Vacuum tubes are the absorber part of solar water heater, consisting of double-layer coaxial glass tubes, made from extremely strong borosilicate glass 3.3, the inner tube coated by absorber selective coating, which absorbs solar energy and converts it into thermal energy for water heating. This type of tube is chosen as its reliability, efficient performance and low cost. More and more people regard vacuum tubes as their first choice in water heating.

The heat pipe is hollow with the space inside evacuated, the same as vacuum tube. In this case insulation is not the goal, but rather to alter the state of the liquid inside. Based on the principle of water boiling at a lower temperature with decreased air pressure. The heat pipes used in our solar collectors have a boiling point of only 25°C. So when the heat pipe is heated above 25°C the water vaporizes. This vapor rapidly rises to the top of the heat pipe and transfers the heat. As the heat is exchanged at the condenser top, the vapor condenses to form liquid and returns to the bottom of the heat pipe at once and then repeats the process.