Broad-band absorption and photo-thermal conversion characteristics of rGO-Ag hybrid nanofluids

In the current paper, the thermo-physical, optical and photo-thermal conversion characteristics of reduced graphene oxide nanosheets and silver nanoparticles suspended in water and water + ethylene glycol solution (1:1) were experimental investigated under indoor conditions. The results indicated that the hybrid nanofluids have a good solar absorption in both visible and near-infrared regions (220 - 1400 nm). Comparing transmission spectra and extinction coefficients of rGO-Ag/water and rGO-Ag/W + EG hybrid nanofluids it is found that the use of rGO-Ag/W + EG hybrid nanofluid is much more beneficial than the rGO-Ag/water nanofluid in solar applications. The rGO-Ag /water and rGO-Ag /W + EG hybrid nanofluids with 0.10 wt% exhibit a relative increase in the temperature difference by about 21 % and 37 % compared to the base fluids and also stored energy values of 4989 J and 5432 J respectively, after an irradiation time of 60 min. This study emphasized the solar potential of rGO-Ag hybrid nanofluids for improving the direct absorption solar collectors performance.