Experimental investigation of a TiO2 nanofluid spectral beam-splitting photovoltaic-thermal system under outdoor conditions

This paper presents the design, fabrication, and experimental validation of a fluid-based spectral beam-splitting photovoltaic–thermal (BSPVT) system using a TiO 2 nanofluid filter. A modular setup was developed comprising a hinged mild steel frame to accommodate the PV panel and fluid filter, a circulation system for controlled fluid flow, and integrated instrumentation for monitoring thermal and electrical performance under outdoor solar conditions. The TiO 2 nanofluid (0.04% w/w) was selected as the filter medium for its c-Si responsive range transparency and near-infrared absorption, enabling spectral separation and dual energy harvesting. Experimental trials conducted at Daman, India (20.41° N, 72.86° E), during April 2025, demonstrated that the nanofluid filter reduced PV surface temperature by 12–15 °C compared to baseline, stabilized electrical efficiency at 7.4–9.4% during midday, and achieved thermal efficiencies of 45–67%, resulting in overall efficiencies exceeding 70% during peak hours. While a marginal reduction in early-hour electrical output was observed, this was offset by significant thermal energy gains. The results confirm the suitability of TiO 2 nanofluids as spectral filters and establish the developed rig as a reliable platform for long-term experimental studies on BSPVT systems. The developed experimental platform provides a scalable and flexible foundation for long-term outdoor studies, enabling future investigations on alternative nanofluids, flow rates, filter path lengths, and year-round performance assessment of BSPVT systems.