## The Divergent Solar Chimney - theoretical considerations and possible dimensions for a large-scale prototype

### Summary

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 (A_{1}/A_{2})^{2}
divergent compared to cylindrical, where A_{1} is
the area of the top of the chimney and A_{2} 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%.