OCR 21OCR 21stst Century Century Science Science

Unit P3b Revision Unit P3b Revision Generating energy

19/04/23

Generators (dynamos)Generators (dynamos)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?

19/04/23Using primary energy sources in power Using primary energy sources in power stationsstations

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 fuels4) The output of the generator is connected to a transformer

5) The steam is cooled down in a cooling tower and reused

19/04/23

Efficiency of Power StationsEfficiency of Power Stations

100J Boiler 85J Turbine35J

Generator30J

15J 50J 5J

Heat

Heat Kinetic

Heat Heat

Electrical

19/04/23

Nuclear power stationsNuclear power stationsThese 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.

19/04/23Radioactive Waste - Radioactive Waste - IonisationIonisation

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.

19/04/23

Radioactive ContaminationRadioactive Contamination

Timeline of Events

Video of risks from polonium 210

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:

19/04/23Other ways of generating Other ways of generating electricityelectricity

Can we drive the turbine directly without burning any fossil fuels?

Here are some examnples...

19/04/23

Wind PowerWind Power

19/04/23

Wave PowerWave Power

19/04/23

Hydroelectric PowerHydroelectric Power

19/04/23

The National GridThe National GridElectricity reaches our homes from power stations through the National Grid:

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.

Power stationStep up

transformerStep down

transformerHomes

19/04/23

Which power station?Which power station?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 £100 million 40-80

Gas £800 million 6 £100 million 30-40

Nuclear £2 billion 3 £500 million 30-40

1) Which power station is the most expensive to build and why?

2) Give one advantage of coal power stations

3) Why is nuclear fuel cheaper than oil?

4) Overall, which power station is the most expensive?

19/04/23Matching supply and Matching supply and demand…demand…

“Baseline” power stations

Hydroelectric power station might “kick in” here

19/04/23Solar Panels and Thermal Solar Panels and Thermal TowersTowers

What are the advantages and

disadvantages of solar power?

19/04/23Using Solar Energy in remote Using Solar Energy in remote placesplaces

19/04/23

Geothermal EnergyGeothermal Energy

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

19/04/23

Non-renewable energy sourcesNon-renewable energy sources

Coal, oil, gas and nuclear

Advantages Disadvantages

Cheap fuel costs

Short start-up time for gas and oil

Good for “basic demand”

Fuel will run out

Costs a lot of money to

decommission a nuclear plant

Pollution – CO2 leads to global warming and SO2 leads to acid rain

Reliable

Nuclear produces little pollution

19/04/23Renewable energy sources Renewable energy sources summarysummary

Wind, tidal, hydroelectric and solar

Advantages Disadvantages

Zero fuel costs

Hydroelectric is good for a

“sudden” demand

Don’t produce pollution

Tidal barrages destroy the habitats of wading birds and hydroelectric

schemes involve flooding farmland

Unreliable (except for

hydroelectric)

Expensive to build

Solar is good for remote locations (e.g. satellites)

19/04/23

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