Wind power is the kinetic energy of wind, harnessed and redirected to perform a task mechanically or to generate electrical power. Sailing and similar activities are among the simplest, oldest and most direct applications of wind power. Mechanical uses of wind power go back to ancient Greece. The first wind wheels, for example, relied upon gearing and shafts to power machinery. Windmills drive a millstone to grind grains, among other purposes. Wind has also long been used to power mechanical pumps to draw water for use and to drain land for agricultural purposes. The basic wind turbine design consists of a bladed rotor that drives a shaft to a generator. The generator uses electromagnetic induction to produce a voltage. Wind power was used to enable electrolysis, the separation of water into hydrogen and oxygen, to make it possible to store energy as early as the 1890s. Today, small-scale wind turbines for individual use generally have a maximum output of 400-1600 watts. In contrast, the largest industrial turbines might generate as much as 7.5 megawatts. Groupings of turbines are known as wind farms or wind parks. Although windmills are still in use, wind turbines have become more common as the interest in renewable energy increases