Coupled optical-thermal optimization of concentrated photovoltaic/thermal modules using advanced nanofluids and phase change materials

Efficient solar spectrum splitting and dynamic thermal management remain critical bottlenecks in advancing concentrated photovoltaic-thermal (CPV/T) technologies. To address this, the present study introduces a novel hybrid CPV/T architecture that synergistically couples a nanoparticle-based liquid spectral filter with a phase change material (PCM) heat sink, actively regulated by an embedded fluid-circulating spiral coil. A comprehensive 3D multiphysics framework was developed to evaluate the complex thermoelectric and optical interactions across varying nanoparticle concentrations (40 to 200 ppm) of TiO₂ and ZnO. The analysis exposes a fundamental optical thermodynamic trade-off. ZnO nanofluids exhibit exceptional thermal regulation and spectral filtering, achieving a peak thermal efficiency of 50.5 % and a total primary efficiency of 23.5 % by minimizing secondary coolant thermal loads (19 W). However, their high photon absorption inherently penalizes direct electrical generation. In contrast, TiO₂ suspensions prioritize photon transmission, maximizing instantaneous electrical output and overall exergy efficiency (5.6 %). When evaluating base fluids, the PSF/TiO₂ combination emerges as the superior medium, yielding the highest primary power output (48.5 W) and an optimal merit function of 2.25 through enhanced thermal recovery. While water/TiO₂ provides a robust thermoelectrical balance (40 W electrical output), Dowtherm A severely underperforms (33 W, merit function 1.55). Furthermore, geometrical optimization of the active cooling loop proves that a longitudinal finned coil maximizes overarching system performance, delivering 97.0 W of total power with a merit function of 2.2. Although annular finned coils achieve the lowest operating cell temperature (330.5 K), their associated optical shading losses (5.2 %) drastically degrade the net electrical yield to 25.1 W. Ultimately, this study provides a definitive, multi-objective design matrix for engineering next-generation CPV/T systems governed by hybrid active–passive thermal control.