Savonius wind turbine

Savonius wind turbines are a special kind of wind turbine that turns wind into useful energy. They are called vertical-axis wind turbines because their spinning parts move up and down, not side to side like some other turbines. These turbines have special shapes, called aerofoils, that catch the wind and create a spinning motion.

The spinning parts, or shaft, can be fixed to the ground or held up in the air with special systems. This makes Savonius turbines useful in many places where we need clean energy from the wind. They are strong and can work well even when the wind does not blow very fast.

Origin

The Savonius wind turbine was made by a Finnish engineer named Sigurd Johannes Savonius in 1922. He got a patent for it in 1926. People in Europe had tried using curved blades on tall wind turbines for many years before that. The first written record of this idea was by an engineer named Fausto Veranzio in 1616. He described several tall wind turbines with curved blades in his book. Savonius was the first to fully develop this type of turbine. He tested his design on small boats on lakes in Finland. He also applied for two patents for this turbine design in the United States, one in 1925 and another in 1928.

Operation

The Savonius turbine is one of the simplest types of turbines. It is made of two or three scoops. If you look at the rotor from above, a two-scoop machine looks like the letter "S". The scoops spin because they feel less force when moving against the wind than when moving with the wind. Because they are drag-type devices, Savonius turbines do not get as much power from the wind as other turbines. They have some good points, like making little noise, working well in low wind speeds, and not needing to face a special wind direction.

Power and rotational speed

According to Betz's law, we can only get part of the power from the wind. In real life, we get about half of what is possible.

For a Savonius wind turbine, we can get about 20% of the most possible power.

The speed the rotor turns depends on the wind and the size of the rotor. For example, a Savonius rotor about the size of an oil barrel in a wind of 10 meters per second can make about 120 watts of power and turn about 190 times every minute.

Use

Savonius turbines are used when cost or reliability is more important than efficiency. Many anemometers, which measure wind speed, are Savonius turbines because efficiency does not matter for this job. Larger Savonius turbines have been used to make electric power on deep-water buoys. These buoys need only small amounts of power and do not get much maintenance. Their design is simpler than other turbines because they do not need a special part to face the wind, and they can start turning on their own.

One common use of Savonius turbines is the Flettner ventilator, seen on roofs of vans and buses. It was made in the 1920s by German engineer Anton Flettner to help cool vehicles by moving air. These vents are still made in the UK today. Savonius turbines have also helped power science stations in Antarctica. In Europe, small Savonius turbines are sometimes used in signs that spin to catch people’s attention.

Tethered airborne Savonius turbines

• Airborne wind turbines
• Kite types

When the Savonius rotor axis is set horizontally and tethered, it can move the air around it. Many patents and products use the lift that happens when the Savonius rotor spins. This spin can be used to create sound, heat, or electricity.