Multi-Scale Femtosecond-Laser Texturing for Photothermal Efficiency Enhancement on Solar Absorbers Based on TaB2 Ceramics

Abstract

Tantalum boride is an ultra-refractory and ultra-hard ceramic known so far for its favorable high-temperature thermo-mechanical properties and also characterized by a low spectral emittance, making it interesting for novel high-temperature solar absorbers for Concentrating Solar Power. In this work, we investigated two types of TaB2 sintered products with different porosities, and on each of them, we realized four femtosecond laser treatments differing in the accumulated laser fluence. The treated surfaces were then characterized by SEM-EDS, roughness analysis, and optical spectrometry. We show that, depending on laser processing parameters, the multi-scale surface textures produced by femtosecond laser machining can greatly increase the solar absorptance, while the spectral emittance increase is significantly lower. These combined effects result in increased photothermal efficiency of the absorber, with interesting perspectives for the application of these ceramics in Concentrating Solar Power and Concentrating Solar Thermal. To the best of our knowledge, this is the first demonstration of successful photothermal efficiency enhancement of ultra-hard ceramics using laser machining.

Processing and Optical Behavior of Dense (Hf,Zr)B2 Solid Solutions for Solar Energy Receivers

“…If we consider the ratio R e-p between the spectra of etched and pristine sample, its value is the lowest in the range ~1.3-2.0 μm Following the approach shown in Refs. [33,34], the obtained result on optical properties can be qualitatively explained in terms of the structures created by the etching treatment and their sizes. The involved light-material interaction phenomena are light trapping (when the radiation wavelength is similar to the size of surface features) and increase the effective surface (when the surface features are much larger than radiation wavelength).…”

“…From the α and ε parameters, it is possible to evaluate the optothermal conversion efficiency of the solar absorber, defined as [34]:…”