The paper presents a mathematical thermal model for steady state airflow inside a solar chimney power plant using modified Bernoulli equation with buoyancy effect and ideal gas equation. The study evaluates the use of constant density assumption across the solar chimney and compares it with more realistic chimney mathematical discrete model that allows density variation across the chimney. The result shows that using a constant density assumption through the solar chimney can simplify the analytical model however it over predicts the power generation. The results show that the chimney height, the collector radius, the solar irradiance, and the turbine head are essential parameters for the design of solar chimneys. The maximum power generation depends on the turbine head and the relation is not monotonic. (C) 2012 Elsevier Ltd. All rights reserved.