Solar water heaters based on Evacuated Tube Collectors (ETC based SWH)

Here the 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.

Solar water heating is now a mature technology. Wide spread utilization of solar water heaters can reduce a significant portion of the conventional energy being used for heating water in homes, factories and other commercial & institutional establishments. Internationally the market for solar water heaters has expanded significantly during the last decade. It is estimated that over 107 million sq.m. of collector area has so far been installed world wide for heating water. In the country, the collector area so far installed for water heating is over 1.00 million sq.m. Ministry has plans to add another 1.00 million sq. m. in next two years.

Solar Water Heaters

• Hot water at 60-80 C for hotels, hospitals, restaurants, dairies, homes, industry etc.
• Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application.
• Larger systems can be used in restaurants, canteens, guest houses, hotels, hospitals etc.

Fuel Savings:
A 100 litres capacity SWH can replace an electric geyser for residential use and saves 1500 units of electricity annually.

Avoided utility cost on generation
The use of 1000 SWHs of 100 litres capacity each can contribute to a peak load shaving of 1 MW.

Environmental benefits
A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon-dioxide per year.

Life : 15-20 years

Approximate cost: 
Around Rs.22000 for a 100 litres capacity SWH
Rs.110-150 per installed litre for higher capacity systems

Payback period:
3-4 years when electricity is replaced
4-5 years when furnace oil is replaced
6-7 years when coal is replaced

Though the initial investment for a solar water heater is high compared to available conventional alternatives, the return on investment has become increasingly attractive with the increase in prices of conventional energy. The pay back period depends on the site of installation, utilization pattern and fuel replaced. To offset the high initial investment for solar water heaters, the Ministry is currently implementing a soft loan scheme through seven designated banks and Indian Renewable Energy Development Agency (IREDA), which has now been extended to all kind of Financial Institutions.