Solar vapor generation using bubbly flow nanofluids with collaborative light-harvesting nanoparticles

Nanotechnology can produce metallic particles of nanometer sizes with unique optical and thermal properties. Utilizing the nanofluid in solar systems has distinct advantages over conventional fluids in light harvesting, thermal generation and heat transport. However, the plasmonic effect only induces strong light absorption around its nature resonance peak, which is not desirable for broadband solar absorption. Herein, we propose a composite nanofluid composed of three different kinds of particles with distinguish absorbance peaks for collaborative light absorption over the entire solar spectrum. Dynamic bubbles are further introduced into the nanofluid to promote the solar vapor generation. With light absorption spanning from ultraviolet, visible to near-infrared wavelengths, these particle-bubble couplings induce multiple scattering events, increasing photon absorption and light flux within local domain, leading to intensive heating that activates phase-change evaporation in the close proximity. The bubbly flow nanofluid exhibits the best photothermal efficiency of 91.2% than that of the other counterparts, enabling fast vapor diffusion with an upward bubble-bursting flow, and therefore achieving a decent steam generation efficiency of 40.8% under one-sun irradiation. Our findings not only suggest a new way to improve solar vapor generation in laden-particle solution, but also shed lights on the development of novel solar thermal systems.