By gravity flow, water from the cold-water tank enters the solar tank at point through cold water inlet and fills it up. The cold water from the solar tank in turn flows in the bottom header pipe of the absorber, and into the copper tubes, until all the absorber tubes and the header at the top of the absorber are full.

When the sun rises to a certain level, its energy, which falls on the absorber fins and tubes, begins heating the water contained therein. The heated water being lighter than the cold water rises and via the top header pipe of the absorber, flows into the top of the solar tank through pipe. The quantity of hot water entered in to the solar tank, same quantity of cold water from the solar tank flows into the absorber tubes, gets heated and rises to the top, and so on. This process is called ‘Thermo-syphon Process’ and this Thermo-syphon Process continues until the temperature of the water in the solar tank and the absorber equalizes. Now the solar tank is full of hot water. Average temperature is 60 degree centigrade at the end of bright sunshine day.

Further when the hot water is drawn from the solar tank outlet to the utilities point, cold water enters into the solar tank and takes its place, thus lowering the overall temperature of the hot temperature between the water in the solar tank and the absorber tubes, the thermosyphon process starts once again, as explained earlier.

A back up electrical heater (to be used during cloudy days) and the sacrificial anode rod in the solar tank to prevent galvanic corrosion (but not scale formation), if the hardness of the water quality is less than 140 ppm, thereby ensuring effective working for longer time.

Solar Water Heaters are available in Three models and capacity ranging from 100 LPD to 1,00,000LPD

1. Regular or Basic System: is as explained above
   
   
2. Heat Exchanger System : This type of Solar water heating system used when the original cold water (from the source) contains chemical contents and is therefore hard water.
   Thermal fluid (Distilled water) is filled thro make-up tank to the outer tank shell. In turn, this fluid gets circulated thro the solar fins and tubes and goes back into the top of the outer tank. This fluid acts as a heat transfer media and prevents clogging of the copper tubes due to chemical contents in the original water source. The inner tank gets filled with cold water from the original cold water source. Since the inner tank is immersed within the outer tank, the heat gets transferred to the inner tank through the conducted and convection method and the water in the inner tank gets heated up and available for hot water utility.
   
   
3. Pressurized System : A pressure pump is used to pump cold water from the source into the Solar tank. This type of water heating system is used when :
   The level of the overhead tank (The original cold water source) is at low level.
   -High pressure hot water flow is required for various uses like shower panels, jet shower, telephone shower, etc.
   -The number of hot water points are more than normal.

TECHNICAL SPECIFICATIONS OF REGULAR SOLAR WATER HEATING SYSTEMS