A solar thermal system is provided. The system comprises at least one solar thermal collector for heating a heat transfer fluid (HTF); and at least one conduit for transporting the HTF into and out of the at least one solar thermal collector; wherein said at least one conduit is of a foam or plastics material.

A heat driven liquid close-loop automatic circulating system is provided. This system circulates the liquid in a close-loop by the collected heat in the loop. The system may operate without external power for the pump. The heat driven liquid close-loop automatic circulating system may employ a modified self-powered pump for heated liquid. The pump includes an airtight container for containing the heated liquid, a inlet and a outlet of the heated liquid, further more the modified self-powered pump has a breathing channel with a liquid vapor condensing and reflux structure. The heat driven liquid close-loop automatic circulating system may be a solar heated liquid close-loop automatic circulating system with a solar heat collector.