Geothermal Energy (Cambridge International IGCSE Physics)

Spec point — 1.8.4 · Describe how useful energy may be obtained, or electrical power generated, from:

• geothermal resources including references to a boiler, turbine and generator where they are used Describe advantages and disadvantages in terms of renewability, availability, reliability, scale and environmental impact

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 turns a turbine, powering a generator that produces electricity.
  • The hot water can be used to heat homes and provide a hot water supply to households

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— it comes from the long-term continuous decay of radioisotopes in the Earth's core that will outlive the Earth
• Geothermal power stations do not produce greenhouse gases (such as carbon dioxide) during operation and do not contribute to global warming
• Generating electricity from geothermal energy does not release acidic gases (such as sulfur dioxide) into the atmosphere and does not contribute to acid rain
• 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
• Drilling can release gases trapped underground, including methane, which is a powerful greenhouse gas
• The initial cost to build the geothermal power station and drill deep into the Earth is extremely expensive
• Most geothermal power stations are smaller than fossil-fuel or nuclear stations

Exam Hint Note that geothermal energy is one of three energy resources whose energy does not come from the Sun. The other two energy resources are nuclear energy (nuclear fission) and tidal energy.