CFD-based analysis of chimney performance optimization for the Manzanares pilot plant

Abstract

This research conducts an extensive computational fluid dynamics (CFD) analysis aimed at optimizing the geometric configuration of solar chimney power plants (SCPPs), with particular emphasis on the Manzanares pilot plant. The research analyses the effects of chimney diameter and divergent chimney design on system performance under steady-state conditions at 1000 W/m2 solar irradiance and 300 K ambient temperature. A validated three-dimensional CFD model with a 90° symmetry sector is developed in ANSYS FLUENT. The model is verified through mesh independence and benchmarked against experimental results, showing excellent agreement with measured power output and airflow velocity. The results demonstrate that chimney geometry is a dominant performance-governing factor in large-scale SCPPs. Increasing the chimney diameter up to 2.5 times the reference value enhances the power output by 97%, reaching ~110 kW; further enlargement leads to performance deterioration due to reduced pressure potential at the turbine. More importantly, the adoption of a divergent chimney configuration yields a substantial performance improvement. An optimal chimney exit-to-inlet area ratio of 4 increases the power output to 369.4 kW, corresponding to a 5.6-fold enhancement compared to the reference cylindrical chimney. At this optimal configuration, the maximum air velocity and mass flow rate reach 28.7 m/s and 2137.8 kg/s, respectively. These findings demonstrate that multifold power enhancement can be achieved through aerodynamic optimization of chimney geometry alone, without increasing chimney height, offering a practical, cost-effective, and structurally safer design pathway for future large-scale SCPP installations.