Geothermal energy

Humans have used geothermal energy for thousands of years. The Maoris of New Zealand use hot rocks to cook food in the ground. Around the world, the thermal waters in hot springs are used to soothe aches and pains. Geothermal energy also has trememdous potential for generating electricity.

Geothermal energy comes from the heat in the earth's core. Magma heats water underneath the earth's crust. This water may then travel up through cracks and reach the earth's surface as hot springs or geysers, but most of it stays deep underground, trapped in cracks and porous rock. This natural collection of hot water is called a geothermal reservoir.

In steam plants such as The Geysers in California, hot water and steam created underground is used to turn turbines and generate electricity. The only significant emission from these plants is water vapour.

Another form of geothermal energy is called "hot rock". This is where water is pumped below the surface to areas of hot rock. The water then turns to steam, and is pumped back to the surface to drive a turbo-generator.

Advantages of using geothermal energy

• It is free once built.

• It is renewable.
• The plants are not large, and do not spoil the landscape.

Disadvantages of using geothermal energy
• Some geothermal sites may 'run out of steam'.
• Small amounts of hazardous minerals - which are difficult to dispose of - may be produced.
• Geothermal energy sites can be difficult to find.