Year 9 Science · Unit 3 · Lesson 12
Challenge Worksheet
Learning Goals
1. Sunlight, wind and flowing water are all called renewable. Using the idea of how fast each one is replenished, explain why, and why coal is not.
2. Which renewable technology in the lesson is the most efficient at making electricity? Give its approximate efficiency and its energy transformation chain.
Find the mistakes: a community energy brochure
(a) “A hydro station turns the chemical energy of water into electricity.”
(b) “Geothermal energy is heat from the Sun that has soaked into rocks deep underground.”
(c) “Solar panels change almost all of the sunlight that hits them into electricity.”
(d) “Because the Sun and wind are renewable, solar and wind farms can make electricity whenever we need it.”
3. Each statement has one error. Say what is wrong, and rewrite the statement correctly.
| Statement | The error | Rewritten correctly |
|---|---|---|
| (a) | ||
| (b) | ||
| (c) | ||
| (d) |
Data: how hard does each power station work?
Three renewable power stations each have a rated power of 100 MW: the most they can produce at any moment. A power station’s capacity factor compares the energy it really produces in a year with the energy it would produce running at full power all year:
capacity factor (%) = energy produced in a year ÷ (rated power × 8,760 hours) × 100. There are 8,760 hours in a year.
| Power station | Energy produced in a year (MWh) | Capacity factor (%) |
|---|---|---|
| Solar farm | 219,000 | |
| Wind farm | 350,400 | |
| Hydro station | 157,680 |
Source: sample values for this worksheet.
4. Calculate the energy each 100 MW station would produce if it ran at full power for a whole year. Then complete Table 1.
Full power all year MWh
5. Use the wind farm’s capacity factor to work out how many hours a day, on average, it would need to run at full power to produce its yearly energy.
Full-power hours each day hours
6. Give a reason why the solar farm’s capacity factor is well below 100%. The hydro station has the lowest capacity factor, yet grid operators value it highly. Suggest why, using what the lesson says about hydro.
Someone claims…
“Australia should switch entirely to solar power by 2030. We’re the sunniest continent on Earth, and more than enough sunlight falls on us to power the whole country several times over. We could close every coal plant tomorrow and just use solar instead.”
7. Evaluate this claim. Say which parts are supported by science and which are not, use your capacity factor results, and finish with a more accurate version of the claim.