Sustainable sources of energy  
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Are the natural resources that are used in the production of electricity without  
destroying the environment.  
OR  
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Is a form of energy whose usage meets the needs of the present generation  
without compromising its ability to meet the needs of the future generations  
Types of Sources of Energy  
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Renewable sources  
Non- renewable sources  
Renewable Sources  
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These are the energy sources which can be turned into use again after being used.  
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Examples are sun  
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water  
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wind and fossils  
Non- Renewable Sources  
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These are the energy sources which cannot be turned into use again.  
For example oil  
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natural gas and charcoal  
Sustainable Sources of Energy  
This source occurs naturally and readily available, these include the following:-  
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Hydroelectric energy  
Solar energy  
Wind energy  
Sea wave energy  
Geothermal energy  
Tidal energy  
Hydroelectric Energy (water energy  
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Hydroelectricity is a form of renewable energy that uses the water stored in  
dams as well as flowing in rivers to create electricity in hydropower plants  
OR  
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Hydroelectric energy is the generation of electricity using flowing water to drive  
a turbine which powers a generator.  
Generation of Hydroelectricity  
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Hydroelectric energy is formed from the force of falling (moving) water  
The capacity of this energy depends on the available flow and the height  
from which it falls  
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When water comes from the dam which is constructed to hold water at a  
higher ground used to drive the turbine in order to generate electricity  
Uses of water energy  
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U
sed for industrial work  
Used for lighting  
Used for heating and cooking  
Used for running hospital equipment  
Advantage of Using Water Energy  
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It is a renewable form of energy  
It is Clean and safe energy  
It is reliable source of energy  
It is operated at low cost  
Electricity can be generated constantly due to constant flow of water  
Disadvantage of using water energy  
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It is expensive to construct (install)  
The huge area is required hence can affect the ecology of the area  
Much of the energy produced is wasted in form of heat during transmission  
Solar Energy  
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Solar energy is the radiant energy emitted by the sun.  
Solar energy converted by solar cells (photovoltaic or photoelectric cells).  
Solar cell is a device that converts light energy into electric current using a  
photoelectric effect  
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photoelectric effect is a property of some materials to release electrons when  
hit with rays of light known as photons  
The main surface of a solar panel (several thousand cells) is dull black to  
enhances the absorption rate of the radiant energy from the sun  
NB:  
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The sun is the ultimate source of much of the world’s energy  
It provides the earth with light, heat and radiation  
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All renewable energies ,other than geothermal energy and tidal(wave) energy,  
derive their energy from the sun  
Advantage of Solar Energy  
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It is renewable and unlimited  
It is non – polluting  
It has easy installation  
It is used for lighting purposes  
It is used for provision of electricity that is used by electric appliances  
It is used for drying clothes  
It is used for heating of water  
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It is used to power torches, cars and calculators  
It is used by spaceships and satellites to convert sunlight into electricity  
It creates jobs by employing solar panel manufacturers, solar installers etc  
Disadvantage of Solar energy  
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Lower production in the winter months  
Devices that run on DC power directly are more expensive  
No solar power at night so there is a need for a large battery bank  
It is cost for initial purchasing of a solar system  
Uses a lot of space (the more solar panel as you need)  
Wind Energy  
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Wind is simply air in motion  
Wind energy is the form of solar energy caused by the uneven heating of the  
earth’s surface by the sun  
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Wind energy can be converted into electricity by building a tall tower with a  
large propeller on top called wind mill (wind turbine).  
Wind mill is a rotating machine that converts kinetic energy of wind into  
electrical energy  
Advantage of Using Wind Energy  
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It is renewable source of energy  
It is environmental friendly  
It has low running costs  
It can provide power to remote locations  
It is free (anyone can use it and never run out)  
Disadvantage of wind energy  
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Noise: some wind turbines tend to generates a lot of noise which can be  
unpleasant  
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Wind turbines can cause death to wild animals (e.g birds, bats)  
Installation is expensive  
Sea Wave Energy  
Sea water is the form of energy caused by disturbing water particles resulting  
progressive propagation from one point to another  
Causes of Sea Wave Energy  
Sea wave energy is as a result of wind blowing across the sea  
Advantages of sea wave energy  
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It is a renewable source of energy  
It is an environment friendly  
It is abundant and widely available  
It is easily predictable  
It is operated at low costs  
Disadvantages of sea wave energy  
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It has effects on marine ecosystem  
It is a source of disturbance for private and commercial vessels  
High cost of investment  
Tidal Energy  
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A Tide refers to the rise and fall of the sea level surface  
Tidal energy refers to the energy that is created by the rise and fall of the  
earth’s sea level  
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The amount of energy that is produced is determined by how high or low the  
tide rises or falls  
Causes of Tides  
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Tides are caused by the gravitational interaction between the earth and the  
moon  
Advantages of tidal energy  
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It is renewable energy source  
It is an environmentally friendly energy source  
Tides are very predictable thus highly reliable  
Cost of running is cheap  
It does not generate any unsafe, greenhouse gases or hazardous waste  
It functions without fuel requirement ,only functions with natural tidal energy  
Disadvantages of Tidal Energy  
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It is expensive to construct  
Limited locations: Tidal energy requires specific site characteristics  
Equipment maintenance can be challenging  
Weather effects: Bad weather and storm events along coastlines can damage  
tidal energy equipment  
Geothermal Energy  
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Geothermal energy is the energy generated by the flow of heat within the  
surface of the earth  
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it is associated with area of frequent earthquakes and high volcanic activities  
The heat from the inside of the earth is used to heat water into steam. The  
steam is used to turn turbines and as the result this causes turbines to turn  
generator and produce electricity  
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Geothermal energy exists in the form of :-  
a) Volcanoes  
b) Hot Springs  
c) Geysers  
Three main uses of geothermal energy  
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Heating  
Electricity generation  
Geothermal heat pumps  
Advantages of geothermal energy  
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It is renewable source of energy  
It is environmentally friendly  
It is reliable  
It reduces reliance on fossil fuels  
It create jobs and economic benefits  
Disadvantages of geothermal energy  
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During construction it can cause earthquakes (surface instability)  
Commercial geothermal power projects are expensive  
It can sometime run out of steam  
Suited to particular region  
It may release harmful gases through the holes drilled by constructors  
Energy Cycle  
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The sun is the ultimate the source of much of the world’s energy.  
For instance, the solar cell generates electricity using light energy which has  
just arrived from the sun.  
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Energy from the sun also makes the water cycle work, It evaporates water from  
the sea and this water later falls as rain which fills up rivers and lakes in which  
hydroelectric power stations capture energy.  
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Wind is caused by the unequal heating of the earth by the sun. Wind energy  
therefore is a derivative of solar energy.  
All green plants use the energy from the sun during the process of  
photosynthesis. They store chemical energy in form of starch. So the energy  
obtained from a wood fire originally comes from the sun.  
This is similar to the fossil fuels formed hundreds of millions of years ago.  
Plants died and became compressed to form coal.  
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Class Assignment  
1. What are the advantages of utilizing tidal energy over utilizing geothermal  
energy?  
2. Describe how hydro – electric energy is generated  
3. “Though fossil fuels such as petroleum and coal are widely used, they are not  
sustainable.” Give reasons to support the statement above.  
4. Nuclear energy is not sustainable energy. Explain.  
5. What are the benefits and drawbacks of hydroelectric energy?  
6. “The sun is the ultimate source of the earth’s energy”. Explain this statement  
showing how the sun is the source of the other forms of energy  
7. What is the role of a wind turbine?  
8. ------------------------- is a form of energy that can be persistently used without  
running out  
9. Name five sources of sustainable energy  
10.State application of water energy  
11.Sea wave energy is as a result of----------------------the sea  
12.What is geothermal energy?  
13.  
A
----------is a device that converts light energy into electrical energy.  
(A)Wind mill (B) Inverter (C) Turbine (D) Solar cell  
14.A form of energy that can be persistently used without running out is said to be:  
(A)Efficient (B) Renewable (C) Environmental friendly (D) Non – Renewable  
15.Which is false?  
(a) Hydroelectric power stations are easy to set up?  
(b) Windmills are noisy?  
(c) Hydroelectric power plants degrade the environment  
(d) Windmills cannot be set up near the seabed  
16.The energy due to the rising and falling in the level of water in the oceans or  
seas is known as:  
A. electric energy  
B. Tidal energy  
C. water energy  
D. wind energy  
17.The most available sustainable sources of energy is:  
A. the sun  
B. wind  
C. Sea tides  
D. Water falls  
18.Mention three sources of thermal energy in everyday life  
19.State the energy conversion in a solar cell and give two practical uses of it.  
20.Mention three renewable sources of energy  
21.Sustainable energy sources are:  
A. Biogas, kinetic energy and petrol  
B. Biogas ,tidal energy and water energy  
C. Firewood, petrol and tidal energy  
D. Kerosene, nuclear energy and water energy  
22.Which of these resources of energy is non renewable?  
A. Wave energy  
B. Bio fuels  
C. Radiant energy  
D. Fossil fuel  
23.  
Match the items in list A with the items in List B  
List  
A
List  
B
a) Geothermal energy  
b) Solar energy  
(i) Energy from the sun  
(ii) Energy from firewood  
c) Wind energy  
(iii)Energy from coal  
d) Sea wave energy  
e) Water energy  
(iv)Hydroelectric energy  
(v) Energy from the nuclear of the atom  
(vi)Energy from hot rocks underground  
(vii)  
Energy from fossils  
(viii)  
Energy from charcoal  
(ix)Air current energy  
(x) Energy from batteries  
(xi)Tidal energy