During the energy price spike in the summer of 2008, wind power looked poised to change the world; capacity expansion set records and and billionaire T. Boone Pickens proposed wind as the key to independence from imported oil. Less than a year later, wind installations are falling off and the "Pickens Plan" has stalled.
But I wouldn't start betting against the wind industry yet. Steady technological progress means that turbines can produce more efficiently at more locations than ever. The map below shows how average wind speeds in otherwise-unimpressive Indiana increase for higher turbine mountings--50 meter hub heights were typical in the 1990s, 70 meters after the year 2000, but 100 meters will be common next year. At that height, the entire northern half of the state becomes economical.
And more advanced turbines ensure the economics; recently-introduced designs for lower-speed onshore wind regimes include the Vestas V100 (1.8MW), Acciona AW-116/3000 (3MW), and the Siemens SWT-2.3-101 (2.3MW). These turbines are scaled-up versions of proven generators with blade diameters of one hundred meters or more. The wind industry is likely to see similar conditions to natural gas--an essentially limitless resource constrained primarily by economics. Like horizontal drilling in shale gas formations, the new "superturbines" will be able to generate power across vast swathes of the country, but they will only be built when electricity prices rise above a certain floor.
Federal incentives and emerging carbon restrictions will likely push the wind industry back to record levels in the next year or two. We will probably be surprised how easily wind meets one ambitious 20%-by-2030 goal.