After oil runs out, as it will eventually, perhaps the world will use the electric energy of the ionosphere. The electric energy of the ionosphere is virtually unlimited and is continuously renewed by the sun and has a big role in producing hurricanes and stuff. Harnessing this energy would have the additional advantage of reducing the number and strength of hurricanes. That is, if we could use enough energy, which is questionable because there is a godawful amount of energy up there.