Savonius Wind Turbines

What is a savonius wind turbine - savonius (VAWT)

A Savonius is a type of vertical axis wind turbine (1) (VAWT) generator. The Savonius is a drag-type VAWT which operates in the same way as a cup anemometer (2) (pictured below). Savonius wind turbines typically only have an efficiency of around 15% - i.e. just 15% of the wind energy hitting the rotor is turned into rotational mechanical energy. This is much less than can be achieved with a Darrieus wind turbine (3) which uses lift rather than drag.

Cup anemometer is like a savonius drag type VAWT

The speed of the cups of a cup anemometer (and a Savonius wind turbine) cannot rotate faster than the speed of the wind and so they have a tip speed ratio (TSR) of 1 or below. Therefore Savonius type vertical axis wind turbines turn slowly but generate a high torque.

This does not make them very suitable for electricity generation since turbine generators (4) need to be turned at hundreds of RPM to generate high voltages and currents. A gearbox could be employed but the added resistence would leave the Savonius requiring a very strong wind to get spinning - i.e. it typically would not self-start.

Savonius wind turbines can and are used in electricity generation - for example see our article on the Envirotek V20 VAWT (5) generator - with the benefit that they continue to generate electricity in the strongest winds without being damaged, they are very quiet, and they are relatively easy to make. Savonius turbines do not scale well to kW sizes, however they are useful for small scale domestic electricity generation - especially in locations with strong turbulent winds. Click here to view our free VAWT wind turbine plans (6) to find out how to make your own Savonius wind turbine generator.

Savonius wind turbines are ideally suited to applications such as pumping water and grinding grain for which slow rotation and high torque are essential. Because of the torque yield of a Savonius wind turbine, the bearings used must be very sturdy and may require servicing every couple of years.

Make a Savonius Wind Turbine

NEW - Click here to view our new article Build a Savonius Wind Turbine (7). Find out how to put together a small (<100W) Savonius wind turbine using cheap and easy to find items and a few tools.

Web Link References

(1) http://www.reuk.co.uk/VAWT-Vertical-Axis-Wind-Turbine.htm
(2) http://www.reuk.co.uk/Anemometer.htm
(3) http://www.reuk.co.uk/Darrieus-Wind-Turbines.htm
(4) http://www.reuk.co.uk/Permanent-Magnet-Generator.htm
(5) http://www.reuk.co.uk/Envirotek-V20-VAWT-Generator.htm
(6) http://www.reuk.co.uk/Free-VAWT-Wind-Turbine-Plans.htm
(7) http://www.reuk.co.uk/Build-a-Savonius-Wind-Turbine.htm