Cold Water != Fun Water
My swimming pool only get a few hours of direct sunlight each day, so the water temperature never gets above 75 degrees Fahrenheit (24 degrees Celsius). To help increase the temperature, I built a simple solar water heater using black irrigation tubing and a bilge pump. (I could have tapped directly into the pool's filter, but it's in the shade and I would need a lot of tubing to reach the sunny spots.)
I found a tutorial online on how to put together the heat coil. Basically you take 200' of black irrigation tubing, and attach it to a board. I skimped on the zip ties, don't do that. Drill all of the holes and use as many zip ties as possible. By the end of the summer, my coil had come undone in places and looks generally, like crap.
Once you have your coil complete, attach the bilge pump to one end of the coil, submerge the pump, and start pushing water through the coil. Stop the pump and let the sun warm the standing water inside the hose. Periodically touch the coils until you feel it getting hot. Turn your pump on again while feeling the coils, they should feel cool to the touch after only a minute or so, depending on how old your pool water is. Time how long it takes for each hot/cold cycle and use that when connecting your Omega and relay.
Prototyping in a spare plastic container.
Logging when the relay switched on and off.
I can't say it was a total success or a total failure. The water was a little warmer where the hose emptied into the pool, but not much anywhere else. I feel that in order to make a dent in my pool's temperature, I would need 3 coils and a few more hours of sunlight in my backyard. Or a really long hose, so I could place the coil in my front yard where it's sunny all day and faces south (for more direct sunlight). My neighbors will love it!
Upgrade to a real project box, I eventually traded out the 12v to 5v converter to a smaller module.
When I try this again next year, I will add temperature sensors in the pool and in the coil to monitor when the best time to turn the pump on will be, and logging this data to phant will be added as well.
Weather proof box with lid on. Quick connect banana plugs to the pump.
The project box ended up at the bottom of the pool one day when the pool vacuum 'bot got tangled with the pump. Everything dried out nicely in the summer heat though. And it was a good thing the power supply didn't fall in too.
As you can see, not a lot of direct sunlight falls on the pool.