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 (> 700°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-weighted absorptance of > 97.75 ± 0.04% after ageing at 850°C for more than 2,000 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.