Vertical axis windmills like the Savonius design have been around since about the 9th century and can be traced back to early Persia. These early designs prevailed for a long time. The horizontal axis or propeller-style versions were designed much later as an alternative way to harness the power of the wind and were used primarily for grinding grain or pumping water.

The History

Around 1922 Sigurd J. Savonius, a Finnish engineer, introduced a revolutionary design in vertical axis wind turbines (VAWT) that was both reliable and simple to build. It was initially deployed for installations that required dependability while generating small amounts of power. Currently, this is still the design of choice for most modern anemometers as well as some deep-sea buoys that require low maintenance power.

Why It Is Quiet

One of the main advantages of the Savonius design is that it is quiet and therefore suitable for suburban communities. There are no large noisy blades with which to annoy neighbors or local zoning commissions. Another advantage is that its compact blades seem to pose much less of a danger to passing birds over its horizontal axis cousin.

Why It Is So Efficient In Low Wind Conditions

Since the blades are mounted vertically, there is no need to rotate the windmill to catch the wind. Standard horizontal designs have to be mounted on a pivot that allows them to rotate freely and track the changing wind. Usually little or no electricity is generated while the blades are re-orienting into the wind. In contrast, the more efficient vertical orientation can always be collecting a passing breeze that the horizontal style might miss.

Why It Is Inexpensive And Easier To Operate

Another bonus of the low wind capability of the Savonius windmill is that the vertical shaft allows the generator to be placed nearer to the ground, which means there is less weight at the top of the tower. Because of this, there is less need to stabilize the tower since it is supporting a lighter load.

Having a smaller tower can save money when compared to a standard installation because the tower is lighter and needs less hardware to secure it. By lowering the cost, it can pay for itself more quickly and contribute to lowering your energy bills faster.

The Bottom Line

This type of Vertical Windmill design is efficient because its blades are always in a good position for extracting energy from even a light wind. It requires a lower and therefore less expensive tower than its horizontal cousin. Maintenance can be simpler because its vertical spinning shaft permits the motor/generator to be located at ground level for easy access.