title: High performance solar-selective absorbers using coated sub-wavelength gratings.
abstract: Spectral control of the emissivity of surfaces is essential for efficient conversion of solar radiation into heat. We investigated surfaces consisting of sub-wavelength V-groove gratings coated with aperiodic metal-dielectric stacks. The spectral behavior of the coated gratings was modeled using rigorous coupled-wave analysis (RCWA). The proposed absorber coatings combine impedance matching using tapered metallic features with the excellent spectral selectivity of aperiodic metal-dielectric stacks. The aspect ratio of the V-groove can be tailored in order to obtain the desired spectral selectivity over a wide angular range. Coated V-groove gratings with optimal aspect ratio are predicted to have thermal emissivity below 6% at 720K while absorbing >94% of the incident light. These sub-wavelength gratings would have the potential to significantly increase the efficiency of concentrated solar thermal systems.
authors.affiliation: Dept. of Electrical Engineering, Stanford University, Stanford, CA 94305 USA.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Sergeant
authors.forename: Mukul
authors.initials: M
authors.lastname: Agrawal
authors.forename: Peter
authors.initials: P
authors.lastname: Peumans
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D012031:Refractometry / Q000295:instrumentation*; D012993:Solar Energy; D014159:Transducers