Big Large Diameter Solar Vaccum Evacuated Collector Tubes 125 x 500 to 125 x 1800

Gaia Solar Evacuated Collector Tube

The evacuated tube is the key component to all the thermal heaters and systems. It’s similar to a conventional Dewar flask and consists of two borosilicate glass tubes, resistant to high chemical and thermal shock. 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 avoid heat loss in conduction and convection.

The key element determines function of tube is the technology of the film coating, and Gaia Solar uses the Patent of the University of Sydney to produce tubes and our tube is the best efficiency tube you can find in China, with the highest absorptance of near 97% with common rate of 94% and lowest emission rate near 3% with common rate of 5%. At this efficiency, it has been very hard to improve the function any more, even very little part. And the film can be divided into bellowed four layers as drawing:

The four layers are metal infrared reflector layer, HMVF cermet, LMVF cermet and anti reflection layer. When the tube is placed into the coating machine, pumps draw the air outside and form a vacuum at about 1x10^-3. Later on, some nitrogen was sent into the coating machine and form a film of Al/N-Al. at this stage, the main percentage of the film is AL for there only very few Nitrogen enters the coating machine. So this stage film is called High Metal Value Film (HMVF). And little by little, more and more nitrogen was released into the coating machine, and form Al/N-AL film, but at the stage, the percentage of Nitrogen increases and forms Low Metal Value Film (LMVF). At last, an anti-reflection layer was made on tube to reduce the emission rate of the film. Thus the coating procession if finished.

During the whole procession, with continuously entrance of nitrogen, difference content AL/N-AL film forms. Some companies thus said their tubes have many layers and even ten thousands layer. But it is not the number of layers and the thickness of layers affect the efficiency of the tubes but the production technology and the data designed, even the quality of the materials. Bellow attached is efficiency curve of Gaia Solar vacuum tube and technical datasheet on tubes