Solar thermal systems use solar collectors to absorb the energy of the sun’s rays. When exposed to the sun, the collector warms up. The temperature sensor, located on the collector manifold, sends a temperature reading to the controller. When the collector reaches the required temperature, the controller turns the pump on and that pump starts pushing a heat transfer liquid trough the system. When the liquid goes through the collectors, it warms up and then flows down to the heat exchanger to heat cold water. On cloudy days, when the sun is not providing enough energy, water is warmed up with a conventional water heater, so you are never left without hot water.

(Solar water heating diagram)