WIND A wind farm or wind power installation comprises one or more wind turbines which transform the wind’s kinetic energy into electricity. The power of the wind turns a rotor with two or three blades connected to a d horizontal axis. Through a mechanical system which multiplies the number of revolutions, the rotation is then transferred to an electric generator. After being suitably transformed to a higher voltage level, the energy produced is released into the electric power grid.

Wind turbines are installed onto towers high enough to capture a greater amount of energy from the wind while avoiding turbulence created from the ground or obstacles.

A site’s wind characteristics are a critical factor which determines a wind power installation’s concrete feasibility. In fact, taking into consideration that the production of electricity for wind installations is proportional to three times the wind speed, small differences in a site’s anemometric characteristics can translate into in considerable differences in actual producible energy.

A generator, whether with a vertical or horizontal axis, requires a minimum wind (cut-in) speed of 3-5 m/s, providing power at a wind speed of 12-14 m/s. At high speeds (20-25 m/s, cut-off speed) wind turbines are blocked by the braking system for safety reasons.

Wind turbines can be subdivided into different power classes, depending on various dimensional specifications:
  • Small size (from 1kW to 200 kW): rotor diameter 1- 20 m; tower height 10 30 m
  • Medium size (from 200kW to 800 kW): rotor diameter 20 50 m; tower height 30 50 m
  • Large size (over 1000 kW): rotor diameter 55 80 m; tower height 60 120 m
Small sized wind turbines can be used to produce electricity for individual users or groups of users with a low voltage connection to the power grid, or even isolated from the power grid.

Medium and large sized wind turbines are mostly used in large installations known as wind farms, where they are connected to a mid to high voltage power grid.

The main components on a wind turbine are:
  • the rotor, comprising blades generally made of fiberglass, coupled to a hub;
  • the shuttle or gondola, or a generic housing structure containing the transformation systems (mainly the speed multiplier and power generator) and machine controls;
  • the tower, with the foundations or support structures