It is a form of renewable energy derived from heat deep in the earth’s crust, in the earths molten interior.

It is the heat energy that is responsible for tectonic plates, volcanoes and earthquakes. The origin of this heat is from heat generated during the earths formation and heat generated from the decay of radioactive isotopes.

The temperatures within the earth are extremely high, and can reach as high as 7000 degrees.

The heat is brought to the near-surface by thermal conduction and by intrusion into the earth's crust of molten magma originating from great depth.

The hot molten rock heats the surrounding groundwater, which is forced to the surface in the form of hot steam or water.

When the heat comes close or near to the earths surface it can therefore be utilized as a source of energy. This is known as GEOTHERMAL ENERGY! This produces electrictiy.

Many areas have accessible geothermal resources, especially countries along the circum-Pacific "Ring of Fire," spreading centers, continental rift zones and other hot spots. In these regions the heat is conducted very rapidly from the earths interior to the earths surface so that geothermal energy can therefore be produced, and used.

The regions where the energy can be utilised – regions where the most heat is produced.

Geothermal electricity Installed capacity MWe 2001

Kenya 58

Mexico 858Guatemala 33El Salvador 161Nicaragua 70Costa Rica 143

China 29

Russia 23

Philippines1931

Indonesia 787

Turkey 20

New Zealand 437

Thailand 0.3

USA 2002

Ethiopia 9

Italy 762

Iceland 200

Azores 16Japan 549

Australia 0.2

Guadeloupe 4

These were the first type of power generation plants built.

They use steam from the geothermal reservoir ( in the earths surface) from wells and the steam is transferred through generators and turbines to produce electricity.

An example of a dry steam generation operation is at the Geysers in northern California.

These are the plants that are most common type of geothermal power generation plants used today.

They use water at temps more than 186 degrees, and that is pumped under high pressure to the generation equipment at the surface.

When it reaches the surface the pressure is reduced, allowing some of the hot water to convert or ‘flash’ into steam.

This steam is then used to power the turbine /generator units to produce electricity.

The remaining hot water not flashed into steam and the water condensed from the steam is pumped back into the reservoir.

An example of an area that uses the flash steam operation is Calenergy Navy 1 Flash.

Differs from flash and dry steam,.

The water or steam from the geothermal reservoir never comes in contact with the turbine or generator units.

The water from the geothermal reservoir is used to heat another fluid which is vaporized and used to turn the

turbine/generator.The geothermal water and the working fluid are confined in separate circulating systems and never come in contact with each other.

These plants can operate at a lower temp which is an advantage., and produce no air emissions.

An example of an area using a Binary Cycle power generation system is the Mammoth Pacific binary geothermal power plants at the Casa Diablo geothermal field.

The operating costs are low.

Earth energy can provide heating in winter, cooling in summer, and year-round hot water for home use. A single system performs all necessary functions and requires only a flick of a switch to reverse the unit for a seasonal change .

The systems do not produce the odour that is found in natural gas, oil or propane furnaces. That makes earth energy systems perfect for highly-insulated buildings or for people who are allergic or sensitive to noxious gases and poor air quality.

The land area required for geothermal power plants is smaller per megawatt than for almost every other type of power plant. Geothermal installations don't require damming of rivers or harvesting of forests -- and there are no mine shafts, tunnels, open pits, waste heaps or oil spills.

Geothermal projects can offer all of the above benefits to help developing countries grow without pollution. And installations in remote locations can raise the standard of living and quality of life by bringing electricity to people far from "electrified" population centers.

the processes used to extract energy move at a much higher rate than the processes that return energy into the geothermal environment.

There are not many places where you can build a geothermal power station, this is due to the fact that the plants cannot be built in areas where the temp in the earth is low. Also a large depth is needed to drill holes into the ground.

Hazardous gases and minerals may come up from underground, and can be difficult to safely dispose of.

Geothermal energy doesn’t create much employment. This could affect some people and therefore the standard of living for these could reduce , and income, and problems would be created with finding employment,

The impact on the environment is considerably lower than using fossil fuels or a nuclear plant.

The hydrogen sulphide released could convert to sulphur dioxide that contributes to acid rain but it is highly unlikely.

Instead it converts into sulphur which falls with precipitation and collects harmless salts.

Geothermal power plants, like wind and solar power plants, do not have to burn fuels to manufacture steam to turn the turbines. Therefore this helps to conserve nonrenewable fossil fuels, and by decreasing the use of these fuels, we reduce emissions that harm our atmosphere. There is no smoky air around geothermal power plants -- in fact some are built in the middle of farm crops and forests, and share land with cattle and local wildlife.

Most of it is generated by hydroelectric stations.

Geothermal is used in Wairahei. The power station here has been running since 1958. and has generated 192mw.

The geothermal energy capacity in New Zealand is over 2000 megawatts and supplies for industrial and domestic demand.

There is scope in New Zealand for more geothermal power stations as demand increases.

Sits on mid Atlantic ridge.

Significant producer of geothermal energy for some time.

Has 250 low temp geothermal fields and 23 high temps.

86% of its domestic usage is from geothermal sources.

It currently produces 40ej in this way and has a capacity of 1000ej.

Heating bills are lower for the residents , and are lower than those in the UK despite the colder climate and higher cost of living.

The smell from the hydrogen sulphide is a minor inconvenience to tolerate for the sake of a cheap energy supply.

There is some potential in the uk, which is distant from plate boundaries.

Some low flow aquifers are found in the Southampton and Cleethorpes areas, while better prospects exist in the igneous rocks of south west England,

These are hot dry rocks which could heat water pumped down to them.

Improvements in technology are required before the uk would be able to carry out geothermal energy production, and rival Iceland.