The Savonius rotor – a kind of vertical wind turbines. It consists of a mast and two or more blades in the form of hollow half-cylinders offset relative to each other. Rotor invented by the Finnish engineer Sigurd Savonius in 1929. The rotor is constructed on the difference of resistances, which is created in the flow of air flow of the wings of the rotor. The movement of the blades around the Central axis is achieved by the convex – concave shape of the blades. The rotor design is simple, so is strength and durability. With proper manufacturing has a relatively high rotation speed. The construction is made so that regardless of the direction of air flow, the rotor is always oriented to the wind, also he is not afraid of turbulence.
There are several types of designs of savonius rotors:
1. The design consists of a shaft and symmetrically mounted on the two blades in the form of a half-cylinder. The design differs durability and reliability due to the presence of the central shaft, but it is in comparison with the next two designs are less effective. The rotor it is possible to install and fasten only one end.
2. Too simple design. Consists of vanes in the form of half-cylinders, which in the central part is offset so that calling on each other. This technique significantly increases the effectiveness of the design, due to the fact that part of the air flow acts on the second blade during the release of the first.
3. The most effective and most common design of the three. Represents the two blades in the form of half-cylinders, one side, not curved, but straight. This solution allows to equip the design of the aerodynamic profile and thus significantly improve aerodynamic performance. Besides the blades in the central part are shifted toward each other relative to the center. Getting on the blades, the air flow creates a lifting force, and increases the efficiency of the rotor. But this design is labor intensive to manufacture, the blades are made of metal.
Currently wind turbines with a savonius rotor produce power up to 5kW.
The savonius rotor is unfortunately ineffective, it produces only 15% of the energy. But considering the fact that he has a great starting torque, it is often used in tandem with the Darrieus rotor to provide a second high starting torque.
But despite this shortcoming, the rotor has advantages in a simple and very reliable design. The blades are a simple shape and does not require special technology in manufacturing. The rotor has a large starting torque, therefore, does not require initial forced unwinding. Also works at not very high speeds, which affects safety during maintenance. And most importantly, fully independent from air flow direction.
