How does the ISL flat plate collector compare to evacuated tubes?
There is a lot of conflicting information available about the relative performance of flat plate and evacuated tubes. For example comparing evacuated tubes to unglazed flat plate collectors or those with non selective absorbers, or comparing at temperatures which are not representative of normal domestic hot water usage. This has led some people to believe that a much lower area of solar collectors are required to be used for evacuated tubes, which is simply not the case. The truth is that there are good solar collectors and bad solar collectors and many good flat plate collectors perform better than poor evacuated tubes for a given collector area. Also a lot depends on the design of rest of the solar system, such as the pump energy consumption, control system and hot water cylinder. We believe that the ISL solar system is one of the better flat plate systems, having a low water volume panel, a selective absorber surface, a low wattage pump. Therefore until more conclusive test data is
