Or better still, provide some kind of variable restriction such that the air flow through the turbine is right at it's max operating power. Furthermore this to

Or better still, provide some kind of variable restriction such that the air flow through the turbine is right at it's max operating power. Furthermore this tower isn't a lossless device, as the wind speed picks up I would guess that it gets "draggier" and less efficient at channeling and accelerating the wind. But even if that's not the case making a variable restriction that could moderate the tunnel wind speed is a very easy problem to solve. Some kind of a damper and a control system that measures wind speed and adjusts the damper accordingly. You might even be able to use the turbine to do the measuring if you're clever.