I agree with your first thought, under the three windows is a good place for the bed. If you put it against the wall to the right you'll have limited walking space at the foot.

If you're worried about it being too bright, I would purchase 3 blackout shades. They can be cut to size at any big box hardware store. Use them at night, and then roll them up entirely during the day. Add drapery panels for visual appeal and a cornice board to hide the shades when they're rolled up. [houzz=]