Evacuated Tube Collector Solar Water Heaters

Solar Water Heater is a device which produces hot water for bathing, washing, cleaning, etc. using sunlight during sunny days. It is generally installed at the terrace or where sunlight is available and heats water during daytime which is stored in an insulated storage tank for use when required including mornings.

Solar water heater with capacity 150 ltr per day.

Working Principle of Evacuated Tube Collector (ETC) System :

Solar Water Heater Glass Tube Type workingRedsun 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 Water Heater Evacuated Tube Collector WorkingAir 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 Thermosyphon circulation, which occurs in every tube.

Thermosyphon Systems : In this type water flows through the system and when water gets warm it rises as cooler water sinks. The collector is installed below the storage tank so that warm water will rise into the tank. These systems do not involve any pump and are more reliable.

Solar Water Heaters have several advantages over conventional water heating systems as they :

  • Reduce electricity bills: 40% of an average household’s energy bill comes from water heating.
  • Save interior space: These systems are usually located on rooftops.
    Increase safety: Solar water heaters eliminate the risk of accidents in bathrooms due to electric water heating equipment.
  • Quick payback: On average, a good quality solar water heater will have a payback period of 1½ – 2 years in Indian conditions.
  • Protect the environment: In today’s environment conscious world, you can make a difference by getting your hot water free from the sun. By replacing an electric water heater with a solar water heater, you can reduce greenhouse gas emissions by up to 3 and 4 tonnes a year – the equivalent of taking a small car off the road.

REDSUN Evacuated Tube Collector Solar Water Heater Features:

  • High quality tubes made from borosilicate glass
  • No clogging/choking
  • Long lasting
  • Better performance in winter and cloudy days
  • Inner glass tube is coated with the world best magnetron sputtering Hi-Tech, layers of AL – N with AL base
  • Vacuum jacket insulation
  • Heats water to a very high temperature
  • Makes hot water available even on partially cloudy days
  • High quality PUF insulation for maintaining high temperature of water inside the tank
  • Compact
  • Easy to install, operate and maintain
  • Works efficiently with hard water
  • Galvanized Iron tank for hot water storage
  • Powder coated GI stand
  • Safe and environment friendly

Specifications of Evacuated Glass Tubes:

Material of GlassBorosilicate Glass
Length1800 mm and 2100 mm
Outer diameter58 mm
Inner diameter47 mm
Thickness of Glass TubeOuter tube thickness: 1.8 mm, inner tube thickness: 1.6 mm
Selective coating typeAIN/AIN-SS/CU – Sputtering
Value of absorptance and emittance of the black coatingAbsorptance: α ≥ 93.5%, Emission rate: ε ≤ 5%
Vacuum rateP ≤ 5.0×10-4Pa
Recommended operating pressure0.2 Kg/sq. cm.
Stagnation ParameterY ≥ 290 M² °C/KW
Coefficient of Thermal Expansion3.3×10-6/k