Numerical analysis of the crosswind in small solar chimney

Abstract

The solar chimney (or solar updraft tower) consists of a circular solar collector, a tower in the center of the collector, and turbines installed in the collector output or the tower entrance. The solar radiation passes through the translucent collector, reaches the ground surface and heats it. The air within the device is heated by the radiation emitted by the ground and by convection currents formed under the collector. The thermal energy is stored in the absorber layer of the ground when there is incidence of solar radiation and it is released from the ground when solar radiation is low. The density difference between the hot air inside the device and the ambient air creates convection currents that drive the air in the collector from the base to the top of the tower. Finally, the airflow in the tower drives the turbines which are coupled to electrical generators. The environmental winds influence the performance of the solar updraft towers in three main ways: heat losses by convection from the outer surface of the collector to the environment, heated air drag out of the cover and drag on the top of the chimney generating a suction effect and enhancing the upward flow in the tower. This work studied the influence of crosswinds on the system flow conditions through a numerical analysis using CFD. Results indicate that an increase on the environmental crosswinds speed from 0 to 25 m/s decreased the outlet temperature of the device in 0.3% and increased the outlet velocity in 50.26%, increasing the energetic efficiency of the device in 56.31%.