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Matrix approach for testing mirrors. Part 1

The purpose of this report is to describe the development of a matrix approach for testing mirrors (MATM) to be used for outdoor solar concentrators. The method resulted from a cooperative effort by several national laboratories. The MATM systematically subjects mirrors to accelerated and abbreviated exposures to significant environmental conditions encountered in solar applications (such as water vapor, pollutants, elevated temperature, temperature cycles, and ultraviolet light) that can lead to corrosion and reduced specular reflectance. The objective of the first phase of this project was to collect baseline data on degradation rates for exposure of a number of types of mirrors to temperatures and water vapor. Techniques for characterizing mirror corrosion were also surveyed (such as reflectance, light scattering, optical microscopy, and surface analysis). The results of the first phase of the MATM validate the basic experimental approach selected. The results also validate eliminating temperature cycling from the second phase of the project and reducing the number of optical characterization measurements to the spectral, hemispherical, and diffuse reflectance; image analysis; and light scattering at 400 nm.