Low pressure solar collectors are wildly used in China for big projects where automatic thermosyphon heat collection is preferred Water flows directly in the evacuated glass tubes connected to the manifold. Features: 1) Highest efficiency 2) Thermosyphon heat collectable is one of the shining points 3) Economic 4) Suitable for big projects where the lowest ambient temperature is no less than -3° 5) Working pressure: less than 0.04MPa