[komodus]

Ten years

Water wheels for a start, then dams, hydroelectric power and industrial revolution around the corner in just a year. Then ethanol/corn fueled engines and we'll be sailing/flying in no time. Trains will go electric right away instead of steam/diesel/gas. A small country with smart people and good leadership would easily build the first computer and nuclear bomb in less than a decade. From there, world domination.

[komodus]

To expand a bit more, energy is the fuel of civilization, since we won't have oil at surface level and solar won't be possible without panels, we should concentrate in generating hydroelectric power from rivers that will still be there. With unlimited power everything else is just as easy to rebuild.