Comparison of Commercial Reflectometers for Solar Mirrors

Abstract

The important in-field characterization of solar mirror reflectance can be performed by a variety of commercial portable reflectometers. In this study the most common commercially available reflectometers are evaluated in a campaign comparing different reflector materials, covering a wide range of realistic reflectance and specularity values. Where possible, measurements are compared to reference values measured with laboratory equipment. In general, good agreement between measurements is detected for highly specular mirrors (average deviation 0.005±0.004) and methods for improvement are proposed when deviations are detected. Important differences between measurements are found for less specular reflectors, which are caused by the disparity of the measurement parameters of the devices. These differences confirm that detailed knowledge about the device characteristics is important, to be able to correctly interpret and utilize gained results, especially for soiled and degraded mirrors.