Experimental and Numerical Analysis of Thermal-Electrical Performance and Cell Temperature Distribution in a Novel Multi-Fluid Coupled Flow-Regulated PVT System.

Photovoltaic-thermal (PVT) systems, which harness the full solar spectrum, are attracting substantial research attention. By integration of electrical power generation with thermal energy extraction, these systems enhance overall energy efficiency. However, existing studies often focus on individual parameters, lacking a comprehensive investigation of the combined effects of nanofluids, channel geometries, and coolant volumetric flow rates. This study presents a novel PVT system tailored for high-rise residential applications featuring a lightweight aluminum alloy structure and a parallel full-channel collector configuration. Thermoelectric performance and photovoltaic (PV) cell temperature distribution were analyzed experimentally and via CFD-FLUENT simulations using water, a 40% ethylene glycol solution, and a 3% Al2O3-water nanofluid across volumetric flow rates ranging from 0.02 to 0.20 L/s. Experimental results demonstrate that increasing the volumetric flow rate significantly improves the convective heat transfer effectiveness. The 3% Al2O3-water nanofluid exhibits superior thermal conductivity, achieving a combined thermoelectric efficiency of 76.97% at 0.20 L/s, followed by water (74.09%), while the 40% ethylene glycol solution yields the lowest efficiency (70.62%). Simulation results indicate that the collector's flow channel geometry constitutes the intrinsic physical mechanism governing PV cell temperature field uniformity, whereas the volumetric flow rate serves as the key external parameter modulating this mechanism's efficacy. Higher flow rates enhance cell cooling and improve temperature uniformity across the PV module, albeit at the expense of reduced coolant exergy. A significant synergistic effect exists between coolant type and flow rate: under high volumetric flow conditions, the 3% Al2O3-water nanofluid, leveraging intensified turbulence and high thermal conductivity, achieves both the lowest cell temperature and minimal standard deviation in cell temperature. However, its application is limited in subzero environments due to its freezing point (-1 to -2 °C). Although the 40% ethylene glycol solution delivers lower thermoelectric overall efficiency, it offers broader operational temperature tolerance. This work establishes a theoretical foundation for coolant selection and operational optimization of PVT systems, providing valuable insights for advancing renewable energy utilization.