This 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

Concentrating solar thermal technologies have experienced an important boost in the last few years. Besides the production of electricity, they are particularly useful for the supply of industrial process heat. The industrial atmospheres affecting these solar plants typically contain gaseous pollutants that are likely to promote corrosion on the components of the solar facility, specifically solar reflectors, thereby compromising their optimal performance and the overall system efficiency. Seven accelerated aging tests were designed to study the effects of three air pollutants (H₂S, SO₂ and NO₂) on the durability of two commercially available reflector types (silvered-glass and aluminum), both in single-gas tests and in multicomponent gas mixtures. Additionally, the same material types were exposed outdoors at five representative polluted sites, including industrial, urban and coastal environments. Reflectance and optical microscope monitoring corroborated which degree of corrosion was developed on a specific type of reflector in the different tests with gaseous pollutants, as well as the synergistic effects of gas combinations. For example, tests with sulfur were harmful for silvered-glass reflectors (up to a total of 16 corrosion spots), whereas aluminum was particularly affected by tests with NO₂ (numerous micro spots of around 50 μm size). Moreover, comparisons of the corrosion patterns found in accelerated-aging and outdoor exposures revealed which laboratory test reproduced the different real polluted atmospheres in the most realistic way, which is the main goal of this work. For instance, the degradation found at Site 2 was reproduced by Test NO₂+SO₂, with an acceleration factor of 27.

Concentrating solar thermal (CST) technologies are a feasible and promising option to tackle worldwide energy problems. These solar facilities are sometimes located near industrial sites, where their main components—including concentrating solar reflectors—are prone to significant degradation caused by corrosive agents, especially in the presence of sulfurous atmospheres such as H₂S and SO₂. This paper focuses on analyzing the influence of sulfurous atmospheres on the durability of reflector materials used in CST technologies. To this end, accelerated aging tests were performed on the most commonly used materials found in solar reflectors (i.e., thick silvered glass and aluminum-based reflectors) by applying the same concentrations of H₂S and SO₂ under the same conditions of temperature and relative humidity. The results showed that the solar reflectors based on a silver reflective layer are significantly corroded by H₂S atmospheres—several corrosion defects were found in the samples tested. However, those based on aluminum were barely affected by sulfurous environments in the conditions tested. Nonetheless, the study suggests that both reflector types are suitable candidates, depending on the purpose of the CST technology in question and the specific environmental conditions.