all glass evacuated tube solar collector Hight absorbance and performance, antifreezing, fashionable design, Keymark, CE, Main features of all glass evacuated tubes solar collector:Manifold: aluminum alloy Head ... Number of tubes: 20 pieces Collector area: 2.88m² Tube vacuum degree: 5 x 10 to 3Pa Tube absorption: >88% Tube heat loss: <8% Working ...