Given the different construction of flat plate and evacuated tube solar collectors, it's reasonable
to ask which type is better. There is no simple answer to this question. The solar collector with the greatest
heat collection potential depends strongly on the specific application in which the collector will be used.
Beyond thermal performance, the designer must also weigh factors such as differences in roof area
requirements, maintenance requirements, ability to shed snow and the type of freeze protection options
available for each type of collector.
From the standpoint of thermal performance only, the collector with the best performance depends on the
temperature requred by the load the system supplies. This is demonstrated by comparing the three solar collector
efficiency lines shown on the following graph.
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