Year 9 Science · Unit 3 · Lesson 21
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Learning Goals
1. Lesson 21 judged future energy technologies on four dimensions. Name all four.
2. Explain why tidal power is easier to plan for than wind power.
Because… chain: from Pilbara wind to a steelworks in Japan
Each box causes the next one. Read across each row, then down to the next row.
3. Fill in the three empty boxes.
Real-world context: hot rocks under the Cooper Basin
About 4 km below the Cooper Basin in outback South Australia lies hot granite (Lesson 21). A hot-rock power station would pump water down one well, let the rock heat it, and bring it back up another well. Unlike a solar farm, it could run day and night. No large hot-rock power station has been built in Australia yet: the wells are deep and costly to drill, and the basin is a long way from the cities that would use the electricity.
4. Describe how a hot-rock power station would make electricity here. Start with the cold water pumped down, and finish at the generator.
5. Give one advantage the station would have over a solar farm, and one reason it has not been built.
Investigation: hydrogen or batteries for a long-haul truck?
A transport company compares two ways to store 396 kWh for a truck: as hydrogen fuel, or in lithium-ion battery cells. This simplified comparison excludes the mass of tanks and battery-pack hardware, and the energy losses when powering the truck.
| Quantity | Value | Unit |
|---|---|---|
| Electricity assumed to make 1 kg of hydrogen | 50 | kWh |
| Energy in 1 kg of hydrogen (lower heating value) | 33 | kWh |
| Energy stored in 1 kg of lithium-ion battery cells | 0.25 | kWh |
Source: rounded electrolysis assumption of 50 kWh/kg (US Department of Energy); hydrogen lower heating value (NREL); 0.25 kWh/kg for battery cells (Molicel M35A datasheet). Compression and storage energy are excluded. The 396 kWh is a sample stored-energy value.
6. Find (a) the mass of hydrogen that stores 396 kWh, (b) the electricity needed to make it, (c) the efficiency of making the hydrogen, and (d) the mass of lithium-ion battery cells that stores 396 kWh.
(a) Hydrogen kg
(b) Electricity kWh
(c) Efficiency %
(d) Battery cells kg
7. Use your answers to explain why hydrogen may suit long-distance freight and shipping, while batteries suit cars and homes.
Scenario: a politician’s plan
A politician says: “Australia should invest only in solar and wind, and ignore every other energy technology.”
8. Evaluate the politician’s plan. Use all four dimensions from Lesson 21 to build an argument for it and against it, and finish with your own conclusion.