Rough metallic selective surfaces for solar energy applications

Laser Sintering of Tungsten Nanoparticles for Solar Thermal Receivers

“…This enables solar light to get absorbed but still have high IR reflectance. Since the wavelength of the IR radiation is almost ~10 times larger that the surface roughness, the surface starts to behave more like an effective medium [19] The Bruggeman theory is primarily used here due to the fact that it is accurate for a wide range of material ratios and is symmetric. Symmetric means that it does not matter which material is represented as an inclusion and which is specified as the matrix [20,21].…”

“…There is also sub-micron roughness on peaks and valleys that can contribute to increased solar absorption. This surface behaves as a graded index medium [13,19] when the roughness is sub-wavelength thus leading to increased solar absorptance. When the roughness is larger than the wavelength, the increased absorptance is due to the light getting trapped by multiple reflections.…”