How to solar power the world
How much surface area would we have to devote to solar cells in order to power the whole world? A physics professor at Berkeley named Mattias Loster decided to extrapolate some answers. Assuming the entire world uses about 18 terrawatts per year (which we do) and the solar cells installed had just 8% efficiency (a low average), the black discs represent the surface area needed:
For technical and political reasons (and certainly economic as well), it probably doesn't make sense to build solar cells that average 150,000m in diameter, but it's an interesting thought nevertheless.