The main components of a solar thermal system :
The dual coil solar cylinder, pump station, and collector.
Solar radiation is absorbed by the collector, heating the water either directly (the water is pumped through a manifold connected to the collector) or indirectly (the domestic water is heated by a heat-transfer fluid).
The controller switches the pump on when the difference between the temperature on the roof and the temperature at the bottom of the cylinder is sufficiently large (typically 10 degrees). The pump circulates water or heat transfer fluid around the system and heat is transferred from the roof into the bottom of the tank.
Top up heat is provided by the boiler as required.