Our energy source will run out, there is much speculation on when exactly this will happen but it WILL happe if we do not find an alternative.
Green energy is promising but still not as reliable as our current energy sources, and the earths reserves of uranium will become scares in the years to come. So I propose that we turn our focus back to the atomic age for some answers. In the 1960s it was discovered that the abundant element thorium had very high energy density and could be used in special reactors that utilized liquid fluoride.
These liquid fluoride reactors also have no need to be kept under pressure and have no chance of nuclear meltdown. They are in fact "walk away safe". This may be an alternative to our current energy issue.