Highly efficient and durable solar thermal energy harvesting via scalable hierarchical coatings inspired by stony corals

Concentrating solar thermal (CST) is an efficient renewable energy technology with low-cost thermal energy storage. CST relies on wide-spectrum solar thermal absorbers that must withstand high temperatures (>600 °C) for many years, but state-of-the-art coatings have poor optical stability. Here, we show that the largely overlooked macro-scale morphology is key to enhancing both optical resilience and light trapping. Inspired by stony-coral morphology, we developed a hierarchical coating with three tuneable length-scale morphologies: nano- (∼120 nm), micro- (∼3 μm) and macro-scales (>50 μm). Our coating exhibits outstanding, stable solar absorptance of >97.75 ± 0.04% after ageing at 850 °C for more than 2000 hours. The scalability of our coating is demonstrated on a commercial solar thermal receiver, paving the way for more reliable high-performance solar thermal systems.