The evacuated (vacuum) tube:

Each evacuated tube is composed of two concentric glass tubes ; the inner one is coated with highly selective layer and it converts solar radiation into thermal energy, as for the outer one, it is a cover to keep the vacuum . Both tubes are fused together and the gap between them is evacuated to achieve excellent thermal vacuum insulation .

Technical Info Specifications:

Evacuated tubes
Glass material	borosilicate glass
Glass thickness	1.6mm
Coating	graded AL-N/AL
Degree of vacuum	>5x10-3 Pa
Hail proof	25mm
Absorption coefficient	>0.92
Emittance	<0.08
Average heat loss coefficient	< 0.6 W(m2.C° )^-1
Maximum temperature	200C
Service life	15-20 years
Size of single tube	58x1800 mm

Hot Water Tank
Structure	Dual layered water cylinders
Inner tank material	stainless steel 304 Food grade
Inner tank thickness	0.4mm
Outer tank material	PVDF Coated galvanized steel
Outer tank thickness	0.4mm
Tank insulation	50mm polyurethane
Silicon rubber	UV stabilized high temperature
Working pressure	non pressure system
Testing pressure	2 Bar
Cold Water Inlet	½”
Hot Water Outlet	½”
Packing	Recycled Card Board (Export)
Manufacturer Warranty	5 years

Stand
Material	Coated galvanized steel
Thickness	1.2 mm
Tilt angle	45 Degree

Why vacuum tubes?

Vacuum (evacuated) tube works like well-known, a thermos flask, which uses vacuum to provide thermal insulation; once the evacuated tube absorbs the radiation from the sun and converts it to heat; the vacuum helps keep the heat. The vacuum insulation makes evacuated tube collector excels the traditional flat plate collector in performance.