High Temperature Oxido-Resistant mIcroteXtured Solar Absorbers – ASTORIX

The ASTORIX project aims to develop new absorption selective coatings for solar receivers installed in concentrated solar power (CSP) plants using central tower and linear Fresnel technologies working at temperatures above 500°C.

The objective is to combine new solar selective coatings based on materials known to sustain high temperatures, and microstructures able to maintain a low level of emissivity and improve the absorption. Indeed thermal losses in today receivers show a dramatic increase with temperature which strongly affects the yield of such plants.
To tackle corrosion issues and selective coatings instabilities at high temperatures, these optical absorbers stacks will be deposited based on nanostructured titanium aluminum alloys nitride and silicon carbide. These materials will be synthesized by magnetron sputtering and novel high plasma density hybrid PVD/PECVD processes at PROMES in a laboratory scale deposition tool, and in large industrial equipment at HEF able to demonstrate the production of solar receivers at pilot scale.

Microstructured layers, e.g. in the form of sub-wavelength periodic gratings combined with absorption coatings will be fabricated at LabHC on planar substrates and on tubes, using special writing lithography tools based on a unique patented phase mask technology which has already been set up to print gratings on cylinders.

Specific laboratory simulation tools using rigorous electromagnetic codes (e.g. rigorous coupled wave analysis, RCWA) will be used to calculate the optical absorption and emissivity. Due to the new aspect of having a structured multilayered surface, these codes will have to be further developed to account for effects that are at present usually neglected like strong angular sensitivity of absorption and emission or non-homogeneous temperature distribution in the absorber volume, which requires to take the actual distribution of radiation sources inside the layered structure into account. These numerical simulations will allow a rigorous calculation of the optical and thermal properties of receivers to eventually design an optimized combination of selective coatings and microstructures.

Fatigue, creep and corrosion behavior as well as microstructural stability of the receivers will be studied using samples excerpted from stainless steel coated tubes and flat plates having been subjected to high concentration solar radiation aging cycles at PROMES furnaces and across accelerated creep-fatigue laboratory tests under oxidizing environment at SMS-ARMINES.

The final goal is to develop new highly efficient solar receivers with strongly enhanced optical characteristics for high temperature applications.