Solar heater - could it also cool water a little?

[BigDave]

They should be installed to drain back. The GL-235 has a freeze protection option that will run water through the panels when temp gets near freezing to keep them from freezing and bursting.

[Sean OBrien]

Keep in mind, the glazing on the collector will work to prevent significant thermal losses at night.

If you have a large enough property with an area that is free from tree roots - you could use geo-cooling without too much of a problem. Ground temperature even a few feet below the surface are significantly cooler than air temperatures. You could use a thermostatically controlled valve to shunt water into a horizontal loop collector in order to cool the water before it goes back to the pool.

I am sure there is information around regarding the setup - and there isn't much difficult engineering in this particular application (nor extremely expensive materials). The biggest restriction would be the hole that you need. Horizontal loops are easy for DIY projects, you just need a large area to dig a 3 foot deep hole in. If that isn't an option - vertical loops work as well - though for those you usually need to hire a boring company to come in and drill your holes.