"I'd like to fill a room with ambient daylight by bouncing LED light off the ceiling."
EDIT: Poor wording, but by "fill", "ambient" and "daylight", I'm not considering the intensity, but just how to focus and direct whatever light output I have, to achieve a "general brightness from above" similar to being under a bright sky, avoiding direct glare. For instance, should I try to cover most of the ceiling with a wide beam, or direct a narrower beam towards its center? And ultimately, how to choose lens/reflector components for COB LEDs.
"Initially I would test with 15x10W LEDs aimed diagonally upwards from the top of a shelf."
EDIT: I'm not expecting to simulate sunlight with 150W, it's just seems like a reasonable place to start in terms of cost and managing the cooling requirements. There is an article about DIY SAD treatment by bouncing 150W directional light off the ceiling, using a ceramic metal-halide bulb. In 2017 it seems possible to achieve 100 lm/W and CRI: 95 with LEDs at a similar cost. The author finally suggests using 25,000-50,000 lm, which would be 2-4 times more than 150W.
"If the LEDs' emission angle is 120°, how important are lenses and/or reflectors for this kind of setup, and what do I need to consider when choosing them?"
EDIT: I understand that this question might not be appropriate here, what I'm looking for is the big picture of how to find and select a lens for COB LEDs. I don't think the Physics SE would be suitable for that, either. I apologize and respect any decision by the mods. :)
Thank you for the detailed and insightful answers!