Solar Water Heater

A Solar Water Heater utilizes heat energy of Sun Rays (solar energy) to increase temperature of water and stores this heated water in an insulated tank, for use throughout the day. The capacity or rating of solar water heaters is defined by amount of water that it can warm – LPD – liters per day. Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application i.e. a family of 4-10 members.

A Solar water heater system includes mainly 3 parts:

  • Collector – which raises temperature of water
  • Storage Tank – which stores this heated water
  • Water Pipelines connecting the different parts.

Based on the collector system, solar water heaters can be of two types. One with Flat plate collectors (FPC) and the other with Evacuated tube collectors(ETC).

solar water heater

Flat Plate Collectors (FPC) based Solar Water Heaters

The solar radiation is absorbed by Flat Plate Collectors which consist of an insulated outer metallic box covered on the top with glass sheet. Inside there are blackened metallic absorber (selectively coated) sheets with built in channels or riser tubes to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water. There are 60 BIS approved manufacturers of Solar Flat Plate Collectors.

Evacuated Tube Collectors (ETC) based Solar Water Heaters

Evacuated Tube Collector is made of double layer borosilicate glass tubes evacuated for providing insulation. The outer wall of the inner tube is coated with selective absorbing material. This helps absorption of solar radiation and transfers the heat to the water which flows through the inner tube. There are 44 MNRE approved ETC based solar water heating suppliers.


FPC based systems are of metallic type and have longer life as compared to ETC based system where tubes are made of glass which are of fragile in nature. ETC based systems are, therefore, cheaper than FPC based system.

The choice of system depends on heat requirement, weather conditions, heat transfer fluid quality, space availability, annual solar radiation, etc. The SHW systems are economical, pollution free and easy for operation in warm countries like ours.

Costs Comparison of FPC & ETC Solar Water Heater:



Applications of Solar Water Heaters:

  • Domestic:
    • Residential Bungalows Residential Flats & Apartments Staff Quarters
    • Hostels & Canteens
    • Hospitals
  • Business:
    • Hotels, Clubs & Resorts
    • Spa & Salons
    • Milk Dairies
    • Heated Swimming Pools
  • Industrial Applications
    • Pre-Heating of Boiler Feed Water Chemical & Pharmaceutical Industry Recirculation of Hot Water in Process Textile Industry
    • Paper Industry Laundry

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