Description

All glass evacuated tubes are the key component of solar collectors. The evacuated tube is similar to a conventional dewar flask and consists of two borosilicate glass tubes, a glass with high chemical 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. We use the tubes which use the successfully developed innovative Advanced Solar Selective Coatings in commercial scale, which achieve the highest thermal efficiency and good thermal stability. Solar selective coatings absorb most solar radiation while simultaneously suppressing the thermal emittance loss from coating surfaces. They vary mainly in their optical property and thermal stability. Excellent results have been obtained by using DC magnetron sputtering technology. A solar absorbance of 0.*4 - 0.*6 with an emittance of 0.*4 - 0.*6 at **0 centigrade has been achieved