No complex wiring here. The re circulation pump is wired directly to the PV panel. When the sun is out the pump will run, re circulating water from the storage tank, through the solar collector, and back into the storage tank.
A system like this, left unattended, must include a safety features in case the re circulation system malfunctions. If the re circulation pump stops running the fluid in the collector can quickly rise past the boiling point of water or even antifreeze. This will cause pressure buildup in the system and an explosion if there is not a pressure relief valve.
A temperature sensor in the collector could drive the heliostat of target to keep the collector from overheating in the event of a re circulation malfunction. Another solution could be to cover the aperture of the collector with a heat shield or secondary collector of some kind.