Large turbines require ultracapacitors or rechargeable batteries to power operating equipment, such as blade-pitch controls to ensure that rotors continue spinning, yaw mechanisms that maintain blade position facing the wind, and hydraulic brakes which lock blades during turbulent weather. In addition, computer systems and aircraft lights need electricity that comes from the power grid.
In frosty regions, blade heaters are used to ward off icing. Some heaters use as much as 20 percent of a turbine's energy output. The nacelle, the enclosure that shields the gearbox, also requires heaters and dehumidifiers.
During periods of little to no wind, large wind turbines employ their own generators to keep the blades turning.