Synchronous steam generation and heat collection in a broadband Ag@TiO2 core–shell nanoparticle-based receiver

Research in collection and conversion of solar energy has attracted an increasing interest because of the fact that conventional energy resources are becoming increasingly exhausted. For this reason, Ag@TiO 2 core–shell nanoparticles (NPs) with great absorptivity in the visible region were synthesized in this work. Subsequently, an experimental study on photo-thermal performances including steam generation and solar energy capture in a thermal receiver containing the Ag@TiO 2 NPs-based nanofluids was conducted. The effects of the NP concentration as well as the optical concentration were taken into consideration. The results showed that the nanofluids can be used for direct steam generation with a short period of solar irradiation time, even at the illumination intensity of 1 sun (1 sun   =   1   kW/m 2 ). An evaporation efficiency of 53.6% can be achieved when the NP concentration is only 200   ppm owing to local heating induced by the surface plasmon resonance of the NPs. In addition, it is found that the nanofluid with a lower NP concentration has a higher temperature rise during illumination. Our findings also showed that the absorbed solar energy is transferred preferentially into latent heat enthalpy and consumed for steam generation instead of heating the nanofluids.