Renewable and non-renewable energy
Non-renewable energy sources, such as coal, oil and natural gas, take millions of years to form and will run out. Renewable (sustainable) sources are replaced naturally and will not run out: the Sun, wind, water, waves and heat from inside the Earth.
| Source | How it makes energy | Advantage | Limit |
|---|---|---|---|
| Water (hydroelectric) | falling water turns a turbine | reliable, no fuel | needs rivers and dams |
| Solar | cells turn sunlight into electricity; panels heat water | free, no noise | only in daylight, needs space |
| Wind | moving air turns turbine blades | clean | needs steady wind |
| Sea waves | moving water drives generators | clean | equipment is costly |
| Geothermal | hot underground rock heats water to steam | steady day and night | only in certain places |
Power from the wind
The power in the wind rises very quickly with its speed: it depends on speed cubed. Double the wind speed and the power becomes eight times larger. A turbine can capture only a fraction of it, about 35% here.
Try itA wind turbine
Change the wind speed and the blade length. Watch how fast the power grows with wind speed.
Worked exampleWhy tall, windy sites matter
Wind speed at a site rises from 5 m/s to 10 m/s. By what factor does the available wind power change?
- Power ∝ v³.
Answer: The power is 8 times larger.
Key terms
- Renewable energy
- Energy from sources replaced naturally.
- Fossil fuel
- Coal, oil or gas formed from ancient living things.
- Geothermal
- Energy from heat inside the Earth.
- Turbine
- A wheel turned by water, steam or wind to drive a generator.
Summary
- Non-renewable sources run out; renewable sources do not.
- Water, solar, wind, wave and geothermal energy are sustainable.
- Wind power depends on v³, so a faster wind gives much more power.