Fit a window-mounted AC unit into horizontally sliding windows. Should work with casement windows, too -- at least that's what I hope!
How to make a frame so a horizontal ac unit can fit in a vertical casement window. This also makes it easier to remove the ac and take it with you when you leave, ensuring you get your apartment deposit back.
Mounting a Standard Air Conditioner in a Sliding Window (From the Inside, Without a Bracket): 6 Steps (with Pictures)