The amount of energy from the sun that hits the earth in one hour is enough to power the entire globe for an entire year. So given inefficiencies and losses and that we can't cover everything with PV panels - it would take a month to gather enough energy for an entire year.
And that is just solar PV. Overall from all the different sources of renewable energy, we can gather about 16X as much energy as we need.
http://earththeoperatorsmanual.com/f...erators-manual
POWERING THE PLANET | Earth: The Operators' Manual
http://earththeoperatorsmanual.com/f...ergy-quest-usa