Resumen
The use of a solar chimney for ventilation has a very significant environmental and economic impact. The aim of this work is to found the optimum ratio between height and base length in trapezoidal prism-shaped solar chimney. The idea is to give more flexibility to the architectural design in buildings and offer the possibility of combination with other passive or active systems. Trapezoidal shape of solar chimney can be interesting not by increasing the efficiency comparing with other shapes like the rectangular. It may be more aesthetically pleasing, easily to be installed and retrofitted on trapezoidal roofs even on existing buildings. For this reason, three differents ratios of height to base length (h/l = 1), (h/l = 1.5) and (h/l = 2) have been experimentally studied. Two correlations to predict solar chimney exit air velocity and efficiency were developed and tested; good agreement with experimental results is proved. Results show that the flow rate increase by increasing (h/l) in a logarithmic tendency. The optimum thermal efficiency is given where h/l = 1.65. An approach using RETScreen4 software was also carried out and showed that 1 m² solar chimney installed in favorable conditions can cover 37 m² of living space in term of ventilation. For a 120 m² house, solar chimney system saves the equivalent of 23.9 liters of gasoline per year.