Year 9 Science · Unit 3 · Lesson 13
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Learning Goals
1. Name the four main non-renewable energy sources. Which one is not a fossil fuel, and how does it release its energy?
Order the steps: from the mine to your home
Number the steps from 1 to 8. Step 1 happens first.
| Order | Step |
|---|---|
| Steam spins the turbine blades at high speed. | |
| Coal is mined from the ground, for example in the Hunter Valley, NSW. | |
| The generator turns the shaft’s kinetic energy into electrical energy. | |
| Coal is burned in a furnace, releasing thermal energy. | |
| Electricity is sent along high-voltage lines to homes. | |
| Water in the boiler is heated and turns into high-pressure steam. | |
| Coal is carried by train to the power station. | |
| The spinning turbine turns the generator’s shaft. |
Real-world context: Liddell Power Station
Liddell, a coal-fired power station in the Hunter Valley, NSW, had four 500 MW generating units, giving 2,000 MW at full power. It opened in the early 1970s, and its last unit closed on 28 April 2023.
Source: “Liddell Power Station”, Wikipedia.
2. At full power, how much electrical energy did Liddell produce in one hour? Give your answer in MWh and in MJ. (1 MW = 1 MJ each second.)
Electricity made in one hour MWh
Electricity made in one hour MJ
3. Assume the station was 36% efficient and its black coal held 25 MJ of chemical energy per kilogram (the lesson’s value). Calculate (a) the chemical energy burned in one hour at full power and (b) the mass of coal burned in one hour, in tonnes.
(a) Energy from the fuel MJ
(b) Mass of fuel t
| Power station | Chemical energy in (MJ) | Electrical energy out (MJ) | Waste energy (MJ) | Efficiency (%) |
|---|---|---|---|---|
| Black coal | 9,000,000 | 3,240,000 | 5,760,000 | 36 |
| Brown coal | 9,000,000 | 2,520,000 | ||
| Gas, combined-cycle | 9,000,000 | 4,950,000 |
Source: sample values within the efficiency ranges given in Lesson 13.
4. Complete Table 1. The black coal row is done for you.
5. (a) How much chemical energy must the brown coal station and the gas station each burn to supply 1,000 MJ of electrical energy? (b) Use your answers to explain why replacing brown coal with gas cuts the fuel burned, as well as the CO₂ released.
(a) Brown coal MJ
(a) Gas MJ
6. Liddell’s 2,000 MW has to be replaced. Explain the challenges of replacing a coal station with solar and wind farms. Compare when each can produce electricity, and suggest how the grid can keep the lights on through a still night.