Here in the sunny south, near Atlanta, our swimming season is pretty long, but longer would be nice! I'd given some thought to installing the extruded plastic collectors on the south-facing roof of our pool house. The solar orientation is close to ideal, the collectors are relatively light, and the plumbing would be so simple, since the pump/filter is in the south-west corner of the building.
Then I had an idea, a dangerous event for me! I wonder if, in addition to collecting solar energy during the day in early spring and late fall to extend the swimming season, the same collectors could circulate pool water at night during the height of summer to dump excess heat. Our pool temperature seems to approach body temperature in late July and early August, hardly refreshing. I imagine that I'd need some idea of the average low night temperature during the height of summer, and the actual water temperature. I'm not an engineer, but I suspect that the greater the temperature difference (delta T?) between the pool water and the atmosphere the better this might work. Clear nights might be more effective in radiative cooling, while cloud cover might mean only conduction to cooler air would be effective.
A differential temperature control valve to bring the collector/radiator on or off line would be a nice though probably costly addition for either heating or cooling.
Any engineers out there? Any one have opinions? Any experience with the roll out collectors?