Thermo Siphon Systems
Solar radiation falling on the collector passes through the glass and is absorbed by the absorber consisting of fin, raisers and headers. A special selective coating on the absorber prevents escape of heat to the environment. Water contained in the raiser and headers absorb the heat from the fins and raisers and becomes less dense than the water contained in the storage tank. It rises to the top of the hot water tank, simultaneously the cold water in the tank descends to the bottom header of the collector and gets heated in the absorber ; and the cycle is repeated. After such number of cycles the entire water in storage tank becomes hot.
Forced Circulation Type : In this type of solar water heater, water is pumped from the collectors to the tank. This type of system has a greater control on temperature output and is ideal for commercial and industrial establishments where hot water requirements are high.Thermo Siphon Systems work on two principles viz,
The water from the solar tank travels into the collectors and is heated with the sun rays and returns back to the solar tank. This is called an Open Loop System. A collector without heat exchanger/close loop needs frequent de-scaling / cleaning, which results in damage of the copper tubes/absorber. Models available :
1- Pressurized Tank
2- Non pressurized Tank
The water in the heat exchanger* travels into the collectors and is heated with the sun rays and returns back to the heat exchanger. This hot water in the heat exchanger in turn heats up the water in the solar tank. This is called a ‘close loop system’ . This ‘close loop ’ technology is to ensure uninterrupted working of the solar water heating system and also to safe-guard the solar flat plate collectors from scaling due to hard water, thus enhancing the life and performance of the collectors. (say upto 15 to 20 years)..
1- Pressurized with heat exchanger
2- Non Pressurized with heat exchanger
In contrast to thermo siphon systems, an electrical pump can be used to move water through the solar cycle of a system by forced circulation. Collector and storage tank can then be installed independently, and no height difference between tank and collector is necessary.
Forced-circulation systems can be used for room heating as well as domestic water heating. In this case, collectors and storage tanks must be much larger than with simple domestic water heating systems, where a collector surface of about 4 mxm is sufficient for most households. Larger systems have also been realized successfully with two or more storage tanks.