Lesson overview
Energy resources: How should a town get its electricity?
Look inside a gas-fired power station and follow the energy from the flame to the cables. Run a model town for a week on gas alone, then decide where a wind farm, solar cells, a tidal barrage and a dam should go, and watch hour by hour whether they keep up. Find out why the town still needs a backup, where the wasted energy goes, and calculate the efficiency of the station.
Suggested sequence
- Lesson 1 · Where electricity comes from. Electricity from fossil fuels, biofuels, nuclear fuel, geothermal resources, water, sunlight and wind, with the boiler, turbine and generator; Supplement: the Sun as the main source of energy, and nuclear fusion. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- Lesson 2 · Choosing energy resources. Advantages and disadvantages of energy resources: renewability, availability, reliability, scale and environmental impact; efficiency; Supplement: calculating efficiency from energy or power. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- End of module · final check. 5 new questions, 20–30 min, without hints or notes; pupils check their answers once they have answered them all.
- One to two weeks later · return questions. 4 questions, 15 min, lesson closed.
Learning goals
Part 1: Where electricity comes from
- Describe how useful energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy including references to a boiler, turbine and generator where they are used (1.7.3.1)
- Supplement: Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal; know that energy is released by nuclear fusion in the Sun; know that research is being carried out to investigate how energy released by nuclear fusion can be used to produce electrical energy on a large scale (1.7.3.4, 1.7.3.5, 1.7.3.6)
Part 2: Choosing energy resources
- Describe advantages and disadvantages of each method in terms of renewability, availability, reliability, scale and environmental impact (1.7.3.2)
- Understand, qualitatively, the concept of efficiency of energy transfer (1.7.3.3)
- Supplement: Define efficiency as: (a) (%) efficiency = (useful energy output) / (total energy input) (× 100%) (b) (%) efficiency = (useful power output) / (total power input) (× 100%); recall and use these equations (1.7.3.7)
Misconceptions to listen for
- “The flame turns the turbine directly.” — The flame heats water in the boiler. It is the steam from the boiling water that pushes the turbine blades round.
- “The generator stores the electricity until it is needed.” — A generator generates electricity only while it is turning. The power station stores no electricity.
- “The cooling tower makes the electricity, because the cloud rises from it.” — The cloud is water vapour carrying wasted energy away. The current comes from the generator, part C.
- “Row A.” — The moving water pushes the turbine round directly. Nothing is burnt, so no water is boiled into steam: there is no boiler.
- “Row C.” — A generator has to be turned. At a barrage the moving water pushes a turbine round, and the turbine turns the generator.
- “Row D.” — A turbine only spins: it makes no current. The generator makes the current, and no water is boiled at a barrage.
- “Biofuels generate electricity in a different way from fossil fuels.” — Both are fuels: they are burnt to boil water, and the steam turns a turbine and generator. The difference is where the fuel comes from.
- “Solar cells use the Sun’s heat to make steam.” — Solar cells turn light straight into electricity. There is no steam, turbine or generator.
- “Uranium is burnt in a boiler, like coal.” — Nothing burns in a nuclear power station. Energy released from the nuclei of the uranium atoms heats the water.
- “The charger works like a solar panel; the shower uses solar cells.” — Swapped. The charger must give a current, so it uses solar cells. The shower must give hot water, which is what a solar panel does.
Scope
Useful energy and electrical power obtained from chemical energy in fossil fuels and biofuels, water (waves, tides and water behind hydroelectric dams), geothermal resources, nuclear fuel, light from the Sun with solar cells, infrared and other radiation from the Sun heating water in solar panels, and wind, including the boiler, turbine and generator where they are used (1.7.3.1); the advantages and disadvantages of each method in terms of renewability, availability, reliability, scale and environmental impact (1.7.3.2); efficiency in qualitative terms (1.7.3.3). Supplement: the Sun’s radiation as the main source of energy for all our energy resources except geothermal, nuclear and tidal (1.7.3.4); energy released by nuclear fusion in the Sun (1.7.3.5); research into nuclear fusion for large-scale electricity (1.7.3.6); (%) efficiency = useful energy output ÷ total energy input (× 100 %) and the same with power (1.7.3.7). How a generator works (4.5), nuclear fission and fusion in detail (5.1) and the National Grid are left to later modules.