1. OCR 21st Century Science Unit P3b Revision
Generating energy

2. Generators (dynamos)
21/04/2017
Electricity is convenient because it can be transmitted over long distances and can be used in many ways. But how is it generated? We need to use a “generator”:
Basically, a generator works by spinning a magnet near a coil of wire. That’s useful, but how do we get this magnet to keep spinning?

3. Using primary energy sources in power stations
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1) A fuel is burned in the boiler
2) Water turns to steam and the steam drives a turbine
3) The turbine turns a generator – if you want more electricity you have to burn more fossil fuels
4) The output of the generator is connected to a transformer
5) The steam is cooled down in a cooling tower and reused

4. Efficiency of Power Stations
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Heat
Heat
Heat
15J
Boiler
Turbine
Generator
100J
50J 5J
85J
35J
30J
Heat
Kinetic
Electrical

5. Nuclear power stations
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These work in a similar way to normal power stations:
The main difference is that the nuclear fuel is NOT burnt. This means that they produce less pollution but they do produce radioactive waste instead.

6. Radioactive Waste - Ionisation
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Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by “knocking off” electrons:
Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.

7. Radioactive Contamination
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Simply being “irradiated” by a radioactive material doesn’t have to be dangerous – for example, we have background radiation around us all the time. However, being “contaminated” is far more dangerous. Consider the example of Alexander Litvinenko who was poisoned with polonium-210:
Timeline of Events
Video of risks from polonium 210

8. Other ways of generating electricity
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Can we drive the turbine directly without burning any fossil fuels? Here are some examnples...

9. 21/04/2017
Wind Power

10. Wave Power
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11. Hydroelectric Power
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12. The National Grid
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Electricity reaches our homes from power stations through the National Grid:
Power station
Step up transformer
Step down transformer
Homes
If electricity companies transmitted electricity at 230 volts through overhead power lines there would be too much energy loss by the time electricity reaches our homes. To ensure this doesn’t happen, electricity companies transmit electricity at higher voltages instead.

13. Decommiss-ioning costs
Which power station?
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Type of power station
Commiss-ioning costs
Running costs
(p per KWh)
Decommiss-ioning costs
Life span (years)
Coal
£650 million 4
£100 million
40-80
Oil
£700 million 12
Gas
£800 million 6
30-40
Nuclear
£2 billion 3
£500 million
Which power station is the most expensive to build and why?
Give one advantage of coal power stations
Why is nuclear fuel cheaper than oil?
Overall, which power station is the most expensive?

14. Matching supply and demand…
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Hydroelectric power station might “kick in” here
“Baseline” power stations

15. Solar Panels and Thermal Towers
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What are the advantages and disadvantages of solar power?

16. Using Solar Energy in remote places
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Using Solar Energy in remote places

17. Words – steam, Iceland, volcanic, turbines, hot rocks
Geothermal Energy
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Geothermal energy can be used in _______ areas such as ______. In a geothermal source cold water is pumped down towards ____ _____. The water turns to steam and the steam can be used to turn ______. In some areas the _____ rising at the surface can be captured and used directly.
Words – steam, Iceland, volcanic, turbines, hot rocks

18. Non-renewable energy sources
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Advantages
Disadvantages
Cheap fuel costs
Costs a lot of money to decommission a nuclear plant
Good for “basic demand”
Coal, oil, gas and nuclear
Reliable
Fuel will run out
Short start-up time for gas and oil
Pollution – CO2 leads to global warming and SO2 leads to acid rain
Nuclear produces little pollution

19. Renewable energy sources summary
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Advantages
Disadvantages
Zero fuel costs
Unreliable (except for hydroelectric)
Don’t produce pollution
Wind, tidal, hydroelectric and solar
Expensive to build
Hydroelectric is good for a “sudden” demand
Tidal barrages destroy the habitats of wading birds and hydroelectric schemes involve flooding farmland
Solar is good for remote locations (e.g. satellites)

20. Electricity Supply in the UK
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Notice that, due to all these advantages and disadvantages, we use a variety of sources of energy in the UK: