Investigation and review of mirrors reflectance in parabolic trough solar collectors (PTSCs)

As mirrors used in concentrating solar systems influence the thermal efficiency of the systems collectors to a large extent, the reflectance of mirrors plays a critical role in the thermal efficiency of parabolic trough solar collectors. The studies already done by scientists in terms of how to prepare mirrors of high reflectance and quality to be used in parabolic trough solar collectors are investigated in this review paper. In other words, the paper is aimed at investigating the reflectance of various mirrors already studied by researchers as an important parameter influencing the thermal efficiency of parabolic trough solar collectors. This influence is numerically shown through two instances applied in a case study. Many factors and preparation methods influencing solar mirrors reflectance and quality including mirror preparation technique, mirror material, and material configuration, which were studied by scientists, are investigated. In addition, the useful and important strategies, already studied, influencing the reflectors performance and quality are discussed within the paper sections and briefly through tables. Finally, although a nearly ideal reflectance of about 0.99 in both silver and aluminum mirrors - as the most common and efficient mirrors - has been achieved by scientists, it becomes evident that more work is still required to be done in the future in order to achieve mirrors of ideal reflectance and quality. (C) 2019 Published by Elsevier Ltd.