Savonius Wind Turbine

A Savonius wind turbine is a vertical-axis wind turbine, developed by Finnish engineer Sigurd Johannes Savonius, who built the design in 1922 and patented it in 1926, that turns wind force into rotational torque using two or three curved scoops mounted on a vertical shaft; seen from above, a two-scoop Savonius rotor resembles the letter S. Earlier Europeans had experimented with curved vertical blades for centuries, including engineer Fausto Veranzio, who described such a design in his 1616 book Machinae Novae, but Savonius carried the idea to a working, patentable design, filing two United States patents, in 1925 and 1928. As a drag-type turbine, a Savonius rotor extracts substantially less power from the wind than a similarly sized lift-type turbine such as a horizontal-axis machine, but it runs quietly, keeps working in low wind, and needs no mechanism to turn and face the wind, since it responds to wind from any direction equally.