And omb (the first post)...
This is why lay people should not (as a rule) second-guess scientists and engineers, who spend their whole lives studying their subjects.
Trust me, a competent design WILL use all of the generated force that it can.
But rather than put "additional" turbines all the way up the stack, where access would be not only difficult but also perhaps dangerous (height AND weight), the increased resistance would be put where it is now: at the bottom. Up the stack is highly unnecessary.
Remember: the tower is sealed to leakage (or it would not work), therefore one can take ALL of the energy one is going to take, at either end of the tube. Generators can be designed to use MOST of the available energy, leaving only enough lift in the tube to move the air fast enough to generate power. This turbine will not be "off the shelf," but will be designed to use every bit of energy available, leaving only enough in the column of air to keep the flow moving at an adequate generation speed. Too slow, and the turbines will stall out.
They have already optimized the turbines and blades, or they wouldn't have achieved 80 % efficiency.
