How Can I Increase Wind Speed and Thus Maximize the Power Output of My Turbine?  You Can’t

I often come across claims that wind shrouds serve to concentrate the wind’s power; I’ve seen dozens of variations on this theme over the years.  The bitter truth is that this doesn’t work, for reasons explained in the article linked above, of which this is an excerpt:

“Augmenters” attempt to leverage the cubic function of wind speed in the energy equation by speeding up the wind into the rotor through ducts or shrouds. This method is akin to the nozzle on a hose that effectively turns a fat, trickle of water into a forceful, faster stream. The difference with wind is that it is not confined to a hose, so it does not have to pass through the nozzle. And in fact, because the wind turbine at the end of the “nozzle” is trying to slow the wind (remember, that is its job), the wind simply sees the augmented turbine as an obstruction and passes around it rather than going through it—taking the path of least resistance.  Although a duct does serve to increase the capture area of a wind turbine, a more effective way to accomplish that goal is with longer blades.

Here is some real-world testing on this, showing that the shroud does increase the power output in a linear fashion, according to the increase in “capture” or “swept” area.