Another important advantage that vacuum tubes have given to the solar heating industry is the extremely low temperature loss of zero. In such a way that the problem of water freezing inside these pipes at minus 20 degrees was eliminated and the need for antifreeze and insulation was practically eliminated.
To produce this product, permanent melting furnaces and glass surface coating devices are needed. Because of the need for high investment, the mass production of this product was actually concentrated in China, and despite the fact that its technical knowledge was related to Germany. , but its development and commercialization was realized in China.
Vacuum tube collectors consist of two glass tubes inside each other, which creates a relative vacuum in the space between these two tubes. By coating the outer surface of the inner tube with a layered combination of copper, aluminum and steel nanoparticles, an absorbent surface is created. Vacuum creates a very good thermal insulation. Therefore, when the water inside the tube is boiling, the outer surface of the tube is cold. Also, when the air surrounding the pipe is below zero, the water inside the pipe does not freeze.
The advantage of vacuum tubes is cheap price and no heat loss. Its disadvantage is its short lifespan compared to flat plates and its greater vulnerability.
Thermosiphon low pressure water heaters are made from vacuum tubes. Also, by adding a copper core and aluminum fins inside it, heat pipe collectors can also be made, which can be used in the production of high pressure vacuum tube solar water heaters.
With vacuum tubes, a variety of vertical and horizontal (propeller) collectors are made, which can be used in high capacity spa production.