All glass evacuated solar collector vacuum tubes are the key component of the Solar Collectors. Each evacuated tube consists of two layers of glass tubes. The outer layer is made of extremely strong transparent borosilicate glass that is able to resist impact from hail up to 25mm in diameter. The inner layer is also made of borosilicate glass, but coated with a special selective coating, which features excellent solar heat absorption and minimal heat reflection properties. The air is withdrawn (evacuated) from the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss. Unlike other types of solar collectors, evacuated tube solar collectors still provide excellent results on cloudy days. This is because that the tubes are able to absorb the energy from infrared rays, which can pass through clouds.
Wind and low temperatures also have less of an effect on the function of evacuated tubes when compared to flat plate solar collectors due to the insulating properties of the vacuum.

Three target vacuum tube proformance and specification:

Tube structure

All-glass double deck co-axial structure

Glass material

High borosilicate 3.3 glass

Out tube diameter and glass thickness

Φ47±0.7mm; Glass thickness 1.6±0.15mm

Φ58±0.7mm; Glass thickness 1.6±0.15mm

Φ70±0.7mm; Glass thickness 2.0±0.15mm

Inner tube diameter and glass thickness

Φ37±0.7mm; Glass thickness 1.6±0.15mm

Φ47±0.7mm; Glass thickness 1.6±0.15mm

Φ58±0.7mm; Glass thickness 1.6±0.15mm

Tube length

800mm, 1200mm, 1500mm, 1600mm, 1800mm, 1900mm, 2000mm, 2100mm etc

Absorption coating property

Coating material

CU/SS-ALN(H)/SS-ALN(L)ALN

Sediment method

Three target magnetron sputtering plating

Absorptivity

Absorptivity: α=0.92～0.96 (AM1.5)

Emission ratio

Emission: ε=0.04～0.06 (80℃±5℃)

Vacuum degree

P≤5.0X10ˉ³ (PA)

Stagnation temperature
(temperature inside of empty
evacuated tubes)

260～300℃

Average heat loss

ULT 0.4～0.6 W/(m2～﹡℃)

Hail resistance

Φ25 mm

Pressure-endure

1MPa