Evacuated tubes are the absorber of the solar water heater. They absorb solar energy converting it into heat for use in water heating. Evacuated tubes have already been used for years in Germany, Canada, China and the UK. There are several types of evacuated tubes in use in the solar industry. Apricus collectors use the most common "twin-glass tube".

Length(nominal):1500mm/1800mm
Outer tube diameter:58mm
Inner tube diameter:47mm 
Glass thickness:1.6mm
Thermal expansion:3.3x10-6 oC
Material:Borosilicate Glass 3.3
Absorptive Coating:Graded Al-N/Al
Absorptance:>92percentage (AM1.5)
Emittance:less than 8percentage (80oC)
Vacuum:P<5x10-3 Pa
Stagnation Temperature:over200oC
Heat Loss:less than0.8W/ ( m2oC )
Maximum Strength:0.8MPa