Wind turbine architecture is at a plateau

Conventional turbines have grown taller, heavier, and more expensive in order to generate more power. These large structures are expensive and complex to construct, and can only be installed economically where the winds routinely reach speeds of between 5-8 meters per second (20-28 kilometers per hour). Unfortunately, less than 15% of all land around the world meets this criteria, meaning this existing technology in its current form cannot scale.

Source: National Renewable Energy Laboratory