Experimental Characterization of Aqueous Zinc Oxide Nanofluid for Liquid Spectral Beam Splitting Photovoltaic-Thermal (BSPVT) Systems

Photovoltaic-Thermal (PVT) systems suffer from a thermal-electrical efficiency trade-off due to module overheating under high solar irradiance. Spectral Beam Splitting (SBS) resolves this by selectively transmitting the PV-responsive solar spectrum while capturing non-useful wavelengths for thermal conversion. In this study, aqueous zinc oxide nanofluids at concentrations ranging from 0.01 wt% to 0.05 wt% were synthesized using probe ultrasonication with Sodium Dodecyl Sulfate (SDS) surfactant stabilization. Spectrophotometric characterization (200-2500 nm) was conducted to evaluate spectral transmissivity across the active bandwidth of crystalline silicon (c-Si) solar cells (751-1126 nm). Spectrophotometric characterization revealed that the 0.03 wt% formulation achieved maximum spectral selectivity, yielding a peak transmissivity of 85.48 % (average 74.45 % across the c-Si active region, while providing near-complete optical extinction (<5% transmission) in the UV (<350 nm) and deep NIR (>1400 nm) thermal bands. Thermophysical modeling of the optimal 0.03" wt" % nanofluid yielded a density of 997.25 kg/m³, a specific heat capacity of 4178.9" J/kg"â‹…"K" , and a thermal conductivity of 0.6001" W/m"â‹…"K" . These results validate 0.03 wt% aqueous zinc oxide as an efficient optical filter and thermal absorber for hybrid BSPVT applications.