Wind turbines convert the kinetic energy from wind into mechanical energy. When used with an electrical generator, the rotation of the wind turbine’s blades turns a shaft to produce electricity. There are two basic types of wind turbines: horizontal-axis and vertical-axis. Horizontal-axis wind turbines (HAWT) are the most popular type. They have two or three wing-shaped blades. Two-bladed turbines are operated downwind, with the blades facing away from the wind. By contrast, three-bladed devices are operated upwind. Vertical-axis wind turbines (VAHT) are shaped like an eggbeater and use one or more propellers or aerofoils. The Darrieus turbine is a type of VAHT in which the aerofoils are arranged symmetrically with a zero rigging angle. Although vertical turbines are limited by physical stress, they offer a wide range of operating speeds and easy access to the generator, which is located at the base of the turbine.