Comment by GistNoesis

The area comment was more relative about the power received : To be able to have the power on the ground you need to reflect it from space (pointing the obvious that with 100sqm of surface area, you can't collect more power than surface area * power density). You also don't want to overheat everything (otherwise you need sun towers instead of solar panels), so a ball park of around 1:1 is a good starting point.

To focus light, the ideal shape is a parabola, and it's a shape that occur naturally when you spin liquid in gravity. (Their are process to build big telescopes which only point up). Of course you don't have gravity anymore, but you can pull on your surface with fields, or you can have concentric rings that you align more or less along the axis to deform the surface. We don't need perfect focus just a rough spot.