What are Wind Generators?

Wind generators, or wind turbines, are machines that convert energy from the wind into mechanical energy, which is then used to produce electricity. Developed for over one thousand years, wind turbines today are constructed in a range of models along either horizontal and vertical axis types. The smallest turbines manufactured are used to charge batteries or for auxiliary power on sailing boats, while the largest are parts of massive arrays that are becoming an increasingly more common and important source of electrical power.

Types of wind generators

There are two principal ways that wind generators are constructed - with the arms rotating around a vertical axis, and with the arms rotating around a horizontal axis. Horizontally oriented wind generators are both older and more common compared to the vertically oriented ones.

Horizontal wind generators

Horizontal-axis wind generators have an electrical generator and main rotor shaft at the top of a tower, and they must be pointed into the wind to be most effective. Small turbines use a normal wind vane to achieve this, while large ones use an electronic wind sensor and motor to align themselves properly. The arms of a generator are usually placed upwind of the supporting tower, due to the turbulence caused by the wind passing along the arms - having the arms upwind allows the tower to be unaffected by the turbulence, preventing fatigue failures. Turbines used in modern wind farms for the production of electricity for commercial use are usually three-bladed turbines oriented along a horizontal axis; because they can be turned into the wind easily using motors, these are the most efficient designs for harnessing and converting wind energy into electricity.

Vertical wind generators

Vertical-axis wind generators are designed so that the main rotor is arranged vertically, which allows the turbines to function without needing to be turned to face the wind, which can be an advantage at sites where the wind direction is variable (for example, when a generator is integrated into a building). However, the vertical alignment also leads to slower rotational speeds due to the higher torque. Having the turbine oriented around a vertical axis allows the gears and motor to be placed closer to the ground, making maintenance much easier and avoiding the need to build a tower to support the blades. There are three "subtypes" of vertical wind generators:

Darrieus wind turbine

These turbines have long, outwardly curved blades attached to the top and bottom of the rotor, similar in shape to an eggbeater. These turbines are quite efficient, but produce a large amount of cyclical stress on the rotor, contributing to poor reliability.

Giromill

These towers are similar to the Darrieus mills, but have straight blades instead of curved. This allows them operation that is more efficient in turbulent winds, and lessens blade bending stresses.

Savonius wind turbine

These have large, scoop-like arms that rotate around a central rotor. As long as they have three or more scoops, they are always self-starting wind generators.