*Translated by Elisa on 5/19/08 - 版權所有*
Solar chimney is a thermal power generation system. Hot air for the solar chimney is produced by absorbing solar irradiance through a translucent collector, and accelerates upwards by the buoyancy force and the stack effect, generating electricity through a wind turbine in the base of the chimney.
Currently, the existing large-scale solar chimney power plants only have an energy conversion efficiency of 1% at their highest at the scale of 1km chimney height, and require an enormous absorber plate to generate the capacity required to meet the energy demand. However, due to the simple system structure and cheap operating cost, its electricity generation cost per kilowatt hour is still lower than that of other solar power generation systems.
The purpose of this study is to discuss the impact of solar chimney geometric shapes to energy conversion efficiency. This includes relevant parameters such as changes of flow areas with changes of chimney heights, sealants of the collectors and proportions of radius. Although the difference in height is the major cause of chimney (stack) effect, the height of chimney directly impacts the cost of power generation. Thus, enhancing power generation efficiency within a limited height will increase the conversion efficiency to kinetic energy of the fluid. This is the focal point of this research.
Through a divergent nozzle, we can change the distribution of pressure inside a chimney, generate a faster fluid speed at the nozzle throat, lower the average temperature of the fluid at the outlet and obtain the highest flow rate along with the increase of mass flow. This will help the operation of wind turbine. The reduced-scale model experiment proves that the (energy) conversion efficiency of a divergent nozzle is four to five times that of a vertical pipe and will reach above 1% efficiency under the simulation of a scale of 100m chimney height.
** Partial document posted. The rest of the document is password protected to protect the person who asked me to translate her thesis**