Renewable and non-renewable energy sources are discussed. Renewable sources include solar, wind, hydroelectric, geothermal and tidal power. Solar cells convert sunlight to electricity but have low efficiency. Wind turbines capture kinetic energy from wind to generate electricity. Hydroelectric dams produce large amounts of power but require specific locations. Fossil fuels like coal and oil are non-renewable and produce pollution when burned, though they currently provide most energy. Nuclear power is a non-renewable source that does not pollute when generating electricity but produces radioactive waste.

1. Unit-4
Environmental Science
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
south-east coast of Ireland
Wind farms
.
© 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