Thermo-optical performance of iron-doped gold nanoshells-based nanofluid on direct absorption solar collectors

Abstract

Nanofluids are potential working fluids for Direct Absorption Solar Collectors, mainly due to the enhancement of the optical absorption by the presence of metallic nanoparticle inclusions. For instance, Gold Nanoshells (Au NS) have absorption spectrums in the visible–NIR spectrum that can be tuned controlling their size in the chemical synthesis. The use of metallic nanoheaters in photo-thermal applications requires finding nanostructures with high optical absorption features and low optical scattering properties, which could be achieved by doping gold with transition metals impurities, such as Pt, Fe, or Ag. In this work, a numerical analysis is used to determine the proper fraction of Fe-doping Au NS to increase the solar energy efficiencies of plasmonic nanofluids. In our knowledge, it is the first time this kind of nanofluid is proposed for solar harvesting applications. The results show that the solar weighted absorption efficiency of Fe-doped Au NS based nanofluids is sensibly enhanced and improved the performance of direct solar absorption collectors by increasing the optical absorption cross-section of plasmonic nanoparticles. The collector using Fe-doped gold nanoshells based nanofluids can reach thermal efficiency above 95% at 1 kWm−2, and in a very dilute condition (volume fraction of p=2×10−5). This value is up to 20% superior to that of pure Au NS based working fluids. These results demonstrated that adjusting the proper fraction of Fe as a dopant into the Au layer of nanostructure provides a novel approach to harvesting solar energy flux under optimal conditions.