A wind energy system transforms the kinetic energy of wind into mechanical or electrical energy that can be harnessed for practical use. Mechanical energy, most commonly used for pumping water in rural or remote locations, powers the “farm windmill” still seen in many rural areas of the U.S.
Wind turbines generate electricity in a straightforward way: wind moves the blades of the turbine, which spin a central shaft. The shaft connects to an electrical generator, often located at the top of the tower, which produces electricity. They are deployed at homes, farms, businesses, utility-scale wind farms, and other locations.
There are two basic designs of wind turbines: vertical-axis (“egg-beater” style) and horizontal-axis (propeller-style) machines. Horizontal-axis wind turbines are most common today, constituting nearly all of the utility-scale (100 kilowatts (kW) capacity and larger) turbines in the global market. Small-scale turbines (50 kW capacity and under) are used to power isolated communities and other areas where large turbines are not feasible. Today turbines with capacities as large as 5 megawatts (MW) are being tested.
Wind farms may also be located offshore, where the average wind speed is much higher than on the land. Most offshore wind turbines are fixed to the ocean floor, while some newer models float on platforms.