Wind turbines convert the kinetic energy of wind into mechanical or electrical energy. Historically, windmills have been used for centuries to grind grain and pump water, and modern large wind turbines can generate megawatts of electricity. The rotor captures the wind's energy, which spins a shaft connecting to a generator to produce electricity. Wind turbines are mounted on towers to access stronger winds higher above the ground. While wind energy has advantages of being renewable and producing no emissions, disadvantages include dependence on wind conditions and higher costs of offshore installations.