Hybrid Au-ZnO/(water-ethylene glycol)-nanofluid based PV/T spectral beam splitter for efficient photo-harvesting
Sandesh S. Chougule, Bhagyashree A. Gaikwad, A. Inbaoli, Anand Ajayan, Sandip Saha, Patrice Estellé
Abstract
Persistent challenges in photovoltaic/thermal (PV/T) systems with nanofluids (NFs) arise from colloidal instability, reducing optical absorption and thermal conductivity, which this study addresses through the techno-economic analysis and performance evaluation of a hybrid Au- zinc oxide (ZnO)/(W-EG) nanofluids as a spectral splitter for enhanced photo-harvesting. ZnO nanosheets (NSs) and Au nanoparticles (NPs) were synthesised via a reagent-free electrophoretic method and citrate reduction. The hybrid Au-ZnO/(W-EG) NF, dispersed in a 50:50 W-EG mixture, exhibited a localized surface plasmon resonance (LSPR) peak at 540 nm and UV absorption at 370 nm, reducing UV transmittance to near zero while maintaining 87-97% visible transmittance at 5-50 ppm Au-NP concentrations. Stability tests showed the Au-ZnO/(W-EG) NF retained 90% absorption ( A/A 0 ) for over 100 h, outperforming ZnO/(W-EG) (<14 h). In a PV/T system under 1000 W/m 2 solar irradiance, the NF at 50 ppm achieved a total efficiency ( ) of 76.24% ( : 64.62%, : 11.62%), a 7.42-fold enhancement over 5 ppm ( : 70.97%), though decreased by 7.19% due to reduced transmission. Increasing m from 2 to 6 mL/min raised from 51.12% to 62.23% and from 12.01% to 12.06% ( t opt : 10 mm), while larger Au-NP sizes (20 to 60 nm) reduced by 6.5% at 5 ppm. The merit function (MF) increased from 1.793 to 2.025 with m, but decreased from 15.24% to 13.48%, reflecting a trade-off between energy quantity and quality. Overall, this hybrid NF offers superior spectral splitting and stability, positioning it as a promising candidate for advanced photo-harvesting.