New Technologies and Materials for Solar-Selective Coatings

Dear Colleagues,

The development of solar selective coatings is one of the major challenges for solar thermal systems, which convert solar radiation to heat using line and point focusing technologies. The generated heat can be utilized for process heating, cooling, and power generation. The spectrally selective nature of the coating is essential to maximize the absorption of solar radiation in the ultraviolet (UV) to infrared (IR) spectrum and to minimize the emission of thermal radiation at a higher wavelength. The design of spectrally selecting materials, to achieve these properties, is very challenging. There are different coating structures consisting of single-layer hybrid coatings, i.e., high metal content in the ceramic hosts viz. CERMET, the multilayer structures comprising a high and a low metal volume fraction in oxide hosts, and even multi-layer metal/semiconductor structures, with their relative merits and demerits. Because of thermal and environmental degradation the current state-of-the-art technologies are using solar selective coatings under vacuum. Thus, there is a strong need to develop high-temperature and environmentally stable coatings, which can withstand harsh operating conditions and enhance the heat transfer efficiency to a fluid medium. The multifunctional nanostructured pristine and composite coating materials, inkling air stable oxides, are considered the potential candidates for the next generation spectrally selective coatings, which may offer the desired physical, chemical, and optical characteristics, essential for solar thermal applications.

The different design geometries need to be explored with specific materials, which can meet the requirement of spectrally selective coatings for solar thermal applications. These coatings can be realized using different coating techniques; however, the emphasis on their scaling must be considered for any futuristic, high-temperature, solar thermal systems/sub-systems to address the need for green energy. Thus, considering the need of the hour, the present Special Issue will focus on, but is not limited to, the following concepts:

• Recent developments and current trends in solar selective coatings;
• The theoretical and experimental design aspects of spectrally selective coatings;
• Thermally and environmentally stable, composite and multilayer, coating structures;
• Efficient characterization strategies for the spectrally selective coatings;
• Different coating methods for spectrally selective coatings and their scale-up strategies;
• Computational modeling and simulation for solar selective coatings with their solar thermal properties;
• Machine learning-based materials selection for the highly stable solar thermal coatings;
• System level development for absorber tube coatings for the solar thermal systems.

Dr. Ambesh Dixit
Dr. Raju Kumar Gupta
Dr. Laltu Chandra
Guest Editors

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• solar/spectrally selective coatings
• absorber tube
• thermal emittance
• multilayer coatings
• thermal and corrosion resist spectrally selective coating