatively lightweight glass. These mirrors are bonded to metal substrates in commercial installations and have the confidence of the CSP industry. Initial hemispherical reflectance is {approx}93%-96%, and the cost is {approx}$16.1/m{sup 2}-$43.0/m{sup 2}. However, corrosion was observed in mirror elements of operational solar systems deployed outdoors for 2 years. National Renewable Energy Laboratory (NREL) Advanced Materials Team has been investigating this problem. First, it was noted that this corrosion is very similar to the corrosion bands and spots observed on small (45 mm x 67 mm) thin-glass mirrors laminated to metal substrates with several different types of adhesives and subjected to accelerated exposure testing (AET) at NREL. The corrosion appears as dark splotches in the center of the mirror, with a corresponding 5%-20% loss in reflectivity. Secondly, two significant changes in mirror manufacture have occurred in the wet-chemistry process because of environmental concerns. The first is the method of forming a copper-free reflective mirror, and the second is the use of lead-free paints. However, the copper-free process requires stringent quality control and the lead-free paints were developed for interior applications. A test matrix of 84 combinations of sample constructions (mirror type/backprotective paint/adhesive/substrate) was devised for AET as a designed experiment to identify the most-promising mirrors, paints, and adhesives for use with concentrator designs. Two types of accelerated exposure were used: an Atlas Ci5000 WeatherOmeter (CI5000) and a BlueM damp-heat chamber. Based on an analysis of variance (ANOVA), the various factors and interactions were modeled. These samples now have more than 36 months of accelerated exposure, and most samples have completed their test cycle. We will discuss the results of the final exposure testing of these mirror samples. Glass mirrors with copper back-layers and heavily leaded paints have been considered robust for outdoor use. However, the basic mirror composition of the new mirrors is radically different from that of historically durable solar mirrors, and the outdoor durability must be determined.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

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