So, you own one of these cheap Intex pools just like me (Well, not exactly like me, I'm cheap, I bought a cheap fake) and you wanna heat it, but you don't wanna waste electricity on it?
Great, me too!
I was trying to think of a solution, the first involved putting a barbeq into the pool, and firing it up for a few hours to heat up the water. that failed. horribly.
My second thought was solar! I bought a 30m long black garden hose, and rolled it on the concrete in my yard, and plugged it to the water circulation of the pool.
The result, was incredible, after only 2 hours the water temprature has gone up by 8 degrees.
After 4 hours it was hot like a hot tub, and in the evening when the kid was asleep, it was nice to relax there with a joint! :)
Good luck building :)
Ask me if you need help!
-Simba.