Vertical Axis Wind Turbine
Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor shaft is set vertically and the main components are located at the base of the turbine. Among the advantages of this arrangement are that generators and gearboxes can be placed close to the ground, which makes these components easier to service and repair, and that VAWTs do not need to be pointed into the wind. Major drawbacks for the early designs (Savonius, Darrieus and giromill) included the pulsatory torque that can be produced during each revolution and the huge bending moments on the blades. Later designs solved the torque issue by using the helical twist of the blades almost similar to Gorlov's water turbines.
A VAWT tipped sideways, with the axis perpendicular to the wind streamlines, functions similarly. A more general term that includes this option is "transverse axis wind turbine". For example, the original Darrieus patent, includes both options.
Drag-type VAWTs, such as the Savonius rotor, typically operate at lower tipspeed ratios than lift-based VAWTs such as Darrieus rotors and cycloturbines.
A unique, mixed Darrieus - Savonius VAWT type has recently been developed and patented. The main benefits obtained are improved performance at lower wind speeds and a lower r.p.m. regime at higher wind speeds resulting in a silent turbine suitable for residential environments.
Read more about Vertical Axis Wind Turbine: General Aerodynamics, Advantages of Vertical Axis Wind Turbines, Disadvantages of Vertical Axis Wind Turbines
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