Improvement in Solar Chimney Power Generation by Using a Diffuser Tower

Abstract

The solar chimney prototype, operated in Spain from 1982 to 1989, verified the concept of the solar chimney. The power generation mechanism in this system is to turn the wind turbine placed inside a high rise cylindrical hollow tower by an induced thermal updraft. As long as the thermal updraft is induced inside the tower by the solar radiation, this system can produce electricity. The disadvantage of this system is the low power generation efficiency compared to other solar energy power generation systems. To overcome this disadvantage, we improved the mechanism in order to augment the velocity of the air which flows into the wind turbine. By applying a diffuser tower instead of a cylindrical one, the efficiency of the systems power generation is increased. The mechanism that we investigated was the effect of the diffuser on the solar chimney structure. The inner diameter of the tower expands as the height increases so that the static pressure recovery effect of the diffuser causes a low static pressure region to form at the bottom of the tower. This effect induces greater airflow within the tower. The laboratory experiment, as does the computational fluid dynamics (CFD) analysis of the laboratory sized model, shows that the proposed diffuser type tower induces a velocity approximately 1.38–1.44 times greater than the conventional cylindrical type. The wind power generation output is proportional to the cube of the incoming wind velocity into the wind turbine; therefore, approximately 2.6–3.0 times greater power output can be expected from using the diffuser type tower.