Geothermal in brief
Geothermal energy uses heat from the Earth's interior. Where hot water or steam is close to the surface, it can generate electricity around the clock.
Power plants cluster in volcanic regions such as Iceland, Indonesia, Kenya, New Zealand and the western United States. Elsewhere, deeper wells and heat pumps supply heat directly.
How it works
- Wells reach hot rock or water. Production wells tap reservoirs at temperatures from about 100 °C to over 300 °C.
- Steam or hot fluid rises. Dry steam goes straight to a turbine; hot water is 'flashed' to steam.
- A turbine generates power. Binary-cycle plants use a second fluid for lower-temperature resources.
- Fluid is reinjected. Cooled water returns underground to sustain the reservoir.
Main technologies
- Flash and dry steam: High-temperature volcanic fields.
- Binary cycle: Lower-temperature resources.
- Direct use and heat pumps: Heating for districts, greenhouses and buildings.
Strengths
- Constant, weather-independent output
- Small land footprint
- Useful for heat as well as power
Challenges
- Suitable geology is limited
- High drilling cost and exploration risk
- Induced seismicity must be managed
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