Sansom, Christopher L.Fernández-García, AránzazuKing, PeterSutter, FlorianGarcia Segura, Alejandro2017-07-102017-07-102017-06-29Christopher Sansom, Aránzazu Fernández-García, Peter King, Florian Sutter, Alejandro Garcia Segura, Reflectometer comparison for assessment of back-silvered glass solar mirrors, Solar Energy, Volume 155, October 2017, Pages 496-5050038-092Xhttp://dx.doi.org/10.1016/j.solener.2017.06.053https://dspace.lib.cranfield.ac.uk/handle/1826/12177This paper compares the two most common reflectometers used to assess the specular reflectance of back-silvered glass mirrors for Concentrating Solar Power (CSP) applications, namely the Device and Services (D&S) 15R-USB and the Abengoa Condor SR-6.1 instruments. Comparisons are first made between the two instruments themselves using a Gage Repeatability and Reproducibility (R&R) study. Results are given for the as-cleaned collector mirrors and then as the mirrors become naturally soiled over a one month period. The results of the Gage R&R study show that for the D&S the gage itself contributes 40.97% of the variability, whilst 59.03% is due to part-to-part (location on the mirror under investigation) variability. For the Condor we show that the % Contribution from the gage is 62.18% of the total variability with only 37.82% of the contribution attributable to the location dependent reflectance. The Condor has a wider acceptance angle, and over the reflectance range of 0.91–0.95 the condor was found to measure higher than the D&S by an average of 1.53%. The differences between the soiling results obtained from the two instruments are explained, and the results are used to derive a predictive model for the soiling of solar collectors. In conclusion, both instruments have advantages and shortcomings, and the factors that influence which instrument to select are discussed.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/ReflectometryOptical instrumentsSolar collectorCollectorSoilingArticle