Passive cooling technology for a building by using solar chimney and earth to air heat exchanger hybrid system

Heating, ventilation and cooling are main parts of the major energy consumption in a building. Passive cooling systems are used as a low energy consuming technology to provide thermal comfort and remove undesirable indoor heat from buildings in hot climate conditions. There are many passive cooling techniques in this field and it is possible to improve these technologies. In this study, solar chimney (SC) and earth to air heat exchanger (EAHE) hybrid system is introduced to provide passive cooling of a typical building in Elazig (Turkey). Numerical analyses are performed for thermal performance of EAHE at 1 m soil depths with two different channel materials as PVC and steel (%0.5 C). Problems have been solved at steady state in three-dimensional model by using different values of the Reynolds number in turbulent flow (Re = 5x103, 104, 15x103, 2x104, 4x104, 6x104, 105). In order to investigate cooling performance of the solar chimney, results have been obtained for various air gaps and inlet velocity. In the solar chimney and earth to air heat exchanger hybrid system, results have been recorded for different solar radiation and ambient temperature, various absorber lengths, chimney inclination angles, channel and openings measurements to determine the effects on system performance. For numerical analysis ANSYS Fluent 12.1 and 14.5 Software program was used. Geometric model has been created with SolidWorks and ANSYS Workbench. Furthermore, Mesh structures of the models have been created in the Workbench package program. Standard k-ε and Reynolds Normalized Group Turbulence (RNG) k-ε have been chosen as turbulent models. In order to validate the numerical results, comparisons were made with experimental, theoretical and numerical studies in the literature and very consistent results were obtained. Consequently, the desired cooling with the use of the combined solar chimney and underground air channel during the daytime has been provided without any need to electricity. Additionally, the hybrid system with an appropriate design provides thermal comfort with large number of hours, especially in hot summer days for occupants. The number of required solar chimney and earth to air heat exchanger may be calculated depending on the desired thermal comfort conditions and cooling capacity. It is expected that these hybrid systems are used extensively to provide thermal comfort, especially in summer and tropic climate regions. Finally, the advantages, limitations and difficulties of these technologies are emphasized and possible future systems are proposed in this field.