I'm going to attempt to explain how it works, but keep in mind that I'm an accountant - not an engineer. Or plumber.
We needed three sections of tubes to support our household needs (some folks need four).
|Had to straddle the chimney|
The vacuum tubes are two layers of glass with a copper tube in the center. The copper tube is filled with "magic gas" with converts from a liquid to gaseous state thus creating heat. This heat transfers to the water that is flowing through the top pipe (the one that runs up through the roof, across the top, and then back down through the roof, moving left to right in the picture below). Since the only water in the system is in that one pipe (remember the tubes hold a gas, not water), the system is amazingly light weight. Each tube is independent so if one tube gets broken for some reason (a tree limb, a baseball), it doesn't shut down the whole system.
|Installing individual tubes|
The heat is transferred to the domestic hot water tank until the two tanks reach the same temperatures. Yesterday, a mildly sunny day, the water reached 140 degrees by mid-morning. If the DHW tank temperature cools too much, the system starts up again and rewarms it. Before anyone freaks out about how hot the tank water is, there is a mixing valve that adds cold water before it is used in the household. This is a required anti-scalding measure.
|The control unit with heat exchanger hidden inside|
|Close up of the tubes|
The whole thing is surprisingly subtle up there. You can't even see it unless you're in the Southeast section of the yard. Pretty cool