Integrated design of a bio-inspired photovoltaic/thermal system with green nanofluids and composite phase change materials for semi-arid climates

Abstract

Photovoltaic/thermal (PV/T) systems urgently require solutions that simultaneously address efficiency limitations and environmental concerns. This study introduces three key innovations to address these limitations: (1) bio-inspired absorber tubes modeled after the black scorpion’s tail geometry (a previously unexplored biomimetic approach for PV/T systems), (2) Clove-functionalized MWCNT/H₂O nanofluids—a new eco-friendly coolant class that simultaneously enhances heat transfer and reduces nanoparticle toxicity, and (3) Composite phase change materials (CPCMs) for surface cooling and electrical efficiency enhancement, with annual carbon dioxide emission (CO₂) reduction analysis. These innovations synergistically improve performance while addressing environmental concerns—an aspect underexplored in previous PV/T research. Numerical simulations were conducted using Ansys-Fluent 2021 under transient heat flux conditions (11:00 AM to 16:00 PM) representative of a semi-arid climate (summer in Tehran- Iran), with experimental validation to ensure accuracy. The results demonstrate that the optimized helical turbulator design (Model 3) reduces average PV surface temperature by 10.2 % (to ∼43.36 °C) and increases average fluid outlet temperature by 3.85 % (to ∼32.81 °C) compared to baseline geometries. Furthermore, the use of green nanofluids at varying concentrations increases thermal and electrical efficiencies by up to 15.38 % and 1.43 %, respectively. Green nanofluids enhance thermal conductivity by ∼12.22 %, achieving a peak thermal efficiency of 75.2 % (+15.38 % improvement) and electrical efficiency of 15.23 % (+0.83 % improvement). CPCM thickness optimization (1.2 cm) further reduces PV temperature by 3.33 % while improving electrical efficiency by 1.01 %. From an environmental perspective, the system achieves substantial CO₂ reductions, with Model 3 and the inclusion of C-MWCNTs/H₂O: 0.175 wt% nanofluid leading to a 32.29-ton decrease (+ 143.7 % improvement) over a 15-year period.