Anatomy of Modern Wind Turbine & Wind farms P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Physics is experience, arranged in economical order. — Prof. Ernst Mach Arganons of a Machine to Generate Lift for Power generation

Organon to mean a musical organ or just as a generic term, as we might speak of an organ of the body.

Classification of Wind Machines The adjectives horizontal or vertical attached to the two major classes of wind machine. This classification refers to the geometrical aspect of the driving shaft on which the rotor/wheel is mounted. An oldtime wooden machine with four sails (a type typified by the term Dutch windmill) is now called a horizontal-axis wind turbine (HAWT). Past usage terms it as a vertical windmill, because the path of a point on a moving blade lies in a vertical plane. A machine with a central vertical axis and a number of straight or bent vanes arranged in a direction more or less parallel to the shaft is today called a vertical-axis wind turbine (VAWT). In past times this was called as a horizontal windmill.

Major Geometrical Features of Modern Wind Turbines The principal subsystems which make up the total wind energy conversion system are the rotor, the power train, (3) the nacelle structure, (4) the tower, (5) the foundation, and (6) the ground equipment station.

The Turbine Rotor Subsystem Horizontal Axis Wind Turbine rotors are often described as “propeller-type”. indicating correctly that many of HAWT rotors decelerate the air, and their tip speeds (typically less than Mach 0.4) are much lower than those of aircraft propellers. The main components of the HAWT rotor are its blades fastened to a central hub. HAWT rotors usually contain either two or three blades. One-bladed rotors with counterweights are technically feasible but rare. As the rotor turns, its blades generate an imaginary surface whose projection on a vertical plane is called the swept area.

General Configurations of Horizontal-Axis Wind Turbines (Teetered-hub) upwind rotor (Rigid-hub )downwind rotor

Major classes in HAWT

Geometric Features Beyond Scientific Engineering The terms downwind rotor and upwind rotor denote the location of the rotor with respect to the tower. An unconed rotor is one in which the spanwise axes of all of the blades lie in the same plane. Blade axes in a coned rotor are tilted downwind from a plane normal to the rotor axis, at a small coning angle. Coning helps to balance the downwind bending of the blade caused by aerodynamic loading. The minimum distance between a blade tip and the tower is defined as Tower Clearance (TC). TC is influenced by blade coning, rotor teetering, and elastic deformation of the blades under load. Elastic deformation can be significant for blades fabricated from composite materials, such as fiber glass.

Often an axis-tilt angle is required to obtain sufficient clearance. Axis tilt is kept to a minimum because of potential negative side effects, such as reduced swept area and a vertical component to the rotor torque that can cause a yaw moment on the nacelle.

The Power-Train Subsystem