Horizontal-Axis Wind Turbine

A horizontal-axis wind turbine is a wind turbine whose main rotor shaft runs parallel to the ground, converting the kinetic energy of wind into electricity, and it is the design that dominates the modern wind industry: commercial horizontal-axis turbines typically carry three blades mounted upwind of their own tower. As of 2024 hundreds of thousands of large turbines, most of them horizontal-axis machines, were operating in wind farms worldwide, together generating more than 1,136 gigawatts of power, with another 117 gigawatts added that year alone. Turbine blades are built mainly from glass fiber composites, with carbon fiber used where its greater stiffness, strength and lower weight justify the added cost, and a 2009 comparison found wind power carried the lowest greenhouse gas emissions, the lowest water use and the most favorable social impacts among the renewable and fossil generating technologies it was measured against. Horizontal-axis machines range from small turbines that charge batteries or power remote equipment up to large grid-connected installations that supply whole communities, and because their output depends on the wind rather than on demand, they need storage or other generation to back them up when the wind drops.