Optical Characterization Of Nanoparticles For Solar Energy Absorption

Solar energy is a highly competitive new energy source that meets the current trend.Its advantages of complete cleanliness,wide distribution and high energy quality make it strategically important in alleviating the energy crisis and adjusting the energy structure.Photothermal conversion is the most direct form of utilization in solar energy development,and the efficient absorption of solar energy is fundamental to its utilization.However,there are significant limitations in solar absorption efficiency with conventional surface-based absorption systems.To overcome the limitations of conventional solar collectors,researchers have proposed direct absorption solar collectors（DASC）to improve solar absorption efficiency.But conventional base working fluids（e.g.,water）typically have poor optical and thermophysical properties,resulting in low thermal efficiency.In response to the above problems,an in-depth study on the optical properties of nanoparticles for DASC is carried out in this paper.Three special structures of nanoparticles based on localized surface plasmon resonance（LSPR）,propagating surface plasmon resonance（PSPR）and magnetic resonance are proposed to achieve efficient absorption of solar energy.The following is the main research work of this paper:1.The optical properties of plasma dimer silver（Ag）nanoparticles are investigated.Based on LSPR,the plasma dimeric Ag nanoparticles produce multiple absorption peaks,which broadens the absorption band of solar energy.The resonance modes of the plasma dimer are discussed by analyzing the electromagnetic fields of nanoparticles.The effects of nanoparticle geometry and the embedding of two spheres on the optical properties are investigated.Furthermore,the effect of the trimer and its special structure on its optical properties is analyzed.The results show that the proposed plasma dimer Ag nanoparticles have promising applications in solar thermal conversion technology.2.A SiO₂@Au core-shell composite nanorods for improving the absorption performance of DASC is proposed and investigated.The optical properties are numerically simulated by the finite element method.The results show that the core-shell composite nanorods can improve the absorption efficiency of DASC for the full spectral region of solar energy.The efficient uptake mechanism can be attributed to the coupling effect of LSPR and PSPR.The solar absorption efficiency of the composite nanorod suspension（nanofluid）can be as high as 95.3% under AM 1.5 radiation spectrum.Notably,we also consider the effects caused by imperfect shells during the experimental synthesis.3.A dumbbell-type nanorod that can excite both electrical and magnetic resonance is proposed.Due to the coupling between electrical and magnetic resonance,the dumbbell-shaped nanorods can excite multiple absorption peaks to enhance absorption while reducing scattering.Analysis of the slotted positions of the dumbbell-shaped nanorods shows that the slotting should not occur at the ends of the nanorods.It is shown that the optical properties of dumbbell-type nanorods can be effectively tuned by adjusting the geometric parameters of the slot.The dumbbell-shaped nanorods are expected to be used for solar photothermal conversion and could be a candidate material for the working fluid in DASC.