This type uses the all glass evacuated solar collector tubes as the heat-absorbing element. The high vacuum degree of the clearance between the outer and inner tube reduces the heat emission which is caused by convection and conduction. The layer films(coating) of the all glass evacuated tubes transfer the sun energy into heat energy. The high absorption and low emittance rate of layer fils is unique. Depending on the different density between hot water and cold water, a water flowing cycle is created in the tube. Hot water flows automatically upwards while the cold water flows downward. The water in the storage tank will be heated from this natural circulation.