Why are tube collectors more efficient than flat plates?
When comparing the best efficiency levels it may seem that there is little difference between flat plate and evacuated tubes, but when efficiency is averaged over a year evacuated tube collectors have a clear advantage when collecting radiation. 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. The high efficiency of evacuated tubes absorption of solar radiation, means that even on cloudy and overcast days, energy producing savings can be generated. This in turn means energy can be collected for longer periods and across all seasons. Additional advantages of evacuated tube collector over flat plate collectors, means a smaller array of collector can be used to provide the same performance. Evacuated tubes are strong, long lasting, and should one be broken or damaged, are inexpensive and easy to
