All-glass evacuated tube :
Consists of two glass tubes which are fused together at one end. The inner tube
is coated with a selective surface that absorbs solar energy well but inhibits
radiative heat loss.
The air is withdrawn ("evacuated") from the space between the two glass tubes to
form a vacuum, which eliminates conductive and convective heat loss.
These tubes perform very well in overcast conditions as well as low
temperatures. Because the tube is 100% glass, the problem with loss of vacuum
due to a broken seal is greatly minimized. Glass-glass solar tubes may be used
in a number of different ways, including direct flow or heat pipe configuration.
Technical data table
Model tapeTG47 TG58
Outer tube diameter47mm 58mm
Inner tube diameter37mm 47mm
Glass thickness1.6mm 1.6mm
MaterialBorosilicate Glass 3.3 Borosilicate Glass 3.3
Absorptive CoatingAL/N/AL AL/N/AL
Absorption coefficient>92% >92%
Emission coefficient<8% <8%
Net weight 2.1KG