In this post Why not use our own light production to produce new energy instead of wasting it?, I naively asked if it was possible to also recycle our own lightning at night. someone, in his answer, also noticed that photoelectric cells are highly angle dependent.
Hence my first thought: why the photoelectric cells are not designed to be hemispheric?
EDIT1: people misunderstood, so I'm correcting: I mean the panel would be flat, parallel to the ground for example, but each photoelectric cell would be hemispheric. Thus getting optimum direct radiance over time from the sun as also irradiance from the whole sky. As side-effect, light from every point and also because cells are highly reflective, including sunlight would also bounce multiple times from one cell to the others around before dissipating instead of being reflected toward the sky. So does it worth it?