However, this age-old method of harnessing the wind is only a shadow what what has come since. The western windmill that dotted the plains and prairies in the latter half of the 19th century was widely used to pump water for settlers, ranchers, and cattle. Early in the 20th century, "wind-jammers" brought electric light to those farmers who could afford this luxury before rural electrification.
The late 20th century saw the emergence of the now familiar three-bladed air foil wind turbine. This very effective design has been the defacto standard for the majority of wind-powered electrical generation. The practical limitation has been just how tall can you make the supporting tower.
One of my students recently sent me a link to a radical departure from the familiar bladed turbine. Instead of a supporting tower to gain the required altitude required for catching the best wind, this Horizontal Axis Wind Turbine (HAWT) uses impellers integrated into a lighter-than-air bag filled with helium. The advantage of this design is the ability to soar hundreds of feet higher than the towers it replaces without the engineering requirements to erect a tall structure. You can view this design at http://www.magenn.com/.
Not satisfied with one design, our intrepid student submitted two more. The second design incorporates whatever roof peak line that might exist facing the prevailing winds. Inside a cowling is a horizontally oriented turbine whose blades are roughly the same length as the roofline. You can view this concept at http://cleantechnica.com/2009/10/23/the-new-nimby-defeating-wind-turbine/.
The last design is for a sea-going configuration of multiple turbines. The purpose of these turbines is not for delivering electricity to businesses and residences. These turbines are in place to produce hydrogen gas at a large scale for transport and delivery to those subscribers who need this clean-burning fuel to operate fuel cells, thus providing residential and business electricity. This concept can be viewed at http://www.windhunter.org/.