OPTIMIZATION OF A SMALL SOLAR CHIMNEY

Abstract

An optimization study to maximize the exergy efficiency of a small-scale solar chimney was carried out. Optimization variables include collector diameter (Dc), collector height (Hc), tower height (Ht), and tower diameter (Dt). Models from the literature were used to predict environmental and airflow parameters. Exergy efficiency and solar chimney efficiency were determined, on an hourly basis, for a one-year period. The model was simulated using the EES software. Two methods of optimization were used, the method of conjugate directions and the method of variable metric, both providing similar results. Results were compared to the results from an experimental prototype, and it was found that the energetic and exergetic efficiency were significantly improved. The analysis indicated that the height and diameter of the chimney and collector are the most important physical variables in the design of a solar chimney. For both methods, it was found that the maximum exergy efficiency was obtained with a collector height of 0.5 m, a collector diameter of 30 m, a tower diameter of 1 m, and a tower height of 17.8 – 18.8 m. The exergy efficiency was 44 %.

Keywords

• solar chimney, optimization, conjugate directions, variable metric