Vertical Axis Wind Turbine (VAWT)
- The schematic diagram of a vertical axis wind turbine with Darrieus type two bladed rotor is shown in Figure.
The advantages of vertical axis turbines over horizontal axis turbines are :
- It does not need any yaw control mechanism since vanes of the wind mill can accept the wind from any directions.
- It does not need to support the nacelle on the top of the tower since the gear box, brakes generators are located on the ground.
- Overall cost of the wind mill is reduced.
- The cost of maintenance is low.
- Design of the whole structure is comparatively easier.
- It consists of a hollow vertical shaft mounted between the top and bottom bearings. The lower bearing is supported on the foundation.
- The upper platform is supported by six guy ropes. The height of tower is about 100 m.
- Two thin and curved blades are attached at the rotor shaft at the top and bottom as shown. These blades form a symmetrical configuration about the vertical axis.
- The blades have the aerofoil section. The turbine shaft is coupled to a generator having in between the disc brakes, electrical controls, the gear box and the flexible coupling.
- Both the turbine and generator operate at variable speeds. Such wind mills run at large tip-speed ratio.
- The mechanical energy developed by the turbine rotor is converted into electrical energy by the generator.