|Configuration||Double-layer concentric boronsillicate glass tubes|
|Glass thermal expansion coefficient||3.3*10-6/||3.3*10-6/|
|Diameter of outer tube||φ47||φ58|
|Diameter of absorber tube||φ37||φ47|
|Transmittance of outer tube||0.91||0.91|
|Solar selective absorbing coating||Al-N/Al||Al-N/Al|
|Average Heat loss coefficient||≤0.8W/(*)||≤0.8W/(*)|
|Solar irradiation under stagnation||≤3.2MJ/||≤3.2MJ/|
|Hailstone resistance||hailstone diameter25mm||hailstone diameter25mm|
·Each tube is consists of two layer of glass tubes.
·The outer tube is made of extremely strong transparent quartz sand which can resist impact from hail up to 25mm in diameter.
·The inner tube is also made of quartz sand, but it is coated with a special selective coating with strong heat absorption and lowest heat loss.
·The air is evacuated from the space between the two glass tubes to form a vacuum, so it eliminates heat loss.
·This why the tubes are able to absorb the energy from infrared rays which can pass through clouds.
· So it also can operate in low temperature and low sunlight medium.