The 100mm metal glass vacuum heat pipe tube is fully evacuated. 

The solar energy passesthough the glass and is absorbed by the selective coating on the aluminumabsorber, thus it becomes hot.

The heat is transferred directly to the heat pipe, making the heat-transport liquid inside evaporated very fast. 

The evaporationsteam goes up to the condenser on the top and the heat is transferred to theheat transfer fluid inside the pipe, and therefore the heat is kept inside thewater tank.