There is an interesting graphic by solar panel advocates showing the area needed to be covered by solar panels to fuel the world. These are obviously huge areas but it offers an interesting perspective.
The advocates point out that large areas of such panels could produce massive amounts of energy — particularly if located in places like the Saharan Desert. (That would make the currently poor Saharan people the new energy-rich producers). According to the site, the total energy needs for 2030 could be met with less than 500,000 square kilometers of solar panels.
Obviously, there are tremendous technological barriers in getting energy from such spots to population centers and maintaining such massive grids. However, it does offer an alternative view of how to break our dependence on oil.