Absorption characteristics and solar absorption capacity of Au core NR coated with various shell material.

Au nanorods (NRs) can be used to improve the performance of direct absorption solar collectors (DASCs), however, the solar absorption of Au NRs should be further improved because the absorption of Au NRs in near-infrared range is strong while the absorption in visible range is relatively weak where the solar spectrum intensity is the strongest. Based on this tissue, a composite nanostructure composed of Au core NR and Mg shell is proposed to improve the solar absorption capacity. The choice of Mg material as the shell composition is explained. By optimizing the composition structure, the enhancement effect on the absorption properties of Au@Mg NR from visible range to near-infrared range is proven by the finite element method. Furthermore, the effect of imperfect shell on absorption capacity of Au@Mg NR is discussed. Finally, the DASCs performance based on optimal Au@Mg NR nanofluids is evaluated. The results show that when the volume fraction is lower than 2 ppm and the collector depth is 2 cm, the highest solar energy harvesting capacity (>92%) using Au@Mg NRs nanofluids can be obtained, showing an excellent Au-based material for DASCs application.