S.No | Evacuated Tube Collector | Flat Plate Collector |
1 | Quick heat generation | Slow heat generation |
2 | Collector efficiency on higher temperature is high | Collector efficiency on higher temperature is low. |
3 | Heat loss in the tubes during the daytime is negligible (evacuated tubes) | Heat loss in the collector & tank during the day-time is high due to convection. |
4 | Convection and Convecting losses is low. | Convection and Convecting losses is high. |
5 | Emissivity is low. | Emissivity is high. |
6 | Satisfactory performance even in extreme cold condition (-18 deg. C) | Freezing of water will take place at high altitude causing damage to the collector. |
7 | Temperature range from 60deg. to 120 deg. | Temperature range from 60 deg. to 80 deg. |
8 | System hot water tank only is insulated using polyurethane insulation material which does not absorb water or moisture | Collector & tank insulated with glasswool/ rockwool, absorbs moisture & gets wet during monsoons reducing the efficiency of the system |
9 | Negligible scaling of tubes which can be cleaned manually (inner tube dia. Is 37mm). Loss of efficiency consequently is minimal | Heavy scaling of the copper/aluminum tubes which cannot be cleaned manually as the bore dia. is 12.50 mm. giving rise to substantial loss in efficiency of the system. |
10 | The collector glass tube absorbers being cylindrical the incident sun’s rays on the tubes is at 90 degrees throughout the day. Hence peak heat absorption always. | The collector fins & tubes being flat the incident sun’s rays will be at 90 degrees at noon only for peak absorption |
11 | In locations with average availability of solar energy over-sizing of the system glass tube collectors is not required. | Higher system sizing is required to get the desired result. Hence added cost. |
12 | Heat exchanger not required | Heat exchanger required |
13 | Advanced technology at competitive prices that is System Cost per unit water is low. | Old technology at higher prices |
14 | Hot water availability for 350 days in a year. | Hot water availability for 300 days in a year claimed. |
15 | System life above 15 years. | System life above 15 years |
16 | It is very easy to replace glass tube. | Difficult and expensive to replace glass sheet |
17 | Water quality is not effect the system. | Water quality effect the heating system forming scale over metal tube. |
18 | It has low maintenance | Its required high maintenance. |
19 | Grouting of Collectors not required. | Grouting of collectors are required. |