How does it work in the Winter at higher Latitudes?
If you are referring to a reverse osmosis unit, they are not affected by altitude. They are force fed by high pressure pumps.
I operated an industrial scale one at a hospital in the early 90’s. They were quite expensive, but they were very productive and efficient if properly maintained.
Another poster mentioned the Israelis purify water on a grand scale, I suspect their method is much more cost effective.
Regardless, trying to purify water via the evaporation by the sun is just a dumb as a solar panel, and most likely much less efficient than a solar panel.