It's plausible that such a design could double or triple a turbine's power output, says Paul Sclavounos, a professor of mechanical engineering http://en.wikipedia.org/wiki/Mechanical_engineering at MIT. Part of the increase comes simply from guiding the air to the turbine with the shroud. But Sclavounos notes that it also helps to use the wind surrounding the turbine to speed up the airflow, because the power produced by a wind turbine increases with the cube of the wind speed. The key question is whether the new turbines can be built and maintained at a low-enough cost. A shrouded turbines can be half to a third the size of a conventional 30+ story tall 3 blade turbine for the same power output and with tall towers and blades up to 90 meters long transportation alone can make up to 20% of turbine construction costs so a shrouded turbine may lead to significant reduction in construction costs and as a result cheaper power generation.

It is still early days for the FloDesign turbines as they have only built a small prototype http://en.wikipedia.org/wiki/Prototype for wind-tunnel tests. Its next step is to build a 12-foot diameter, 10-kilowatt system for field tests. The prototype is expected to be finished by the end of next year or early in 2010, with commercial wind turbines to follow. Eventually the company plans to make turbines as large as one megawatt, but is not yet taking orders.

http://www.gizmag.com/flodesign-high-efficiency-wind-turbine-based-on-jet-engine-technology/10556/