This technology seems to be the go, especially down here in southern Victoria. From what I can tell there seems to be two diferent types of collector. One type uses a number of straight glass tubes with a central copper core containing a low boiling point liquid which is used to transfer heat to a main water tank. The concept is quite clever and seems more efficient and simple than conventional flat black panels. The other type uses U shaped glass tubes with the inner tube coated in heat absorbent material which somehow manages to transfer heat to the main tank. Though the science is basically the same I cant see how the heat is transferred to the water in this scenario. Does the heat pass through the glass to the water ? Which is the better system ?
Anyone out there with knowlege of these systems ?

Deano