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Generating Electricity Pg 150 – 159
Syllabus 4.16 and 4.17
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Starter: is nuclear energy green?
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Generating Electricity
Today’s learning objective is to… * Describe the energy transfers involved in generating electricity using a variety of energy sources * Know their advantages and disadvantages
Think How many energy sources do you know which
are used to generate electricity?
October 18, 2015
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Key Words
* Renewable 재생 가능한
* Non-‐Renewable 재생 불 가능한
* Solar 태양의
* Geothermal 지열의
* Turbine 터빈
* Generator 발전기
* Wind 바람
* Water 물
* Fossil fuels 화석 연료
* Nuclear power 원자력 © www.cgrahamphysics.com
Edexcel Specification
Section 4: Energy resources and energy transfer d) Energy resources and electricity generation understand the energy transfers involved in generating electricity using: • wind • water • geothermal resources • solar heating systems • solar cells • fossil fuels • nuclear power Describe the advantages and disadvantages of methods of large-‐scale electricity production from various renewable and non-‐renewable resources.
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The big picture
How is electricity produced?
Have you ever wondered? © www.cgrahamphysics.com
How is electricity generated?
Coal burnt in furnace, produces heat
Water boils to form steam, which rises
Steam turns turbine blades
Turbine drives generator, which creates electricity
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What are energy resources? An energy resource is anything that can be used to generate power for human use. There are two categories of energy resource: l non-renewable energy
resources will eventually run out – once used they cannot be used again. Examples are fossil fuels (coal, oil, natural gas) and nuclear fuels (uranium, plutonium).
l renewable energy resources can be replaced or regenerated and will never run out. Examples are wind, hydroelectricity and solar power. © www.cgrahamphysics.com
Driving a turbine
Many energy resources are used to generate electricity by driving a turbine connected to a generator. Both renewable and non-renewable energy sources can drive a turbine. l Some drive a turbine directly – e.g. wind and water power. l Others drive a turbine indirectly by being used to heat
water and create high-pressure steam – e.g. coal, nuclear and geothermal power. © www.cgrahamphysics.com
Renewable or non-‐renewable?
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Wind power
Wind is used to rotate a turbine (the blades) which turns an electrical generator.
A wind farm
Energy changes: kinetic to electrical
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ADVANTAGES * Renewable energy source * No greenhouse gases * No acid rain * No radioactive waste * Inexpensive to build * Short start up time
DISADVANTAGES * Unreliable – needs wind! * Best used in places where they will often be regarded as unsightly * Many turbines are needed to produce the same energy of a small thermal power station * Noise * Danger to wildlife
Wind farm off the coast in Shanghai
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Hydroelectric power
Falling water is used to drive a turbine which rotates an electrical generator. Energy changes: gravitational potential to kinetic to electrical © www.cgrahamphysics.com
Hydroelectric power station
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ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste * Short start up time
DISADVANTAGES * Very limited locations * Wildlife affected * Expensive to build
The Hoover Dam near Las Vegas
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Wave power
Waves can be used to drive an electrical generator. Energy changes: kinetic to electrical
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ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste * No land needed * Short start up time
DISADVANTAGES * Unreliable * Can only be used in areas with suitable waves * Prone to storm damage * Many needed to produce the same energy of a small thermal power station * Danger to shipping
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Tidal power
Moving water caused by the tides is used to drive a turbine directly which rotates an electrical generator. Energy changes: gravitational potential to kinetic to electrical
Tidal power station at La Rance, Brittany
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Tidal power station © www.cgrahamphysics.com
ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste * Short start up time
DISADVANTAGES * Very limited locations * Wildlife affected * Expensive to build
Proposed Severn Estuary Tidal Power Scheme
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Geothermal energy
In some volcanic areas hot water and steam rise to the surface. The steam can be tapped and used to drive turbines. This is known as geothermal energy. Energy changes: thermal (heat) to kinetic to electrical
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ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste * Short start up time
DISADVANTAGES * Very limited locations * Expensive to build
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Solar heating
Heat energy from the Sun is focussed onto pipes containing water. The water boils producing steam. The steam is then used to drive turbines which turn electrical generators. Energy changes: thermal to kinetic to electrical
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ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste
DISADVANTAGES * Sunshine needed and so best in desert regions * Can only be used during the day * A large amount of land is needed to produce a significant amount of energy
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Solar cells
Electricity produced directly from the Sun’s radiation. Energy changes: light to electrical
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ADVANTAGES * Renewable * No greenhouse gases * No acid rain * No radioactive waste * Instant start up time
DISADVANTAGES * Unreliable in the UK! – sunshine is needed for solar cells * Can only be used during the day * Only 10% of solar energy is converted into electricity by solar cells * Many cells needed to produce a significant amount of energy
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Fossil fuels
Fossil fuels include coal, oil and natural gas. They have been formed in the ground from dead vegetation and tiny creatures by a process that has taken millions of years. When burnt the heat energy produced is used to produce steam. The steam is then used to drive turbines which turn electrical generators.
Energy changes: thermal to kinetic to electrical
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Coal-‐fired power station
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Problems with fossil fuels
Burning coal, gas and oil produces carbon dioxide. This is a greenhouse gas which causes global warming.
Fossil fuel burning can also produce sulfur dioxide gas. This can dissolve in water and produce acid rain which causes damage to forests and buildings. Modern power stations remove most sulfur dioxide producing compounds before burning.
Fossil fuels are not renewable. They are running out. Estimates vary between 50 to 200 years to when we will need to find alternative sources of energy.
An effect of acid rain
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ADVANTAGES * Concentrated energy source * Reliable energy source * Can be built anywhere * No radioactive waste
DISADVANTAGES * Non-‐renewable * Produces greenhouse gases and contributes to global warming * Produces acid rain
A good and a bad day in Beijing © www.cgrahamphysics.com
Nuclear power
Nuclear power stations use a certain type of uranium to produce heat energy. This heat energy is used to produce steam. The steam is then used to drive turbines which turn electrical generators. Energy changes: nuclear to thermal to kinetic to electrical
uranium fuel rods
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A nuclear reactor
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Problems with nuclear power stations
Nuclear fuel (uranium) does not produce greenhouse gases and it generates 10000 times more energy per kilogram than fossil fuels.
However:
Nuclear waste is radioactive and may have to be stored safely for thousands of years.
Although safe in normal operation, accidents can release radioactive material over a large area. The area around Chernobyl in Ukraine has been closed off since 1986.
The destroyed Chernobyl nuclear reactor
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ADVANTAGES * Concentrated energy source * Reliable energy source * Can be built anywhere * No greenhouse gases * No acid rain
DISADVANTAGES * Non-‐renewable * Radioactive waste * Expensive to build * Technology is related to that needed to make atomic bombs © www.cgrahamphysics.com
What is biomass?
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Biomass and carbon neutral energy Biomass produces carbon dioxide when burnt. This is a greenhouse gas so why is biomass considered ‘green’?
However, the environmental impact of using fertilizers to grow biomass and the energy used in its transportation must also be considered.
The amount of carbon dioxide released is the same as the amount that the biomass took in when it was growing. There is no net increase in carbon dioxide, which means biomass is carbon neutral.
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Biofuels: complete the sentences
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Electricity generation pie-‐chart
Most of our electricity is generated by burning fossil fuels (74% according to the pie chart opposite)
Nearly 20% is nuclear
Less than 5% is currently generated using renewable sources.
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Task: 15 minute
End
1. (a) Explain the difference between a renewable and a non-‐renewable energy source. (b) Give three examples of each.
2. Briefly describe how the following energy sources can be used to produce electricity: (a) wind; (b) water; (c) geothermal; (d) solar; (e) fossil fuels and (f) nuclear.
3. For each source listed in question 2 give two advantages and two disadvantages of their use in generating electricity.
4. Answer the questions on page 159. 5. Verify that you can do all of the items listed in the end of
chapter checklist on page 159.
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Plenary: Choose appropriate words to fill in the gaps below:
Most of our electricity is produced by thermal __________ stations. These use the _______ produced by burning _____ or the fission of __________ to generate electricity.
The heat produced is used to change ________ into high pressure steam. This steam is used to turn a _________ which in turn _________ an electrical generator.
Over _______ of our electricity is generated by using thermal power stations.
fuels uranium turbine
rotates water heat
power
WORD SELECTION:
90%
fuels uranium
turbine rotates
water
heat power
90%
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Multiple-‐choice quiz
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