Parabolic trough solar collectors (PTSCs) are commonly used for applications that reach a temperature of up to 500 °C.  Recently, improving the efficiency of PTSCs has been the focus of research because PTSCs have advantages, such as cost and size reduction and improved optical and thermal performance.  This study summarizes relevant published research on the preparation, properties and experimental behavior of the optical and thermal properties of PTSCs. Analyzing of the thermal modeling method presents a steady and transient heat transfer analysis.  Optical efficiency depends on material properties, such as mirror reflectance, glass cover transmittance, receiver absorption–emission, intercept factor, geometry factor and incidence angle. Also analyzed and discussed are the models used in computational fluid dynamics to study the physical properties of PTSCs. Lastly, studies on PTSC performance and enhancement, including novel designs, enhancement of passive heat transfer and laden flows of nanoparticles inside the absorber tube, are presented and examined separately. Nanofluids have illustrated their advantages and ability to increase heat transfer rates. Moreover, other works that aimed to enhance the optical and thermal efficiency of PTSCs are evaluated.

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Parabolic trough solar collector systems are the most advanced concentrating solar power technology for large-scale power generation purposes. The current work reviews various selective coating materials and their characteristics for different designs in concentrating solar power. Solar selective absorbing coatings collect solar radiation and convert it to heat. To promote higher efficiency and lower energy costs at higher temperatures requires, this study aims to analyse the fundamental chemistry and thermal stability of some key coatings currently being used and even under investigation to find reasons for differences, information gaps and potential for improvement in results. In recent years, several novel and useful solar absorber coatings have been developed. However, qualification test methods such as corrosion resistance, thermal stability testing and prediction of service life, which have essential technical value for large-scale solar absorbers, are lacking. Coatings are used to enhance the performance of reflectors and absorbers in terms of quality, efficiency, maintenance and cost. Differentiated coatings are required as there are no uniformly perfect materials in various applications, working conditions and material variations. Much more knowledge of the physical and chemical properties and durability of the coatings is required, which will help prevent failures that could not be discovered previously.

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