Novel highly performing tandem selective solar absorber for industrial heat applications

The needed decarbonisation of the industrial sector for an efficient transition to a Net Zero future, alongside the lack of commercially competitive solar absorbers for industrial heat applications using small non-evacuated receiver tubes, has motivated the design of a new highly stable material suitable for the open-air conditions. This work demonstrates that the potential candidate is the CuCoMnO_x/SiO₂ tandem selective absorber, designed to coat line-focussed receiver tubes to supply thermal energy up to 450 °C for industrial process heat applications. Remarkably, with only two layers deposited on stainless-steel (SS) under optimised conditions, the material exhibits excellent optical performance, achieving a α_s > 0.95 and a ε_350°C = 0.16. The absorber design prioritises cost-effective industrialisation by optimising thermal treatment to lower both temperature and duration time, while fine-tuning layer thicknesses to locate optical interferences at the required wavelengths. This approach ensures outstanding reproducibility, uniformity, and efficiency, marking the first successful deposition of coatings on tubular forms. The coatings composing the absorber are characterised optically, by X-ray diffraction, scanning electron microscope, and thermogravimetric and differential scanning calorimeter techniques. In terms of durability, the absorber shows extraordinary resilience, maintaining thermal stability for 27 months at 400–450 °C in open air, and exhibiting good resistance to condensation (PC = 0.03 in the most drastic situation). Therefore, the SS-substrate/CuCoMnO_x/SiO₂ absorber emerges as a promising commercial material for both evacuated and non-evacuated receiver tubes, promoting the integration of concentrating solar power (CSP) technology with solar heat for industrial processes (SHIP).