A solar collector works like an engine of any solar water heating system. Solar vacuum tubes are very much efficient in producing solar powered systems. The vacuum tubes work similarly like the coffee thermos.

The  vacuum tubes comprise of two glass layers with vacuum in between the  layers. The outer layer of the tube is made from Borosilicate glass,  which has very low iron content. The Borosilicate glass allows around  98% light energy to enter. The second layer is applied with special  coating.