Normally Solar systems are working up to 0.8 Kg / Cm2 , The storage tank is placed at a certain height relative to the top of the collector to prevent the reverse circulation during off-sun shine hours. In this system, hot water storage tank can be under normal pressure of cold water overhead tank so gravitational force of overhead cold water tank comes to bottom of hot water tank at normal pressure, hot water comes out from top of hot water solar tank and release at the end of tap as a regular.


  1. High Density Galvanise Tank
  2. PUF Insulation
  3. Inside Marine Coating
  4. Galvanise Sheet Stand
  5. High Thick G.I Base and Leg
  6. Heavy G.I Nipples


  1. Higher temperature  than FPC System
  2. Thick tank Gives More Strength
  3. Quick result in rainy and cloudy atmosphere
  4. Easy to get temperature in hard water
  5. No need to service for long time


  1. Household water heating
  2. Textiles
  3. Hotel,Restaurants and resorts
  4. Hospital
  5. Hostel
  6. Boiler Feed water preheating
  7. Apartments
  8. Industrial and Commercial
Technical Specifications:
Material Borosilicate 3.3 glass
Outer Diameter  58mm
Inner tube diameter  47mm / 54mm
(whatever applicable)
Tube Length 1800mm /2100mm (whatever applicable)
Absorptive coating Graded AL-N/AL
Vacuum <5*10-3 Pa
Absorptance >92%(Am1.5)
Glass thickness 1.6mm
Emittance <8%(80 oC)
Thermal expansion 3.3*10-6 oC
Stagnation temperature >200 oC
Heat loss <0.8 w / sqm
Maximum strength 0.8 MPa



Evacuated Tube Collector Solar Water Heaters

Working Principle of Evacuated Tube Collector (ETC) System:
Solar Glass Tube Water Heater working Alfa Solar Water Heater (ETC System) works on a simple principle ‘Black body heat absorption principle’. The principle says, ‘black colour absorbs maximum heat, more than any other colour’.

Solar water heating systems using vacuum tubes made of borosilicate glass with special coating to absorb the solar energy are called as Evacuated Tube Collector system (ETC Systems).

Vacuum tube, as shown in the sketch, is the main component, which absorbs solar energy. The vacuum tube is an assembly of two concentric, borosilicate glass tubes.

Solar Evacuated Tube Collector Working Air between the gap of two glass tubes is evacuated. It results in high level of vacuum, which acts as the best insulation to minimize the heat loss from inner tube. The black coating on the inner tube absorbs the solar energy and transfers it to the water. The water on upper side of Vacuum Tube becomes hot and thus lighter, so it starts moving upwards in the tank. At the same time cold water, which is heavy, comes downward from the tank and is stored at the bottom. The phenomenon is called as natural Thermo syphon circulation, which occurs in every tube.