Renewable energy sources like solar, wind, hydroelectric, and geothermal can be replenished and do not cause pollution. Solar cells convert sunlight to electricity but are currently expensive and only efficient at converting 25% of sunlight. Wind turbines use wind kinetic energy to generate electricity but require many turbines to have a large impact. Hydroelectric dams provide reliable power but can flood habitats. Geothermal energy captures underground heat to power generators. Fossil fuels like coal, oil and gas are non-renewable and produce greenhouse gases and other pollution when burned. Nuclear power produces no emissions but creates radioactive waste that remains dangerous for thousands of years.

1. Unit-4
Sub :
Environmental Studies
Topic : Renewable and Non Renewable Energy Sources

2. Renewable Energy
• Renewable energy resources can be replaced or regenerated
and will never run out (at least not for a very long time).
• Examples: wind and solar.
 Solar Power
 Wind Power
 Water Power
 Thermal power

3. Solar cells
• Solar cells (or photocells) turn light energy from
the Sun directly into direct current electricity.
• Manufacturing solar cells is very expensive and
requires the use of highly toxic materials.
However, once the solar cell is built it produces
no pollution and requires little maintenance.
• This makes solar cells ideal for use in remote
locations where maintenance is difficult and
other sources of electricity would be expensive.

4. Solar cells suffer from a low efficiency. This is because only light with enough energy
causes an electron to be released which is only about 25% of all sunlight.
The amount of electricity a solar panel can produce depends on two factors: its surface
area and the light intensity.
Producing enough electricity to
power a town would require a
very large area of solar panels
but covering the roof of a house
can meet the annual electricity
needs of the household.
Efficiency of a solar cell
1

5. One obvious problem with solar cells is that they do not produce electricity at night.
If more electricity is produced during the day than is used, the excess can be used to
charge a battery which can then provide power during the night.
Scientists are working to develop
improved solar cells which
require less polluting chemicals in
their manufacture, cost less to
produce and are more efficient
than the current technology.
Problems with solar cells
© Warren Gretz/NREL
2

6. Solar cells can be used very effectively in the right
situation.
Effective use of solar cells
Solar cells are very useful for remote
locations where supplying mains electricity
would be expensive.
This solar-powered street light is in a remote
part of mid-Wales with no mains electricity
supply close by.
The use of solar power in this way removes
the need to lay electricity cables to the light,
which is another benefit to the environment.
3

7. Effective use of solar cells
Solar cells are very useful where the
light intensity is highest.
These solar panels are in a remote
part of Morocco where they are used
by a local utility company.
Solar cells are also useful where low amounts
of power are needed.
Calculators only require a small amount of
electricity, so most calculators now use solar
cells
in place of batteries .
© Courtesy of BP Solarex/NREL
4

8. Using the wind as a source of energy is
not a new idea.
Sailing ships, powered by the wind, have
been around for thousands of years.
Windmills which used the wind’s power
to grind corn were once a common
landmark across Britain.
Wind power
5

9. Wind turbines (or aero-generators) use
large blades to capture the kinetic energy of
the wind. This kinetic energy is used to
directly turn a turbine and produce
electricity.
Wind turbines do not produce any polluting
waste, however, some people consider
them to be an noisy and an eyesore. There
is also concern that, if poorly located, they
could kill migrating birds.
Wind turbines
6

10. One problem with wind turbines is that individually they
do not generate a lot of electricity. They are usually
needed in large numbers to have an impact on electricity
production. A group of wind turbines is called a wind
farm.
Wind farms require large amounts of space in
open areas, but the land can also be used for
farming at the same time.
Offshore wind farms are located at sea. This
wind farm is located 10 kilometres from the
Wind farms
south-east coast of Ireland.
© Robert Thresher/NREL
7

11. The energy produced by a wind turbine depends on the wind speed. If it is not windy,
electricity is not produced, so wind turbines are not a reliable source of electricity.
Wind power can be used effectively in remote locations to charge batteries which can
then be used to provide a constant supply of electricity.
To be effective, wind turbines need to be
located in windy areas. Unfortunately, these
are usually upland areas of natural beauty
and some people object to the building of
wind farms in these areas.
Effective use of wind turbines
8

12. The power of flowing water has been used for hundreds of years to operate
machinery. This power can also be used to generate electricity.
Water power 1: hydroelectric power
9

13. Large scale hydroelectric schemes
involve building a dam across the end
of a river valley to create a reservoir.
This is done high up in a mountainous
area.
Hydroelectric power stations are able
to start up electricity production
quickly.
Hydroelectric power is also very
reliable.
Hydroelectric power
10

14. Hydroelectric power stations need to be
situated in high mountainous areas such as
North Wales or Scotland.
Damming the river causes the river valley
to flood which could mean that houses and
villages are destroyed.
Hydroelectric power schemes also cost a lot of money and take a long time to build.
However, they do last a long time and they are able to produce large amounts of
electricity.
Once they are built, hydroelectric schemes provide a cheap and reliable source of
electricity.
Effective use of hydroelectric power
11

15. The rise and fall of waves is a renewable
source of energy. Effective sites for
harnessing wave energy need to have strong
waves most of the time, to ensure that
enough electricity will be produced.
The “Limpet” (land-installed marine-powered
energy transformer) on Islay, Scotland, is the
world’s first commercial wave energy device.
Its low profile is designed so that it does not
effect coastal views.
Water power 2: wave power
12

16. Tidal power involves building a dam
across a river estuary.
Water can only flow in and out of the
estuary through turbines in the dam,
which harness the tidal energy.
When a tidal barrage is built, it results in some of the estuary being flooded. This can
mean the loss of important habits for wading birds.
Water power 3: tidal power
Tidal power is able to provide a lot of electricity, however building a tidal barrage is
very expensive.
13

17. Tidal power provides a regular source of electricity. Exactly when this electricity will be
produced is governed by the tides, which depend on the Moon.
The passage of ships past the tidal
barrier and the effect on wildlife also
complicate the construction of tidal
barrage schemes.
Effective use of tidal power
Monthly variations in the tidal range
will also affect how much electricity
can be produced.
14

18. In rocks under the ground, radioactive decay
of elements, such as uranium, releases heat
energy that warm the rocks.
In some areas, hot water and steam rise to the
surface.
The steam and hot water which rises
naturally to the surface can be harnessed to
generate electricity.
The largest geothermal power plant is in
California and has an output of 750
megawatts.
Geothermal energy
© Joel Renner - DOE/NREL
© David Parsons/NREL
15

19. Geothermal energy
In some areas, the warm rocks are very deep underground.
This geothermal power plant in
California has
57 wells and produces 52 MW of
electricity.
Where this occurs, wells are drilled
down to the hot rocks and cold
water is pumped down. The water
is heated by the rocks and returns
to the surface as steam.
© Warren Gretz/NREL
16

20. Non Renewable Energy Sources
Non-renewable energy resources will eventually run out – once used they cannot
be used again.
Examples: coal and oil.
16

21. What are fossil fuels?
Industrial societies need a lot of energy and, at
the moment, rely on fossil fuels as the main
source of this energy.
Coal, oil and natural gas are fossil fuels. They are
carbon-based materials that formed over millions
of years from the remains of ancient plants and
animals.
Fossil fuels are so useful because they contain
stored chemical energy, which is converted into
large amounts of useful heat energy when the
fuels are burned.
The total amount of fossil fuels available is limited
and so they are classed as non-renewable energy
resources. 17

22. What waste do fossil fuels produce?
Burning fossil fuels creates waste products that can act
as pollutants and have harmful environmental effects.
Carbon dioxide – This greenhouse gas is the main waste
product of burning fossil fuels. Increased levels of
carbon dioxide due to human activities are thought to
be connected with global warming.
Sulfur dioxide and nitric oxides – These gaseous
pollutants contribute to the formation of smog and acid
rain.
Ash – This waste solid is disposed of in landfill sites.
What can be done to reduce the problems caused by
burning fossil fuels?
18

23. Nuclear fuel is used to generate electricity but,
unlike fossil fuels, it does not burn.
In a nuclear fuel, such as uranium, reactions
take place that split the atoms and release
huge amounts of heat energy.
This is called nuclear fission.
In a nuclear power station, the heat released
from nuclear fission reactions is used to
change water into steam. As in other types of
power station, the steam then turns a turbine,
which turns a generator and produces
electricity.
Nuclear power stations do not release any
greenhouse gases such as carbon dioxide or
gases which cause acid rain.
What is nuclear fuel?
19

24. What waste does nuclear power produce?
Nuclear power stations produce radioactive waste.
The used nuclear fuel contains some uranium, which can be separated from the
waste and reused.
It also contains plutonium, which is a highly-radioactive product of the fission
reactions that occur in uranium nuclear fuel.
New reactors that use this waste product as a fuel have been built.
However, plutonium is also used in the construction of
nuclear bombs and poses a very serious threat if it
gets into the wrong hands.
20

25. Nuclear waste that cannot be reused poses serious problems as it can remain radioactive
for thousands of years.
Highly radioactive waste can be turned into glass to help stabilize it and prevent leaks
during storage.
One solution is to bury the waste deep underground.
This must be in a geologically stable environment, so there are few suitable sites.
Another suggested solution is to dump radioactive waste at the bottom of the sea. Dealing
with nuclear waste is expensive and any solution has to be long term.
Where can nuclear waste be stored?
21

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28. Book/Web Resources
Environment & Ecology by Dr Gourkrishna Dasmohapatra

29. Thank You