The evacuated tube is a product with improved geometry and performance and consists of two concentric glass tubes which are sealed in a semi-circular shape on one side and are joined to one another on the other side. The space between the tube is evacuated and then hermetically sealed (evacuated insulation). To use solar energy, the internal glass coated with an environmentally friendly, highly selective la er on the outside, thus turning it into an absorber. The coating is protected in the evacuated space. The aluminum nitride sputter coating used is characterized by an ex u extremely low emission and a high absorption rate