Considering the Performance Study of ZnO Nanofluid at Different Concentrations for the Full-Spectrum Utilization System

Single photovoltaic (PV) and photothermal (PT) technologies in solar energy applications are limited to the conversion of visible light and high-quality infrared spectra, respectively; this limitation results in relatively low energy utilization efficiency. In contrast, liquid spectrum-splitting technology enables the separation and conversion of various spectral bands, with the composition of the medium playing a pivotal role in the efficient utilization of the full spectrum. Compared to previous static spectral-splitting systems, this study introduces a dynamic nanofluid concentration control mechanism, which actively balances PV and PT contributions based on real-time solar conditions, achieving higher adaptability and efficiency. This study proposes a concentrated photovoltaic-thermal (CPVT) system based on the variable concentration of spectrum-splitting media, employing a concave-bottom, hollow pipeline structure. By introducing nanofluids with varying concentrations, we measured and analyzed spot uniformity and transmittance, comparing the system's absorption properties for infrared light to its transmittance properties for visible light. A tunable model for photoelectric and photothermal-electric conversion was constructed, enabling the evaluation of differences in thermal and electrical performance. The results indicate that, within the designed spectrum-splitting pipeline, increases in nanofluid concentration correlate with improvements in both temperature and thermal efficiency. However, the photovoltaic efficiency decreased at higher concentrations. When the concentration reached approximately 280 ppm, the system achieved a peak comprehensive efficiency of 50.63%, demonstrating its superiority in adaptability and full-spectrum utilization compared to previous CPVT systems. As the concentration increased to 420 ppm, light transmittance nearly approached zero, resulting in a peak in thermal efficiency. This variability in concentration endows the system with a flexible capacity to modulate both thermal and electrical outputs, offering significant potential for further development.