Geothermal energy
- Tectonic activity causes areas where the rocks below ground become heated
- Energy in the thermal store of the rocks can be obtained by:
- Drilling shafts into the Earth's surface to expose the heated rocks
- Injecting water into the shaft which is heated by the rocks
- The water is returned via another shaft as steam or hot water
- The steam can be used to turn a turbine and generate electricity
- The hot water can be used to heat homes and provide a hot water supply to households
Geothermal power station
Cold water is heated by the rocks and returned as hot water or steam, which can be used to generate electricity
Advantages of geothermal energy
- Geothermal energy is renewable
- Geothermal power stations are reliable because the rocks remain hot for thousands of years so they can consistently produce electricity
Disadvantages of geothermal energy
- Geothermal energy depends on tectonic activity, so there are few suitable locations on Earth
- Methane (natural gas) is found in spaces between rocks and can be forced out when water is injected into the rocks (fracking)
- Methane is a greenhouse gas which contributes to global warming (even without combustion)
- Geothermal power stations are expensive to build
- Geothermal power stations are small so they are not suitable for large-scale electricity production
- Geothermal power stations are not very efficient (around 12%)
Examiner Tip
In your IGCSE Co-ordinated Sciences exam, you may be required to discuss the advantages and disadvantages of various energy resources. You may also need to apply your understanding of energy resources to unfamiliar scenarios, for example, by suggesting which type of energy resource would be best for a particular community. Make sure you can justify your choices.
