Solar Thermal

In a solar thermal system solar energy is captured and transferred from solar light to water through a panel on the roof of the house, a closed hydraulic circuit, and a water storage tank.
This type of energy warms up the water, which is present in an accumulator, which is used for heating domestic hot water and for heating the rooms (hot water goes into floor heating or in traditional heating systems).
The most common systems are two: natural and forced circulation.

Natural circulation	Forced circulation
Thermal energy is transferred from solar light to water through a panel located on the roof of the house. The water is heated by convection in a storage tank (boiler), which is to be placed higher than the panel, from which it is distributed to domestic users. The circuit is closed, as the water being consumed is replaced by the external outflow. This system has the advantage of simplicity but is characterized by a high thermal dispersion, at the expense of efficiency	The thermal energy is transferred from the sunlight to the water through a panel located on the roof of the house where a fluid transfers the energy to the reservoir located in a room of the house, using a pump and an electronic control unit . The circuit is than composed of the panel, a coil inside the boiler and the connection pipes. A pump, called circulator, allows the transfer of heat collected by the fluid, in this case propylene glycol, similar to ethylene glycol (the liquid used for car radiators), to the coil placed inside the boiler. The circuit is considerably more complex, having an expansion vessel, a temperature control and other components, and has an electrical consumption due to the pump and control unit, but has a much higher thermal efficiency since the boiler is placed inside and therefore less subject to thermal dispersion overnight or in adverse climatic conditions.