Hydrogen generating station (HGS) by water electrolysis is based on three principal compartments: hydraulic pumping system, water electrolysis process and energy supply whose can be free source like solar chimney power plans (SCPP). The HGS can be controlled if governed one of these three compartments especially the energy supply SCPP. The aim of this study is to investigate numerically the airflow behavior through a Solar Chimney. The transport equations that describe the flow, for different geometric tower parameters were modeled and solved numerically using the finite volume method. This methodology allows us a detailed visualization of the effects of some geometrical parameters such as the tower height and tower radius. It has been shown in this work that the dimensions of the tower play an important role in designing of such systems by increasing or decreasing the mass flow rate. Consequently, the hydrodynamic field is directly controlled by varying the tower dimensions. However the thermal field is indirectly controlled by decreasing the system mean temperature. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.