Each dark blue glass tube is a double-walled borosilicate flask. The inner tube is coated with a selective material that absorbs solar radiation while minimizing heat reflection.
Water flows naturally into the vacuum tubes from the main horizontal storage tank.
As the sun warms the water inside the tubes, it expands and becomes less dense (lighter).
The hot, light water floats upward out of the tubes and into the storage tank, while colder, denser (heavier) water from the bottom of the tank sinks down into the tubes to replace it.
This continuous loop requires no electric pumps.
The main horizontal tank features thick polyurethane insulation that traps the hot water inside, ensuring it stays hot for use at night or early the next morning.