Are evacuated tube solar collectors more efficient than flat plate solar collectors?
When comparing peak efficiency levels, it may seem that there is little difference between flat plate and evacuated tubes. In fact, the efficiency of flat plate may be higher, but this is under minimal heat loss conditions. When averaged over a year, the evacuated tube solar collector has a clear advantage. The key points are as follows: 1) Due to the cylindrical shape of the evacuated tube, the solar tubes are able to passively track the sun throughout the day. Flat plate collectors only provide peak energy output at midday when the sun is perpendicular to the collector’s surface. 2) Air is evacuated from the 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 less effect on the efficiency of the evacuated tube collector. 3) Evacuated tube solar collectors can be used under cold temperatures when flat plate collectors have limited or no heat output. 4) Evacuated tubes are strong, lo
