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 %.
Highlights
In the last few decades, global population and global consumption of energy have increased significantly
Solar radiation passes through the transparent solar collector and reaches the ground, which works as an absorber
Part of the heat is stored in the deeper layers of the ground, and part is released to the air under the solar collector
Summary
In the last few decades, global population and global consumption of energy have increased significantly. The authors used the collector diameter and the tower height and diameter as design parameters and prescribed values of solar radiation to maximize the power output and minimize the capital cost of components [28] and minimize the expenditure and maximize total efficiency and power output [29], using a global analysis. To extract the maximum output from the wind, [35]performed an optimization analysis of small scale wind turbine blades for a solar chimney power plant, under various wind velocity ranges. Most works from literature use yearly averaged values of temperature, solar radiation, and heat fluxes to obtain the optimum dimensions that maximize the efficiency or power output and/or minimize the total cost. What makes our work original is that the optimization was performed for one year, with a time step of one hour
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