- Each vacuum tube consists of two glass tubes.
- The outer tube is made of extremely strong transparent botosilicate glass that is able to resist impact from hail up to 25mm in diameter.
- The inner tube is also made of borosilicate glass, but coated with a special selective coating , which features excellect solar heat absorption and minimal heat reflection properties.
- The air is evacuated from the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss.
- This is why the tubes are able to absorb the energy from infrared rays which can pass through clouds.
- Wind and low temperatures also have less of effect on the function of evacuated tubes when compared to flat solar collectors due to the insulating properties of the vacuum.
All-glass vacuum tubes are the key component of the solar collectors and solar water heater.