Solar selective absorbers with foamed nanostructure prepared by hydrothermal method on stainless steel

•Selective absorber films, with unique foamed nanostructure, are firstly obtained by hydrothermal method on stainless steel, without using any porogen.•The films, which comprise large numbers of nanoparticle agglomerates and nanopores, display a solar absorbance of 0.92 and a thermal emittance of 0.12.•The films prove benign thermal stability and performance at 450 °C, without crackings within entire structure.•The strategy is especially simple, pollution-free, low-cost and novel.

Currently, solar absorber plays a key role among all components of the concentrating solar power (CSP) system, which is considered as an important way for solar energy utilization. Due to the outstanding features of surface texture, nano-structured materials have been extensively utilized for solar energy harvesting and conversion, but most of them were synthesized by expensive or complicated techniques. Herein, for the first time, solar selective absorbers with uniquely foamed nanostructure, are grown in situ by facile hydrothermal method on stainless steel, without using any porogen or template. The selective absorber films, which comprised a large number of nanoparticle agglomerates and nanopores, have a vital role on the solar selective absorptance owing to the increased optical path as well as enhanced sunlight trapping via foamed nanostructure. They show an excellent solar thermal performance with the solar absorptance and the thermal emittance of 0.92 and 0.12, respectively. Besides, the solar absorber films also exhibit considerable solar thermal performance and benign thermal stability at high temperature. Due to the relieving internal stresses from foamed nanostructure, there is no obvious cracking within the entire structure even after heat treatment. Consequently, the hydrothermal method used in the present investigation happens to be a novel, pollution-free, low-cost, and suitable for simultaneous mass production for large-size absorber films. Moreover, the pre-treatment of substrate and post-treatment of films are also very convenient and environmental, without any complex procedure. Accordingly, the resultant films with foamed nanostructure will have a good prospect as a new-family of solar selective absorbers, which may have a tremendous potential for industrial production in the future.

Graphical abstractHerein, for the first time, the solar selective absorbers with foamed nanostructure, are grown in situ by hydrothermal method on stainless steel, without using any porogen or template. The selective absorber films, which comprise a large number of nanoparticle agglomerates and nanopores, have benign solar selective absorption and thermal stability due to the excellent foamed nanostructure. The hydrothermal method used in preparation of selective absorber films happens to be a simple, convenient, no-polluting, and low-cost technique, besides being novel. Furthermore, the films have led to a new-family of solar selective absorbers which are very likely applied in large-scale industrial production of CSP sectors in the future.Figure optionsDownload full-size imageDownload as PowerPoint slide