Vacuum tubes absorb solar energy converting it into heat. Vacuum tubes consist of two glass tubes which are fused together at one end. The inner tube is coated with a number of selective coatings that absorb solar energy efficiently, but inhibit radiant heat loss.

The air is withdrawn from the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss. These tubes perform very well even in low temperature conditions.

The heat pipe is hollow and the space inside contains liquid. The pipe is then vacuumed and sealed. Under vacuum the liquid has a low boiling point of 25ºC. When the heat pipe is heated above 25ºC, the fluid starts boiling, causing vapour to rise to the top.

This vapour then condenses to fluid in the condenser, causing heat to be transferred. The condensed fluid flows back to the bottom of the heat pipe where the sun begins the process again.

Not all vacuum tubes contain a heat pipe and condenser. There are systems available where the water flows through the tubes. These would be suitable for frost free areas only.

Vacuum Tube Technology versus Flat Panel Collectors

  • Vacuum tubes are approximately 80% efficient compared to 40% for flat plate collectors.
    Flat plate collectors suffer severe performance degradation in cold ambient conditions whereas vacuum tube collectors are relatively unaffected and can operate down to temperatures well below zero degrees Celsius.

  • The design of vacuum tubes allows them to collect more of the sun’s energy for a longer period of the day. At noon, both vacuum tubes and flat panels are perpendicular to the sun and at maximum efficiency. At other times, only the tubes are still perpendicular to the sun and at maximum efficiency. Flat plate collectors reflect the sunlight.

  • If the glass of the flat panel is broken, it will have to be replaced and the system will not work properly until it has been attended to. Vacuum tubes can withstand 25mm of hail. Should one be broken, it is an inexpensive component and easy to replace. In a system with a heat pipe and condenser, the system will still work even if one or two tubes are broken.

Technical Data
Available in 18 , 24 or 30 pieces of Vacuum Tube - 58mm x 1800mm
Heat Delivery Component - Super Heat Pipe (Copper)