3. What is Solar Energy?
Solar energy is, simply, energy
provided by the sun. This energy
is in the form of solar radiation,
which makes the production of
solar electricity possible.
The spectrum of Solar light at
the Earth's surface is mostly
the visible and near
infrared ranges with a small part
in the ultraviolet region.
5. Electromagnetic spectrum
Electromagnetic spectrum is a continuum of all
electromagnetic waves arranged according to
frequency and wavelength. The sun , earth and
other bodies radiate electromagnetic energy of
Electromagnetic energy passes through space at
the speed of light in the form of sinusoidal waves.
6. Solar water heating (SWH) is the conversion of
sunlight into heat for the purpose of water
heating, using a solar thermal collector.
Main power is Solar power.
Primarily no electricity is needed.
Gravity is the main driving force.
Solar Water Heater:
8. Parts of SWH
• Insulated tank
• Insulator box
• Copper pipes
• Temperature valve
9. Thermal Collector
• A solar thermal collector collects heat by absorbing sunlight. A
collector is a device that is used for capturing solar radiation. Solar
radiation is energy in the form of electromagnetic radiation from the
infrared to the ultra violate wavelengths.
• Collectors can be of a integrated form, used as both collector and
• Two types of collectors : Flat plate and Evacuated tube.
• Collectors can also have fluids. Thermal energy heats the fluid then
the heat from this fluid is transferred to the water.
11. How does a Solar Water Heater Work?
A Solar Water Heater comprises of an array of solar collectors to
collect solar energy and an insulated tank to store hot water.
The hot water with lower density moves upwards and cold water
with higher density moves down from the tank due to gravity head.
Both are connected to each other.
During the day time, water in solar collectors gets heated which
is either pumped or flown automatically on Thermosimphon
principle (propulsion energy) to the storage tank.
Hot water then stored in the tank can be used for various
13. Different types of SWH:
direct circulation system. Pumps circulate water through the
Indirect circulation. pumps circulate non freezing heat transfer fluid
through the collectors .
Integral collector storage . Works best for areas where temperature
rarely falls below freezing.
Thermosymphon systems. Where differential pressure of hot and
cold water and gravity is used.
14. Cloudy / rainy day effect:
• On cloudy days also, if it is for a day or
two, you still get warm water as water
gets heated due to diffused radiation
available in the atmosphere.
• The system, however, is either
connected to an electric geyser in the
house or an electrical back-up is
provided in the storage tank of the
system which is switched on when
water is not sufficiently hot
• So, you get hot water all the time even
on rainy days.
16. Savings :
• Solar Water Heater is proven to be actually cost
effective in the long run.
• A 100 litres capacity SWH can replace an electric
geyser for residential use and saves 1500 units of
17. Environmental benefits:
Solar thermal is one of the best ways to
lower a building's carbon footprint and help
protect the environment.
Reduced greenhouse gas emissions:
A 50-collector solar hot water system can
offset over 50 tons of CO2 per year, or 5,000
tons over the life of the system.
A 100-collector pool-heating system can
offset over 80 tons of CO2 per year.
A SWH of 100 litres capacity can prevent
emission of 1.5 tonnes of carbon- dioxide per
Simple to construct and install.
No or negligible running cost.
Low maintenance .
Cost is low and economically competitive with electric
water heating system.
It saves time and high grade form of electric energy.
Temperature up to 100C can be achieved by simple flat
•Over heating problem
•Solar thermal panels can only heat water.
•There are few parts of the system like the pump
and antifreeze which need to be checked to
ensure that they are performing optimally.