The Divergent Solar Chimney - theoretical considerations and possible dimensions for a large-scale prototype
There have been several investigations into whether the shape of the chimney might affect the efficiency of the solar chimney but results have been inconclusive. Two recent papers, however, have shown that a divergent solar chimney (DSC) multiplies efficiency. Koonsrisuk and Chitsomboon using computational fluid dynamics (CFD) and a theoretical model found that efficiency could be multiplied "as much as 400 times". Ohya et al using laboratory model solar chimneys found experimentally enhancement by a factor of 2-3-4. The present paper develops its own theoretical model and finds the efficiency is multiplied by (A1/A2)2 divergent compared to cylindrical, where A1 is the area of the top of the chimney and A2 the area of the base of the chimney. Calculations are presented for a large-scale prototype DSC of height 100m, chimney base diameter 20m and chimney top diameter 100m which give an efficiency of conversion of solar to mechanical energy of 67%.