99600c1d_Collector___Solar_Water_Heater__Evacuated_Tube_Collector
[S.No] 16 [Flat Plate Collector] Difficult and expensive to replace glass sheet [Evacuated Tube Collector] 
It is very easy to replace glass tube.
Comparison between Evacuated Tube Collector & Flat Plate Collector - Solar Water Heater
Evacuated Tube Collector