Having used solar panels for at least a dozen years I have LONG found that it's no big deal to turn the panels on and off manually. I have two ball valves, one for my south and eastern panels, and one for my north and western panels. THEORETICALLY, I could get better performance with robotic, computer controlled valves, but at what cost? If my pool gets too hot I merely turn the panels on at night and they act like a car's radiator, bleeding off heat energy.

Just, IMHO, it's over-kill.