1. Lesson 8: Generating electricity
What you need to know:
1. Different energy sources can be used to generate electricity.
2. There are different types of power stations.
3. How to use a Sankey diagram.
Electricity is a secondary energy source, this is an energy source which does not
exist in nature but is produced from a primary energy source such as fossil fuels.
There are a number of primary energy sources that can be used to generate
electricity:
 Fossil fuels: Coal and gas are examples of fossil fuels, but they will
eventually run out. When a fossil fuel is burned in a power station it will
release carbon dioxide (CO2) into the atmosphere, adding to the problem
of global warming.
 Nuclear fuel: Uranium is used as fuel in nuclear power stations. Nuclear
power stations do not produce CO 2 but do produce nuclear waste, which is
very dangerous.
 Renewable energy sources: Solar, wind, tidal and geothermal power
can be used to generate electricity. These sources will never run out and
do not produce CO2.
In your exam you may be asked to identify different primary energy sources that
can be used to generate electricity.
There are advantages and disadvantages of using these different primary energy
sources to produce electricity.
Energy source Advantages Disadvantages
Coal  Coal is cheap and easy to  Produces lots of CO2 which
obtain. contributes to global
warming.
 High efficiency
 Produces acid rain.
 High power output.
 Need to mine coal, which
 Cheap electricity. can damage the
environment.
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2.  Technology is easily  Some countries need to
available to build coal import coal, meaning they
fuelled power stations. are reliant on other
countries. This means they
are not secure for their
energy generation.
 Coal will eventually run
out.
Gas  Efficient at producing  Produces CO2 which
electricity. contributes to global
warming.
 Cheap electricity.
 Difficult to transport.
 Technology is easily
available to build coal  Some countries need to
fuelled power stations. import gas, meaning they
are reliant on other
countries. This means they
are not secure for their
energy generation.
 Gas will eventually run out.
Nuclear  Very cheap electricity.  Produces nuclear waste.
 Low levels of CO2  Building and
produced. decommissioning power
stations is difficult and
 Very high efficiency. costs are high.
Solar power  No CO2 produced.  Low efficiency.
 Easy to build power  Small amounts of
stations. electricity produced.
 Source not constant.
Wind  No CO2 produced.  Need lots of turbines to
produce electricity.
 Easy to build power
stations.  Wind is not constant.
 Cheap electricity.  Visual pollution.
In your exam you may be asked for some advantages and disadvantages of
these different energy sources.
© Studydoctor 2009

3. Power stations use the heat generated from burning fossil fuels and the fission of
nuclear fuels to boil water, making steam. This steam drives a turbine which
produces electricity. The efficiency of a power station can be described in
a Sankey diagram, which shows where the energy created from a fuel
source is going.
25%
30%
Cooling steam
Exhaust gases
Electricity 45%
As you can see, not all the energy generated from a fossil fuel actually goes into
making electricity, lots of the energy is wasted.
In your exam you may be asked to use a Sankey diagram to work out the
efficiency of a primary energy source used to generate electricity.
Recap:
1. Electricity is a secondary energy source that is generated from a primary energy
source.
2. Each energy source has its advantages and disadvantages.
3. A Sankey diagram can be used to show the efficiency of energy sources in generating
electricity.
© Studydoctor 2009