Design and experimental study of a Fresnel lens-based concentrated photovoltaic thermal system integrated with nanofluid spectral splitter

Abstract

Minimizing optical losses during light focusing and preparing an appropriate nanofluid for spectral splitting is crucial for the performance of a concentrated photovoltaic thermal system. A Fresnel lens-based solar concentrator integrated with a nanofluid spectral splitting photovoltaic thermal system was designed and validated in this study. The design posited solar irradiation being appropriately concentrated by a linear Fresnel lens on a series of tubes through which the nanofluid flowed, allowing a large beam of limited spectra to be transmitted to the PV below, with the rest absorbed and converted to thermal energy is introduced. The optical loss was minimized by increasing the surface area and decreasing the optical path length. The synthesized nanofluid's spectral transmittance was measured experimentally. Dynamic modeling energy balance equation for the concentrated solar energy conversion system was developed and computed by MATLAB programming. Since the photovoltaic module was decoupled from the filtering channel and integrated with the water cooling, its surface temperature was much lower than the nanofluid and output water temperature. The combined efficiency of the system was 50.35%, 65.2%, 72.70%, 74.7%, and 85% for ZnO nanofluids with volume concentration ratios of 0.00036%, 0.00089%, 0.0017%, 0.0036%, and 0.0089%, respectively. A nanofluid with a concentration ratio of 0.00089 vol% provides the closest spectral match with a silicon solar cell, as verified by a reasonable electrical and thermal efficiency. We used this as a representative concentration ratio of ZnO nanoparticles to validate the prototype. The maximum deviation between simulated and experimentally determined overall performance was less than 3.7% which shows the two results are in good agreement. The findings highlight the potentials of employing a low-cost ZnO nanofluid in a concentrated photovoltaic thermal system for full spectrum utilization.