| 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 60 deg. to 120 deg. |
Temperature range from 50 deg. to 60 deg. only |
| 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 44mm). 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 |
Advanced technology at competitive prices
that is System Cost per unit water is low. |
Old technology at higher prices |
| 13 |
Hot water availability for 350 days in a
year. |
Hot water availability for 300 days in a year
claimed. |
| 14 |
System life above 15 years |
System life approximately 10 years. |
| 15 |
It is very easy to replace glass tube. |
Difficult and expensive to replace glass
sheet |
| 16 |
Water quality does not affect the system. |
Water quality affect’s the system.
Scaling takes place around the metal tube. |
| 17 |
It is a low maintenance solution |
It requires high maintenance. |
