Numerical Investigation of Collector Area Ratio Effects on Buoyancy-driven Flow and Pressure Development in a Solar Chimney Power Plant

Abstract

Solar chimney power plants (SCPPs) convert buoyancy-driven airflow into renewable electricity, and their performance strongly depends on geometric design parameters. While chimney height and collector diameter have been extensively investigated, the influence of the collector outlet-to-inlet area ratio (OIAR) remains insufficiently addressed despite its important role in airflow acceleration, heat retention, and pressure generation. A three-dimensional computational fluid dynamics (CFD) analysis of OIAR effects on the thermo-fluid behavior and power performance of a scaled SCPP model is conducted. The incompressible turbulent flow equations were solved in ANSYS Fluent using the Boussinesq approximation for buoyancy, the standard k–ε turbulence model, and the Discrete Ordinates (DO) radiation model. Turbine rotation was represented through a multiple reference frame approach, and the numerical model was validated against experimental data with good agreement in velocity and temperature distributions. Four OIAR configurations (0.5, 1.0, 1.5, and 2.0) were investigated. Results show that OIAR significantly affects pressure distribution, airflow structure, and thermal stratification. At OIAR = 0.5, the collector outlet temperature increased by 18 K, the chimney inlet pressure reached −260 Pa, and the turbine power output attained 428.7 W. In contrast, OIAR = 2.0 produced only a 5.3 K temperature rise and reduced the power output to 134.6 W. The study identifies OIAR = 0.5 as the optimal configuration and highlights OIAR as a key parameter for improving large-scale SCPP performance. By emphasizing the governing influence of collector geometry, this research contributes to improving the understanding and future development of high-performance large-scale solar chimney technologies.