Experimental investigation on the Magnetically controlled performance of Fe3O4@SiO2 nanofluids in a PV/T spectrum splitting system

This study explores the effect of an external magnetic field on the performance of a PV/T spectral splitting system employing Fe₃O₄@SiO₂ nanofluid. The distribution characteristics of magnetic nanoparticles were manipulated to modify their optical properties and thermal conductivity. As a result, the photothermal and photovoltaic conversion efficiencies, along with the merit function (MF value) of the PV/T system, were enhanced. First, the experiment tested different magnetic pole orientations. Results demonstrated that the solar energy utilization rate was highest under the S-S pole orientation. Second, the influence of the magnetic field height ratio on system performance was investigated. The results indicated that changes in the height ratio altered the direction of the magnetic force on nanoparticles. The system achieved optimal performance at a height ratio of 0.5, with thermal and electrical efficiencies of 73.5% and 11.9%, respectively. Third, the study of different magnetic field width ratios revealed that at a width ratio of 1.5, the system’s thermal efficiency reached 75.2%, and the electrical efficiency was 12.0%, with the highest MF of 2.12, significantly outperforming the system under no magnetic field. Magnetic recovery experiments assessed the recyclability of Fe₃O₄@SiO₂ nanofluid. Under a magnetic field strength of 150 mT, a recovery rate of 92.3% was achieved. These findings offer valuable insights for applying magnetic nanofluids in PV/T spectral splitting systems.