What is the difference between flat plate collectors and evacuated tubes?
Flat plate thermal solar collectors have been in use for several decades, but only in relatively small numbers, particularly in Western countries. Evacuated tubes have also been in use for more than 20 years, but have been much more expensive than flat plate, and therefore only chosen for high temperature applications or by those who could afford their high price. In recent years the production volume of evacuated tubes has exploded, resulting in greatly lower manufacturing and material costs. The result is that evacuated tubes are now similar in price to flat plate, but with the insulating benefits of the evacuated tube, they are set to become the default choice for thermal solar applications worldwide. When comparing peak efficiency levels it may seem that there is little difference between flat plate and evacuated tubes, and in fact flat plate may actually be higher, but this is during minimal heat loss conditions. When averaged over a year, evacuated tube collectors have a clear ad
