Thermal and technical analyses of solar chimneys

Institut für Energiewirtschaft und Rationelle Energieanwendungen, Universität Stuttgart, Heßbrühlstraße 49a, D-70565 Stuttgart, Germany; Schlaich Bergermann und Partner, Hohenzollernstr. 1, D-70178 Stuttgart, Germany
Solar Energy (Impact Factor: 3.54). 01/2003; DOI: 10.1016/j.solener.2003.09.012

ABSTRACT An analysis for the solar chimneys has been developed, aimed particularly at a comprehensive analytical and numerical model, which describes the performance of solar chimneys. This model was developed to estimate power output of solar chimneys as well as to examine the effect of various ambient conditions and structural dimensions on the power output. Results from the mathematical model were compared with experimental results and the model was further used to predict the performance characteristics of large-scale commercial solar chimneys. The results show that the height of chimney, the factor of pressure drop at the turbine, the diameter and the optical properties of the collector are important parameters for the design of solar chimneys.

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    ABSTRACT: The radiation network method has been applied to calculate the net radiation heat transfer between two concentric hemispheres separated by two hemispherical radiation shields with temperature-dependent surface emissivities. Three different materials are chosen for radiation shields: aluminum oxide, silicon carbide, and tungsten. The reduction in heat transfer with shields depends not only on the surface characteristics of the two shields, but also on the locations of the shields. Three illustrative examples are presented to illustrate the effects of temperature dependent emissivities and shield locations on the percentage heat transfer reduction. The analysis can be used to study other cases as warranted.
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    ABSTRACT: High solar radiation and ambient temperature, and large desert in Egypt are excellent conditions to install efficiently solar chimney power plants there. Therefore this research aimed to develop a validated mathematical model and governing equations of solar chimney. It is proposed to improve the performance of solar chimney under effects of various parameters, and study of possibility of installing solar chimney in Egypt. The mathematical simulation of the solar chimney has been developed including all its performance parameters, dimensions (of collector, chimney and turbine) and the metrological data; which were considered as inputs of the simulation program. A comparison between the mathematical and experimental performance has been investigated to validate the mathematical simulation. The mathematical model has been used to predict the performance of the solar chimney power plant over a year in Egypt. It is used to study of effects of geometrical parameters, and investigate possibility of the optimum geometrical dimensions. It is obtained that there is in fact no optimum physical size for such plants without considering the economical constraints. The chimney height has a significant effect in the chimney performance. Visualizing of annual performance of the solar chimney would seem to be essentially a power generator in Egypt if it installed in a large scale.