All glass vacuum tube collector

The evacuated tube is similar to a conventional Dewar flask and consists of two borosilicate glass tubes, a glass with high chem

All glass vacuum tubes are the key component of solar collector.the vacum tube is similar to a conventional Dewar flask and consists of two borosilicate glass tubes,a glass with high chemocal and thermal shock resistance.the outer side of the inner tube is coated with a sputtered solar selective surface.this coated inner tube is closed at one end and sealed at the other end to the outer tube.the annular space between the outer tube and inner tube is evacuated to virtually eliminate heat loss by conduction and convection.

DetailAll-glass Evacuated Solar Collector Tube Specifications 

Specifications for all-glass evacuated solar collector tube 

Configuration	two concentric borosilicate  glass tubes						triple concentric borosilicate glass tubes
Diameter of cover tube	47 mm		47 mm			58 mm
Diameter of absorber tube	37 mm		37 mm			47mm
Length	1500 mm	1200 mm		1500 mm	1800 mm			1600 mm
Coating technology	Sputtered graded  Al/N-Al solar selective  Absorbing coating		Sputtered Al/N-Al solar selective Absorbing  coating with interference effect
Solar absorptance (AM1.5)	0.90		0.94			0.94
Emittance (80°C)	0.08		0.05			0.05
Heat loss coefficient	0.80 W/m2°C		0.65 W/m2°C			0.65W/m2°C
Transmittance of cover tube	0.91		0.91			0.91
Glass thermal expansion coefficient	3.3*10-6/°C		3.3*10-6/°C			3.3*10-6/°C
Stagnation temperature (1000W/m2 solar irradiation, with flat diffuse reflector)	240°C		270°C			260°C
Pressure between tubes	5*10-3Pa		5*10-3Pa			5*10-3Pa
Strength of glass	0.8 MPa		0.8 MPa			0.8 MPa
Impact resistance	withstand hailstones of 25mm in diameter
Strength(pressure tested)	0.8 Mpa		0.8 Mpa			0.8 Mpa
Warranty	5 years		5 years			5 years

Features:-The collector tube has excellent solar-thermal conversion and very low heat loss, and canbe used all year round in cold climates;- Good thermal performance even in low solar irradiation days;- The collector tube achieves reliability, using the same glass materials for match sealing;- The collector tube vacuum has a long life-time.- The cylindrical absorber is all-day quasi-tracking for a north-south orientation of tubes,and four seasons quasi-tracking for an east-west orientation of tubes.