Savonius wind turbine
Savonius wind turbines are a type of vertical-axis wind turbine (VAWT), used for converting the force of the wind into torque on a rotating shaft.[disambiguation needed 
] The turbine consists of a number of aerofoils, usually—but not always—vertically mounted on a rotating shaft or framework, either ground stationed or tethered in airborne systems.
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[edit] Origin
The Savonius wind turbine was invented by the Finnish engineer Sigurd Johannes Savonius in 1922. However, Europeans had been experimenting with curved blades on VAWT type wind turbines for many decades before this. In 1551 in Sebenico, Italy-born Bishop of Czanad, who was as well an engineer, wrote 1616 the book Machinae novae, containing several VAWT-type wind turbines with curved or V-shaped pallets. None of his or any other earlier examples arrived the state of development made by Sigurd Savonius. In his Finnish biography, there is mention of his intention to develop a turbine-type similar to the Flettner-type, but autorotationary. He - so tells the biography - experienced his rotor on small rowing vessels on lakes in his country before he died on lung infection in early age of 46. There are no results of his particular investigation known, but Magnus-Effect is confirmed by König.[1]
[edit] Operation
The Savonius turbine is one of the simplest turbines. Aerodynamically, it is a drag-type device, consisting of two or three scoops. Looking down on the rotor from above, a two-scoop machine would look like an "S" shape in cross section. Because of the curvature, the scoops experience less drag when moving against the wind than when moving with the wind. The differential drag causes the Savonius turbine to spin. Because they are drag-type devices, Savonius turbines extract much less of the wind's power than other similarly-sized lift-type turbines. Much of the swept area of a Savonius rotor may be near the ground, if it has a small mount without an extended post, making the overall energy extraction less effective due to the lower wind speeds found at lower heights.
[edit] Use
Savonius turbines are used whenever cost or reliability is much more important than efficiency.
Most anemometers are Savonius turbines for this reason, as efficiency is irrelevant to the application of measuring wind speed. Much larger Savonius turbines have been used to generate electric power on deep-water buoys, which need small amounts of power and get very little maintenance. Design is simplified because, unlike with horizontal axis wind turbines (HAWTs), no pointing mechanism is required to allow for shifting wind direction and the turbine is self-starting. Savonius and other vertical-axis machines are good at pumping water and other high torque, low rpm applications and are not usually connected to electric power grids. They can sometimes have long helical scoops, to give smooth torque.
The most ubiquitous application of the Savonius wind turbine is the Flettner Ventilator, which is commonly seen on the roofs of vans and buses and is used as a cooling device. The ventilator was developed by the German aircraft engineer Anton Flettner in the 1920s. It uses the Savonius wind turbine to drive an extractor fan. The vents are still manufactured in the UK by Flettner Ventilator Limited.[2]
Small Savonius wind turbines are sometimes seen used as advertising signs where the rotation helps to draw attention to the item advertised. They sometimes feature a simple two-frame animation.
[edit] Tethered airborne Savonius turbines
- Airborne wind turbines
- Kite types
- When the Savonius rotor axis is set horizontally and tethered, then kiting results. There are scores of patents and products that use the net lift Magnus-effect that occurs in the autorotation of the Savonius rotor. The spin may be mined for some of its energy for making noise, heat, or electricity.
[edit] Gallery
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Operation of a Savonius turbine
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A Savonius rotor bladed WECS
[edit] References
[edit] External links
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Wikimedia Commons has media related to: Savonius wind turbines |
- Build your own model Savonius wind turbine
- Windside Savonius Type Wind Turbines for use in Extreme Environments
- Forgen low power Savonius Type Wind Turbines for Marine Applications
- HelixWind Savonius Type Wind Turbine
- Savonius turbines for dynamic environments www.spinpower.org
- How to build a Savonius wind generator
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