Kevin Bullis, reporting for Technology Review:
The blades of this type of wind turbine are arranged vertically—like poles on a carousel rather than spokes on a wheel, as with conventional wind turbines. Wind moving around the vertical-axis turbines speeds up, and the vertical arrangement of the blades on downstream wind turbines allows them to effectively catch that wind, speed up, and generate more power. (The spinning blades of a conventional wind turbine would only catch some of this faster wind as they pass through it—this actually hurts the turbine’s performance because it increases stress on the blades.) The arrangement makes it possible to pack more turbines onto a piece of land.