Year 9 Science · Unit 3 · Lesson 21
Foundation Worksheet
Learning Goals
Match it: technology and energy source
Write the letter of the matching energy source next to each technology. Each letter is used once.
1. Match each technology to the energy source it uses.
| Technology | Letter | Energy source |
|---|---|---|
| Green hydrogen | A. Kinetic energy of ocean waves, which the wind whips up | |
| Geothermal power | B. Energy released when light atomic nuclei join together | |
| Tidal power | C. Heat stored in hot rock several kilometres underground | |
| Wave power | D. Solar or wind electricity used to split water | |
| Fusion power | E. Seawater moving as the Moon and Sun pull the oceans up and down |
True or false? Fix the false ones
Circle T or F. If a statement is false, rewrite it correctly on the line.
Nuclear fusion already generates electricity in commercial power stations.
Correct it:
Hydrogen is an energy carrier: energy from another source must be used to make it.
Correct it:
Tide times can be predicted years ahead, because tides follow the pull of the Moon and Sun.
Correct it:
Hot-rock geothermal power only works right next to an active volcano.
Correct it:
Grey hydrogen is made from natural gas, and making it releases carbon dioxide.
Correct it:
Fill the gap: making hydrogen
Choose the correct word from the word bank. Each word is used once. Two words will not be used.
Green hydrogen is made by , which uses electricity to split into hydrogen and . The electricity comes from sources such as solar and wind. Grey hydrogen is made from , and making it releases . Because energy from another source must be used to make it, hydrogen is called an energy . Later, a can turn the hydrogen back into electricity, and its only waste product is water.
2. A truck company says its hydrogen trucks are “zero emission”. Explain when this is true and when it is not, using the words green and grey.
Investigation: following 400 kWh of solar electricity
An electrolyser takes in 400 kWh from a solar farm. The gas it makes is squeezed into tanks, and a fuel cell turns it back into electricity when it is needed. Table 1 gives the efficiency of each stage. The energy going into each stage is the energy that came out of the stage before it.
| Stage | Efficiency | Energy out of the stage (kWh) |
|---|---|---|
| 1. Electrolyser makes hydrogen | 70% | |
| 2. Hydrogen is compressed and stored | 90% | |
| 3. Fuel cell makes electricity | 50% |
Source: stage efficiencies from Lesson 21; the 400 kWh is a sample value.
3. Complete Table 1. Use energy out = energy in × efficiency ÷ 100, and show your working for each stage.
Stage 1 kWh
Stage 2 kWh
Stage 3 kWh
4. How much of the 400 kWh was wasted altogether? What is the efficiency of the whole chain?
Wasted kWh
Chain efficiency %
5. A home battery would give back 360 kWh of the same 400 kWh. Which is the better way to store solar energy overnight, and into what form is most of the wasted energy in the hydrogen chain transformed?
Scenario: hydrogen haul trucks at a Pilbara mine
A mine in the Pilbara runs 40 huge diesel haul trucks. The company is thinking of switching them to trucks that run on green hydrogen, made at the mine using electricity from its own solar farm. A battery big enough to run trucks this size would be very heavy.
6. Should the mine switch its trucks to green hydrogen? Explain how the hydrogen would be made and used, and judge the idea using at least two of the four dimensions from Lesson 21: environmental, economic, social and security.