Wind turbine

A wind turbine is a device that converts the kinetic energy of wind into electrical energy. As of 2024, hundreds of thousands of large turbines, in installations known as wind farms, were generating over 1,136 gigawatts of power, with 117 GW added each year. Wind turbines are an increasingly important source of intermittent renewable energy, and are used in many countries to lower energy costs and reduce reliance on fossil fuels. One study claimed that, as of 2009, wind had the "lowest relative greenhouse gas emissions, the least water consumption demands and the most favorable social impacts" compared to photovoltaic, hydro, geothermal, coal and gas energy sources.

Wind turbines are manufactured in a wide range of sizes, with either horizontal or vertical axes, though horizontal is most common. Commercial power production horizontal-axis turbines usually have three blades, upwind of their towers. Vertical-axis turbines can be made to varied designs, including the "eggbeater" Darrieus, the giromill with straight blades, the Savonius with scoops suitable for rooftops and ships, airborne with wings tethered to the ground, floating (mounted on a floating platform), and various unconventional types such as with counter-rotating blades.

Blades are most commonly made of glass fiber composites, but carbon fiber which is stiffer, stronger, and less dense is also used. Smaller wind turbines are used for applications such as battery charging and remote devices such as traffic warning signs. Larger turbines can contribute to a domestic power supply while selling unused power back to the utility supplier via the electrical grid.

Wind turbines produce among the cheapest renewable energy, and are clean, emitting no greenhouse gases. They have a significant environmental impact such as on wildlife, but this can be mitigated. The power produced varies with the wind, not with demand, so it is an unreliable source of energy unless energy storage is available.