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Salient Features of Solar Water Heating
System: A solar water heater consists
of a collector to collect solar energy and an insulated storage tank to
store hot water. Based on the collector system, solar water heaters can
be of two types:
Solar water heaters based
on Flat plate Collectors (FPC based SWH): 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.
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 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.
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Solar Water Heaters
- Hot water at
60-80C for hostels , hospitals, restaurants, dairies, homes, industry
etc.
- Solar water
heaters (SWHs) of 100-300 liters capacity are suited for domestic
application.
- Larger systems
can be used in restaurants , canteens , guest houses, (SWHs)
Fuel Savings: A 100 liters capacity SWHs
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
liters capacity each can contribute to a peak load shaving of 1 MW.
Environmental benefits : A SWH of 100 liters capacity
can prevent emission of 1.5 tones of carbon – dioxide per year.
Life: 15-20 years
Approximate cost:
- Around Rs. 22000 for a 100 liters capacity SWHs Rs. 110-150
- Installed liter 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.
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