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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
onthe collector system, solar water heaters can be of two
types:
Solar water heaters based on Flat plate Collectors (FPC based
SWH)Here the solar radiation is absorbed by flat plate collectors
whichconsist of an insulated outer metallic box covered on the top
with glasssheet. 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.
Flat Plate Collector based Solar Water Heaters
Solar water heaters based on Evacuated Tube Collectors (ETC
basedSWH)Here the collector is made of double layer borosilicate
glass tubesevacuated for providing insulation. The outer wall of
the inner tube iscoated with selective absorbing material. This
helps absorption of solarradiation and transfers the heat to the
water which flows through theinner tube.
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tonnes of carbon-dioxide per year.Life : 15-20 years
Approximate cost: Around Rs.22000 for a 100 litres
capacity SWHRs.110-150 per installed litre for
higher capacity systemsPayback period: 3-4 years when
electricity is
replaced
4-5 years when furnace oil isreplaced
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. Thepay back period depends on the site of
installation, utilization pattern and fuel
replaced. To offset the high initial investment for solar water
heaters, theMinistry 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.
