Structural and optical properties of copper-coated substrates for solar thermal absorbers

Abstract

a b s t r a c tSpectral selectivity, i.e. merging a high absorbance at sunlight wavelengths to a low emittance at the wavelengths of thermal spectrum, is a key characteristics for materials to be used for solar thermal receivers. It is known that spectrally selective absorbers can raise the receiver efficiency for all solar thermal technologies. Tubular sunlight receivers for parabolic trough collector (PTC) systems can be improved by the use of spectrally selective coatings. Their absorbance is increased by deposing black films, while the thermal emittance is minimized by the use of properly-prepared substrates. In this work we describe the intermediate step in the fabrication of black-chrome coated solar absorbers, namely the fabrication and characterization of copper coatings on previously nickel-plated stainless steel substrates. We investigate the copper surface features and optical properties, correlating them to the coating thickness and to the deposition process, in the perspective to assess optimal conditions for solar absorber applications.

Thermal Emittance Measurement of Very Low-Emissive Materials for Solar Thermal Applications

“…SSAs with excellent optical properties have been designed and realized for middle-temperature solar thermal applications (De Maio et al, 2022). Ongoing research in the HVFPC field aims not only to reduce thermal emittance on the front side of the absorber but also to minimize power emitted from the back side towards the panel bottom case by developing selective solar absorbers (SSA) on low-emissive coated substrates (Caldarelli et al, 2023) Copper (Cu) is a highly promising material for low-emissive SSA substrates, as it exhibits extremely low thermal emittance (ε < 0.02) (Querry, 1985) also in the form of thin films (Pratesi et al, 2016).…”

Optical properties of titanium oxynitride thin films and application in selective solar absorber

“…In the solar thermal energy systems, the SSA is one of the key units [203]. To reduce the cost, a glass substrate is widely used [204,205], and a metallic thin film (e.g., Cu, Al, Mo, etc.)…”