High performance evacuated tubes with selective coating

Linuo Ritter International distributes highly efficient evacuated tubes. We offer high performance evacuated tubes with an improved geometry and performance. The evacuated tubes consists of two concentric glass tubes which are sealed in a semi-circular shape on one side and are joined to one another on the other side. The space between the tubes is evacuated and hermetically sealed (evacuated insulation). To use solar energy, the internal glass tube is coated with an environmentally friendly, highly selective layer on the outside, thus turning it into an absorber. The selective coating is protected in the evacuated space. The aluminum nitride sputter coating used is characterized by an extremely low emission and a high absorption rate.


Absorbance rate after coating (AM 1.5) α% ≥94.5
Absorbance rate after evacuating (AM 1.5) α% ≥93.5
Emission rate after coating (80±5°C) α% ≤6
Emission rate after evacuating (80±5°C) α% ≤6.5
Stagnation parameter m²°C/Kw ≥240
Solar radiance exposure MJ/m² ≤3.0
Average heat loss coefficient W/(m²°C) ≤0.70
Selective coating material   SS-AL-N/Cu, SS-AL-N/Cu
Impact resistance   Steel Ball Test: Steel ball with diameter of 30 mm fall on the evacuated tube vertically from 450 mm height.
Vacuum Degree Pa ≤3×10(-3)
Pressure MPa 0.6
Transparent (AM 1.5)   ≥0.89 (ISO9806-1: 1994)