Geothermal Energy
Geothermal energy is seen as a renewable energy resource, in particular as an energy resource which does not originate from the Sun. This energy is stored as heat in the rocks within the earth. We sometimes see this heat in the form of molten lava from areas of volcanic activity.
Strictly speaking geothermal energy is not a renewable energy source, but it can be classified as one because the underground rocks continue to heat up again once the heat has been extracted.
Extracting geothermal heat
The usual method of extracting geothermal heat is to pump water down through the hot rock strata and using the hot water (or steam) that is returned to generate electricity or for district heating systems.
The city of Southampton created the UK's first geothermal power scheme because it set an objective to be a 'self sustaining city' in energy generation.
Hot water, at a temperature of 75°C, is extracted from the Wessex Basin aquifer at a depth of 1,800 metres.
Geothermal energy provides 16 GWh of heat per year.
Ground Source pumps pump heat to or from the ground. The heat source is the earth in the winter, and in the summer the earth becomes the heat sink. A heat pump circulates a mixture of water and antifreeze around a loop of pipe buried in the ground. The heat from the ground is transferred to this fluid which passes through a heat exchanger in the heat pump.
The heat collected in the system is used to heat radiators and floor heating systems.
Rosemanowes Quarry in Cornwall is the site of an experiment to extract extracting geothermal energy using hot dry rock technology. This is not at this time being commercially exploited.
Southampton District Geothermal Heating
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In 2005 the total heat extracted from geothermal sources was 9064.1 MWe.
Source - www.geothermal-energy.org