With wind turbines, the amount power you get depends of how fast the wind is blowing, which means dead air can be a problem. To smooth out the supply, Apple has filed a patent application for a system that stores excess energy when the wind is strong, and dishes it out again if the wind dies.
Unlike similar schemes that store the extra energy using batteries, Apple's system uses the rotation of the turbine to spin blades in a liquid so that they generate heat through friction. An adjustable heat exchanger transfers the heat to second liquid until it boils and can drive a steam turbine. When the wind is strong the first liquid will heat up beyond what is needed to boil the second liquid. Then during calm spells, the heat stored in the liquid can be used to make steam without the wind turbine's input.
Just why Apple is working on something so far removed from its current product lines isn't clear, although the company is known to use alternate energy sources at its facilities. I just wouldn't expect to see a MacBook with little wind turbines mounted on top anytime soon.