Are all-glass evacuated tubular collectors more efficient than flat plate collectors?
On average, yes. Evacuated tubular collectors are superior to flat plate collectors in a number of ways: (a) Due to the cylindrical shape of the evacuated tube, the sun is perpendicular to the surface of the glass for most of the day. Flat plate collectors have the disadvantage that the sun is only perpendicular to the collector at noon and thus a proportion of the sunlight striking the surface of the collector is likely to be reflected. (b)As the name suggests, air is evacuated from the evacuated tube to form a vacuum. This greatly reduces conductive and convective heat loss from the interior of the tube. As a result wind and cold temperatures have minimal effect on the efficiency of the evacuated tubular collector. (c)Tsinghua all-glass evacuated tubular collectors can be used in subzero temperatures without the system sustaining damage. Flat plate systems often require expensive and complicated “antifreeze” systems to be installed. (d)Evacuated Tubes are strong, long lasting, and sh
