Here is a good reminder of exactly how little area is required to provide enough solar power for the entire world. Below is a map that shows the area we'd need from the Northern Africa desert in order to get the job done.
An area of 158 miles x 158 miles would be enough to meet the total electricity demand of the world. The amount of electricity needed by the EU-25 states could be produced on an area of 68 miles x 68 miles. For Germany with a demand of 500 TWh/y an area of 28 miles x 28 miles is required, which concerns 0.03 % of all suited areas in North Africa.
Our planet receives 6,000 times more energy from the sun every day than all seven billion of us can consume. [Clean Techies]