Solar Water Heating : FPC(Flat Plate Collector) and ETC (Evacuated Tube Collector)

The choice of an FPC or ETC type of solar water heater depends upon the location, seasons and other external factors.
In general, FPC type solar water heaters have better performance in hot climatic conditions whereas ETC type solar water heaters perform better in cold climatic conditions. A detailed comparison between the two technologies in the context of providing domestic water heating is as below:

Criteria: Comparison between FPC & ETC type Solar Water Heaters

Heat generation: ETC has better heat generation in colder climates and under cloudy/low sunlight conditions

Heat insulation: ETC has lower heat loss at night as the vacuum inside the tubes offers better insulation

Pressure endurance: In case of non-pressurized systems, FPC can withstand higher pressure compared to ETC

Water hardness: In case of non-heat exchanger type systems, scaling due to hard water leads to a higher loss in efficiency in case of FPC compared to ETC

Durability: FPC systems can last for 15 years or more without major maintenance whereas ETC systems can last for 5 years or more without major maintenance.

Operations & Maintenance: • The tubes in case of ETC are prone to breakage and in case of breakage of one of the tubes the entire system gets drained and hence is not usable. However, the cost of replacement in case of ETC is lower as the broken tube can be replaced whereas in case of FPC the entire glass needs to be replaced
• Corrosion is not an issue in case of ETC as it is made of glass
• ETC systems cannot be exposed to solar radiation when there is no water inside the tubes as thermal shock could lead to cracking of the tubes