Nanoparticles based single and tandem stable solar selective absorber coatings with wide angular solar absorptance

Solar selective absorber coatings with wide angular solar absorptance aids in attaining high photo-thermal conversion efficiency for solar thermal systems. In this regard, nanoparticles-based absorber coatings were developed on stainless steel grade 304 by combining the impregnation method, solvothermal process, and dipcoating technique. Developed nanocomposite (SiO2 nanoparticles in transition metal oxide matrix) based single layer absorber coating with nano void textured surface, exhibits solar absorptance of 0.92 and spectral emittance of 0.12. MgF2 nanoparticles based anti-reflective layer on single-layer absorber coating improves the solar absorptance to 0.94 by destructive interference mechanism. Both nanoparticles based single and tandem absorber coatings show wide angular solar absorptance of 0.88 and 0.89, respectively, at an incidence angle of 50 degrees. Besides, developed absorber coatings show lower thermal emissivity of 0.17 and good photo-thermal conversion efficiencies at high operating temperatures (400-500 degrees C). These developed absorber coatings offer excellent thermal stability at an open atmospheric condition till operating temperature, such as 400 degrees C for 100 h. Selective nature with wide angular solar absorptance and low heat loss behaviour of stable absorber coating show the photo-thermal conversion efficiency of 91% can improve the performance of receiver tubes in solar thermal systems.