Energy coupling mechanism of spectral-splitting PV/T systems under multi-environmental conditions

Existing studies on nanofluid-based spectral-splitting photovoltaic/thermal systems seldom address multi-parameter coupling under realistic environmental conditions. To fill this gap, this work develops an integrated framework combining high-fidelity 3D computational fluid dynamics using a non-gray discrete ordinates radiation model, an L16(45) orthogonal design, and semi-empirical modeling. The goal is to clarify energy-coupling mechanisms and quantify system sensitivity to ambient temperature, wind speed, inlet velocity, irradiance, and incidence angle. Range analysis shows that ambient temperature is the dominant factor, with ranges of 4.30 °C for fluid temperature difference and 12.82 °C for photovoltaic temperature, followed by irradiance. Across 16 operating conditions, the inlet–outlet temperature difference varied from 0 °C to 10.5 °C, and photovoltaic temperature fluctuated by up to 15.4 °C. Simulations reveal that flow control can suppress hot spots caused by low velocity and high irradiance. Spectral analysis confirms strong thermal–electrical decoupling: the nanofluid absorbs 60 % and 71 % in bands 0 (300–700 nm) and 2 (1100–2800 nm) while transmitting 80 % in band 1 (700–1100 nm). The developed nonlinear regression models achieve R2 values of 0.94 (thermal) and 0.93 (electrical), offering guidance for photovoltaic/thermal optimization under real-world conditions.