Stability investigation of propylene glycol-based Ag@SiO2 nanofluids and their performance in spectral splitting photovoltaic/thermal systems

Abstract

One main challenge facing nanofluid filters in PV/T systems is their long-term dispersion stability. This work studies the stability of the Ag@SiO2 nanoparticles suspended in propylene glycol (PG)-based fluids for use as optical filters. These nanofluid filters are subjected to high temperature heating test and thermal cycling test to analyze their thermal stability and identify appropriate base fluids. The results of UV–Vis spectroscopy and visual inspection show that both the most concentrated Ag@SiO2/PG + water nanofluid and Ag@SiO2/PG nanofluid exhibit excellent thermal stability when heated to 95 °C and 120 °C, respectively and no agglomeration is observed for exposure to thermal cycling test. A theoretical model with the measured transmittance of the identified Ag@SiO2 nanofluids as the input is introduced to evaluate performance of the nanofluid filtered PV/T system by varying the nanoparticles concentration, optical path-length and concentration ratio. The results indicate that Ag@SiO2/PG + water filter and Ag@SiO2/PG filter for PV/T systems using silicon cells show the capability to increase the economic value of more than 30% at optimum nanoparticles concentration of 12.7 mg/L and optical path-length of 35 mm and 40 mm, respectively, when the concentration ratio varies from 1 to 30 suns.