Design of Solar Absorbers Based on Micro- and Nanostructured Materials

This chapter applies micro/nano structured designs to the development of high-efficiency solar absorbers for solar thermal utilization. The chapter first introduces a two-dimensional multilayer metal-dielectric-metal pyramid array absorber. Using refractory materials like Ni, the design ensures excellent thermal stability for high-temperature applications. The absorber achieves an average absorption rate of 99.28% in the ultraviolet to near-infrared (0.3–2.5 μm) range by leveraging the slow light effect and surface plasmon resonance, resulting in a photothermal conversion efficiency of 96.45%. Building on this, the chapter proposes a multilayer flat-structured absorber based on TiN. This structure utilizes the superposition of multiple Fabry-Perot resonances within coupled cavities to achieve broadband absorption (93.5% for three units). The chapter systematically investigates the influence of geometric parameters, material selection, and incident angles, demonstrating that the absorbers remain highly efficient even under large-angle incidence of up to 60°. Additionally, it explores performance under concentrated solar power conditions, showing that high conversion efficiency is maintained at elevated temperatures. These designs offer stable, high-performance solutions for solar thermal systems, emphasizing the importance of multi-mode coupling and structural optimization in matching the absorber's response to the solar spectrum while minimizing thermal re-emission.