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

## TL;DR

This study improves solar energy systems by using ZnO nanofluids with varying concentrations to better split and convert the full spectrum of sunlight into electricity and heat.

## Contribution

The paper introduces a dynamic nanofluid concentration control mechanism for enhanced adaptability and full-spectrum utilization in solar systems.

## Key findings

- Higher nanofluid concentrations improve thermal efficiency but reduce photovoltaic efficiency.
- A peak comprehensive efficiency of 50.63% was achieved at 280 ppm ZnO concentration.
- At 420 ppm, thermal efficiency peaks as visible light transmittance approaches zero.

## Abstract

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.