Solar Water Heating Systems Solar water heater suppliers in kerala, Solar Water Heater suppliers in Ernakulam
We
are blessed with Solar Energy in abundance at no cost. The solar radiation
incident on the surface of the earth can be conveniently utilized for the
benefit of human society. One of the popular devices that utilize the solar energy is solar hot water system (SHWS). Solar water heating system is a device
that uses solar energy to heat water for domestic, commercial, and industrial
needs.
Working
of a solar water heater
The system is generally
installed on the roof or open ground, with the collectors are glazed on the sun
facing side to allow solar radiation to come and connected to a continuous
water supply. A black absorbing surface (absorber) inside the flat plate
collectors absorbs solar radiation and transfers the energy to water flowing
through it. Heated water is collected in the tank which is insulated to prevent
heat loss. Circulation of water from the tank through the collectors and back
to the tank continues automatically due to density difference between hot and
cold water (thermosyphon effect).Water flows through the tubes, absorbs solar heat and becomes hot. The heated water is stored in a tank for further use. The
water stored in the tank remains hot overnight as the storage tank is insulated
and heat losses are small.
Parts
of the Solar Water Heating System
A solar water heating system consists of a solar collector,
a storage tank kept at a height
behind the collector, and pipelines.
The collector usually comprises copper tubes welded to copper sheets (both
coated with a highly absorbing black coating) with a toughened glass sheet on
top and insulating material at the back. The entire assembly is placed in a
flat box.
Storage
Tanks
Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an
additional outlet and inlet connected to and from the collector. In two-tank systems,
the solar water heater preheats water before it enters the conventional water
heater. In one-tank systems, the back-up heater is combined with the solar
storage in one tank.
Solar
Collectors
Three types of solar
collectors are used for residential applications:
Flat-plate
collector: It is the heart of a solar water heating system. It
consists of an absorber plate which is coated on its sun facing surface with an
absorbent coating, also called selective coating. The absorber consists of a
grid of metallic tubes and sheets. Water flows through the tubes. Sheet absorbs
the solar radiation falling on it and transfers it to water. The absorber plate
is placed in a top open box to protect it from weather. The space between back
and sides of the absorber and the box is filled with insulation to reduce heat
losses. The front of the box is covered with a high transmittance glass plate.
Flat plate collectors are the most common type used in the domestic solar water heating systems in India as they are relatively cheaper when compared to
others.
Glazed
flat-plate collectors are insulated, weatherproofed boxes that
contain a dark absorber plate under one or more glass or plastic (polymer)
covers. Unglazed flat-plate collectors
typically used for solar pool heating -- have a dark absorber plate, made of
metal or polymer, without a cover or enclosure.
Integral
collector-storage systems: Also known as ICS or batch
systems, they feature one or more black tanks or tubes in an insulated, glazed
box. Cold water first passes through the solar collector, which preheats the
water. The water then continues on to the conventional backup water heater,
providing a reliable source of hot water. They should be installed only in
mild-freeze climates because the outdoor pipes could freeze in severe, cold
weather.
Evacuated-tube
solar collectors: Evacuated Tube Collector is made of
parallel rows of transparent borosilicate glass tubes evacuated for providing
insulation. Each tube contains a glass outer tube and metal absorber tube attached
to a fin. The fin's coating helps absorption of solar radiation and transfers
the heat to the water which flows through the inner tube.
Types
of Solar water heating systems
Solar water heating systems are of two categories: They are Indirect/closed loop system and
Direct/open loop system.
Indirect/Closed
Loop System: Here the heat exchangers are installed
to protect the system from hard water obtained from bore wells or from freezing
temperatures in the cold regions. After collecting heat in the panels, the heat
transfer fluid flows through a heat exchanger, transferring its heat to the
potable hot water. When the panels are cooler than the storage tank or when the
storage tank has already reached its maximum temperature, the controller in
closed-loop systems stops the circulation pumps.
Direct/open
loop system: The basic solar thermal models are the
direct-gain type, in which the potable water is directly sent into the
collector. Many such systems are said to use integrated collector storage
(ICS), as direct-gain systems typically have storage integrated within the
collector. Heating water directly is inherently more efficient than heating it
indirectly via heat exchangers, but such systems offer very limited freeze
protection (if any), can easily heat water to temperatures unsafe for domestic
use, and ICS systems suffer from severe heat loss on cold nights and cold,
cloudy days.
Features
of Solar Water Heating System
·
Solar Hot Water System turns cold water
into hot water with the help of sun’s rays.SWH provides hot water for homes,
hostels, hotels, hospitals, restaurants, dairies, industries etc.
·
Can be installed on roof-tops, building
terrace and open ground where there is no shading, south orientation of
collectors and over-head tank above SWH system.
·
SWH system generates hot water on clear
sunny days (maximum), partially clouded (moderate) but not in rainy or heavy
overcast day. Only soft and potable water can be used.
·
Stainless Steel is used for small tanks
whereas Mild Steel tanks with anticorrosion coating inside are used for large tanks.
·
Solar water heaters (SWHs) of 100-300
litres capacity are suited for domestic application. Larger systems can also be
used for a variety of industrial applications.
·
Around 60 deg. – 80 deg. C temperatures
can be attained depending on solar radiation, weather conditions and solar
collector system efficiency.
·
Fuel Savings: A 100 liters capacity SWH
can replace an electric geyser for residential use and saves 1500 units of
electricity annually.
·
Saves cost on power generation: The use
of 1000 SWHs of 100 litres capacity each can contribute to a peak load saving
of 1 MW.
·
Environmental benefits: A SWH of 100
liters capacity can prevent emission of 1.5 tonnes of carbon dioxide per year.
·
Life: SWHs have a life span of 15-20
years.
·
Approximate cost: Rs.15000- 20,000 for a
100 litres capacity system and 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 5-6 years when
coal is replaced. The payback period depends on the site of installation,
utilization pattern and fuel replaced.
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